Global Mineral Resource Assessment

Scientific Investigations Report 2010–5090–D

U.S. Department of the Interior

U.S. Geological Survey

Prepared in cooperation with the Coordinating Committee for Geoscience Programmes in East and Southeast Asia

Porphyry Copper Assessment of Southeast Asia 

and Melanesia

Porphyry Copper Assessment of Southeast 

Asia and Melanesia

By Jane M. Hammarstrom, Arthur A. Bookstrom, Connie L. Dicken, Benjamin J. 

Drenth, Steve Ludington, Gilpin R. Robinson, Jr., Bambang Tjahjono Setiabudi, 

Wudhikarn Sukserm, Dwi Nugroho Sunuhadi, Alexander Yan Sze Wah, and 

Michael L. Zientek, with contributions from Dennis P. Cox, Pairatt Jarnyaharn, 

Gwaibo Kopi, Nguyen Thi Minh Ngoc, Pichai Otarawanna, Chen Shick Pei, Ung 

Phany, Nguyen Vay Quy, Takehiro Sakimoto, Dulcie Saroa, Norberta Soares da 

Costa, Sieng Sotham, I.M. Sim, Nguyen Nhu Trung, Somob Wongsomasak, Boonsong Yokarti, and Khin Zaw

Scientific Investigations Report 2010–5090–D

U.S. Department of the Interior

U.S. Geological Survey 

Global Mineral Resource Assessment 

Michael L. Zientek, Jane M. Hammarstrom, and Kathleen M. Johnson, editors

Prepared in cooperation with the Coordinating Committee for Geoscience 

Programmes in East and Southeast Asia
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2013

This report and any updates to it are available online at:

http://pubs.usgs.gov/sir/2010/5090/d/

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only and does not imply endorsement by the U.S. Government.

Although this report is in the public domain, it may contain copyrighted materials that 

are noted in the text. Permission to reproduce those items must be secured from 

the individual copyright owners.

Suggested citation:

Hammarstrom, J.M., Bookstrom, A.A., Dicken, C.L., Drenth, B.J., Ludington, S., Robinson, G.R., Jr., 

Setiabudi, B.T., Sukserm, W., Sunuhadi, D.N., Wah, A.Y.S., and Zientek, M.L., with contributions from Cox, 

D.P., Jarnyaharn, P., Kopi, G., Ngoc, N.T.M., Otarawanna, P., Pei, C.S., Phany, U., Van Quy, N., Sakimoto, T., 

Saroa, D., Soares de Costa, N., Sotham, S., Sim, I.M., Trung, N.N., Wongsomasak, S., Yokarti, B., and Zaw, 

K., 2013, Porphyry copper assessment of Southeast Asia and Melanesia: U.S. Geological Survey Scientific 

Investigations Report 2010–5090–D, 332 p. and GIS data. 
iii

Contents

Abstract...........................................................................................................................................................1

Introduction ....................................................................................................................................................2

Terminology............................................................................................................................................3

Porphyry Copper Assessment of Southeast Asia and Melanesia.........................................................6

Porphyry Copper Models.....................................................................................................................6

Fundamental Basis for Porphyry Copper Assessment...................................................................7

Tectonic Setting ....................................................................................................................................7

Indochina Peninsula Area..........................................................................................................7

Carboniferous and Permo-Triassic Arcs.........................................................................7

Sukhothai Island-Arc System ..................................................................................7

Loei Magmatic Belt ...................................................................................................8

Trong Son Magmatic Belt.......................................................................................10

Jurassic and Cretaceous Arcs.......................................................................................10

Tertiary Arcs ......................................................................................................................10

Wuntho-Popa Arc....................................................................................................10

Western Indonesian Islands Area ..........................................................................................10

Tertiary Arcs ......................................................................................................................10

Sunda-Banda Arc ....................................................................................................10

Ambon Arc ................................................................................................................10

Halmahera Arc .........................................................................................................10

Sulawesi-Sangihe Arc ............................................................................................11

Central Kalimantan Magmatic Belt.......................................................................14

New Guinea Island, Indonesia and Papua New Guinea.....................................................14

Paleogene Arcs.................................................................................................................14

Inner Melanesian Arc .............................................................................................14

Miocene Arcs....................................................................................................................20

Maramuni Arc of Papua New Guinea ..................................................................20

Miocene Rocks of Western New Guinea Island, Indonesia.............................20

Late Miocene to Pliocene Magmatism .........................................................................20

Medial New Guinea Magmatic Belt .....................................................................20

Papua New Guinea and Melanesia........................................................................................22

Late Miocene to Pliocene Magmatism .........................................................................22

Outer Melanesian Arc.............................................................................................22

Assessment Data................................................................................................................................24

Geologic Maps ...........................................................................................................................24

Mineral Occurrence Data ........................................................................................................24

Other Data...................................................................................................................................24

Exploration History..............................................................................................................................26

Indonesia (Based on contributions of Bambang Tjahjono Setiabudi and 

Dwi Nugroho Sunuhadi)..............................................................................................26

Permissive Tracts................................................................................................................................26

Tract Delineation........................................................................................................................26

Permissive Tracts for Porphyry Copper Deposits in Southeast Asia and Melanesia ....27
iv

Indochina Peninsula Area........................................................................................................29

Indonesian Islands Areas.........................................................................................................29

New Guinea Island and Papua New Guinea Islands...........................................................35

Melanesia....................................................................................................................................36

Other Areas..........................................................................................................................................37

Timor Leste (East Timor) (Based on contributions of Norberta Soares da Costa)..........37

Grade and Tonnage Models..............................................................................................................37

The Assessment Process..................................................................................................................37

Estimates of Numbers of Undiscovered Deposits................................................................37

Summary of Probabilistic Assessment Results ......................................................................................39

Discussion............................................................................................................................................40

Considerations for Users of this Assessment.........................................................................................41

Acknowledgments.......................................................................................................................................50

References Cited..........................................................................................................................................50

Appendix A. Porphyry Copper Assessment for Tract 142pCu7021, Sukhothai—China, 

Myanmar, Thailand, Lao People’s Democratic Republic, Cambodia, and Vietnam.............58

Appendix B. Porphyry Copper Assessment for Tract 142pCu7022, Malaysia—Malaysia, 

Thailand, Singapore, and Indonesia ...........................................................................................69

Appendix C. Porphyry Copper Assessment for Tract 142pCu7023, Mekong Delta—Vietnam, 

Cambodia, and Lao People’s Democratic Republic..................................................................77

Appendix D. Porphyry Copper Assessment for Tract 142pCu7024, Wuntho-Popa—Myanmar 

and India ..........................................................................................................................................85

Appendix E. Porphyry Copper Assessment for Tract 142pCu7020, Sumatra Island—

Indonesia .........................................................................................................................................92

Appendix F. Porphyry Copper Assessment for Tract 142pCu7025, Sunda-Banda Arc—

Indonesia .......................................................................................................................................107

Appendix G. Porphyry Copper Assessment for Tract 142pCu7026, West Sulawesi—

Indonesia .......................................................................................................................................126

Appendix H. Porphyry Copper Assessment for Tract 142pCu7027, North Sulawesi-Sangihe—

Indonesia .......................................................................................................................................137

Appendix I. Porphyry Copper Assessment for Tract 142pCu7019, Central Kalimantan—

Indonesia and Sabah and Sarawak, Malaysia........................................................................149

Appendix J. Porphyry Copper Assessment for Tract 142pCu7201, Ambon Arc—Central 

Molucca Islands, Indonesia .......................................................................................................164

Appendix K. Porphyry Copper Assessment for Tract 142pCu7202, Halmahera Arc—North 

Molucca Islands, Indonesia .......................................................................................................175

Appendix L. Porphyry Copper Assessment for Tract 142pCu7205, Moon-Utawa –Ular Merah 

Area—Indonesia..........................................................................................................................186

Appendix M. Porphyry Copper Assessment for Tract 142pCu7203, Western Medial New 

Guinea Magmatic Belt—Indonesia ..........................................................................................197

Appendix N. Porphyry Copper Assessment for Tract 142pCu7204, Rotanburg-Taritatua 

Area—Indonesia..........................................................................................................................212

Appendix O. Porphyry Copper Assessment for Tract 009pCu7203, Eastern Medial New 

Guinea Magmatic Belt—Papua New Guinea and Indonesia...............................................219

Appendix P. Porphyry Copper Assessment for Tract 009pCu7205, Maramuni Arc— 

Papua New Guinea ......................................................................................................................239
v

Appendix Q. Porphyry Copper Assessment for Tract 009pCu7206, Miocene Alkaline 

Rocks—Southeastern Papua New Guinea .............................................................................251

Appendix R. Porphyry Copper Assessment for Tract 142pCu7208, Inner Melanesian Arc I—

Indonesia .......................................................................................................................................261

Appendix S. Porphyry Copper Assessment for tract 009pCu7208, Inner Melanesian Arc II—

Northern New Guinea Island, Papua New Guinea.................................................................268

 Appendix T. Porphyry Copper Assessment for Tract 009pCu7209, Inner Melanesian Arc III— 

New Britain, Papua New Guinea...............................................................................................275

Appendix U. Porphyry Copper Assessment for Tract 009pCu7207, Outer Melanesian Arc I—

Papua New Guinea ......................................................................................................................287

Appendix V. Porphyry Copper Assessment for Tract 009pCu7210, Outer Melanesian Arc II—

Solomon Islands, Vanuatu, and Fiji............................................................................................303

Appendix W. Description of GIS files .....................................................................................................330

Appendix X. Assessment Team ...............................................................................................................331

Figures

1. Map of permissive tracts for porphyry copper deposits in Southeast Asia 

and Melanesia .........................................................................................................................4

2. Generalized model of western Pacific porphyry copper-gold deposits................................8

3. Map of the principal magmatic arcs of Southeast Asia and Melanesia.............................12

4. Chart of the age distribution of dated porphyry copper deposits 

and prospects in Southeast Asia........................................................................................15

5. Map showing the regional tectonic setting of the Indochina Peninsula 

and western Indonesia.........................................................................................................16

6. Map showing the regional tectonic setting of eastern Indonesia 

and Papua New Guinea .......................................................................................................19

7. Map of tectonic belts of New Guinea Island, Indonesia and Papua New Guinea ............21

8. Map of the Inner and Outer Melanesian arcs, Papua New Guinea.....................................23

9. Diagram showing the tectonic evolution of Melanesia .........................................................25

10. Map of permissive tracts for porphyry copper deposits, Indochina Peninsula Area, 

 Southeast Asia ..............................................................................................................................30

11. Map of permissive tracts for porphyry copper deposits, Indonesian Islands Area, 

 Southeast Asia ..............................................................................................................................31

12. Map of permissive tracts for porphyry copper deposits, New Guinea Island, Indonesia 

and Papua New Guinea, and other Papua New Guinea Islands, Southeast Asia .....32

13. Map of permissive tracts for porphyry copper deposits, Melanesia...................................33

14. Plot of global tonnage and grade models for porphyry copper deposits............................40

15. Bar charts comparing known copper resources, mean and median estimated 

 copper resources in undiscovered porphyry copper deposits in Southeast 

 Asia and Melanesia......................................................................................................................44

16. Bar charts comparing known and mean resource estimates...............................................48

 A1. Map showing tract location, known deposits, and significant porphyry copper

prospects for tract 142pCu7021, Sukhothai—China, Thailand, Myanmar, Lao 

People’s Democratic Republic, Cambodia, and Vietnam ......................................................67

 A2. Cumulative frequency plot showing the results of Monte Carlo computer simulation

 of undiscovered resources in tract 142pCu7021, Sukhothai—China, Thailand, 
vi

 Myanmar, Lao People’s Democratic Republic, Cambodia, and Vietnam............................68

 B1. Map showing tract location and porphyry copper deposits for tract

 142pCu7022, Malaysia—Malaysia, Thailand, Singapore, and Indonesia ...........................75

B2. Cumulative frequency plot showing the results of Monte Carlo computer simulation

of undiscovered resources in tract 142pCu7022, Malaysia—Malaysia, Thailand,

Singapore, and Indonesia...........................................................................................................76

 C1. Map showing tract location and significant porphyry copper prospects for tract 

142pCu7023, Mekong Delta—Vietnam, Cambodia, and Laos...............................................83

 C2. Cumulative frequency plot showing the results of Monte Carlo computer simulation 

of undiscovered resources in tract 142pCu7023, Mekong Delta—Vietnam, Cambodia, 

and Laos.........................................................................................................................................84

D1. Map showing tract location, deposits, and significant porphyry copper prospects for 

tract 142pCu7024, Wuntho-Popa—Myanmar and India........................................................90

D2. Cumulative frequency plot showing the results of Monte Carlo computer simulation 

of undiscovered resources in tract 142pCu7024, Wuntho-Popa—Myanmar and 

India................................................................................................................................................91

 E1. Map showing tract location, known deposits, and significant porphyry copper 

prospects for tract 142pCu7020, Sumatra Island—Indonesia............................................103

 E2. Map showing the regional setting for tract 142pCu7020, Sumatra Island—

Indonesia.....................................................................................................................................104

 E3. Map showing the distribution of permissive igneous rocks, tectonic features, and 

porphyry copper deposits and prospects for tract 142pCu7020, Sumatra Island—

Indonesia.....................................................................................................................................105

 E4. Cumulative frequency plot showing the results of Monte Carlo computer simulation 

of undiscovered resources in tract 142pCu7020, Sumatra Island—Indonesia ...............106

 F1. Map showing tract location, known deposits, and significant porphyry copper 

prospects for tract 142pCu7025, Sunda-Banda Arc—Indonesia.......................................119

 F2. Map showing the regional setting for tract 142pCu7025, Sunda-Banda Arc—

Indonesia.....................................................................................................................................120

 F3. Map showing the distribution of permissive igneous rocks, tectonic features, and 

porphyry copper deposits and prospects for tract 142pCu7025, Sunda-Banda Arc—

Indonesia.....................................................................................................................................122

 F4. Cumulative frequency plot showing the results of Monte Carlo computer simulation 

of undiscovered resources in tract 142pCu7025, Sunda-Banda Arc—Indonesia ..........124

G1. Map showing tract location and significant porphyry copper prospects for tract 

142pCu7026, West Sulawesi—Indonesia ..............................................................................133

G2. Map showing the regional setting for tract 142pCu7026, West Sulawesi—

Indonesia.....................................................................................................................................134

G3. Map showing the distribution of permissive igneous rocks, tectonic features, and 

porphyry copper prospects for tract 142pCu7026, West Sulawesi—

Indonesia.....................................................................................................................................135

G4. Cumulative frequency plot showing the results of Monte Carlo computer simulation 

of undiscovered resources in tract 142pCu7026, West Sulawesi—Indonesia ...............136

H1. Map showing tract location, known deposits, and significant porphyry copper 

prospects for tract 142pCu7027, North Sulawesi-Sangihe—Indonesia...........................145

H2. Map showing the regional setting for tract 142pCu7027, North Sulawesi-Sangihe—

Indonesia.....................................................................................................................................146
vii

H3. Map showing the distribution of permissive igneous rocks, tectonic features, and 

porphyry copper deposits and prospects for tract 142pCu7027, North SulawesiSangihe—Indonesia..................................................................................................................147

 H4. Cumulative frequency plot showing the results of Monte Carlo computer simulation 

of undiscovered resources 142pCu7027, North Sulawesi-Sangihe—Indonesia ............148

 I1. Map showing tract location, known deposits, and significant porphyry copper 

prospects for tract 142pCu7019, Central Kalimantan—Indonesia.....................................160

 I2. Map showing the regional setting for tract 142pCu7019, Central Kalimantan—

 Indonesia.....................................................................................................................................161

 I3. Map showing the distribution of permissive igneous rocks, tectonic features, and 

porphyry copper deposits and prospects for tract 142pCu7019, Central 

 Kalimantan—Indonesia ............................................................................................................162

 I4. Cumulative frequency plot showing the results of Monte Carlo computer simulation 

 of undiscovered resources in tract 142pCu7019, Central Kalimantan—Indonesia ........163

 J1. Map showing tract location and significant porphyry copper prospects for 

 tract 142pCu7201, Ambon Arc, Central Molucca Islands—Indonesia..............................171

 J2. Map showing the regional setting for tract 142pCu7201, Ambon Arc, Central 

 Molucca Islands—Indonesia ..................................................................................................172

 J3. Map showing the distribution of permissive igneous rocks, tectonic features, and 

porphyry copper deposits and prospects for tract 142pCu7201, Ambon Arc, Central 

Molucca Islands—Indonesia ..................................................................................................173

 J4. Cumulative frequency plot showing the results of Monte Carlo computer simulation 

 of undiscovered resources in tract 142pCu7201, Ambon Arc, Central Molucca 

 Islands—Indonesia ...................................................................................................................174

 K1. Map showing tract location, known deposits, and significant porphyry copper

 prospects for tract 142pCu7202, Halmahera Arc, North Molucca Islands—

 Indonesia.....................................................................................................................................183

 K2. Map showing the distribution of permissive igneous rocks and porphyry 

 copper deposits and prospects for tract 142pCu7202, Halmahera Arc, North 

 Molucca Islands—Indonesia ..................................................................................................184

 K3. Cumulative frequency plot showing the results of Monte Carlo computer simulation

 of undiscovered resources in tract 142pCu7202, Halmahera Arc, North Molucca 

 Islands—Indonesia ...................................................................................................................185

 L1. Map showing tract location and significant porphyry copper prospects for tract 

142pCu7205, Moon-Utawa-Ular Merah Areas—Indonesia................................................194

 L2. Map showing the distribution of permissive igneous rocks for tract 142pCu7205, 

 Moon-Utawa-Ular Merah Areas—Indonesia.......................................................................195

 L3. Cumulative frequency plot showing the results of Monte Carlo computer simulation 

 of undiscovered resources in tract 142pCu7205, Moon-Utawa-Ular Merah Areas—

Indonesia.....................................................................................................................................196

 M1. Map showing tract location, known deposits, and significant porphyry copper

 prospects for tract 142pCu7203, Western Medial New Guinea Magmatic 

 Belt—Indonesia .........................................................................................................................209

 M2. Map showing the distribution of permissive igneous rocks for tract 142pCu7203, 

Western Medial New Guinea Magmatic Belt—Indonesia.................................................210
viii

 M3. Cumulative frequency plot showing the results of Monte Carlo computer simulation

 of undiscovered resources in tract 142pCu7203, Western Medial New Guinea

 Magmatic Belt—Indonesia......................................................................................................211 

N1. Map showing tract location for tract 142pCu7204, Rotanburg-Taritatua Area—

 Indonesia.....................................................................................................................................217

N2. Map showing the distribution of permissive igneous rocks for tract 142pCu7204, 

Rotanburg-Taritatua Area—Indonesia..................................................................................218

 O1. Map showing the location and significant prospects and 

 occurrences for permissive tract 009pCu7203, Medial New Guinea Magmatic 

 Belt—Papua New Guinea and Indonesia .............................................................................236

 O2. Sub-tracts of 009pCu7203, Medial New Guinea Magmatic Belt—Papua New Guinea 

 and Indonesia, shown on a shaded relief map of New Guinea Island to illustrate 

 the extent of the highlands areas, with mapped areas of surface exposures of 

 late Miocene-Pliocene igneous rocks permissive for the occurrence of porphyry 

 copper deposits. Sub-tract A is the Indonesia-Papua New Guinea border area. .........237

 O3. Cumulative frequency plots showing the results of Monte Carlo computer 

 simulation of undiscovered resources in 009pCu7203, Medial New Guinea 

 Magmatic Belt—Papua New Guinea and Indonesia..........................................................238

 P1. Map showing the location, known deposits, and significant prospects and 

 occurrences for permissive tract 009pCu7205, Maramuni Arc—Papua New 

 Guinea..........................................................................................................................................248

 P2. Map showing igneous rocks used to delineate 009pCu7205, Maramuni Arc—

 Papua New Guinea....................................................................................................................249

 P3. Cumulative frequency plot showing the results of Monte Carlo computer 

 simulation of undiscovered resources in tract 009pCu7205, Maramuni Arc—

 Papua New Guinea....................................................................................................................250

 Q1. Map showing the location, known deposits, and significant prospects and 

 occurrences for permissive tract 009pCu7206, Miocene Alkaline Rocks of South-

 eastern New Guinea Island—Papua New Guinea..............................................................258

 Q2. Map showing igneous rocks used to delineate tract 009pCu7206, Miocene Alkaline 

Rocks of Southeastern New Guinea Island—Papua New Guinea...................................259

 Q3. Cumulative frequency plot showing the results of Monte Carlo computer simulation 

 of undiscovered resources in 009pCu7206, Miocene Alkaline Rocks of Southeastern 

 New Guinea Island—Papua New Guinea.............................................................................260

 R1. Map showing the location of permissive tract 142pCu7208, Inner Melanesian Arc 

terranes—Papua and West Papua, Indonesia.....................................................................265

 R2. Map showing igneous rocks used to delineate tract 142pCu7208, Inner Melanesian 

 Arc terranes—Papua and West Papua, Indonesia.............................................................266

 S1. Map showing the location of permissive tract 009pCu7208, Inner Melanesian Arc 

 Terranes—Northern New Guinea Island, Papua New Guinea .........................................273

 S2. Map showing igneous rocks used to delineate tract 009pCu7208, Inner Melanesian 

 Arc Terranes—Northern New Guinea Island, Papua New Guinea..................................274

 T1. Map showing the location, known deposits, and significant prospects and 

 occurrences for permissive tract 009pCu7209, Inner Melanesian Arc—New Britain,

 Papua New Guinea....................................................................................................................284
ix

 T2. Map showing igneous rocks used to delineate tract 009pCu7209, Inner Melanesian 

 Arc—New Britain, Papua New Guinea.................................................................................285

 T3. Cumulative frequency plot showing the results of Monte Carlo computer simulation 

 of undiscovered resources in tract 009pCu7209, Inner Melanesian Arc—New 

 Britain, Papua New Guinea......................................................................................................286

U1. Map showing the location, known deposits, and significant prospects and occurrences for of permissive tract 009pCu7207, Outer Melanesian Arc I—Papua New 

Guinea..........................................................................................................................................300

U2. Map showing igneous rocks used to delineate tract 009pCu7207, Outer Melanesian 

Arc I—Papua New Guinea.......................................................................................................301

U3. Cumulative frequency plot showing the results of Monte Carlo computer simulation 

of undiscovered resources in tract 009pCu7207, Outer Melanesian Arc I—Papua 

New Guinea.................................................................................................................................302

V1. Map showing the location, known deposits, and significant prospects and occurrences for of permissive tract 009pCu7210, Outer Melanesian Arc II—Melanesia 

(Solomon Islands, Vanuatu, and Fiji).......................................................................................323

V2. Maps showing subareas and igneous rocks used to delineate tract 009pCu7210, 

Outer Melanesian Arc II—Melanesia....................................................................................324

V3. Cumulative frequency plot showing the results of Monte Carlo computer simulation 

of undiscovered resources in tract 009pCu7210, Outer Melanesian Arc II—

Melanesia (Solomon Islands, Vanuatu, and Fiji)...................................................................329

Tables

 1. General characteristics of porphyry copper deposits in Southeast Asia and 

 Melanesia........................................................................................................................................9

 2. Principal magmatic arcs of Southeast Asia and Melanesia................................................11

 3. Principal geologic maps used for the assessment of Southeast Asia and 

 Melanesia .....................................................................................................................................27

 4. Permissive tracts for porphyry copper deposits in Southeast Asia and Melanesia........28

 5. Summary of identified resources in porphyry copper deposits of Southeast Asia 

 and Melanesia..............................................................................................................................34

 6. Statistical test results, porphyry copper assessment, Southeast Asia and 

 Melanesia .....................................................................................................................................38

 7. Estimates of numbers of undiscovered porphyry copper deposits, Southeast Asia 

 and Melanesia..............................................................................................................................42

 8. Summary of simulations of undiscovered resources in porphyry copper deposits 

 and comparison with identified copper and gold resources in porphyry copper 

 deposits within each permissive tract, Southeast Asia and Melanesia............................43

 A1. Summary of selected resource assessment results for tract 142pCu7021, 

 Sukhothai—China, Myanmar, Thailand, Lao People’s Democratic Republic, 

 Cambodia, and Vietnam..............................................................................................................58

A2. Map units that define tract 142pCu7021, Sukhothai—China, Myanmar, Thailand, Lao 

People’s Democratic Republic, Cambodia, and Vietnam......................................................60

A3. Identified porphyry copper resources in tract 142pCu7021, Sukhothai—China, Myanmar, Thailand, Lao People’s Democratic Republic, Cambodia, and Vietnam....................61
x

A4. Significant prospects and occurrences in tract 142pCu7021, Sukhothai—China, 

Myanmar, Thailand, Lao People’s Democratic Republic, Cambodia, and 

 Vietnam..........................................................................................................................................61

A5. Principal sources of information used for tract 142pCu7021, Sukhothai—China, 

 Myanmar, Thailand, Lao People’s Democratic Republic, Cambodia, and Vietnam..........63

A6. Undiscovered deposit estimates, deposit numbers, tract area, and deposit density 

for tract 142pCu7021, Sukhothai—China, Myanmar, Thailand, Lao People’s 

 Democratic Republic, Cambodia, and Vietnam......................................................................63

A7. Results of Monte Carlo simulations of undiscovered resources for tract 142pCu7021, 

Sukhothai—China, Myanmar, Thailand, Lao People’s Democratic Republic, 

 Cambodia, and Vietnam..............................................................................................................64

B1. Summary of selected resource assessment results for tract 142pCu7022, 

 Malaysia—Malaysia, Thailand, Singapore, and Indonesia .................................................69

B2. Map units that define tract 142pCu7022, Malaysia—Malaysia, Thailand, Singapore, 

 and Indonesia...............................................................................................................................71

B3. Identified porphyry copper resources in tract 142pCu7022, Malaysia—Malaysia, 

 Thailand, Singapore, and Indonesia ........................................................................................71

B4. Principal sources of information used for tract 142pCu7022, Malaysia—Malaysia, 

 Thailand, Singapore, and Indonesia ........................................................................................72

B5. Undiscovered deposit estimates, deposit numbers, tract area, and deposit density 

 for tract 142pCu7022, Malaysia—Malaysia, Thailand, Singapore, and Indonesia ..........72

B6. Results of Monte Carlo simulations of undiscovered resources for tract 142pCu7022, 

Malaysia—Malaysia, Thailand, Singapore, and Indonesia .................................................72

 C1. Summary of selected resource assessment results for tract 142pCu7023, Mekong 

Delta—Vietnam, Cambodia, and Lao People’s Democratic Republic ................................77

 C2. Map units that define tract 142pCu7023, Mekong Delta—Vietnam, Cambodia, and 

Lao People’s Democratic Republic...........................................................................................79

 C3. Significant prospects and occurrences in tract 142pCu7023, Mekong Delta—

Vietnam, Cambodia, and Lao People’s Democratic Republic ..............................................79

 C4. Principal sources of information for tract 142pCu7023, Mekong Delta—Vietnam, 

 Cambodia, and Lao People’s Democratic Republic...............................................................80

 C5. Undiscovered deposit estimates, deposit numbers, tract area, and deposit density 

for tract 142pCu7023, Mekong Delta—Vietnam, Cambodia, and Lao People’s Democratic Republic.............................................................................................................................81

 C6. Results of Monte Carlo simulations of undiscovered resources for tract 142pCu7023, 

Mekong Delta—Vietnam, Cambodia, and Lao People’s Democratic Republic.................81

D1. Summary of selected resource assessment results for tract 142pCu7024, WunthoPopa—Myanmar and India........................................................................................................85

D2. Identified porphyry copper resources in tract 142pCu7024, Wuntho-Popa—

Myanmar and India .....................................................................................................................87

D3. Significant prospects and occurrences in tract 142pCu7024, Wuntho-Popa—

Myanmar and India .....................................................................................................................87

D4. Principal sources of information for tract 142pCu7024, Wuntho-Popa—Myanmar 

and India........................................................................................................................................87

D5. Undiscovered deposit estimates, deposit numbers, tract area, and deposit density 

 for tract 142pCu7024, Wuntho-Popa—Myanmar and India .................................................88

D6. Results of Monte Carlo simulations of undiscovered resources for tract 142pCu7024, 

Wuntho-Popa—Myanmar and India........................................................................................88
xi

 E1. Summary of selected resource assessment results for tract 142pCu7020, Sumatra

 Island—Indonesia.......................................................................................................................92

E2. Map units that define tract 142pCu7020, Sumatra Island—Indonesia................................94

E3. Identified porphyry copper resources in tract 142pCu7020, Sumatra Island—

Indonesia .......................................................................................................................................98

E4. Significant prospects and occurrences in tract 142pCu7020, Sumatra Island—

Indonesia .......................................................................................................................................98

E5. Principal sources of information used for tract 142pCu7020, Sumatra Island—

Indonesia .......................................................................................................................................99

E6. Undiscovered deposit estimates, deposit numbers, tract area, and deposit density 

for tract 142pCu7020, Sumatra Island—Indonesia ...............................................................100

E7. Results of Monte Carlo simulations of undiscovered resources for tract 142pCu7020,

Sumatra Island—Indonesia......................................................................................................100

F1. Summary of selected resource assessment results for tract 142pCu7025, SundaBanda Arc—Indonesia..............................................................................................................107

F2. Map units that define tract 142pCu7025, Sunda-Banda Arc—Indonesia.........................109

F3. Identified porphyry copper resources in tract 142pCu7025, Sunda-Banda Arc—

Indonesia .....................................................................................................................................112

F4. Significant prospects and occurrences in tract 142pCu7025, Sunda-Banda Arc—

Indonesia .....................................................................................................................................113

F5. Principal sources of information used for tract 142pCu7025, Sunda-Banda Arc—

Indonesia .....................................................................................................................................114

F6. Undiscovered deposit estimates, deposit numbers, tract area, and deposit density 

for tract 142pCu7025, Sunda-Banda Arc—Indonesia ..........................................................115

F7. Results of Monte Carlo simulations of undiscovered resources for tract 142pCu7025,

Sunda-Banda Arc—Indonesia.................................................................................................116

G1. Summary of selected resource assessment results for tract 142pCu7026, West

Sulawesi—Indonesia ................................................................................................................126

G2. Map units that define tract 142pCu7026, West Sulawesi—Indonesia ..............................128

G3. Significant prospects and occurrences in tract 142pCu7026, West Sulawesi—

Indonesia .....................................................................................................................................130

G4. Principal sources of information used for tract 142pCu7026, West Sulawesi—

Indonesia .....................................................................................................................................130

G5. Undiscovered deposit estimates, deposit numbers, tract area, and deposit density 

for tract 142pCu7026, West Sulawesi—Indonesia................................................................131

G6. Results of Monte Carlo simulations of undiscovered resources for tract 142pCu7026,

West Sulawesi—Indonesia......................................................................................................131

H1. Summary of selected resource assessment results for tract 142pCu7027, North

Sulawesi-Sangihe—Indonesia ................................................................................................137

H2. Map units that define tract 142pCu7027, North Sulawesi-Sangihe—Indonesia.............139

H3. Identified porphyry copper resources in tract 142pCu7027, North SulawesiSangihe—Indonesia ..................................................................................................................140

H4. Significant prospects and occurrences in tract 142pCu7027, North SulawesiSangihe—Indonesia ..................................................................................................................140

H5. Principal sources of information used for tract 142pCu7027, North SulawesiSangihe—Indonesia ..................................................................................................................141
xii

 H6. Undiscovered deposit estimates, deposit numbers, tract area, and deposit density 

 for tract 142pCu7027, North Sulawesi-Sangihe—Indonesia..............................................142

 H7. Results of Monte Carlo simulations of undiscovered resources for tract 142pCu7027,

 North Sulawesi-Sangihe—Indonesia ....................................................................................143

I1. Summary of selected resource assessment results for tract 142pCu7019, Central 

 Kalimantan—Indonesia ............................................................................................................149

I2. Map units that define tract 142pCu7019, Central Kalimantan—Indonesia ......................151

I3. Identified porphyry copper resources in tract 142pCu7019, Central Kalimantan—

Indonesia.....................................................................................................................................152

I4. Significant prospects and occurrences in tract 142pCu7019, Central Kalimantan—

 Indonesia.....................................................................................................................................153

I5. Principal sources of information used for tract 142pCu7019, Central Kalimantan—

 Indonesia.....................................................................................................................................155

I6. Undiscovered deposit estimates, deposit numbers, tract area, and deposit density 

 for tract 142pCu7019, Central Kalimantan—Indonesia........................................................155

I7. Results of Monte Carlo simulations of undiscovered resources for tract 142pCu7019, 

Central Kalimantan—Indonesia..............................................................................................156

 J1. Summary of selected resource assessment results for tract 142pCu7201, Ambon 

 Arc, Central Molucca Islands—Indonesia............................................................................164

 J2. Map units that define tract 142pCu7201, Ambon Arc, Central Molucca Islands—

 Indonesia.....................................................................................................................................165

 J3. Significant prospects and occurrences in tract 142pCu7201, Ambon Arc, Central 

Molucca Islands—Indonesia..................................................................................................166

 J4. Principal sources of information used for tract 142pCu7201, Ambon Arc, Central

 Molucca Islands—Indonesia ..................................................................................................168

 J5. Undiscovered deposit estimates, deposit numbers, tract area, and deposit density 

 for tract 142pCu7201, Ambon Arc, Central Molucca Islands—Indonesia........................168

 J6. Results of Monte Carlo simulations of undiscovered resources for tract 142pCu7201,

 Ambon Arc, Central Molucca Islands—Indonesia ..............................................................169

 K1. Summary of selected resource assessment results for tract 142pCu7202, Halmahera 

Arc—North Molucca Islands, Indonesia ..............................................................................175

 K2. Map units that define tract 142pCu7202, Halmahera Arc, North Molucca Islands—

 Indonesia.....................................................................................................................................176

 K3. Identified porphyry copper resources in tract 142pCu7202, Halmahera Arc, North

 Molucca Islands—Indonesia ..................................................................................................177

 K4. Significant prospects and occurrences in tract 142pCu7202, Halmahera Arc, North

 Molucca Islands—Indonesia ..................................................................................................179

 K5. Principal sources of information used for tract 142pCu7202, Halmahera Arc, North 

Molucca Islands—Indonesia..................................................................................................180

 K6. Undiscovered deposit estimates, deposit numbers, tract area, and deposit density 

 for tract 142pCu7202, Halmahera Arc, North Molucca Islands—Indonesia ...................180

 K7. Results of Monte Carlo simulations of undiscovered resources for tract 142pCu7202,

 Halmahera Arc, North Molucca Islands—Indonesia..........................................................180

 L1. Summary of selected resource assessment results for tract 142pCu7205, Moon-

 Utawa-Ular Merah Areas—Indonesia...................................................................................186

 L2. Map units that define tract 142pCu7205, Moon-Utawa-Ular Merah Areas—

 Indonesia.....................................................................................................................................188
xiii

L3. Significant prospects and occurrences tract 142pCu7205, Moon-Utawa-Ular 

 Merah Areas—Indonesia ........................................................................................................189

L4. Principal sources of information used for tract 142pCu7205, Moon-Utawa-Ular 

 Merah Areas—Indonesia ........................................................................................................189

L5. Undiscovered deposit estimates, deposit numbers, tract area, and deposit density 

 for tract 142pCu7205, Moon-Utawa-Ular Merah Areas—Indonesia................................190

L6. Results of Monte Carlo simulations of undiscovered resources for tract 

 142pCu7205, Moon-Utawa-Ular Merah Areas—Indonesia................................................191

 M1. Summary of selected resource assessment results for tract 142pCu7203, Western 

Medial New Guinea Magmatic Belt—Indonesia.................................................................197

 M2. Map units that define tract 142pCu7203, Western Medial New Guinea Magmatic 

 Belt—Indonesia.........................................................................................................................199

 M3. Identified porphyry copper resources in tract 142pCu7203, Western Medial New 

 Guinea Magmatic Belt—Indonesia........................................................................................200

 M4. Significant prospects and occurrences in tract 142pCu7203, Western Medial New 

Guinea Magmatic Belt—Indonesia........................................................................................202

 M5. Principal sources of information used for tract 142pCu7203, Western Medial New 

Guinea Magmatic Belt—Indonesia........................................................................................204

 M6. Undiscovered deposit estimates, deposit numbers, tract area, and deposit density 

 for tract 142pCu7203, Western Medial New Guinea Magmatic Belt—Indonesia..........205

 M7. Results of Monte Carlo simulations of undiscovered resources for tract 

 142pCu7203, Western Medial New Guinea Magmatic Belt—Indonesia .........................205

 N1. Summary of selected information for tract 142pCu7204, Rotanburg-Taritatua 

 Area—Indonesia .......................................................................................................................212

 N2. Map units that define tract 142pCu7204, Rotanburg-Taritatua Area—Indonesia..........213

 N3. Principal sources of information used for tract 142pCu7204, Rotanburg-Taritatua 

Area—Indonesia.......................................................................................................................214

 O1. Summary of selected information for tract 009pCu7203, Eastern Medial New 

 Guinea Magmatic Belt—Papua New Guinea and Indonesia............................................219

 O2. Map units that define tract 009pCu7203, Eastern Medial New Guinea Magmatic 

 Belt—Papua New Guinea and Indonesia.............................................................................222

 O3. Identified porphyry copper resources in tract 009pCu7203, Eastern Medial New 

 Guinea Magmatic Belt—Papua New Guinea and Indonesia............................................226

 O4. Significant prospects and occurrences in tract 009pCu7203, Eastern Medial New 

Guinea Magmatic Belt—Papua New Guinea and Indonesia............................................227

 O5. Principal sources of information used for tract 009pCu7203, Eastern Medial New 

Guinea Magmatic Belt—Papua New Guinea and Indonesia............................................230

 O6. Undiscovered deposit estimates, deposit numbers, tract area, and deposit density 

 for tract 009pCu7203, Eastern Medial New Guinea Magmatic Belt—Papua New 

 Guinea and Indonesia...............................................................................................................230

 O7. Results of Monte Carlo simulations of undiscovered resources for tract 

 009pCu7203, Eastern Medial New Guinea Magmatic Belt—Papua New Guinea 

 and Indonesia ............................................................................................................................231

 P1. Summary of selected information for tract 009pCu7205, Maramuni Arc—Papua 

 New Guinea................................................................................................................................239

 P2. Map units that define tract 009pCu7205, Maramuni Arc—Papua New Guinea.............241
xiv

P3. Identified porphyry copper resources in tract 009pCu7205, Maramuni Arc—

 Papua New Guinea...................................................................................................................243

P4. Significant prospects and occurrences in tract 009pCu7205, Maramuni Arc—

 Papua New Guinea...................................................................................................................243

P5 Principal sources of information used for tract 009pCu7205, Maramuni Arc—

 Papua New Guinea...................................................................................................................244

P6. Undiscovered deposit estimates, deposit numbers, tract area, and deposit 

 density for 009pCu7205, Maramuni Arc—Papua New Guinea..........................................245

P7. Results of Monte Carlo simulations of undiscovered resources for 009pCu7205, 

 Maramuni Arc—Papua New Guinea.....................................................................................245

Q1. Summary of selected information for tract 009pCu7206, Miocene alkaline rocks of 

Southeastern New Guinea Island—Papua New Guinea ...................................................251

Q2. Map units that define tract 009pCu7206, Miocene alkaline rocks of Southeastern 

 New Guinea Island—Papua New Guinea 09pCu7206, Miocene alkaline rocks of 

 Southeastern New Guinea Island—Papua New Guinea ...................................................252

Q3. Significant prospects and occurrences tract 009pCu7206, Miocene alkaline rocks 

 of Southeastern New Guinea Island—Papua New Guinea...............................................254

Q4. Principal sources of information used for tract 009pCu7206, Miocene alkaline 

 rocks of Southeastern New Guinea Island—Papua New Guinea....................................254

Q5. Undiscovered deposit estimates, deposit numbers, tract area, and deposit density 

 for 009pCu7206, Miocene alkaline rocks of Southeastern New Guinea Island—

Papua New Guinea....................................................................................................................255

Q6. Results of Monte Carlo simulations of undiscovered resources for tract 009pCu7206, 

 Miocene alkaline rocks of Southeastern New Guinea Island—Papua New Guinea............255

R1. Summary of selected information for tract 142pCu7208, Inner Melanesian Arc 

terranes—Papua and West Papua, Indonesia.....................................................................261

R2. Map units that define tract 142pCu7208, Inner Melanesian Arc Terranes I—

 Papua and West Papua, Indonesia ........................................................................................262

R3. Principal sources of information used for tract 142pCu7208, Inner Melanesian 

 Arc Terranes I—Papua and West Papua, Indonesia ..........................................................263

S1. Summary of selected information for tract 009pCu7208, Inner Melanesian Arc 

 Terranes II—Northern New Guinea Island, Papua New Guinea......................................268

S2. Map units that define tract 009pCu7208, Inner Melanesian Arc Terranes II—

 Northern New Guinea Island, Papua New Guinea..............................................................270

S3. Principal sources of information used for tract 009pCu7208, Inner Melanesian 

 Arc Terranes II—Northern New Guinea Island, Papua New Guinea...............................271

T1. Summary of selected information for tract 009pCu7209, Inner Melanesian Arc 

 Terranes II—New Britain, Papua New Guinea ....................................................................275

T2. Map units that define tract 009pCu7209, Inner Melanesian Arc Terranes II—

 New Britain, Papua New Guinea............................................................................................276

T3. Identified porphyry copper resources in tract 009pCu7209, Inner Melanesian 

 Arc—New Britain, Papua New Guinea.................................................................................278

T4. Significant prospects and occurrences in tract 009pCu7209, Inner Melanesian 

 Arc Terranes II—New Britain, Papua New Guinea.............................................................279

T5. Principal sources of information used for tract 009pCu7209, Inner Melanesian 

 Arc Terranes II—New Britain, Papua New Guinea.............................................................280
xv

T6. Undiscovered deposit estimates, deposit numbers, tract area, and deposit density for 

009pCu7209, Inner Melanesian Arc Terranes II—New Britain, Papua New Guinea.....281

T7. Results of Monte Carlo simulations of undiscovered resources in tract 009pCu7209, 

Inner Melanesian Arc Terranes II—New Britain, Papua New Guinea............................281

U1. Summary of selected information for tract 009pCu7207, Outer Melanesian Arc I—

Papua New Guinea....................................................................................................................287

U2. Map units that define tract 009pCu7207, Outer Melanesian Arc I—Papua 

 New Guinea................................................................................................................................289

U3. Identified porphyry copper resources in tract 009pCu7207, Outer Melanesian 

 Arc I—Papua New Guinea ......................................................................................................291

U4. Significant prospects and occurrences in tract 009pCu7207, Outer Melanesian 

 Arc I—Papua New Guinea ......................................................................................................292

U5. Principal sources of information used for tract 009pCu7207, Outer Melanesian 

 Arc I—Papua New Guinea ......................................................................................................296

U6. Undiscovered deposit estimates, deposit numbers, tract area, and deposit density 

for tract 009pCu7207, Outer Melanesian Arc I—Papua New Guinea...............................296

U7. Results of Monte Carlo simulations of undiscovered resources in tract 

 009pCu7207, Outer Melanesian Arc I—Papua New Guinea..............................................297

V1. Summary of selected information for tract 009pCu7210, Outer Melanesian Arc II—

 Melanesia (Solomon Islands, Vanuatu, and Fiji) ..................................................................303

V2. Map units that define tract 009pCu7210, Outer Melanesian Arc II—Melanesia 

 (Solomon Islands, Vanuatu, and Fiji) ......................................................................................307

V3. Identified porphyry copper resources in tract 009pCu7210, Outer Melanesian 

 Arc II—Melanesia (Solomon Islands, Vanuatu, and Fiji)....................................................310

V4. Significant prospects and occurrences in tract 009pCu7210, Outer Melanesian 

 Arc II—Melanesia (Solomon Islands, Vanuatu, and Fiji)....................................................312

V5. Principal sources of information used for tract 009pCu7210, Outer Melanesian 

 Arc II—Melanesia (Solomon Islands, Vanuatu, and Fiji)....................................................316

V6. Undiscovered deposit estimates, deposit numbers, tract area, and deposit density 

 for tract 009pCu7210, Outer Melanesian Arc II—Melanesia (Solomon Islands, 

 Vanuatu, and Fiji) .......................................................................................................................317

V7. Results of Monte Carlo simulations of undiscovered resources in tract 009pCu7210, 

Outer Melanesian Arc II—Melanesia (Solomon Islands, Vanuatu, and Fiji)...................317

ANOVA Analysis of variance

GIS Geographic Information System

g/t grams per metric ton

kt thousand metric tons

Ma million of years before the present

Mt million metric tons

PGE platinum-group elements

REE rare-earth elements

SHRIMP sensitive high resolution ion microprobe

SSIB small-scale digital international boundaries

t metric ton (tonne) or megagram (Mg)

USGS United States Geological Survey
xvi

Conversion Factors

Inch/Pound to SI

Multiply by To obtain

Length

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

yard (yd) 0.9144 meter (m)

Area

acre 0.4047 hectare (ha)

acre 0.004047 square kilometer (km2)

square mile (mi2) 259.0 hectare (ha)

square mile (mi2) 2.590 square kilometer (km2) 

Mass

ounce, troy (troy oz) 31.015 gram (g) 

ounce, troy (troy oz) 32150.75 megagram (Mg) 

ton, short (T) (2,000 lb) 0.9072 megagram (Mg) 

SI to Inch/Pound

Multiply by To obtain

Length

meter (m) 3.281 foot (ft) 

kilometer (km) 0.6214 mile (mi)

meter (m) 1.094 yard (yd) 

Area

hectare (ha) 2.471 acre

square hectometer (hm2

) 2.471 acre

hectare (ha) 0.003861 square mile (mi2

) 

square kilometer (km2

) 0.3861 square mile (mi2)

Mass

gram (g) 0.03215 ounce, troy (troy oz)

megagram (Mg) 1.102 ton, short (2,000 lb)

megagram (Mg) 0.9842 ton, long (2,240 lb)

Other conversions used in this report

metric ton (t) 1 megagram (Mg)

troy ounce per short ton 34.2857 gram per metric ton (g/t)

percent 10,000 parts per million (ppm) 

or grams per metric ton (g/t) 

percent metal 0.01 x ore tonnage, metric tons metric tons of metal
Abstract

The U.S. Geological Survey collaborated with member 

countries of the Coordinating Committee for Geoscience 

Programmes in East and Southeast Asia (CCOP) on an assessment of the porphyry copper resources of Southeast Asia and 

Melanesia as part of a global mineral resource assessment. The 

region hosts world-class porphyry copper deposits and underexplored areas that are likely to contain undiscovered deposits. 

Examples of known porphyry copper deposits include Batu 

Hijau and Grasberg in Indonesia; Panguna, Frieda River, and 

Ok Tedi in Papua New Guinea; and Namosi in Fiji.

This assessment covers the countries of Cambodia, Indonesia, Lao People’s Democratic Republic, Malaysia, Myanmar, Papua New Guinea, Singapore, Thailand, and parts of 

southeastern China, India, the Solomon Islands, Vanuatu, and 

Fiji. Twenty-two geographic areas were delineated as tracts 

that are permissive for porphyry copper deposits in Southeast 

Asia. Permissive tracts are grouped into four broadly defined 

geographic/geologic areas, as follows: (1) the Indochina 

Peninsula area, (2) Indonesian and Malaysian Islands, (3) New 

Guinea Island and Papuan New Guinea islands, and (4) Melanesia. Individual tracts range from less than 1,000 to more 

than 350,000 square kilometers in area. Permissive tracts 

are based on mapped and inferred subsurface (<1 kilometer 

depth) distributions of igneous rocks of specific age ranges 

that define magmatic arcs and magmatic belts that are likely 

to contain porphyry copper deposits. Most of these magmatic 

arcs are subduction-related, although some have porphyrystyle deposits occurring in postcollisional and (or) poorly 

understood tectonic settings. Although maps at a variety of 

different scales were used in the compilation, the final tract 

boundaries are intended for use at a scale of 1:1,000,000.

Global grade and tonnage models for porphyry copper deposits were evaluated. Most of the known deposits are 

best described as fitting the copper-gold (Cu-Au) subtype of 

porphyry copper deposit. For some permissive tracts, a general 

porphyry copper-gold-molybdenum (Cu-Au-Mo) model was 

used. Assessment participants estimated numbers of undiscovered deposits at different levels of confidence for most of the 

permissive tracts. These estimates were combined with grade 

and tonnage models using a Monte Carlo simulation to estimate undiscovered resources. Additional resources in extensions of deposits with identified resources were not evaluated.

Assessment results, presented in tables and graphs, show 

mean amounts of metal and mineralized rock in undiscovered 

deposits at different quantile levels, as well as the arithmetic 

mean for each tract.

This assessment estimated a mean of 89 undiscovered 

porphyry copper deposits for the assessed permissive tracts 

in Southeast Asia and Melanesia. About 288 million metric 

tons (Mt) of copper and 18,000 metric tons (t) of gold, as well 

as byproduct molybdenum and silver, could be associated 

with undiscovered deposits. This represents about four times 

the number of deposits with identified resources (23) already 

discovered in Southeast Asia; reliable reported identified 

Porphyry Copper Assessment of Southeast Asia and 

Melanesia

By Jane M. Hammarstrom1, Arthur A. Bookstrom6, Connie L. Dicken1, Benjamin J. Drenth8, Steve Ludington2, 

Gilpin R. Robinson, Jr.1

, Bambang Tjahjono Setiabudi3, Wudhikarn Sukserm4, Dwi Nugroho Sunuhadi3, Alexander Yan Sze Wah5

, and Michael L. Zientek6,with contributions from Dennis P. Cox7, Pairatt Jarnyaharn4, 

Gwaibo Kopi12, Nguyen Thi Minh Ngoc9

, Pichai Otarawanna4, Chen Shick Pei10, Ung Phany11, Nguyen Vay 

Quy9

, Takehiro Sakimoto4, Dulcie Saroa12, Norberta Soares da Costa13, Sieng Sotham11, I.M. Sim11, Nguyen 

Nhu Trung4 , Somob Wongsomasak4

, Boonsong Yokarti4, and Khin Zaw14

1

U.S. Geological Survey, Reston, Virginia, United States.

2

U.S. Geological Survey, Menlo Park, California, United States.

3

Geological Agency of Indonesia, Bandung, Indonesia.

4

Royal Thai Government Department of Mineral Resources, Bangkok, 

Thailand. 5

Mineral and Geoscience Department, Sabah, Malaysia.

6

U.S. Geological Survey, Spokane, Washington, United States.

7

Palo Alto, California, United States.

8

U.S. Geological Survey, Denver, Colorado, United States.

9

Department of Geology and Minerals of Vietnam, Hanoi, Vietnam.

10Coordinating Committee for Geoscience Programmes in East and Southeast Asia (CCOP) Technical Secretariat, Bangkok, Thailand. 11Department of Geology and Mines, Phnom Penh, Cambodia.

12Mineral Resources Authority of Papua New Guinea, Port Moresby, Papua 

New Guinea. 13Director of Geology and Mineral Resources, Dili, Timor Leste.

14University of Tasmania, Hobart, Australia.
2 Porphyry Copper Assessment of Southeast Asia and Melanesia

resources for those 23 deposits total 84 Mt of copper and 

6,000 t of gold. Eleven permissive tracts have no known 

porphyry copper deposits with reported resources. Three of 

those 11 tracts lacked sufficient information for a probabilistic 

assessment and are discussed in qualitative terms.

On a regional basis, both the Indochina Peninsula area 

and the Indonesian-Malaysian Islands area are estimated 

to contain about 10 times as much in place copper in 

undiscovered porphyry copper deposits as has been identified 

to date. For the New Guinea Island areas, the ratio of 

undiscovered to identified copper resources is about 2. Some 

parts of the region have a long history of porphyry exploration 

cycles and mine development, interrupted at times by political 

and social unrest, environmental concerns, and natural 

disasters. Changes in mining laws within the region and the 

recent high price of gold on the world market have prompted 

renewed interest in porphyry copper deposits in Southeast Asia 

and Melanesia. However, predicted undiscovered deposits 

may not be found, and if found, may not be developed.

This assessment includes an overview of the assessment 

results with summary tables. Detailed descriptions of each 

tract are included in appendixes, with estimates of numbers of 

undiscovered deposits, and probabilistic estimates of amounts 

of copper, molybdenum, gold, and silver that could be 

contained in undiscovered deposits for each permissive tract. 

A geographic information system (GIS) that accompanies 

the report includes tract boundaries and a database of known 

porphyry copper deposits and significant prospects.

Introduction

The Southeast Asia-Melanesia region is one of the 

world’s most productive copper provinces. The region hosts 

world-class porphyry copper deposits, including the Batu 

Hijau and Grasberg deposits in Indonesia; the Panguna, 

Frieda River, and Ok Tedi deposits in Papua New Guinea; 

and the Namosi deposit in Fiji (fig. 1). Indonesia ranked 

sixth in world copper production in 2010 (U.S. Geological 

Survey, 2011). The Grasberg porphyry copper-gold deposit 

is the world’s largest producer of gold. Parts of Southeast 

Asia remain underexplored. In recent years, new target areas 

have been recognized, historical mining districts continue 

to be explored, and new deposits continue to be discovered 

through greenfields exploration. Most of the copper 

production in Southeast Asia comes from porphyry copper 

deposits. Porphyry copper deposits provide approximately 

60 percent of the world's discovered copper (Singer, 1995). 

The most common ore minerals in porphyry copper deposits 

are chalcopyrite (CuFeS2) and bornite (Cu5FeS4), distributed 

in stockwork veinlets and disseminations in hydrothermally 

altered intrusions and adjacent wallrock. Secondary copper 

minerals, such as chalcocite (Cu2S), in oxidized, supergene 

enrichment zones comprise a major part or all of the ore in 

some deposits. Molybdenum, silver, and gold are important 

coproducts or byproducts in many deposits.

A probabilistic mineral resource assessment of undiscovered resources in porphyry copper deposits in Southeast 

Asia and Melanesia was undertaken as part of a global mineral 

resource assessment (Schulz and Briskey, 2003). The purpose of the assessment was to (1) delineate permissive areas 

(tracts) for undiscovered porphyry copper deposits at a scale 

of 1:1,000,000, (2) provide a database of known porphyry copper deposits and significant prospects, (3) estimate numbers 

of undiscovered deposits within those permissive tracts, and 

(4) provide probabilistic estimates of amounts of copper (Cu), 

molybdenum (Mo), gold (Au), and silver (Ag) that could be 

contained in undiscovered deposits for each permissive tract. 

The U.S. Geological Survey (USGS) collaborated with the 

Coordinating Committee for Geoscience Programmes in East 

and Southeast Asia (CCOP) on the joint assessment project for 

Southeast Asia.

CCOP is an intergovernmental organization founded to 

facilitate and coordinate applied geoscience projects (http://

www.ccop.or.th/). The CCOP’s mission is to contribute to 

economic development and improve the quality of life in the 

region. The CCOP has eleven member countries—Cambodia, China, Indonesia, Japan, Malaysia, Papua New Guinea, 

Philippines, Singapore, South Korea, Thailand, and Vietnam. 

Fourteen other countries, including the United States, participate in CCOP activities as cooperating countries.

This assessment report covers parts of the CCOP-member 

countries that contain known porphyry copper deposits, as 

well as areas that may contain undiscovered deposits, based on 

available geologic information. The region was divided into 

four broadly defined geographic/geologic areas for the assessment. These areas are (1) the Indochina Peninsula area, (2) 

Indonesian and Malaysian Islands, (3) New Guinea Island and 

Papuan New Guinea islands, and (4) Melanesia (fig. 1). On the 

basis of available information, some CCOP member countries 

have little or no recognized potential for porphyry copper 

deposits (Timor Leste) although these countries have known 

deposits and potential for undiscovered deposits of other types. 

The porphyry copper assessments for other CCOP-member 

countries (the Philippines, China, Japan, and South Korea) are 

in separate reports. This assessment report covers the countries 

of Cambodia, Indonesia, Lao People’s Democratic Republic, 

Malaysia, Myanmar, Papua New Guinea, Singapore, Thailand, 

parts of India, and the Melanesian nations of the Solomon 

Islands, Vanuatu, and Fiji (fig. 1).

The assessment of undiscovered porphyry copper 

deposits in Southeast Asia and Melanesia was done using 

the three-part form of mineral resource assessment based on 

mineral deposit models (Singer 1993, 2007a, b; Singer and 

Berger, 2007; Singer and Menzie, 2010). In applying the threepart form of mineral resource assessment, geographic areas 

(permissive tracts) are delineated using geologic, geochemical, 

and geophysical features typically associated with the type of 

deposit under consideration. The amount of metal contained in 

undiscovered deposits is estimated by using grade and tonnage 

models. Grade and tonnage models are frequency distributions 

of tonnages and grades of thoroughly explored deposits, based 
Introduction 3

on total production, reserves, and resources at the lowest 

available cutoff grade. For porphyry copper deposit models, 

a spatial rule is used to group grade and tonnage information to represent deposits as geologic entities: all mineralized 

rock or alteration within 2 kilometers (km) is combined as 

one deposit for model construction (Singer and others, 2008). 

Data for deposits within the permissive tracts are compared 

with global grade and tonnage models using statistical tests, 

along with other geologic information, to select an appropriate model for assessment.

Estimates of numbers of undiscovered deposits in each 

permissive tract are made at different confidence levels using 

a variety of estimation strategies to express the degree of 

belief that some fixed but unknown number of deposits exists 

within the tract. These estimates represent a measure of the 

favorability of the tract and the estimator’s uncertainty about 

what may exist (Singer, 2007a). The Monte Carlo simulation 

that is used to combine deposit number estimates with grade 

and tonnage models to produce a probabilistic estimate of 

undiscovered resources is the EMINERS program (Bawiec 

and Spanski, 2012; Duval, 2012), based on the algorithms 

described by Root and others (1992).

The assessment data and results for each permissive 

tract are presented in a standardized format in appendixes A 

through V of this report. Each permissive tract is assigned a 

unique identifier (Coded_Id), as well as a geographic/geologic name. Identifiers are based on United Nations regions 

(142 for Asia, 009 for Oceania), deposit type (pCu), and a 

4-digit number. Permissive-tract boundaries and point locations of deposits and significant prospects are included as 

shapefiles in a geographic information system (GIS) format 

that accompanies this report (appendix W). Political boundaries are based on data maintained by the U.S. Department of 

State (2009).

Southeast Asia and Melanesia are areas of active 

exploration. This report reflects the porphyry copper projects known to the assessment team as of March 2011. Many 

active exploration projects focus on large concessions that 

attracted attention owing to reported gold associated with 

historical workings. Epithermal gold deposits are the initial 

targets of many projects, owing to the current (2011) high 

price of gold. Company reports mention porphyry systems 

associated with some of these targets, and the association 

of these deposit types is well known in Southeast Asia (for 

example, Cooke and others, 1998); however, delineation of 

a porphyry copper deposit, if present, awaits further exploration in most cases.

Terminology

The terminology used in this study follows the definitions used in the 1998 assessment of undiscovered deposits 

of gold, silver, copper, lead, and zinc in the United States 

(U.S. Geological Survey National Mineral Resource Assessment Team, 2000; U.S. Bureau of Mines and U.S. Geological Survey, 1976; Bates and Jackson, 1997). The terminology is intended to represent standard definitions and general 

usage by the minerals industry and the resource-assessment 

community. Some countries in the world recently have 

adopted more rigorous definitions of terms for estimating 

mineral resources and mineral reserves and for reporting 

exploration information to comply with legal mandates 

(Committee for Mineral Reserves International Reporting 

Standards, 2006).

Mineral deposit. A mineral concentration of sufficient size 

and grade that it might, under the most favorable of circumstances, be considered to have potential for economic 

development.

Undiscovered mineral deposit. A mineral deposit believed 

to exist 1 km or less below the surface of the ground, or an 

incompletely explored mineral occurrence or prospect that 

could have sufficient size and grade to be classified as a 

deposit.

Descriptive mineral deposit model. A set of data in a convenient, standardized form that describes a group of mineral 

deposits having similar characteristics.

Grade and tonnage model. Frequency distributions of the 

grades and sizes of thoroughly explored, and (or) completely mined out, individual mineral deposits that are classified by a descriptive mineral deposit model.

Permissive tract. The surface projection of a volume of rock 

where the geology permits the existence of a mineral deposit 

of a specified type. The probability of deposits of the type 

being studied occurring outside the tract is negligible.

Resource. A mineral concentration of sufficient size and 

grade, and in such form and amount that economic extraction of a commodity from the concentration is currently or 

potentially feasible.

Identified resources. Resources whose location, grade, 

quality, and quantity are known or can be estimated from 

specific geologic evidence. For this assessment, identified resources are the deposits that constitute the grade and 

tonnage models used in the assessment (which can include 

measured, indicated, and inferred mineral resources at the 

lowest available cutoff grade). In addition, deposits that are 

not included in the models used for the assessment may be 

considered as identified resources if they are characterized 

well enough by deposit type, grade, and tonnage to meet 

U.S. Securities and Exchange Commission or CRIRSCO15

reporting guidelines.

15 Committee for Mineral Reserves International Reporting Standards 

(2006) (http://www.crirsco.com/welcome.asp).
4 Porphyry Copper Assessment of Southeast Asia and Melanesia

110° E 130° E 

20° N

0°

20° S

Mamut

Monywa

Tangse

Phu Kam

Mengapur

Tapadaa

Kaputusan

Batu Hijau

Tombulilato

PHILIPPINES

MALAYSIA MALAYSIA

CHINA

(TAIWAN)

INDONESIA

CHINA

MYANMAR

THAILAND

VIETNAM

INDIA

CAMBODIA

AUSTRALIA

INDONESIA

CHINA

(HAINAN)

LAOS

SINGAPORE

INDIAN OCEAN

Andaman Sea

Gulf of Thailand

South China Sea

 Java Sea

 Timor Sea

0 500 1,000 KILOMETERS

0 250 500 MILES

Political boundary source: U.S. Department of State (2009)

Projection: Asia South Albers Equal Area Conic;

Central meridian 115° E; latitude of origin 15° S

Figure 1. Map showing permissive tracts for porphyry copper deposits in Southeast Asia and Melanesia, grouped 

by geographic areas. Porphyry copper deposits (filled squares) and significant prospects (open squares) are shown; 

deposits mentioned in the text are labeled.
Introduction 5

150° E 170° E

Arie

Simuku

Panguna

Yandera Ok Tedi

Grasberg

Wafi-Golpu

Star Mt. Futik

Star Mt. Nong River

Kodu (Ofi Creek,Mount Bini)

Koloula (Guadalcanal Joint Venture)

Frieda River

Waivaka

Namosi

INDONESIA

PAPUA

NEW GUINEA

SOLOMAN

ISLANDS

VANUATU

FIJI

NORTH PACIFIC OCEAN

Coral Sea

Arafura Sea

Deposit

Prospect

EXPLANATION

Indochina Peninsula area

Melanesia

New Guinea and other islands

Indonesian and Malaysian 

 Islands area

Porphyry copper tracts

of Southeast Asia
6 Porphyry Copper Assessment of Southeast Asia and Melanesia

Undiscovered resources. Resources in undiscovered mineral deposits whose existence is postulated on the basis of 

indirect geologic evidence. These include undiscovered 

resources in known types of mineral deposits postulated 

to exist in permissive geologic settings. Undiscovered 

resources may include active mines if the resource is delineated incompletely. For example, a deposit that is explored 

only partially and reported as “open to the west or open at 

depth” could be counted as an undiscovered deposit. Undiscovered resources in extensions to identified resources are 

not addressed explicitly in the assessment process.

Calc-alkaline, calc-alkalic; alkaline, alkalic. These terms 

are used in a general, non-rigorous manner to refer to plutonic igneous rocks of granitoid composition (calc-alkaline 

or calc-alkalic) and of syenitoid through dioritoid to gabbroid 

composition (alkaline or alkalic) and their volcanic equivalents (see Le Maitre and others, 2002, provisional field classifications, figures 2.10 and 2.19). In the igneous literature, 

the terms “-alkaline” and “-alkalic” are defined and used in 

multiple and inconsistent ways (see Arculus, 2003). For this 

assessment, the term calc-alkalic is used synonymously for 

calc-alkaline, and alkalic is used synonymously for alkaline, 

as well as for their associated deposits, which are classified 

as calc-alkaline (or calc-alkalic) Cu±Mo±Au or alkaline (or 

alkalic) porphyry copper subtypes.

Porphyry Copper Assessment of Southeast Asia and Melanesia

Porphyry copper deposits typically form in magmatic 

arcs, primarily in subduction-related tectonic settings. 

Postsubduction, collisional, and extensional back-arc settings also are recognized as permissive environments for the 

formation of porphyry copper-gold deposits, where processes 

such as postsubduction lithosphere thickening or extension, 

delamination, slab rollback, and asthenospheric upwelling may have facilitated remelting of lithosphere (Richards, 2009). Postsubduction porphyry copper-gold deposits 

typically are associated with mildly alkaline, rather than 

calc-alkaline, magmas, and may form isolated complexes in 

contrast to volcanoplutonic arcs (Richards, 2009). Molybdenum-rich porphyry copper deposits tend to be associated 

with calc-alkalic rocks in continental arcs, and gold-rich 

porphyry copper deposits tend to be associated with diorites 

or alkaline igneous complexes in island arcs, back-arc basins, 

or extensional settings. However, both molybdenum- and 

gold-rich deposits can occur within the same tectonic setting.

Porphyry Copper Models

Cox and Singer (1986) included a general descriptive 

mineral-deposit model for porphyry copper deposits, as well 

as separate descriptive models for Cu-Au and Cu-Mo subtypes 

(Cox, 1986a,b,c). However, recent descriptive models have 

not identified sufficient geologic criteria to justify division of 

a general geologic model for porphyry copper deposits into 

subtypes (Singer and others, 2008; Berger and others, 2008; 

John and others, 2010). Grade and tonnage distinctions of 

subtypes are discussed in the “Grade and Tonnage Models” 

section of this report.

Porphyry copper mineral deposit models used for the 

assessment include Singer and others (2008), Cox (1986a, 

b), Berger and others (2008), and John and others (2010). 

Porphyry copper characteristics and classification schemes 

discussed by Seedorff and others (2005) and the porphyry 

copper-gold model compiled by Geoscience Australia (2010) 

also were considered. In addition, porphyry copper models for Australia and western Pacific porphyry copper-gold 

deposits apply (Cooke and others, 1998; Sillitoe, 1997). 

These latter models are appropriate for many of the tectonic 

settings of Southeast Asia, where most porphyry copper deposits are Cenozoic, island-arc-related, copper-gold 

deposits unlike the copper-molybdenum-gold deposits in the 

southwestern United States or the Andes of South America. 

Conceptual exploration models for southwest Pacific Rim 

gold-copper systems, including porphyry copper deposits, 

are included in Corbett and Leach (1998).

For western Pacific porphyry deposits, copper-gold 

deposits typically are related to island arcs whereas coppermolybdenum deposits typically are related to continental 

margin arcs or cratons (Cooke and others, 1998). Intrusive 

rocks associated with many Cenozoic western Pacific porphyry deposits commonly have calc-alkaline to shoshonitic 

compositions, were emplaced at shallow (1 to 2 km) depths, 

have distinctive steep-sided, cylindrical form (“pencil 

porphyries”), and are spatially associated with diatremes, 

epithermal gold deposits, and if carbonate rocks are present, 

skarn deposits (fig. 2, table 1). As a result of the rapid uplift 

and high rates of erosion (tropical climate) in southeast Asia, 

coeval volcanic rocks and advanced argillic lithocaps are not 

always preserved. In southeast Asia, supergene enrichment 

zones tend to be absent or poorly developed compared with 

the deposits of the Andes and southwestern North America 

(Cooke and others, 1998). Supergene zones can develop 

depending on local topography, climate, and hydrology; the 

best example known in the study area is the oxide zone at 

the OK Tedi porphyry copper deposit in Papua New Guinea, 

which contains a 19 million metric tons (Mt) resource at 1.74 

percent copper and 1.34 grams per ton (g/t) gold (Rogerson 

and McKee, 1990).

Gold-rich porphyry copper deposits associated with 

alkaline (high-K) rocks, typically syenites, also are present 

in Southeast Asia. Characteristic settings for these deposits 

include emplacement in subduction-related oceanic arcs 

within, or along, calderas. Many deposits are localized at 

fault intersections. Associated rocks typically have elevated 

K2

O contents, are enriched in chlorine, fluorine, and light 

rare-earth elements, and have oxidized, magnetite-bearing 

magma sources (Müller and Groves, 1999). Gold-rich 
Porphyry Copper Assessment of Southeast Asia and Melanesia 7

porphyry copper deposits typically have abundant hydrothermal magnetite in copper- and gold-bearing potassic alteration zones; magnetite can be sufficiently abundant to cause 

“bull’s eye” magnetic-high anomalies (Sillitoe, 1997).

Fundamental Basis for Porphyry Copper 

Assessment

The fundamental geologic feature (unit) for delineation 

of a permissive tract for porphyry copper deposits, as derived 

from deposit models, is defined as a subduction-related magmatic arc or a postsubduction or collisional magmatic belt of 

a given age. Porphyry copper deposits form in hydrothermal 

systems that are spatially and temporally associated with apical, generally porphyro-aphanitic parts of felsic to intermediate stocks that were emplaced at shallow depths, typically less 

than 1 to 4 km.

Permissive tracts for porphyry copper deposits are delineated as geographic areas that include volcanic and intrusive 

rocks of a specified age range that typically can be related to 

a particular tectonic setting (such as a subduction-boundary 

zone). Tracts are based primarily on geologic map units 

that define the magmatic arc or belt. As a framework for the 

description of permissive tracts identified for the assessment 

of Southeast Asia, we briefly describe the tectonic setting of 

the major magmatic arcs and belts of the region.

Tectonic Setting

Southeast Asia and Melanesia host a variety of porphyry 

copper deposits, including world-class deposits, and deposits 

that principally are exploited for gold. Both subduction and 

postsubduction settings for porphyry deposits are recognized. 

The major magmatic arcs and magmatic belts that form the 

basis of this assessment are shown in figure 3 and listed in 

table 2. A complex series of both continental and island arcs 

developed in response to subduction and plate reorganization related to the geodynamic evolution of the borders of the 

Eurasian and Indian-Australian continents, the life cycle of 

seas in the region, and the movement of the Pacific Plate. This 

complex tectonic evolution has led to the development of a 

myriad of arc fragments, microcontinents, accreted terranes, 

and sea basins, many of which are of uncertain origin. Porphyry copper deposits and prospects in the study area range 

from Permian to Quaternary in age; most of the preserved 

porphyry copper mineralized systems are Miocene-Pliocene in 

age (fig. 4).

Pre-Cenozoic Settings.—The Indochina Peninsula is an 

assembly of micro-continental fragments that were sequentially accreted to Eurasia by the end of Mesozoic time. 

Metcalfe (2009) provides a particularly thorough discussion 

of the pre-Cenozoic evolution of Southeast Asia. We refer the 

reader to that paper and the figures therein for details. The 

continental terranes that make up today’s Indochina and South 

China originated as blocks that were rifted and dispersed from 

Gondwana (fig. 5A). This dispersion, as three elongate continental slivers, took place at three times, in the Devonian, in the 

Permian, and near the Triassic-Jurassic boundary. These rifting 

events marked, successively, the birth of the Paleo-Tethyan, 

Meso-Tethyan, and Ceno-Tethyan oceans. Igneous rocks were 

generated by subduction beneath and collision between all 

these continental fragments; the most important pre-Cenozoic 

arcs in Southeast Asia are the Sukhothai island-arc system and 

the Loei and Truong Son magmatic belts (fig. 3), all of which 

show evidence of porphyry copper-style mineralization and 

host porphyry copper deposits.

These pre-Cenozoic terranes have been translated, 

rotated, and deformed by the collision of the Indian subcontinent with Asia, beginning in earliest Cenozoic time and continuing to the Holocene (Metcalfe, 1999). This deformation 

has been largely accommodated by a giant dextral megashear 

zone (Ailoshan-Red River Fault Zone) that today forms the 

boundary between South China and Indochina (fig. 5A).

Cenozoic Settings.—Building on the work of Hamilton 

(1979) and Mitchell and Leach (1991), Garwin and others 

(2005) described the tectonic setting, geology and gold and 

copper deposits associated with 20 major Cenozoic magmatic arcs that form a >17,000 km-long volcano-plutonic 

chain extending from Japan southward to New Guinea, and 

west-northwest through Indonesia to Myanmar. The porphyrycopper-bearing magmatic arcs described by Garwin and others 

(2005) provided the geologic framework for most of the Cenozoic assessment areas.

Indochina Peninsula Area

Carboniferous and Permo-Triassic Arcs

Widespread Carboniferous through Late Triassic magmatic rocks in Southeast Asia have been assigned to a variety 

of named arcs. They are all related to the amalgamation of 

microcontinents that were rifted from Gondwana and drifted 

north due to subduction of the Paleotethyan ocean (Wakita and 

Metcalfe, 2005). We recognize three named arcs or belts that 

are described below.

Sukhothai Island-Arc System

The Sukhothai island-arc system (no. 3, fig. 3), as 

defined by Sone and Metcalfe (2008), is a single island arc, 

nearly 3,000 km long, that developed along the western margin of the Indochina terrane (fig. 5A) and was active from 

latest Carboniferous time through the Permian until the final 

amalgamation of Indochina in the Late Triassic (the Indosinian Orogeny). Today, it extends from southern Yunnan south 

through northern Lao People’s Democratic Republic16 and 

Thailand, where it disappears beneath the Gulf of Thailand 

16 The country commonly referred to as “Laos” is officially known as the 

Lao People’s Democratic Republic. Laos is used on figures in this report.
8 Porphyry Copper Assessment of Southeast Asia and Melanesia

near the Thai-Cambodia border. It likely is present below 

this shallow sea as it reappears in southernmost Thailand and 

Malaysia before disappearing once again into the Karimata Strait. Volcanic rocks of this arc mostly are andesitic 

in composition and the presence of volcanogenic massive 

sulfide deposits suggests that much of the volcanism was 

submarine. Some volcanic suites show chemical affinities 

with continental-arc rocks and the youngest rocks in the 

arc probably were emplaced on continental crust (Sone and 

Metcalfe, 2008).

Loei Magmatic Belt

To the east of the Sukhotai Arc system, the Loei magmatic 

belt (no. 1, fig. 3) has been defined by a 500-km-long varied suite 

of Permian and Triassic intrusive and volcanic rocks in northwestern Lao People’s Democratic Republic and northern Thailand (Royal Thai Government Department of Mineral Resources, 

2010). It is known for hosting base-metal deposits, including the 

Phu Thong Daeng and Phu Hin Lek Fai porphyry copper deposits 

and the Phu Lon copper-gold skarn deposit in Thailand (fig. 1).

Limestone

Granodiorite/monzonite

Quartz diorite - dacite porphyry

Diatreme

Intermediate argillic alteration

Advanced argillic alteration

Phyllic alteration

Potassic alteration

Hydrothermal breccia

Propylitic alteration

K

K K

K

K

Fault

EXPLANATION

Skarn

K

K

K K

K

K

K K

K K

K

K

K

K

K

K

K

K K

K

K

high sulfidation veins

and replacement breccias

low sulfidation

epithermal veins

and breccias

proximal Cu-Au-Fe skarn distal 

skarn

propylitic 

alteration

“lithocap”

Figure 2. Generalized model of western Pacific porphyry copper-gold deposits (based on Cooke and others, 

1998). See table 1 for explanation of terms.
Porphyry Copper Assessment of Southeast Asia and Melanesia 9

Deposits tend to occur in belts and clusters

Proximity to known deposits is a good exploration guide

Coeval volcanic and intrusive rocks indicate appropriate levels of exposure

Unmetamorphosed host rock

Cu-Au deposits in island arcs after arc reversals; postcollisional settings

Associated with oxidized, I-type, magnetite series, subvolcanic intrusions

Arc-parallel and arc-oblique fault intersections

Small (<1 km2

), steep-sided, cylindrical, vertically extensive stocks; margins of batholiths

Proximity to intrusions with phaneritic textures (<4 km)

Porphyritic diorite to quartz diorite to monzonite stocks

Hypabyssal intrusions in andesitic volcanic rocks

Roots of eroded stratovolcanoes

Association with skarns and epithermal deposits

Telescoped epithermal systems over porphyries

Diatreme breccias; intramineral intrusions

Significant structural control on magma emplacement and mineralization

Typically shallow (1–2 km) depth of emplacement

K-silicate (biotite, magnetite, orthoclase, quartz, anyhydrite, chalcopyrite, actinolite)

Propylitic (chlorite, epidote, calcite, pyrite, albite) 

Intermediate argillic [SCC] (sericite, chlorite, kaolinite or illite, pyrite, calcite)

Phyllic (sericite, quartz, pyrite)

Advanced argillic (alunite, kaolinite, pyrophyllite, quartz, dickite, gibbsite, pyrite, enargite, covellite)

Tourmaline absent 

Supergene zone typically <60 m thick due to climate controls; best preserved along ridge crests; may be welldeveloped (as much as 600 m thick) depending on local topography and hydrology

Calc-alkaline to high-K calc-alkaline to shoshonitic volcanic sequences

Magmatic 34S (~-3 to +1‰; magmatic 18O (~+4 to +10‰) to meteoric with alteration

Stream sediment and soil sampling: anomalous concentrations of Cu, Au, Mo, Ag, Zn, Pb, As, Sb, Hg, Te, Sn, S 

Skarns (Cu, Au, Fe)

High-sulfidation epithermal gold; "lithocaps" (masses of pyrite and vuggy silica in advanced argillic 

alteration zones above subvolcanic intrusions) 

Low-sulfidation epithermal gold-silver 

Table 1. General characteristics of porphyry copper deposits in Southeast Asia.

Associated deposit types

Geochemical guides

Regional-scale features

Local-scale features

Alteration

[Based on Cooke and others (1998), Corbett and Leach (1998), and John and others (2010)]

δ δ

Table 1. General characteristics of porphyry copper deposits in Southeast Asia.

[Based on Cooke and others (1998), Corbett and Leach (1998), and Johnand others (2010)] 
10 Porphyry Copper Assessment of Southeast Asia and Melanesia

Truong Son Magmatic Belt

Farther east, Permian to Triassic intermediate to felsic magmatism characterizes the Truong Son magmatic belt in the Lao 

People’s Democratic Republic and Vietnam (no. 2, fig. 3; Hoa 

and others, 2008). It is a 1,000-km-long continental-margin arc, 

characterized by calc-alkaline volcano-plutonic complexes that 

formed primarily between 270 and 250 Ma and by post-collision 

alkaline felsic volcano-plutonic complexes that formed primarily 

after 245 Ma. There are also a few peraluminous granites with 

ages between 260 and 245 Ma that are interpreted to mark the 

collision of Indochina with the South China-Vietnam block.

Jurassic and Cretaceous Arcs

In southernmost Vietnam and southeastern Cambodia, I-type 

Jurassic and Cretaceous magmatic rocks formed as a result of 

northwest-directed subduction of the Pacific Plate beneath Indochina (no. 4, fig. 3; Taylor and Hayes, 1983). The rocks have not 

been studied extensively, although Thuy and others (2004) report 

that the rocks in Vietnam are metaluminous I-type granitoids that 

vary in composition from about 56 to 76 percent silica. This area 

is part of the larger Pacific margin arc of southeastern China.

Tertiary Arcs

Wuntho-Popa Arc

The Pliocene to Quaternary Wuntho-Popa magmatic arc 

(no. 5, fig. 3) includes an onshore portion that extends for 1,200 

km from Wuntho State in northern Myanmar through Mount 

Popa in southern Myanmar, and a southward offshore extension 

along a chain of islands in the Andaman Sea (figs. 3 and 5). This 

magmatic arc is a northern extension of the Sunda Arc, but the 

Wuntho-Popa Arc separated from it by strike-slip displacement 

and subsequent extension beneath the Andaman Sea. The Wuntho-Popa magmatic arc is related to northeast-directed oblique 

subduction of the Indian subcontinent and the Indian Ocean Plate 

beneath Indochina along the Sunda Trench (Mitchell, 1993; Curray, 2005; Chandrasekharam and others, 2009). Today, this relative movement is largely accommodated by the dextral strike-slip 

Sagaing Fault system (fig. 5A) that marks the boundary between 

the West Burma continental block to the west and the Sibumasu 

terrane (see Sone and Metcalfe, 2008, fig. 3; Hutchison, 1989). 

The onshore portion of the arc is primarily mafic calc-alkaline 

(Mitchell and others, 2008) to high-K calc-alkaline rocks (Maury 

and others, 2004), while the offshore subsea portion is mostly 

tholeiitic (Hutchison, 1989). A few alkaline to shoshonitic rocks 

occur about 100 km to the east of the calc-alkaline arc along the 

east side of the Sagaing Fault.

Western Indonesian Islands Area

Tertiary Arcs

Sunda-Banda Arc

The Eocene to Holocene Sunda-Banda Arc (no. 6, 

fig.3) that extends 4,000 km from northwestern Sumatra to 

Java through the Banda Island group of eastern Indonesia is 

related to subduction of oceanic crust along the Sunda-Banda 

Trench system (fig. 5B,C). The basement to the arc varies 

from Eurasian continental crust with Mesozoic to late Paleozoic platform sedimentary rocks intruded by Cretaceous 

two-mica granites in Sumatra in the eastern segment of the 

arc, Cretaceous to Cenozoic melange and ophiolite in Java in 

the central portion of the arc, to oceanic crust in the western 

Banda Arc portion of the arc (Hamilton, 1979). Porphyry 

copper mineralization in the Sunda-Banda Arc, mostly late 

Eocene to Pliocene age, generally is associated with bodies 

of andesite porphyry, dacite porphyry, and tonalite porphyry. 

This calc-alkaline magmatism declined in the early Miocene, 

followed by erosion and widespread deposition of sedimentary rocks. In the late Miocene to Pliocene, collision of the 

Australian continent with the western segment of the SundaBanda Arc shut off subduction along the Timor Trench and 

initiated a polarity shift to southward subduction of oceanic 

crust of the marginal Banda Sea beneath the arc (Garwin and 

others, 2005).

Ambon Arc

The Pliocene-Quaternary Ambon Arc in the Moluccan Islands (no. 9, fig. 3), extends from Ambelau Island 

across western Seram and Ambon Island (fig 5C) to the 

small islands of the Banda Archipelago. The Ambon Arc 

and the Moluccan Islands are located east of Sulawesi, west 

of New Guinea, and north of Timor, near the intersection of 

the Indo-Australian, Pacific, and Eurasian Plates (fig. 5B). 

Collision of the Australian continent with the western segment of the Sunda-Banda Arc in the late Miocene to Pliocene shut off subduction along the Timor Trench, initiating 

plate reorganization and southward subduction of Irian Jaya 

continental crust beneath Seram along the Seram Trough 

(McCaffrey, 1988). Honthaas and others (1999) separate the 

Ambon Arc from the Sunda-Banda Arc based on geochemical differences in their Pliocene and younger volcanic rocks 

and differences in the subduction settings of the arcs. The 

Ambon Arc consists of two suites of island-arc magmas. 

These are (1) Pliocene low-K calc-alkaline volcanic rocks 

(basalts, andesites, dacites, rhyolites) related to mantle melting above the subducting Irian Jaya Plate; and (2) Pleistocene high-K calc-alkaline andesite, dacites, rhyolites, and 

granites formed by assimilation of continental crust (Whitford and Kezek, 1979).

Halmahera Arc

The Miocene to Holocene Halmahera Arc (no. 10, 

fig. 3) sweeps north across the western arm of the Halmahera Islands and includes Morotai, Halmahera, Bacan, and 

Obi Islands (fig 5C). The arc system extends 400 km from 

near the Philippine Trench to the western extension of the 

Sorong Fault (fig. 5B). The basement to the arc consists 

primarily of Cretaceous-Paleocene ophiolite in Halmahera, 

Bacan, and Obi (Hall and others, 1991), although there 
Porphyry Copper Assessment of Southeast Asia and Melanesia 11

Map

key

Magmatic

arcs and belts Age range

Arc

Length

in km

Arc /crust type Key reference

1 Loei magmatic belt Permian to Triassic 900 oceanic and continental Boonsoong and others (2011)

2 Truong Son magmatic belt Permian to Triassic 1,000 oceanic and continental Hoa and others (2008)

3 Sukhothai Arc system Carboniferous to Triassic 1,700 oceanic and continental Sone and Metcalfe (2008)

4 South Indochina Arcs Jurassic to Cretaceous 700 continental Mitchell and others (2008)

5 Wuntho-Popa Arc Miocene to Holocene 1,200 continental Garwin and others (2005)

6 Sunda-Banda Arc Eocene to Holocene 3,800 oceanic (E); continental (W) Garwin and others (2005)

7 Central Kalimantan magmatic belt Eocene(?) to Miocene 1,200 continental Garwin and others (2005)

8 Sulawesi-Sangihe Arc Miocene to Pliocene 1,200 oceanic (NE); continental (SW) Garwin and others (2005)

9 Ambon Arc Pliocene to Quaternary 300 oceanic Honthaas and others (1999)

10 Halmahera Arc Neogene to Holocene 400 oceanic (N); continental (S) Garwin and others (2005)

11 Maramuni Arc Miocene 1,000 continental and accreted oceanic Garwin and others (2005)

12 Moon-Utawa Arc Miocene 200 continental? Carlile and Mitchell (1994)

13 Medial New Guinea magmatic belt Late Miocene to PliocenePleistocene1,800 continental; postcollisional Garwin and others (2005)

14 Inner Melanesian Arc* Late Oligocene to Holocene 1,000 oceanic Garwin and others (2005)

15 Outer Melanesian Arc Eocene to Holocene; Pliocene 

to Holocene

 >800 oceanic Garwin and others (2005)

16 Sulu-Zamboanga Arc Miocene to Holocene 400 oceanic (NE); continental (SW) Garwin and others (2005)

Table 2. Principal magmatic arcs of Southeast Asia and Melanesia.

[Map key for figure 3; arcs and belts based primarily on Garwin and others (2005); *, Inner Melanesian arc extended across northern New Guinea Island to 

include accreted terranes; km, kilometers]

are Mesozoic and probable Precambrian gneiss and schist 

exposed on Bacan Island (Hamilton, 1979; Malaihollo and 

Hall, 1996). The Halmahera Island region has a long history 

of magmatic activity. The ophiolitic basement was formed 

in an intra-oceanic arc (Ballantyne, 1992) and it is overlain 

in Halmahera and Obi Islands by products of a Late Cretaceous arc and in Halmahera, Bacan, and Obi by an Eocene 

to Oligocene arc (Hall and others, 1988a,b; Ali and Hall, 

1995; Malaihollo and Hall, 1996). These arcs formed as the 

result of subduction at the margin of the Philippine Sea Plate 

in an intra-oceanic setting. Arc magmatism was terminated 

between the late Oligocene and early Miocene by collision 

with the north Australian margin (Hall, 1996). During the 

middle Miocene, there was little or no magmatic activity 

and marine platform carbonates were deposited over a large 

area. Arc magmatism resumed in the late middle Miocene. 

All these rocks form the basement to the Neogene Halmahera 

Arc, which has been active since about 11 Ma between Obi 

in the south and Morotai at the north end of the island chain 

(Baker and Malaihollo, 1996). The active arc rocks have 

geochemical data indicating a oceanic-arc chemistry in north 

and central Halmahera (Morris and others, 1983); continental 

crust contribution is present in the Neogene lavas on Bacan 

(Hakimand and Hall, 1991). These data are consistent with 

movement of Australian continental fragments along strands 

of the Sorong Fault, as first suggested by Hamilton (1979).

Sulawesi-Sangihe Arc

The Miocene to Holocene Sulawesi-Sangihe magmatic 

arc (no. 8, fig. 3) extends more than 1,200 km from north 

of Sangihe Island southward through the northern arm of 

Sulawesi, west along the neck of Sulawesi, and continues 

south along the west arm of Sulawesi, ending in small volcanic islands north of Flores (fig. 5B).

The western portion of the arc overlies Sundaland 

(Eurasian) continental crust (fig. 5B) and Cretaceous to 

Eocene metamorphic rocks, which are intruded by late 

Miocene to Pliocene granitoids (Kavalieris and others, 

1992). These rocks are overlain unconformably by Eocene 

to Oligocene submarine basalt, andesite, and sedimentary 

rocks that form part of an oceanic arc extending east along 

the North Arm of Sulawesi (Carlile and others, 1990; Kavalieris and others, 1992). Geochemical and isotopic data 

from northwestern Sulawesi support the inferred transition 

from continental- to oceanic-arc settings from west to east 

and indicate the presence of an underthrust fragment of the 

Australian continent that extends from the western edge 

of North Sulawesi through the northern and central parts 

of west Sulawesi (Elburg and others, 2003). The early to 

middle Miocene portion of the arc consists of andesitic to 

dacitic volcanic and volcaniclastic rocks and sedimentary 

rocks intruded by diorite, quartz diorite, granodiorite, and 
12 Porphyry Copper Assessment of Southeast Asia and Melanesia

Figure 3. Map of the principal magmatic arcs of Southeast Asia and Melanesia. Arcs that continue north into the 

Philippines are shown in gray. See table 2 for map key and references.

100° E 130° E 

20° N

0°

20° S

6

4

7

8

2 3

5

1

3

16

10

9 

12

INDIA

MYANMAR

CHINA

CHINA

(TAIWAN)

CHINA

(HAINAN)

VIETNAM

LAOS

THAILAND

CAMBODIA

PHILIPPINES

MALAYSIA

MALAYSIA

INDONESIA

INDONESIA

AUSTRALIA

SINGAPORE

Andaman Sea South China Sea

INDIAN OCEAN

Java Sea

 Timor Sea

Ara

 Banda Sea

Karimata Strait

Celebes Sea

Gulf

 of

Thailand

0 500 1,000 KILOMETERS

0 250 500 MILES

Political boundary source U.S. Department of State (2009)

Projection: Asia South Albers Equal Area Conic;

Central meridian 115° E; latitude of origin 15° S
Porphyry Copper Assessment of Southeast Asia and Melanesia 13

160° E

15

15

13

15

11

14

12

14

INDONESIA

PAPUA

NEW GUINEA SOLOMON

ISLANDS

VANUATU

FIJI

 NORTH PACIFIC OCEAN

SOUTH PACIFIC OCEAN

 Coral Sea

afura Sea
14 Porphyry Copper Assessment of Southeast Asia and Melanesia

their subvolcanic porphyritic equivalents (Carlile and others, 1990; Kavalieris and others, 1992). Quaternary andesitic stratovolcanoes define the arc from north Sulawesi 

through Sangihe Island (fig. 5B). Major northwest-striking 

faults influenced the distribution of volcanic and sedimentary rock successions in north Sulawesi. The movement along these faults is oblique-slip, with arc-parallel 

extension indicated by the progressive down-to-the north 

movement of the fault blocks in north Sulawesi (Carlile and 

others, 1990).

Central Kalimantan Magmatic Belt

The Late Oligocene to Pliocene Central Kalimantan 

magmatic belt (no. 7, fig. 3; Carlile and Mitchell, 1994) 

extends approximately 1,200 km from western Sarawak, 

northeast through central Kalimantan, into Sabah where it 

merges to the northeast with the western onshore extension 

of the Neogene Sulu-Zamboanga Arc of the Philippines (no. 

16, fig. 3) in the Semporna peninsula of Sabah (fig. 5B). 

The arc is defined by the discontinuous distribution of calcalkaline andesitic, trachyandesitic, and dacitic volcanoplutonic centers, mapped as the Sintang intrusive suite in 

western Kalimantan and the Long Lai intrusive suite in 

northeastern Kalimantan (Carlile and Mitchell, 1994).

The continental basement to the arc consists of 

Paleozoic metasedimentary rocks intruded by Triassic to 

Carboniferous and Cretaceous (Schwaner Massif) granites 

in western Kalimantan (Hamilton, 1979; Hutchison, 1989); 

Late Cretaceous to Paleogene ophiolite, metasedimentary, 

and volcanic rocks comprise the basement to the arc in 

eastern Kalimantan and Sabah. The northwest-striking arctransverse Kinabalu Fault system (fig. 5B), that parallels 

the Late Cretaceous to Paleogene ophiolite belt in Sabah, 

has localized intrusive centers and dikes of the magmatic 

arc.

The late Oligocene to Pliocene igneous rocks in the 

belt overlap and postdate folding, thrusting, uplift, and 

erosion of pre-Miocene rocks and continental basement 

in Kalimantan (Hutchison, 2005; Moss and others, 

1998). This tectonic-magmatic event resulted in about 

1–2 km of exhumation from 25 to 23 Ma, an eastward 

shift of basin sedimentation (Moss and others, 1998), 

and a northeastward shift in magmatic activity. This 

deformation, uplift, and rapid erosion is interpreted to 

record a collision between the extended passive continental 

margin of South China that underthrust the northern 

part of the Eurasian Sundaland continental margin in 

Borneo and ended Cretaceous to Paleogene subduction 

of the proto-South China Sea (Hutchison, 2005; Hall and 

Wilson, 2000). The relationship of this late Oligocene to 

Pliocene magmatic arc to subduction is unclear, but the arc 

may be related to tectonic reactivation of melting in the 

Cretaceous-Paleogene subducted slab. The tectonic setting 

for the porphyry copper deposits that occur in this tract is 

consistent with the postsubduction porphyry copper-gold 

model described by Richards (2009).

New Guinea Island, Indonesia and Papua New 

Guinea

The eastern half of the island of New Guinea is the 

independent country of Papua New Guinea. The western 

half of the island includes the Indonesian provinces of Papua 

and West Papua, formerly known as Irian Jaya. The regional 

tectonic setting of the island is shown in figure 6. The shape of 

the island, that of a westward-flying bird, is used to describe 

various parts of the island (Quarles van Offord and Cloos, 

2005). The Bird’s Head forms the northwesternmost promontory of the island (fig. 7). The southeasternmost part of the 

island, the Papuan New Guinea Peninsula, is called the Bird’s 

Tail. The present-day island formed as a result of complex 

island arc-continent collisions during the Cenozoic. Four 

major east-west-trending structural belts define the central part 

of the island known as the Bird’s Body. These belts originally 

were defined by Dow (1977) and Hamilton (1979), refined 

by various workers, and summarized in Hill and Hall (2003) 

and Quarles van Ufford and Cloos (2005). The belts (fig. 7), 

from north to south, are (1) Paleogene accreted island arcs and 

oceanic terranes; (2) the Mobile Belt, which includes Miocene 

intrusive and volcanic rocks; (3) the Fold Belt, Australian continental crust that was deformed during from late Miocene to 

the Holocene after the late Oligocene-Miocene continent-arc 

collision; and (4) the Stable Platform (Fly platform), underlain 

by Australian continental crust (Hill and Hall, 2003).

Paleogene Arcs

Inner Melanesian Arc

Southwestward subduction of the Pacific Plate in the 

Eocene to early Oligocene formed the Inner Melanesian calcalkaline arc (no. 14, fig. 3). Segments of the arc that extends 

for more than 1,000 km include accreted Paleogene island arcs 

preserved along northern New Guinea Island in the Gauttier 

terrane, Cyclops Mountains, Bewani-Torricelli Mountains, and 

Adelbert and Finisterre Ranges (fig. 7), as well as Eocene to 

early Oligocene igneous rocks on New Britain Island (fig. 7). 

Late Oligocene to early Miocene plate reorganization occurred 

about 25 Ma, when New Britain was situated at the intersection of the South Caroline and Melanesian Arcs (Garwin and 

others, 2005). The accreted arcs on New Guinea Island are 

poorly understood but may represent remnants of the Philippine Sea Plate that were fragmented by strike-slip faulting 

since 25 Ma (Ali and Hall, 1995). During the mid- to late Miocene, jamming of the Melanesian Trench by collision of the 

Cretaceous Ontong Java oceanic plateau17 (fig. 6) led to a cessation of arc magmatism and changes in subduction polarity.

The Inner Melanesian Arc hosts porphyry copper deposits 

on New Britain, but no deposits are known in the accreted 

17 The 1,900,000 square kilometer (km2

) Ontong Java Plateau, which represents the largest and thickest oceanic plateau on Earth, is interpreted as the 

surface location of the head of a mantle plume (Mann and Taira, 2004).
Porphyry Copper Assessment of Southeast Asia and Melanesia 15

Age, in millions of years

0 50 100 150 200 250 300

Number of deposits and prospects

0

5

10

15

20

25

A

Age, in millions of years

0 5 10 15 20 25 30

Number of deposits and prospects

0

2

4

6

8

B

Oligocene Miocene

Pliocene

Figure 4. Chart of the age distribution of dated porphyry copper deposits and prospects in Southeast 

Asia. A, Time span for all dated deposits and prospects. B, Cenozoic Era.
Figure 5. Map showing the regional tectonic setting of the Indochina Peninsula and western Indonesia. A, Continental blocks, Gondwana-derived terranes, a

china Peninsula area. LT, Lincang terrane; ST, Sukhothai terrane; CT, Chanthburi terrane. Based on Metcalfe (2009). B, Present-day extent of Eurasian and Austrafter Garwin and others (2005). ID, Indonesia; LA, Lao People’s Democratic Republic; KH, Cambodia; MY, Myanmar; VN, Vietnam; PH, Philippines. C, Islands of wsia.

5° S

0°

5° N

10° N15° N20° N25° N

85° E 90° E 95° E 100° E 105° E 110° E 115° E 120° E

Projection: Asia South Albers Equal Area Conic;Central meridian 103° E, Latitude of origin 20° 0 500 1,000 KILOMETERS

0 250 500 MILES

Dhaka

Ramgoon

Vientiane

Bangkok

Phnom Penh

Kuala Lumpur

Singapore

Jakarta

AILAOSHAN-RED RIVER FAULT ZONE

SOUTH CHINA

INDIA

SOUTH CHINA SEA

Andaman Sea

INDIAN OCEAN Java Sea

STLT

CT

WEST MYANMAR

INDOCHINA

EAST MALAYSIA

SIBUMASU

ACTIVE TRENCH BENTONG-RAUB

FAULT

SAGAING

FAULT

EXPLAN

FTGTiIGT T

WEST SUMATRA BLOCK

A
Figure 5.—Continued

LA

MYANMAR

KINABALU 

FAULT

HALMAHERA

ARC

CN

Sangihe

Andaman

Sea

Java Sea

100°E 110°E 120°E 130°E

20°N10°N

0°

10°S

Political boundary source U.S. Department of State (2009)Projection: Asia South Albers Equal Area Conic;Central meridian 115° E; latitude of origin 15° S

0 250 500 750 1,000 KILOMETERS0 250 500 MILES

( (

(

Bali

MOLUCCA SEA PLATE

THAILAND

KH

AUSTRALIA

TIMOR TROUGH SUNDA TRENCH

SORONG

FAULT

VN

MY

MY

ID

ID

PH

PH

ID

SOUTH CHINA SEA

NORTH PACIFIC OCEAN

Celebes Sea

Banda Sea

INDIAN OCEAN Arafura Sea

Timor Sea

Makassar Straits

Borneo

Sarawak

Kalimantan

Sabah

Semporna Peninsula

Flores

Java

Central Kalimantan Magmatic

Belt

SULAWESISANGIHE ARC

PHILIPPINE SEA PLATE

CAROLINE

PLATE

INDIAN OCEAN PLATE

Sumatra

SUMATRAN FAULT

SUNDA BANDA ARC

A

B
Figure 5.—Continued

105° E 120° E

0°

10° S

THAILAND

MALAYSIA

MALAYSIA

BRUNEI 

INDONESIA

INDONESIA

PHILIPPINES

TIM

SINGAPORE

Sumatra

Borneo

Mindinao

Sulawesi

Sula

Java

Madura

Bali

Lombok

Sumbawa

Sumba

Flores

Pulau Siberut

Pulau Nias

Pulau Banka

Billiton

Buru

Hal

Kepulaua

Timor

Ambelau 

Bacan

Wetar

Damar South China Sea

Andaman Sea

 Sulu Sea Celebes Sea 

Molucca Sea

Java Sea Banda 

T

INDIAN OCEAN

0 250 500 750 1,000 KILOMETERS0 125 250 375 500 MILES

Political boundary source: U.S. Department of State (2009)Projection: Asia South Albers Equal Area ConicCentral meridian 115° E; latitude of origin 15° S

C
Porphyry Copper Assessment of Southeast Asia and Melanesia 19

Precambrian basement Paleozoic basement

PHILIPPINE

SEA

PLATE

CAROLINE

PLATE

INDO-AUSTRALIAN 

PLATE

PACIFIC

PLATE

AUSTRALIA

NEW

CALEDONIA

SAMOA

NEW

ZEALAND

PHILIPPINES

FJ

New Guinea

VU

SB

Tasman Line

WOODLARK

BASIN

LORD

HOWE

RISE

ONTONG

JAVA

PLATEAU

SOUTH

FIJI BASIN

NORTH

FIJI BASIN

Coral Sea

Tasman Sea

Banda Sea

Celebes

Sea

Bismarck Sea

NORTH PACIFIC OCEAN

CAROLINE RIDGE

LAU RIDGELAU

BASIN

VITIAZ TRENCH

TONGA-KERMADEC ARC

SAN

CRISTOBAL TRENCH

VANUATU TRENCH

SOLOMON TRENCH

AYU

TROUGH

140°E

30°S

0°

170°E

0 250 500 KILOMETERS

0 250 MILES

Figure 6. Map showing the regional tectonic setting of eastern Indonesia and Papua New Guinea (after Hill 

and Hall, 2003). Areas in light blue indicate continental shelf areas of Australia and Eurasia, areas of thickened 

oceanic crust, and arcs. Barbed lines represent active modern subduction zones. SB, Solomon Islands; VU, 

Vanuatu; FJ, Fiji. The Tasman Line marks the approximate boundary between basement of Precambrian continental crust of the Australian craton to the west and Paleozoic continental crust to the east.
20 Porphyry Copper Assessment of Southeast Asia and Melanesia

terranes on New Guinea Island. The Ramu-Markham Fault in 

Papua New Guinea (fig. 8), a seismically active mid-crustal 

detachment, represents the suture between the Finisterre 

accreted island arc terrane and basement rocks of Australian 

origin. The fault connects offshore with the New Britain 

Trench (Stevens and others, 1998). In New Britain, subduction-related arc magmatism began again in the Pliocene and 

continues to the present.

Miocene Arcs

Maramuni Arc of Papua New Guinea

The calc-alkaline igneous suite of rocks that define 

the Miocene Maramuni Arc extends for 1,000 km along the 

southwestern margin of the New Guinea Mobile Belt (fig. 

7). The Maramuni Arc probably formed due to subduction 

of the Solomon Sea under eastern New Guinea following a 

southward jump in subduction from the Melanesian Trench 

to the Maramuni Trench. The change in subduction likely 

was related to early to mid-Miocene collision of the Ontong 

Java Plateau with the Melanesian Arc (fig. 6). Quarles van 

Ufford and Cloos (2005) describe the Maramuni Arc forming 

as a result of subduction from 20 to 10 Ma along northeastern 

New Guinea. The arc was emplaced into Australian continental crust in Papua New Guinea. According to Quarles van 

Ufford and Cloos (2005), Maramuni Arc magmatism occurred 

between two major Cenozoic collisional orogenic events: (1) 

the Oligocene Peninsular Orogeny, recognized only in the Papuan peninsula, and (2) the Central Range Orogeny that began 

in middle Miocene time. The mobile belt is separated from the 

accreted arcs to the north by left-lateral strike-slip faults that 

include the Ramu-Markham Fault Zone in Papua New Guinea 

and the Sorong Fault system in Indonesia. The Sorong Fault, 

a left-lateral megashear, marks the boundary between continental crust related to Australia to the south and volcanic arcs 

and oceanic crust of the Molucca Sea Plate, Philippine Sea 

Plate, and Caroline Plates to the north (fig. 5B). To the south 

of Halmahera, the Sorong Fault splits into several splays that 

formed since the Pliocene (Hall and Wilson, 2000).

Late Miocene Melanesian Arc collision caused regional 

uplift of northern Papua New Guinea; exhumation of the 

Maramuni Arc (3–4 km) exposed mid-Miocene batholiths. 

Late Miocene porphyry copper-gold systems, such as Yandera, 

are localized along the margins of the exposed batholiths (Garwin and others, 2005).

Miocene Rocks of Western New Guinea Island, Indonesia

Igneous rocks of Maramuni age are present to the west of 

the international border in the Bird’s Head (Moon Arc), at the 

base of the Bird’s Neck along the southern margin of Cenderawasih Bay (Utawa Arc), and in the western part of the Bird’s 

Body in the Ular Merah district in the Central Ophiolite Belt 

(Jackson, 2010) (fig. 7). Carlile and Mitchell (1994) proposed the name Moon-Utawa Arc for the mid-Miocene Moon 

Volcanics of the northern part of the Bird’s Head and the 

mid-Miocene Utawa Diorite of the Bird’s Neck. Garwin and 

others (2005) noted that although there is igneous activity in 

this region, the relation of the arc to a subduction zone is not 

clear. The Miocene rocks may have formed in a north-facing 

arc along a passive continental margin prior to south-directed 

thrusting in the Late Miocene (Melanesian orogeny) that 

displaced the Utawa Diorite to the south along the Weyland 

thrust (Carlile and Mitchell, 1994; Dow and Robinson, 1985). 

The Moon Volcanics may be linked to the Maramuni Arc, 

but as noted by Malaihollo and Hall (1996), the nature and 

distribution of the volcanism and its relation to the Maramuni 

rocks remains unclear. The Miocene igneous rocks in western 

New Guinea lie within allochthonous arc/forearc terranes and 

may have originated much farther (>500 km) northeast of their 

present location (Cloos and others, 2005). The Bird’s Head 

block, or microplate, represents a recent escape tectonic zone 

formed by convergence of the Australian Plate with volcanic 

arcs (Pubellier and Ego, 2002).

The Miocene age of the igneous rocks in the Ular Merah 

area was only recently established by Jackson (2010). She 

showed that the 11 mid-Miocene intrusions at Ular Merah 

are adakitic in composition with an asthenospheric mantle 

component and are chemically distinct from coeval rocks in 

Papua New Guinea (Maramuni Arc) and from Pliocene rocks 

in the Medial New Guinea Magmatic Belt. She proposed that 

they formed due to mid-Miocene spreading in the Ayu Trough 

(fig. 6), an intraoceanic rift system that marks the southeastern 

boundary between the Philippine and Caroline Plates, prior 

to left-lateral fault displacement of the Ayu Trough during 

the past 4 million years. The relationship of these rocks to the 

Moon-Utawa area, if any, is unclear.

Late Miocene to Pliocene Magmatism

Medial New Guinea Magmatic Belt

The approximately 1,800-km-long late Miocene to Pliocene medial New Guinea magmatic belt runs along the central 

highlands of New Guinea within the Papuan Fold Belt (fig. 7). 

The belt includes mantle-derived, high-K calc-alkaline to alkaline intrusions associated with world-class porphyry copper 

deposits (Grasberg, Ok Tedi). Extreme uplift and erosion rates 

of about 1–2 mm per year since mid-Pliocene may explain the 

absence of coeval volcanic rocks in the western part of the belt 

(Weiland and Cloos, 1996). Intrusion emplacement was structurally controlled along margins of basement uplifts and northnortheast-trending lineaments that parallel basement structural 

trends and mark boundaries between different structural 

domains (Garwin and others, 2005). Intrusions are not directly 

related to subduction; they occur along local dilational zones 

formed at intersections of strike-parallel (generally east-west) 

crustal extensional faults and long-lived, strike-perpendicular 

crustal transfer structures/lineaments (Hill and others, 2002). 

The western part of the fold belt in Irian Jaya is characterized 

by high mountains (~5 km) and basement thrusts; thin-skinned 

folding and thrusting characterize the eastern part of the fold 

belt in Papua New Guinea, where elevations typically are 
Tosem Block

FORELAND BASIN

MAPENDUMA FAULT

LF

SB

ST

BB

WT

COB

MB

G

DF

CM

LFB

RB

AR

FR

HP

B-T

FHP

Po

GM

Accreted ‘arcs’

April ultramafics

Marum Ophiolite

Miocene igneous rocks

(Maramuni Arc 

mainly 10-20 Ma)

Papuan ultramafic belt

IRIAN JAYA

PAPUA NEW

GUINEA

Bird’sHead

KEMUM

TERRANE

Cenderawasih

Bay

ARAFURA

PLATFORM

NORTH PACIFIC OCEAN

Arafura Sea

New 

FOLD BELT

STABLE

 PLATFORM

MOBILE BELT 

Manus Island

0 300 KILOMETERS

0 125 MILES

132° E 140° E 148° E

0°

4° S8° S

Figure 7. Map of tectonic belts of New Guinea Island, Indonesia and Papua New Guinea (after Hill and Hall, 2003). Different colors represent dielements: yellow, basins; green, Papuan fold and thrust belt; dark blue, ophiolites and ultramafic rocks; red, Miocene igneous rocks; brown, accrGuinea Island. AR, Adelbert Ranges; BB, Bintuni Basin; B-T, Bewani-Torricelli Mountains; CM, Cyclops Mountains; COB, Central Ophiolite Belt; DFly-Highlands province; FR, Finisterre Ranges; G, Gauttier terrane; GM, Grasberg Mine; HP, Huon Peninsula; LF, Lagaip Fault (N limit of foreland foLFB, Lengguru Foldbelt; MB, Meervlakte Basin; Po, Porgera intrusive complex and mine; RB, Ramu Basin; SB, Sepik Basin; ST, Sepik terrane; WT
22 Porphyry Copper Assessment of Southeast Asia and Melanesia

2–3 km. This implies that deeper crustal levels are exposed in 

the western part of the belt.

Papua New Guinea and Melanesia

Late Miocene to Pliocene Magmatism

Outer Melanesian Arc

The Eocene to Holocene Outer Melanesian Arc forms 

a curvilinear belt of islands that extend more than 800 km in 

Papua New Guinea from Manus Island in the north, through 

New Ireland, the Bismarck Archipelago (Tabir, Feni, and 

Lihir), to Bougainville (fig. 8). The extended arc system 

continues to the south to Fiji as a series of arc segments, which 

include the Solomon Arc, the Vanuatu (New Hebrides) Arc, 

the relict Vitiaz Arc, and the arc and rift stages preserved in 

Fiji. When the Ontong Java Plateau first reached the Solomon 

segment of the Vitiaz Trench system at about 22 Ma, it was 

too thick to subduct, which led to cessation of subduction 

along the Vitiaz Trench and arc segmentation and rotation of 

arc segments.

Papua New Guinea. The northernmost islands of the 

Outer Melanesian Arc, Manus and New Ireland, host Miocene 

porphyry copper prospects. In the early Pliocene, subduction 

polarity reversed as northeasterly-directed subduction of the 

New Britain slab began beneath the Inner and Outer Melanesian Arcs. The strike and dip of the subducting New Britain 

slab varies throughout the Melanesian Arcs, as does the age 

and character of the magmatism. Bougainville hosts Pliocene 

deposits associated with calc-alkaline diorite to granodiorite 

stocks. The islands of the Bismarck Archipelago, which lie 

about 400 km above the subducting New Britain slab, represent a series of uplifted and eroded Pliocene to Holocene 

stratovolcanoes that have a shoshonitic geochemical signature 

interpreted as reflecting a contribution from subducted mantle 

material (Garwin and others, 2005). Lindley (2006) noted that 

major, generally north-trending, structural corridors localized 

the emplacement of mineralized Tertiary intrusive rocks in 

New Britain, New Ireland, and Manus Island. These structural 

corridors (fault zones, aligned intrusions) are oblique to major 

morphotectonic features, such as the New Britain Trench. 

High-angle structures predominate in the region, resulting in 

vertical uplift of crustal blocks such as the north-trending horst 

blocks that comprise the basement in the New Ireland offshore 

island chain (Lindley, 2006; Garwin and others, 2005).

Melanesia (Solomon Islands-Vanuatu-Fiji) Paleogene to 

Holocene tectonic interactions between the Pacific and IndoAustralian Plate led to formation, fragmentation, and reconfiguration of a series of magmatic arcs that are variably preserved 

in the Melanesian island nations of Oceania (Solomon Islands, 

Vanuatu, and Fiji). A complex system of trench-bounded arcs 

extends from the easternmost islands of Papua New Guinea 

southward through the Solomon Islands and Vanuatu (New 

Hebrides Islands) to Fiji and the Tonga-Kermadec Arc (fig. 6). 

The arc system developed in Eocene-Oligocene time owing 

to southwest-directed subduction of the Pacific Plate beneath 

the Australian Plate along the Vitiaz Trench system (fig. 9A). 

From the early Eocene to middle Miocene, the Solomon 

Islands, Vanuatu, Fiji, and the Tonga Islands were all part 

of a continuous arc (Vitiaz Arc, also referred to as Northern 

Melanesian Arc, or stage 1 arc of Petterson and others, 1999). 

West-dipping subduction of the Pacific Plate occurred along 

the Vitiaz Trench (Begg and Gray, 2002). The early arc stage 

(35–12 Ma) is recorded in the Solomon Islands, in the western 

belt of Vanuatu, and on Viti Levu, the main island of Fiji.

Collision of the Ontong Java Plateau (fig. 9B) with the 

Solomon topographic block shut down the Vitiaz subduction 

zone and initiated an arc polarity reversal along the Vanuatu 

Arc segment northwest of Fiji as a new east-dipping trench 

system developed west of the Solomon Islands and west of 

the Vanuatu Arc at about 8 Ma (Mann and Taira, 2004; Begg 

and Gray, 2002). The exact timing and nature of the collision 

are not well-established. The initial collision in the Solomon 

Islands may have occurred as early as 25–20 Ma as a “softdocking event” that was sufficient to start the polarity reversal 

at 12–6 Ma. The main “hard” collision recorded in deformation in the Solomon Islands is placed at about 5 Ma or younger 

(Petterson and others, 1999). The modern Solomon Islands are 

bounded on the north by the North Solomon Trench system 

and on the south by the New Britain-San Cristobal Trench 

(fig. 6). The Ontong Java Plateau is converging on the North 

Solomon Trench at an oblique angle at a rate of 10 cm/yr 

(Phinney and others, 2004).

Paleocene/Eocene to early Miocene magmatism and associated hydrothermal activity in the arc system is related to the 

Vitiaz subduction. Late Miocene-Pleistocene arc magmatism 

in Vanuatu (stage 2 of Petterson and others, 1999) is related 

to northeast-dipping subduction of the Australian Plate along 

the San Cristobal-Vanuatu Trench system (fig. 9B). Major 

tectonic reorganization of the Vitiaz Arc system occurred after 

8 Ma. Following the reversal in subduction polarity in the late 

Miocene (8.0–5.5 Ma), the arc fragmented north of Fiji as 

the North Fiji Basin (fig. 9B) opened by back-arc spreading 

with clockwise rotation of the Vanuatu Arc to the southwest, 

translation and clockwise rotation of the Tonga Arc, and 

counterclockwise rotation of the Fiji Platform. The east-west, 

left-lateral Fiji transform fault borders the Fiji platform on the 

north (fig. 9C). Intra-arc extension behind the Tonga Trench at 

about 5.5 Ma opened the Lau Basin (fig. 9C), which separated 

the relict arc of the Lau Ridge from the currently active Tonga

(Tofoa)-Kermadec Arc (Fiji Ministry of Lands and Mineral 

Resources, 2010). Back-arc spreading in the North Fiji Basin, 

and later in the Lau Basin, separated the opposite-facing Vanuatu and Tonga Arcs as the Fiji Platform (Lau Ridge) rotated 

counterclockwise from about 5–3 Ma, subsequent to collision 

of the Melanesian Border Plateau18 with the Melanesian Arc 

(Tanaka and others, 2010).

18 Melanesian Border Plateau: a belt of seamounts and ridges of uncertain 

affinity developed on Pacific Plate that borders the Vitiaz Trench Lineament 

and extends 1,500 km west-northwest from the Samoan Islands (Pelletier and 

Auzende, 1996).
New Britain

Manus Island

Bougainville 

Tabar 

New Ireland

Lihir

Tanga

Feni

Viti LevuVanua Levu

NEW CALEDONIA

AUSTRALIA FIJI

Suva

Noumea

Townsville

Rockhampton

Port Moresby

Lae

Coral Sea

Solomon Sea

Bismarck Sea

PACIFIC OCEAN

VITIAZ TRENCH

SAN CRISTOBAL TRENCH

NEW BRITAIN TRENCH

RAMU-MARKHAM FAULT

Fiji Basin

Woodlark Basin

VANUATU ARC

Ontong Java Plateau

OUTER MEL

S

ANESIAN ARC OLOMON ARC

INNER MELANESIAN ARC

150° E 160° E 170° E 180°

0°

10° S20° S

0 250 500 750 1,000 KILOMETERS0 250 500 MILES

Base source: National Oceanic and Atmospheric Administration (2009)ETOPO1 1 Arc-Minute Global Relief ModelPolitical boundary source: U.S. Department of State (2009)Projection: Asia South Albers Equal Area Conic;Central meridian 165° E; latitude of origin 15° S Spreading center

Strike-slip fault

( ( 

EXPLANATION

Figure 8. Map of the Inner and Outer Melanesian Arcs, Papua New Guinea. Locations of modern trenches and spreading centers plotted on sea flooglobal relief model of Amante and Easkins (2009).
24 Porphyry Copper Assessment of Southeast Asia and Melanesia

The Vitiaz Trench lineament, which forms the northern 

border of the North Fiji Basin, marks the relict Vitiaz subduction zone and separates Pacific Plate Cretaceous crust from 

Late Cenozoic crust of the North Fiji and Lau Basins (Pelletier 

and Auzende, 1996). Southerly propagation of a spreading 

center in the Lau Basin since 3 Ma separated the Lau and 

Tonga Ridge ancient arc segments. The Tonga-Kermadec subduction zone (fig. 6) is a classic intraoceanic arc with back-arc 

spreading that accommodates the fastest known rate of active 

subduction; the subduction zone represents a convergent 

boundary where the modern Pacific Plate subducts beneath the 

Indo-Australian Plate.

In Fiji, the period from 35 to 12 Ma is referred to as 

the early arc stage, followed by a 12–7 Ma mature arc stage 

marked by the Colo (Tholo) orogeny, early arc rifting (7–3 

Ma), and a late arc rifting stage that continues today. Modern 

Fiji is situated between the opposing Tonga-Kermadec and 

Vanuatu convergence zones, bordered by the North Fiji Basin 

on the west and the Lau Basin to the east.

Assessment Data

Geologic Maps

Geologic maps at a variety of scales were used during 

the assessment. Maps included proprietary data provided by 

CCOP country representatives, commercially available digital 

geologic compilations, and paper geologic maps. Paper maps 

were scanned and georectified to incorporate them into GIS 

projects to serve as a basis for tract delineation. Page-size 

figures from a variety of publications were used as references 

to identify tectonic features and the extent of magmatic arcs. 

Specific data used for each tract are listed in the appendixes. 

The principal geologic maps used in addition to the proprietary data provided for the assessment are listed in table 3. See 

the appendixes for data used in determining the extent of each 

permissive tract.

Mineral Occurrence Data

A global database of porphyry copper deposits and 

prospects by Singer and others (2008) was supplemented 

with other global and regional mineral-occurrence databases, including the Geological Survey of Canada (Dunne 

and Kirkham, 2000), AMIRA (Khin Zhaw and others, 1999), 

and proprietary data from CCOP (Directorate of Mineral 

Resources and Inventory, 2004b). In addition, commercially 

available databases (InfoMine19, Intierra20, Metals Economic 

Group21), metallogenic maps, technical reports, company 

Web sites, publications and Web sites of geological surveys, 

and geologic literature were consulted. The U.S. Geological 

Survey On-Line Mineral Resources Data (MRDS)22 includes 

information on mines, prospects, and mineral occurrences 

worldwide (U.S. Geological Survey, 2005). Many other 

geological surveys maintain online mineral databases (see, for 

example, Thailand at http://www.dpim.go.th.mne.mn.php).

The assessment team classified sites as deposits (where 

location, deposit characteristics, and resource grades and 

tonnages are known) or prospects (where location, deposit 

characteristics and type, and resource grades and tonnages are 

incompletely characterized). Some prospects reported in data 

sources could not be unambiguously classified as porphyry 

copper deposit types. Deposits and prospects that the team 

could classify as porphyry copper or porphyry-copper-related 

are included in the database for this report. Distributions 

of gold placers, skarns, and epithermal deposits, as well as 

unclassified copper and gold occurrences, were considered 

during the assessment, but they are not typically included in 

the database. Skarns and epithermal deposits may be included 

if the assessment team considered it likely that a porphyry 

system could be associated with them.

Other Data

Compilations of radiometric ages for igneous rocks in 

Southeast Asia provided information about permissive rocks 

that might not be represented on available geologic maps. 

The Southeast Asia radiometric age database of Malaihollo 

and others (2002) covers Indonesia and Papua New Guinea. A 

compilation of available ages for the western Central Range 

of Papua, Indonesia by Jackson (2010) includes new data that 

establishes a Miocene age for previously undated intrusions.

Global aeromagnetic data covers most of Southeast Asia 

(National Geophysical Data Center, 2009). The coarse spatial 

resolution of this aeromagnetic raster data limits its use for 

defining the subsurface extent of the magmatic arcs beneath 

shallow (<1 km) cover. A detailed aeromagnetic data set was 

acquired for part of the Central Highlands in western Papua 

New Guinea on New Guinea Island. Those data, as well as 

local aeromagnetic data reported on company Web sites, 

indicate that discrete, small (<2 km), circular, steep-gradient 

aeromagnetic anomalies correspond to mapped and shallow subsurface Neogene diatreme-like intrusions associated 

with some porphyry copper systems, such as the anomalies 

described at Batu Hijau and at Grasberg by Hoschke (2008).

Regional scale stream-sediment geochemical surveys 

have been undertaken by government agencies and private 

mineral-exploration companies in some regions, but availability, processing, and incorporation of such data for so many 

areas is beyond the scope of a global assessment. Regional 

stream-sediment and soil geochemistry is one of the primary 

mineral-exploration tools used in Southeast Asia to target 

areas for more detailed mapping, exploration geophysical 

surveys, exploration geochemical surveys using rock-chip 

sampling and trenching, and drilling.

19 http://www.infomine.com/.

20 http://www.intierra.com/Homepage.aspx.

21 http://www.metalseconomics.com/default.htm.

22 http://mrdata.usgs.gov/.
Porphyry Copper Assessment of Southeast Asia and Melanesia 25

EXPLANATION

Ontong Java Platform

Solomon Arc

Vanuatu Arc

New Caledonia

Fiji Platform 

 (Lau Arc-Tonga Arc)

Arcs

Platforms

Trench

Fault zone

Ontong Java

 Plateau

Solomon Arc

Vanuatu Arc

FFZ

MBFZ

Tonga Trench 

Lau Arc 

HKFZ

Stage III (middle Pliocene to Holocene)

 NC

Vitiaz Trench 

Fiji

Plateau Lau

Basin

MP

(SOUTH

FIJI BASIN)

160° E 170° E 180° 170° W

5° S

15° S

25° S

Tonga Arc

C

Stage II (middle Miocene to middle Pliocene)

PACIFIC

PLATE

 INDOAUSTRALIAN

PLATE

Ontong Java

 Plateau Solomon Arc

Vanuatu trench 

Vanuatu Arc

Fiji

Plateau

proto-Lau-Tonga Arc

Fiji

 NC

Platform

Vitiaz Trench 

Tonga Trench 

MP

B

PACIFIC

PLATE

MINERVA PLAIN (MP)

Stage I (early Eocene to middle Miocene)

Solomon Arc

Vanuatu Arc

Vitiaz Trench system

Fiji

Platform

Proto-Lau-Tonga Arc Tonga trench 

A Proto-Solomon Trench

Figure 9. Diagrams showing the tectonic evolution of Melanesia (based on Colley and Greenbaum, 1980 and Colley and Hindle, 1984). A, Stage 

I, early Eocene to middle Miocene, southwestward 

subduction of the Pacific Plate along a continuous 

Solomon-Vitiaz-Tonga Trench system beneath the 

proto-Melanesian Arcs and opening of the Minerva 

Plateau (MP) marginal basin. B, Stage II, middle 

Miocene to middle Pliocene collision of the Ontong 

Java Plateau with the Solomon Arc, arc polarity 

reversal to northeasterly subduction of the IndoAustralian Plate along the Vanuatu Trench, with 

opening of the Fiji Plateau marginal basin. C, Stage 

III, middle Pliocene to Holocene opening of the 

Lau marginal basin, continued opening of the Fiji 

Plateau, and continued development of a complex 

transform fracture system that started in stage II. 

Note the stage III position of the Minerva Plain as 

the modern South Fiji Basin. MBFZ, Melanesian 

Border Fracture Zone; FFZ, Fiji Fracture Zone; 

HKFZ, Hunter-Kandavu Fracture Zone.
26 Porphyry Copper Assessment of Southeast Asia and Melanesia

Satellite imagery proved helpful for confirming mine 

and prospect site locations and for locating and identifying 

topographic and structural features, such as lineaments and 

faults. In many areas, vegetation and cloud cover are too 

dense to allow identification of altered rocks.

Exploration History

Porphyry copper exploration in Southeast Asia 

has been cyclic, driven largely by global metal prices, 

government policies, and accessibility of the region. 

Although the area is considered among the most copperand gold-endowed regions on earth, parts of the area remain 

underexplored (Feebrey, 1999). Political, social, cultural, 

and environmental issues, as well as mining laws, affect 

exploration in the region. Many areas have been closed 

to exploration for many years owing to wars. In addition, 

steep topography, lack of infrastructure, tropical climate 

and vegetation, and natural hazards, such as earthquakes, 

tsunamis, and volcanic eruptions, complicate exploration 

and development. Since the 1960s, changes in mining 

laws in several Southeast Asia countries have made the 

area more attractive for foreign investment in mineral 

exploration and development (van Leeuwen, 1994).

Examples of porphyry copper exploration cycles 

for Indonesia are described below, based on information 

provided in country reports presented at the 2010 CCOPUSGS Workshop in Busan, South Korea, by coauthors of 

this assessment.

Indonesia (Based on contributions of Bambang 

Tjahjono Setiabudi and Dwi Nugroho Sunuhadi)

van Leeuwen (1994) documented several phases of 

mineral exploration in Indonesia up to 1992 that were 

facilitated by a favorable investment climate. The 1961 

to 1976 phase focused on prospects previously identified 

by Dutch investigations between the 1840s and 1930s. 

Porphyry exploration in the early 1970s in the Sunda Arc, 

Sulawesi, and Irian Jaya led to discoveries and award of 

the first contract of work (COW23) at the Ertsberg skarn. 

Intense gold exploration characterized the period from 

1984 to 1990 with a focus on the Cenozoic magmatic 

belts. Grasberg was recognized as a porphyry system in 

the 1970s; Batu Hijau was discovered by stream-sediment 

sampling in 1991. In his 1994 paper, van Leeuwen 

attributed “the unprecedented high level of mineral 

exploration over the past 25 years” to the prospectivity of 

Indonesia and the attractive position for foreign investment, 

and he predicted a new (post-1994) phase of exploration 

for a variety of commodities, with a focus on copper, gold, 

and coal. However, exploration and mining development 

in Indonesia decreased following the 1999 implementation 

of a forestry regulation that prohibited open-pit mining in 

protected forests. Other factors that inhibited exploration 

included violence related to illegal mining activities and 

pressure from social and environmental groups opposed 

to mining. A new mineral and coal mining law passed in 

2009, Law No. 4/009, is anticipated to revitalize the climate 

for mineral exploration and mining to promote national 

development and provide for the welfare of the Indonesian 

people (Setiabudi and Sunuhadi, written commun., 2010).

Permissive Tracts

Tract Delineation

The geology-based strategy for permissive-tract delineation used in this assessment is described herein. The appendixes contain detailed descriptions for individual tracts. Digital 

geologic data were processed in a GIS using ESRI ArcGIS 

software, as follows:

•	 Regional-scale geologic maps and geologic literature were 

used to identify fundamental units for tract delineation, 

which were defined as magmatic arcs, or belts of igneous 

rocks, of a given age range.

•	 Digital geologic maps at scales ranging from 1:200,000 

to 1:1,000,000 were then used to select map units to 

define preliminary permissive tracts for porphyry copper 

deposits. Igneous map units were separated by age groups 

and classified as permissive or non-permissive based 

on lithology. Permissive rocks include calc-alkaline 

and alkaline plutonic and volcanic rocks. Other igneous 

rocks, such as ultramafic rocks, highly evolved granites, 

peraluminous granites, and pillow basalts were excluded 

from tract delineation as they are unlikely to be associated 

with porphyry copper deposits.

•	 Buffers were applied to the polygons that represent these 

permissive rocks to account for spatial uncertainty and 

extension of permissive units under shallow cover rocks. 

Typically, a 10-km buffer24 was applied to plutonic rock 

polygons and a 2-km buffer to volcanic rock polygons; 

this generally expanded the area of the tract to include all 

known porphyry copper deposits and significant associated 

prospects. The buffer also accounts for uncertainties in 

the cartographic position of mapped contacts, as well as 

possible unexposed or unmapped permissive rocks. After 

23 COW (Contract of Work): The Indonesian legal framework for foreign 

investment initiated in 1967. 24 For some small islands and areas where cross sections on geologic maps 

indicated steep-sided intrusions, a buffer distance of 5 km was used. See 

appendixes for criteria used to delineate each tract.
Porphyry Copper Assessment of Southeast Asia and Melanesia 27

buffering, the assessment team examined available data 

on mineral deposits, prospects, and occurrences; locations 

of dated igneous rock samples; and geophysical and 

geochemical information to ensure that the tract included 

any other evidence of unmapped permissive rocks or 

hydrothermal systems.

•	 An aggregation and smoothing routine was applied to the 

resulting polygons, and the tracts were edited by hand to 

honor post-mineral fault boundaries. In some cases, more 

detailed geologic maps were acquired to resolve tractboundary issues, or page-size map illustrations from the 

literature were incorporated to fill in gaps in available 

digital geologic maps.

•	 Volcanic centers and other areas of volcanic cover where 

the thickness of cover was known to exceed 1 kilometer 

were generally excluded from tracts by using a buffer 

zone around the volcano based on topography. Intrusions younger than the designated tract age and ophiolitic 

and ultramafic rocks also were excluded. Volcanic rocks 

younger than the designated tract age, but inferred to be 

less than 1 kilometer thick, may be present as cover over 

permissive areas.

•	 Resulting tract boundaries were clipped to shorelines to 

eliminate undersea areas using small-scale digital international land-boundary polygon files from the U.S. Department of State (2009)25, which incorporate high-tide coastline data from the U.S. National Geospatial-Intelligence 

Agency’s World Vector Shoreline26dataset.

Permissive Tracts for Porphyry Copper Deposits 

in Southeast Asia and Melanesia

Twenty two permissive tracts for porphyry copper deposits 

were delineated within the study area (table 4, figs. 1, 10–13). 

Permissive tracts primarily are based on the mapped extent of 

igneous rocks that are permissive for porphyry copper deposits. 

Permissive tracts may represent segments of an arc or magmatic 

belt that are differentiated from other segments based on different geologic characteristics (such as levels of exposure), different amounts of information, and (or) different probabilities of 

occurrence of undiscovered deposits. Permissive tracts are listed 

by geographic area, along with the countries included within 

each tract and the fundamental geologic features delineated for 

the assessment (table 4). Brief summaries of the tracts, by area, 

are included in this discussion. More detailed tract descriptions 

are presented in the appendixes. Porphyry copper deposits with 

reliable identified resources are listed by area and by permissive tract in table 5. Deposits and significant prospects and 

Table 3. Principal geologic maps used for the assessment of Southeast Asia and Melanesia.

 Description Reference

Digital geologic map of East and Southeast Asia CCOP and Geological Survey of Japan (1997)

Digital geologic maps of Myanmar, Laos, Cambodia, Thailand, 

Vietnam, and Yunnan Province, China

Khin Zaw and others (1999), Geological Survey of Vietnam (1991)

Digital geologic map of Indonesia Directorate of Mineral Resources and Inventory (2004a) [proprietary data]

Geologic map of Irian Jaya, Indonesia (1:1,000,000) Dow and others (1986)

Systematic 1:250,000-scale geologic maps of Indonesia Directorate of Mineral Resources and Inventory (1987–2000)

Digital geologic map of Sabah (1:500,000) Director-General Geological Survey of Malaysia (1985)

Digital geologic map of Papua New Guinea compiled from 

1:250,000-scale geologic maps 

Papua New Guinea Geological Survey (2002)

Geology of Papua New Guinea Bain and others (1972)

Digital and paper geologic maps of the British Solomon Islands Geological Survey Division of the Ministry of Natural Resources (1969)

Geologic maps of the New Hebrides Islands (1:100,000) New Hebrides Geological Survey (1972, 1975, 1977)

Geological map of Fiji (1:500,000) Geological Survey Department, Fiji (1965)

Metallogenic maps of Vanua Levu and Viti Levu, Fiji (1:250,000) Mineral Resource Division—Fiji (1978a,b)

25 The political boundaries used in this report are, in accord with U.S. 

Government policy, the small-scale digital international boundaries (SSIB) 

provided by the U.S. Department of State (U.S. Department of State, 2009). In 

various parts of the world, some political boundaries are in dispute. The use of 

the boundaries certified by the U.S. Department of State does not imply that 

the U.S. Geological Survey advocates or has an interest in the outcome of any 

international boundary disputes. 26 http://shoreline.noaa.gov/data/datasheets/wvs.html.
28 Porphyry Copper Assessment of Southeast Asia and Melanesia

Table 4. Permissive tracts for porphyry copper deposits in Southeast Asia and Melanesia. 

 Coded

_Id Tract name Countries Geologic feature assessed

Indochina peninsular area 

A 142pCu7021 Sukhothai China, Myanmar, 

Thailand, Lao People’s 

Democratic Republic, 

Cambodia, and Vietnam 

An assemblage of Carboniferous through Triassic rocks that were formed as 

both island arcs and continental arcs by subduction of Paleotethyan oceanic 

crust below the South China block in Yunnan, and below Indochina (the 

Loei and Truong Son volcanic arcs)

B 142pCu7022 Malaysia Malaysia, Thailand, 

Singapore, and Indonesia

An assemblage of Carboniferous through Triassic rocks that were formed as 

both island arcs and continental arcs by subduction of Paleotethyan oceanic 

crust below the East Malaya terrrane

C 142pCu7023 Mekong Delta Vietnam, Cambodia, and 

Lao People’s Democratic 

Republic

A field of Jurassic and Cretaceous intrusive and volcanic rocks that are the 

result of subduction of the Pacific Plate beneath southern Indochina

D 142pCu7024 Wuntho-Popa Myanmar and India A linear belt of Late Cretaceous through Holocene volcanic rocks related to 

subduction of the Indian Ocean Plate below Indochina 

Indonesian Islands area

E 142pCu7020 Sumatra Island Indonesia An Eocene-Pliocene continental magmatic arc that straddles the northwesttrending Sumatran Fault Zone in western Sumatra. Known porphyry 

copper deposits and prospects are Miocene-Pliocene in age. 

F 142pCu7025a Sunda Banda Arc Indonesia The eastern part of the Eocene to Holocene Sunda-Banda magmatic arc; 

Java Island 

142pCu7025b The eastern part of the Eocene to Holocene Sunda-Banda magmatic arc; 

Bali to West Flores Islands

142pCu7025c The eastern part of the Eocene to Holocene Sunda-Banda magmatic arc; 

east Flores to Wetar Islands

G 142pCu7026 West Sulawesi Indonesia Miocene to Pliocene igneous rocks in the southern portion of the 1,200 km 

long Sulawesi-Sangihe magmatic arc, located in southwestern Sulawesi

H 142pCu7027 North Sulawesi-Sangihe Indonesia Miocene to Pliocene volcanic and intrusive rock portion of the North 

Sulawesi-Sangihe magmatic arc

I 142pCu7019 Central Kalimantan Indonesia and Sabah and 

Sarawak, Malaysia

A dispersed belt of Tertiary intermediate intrusive and volcanic rocks that 

postdate pre-Eocene subduction and deformation, uplift, and erosion of 

pre-Miocene rocks and continental basement in Kalimantan

J 142pCu7201 Ambon Arc, Central 

Molucca Islands

Indonesia Plio-Quaternary Ambon island arc (northern Outer Banda Arc), eastern 

Indonesia

K 142pCu7202 Halmahera Arc, North 

Molucca Islands

Indonesia Neogene Halmahera island arc

New Guinea Island, Indonesia and Papua New Guinea and other Papua New Guinea islands

L 142pCu7205 Moon-Utawa -Ular 

Merah Areas

Indonesia Miocene Moon-Utawa arc in Papua and West Papua 

Provinces, Indonesia 

M 142pCu7203 Western Medial New 

Guinea Magmatic Belt

Indonesia Late Miocene to Pliocene-Pleistocene Medial New Guinea magmatic belt

N 142pCu7204 Rotanburg-Taritatua Area Indonesia Late Miocene to Pliocene-Pleistocene intrusive rocks.

O 009pCu7203a Eastern Medial New 

Guinea Magmatic Belt

Papua New Guinea Late Miocene to Pliocene-Pleistocene Medial New Guinea magmatic belt

009pCu7203b Papua New Guinea

P 009pCu7205 Maramuni Arc Papua New Guinea Miocene Maramuni magmatic arc 

Q 009pCu7206 Miocene Alkaline Rocks, 

Southeastern Papua New 

Guinea

Papua New Guinea Miocene alkaline island arc intrusive rocks

R 142pCu7208 Inner Melanesian Arc 

Terranes I- Indonesia 

Indonesia Eocene-Oligocene to early Miocene accreted Inner 

Melanesian magmatic arc terranes of Papua, Indonesia

S 009pCu7208 Inner Melanesian Arc 

Terranes II- Papua New 

Guinea 

Papua New Guinea Eocene-Oligocene to early Miocene accreted Inner 

Melanesian magmatic arc terranes of New Guinea Island

T 009pCu7209 Inner Melanesian Arc 

(New Britain) 

Papua New Guinea Eocene-Oligocene to early Miocene Inner Melanesian Arc on New Britain 

U 009pCu7207 Outer Melanesian Arc I 

-Papua New Guinea 

Papua New Guinea Eocene to Holocene Outer Melanesian Arc

Melanesia

V 009pCu7210 Outer Melanesian Arc IIMelanesia Solomon Islands, 

Vanuatu, and Fiji

Eocene to Holocene Outer Melanesian Arc

Appendix
Porphyry Copper Assessment of Southeast Asia and Melanesia 29

occurrences are tabulated and plotted on figures in appendixes 

A–V. Site locations and attributes are included in a shapefile in 

appendix W. Readers should refer to figures in the appendixes 

for locations of deposits mentioned in the following subsections 

of the report.

Indochina Peninsula Area

Four permissive tracts for porphyry copper deposits are 

delineated in the Indochina Peninsula area (fig.10, table 4). 

See appendixes A–D for assessment details and additional 

references.

Two tracts, Sukhothai (142pCu7021) and Malaysia 

(142pCu7022) are defined by Carboniferous through Triassic 

rocks that represent both island and continental arcs related to 

the subduction of Paleotethyan oceanic crust. The permissive 

rocks are chiefly of intermediate, metaluminous I-type 

composition, and they contrast sharply with the collisionrelated peraluminous S-type granitoids that are widely 

distributed on the Indochina Peninsula. The larger tract, 

Sukhothai (354,260 square kilometers, km2), consists of three 

belts of permissive rocks. The westernmost belt, known as the 

Sukhothai island-arc system, extends from southern Yunnan 

Province, in China, through western Lao People’s Democratic 

Republic, Thailand, and, after interruption by the Gulf of 

Thailand, through the eastern part of Peninsular Malaysia (as 

tract 142pCu7022). The second, the Loei Belt just to the east, 

is in the Lao People’s Democratic Republic and Thailand, and 

the third belt, Truong Son, trends southeastwards through the 

Lao People’s Democratic Republic [labeled as Laos on fig. 

10] and Vietnam. The tract includes the 250 Ma Phu Kham 

porphyry copper-gold deposit (table 5) and several significant 

prospects in Thailand and Vietnam, as well as the very large 

Sepon copper-gold skarn and replacement district in the Lao 

People’s Democratic Republic.

The Malaysian tract (142pCu7022) extends for 60,000 

km2 across Malaysia and parts of Thailand, Singapore, and 

Indonesia. The tract includes the Mengapur deposit (45 

Mt, 1.8 percent copper, 0.6 g/t gold) that was classified as 

a porphyry copper deposit by Singer and others (2008). 

However, the deposit is better classified as a copper-gold-iron 

skarn with porphyry copper affinity. Six oxidized orebodies 

currently are being mined, and there are also seven sulfide 

bodies, all surrounding a weakly mineralized adamellite 

intrusion (Kiang, 2008). Scattered copper- and gold-bearing 

vein and skarn prospects, as well as gold-rich polymetallic 

vein deposits throughout the tract are indicative of the 

porphyry copper environment.

The 91,220 km2

 Mekong Delta tract (142pCu7023) 

delineates Jurassic and Cretaceous intrusive and volcanic 

rocks formed by subduction of the Pacific Plate beneath 

southern Indochina. The tract covers parts of Vietnam, 

Cambodia, and Lao People’s Democratic Republic. The tract 

is an excellent example of an underexplored area, in this case, 

because of prolonged warfare in the late 20th century.

The Wuntho Popa tract (142pCu7024) in Myanmar 

defines a belt of Miocene through Holocene volcanic rocks 

related to oblique subduction of the Indian Ocean Plate 

beneath Indochina. The only porphyry copper deposit known 

within the tract is the 5.8 Ma Monywa deposit, which contains 

more than 6 Mt copper (table 5), although there are other 

poorly documented prospects surrounding the deposit.

Indonesian Islands Areas

Seven permissive tracts for porphyry copper deposits 

are delineated in the Indonesian Islands (fig. 11, table 4). See 

appendixes E–K for assessment details.

The Sumatra Island tract (142pCu7020) delineates 

Eocene-Pliocene continental magmatic arc rocks that straddle 

the northwest-trending Sumatran Fault Zone in western 

Sumatra. The only porphyry copper deposit with identified 

resources within the 131,030 km2 tract is the 11 Ma Tangse 

deposit with 900,000 t contained copper (table 5).

The Sunda-Banda Arc tract (142pCu7025) consists of 

the eastern parts of the 3,800-km-long Eocene to Holocene 

Sunda-Banda Arc. The tract was assessed in three segments 

based on differences in crust underlying the arc: sub-tract 

142pCu7020a, the Java segment, which is developed on 

continental crust of the Sundaland part of the Eurasian Plate; 

sub-tract 142pCu7020b, the arc segment from Bali to west 

Flores Islands, which is an island arc constructed on oceanic 

crust; and sub-tract 142pCu7020c, from east Flores to Wetar 

Islands, which is an arc constructed on oceanic crust or highly 

thinned continental crust (Carlile and Mitchell, 1994). The 

world-class Batu Hijau (fig. 1) porphyry copper-gold deposit 

(>7 Mt contained copper), discovered in 1991, is in sub-tract 

b and represents the only known porphyry copper deposit 

with identified resources in the arc.

The island of Sulawesi was assessed using two tracts, 

both part of the 1,200-km-long, Eocene to Holocene, 

Sulawesi-Sangihe magmatic arc. The West Sulawesi tract 

(142pCu7206) is partly developed on continental crust containing pre-Tertiary polymetamorphic rocks and Cretaceous 

plutons and has a complex history, including three overlapping volcanic-arc events. No porphyry copper deposits are 

known in the West Sulawesi tract. However, the tract does 

contain the 4.14 Ma Malala low-fluorine porphyry molybdenum deposit in the northern part of the tract and the Sassak 

porphyry copper prospect. The North Sulawesi-Sangihe tract 

(142pCu7207) outlines an island arc complex developed on 

Cretaceous to Paleogene oceanic crust (Carlile and others, 

1990). It formed during multistage and multidirectional subduction from the Eocene to present in the complex convergence zone of the Eurasian, Pacific, and Australian Plates 

(Kavalieris and others, 1992; Hall, 1996, 2002; Pearson 

and Caira, 1999; Simandjuntak and Barber, 1999). The tract 

includes the 3.75 Ma Tapadaa (232,200 t contained copper) and the 3.0 Ma Tombulilato (~1.8 Mt contained copper) deposits, both developed in shallowly emplaced quartz 
30 Porphyry Copper Assessment of Southeast Asia and Melanesia

LAOS

INDIA

CHINA

CHINA

INDONESIA

MYANMAR

THAILAND

MALAYSIA

VIETNAM

CAMBODIA

SINGAPORE

!

!

!

!

!

!

!

!

!

!

!

Rangoon

Kunming

Ho Chi

Minh City

Hanoi

Medan

Andaman Sea

Gulf of Thailand

SOUTH CHINA SEA

INDIAN OCEAN

95° E 105° E

25° N

15° N

5° N

Political boundary source: U.S. Department of State (2009)

Projection: Asia South Albers Equal Area Conic;

Central meridian 102° E; latitude of origin 15° S

0 200 400 KILOMETERS

0 100 200 MILES

EXPLANATION

Porphyry copper tracts of the

Indochina Peninsula area

142pCu7021

142pCu7022

142pCu7023

142pCu7024

Figure 10. Map of permissive tracts for porphyry copper deposits, Indochina Peninsula Area, Southeast Asia. Tract 

coded identifiers and tracts names are: 142pCu7021 (Sukhothai), 142pCu7022 (Malaysia), 142pCu7023 (Mekong Delta), and 

142pCu7024 (Wuntho-Popa).
!

!

! !

!

Medan

Bandung Semarang

Surabaja

MALAYSIA

INDONESIA

MALAYSIA

INDONESIA

INDONESIA

INDONESIA

THAILAND

SINGAPORE

Andaman Sea

SOUTH CHINA SEA

Java Sea

 Celebes Sea

Sulu Sea

INDIAN OCEAN

Makassar Straits

100° E 110° E 120° E

0°

10° S

Political boundary source U.S. Department of State (2009)Projection: Lambert Azimuthal Equal Area;Central meridian 105° E; latitude of origin 0° N

0 400 800 KILOMETERS

0 200 400 MILES

EXPLANATION

Porphyry copper tracts of the

Indonesian Islands area

142pCu7019142pCu7020142pCu7025A142pCu7025B142pCu7025C142pCu7026142pCu7027142pCu7201142pCu7202

Political boundary source: U.S. Department of State (2009)Projection: Lambert Azimuthal Equal Area;Central meridian 105° E; latitude of origin 0° N 

Figure 11. Map of permissive tracts for porphyry copper deposits, Indonesian Islands Area, Southeast Asia. Tract coded identifiers and tracts na

(Central Kalimantan), 142pCu7020 (Sumatra Island), 142pCu7025 (Sunda Banda Arc, sub-tracts a, b, and c), and 142pCu7026 (West Sulawesi), 142pCSangihe), 142pCu7201 (Ambon Arc, Central Molucca Islands), and 142pCu7202 (Halmahera Arc, North Molucca Islands).
PAPUA NEW GUINEA INDONESIA

AUSTRALIA AUSTRALIA

 PACIFIC OCEAN Bismarck Sea Solomon Sea Coral Sea

Gulf of Carpentaria

Arafura Sea

130° E 140° E 150° E

0°

5° S

10° S

Political boundary source: U.S. Department of State (2009)Projection: Asia South Albers Equal Area Conic;Central meridian 140° E; latitude of origin 15° S

0 200 400 KILOMETERS

0 100 200 MILES

EXPLANATION

Porphyry copper tracts for

New Guinea and other islands

009pCu7203A009pCu7203B009pCu7205009pCu7206009pCu7207009pCu7208009pCu7209142pCu7203142pCu7204142pCu7205142pCu7208

Figure 12. Map of permissive tracts for porphyry copper deposits, New Guinea Island, Indonesia and Papua New Guinea, and other Papua New 

east Asia. Tract coded identifiers and tracts names for Papua New Guinea (Oceania region): 009pCu7203 (Western Medial New Guinea Magmatic b), 009pCu7205 (Maramuni Arc), 009pCu7206 (Miocene Alkaline Rocks, Southeastern Papua New Guinea), 009pCu7207 (Outer Melanesian Arc I—P009pCu7208 (Inner Melanesian Arc Terranes II—Papua New Guinea), and 009pCu7209 (Inner Melanesian Arc—New Britain). Tract coded identifiefor Indonesia (Asia region): 142pCu7203 (Western Medial New Guinea Magmatic Belt-Indonesia), 142pCu7204 (Rotanburg-Taritatua Area), 142pCuMerah Areas), and 142pCu7208 (Inner Melanesian Arc Terranes I—Indonesia).
Figure 13. Map of permissive tract for porphyry copper deposits 009pCu7210 (Outer Melanesian Arc II—Melanesia). The tract includes 3 segmen

(SI), Vanuatu (V), and Fiji (F). AUSTRALIA

SOLOMON

ISLANDS

VANUATU

FIJI

NEW

CALEDONIA

PAPUA NEW

GUINEA

PACIFIC OCEAN

Coral Sea

Solomon Sea

160° E 180°

10° S20° S

Political boundary source U.S. Department of State (2009)Projection: Asia South Albers Equal Area Conic;Central meridian 165° E; latitude of origin 15° S

0 400 800 KILOMETERS

0 200 400 MILES

200 600

EXP

Porphyry 

M
34 Porphyry Copper Assessment of Southeast Asia and Melanesia

diorite intrusions and with local supergene copper enrichment 

(Lowder and Dow, 1976, 1978).

The Central Kalimantan tract (142pCu7019) encloses 

a dispersed belt of late Oligocene to Pliocene intermediate 

intrusive and volcanic rocks across Kalimantan, Indonesia 

and parts of Sabah and Sarawak, Malaysia (fig. 11). The igneous rocks postdate folding, thrusting, uplift, and erosion of 

pre-Miocene rocks and continental basement in Kalimantan. 

The relationship of these mid- to late-Tertiary igneous rocks 

to subduction is unclear, and the porphyry copper deposits 

that occur in this tract postdate subduction and have an origin 

similar to the postsubduction porphyry copper-gold deposit 

Table 5. Summary of identified resources in porphyry copper deposits of Southeast Asia and Melanesia. 

[Ma, million years; Mt, million metric tons; t, metric tons; %, percent; g/t, grams per metric ton (= parts per million); -, no data. *, Mengapur is included as a 

porphyry copper deposit in Singer and others (2008) but is better classified as a skarn deposit]

Tract Tract name Name Age 

(Ma)

Tonnage 

(Mt)

Cu

(%)

Mo

(%)

Au

(g/t)

Ag

(g/t)

Contained 

Cu (t)

Contained 

Au (t)

Indochina peninsular area 

142pCu7021 Sukhothai Phu Kham 292 183 0.64 - 0.24 2 1,171,200 44

142pCu7022 Malaysia Mengapur* Triassic 45 1.80 0.60 810,000 27

142pCu7024 Wuntho-Popa Monywa Miocene 1,700 0.37 - - - 6,290,000 -

Total for Indochina peninsular area 8,271,200 71

Indonesian Islands area

142pCu7020 Sumatra Island Tangse 11 600 0.15 0.02 - - 900,000 -

142pCu7025 Sunda Banda Arc Batu Hijau 3.7 1,640 0.44 - 0.35 0.55 7,216,000 574

142pCu7027 North Sulawesi Tapadaa 3.75 43 0.54 - 0.08 - 232,200 3

142pCu7027 North Sulawesi Tombulilato 3 287 0.63 - 0.47 - 1,808,100 135

142pCu7019 Central Kalimantan Mamut 7 196 0.48 0.001 0.50 2.5 940,800 98

142pCu7202 Halmahera Arc Kaputusan Miocene? 77 0.33 - 0.25 - 254,100 19

Total for Indonesian Islands area 11,351,200 829

New Guinea Island, Indonesia and Papua New Guinea and other Papua New Guinea islands

142pCu7203 Western Medial New Guinea 

Magmatic Belt

Grasberg 3 4,000 0.60 - 0.64 2 24,000,000 2,560

009pCu7203a Eastern Medial New Guinea 

Magmatic Belt

Ok Tedi 1.15 854 0.64 0.011 0.78 - 5,465,600 666

009pCu7203a Eastern Medial New Guinea 

Magmatic Belt

Star Mount Futik 3.65 65 0.54 - 0.10 - 351,000 7

009pCu7203a Eastern Medial New Guinea 

Magmatic Belt

Star Mount Nong 

River

3.55 60 0.50 - - - 300,000 -

009pCu7203b Eastern Medial New Guinea 

Magmatic Belt

Kodu (Ofi Creek, 

Mount Bini)

4.40 276 0.28 0.008 0.30 1.75 759,000 83

009pCu7203b Eastern Medial New Guinea 

Magmatic Belt

Wafi-Golpu 9 540 0.90 0.01 0.56 - 4,860,000 302

009pCu7203b Eastern Medial New Guinea 

Magmatic Belt

Yandera 7 1,639 0.35 0.01 0.07 1.5 5,749,926 115

009pCu7205 Maramuni Arc Frieda River 12 1,900 0.45 0.004 0.22 0.7 8,550,000 418

009pCu7209 Inner Melanesian Arc 

(New Britain) 

Simuku 24 200 0.36 0.008 0.07 2 720,000 12

009pCu7207 Outer Melanesian Arc I -

Papua New Guinea 

Arie 15 165 0.32 - 0.10 - 528,000 -

009pCu7207 Outer Melanesian Arc I -

Papua New Guinea 

Panguna 3.4 1,420 0.47 0.005 0.57 1.1 6,603,000 809

Total for New Guinea Island, Indonesia and Papua New Guinea and other Papua New Guinea islands 57,886,526 4,972

Melanesia

009pCu7210 Outer Melanesian Arc IIMelanesia Koloula (Guadalcanal Joint Venture)

2 50 0.170 - - - 85,000 -

009pCu7210 Outer Melanesian Arc IIMelanesia Namosi -6 1,792 0.370 0.014 0.12 - 6,630,400 215

009pCu7210 Outer Melanesian Arc IIMelanesia Waivaka -6 23 0.750 - 0.25 - 172,500 5.8

Total for Melanesia 6,887,900 221

Total for Southeast Asia 84,396,826 6,095
Porphyry Copper Assessment of Southeast Asia and Melanesia 35

model described by Richards (2009). The only deposit with 

identified resources within the tract is the 7 Ma Mamut porphyry copper-gold deposit (fig. 1, table 5).

The Halmahera tract (142pCu7202) outlines permissive 

rocks of the Neogene Halmahera Arc in the North Molucca 

Islands, Indonesia. Neogene arc rocks include diorite to 

granodiorite intrusions emplaced into andesitic volcanic rocks 

and have geochemical signatures indicating contributions of 

continental crust. The continental-crust component is attributed to underlying Australian continental crust displaced along 

the Sorong Fault (Garwin and others, 2005). The Kaputusan 

(fig. 1) porphyry copper-gold deposit on Bacan Island contains identified resources of 77 Mt at 0.33 percent copper and 

0.25 g/t gold. The tract also includes the Pliocene Gosowong 

quartz- alunite epithermal gold deposit that is currently mined.

The Ambon tract (142pCu7201) outlines Pliocene to 

Pleistocene intrusive and volcanic rocks within the Pliocene 

to Holocene Ambon island arc. The Ambon Arc is the northwesternmost curved segment extension of the Banda Arc system. The west-facing, curvilinear Banda Arc system formed at 

the intersection of the Indo-Australian, Pacific, and Eurasian 

Plates. Honthaas and others (1999) defined the Ambon Arc as 

a separate arc based on its distinctive Pliocene and younger 

volcanic-rock geochemistry. Seismic data (McCaffrey, 1988) 

suggest that the Banda Arc overlies two discrete subduction 

zones: (1) southward subduction of Irian Jaya continental 

crust beneath Seram along the Seram Trough; and (2) northward subduction beneath Wetar to Manuk. The tract contains 

the Hila porphyry copper-gold prospect and associated copper 

and gold occurrences.

New Guinea Island and Papua New Guinea 

Islands

Ten permissive tracts are delineated on New Guinea 

Island and the Papua New Guinea Islands of New 

Britain, Manus, Bougainville, New Ireland, and the 

D’Entrecasteaux and Tabar-Fini-Lihir island groups (figs. 

7, 8, and 12). Because the island of New Guinea includes 

two countries, Indonesia (UN region 142) and Papua New 

Guinea (UN region 009), the permissive tracts for this 

region are numbered accordingly. Tracts outline EoceneOligocene arc segments, Miocene arc segments, and late 

Miocene to Pliocene arc segments.

The Moon-Utawa-Ular Merah tract (142pCu7205) 

delineates igneous rocks associated with the middle to late 

Miocene igneous rocks on western New Guinea Island. 

The Moon Arc area in the northern part of the Bird’s Head 

region of Indonesia and the Utawa diorite at the base of 

the Bird’s Neck are age-equivalent to the Maramuni Arc 

(009pCu7205) in the Mobile Belt of Papua New Guinea. 

No deposits are known in the Moon-Utawa Arc, although 

exploration projects are active in the Moon Arc area. 

Carlile and Mitchell (1994) considered the Moon-Utawa 

Arc to be underexplored at that time. The Utawa segment 

lacks volcanic rocks (that is, it may be too deeply eroded 

to preserve porphyry deposits); however, anomalous gold 

has been detected by exploration in the area, mainly in 

stream sediments. We include the recently dated Miocene 

intrusions of the Ular Merah area in the tract, although the 

relations to the Moon-Utawa Arc, if it exists, are enigmatic. 

The Ular Merah area is centered on a Miocene (17.4–16.6 

Ma) porphyry system that intruded the allochthonous Central Ophiolite Belt in Irian Jaya, about 150 km northwest 

of the Erstberg mining district (Jackson, 2010). PT Freeport Indonesia explored the Ular Merah area in 2007; five 

cores drilled in areas of anomalous copper and gold in soil 

samples showed little evidence of copper mineralization 

(Jackson, 2010).

The western part of the Medial New Guinea magmatic 

belt, an 1,800-km-long, east-west belt of discontinuous 

exposures of late Miocene to Pliocene igneous rocks in 

the fold belt of central New Guinea Island in Indonesia, is 

delineated as tract 142pCu7203. The tract, which includes 

the Grasberg mine, extends eastward to a 300-km-wide 

“gap” in Neogene intrusions that extends to the Papua New 

Guinea border; the gap area is lower in elevation (generally <2,000 m) than the Grasberg area (Cloos and others 

2005). The intrusions in the western Medial New Guinea 

magmatic belt represent post-collisional magmas emplaced 

through continental crust. Pliocene intrusions are present at 

the highest elevations in the Central Range (Cloos and others, 2005); coeval volcanic rocks are absent.

The eastern part of the Medial New Guinea magmatic belt in Papua New Guinea is represented by tract 

009pCu7203. The basement rocks of the magmatic 

belt differ from west (tract 142pCu7203a) to east (tract 

009pCu7203b). The belt is bisected by the Tasman Line 

(fig. 6) that defines the boundary between two crustal 

provinces in northern Australia: Paleozoic basement 

composed of Paleozoic accreted terranes of the Tasman 

orogen lie to the east of the line, whereas the stable craton 

with Precambrian basement lies to the west (Hill and Hall, 

2003). These differences in basement affect the crustal 

response to deformation, and may influence the character 

of porphyry-related magmas. The tracts include several 

discrete subareas. The western tract includes an area of 

the Bird’s Head where no permissive rocks are mapped at 

the surface but were encountered at depth (>500 m) during 

exploration drilling (Arc Exploration, 2009), as well as an 

area of permissive volcanic rocks along the eastern side of 

Cenderawasih Bay, and the Grasberg mine area. Approximately 16 small (a few to several hundred square meters), 

hypabyssal Pliocene intrusions have been identified in the 

Gunung Bijah mining district; the largest intrusions (a few 

square km in outcrop area) are the Erstberg Diorite (3.00 

± 0.08 Ma) and the Grasberg Igneous Complex (2.6–4.4 

Ma). The Grasberg (fig. 1) supergiant deposit (4,000 Mt 

at 0.6 percent copper, 0.64 g/t gold) is the largest coppergold porphyry deposit in the world and the largest porphyry 

deposit in Southeast Asia. The eastern part of the magmatic 
36 Porphyry Copper Assessment of Southeast Asia and Melanesia

belt, mainly in Papua New Guinea, is assessed in two segments based on differences in relative amounts of volcanic and intrusive rocks. Sub-tract 009pCu7203a includes 

porphyritic rocks of the Star Mountain Intrusives associated 

with the Ok Tedi, Star Mount Futik, and Star Mount Nong 

River porphyry copper-gold deposits (fig.1). Sub-tract 

009pCu7203b includes several areas of late Miocene to 

Pliocene intrusions and coeval volcanic rocks in the Central 

Highlands, Papuan Peninsula, and scattered areas along 

the northern coast of New Guinea Island. The sub-tract 

includes the 450 Mt Yandera deposit, Wafi-Golpu, and the 

Kodu (Mt. Bini) deposits (fig. 1), as well as several active 

exploration projects.

The Maramuni Arc (tract 009pCu7205) is defined by 

mapped early to late Miocene intrusive and volcanic-rock 

exposures, including the rocks of the Frieda River Intrusive 

Complex. The complex contains at least seven centers of 

porphyry copper mineralization, including the Horse-IvaalTrukai deposit, which is considered one of the world’s 

largest undeveloped porphyry copper-gold deposits with 

estimated resources of 7.5 Mt of copper and 14.3 million 

ounces of gold (D. Saroa, written commun., 2010).

Tract 009pCu7206 outlines four areas of middle 

Miocene alkaline intrusions of probable island arc affinity in southeastern Papua New Guinea. These rocks were 

described by Smith (1972) as a suite of high-potassium 

(shoshonitic) intrusions that may represent small volumes 

of magma intruded into a subvolcanic environment at the 

beginning of a period of late Cenozoic uplift. The Poi porphyry copper-gold prospect is associated with these rocks.

Three areas on New Guinea Island are treated as qualitative tracts. No estimate of undiscovered porphyry deposits was made of these tracts because of uncertainties about 

map units and lack of evidence of mineral occurrences 

that might be related to porphyry copper deposits. Further 

characterization of these areas, or access to information 

that was unavailable for this assessment, could change 

our assessment. The tracts are (1) an area of igneous rocks 

mapped as late Miocene to Pliocene in the RotanburgTaritatua of Indonesia (tract 142pCu7204), and (2) Late 

Cretaceous to early Miocene accreted terranes of the Inner 

Melanesian Arc in Indonesia and Papua New Guinea (tracts 

142pCu7208 and 009pCu7208, respectively).

The Eocene to Oligocene Inner Melanesian Arc on 

New Britain is assessed as tract 009pCu7209. The Simuku 

deposit in the tract has inferred resources of 200 Mt at 0.36 

percent copper, 0.07 g/t gold, 0.0076 percent molybdenum, 

and 2 g/t silver. Resources in this deposit are incompletely 

defined. Several other porphyry copper prospects on New 

Britain were dated at 24–25 Ma (Whalen and McDougal, 

1980). The Sinivit gold mine (a quartz-alunite epithermal 

system) in the northeastern part of the island exploits an 

oxidized cap containing copper and gold along a 1-km-wide 

by 10-km-long structural zone (Lindley, 1998; New Guinea 

Gold Corporation, 2009; Stagg, 2006). Porphyry style 

alteration (potassic, argillic, sericitic, propylitic) is associated with a composite porphyry intrusion located west of 

the Mount Sinivit gold deposit.

Segments of the more than 800-km-long Outer Melanesian Arc in Papua New Guinea are delineated as tract 

009pCu7207 (fig. 12). See figure 8 for locations of the 

islands of the Outer Melanesian Arc. Porphyry copper 

prospects on Manus are associated with middle Miocene 

calc-alkaline intrusions. In the New Ireland area, the tract 

includes early or middle Oligocene and middle Miocene 

intrusions of the Lemau Intrusive Complex and younger porphyritic diorite and quartz diorite intrusions. The Legusulum 

porphyry copper prospect is associated with diorite, diorite 

porphyry, gabbro, granodiorite and associated agglomerate, and pyroclastic rocks (Mason and McDonald, 1978) 

intruded into volcanic and sedimentary rocks. The islands of 

the Bismarck Archipelago east of New Ireland (Tabar-LihirFeni) represent eroded Quaternary volcanoes with epithermal 

systems overprinting porphyry copper-gold systems. Active 

hydrothermal systems are present on some islands. The 

Ladolam gold deposit on Lihir Island is developed in the 

floor of the alkaline Luise Caldera, where sector collapse at 

0.3 Ma resulted in telescoping of the hydrothermal system 

and superposition of a giant epithermal deposit on a weakly 

mineralized porphyry system.

The 3.4 Ma Panguna (Bougainville) porphyry coppergold deposit in the south-central part of Bougainville 

Island contains 1,420 Mt at 0.465 percent copper, 0.005 

percent molybdenum, and 0.57 g/t gold. This mine produced 2 percent of the world’s copper supply at one time. 

The mine operated from 1972 until 1989, when political 

unrest caused a shutdown and a cessation of any exploration activity. A 1989 study estimated that more than1,000 

Mt of mineable ore remains (Mining Journal, 2009), resulting in the resource estimate above. As of 2011, studies to 

reopen the mine were underway.

Melanesia

The Outer Melanesian Arc south of Papua New Guinea 

is assessed as a single permissive tract 009pCu7210 composed of three segments—Solomon Islands, Vanuatu, and Fiji. 

Although the arc system represents different episodes of arc 

development and fragmentation since the Paleogene, it started 

as a single continuous arc, the Vitiaz Arc. Age information on 

permissive igneous rocks is scarce. In many areas, igneous 

complexes associated with both pre- and postsubduction reversals are essentially colocated. Porphyry copper deposits and 

prospects are associated with both stages of arc evolution.

Most of the porphyry copper deposits and prospects of 

the Melanesian Arcs are associated with the late Miocene-Pliocene arc magmatism, including the 2 Ma Koloulu deposit in 

Guadalcanal in the Solomon Islands (85,000 t contained copper) and the 5.6 Ma Namosi deposit in Fiji (>6 Mt contained 

copper). The Poha and Mbetilonga porphyry copper prospects 

on Guadalcanal and active exploration projects in the Shortland Islands (northernmost Solomon Islands) are associated 
Porphyry Copper Assessment of Southeast Asia and Melanesia 37

with Eocene-Oligocene to early Miocene diorite and andesitic 

volcanic rocks. No deposits are known on Vanuatu; however, 

the western belt of late Oligocene to middle Miocene volcanic 

rocks that formed part of the relict Vitiaz Arc prior to subduction reversal contains hydrothermally altered, chalcopyritebearing, fault-controlled, high-level late Miocene intrusions 

that may be associated with porphyry copper systems (Vanuatu 

Department of Geology, Mines, and Water Resources, 1995). 

In Fiji, major porphyry copper and epithermal gold deposits 

are associated with the mature arc (12–7 Ma) and early rifting 

stage (7–3 Ma) tholeiitic to calc-alkalic rocks (Fiji Ministry of 

Lands and Mineral Resources, 2010). In the Namosi district 

of Viti Levu, Fiji, more than 15 major porphyry copper and 

gold prospects have been explored since the early 20th century 

(Imai and others, 2007).

Other Areas

Timor Leste (East Timor) (Based on contributions 

of Norberta Soares da Costa)

No magmatic-arc rocks have been delineated by mapping 

in Timor Leste. Copper occurs in three areas as chalcopyrite 

associated with ophiolite sequences, as stringers in serpentinite, and as native copper. These occurrences have not been 

fully evaluated; however, on the basis of available geologic 

information, Timor Leste does not appear to be permissive 

for porphyry copper deposits. Pending changes in the Mining 

Law may attract foreign investment in exploration for base 

and precious metals resulting in better characterization of the 

country’s resource potential.

Grade and Tonnage Models

The grade and tonnage models for porphyry copper 

deposits in Singer and others (2008) were used for the simulation of undiscovered resources in Southeast Asia. Available 

models include a global general porphyry Cu-Au-Mo model 

based on 422 deposits, a Cu-Au subtype model based on 115 

deposits, a Cu-Mo subtype model based on 51 deposits, and a 

Cu subtype based on the 256 deposits that do not fit the other 

subtypes. If known deposits were present in a tract, grades 

and tonnages of deposits within the tracts were tested against 

global models using statistical tests (t-test or analysis of variance (ANOVA)). At the 1-percent screening level adopted 

for this study, the assessment team determined that the global 

porphyry Cu-Au subtype model was acceptable for most of 

the tracts (table 6). For permissive tracts that lack identified 

resources for statistical tests, geologic rationale was used to 

select the appropriate model (table 6). Most of the porphyry 

copper deposits of Southeast Asia fit the Cu-Au subtype 

model, evenly distributed above and below the median 

tonnage for the model (see figure 14). For many deposits, 

byproduct metal grades are not reported. Statistical tests for 

silver grades, where available, indicated that neither the general, nor the Cu-Au subtype model were rejected for any tract. 

For a comparison of assessment results using different grade 

and tonnage models, see appendix L (table L7, fig. L3).

The Assessment Process

Several workshops were held between CCOP and USGS 

authors, where CCOP representatives presented country 

reports, provided data, and participated in tract delineation 

and estimation of undiscovered resources. Project workshops 

were held in Bangkok, Thailand (2003, 2004); Kunming, 

China (2005); and Busan, South Korea (2010). Preliminary 

results from the early workshops were updated for the 2010 

meeting and refined after internal USGS reviews. Brief 

biographies of assessment team members are included in 

appendix X.

Estimates of Numbers of Undiscovered Deposits

The assessment team evaluated the available data and 

made individual, subjective estimates of the numbers of 

undiscovered porphyry copper deposits using expert judgment. Estimates are expressed in terms of different levels of 

certainty. Estimators are asked for the least number of deposits 

of a given type that they believe could be present at a three 

specified levels of certainty (90 percent, 50 percent, and 10 

percent). For example, on the basis of all the available data, 

a team member might estimate that there was a 90-percent 

chance (or better) of at least 1, a 50-percent chance of at least 

3, and a 10-percent chance of at least 5 undiscovered deposits 

in a permissive tract. The individual estimates were discussed 

as a group, and a single team estimate was agreed upon for 

each tract. The estimates are converted to a mean number 

of deposits and standard deviation based on an algorithm 

developed by Singer and Menzie (2005). The algorithm can 

be described by the following general equations to calculate 

a mean number of deposits (λ) and a standard deviation (sx) 

based on estimates of numbers of undiscovered deposits 

predicted at different quantile levels27 (N90=90-percent level, 

N50=50-percent level, and so on):

λ = 0.233 N90+ 0.4 N50+ 0.225 N10+ 0.045 N05+ 0.03 N01 (1)

sx = 0.121 − 0.237 N90 − 0.093 N50 + 0.183 N10 + 0.073 N05 

+ 0.123 N01 (2)

These equations were programmed in a simple spreadsheet to allow the team to quickly evaluate estimates. The 

spread in the number of deposits associated with the 90th 

percentile to the 10th percentile or 1 percentile reflects uncer27 To use the equation in cases where three non-zero quantiles (90-50-10) 

are estimated, use the N10 values for N05 and N01; where four quantiles (90-50-

10-5) are estimated, use the N05 value for N01.
Table 6. Statistical test results, porphyry copper assessment, Southeast Asia and Melanesia. [Pooled t-test results assuming equal variances; ANOVA tests used for tracts with a single deposit; p>0.01 indicates that the deposits in the tract are not significantly different fr1-percent level; p<0.01 indicates that the deposits in the tract are significantly different from those in the model at the 1-percent level, and therefore, the tract fails the selected titalic font) and the model is inappropriate for the assessment. -, no data; tests for silver, where reported, were not rejected for either model] Tons Cu Mo Au Tons Cu Mo Au 142pCu7021 Sukhothai 1 0.92 0.72 - 0.82 0.82 0.76 - 0.25 Cu-Au Deposit gr

support ei

142pCu7022 Malaysia 0 --- - --- - Cu-Au Geologic r

142pCu7023 Mekong Delta 0 --- - --- - Cu-Au-Mo Default to 

142pCu7024 Wuntho-Popa 1 0.19 0.73 - - - - - - Cu-Au-Mo ANOVA r

142pCu7020 Sumatra Island 1 0.54 0.02 0.62 - - - - - Cu-Au-Mo ANOVA r

142pCu7025a Sunda Banda Arc 0 --- - --- - Cu-Au Geologic r

142pCu7025b Sunda Banda Arc 1 0.2 0.97 - 0.54 0.13 0.99 - 0.82 Cu-Au Geologic r

model 142pCu7025c Sunda Banda Arc 0 --- - --- - Cu-Au Geologic r

142pCu7026 West Sulawesi 0 - - - - - - - - Cu-Au Geologic r

142pCu7027 North Sulawesi-Sangihe 2 0.48 0.36 - 0.84 0.55 0.4 - 0.07 Cu-Au Geologic r

142pCu7019 Central Kalimantan 1 0.9 0.82 0.012 0.37 0.98 0.85 0.16 0.67 Cu-Au ANOVA r

model 142pCu7201 Ambon Arc, Central Molucca Islands 0 - - - - - - - - Cu-Au Geologic r

142pCu7202 Halmahera Arc, North Molucca Islands 1 0.46 0.56 - 0.72 0.49 0.55 - 0.71 Cu-Au Geologic r

model

142pCu7205 Moon-Utawa-Ular Merah Areas 0 - - - - - - - - Cu-Au Geologic r

142pCu7204 Rotanburg-Taritatua Area 0 --- - --- - No assessment 

142pCu7203 Western Medial New Guinea Magmatic Belt 1 0.06 0.48 - 0.28 0.03 0.52 - 0.39 Cu-Au Deposit gr

support ei

009pCu7203a 3 0.6 0.34 0.92 0.53 0.72 0.39 0.21 0.4 Cu-Au Deposit gr

support ei

009pCu7203b 3 0.84 0.71 0.99 0.21 0.98 0.76 0.07 0.93 Cu-Au Deposit gr

support ei

009pCu7205 Maramuni Arc 1 0.32 0.68 0.27 0.6 0.23 0.72 0.9 0.66 Cu-Au Deposit gr

support ei

009pCu7206 Miocene Alkaline Rocks, Southeastern Papua 

New Guinea

0 --- - --- - Cu-Au Geologic r

142pCu7208 Inner Melanesian Arc Terranes I, Indonesia 0 --- - --- - No assessment 

009pCu7208 Inner Melanesian Arc Terranes II, Papua New 

Guinea 

0 --- - --- - No assessment 

009pCu7209 Inner Melanesian Arc (New Britain) 1 0.91 0.69 0.49 0.99 0.68 0.58 <0.001 Cu-Au-Mo Default to 

009pCu7207, 009pCu7210

Outer Melanesian Arc -Papua New Guinea and 

Melaneisa 

5 0.76 0.55 0.6 0.46 0.93 0.55 0.2 0.45 Cu-Au subtype Deposit gr

support ei

Code Tract name Nknown Porphyry Cu-Au-Mo model Porphyry Cu-Au subtype model Model selected 

Eastern Medial New Guinea Magmatic Belt

Indochina peninsular area

Indonesian Islands area

New Guinea Island, Indonesia and Papua New Guinea and other Papua New Guinea islands

<0.001
Summary of Probabilistic Assessment Results 39

28 Amount of metal at the 0.5 quantile; 50 percent chance of occurrence of 

that amount of metal or more based on simulation for the estimated numbers 

of undiscovered deposits.

tainty; large differences in number suggest great uncertainty. 

The mean number of deposits for the permissive tract, or the 

numbers associated with a given probability level, reflect 

favorability. Another useful parameter for reporting uncertainty associated with an estimate is the coefficient of variation (Cv), defined as:

Cv = sx / λ. (3)

The coefficient of variation is often reported as percent 

relative variation (100 × Cv).

The final team estimates reflect both the uncertainty 

in what may exist and the favorability of the tract (Singer, 

1993). The estimates are combined with appropriate grade 

and tonnage models in a Monte Carlo simulation using 

the EMINERS computer program (Bawiec and Spanksi, 

2012; Duval, 2012), based on the original Mark 3 computer 

program described by Root and others (1992), to provide a 

probabilistic estimate of amounts of resources that could be 

associated with undiscovered deposits. No economic filters 

are applied, so results must be viewed with the realization 

that deposits, if discovered, might not be developed.

The rationales for individual tract estimates are discussed in the appendixes. In some cases, the number of 

significant porphyry copper prospects within a tract served 

as the primary basis for estimates at the 90th and 50th quantiles. Particular weight was given to prospects classified as 

porphyry copper-related in published literature and recent 

exploration reports. The location, number, deposit type, and 

relative importance of other prospects also were considered. 

Recent literature, company Web sites, and technical reports 

for exploration projects were checked for descriptions of 

geology, mineralogy, deposit type, rock alteration, and 

sampling results to evaluate the likelihood that a prospect is 

associated with a porphyry copper system similar to those in 

the grade and tonnage models. In some cases, team members 

provided information about prospects based on personal 

observations from site visits.

The level of exploration in different regions was a factor 

in making estimates. In thoroughly explored areas, such as 

Papua New Guinea and parts of Indonesia that have welldocumented mineral occurrence databases, prospects were 

ranked informally using a numeric scale:

5: deposit (identified resources),

4: prospect in Singer and others (2008), or <16,000 t of 

ore established by drilling,

3: drilled, with >20 m of 0.2 percent copper,

2: drilled, or trenched, with <20 m or <0.2 percent copper; past or ongoing exploration, and

1: stream sediment, magnetic anomaly, or mineralized 

structural trend.

The occurrence of prospects ranked as 3 or 4 typically 

contributed to estimates at the N90 quantile based on reasoning that further exploration of some proportion of these 

prospects was likely to lead to delineation of a deposit. The 

total numbers of prospects, and prospects ranked as 2 or 3, 

as well as the level of exploration throughout the tract area 

contributed to the other quantile estimates. In addition, the 

distribution of reported copper and gold occurrences of 

unknown type and placer gold workings were considered as a 

factor in making estimates. In less thoroughly explored areas, 

and areas with poor documentation of mineral occurrences, 

such methods could not be used, and the spread in estimates 

and high coefficients of variations associated reflect the 

team’s uncertainty (table 7). Other considerations include the 

fact that much of Southeast Asia and Melanesia is heavily 

vegetated, has rugged and steep terrain, and that much of 

the area has been inaccessible to exploration for 20 years or 

more because of political turmoil, years of war and social 

conflicts in some areas, environmental concerns, and local 

opposition to mineral development.

Final team estimates of undiscovered deposits are summarized in table 7, along with statistics that describe mean 

numbers of undiscovered deposits, the standard deviation 

and coefficient of variation associated with the estimate, 

the number of known deposits, and the implied deposit 

density for each tract. In two cases, separate estimates 

were made for different parts of a tract because the team 

concluded that the expected distribution of undiscovered 

deposits varied throughout the tract. Therefore, separate 

estimates are reported for sub-tracts for the Sunda-Banda 

Arc (142pCu7025) and for the Eastern Medial New Guinea 

magmatic belt (009pCu7203). For many of the other tracts, 

geographically distinct tract segments or areas are described, 

but the probabilistic assessment applies to the entire tract.

 Permissive tracts primarily are based on mapped geology. Some tracts necessarily are small because the mapped 

geology reflects the surface exposures of parts of complex or 

fragmented arc systems; many of the islands are small, and 

permissive rocks that comprise arcs, such as the Ambon Arc, 

extend offshore. The assessment is limited to onshore areas 

of Southeast Asia and Melanesia.

The assessment predicts a mean of 89 undiscovered 

porphyry copper deposits in all tracts, or about four times as 

many deposits as already have been discovered and welldelineated (23 known deposits).

Summary of Probabilistic Assessment 

Results

Simulation results for mean and median28 estimates 

of contained copper and gold in undiscovered deposits are 

reported in table 8 along with total identified resources in 

known deposits in each tract. Identified resources are based on 

total production, if any, and published data for measured, indicated, and inferred reserves and resources at the lowest cutoff 
40 Porphyry Copper Assessment of Southeast Asia and Melanesia

grade reported. Identified resources may include substantial 

amounts of metal that already have been produced.

About one-third of the 22 permissive tracts contain 

no identified resources. Some tracts may contain porphyry 

copper systems that are currently, or have been, explored, 

but no reliable grade and tonnage estimates are yet 

available; these were considered as significant prospects 

with a high probability of representing deposits like those in 

the grade and tonnage models.

Simulation results are reported at selected quantile 

levels, along with the mean amount of metal, the probability 

of the mean, and the probability of no metal. The amount of 

metal reported at each quantile represents the least amount 

of metal expected. The quantile results represent ranked data 

from the 4,999 Monte Carlo simulations. The quantiles are 

linked to each tract simulation and, therefore, should not 

be added. Mean estimates, however, can be added to obtain 

total amounts of metal and mineralized rock in undiscovered 

deposits. Mean estimates of copper, gold, molybdenum, 

silver, and rock for each tract are listed in table 8. Note that 

byproduct metals in deposits with reliable tonnages and 

copper grades frequently are not reported (table 5).

Discussion

This probabilistic assessment of the metal resources 

associated with undiscovered porphyry copper deposits 

in Southeast Asia indicates that significant amounts of 

additional resources may be present (table 8). The mean 

estimate of undiscovered copper resources in the study 

area (~288 Mt) is about 3.5 times the amount of copper 

present in identified resources (84 Mt). However, these 

resources, if present, may be inaccessible or uneconomic. 

Results should be interpreted with caution pending 

Figure 14. Plot of global tonnage and grade models for porphyry copper deposits, Cu-Au subtype (Singer and others, 2008) showing 

Southeast Asia porphyry Cu-Au deposits included in the model relative to deposits in other parts of the world. A, Tonnage. B, Copper 

grade. Note the spread of tonnages and grades above and below the median tonnage (that is, proportion of deposits = 0.5).

Kodu

Mamut

Phu Kam

Arie

Kaputusan

Star Mt. Futik

Star Mt. Nong River

Koloula 

Tapadaa

Waivaka

Grasberg Frieda River

Namosi

Ok Tedi

Wafi-Golpu

Tombulilato

Panguna

Batu Hijau

Yandera

Global Cu-Au model

Southeast Asia

EXPLANATION

Proportion of deposits

0.5

0.6

0.7

0.8

0.9

1

0

0.1

0.2

0.3

0.4

Million metric tons

1 10 100 1,000 10,000 100,000

A

Ore tonnage, in million metric tons
Considerations for Users of this Assessment 41

application of economic filters to evaluate what part of 

the estimated undiscovered resources might be economic 

under various conditions, such as mining method, 

metal prices, and capital development costs. Identified 

resources are compared with mean and with median 

estimates of undiscovered copper resources by area and 

by tract in figures 15 A–D.

Assessment results are summarized on a regional 

basis in figure 16. These data indicate that the 

Indochina Peninsula and Indonesian and Malaysian 

islands, especially Kalimantan (fig. 16C), may contain 

significantly more copper and gold in undiscovered 

porphyry copper deposits. Papua New Guinea and the 

Melanesian island nations also are expected to contain 

undiscovered resources, but the ratios of undiscovered 

resources to identified resources are much lower for 

these areas. One possible explanation for the lower ratios 

is that the latter areas have been more fully explored and 

have a longer history of mine development.

Considerations for Users of this 

Assessment

Assessment products represent a synthesis of current, 

readily available information. Ideally, assessments are 

done on a recurring basis, at a variety of scales, because 

available data change over time. This assessment is based 

on the descriptive and grade and tonnage data contained in 

published mineral-deposit models. Data in the grade and 

tonnage models represent average grades of each commodity 

of possible economic interest and tonnages based on the 

total of production, reserves, and resources at the lowest 

Frieda River

Panguna

Batu Hijau

Namosi

Simuku

Monywa

Yandera

Kaputusan

Arie

Kodu

Tangse

Koloula

Wafi-Golpu

Waivaka

Ok Tedi, Phu Kham

Tombulilato

Grasberg

Star Mt. Futik, Tapadaa

Star Mt. Nong River

Mamut

Global Cu-Au model

Southeast Asia

EXPLANATION

Copper grade, in percent

0.0 0.2 0.4 0.6 0.8 1.0 1.2

Proportion of deposits

0.5

0.6

0.7

0.8

0.9

1

0

0.1

0.2

0.3

0.4

B

Figure 14.—Continued
42 Porphyry Copper Assessment of Southeast Asia and Melanesia

Table 7. Estimates of numbers of undiscovered porphyry copper deposits in Southeast Asia. 

[NXX, estimated number of deposits associated with the xxth percentile; Nund, expected number of undiscovered deposits; s, standard deviation; Cv%, coefficient 

of variance; Nknown, number of known deposits in the tract that are included in the grade and tonnage model; Ntotal, total of expected number of deposits plus 

known deposits; area, area of permissive tract in square kilometers; deposit density, reported as the total number of deposits per 100,000 km2. Nund , s, and Cv% are 

calculated using a regression equation (Singer and Menzie, 2005). -, no estimate made] 

Appendix Coded_Id Tract Name

Consensus undiscovered 

deposit estimates Summary statistics Tract

Area

(km2

)

Deposit

density 

(Ntotal/100k

km2)

Estimated 

/known 

N deposits 90 N50 N10 N05 N01 Nund s Cv

% Nknown Ntotal

Indochina peninsular area 

A 142pCu7021 Sukhothai 3 8 26 26 26 12.0 8.5 73 1 13.0 354,260 4 12.0

B 142pCu7022 Malaysia 1 2 6 6 6 2.8 2 70 1 3.8 60,000 6 -

C 142pCu7023 Mekong Delta 1 6 16 16 16 7.4 5.4 73 0 7.4 91,220 8 -

D 142pCu7024 Wuntho-Popa 0 1 5 9 9 2.2 2.7 120 1 3.2 45,260 7 2.2

Area total 24.4 3.0 27.4

Indonesian Islands area

E 142pCu7020 Sumatra Island 1 5 13 13 13 6.1 4.3 71 1 7.1 131,030 5 6.1

F 142pCu7025a Sunda Banda Arc 1 2 8 8 8 3.4 2.7 80 0 3.4 61,200 6 -

142pCu7025b 1 4 10 10 10 4.8 3.3 68 1 5.8 22,550 26 4.8

142pCu7025c 0 0 2 2 3 0.6 1 160 0 0.6 5,670 11 -

G 142pCu7026 West Sulawesi 0 1 2 3 3 1.1 0.98 91 0 1.1 60,270 2 -

H 142pCu7027 North Sulawesi-Sangihe 1 2 6 6 6 2.8 2 70 2 4.8 20,330 24 1.4

I 142pCu7019 Central Kalimantan 3 8 30 30 30 13.0 10 78 1 14 144,580 10 13.0

J 142pCu7201 Ambon Arc, Central Molucca 

Islands

0 1 2 2 2 1.0 0.79 79 0 1.0 1,540 65 -

K 142pCu7202 Halmahera Arc, North Molucca 

Islands

0 1 3 6 6 1.5 1.8 110 1 2.5 12,250 20 1.5

Area total 34.3 6.0 40.3

New Guinea Island, Indonesia and Papua New Guinea and other Papua New Guinea Islands

L 142pCu7205 Moon-Utawa-Ular Merah Areas 0 1 2 2 2 1.00 0.79 79 0 1.0 13,580 7 -

M 142pCu7203 Western Medial New Guinea 

Magmatic Belt

1 3 10 10 10 4.43 3.40 77 1 5.4 13,270 41 4.4

N 142pCu7204 Rotanburg-Taritatua Area - - - - - - - - - - 9,370 - -

O 009pCu7203a Eastern Medial New Guinea 

magmatic belt

0 1 4 4 4 1.60 1.54 97 3 4.6 14,230 32 0.5

009pCu7203b 1 4 16 16 16 6.63 5.58 84 3 9.6 53,220 18 2.2

P 009pCu7205 Maramuni Arc 0 2 8 8 8 3.20 3 93 1 4.2 38,970 11 3.2

Q 009pCu7206 Miocene Alkaline Rocks, 

Southeastern Papua New Guinea

0 0 1 1 3 0.36 0.75 210 0 0.4 1,640 24 -

R 142pCu7208 Inner Melanesian Arc Terranes I, 

Indonesia 

- - - - - - - - - - 7,720 - -

S 009pCu7208 Inner Melanesian Arc Terranes II, 

Papua New Guinea 

- - - - - - - - - - 29,140 - -

T 009pCu7209 Inner Melanesian arc (New Britain) 1 2 4 4 4 2.23 1.2 54 1 3.2 17,990 18 2.2

U 009pCu7207 Outer Melanesian Arc I -

Papua New Guinea 

2 5 10 10 10 5.47 3 54 2 7.5 16,830 45 2.7

Area total 24.9 11.0 35.9

Melanesia

V 009pCu7210 Outer Melanesian arc II- Melanesia 1 5 10 10 10 5.2 3.2 61 3 8.2 38,180 21 1.7

Southeast Asia total 88.9 23.0 107.9
Considerations for Users of this Assessment 43

Table 8. Summary of simulations of undiscovered resources in porphyry copper deposits and comparison with identified copper and 

gold resources in porphyry copper deposits within each permissive tract , Southeast Asia.

[t, metric tons; Mt, million metric tons, -, not determined; NA, not applicable (only means are additive)]

Appendix Coded_Id Tract Name

Known 

copper 

resources (t)

Undiscovered copper 

resources Known 

gold 

resources 

(t)

Undiscovered gold 

resources Mean estimate

Mean 

estimate (t)

Median 

estimate (t)

Mean 

estimate 

(t)

Median 

estimate 

(t)

Undiscovered 

molybdenum 

resources (t)

Undiscovered 

silver 

resources (t)

Rock (Mt)

Indochina peninsular area 

A 142pCu7021 Sukhothai 1,171,200 37,000,000 24,000,000 44 2,700 1,900 210,000 12,000 7,400

B 142pCu7022 Malaysia 810,000 8,900,000 3,500,000 27 640 300 52,000 2,900 1,800

C 142pCu7023 Mekong Delta 0 28,000,000 16,000,000 0 710 380 790,000 9,200 5,700

D 142pCu7024 Wuntho-Popa 6,290,000 8,800,000 1,700,000 0 230 23 250,000 3,000 1,800

 Total for Indochina peninsula area 8,271,200 82,700,000 NA 71 4,280 NA 1,302,000 27,100 16,700

Indonesian Islands area

E 142pCu7020 Sumatra Island 900,000 23,000,000 13,000,000 0 600 300 640,000 7,800 4,800

F 142pCu7025a Sunda Banda Arc 0 10,000,000 4,200,000 0 770 350 59,000 3,500 2,100

142pCu7025b 7,216,000 15,000,000 8,000,000 574 1,100 650 91,000 5,000 3,100

142pCu7025c 0 2,100,000 0 0 150 0 12,000 690 420

G 142pCu7026 West Sulawesi 0 3,400,000 650,000 0 240 66 19,000 1,100 680

H 142pCu7027 North SulawesiSangihe

2,040,300 8,900,000 3,800,000 138 650 310 51,000 2,900 1,800

I 142pCu7019 Central Kalimantan 940,800 40,000,000 25,000,000 98 2,900 1,900 230,000 13,000 8,100

J 142pCu7201 Ambon Arc, Central 

Molucca Islands

0 3,100,000 660,000 0 230 65 18,000 1,000 620

K 142pCu7202 Halmahera Arc, North 

Molucca Islands

254,100 4,800,000 870,000 19 340 80 29,000 1,600 970

 Total for Indonesian Islands area 11,351,200 110,300,000 NA 829 6,980 NA 1,149,000 36,590 22,590

New Guinea Island, Indonesia and Papua New Guinea and other Papua New Guinea Islands

L 142pCu7205 Moon-Utawa-Ular 

Merah Areas

0 3,200,000 660,000 0 230 560 18,000 1,100 640

M 142pCu7203 Western Medial New 

Guinea Magmatic 

Belt

24,000,000 14,000,000 6,500,000 2,560 1,000 560 80,000 4,500 2,800

N 142pCu7204 Rotanburg-Taritatua 

Area

- - - - - - - - -

O 009pCu7203a Eastern Medial New 

Guinea Magmatic 

Belt

6,116,600 5,100,000 1,200,000 673 360 110 29,000 1,700 1,000

009pCu7203b 11,368,926 20,000,000 10,000,000 500 1,500 830 120,000 6,700 4,100

P 009pCu7205 Maramuni Arc 8,550,000 9,900,000 3,300,000 418 710 290 56,000 3,200 2,000

Q 009pCu7206 Miocene Alkaline 

Rocks, Southeastern 

Papua New Guinea

0 1,200,000 0 0 82 0 7,000 340 230

R 142pCu7208 Inner Melanesian Arc 

Terranes I, Indonesia 

- - - - - - - - -

S 009pCu7208 Inner Melanesian Arc 

Terranes II, Papua 

New Guinea 

- - - - - - - - -

T 009pCu7209 Inner Melanesian arc, 

New Britain 

720,000 8,500,000 3,200,000 12 210 62 230,000 2,700 1,700

U 009pCu7207 Outer Melanesian Arc 

I, Papua New Guinea

7,131,000 17,000,000 9,800,000 809 1,200 830 95,000 5,400 3,400

Total for New Guinea Area 57,886,526 78,900,000 NA 4,972 5,292 NA 635,000 25,640 15,870

V 009pCu7210 Outer Melanesian Arc 

II- Melanesia 

6,887,900 16,000,000 9,100,000 221 1,200 760 92,000 5,100 3,200

 Total for Southeast Asia 84,396,826 287,900,000 NA 6,093 17,752 NA 3,178,000 94,430 58,360
44 Porphyry Copper Assessment of Southeast Asia and Melanesia

Figure 15. Bar charts comparing known copper resources, mean, and median estimated copper resources in 

undiscovered porphyry copper deposits in Southeast Asia and Melanesia on a tract by tract basis. See table 4 for 

tract names and countries included. Values that plot on the base of the diagram indicate no resources. A, Indochina 

Peninsula. B, Western Indonesian Islands. C, New Guinea Island, Indonesia and Papua New Guinea. D, Melanesian 

Arcs, Papua New Guinea and Melanesia.

100,000

1,000,000

10,000,000

100,000,000

Sukhothai 142pCu7021 Malaysia 142pCu7022 Mekong Delta 142pCu7023 Wuntho-Popa 142pCu7024

Copper, in metric tons

Tract

Known copper resources

Mean estimate of undiscovered 

 copper resources

Median estimate of undiscovered 

 copper resources

EXPLANATION A, Indochina Peninsula
Considerations for Users of this Assessment 45

Figure 15.—Continued

100,000

1,000,000

10,000,000

100,000,000

Copper, in metric tons

Tract 

Sumatra Island

142pCu7020

Sunda Banda Arc

142pCu7025a

Sunda Banda Arc

142pCu7025b

Sunda Banda Arc

142pCu7025c

West Sulawesi

142pCu7026

North SulawesiSangihe 142pCu7027

Central Kalimantan

142pCu7019

Ambon Arc

142pCu7201

Halmahera Arc

142pCu7202

Known copper resources

Mean estimate of undiscovered 

 copper resources

Median estimate of undiscovered 

 copper resources

EXPLANATION

B, Western Indonesian Islands
46 Porphyry Copper Assessment of Southeast Asia and Melanesia

Figure 15.—Continued

100,000

1,000,000

10,000,000

100,000,000

Moon-UtawaUlar Merah

142pCu7205

W Medial New 

Guinea

142pCu7203

E Medial New 

Guinea

009pCu7203a

E Medial New 

Guinea

009pCu7203b

Maramuni Arc

 009pCu7205

Alkaline SE Papua 

New Guinea

009pCu7206

Tract 

Copper, in metric tons

Known copper resources

Mean estimate of undiscovered 

 copper resources

Median estimate of undiscovered 

 copper resources

C EXPLANATION , New Guinea Island, Indonesia and Papua New Guinea
Considerations for Users of this Assessment 47

Figure 15.—Continued

100,000

1,000,000

10,000,000

100,000,000

, 

Known copper resources

Mean estimate of undiscovered 

 copper resources

Median estimate of undiscovered 

 copper resources

EXPLANATION

Tract 

Inner Melanesian Arc

009pCu7209

Outer Melanesian Arc I 

009pCu7207

Outer Melanesian Arc II 

009pCu7210

Copper, in metric tons

D, Melanesian Arcs, Papua New Guinea and Melanesia
48 Porphyry Copper Assessment of Southeast Asia and Melanesia

Figure 16. Bar charts comparing known and mean resource estimates on a regional basis. A, Copper. B, Gold.

Known copper resources

Mean estimate of undiscovered 

 copper resources

EXPLANATION

1,000,000

10,000,000

100,000,000

1,000,000,000

Indochinese Peninsula Indonesian Islands New Guinea Island Melanesian Arcs

Area

Copper, in metric tons

A

Figure 16A
Considerations for Users of this Assessment 49

Figure 16.—Continued

1

10

100

1,000

10,000

Indochina Peninsula Indonesian Islands New Guinea Island Melanesian Arcs

Area

Known gold resources

Mean estimate of undiscovered 

 gold resources

EXPLANATION

Gold, in metric tons

Figure 16B
50 Porphyry Copper Assessment of Southeast Asia and Melanesia

cutoff grade for which data were available when the model 

was constructed. The present-day economic viability of the 

deposits used to construct the models varies widely, so care 

must be exercised when using the results of this assessment 

to answer questions that involve economics. Furthermore, these 

estimates are of numbers of deposits that are likely to exist, 

not necessarily those likely to be discovered (Singer, 2007b). 

Prospects, revealed by past or current exploration efforts, may 

become deposits when further drilling and characterization takes 

place. These probable deposits are treated here as undiscovered 

deposits, albeit ones with a high degree of certainty of existence. 

The mineral industry explores for extensions of identified 

resources, as well as for greenfields projects in new exploration 

areas. Extensions of identified resources are not estimated in this 

assessment, although they are commonly a substantial part of 

newly discovered copper resources each year. This assessment 

considers the potential for concealed deposits within 1 km of the 

surface. Very high-grade deposits may be exploited at greater 

depths. However, exploration for, and exploitation of such 

deposits may be so expensive that deposits, if present, may not be 

discovered in the near term. If they are discovered, the costs and 

logistics related to mining a deeply buried porphyry deposit might 

prohibit their development into mines given current or near-term 

metal prices and technology.

Permissive tracts are based on geology, irrespective 

of political boundaries; therefore, tracts may cross country 

boundaries or include lands that already have been developed for 

other uses, or have been withdrawn from mineral development 

as protected areas. The tracts are constructed at a scale of 

1:1,000,000 and are not intended for use at larger scales.

Acknowledgments

This joint USGS-CCOP project has a long history, with 

many people involved at different times. Drs. Klaus Schulz 

and Joseph Briskey initiated the USGS project and participated 

in the first two workshops. Dr. Steve Peters coordinated and 

led the original assessment activities, prepared draft reports, 

and represented the USGS at many CCOP meetings. Dr. Jack 

Medlin, as USGS representative to CCOP, facilitated joint project 

activities. Kathleen Johnson, USGS Mineral Resources Program 

Coordinator, provided constant support during the life of the 

project. Walter Bawiec participated in workshops and provided 

GIS support in the early stages of the project. Sewit Yenie, John 

Wallace, Paul Schruben, Pam Dunlap, Deb Briggs, and Mukul 

Sonwalker provided technical support. William Moore assisted 

with preparation of final figures.

CCOP member countries generously participated in 

assessment meetings and provided data that would not have been 

available otherwise. The assessment team would like to thank 

past and present CCOP directors and staff, especially Dr. Nguyen 

Nhu Trung, CCOP Geo-Resources Sector Coordinator, and Ms. 

Sansanee Wudhiwanich for their assistance in completing the 

project. The Geological Survey of China hosted the Kunming 

meeting, the Geological Survey of Thailand hosted Dr. Peters in 

Bangkok, and the Geological Survey of South Korea (KIGAM) 

hosted the final workshop in Busan in 2010.

USGS colleagues David John, Peter Vikre, Byron Berger, 

Larry Drew, Tom Light, and Mark Mihalaksy served on 

assessment oversight committees to vet assessment results. Steve 

Peters provided data, expertise, and reviews of preliminary drafts 

of some assessment tracts.

Technical reviews of the manuscript were provided by 

David John and Klaus Schulz.

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(Also available at http://www.ngdc.noaa.gov/mgg/global/

relief/ETOPO1/docs/ETOPO1.pdf.)

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report: accessed February 10, 2010, at http://www.

arcexploration,com.au/March2009Quarterly.html.

Arculus, R.J., 2003, Use and abuse of the terms calc-alkaline 

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56 Porphyry Copper Assessment of Southeast Asia and Melanesia
Appendixes A–X 57

Appendixes A–X
58 Porphyry Copper Assessment of Southeast Asia and Melanesia 

Appendix A. Porphyry Copper Assessment for Tract 142pCu7021, 

Sukhothai—China, Myanmar, Thailand, Lao People’s Democratic Republic, Cambodia, and Vietnam

By Steve Ludington1, Wudhikarn Sukserm2, Jane M. Hammarstrom3, and Gilpin R. Robinson, Jr.3, with contributions from Pairatt Jarnyaharn2

, Pichai Otarawanna2, Boonsong Yokartt2, Sompob Wongsomasak2, Nguyen 

Van Quy4

, Sieng Sotham5, I.M. Sim5, and Takehiro Sakimoto2

Deposit Type Assessed: Porphyry copper, copper-gold subtype

Descriptive model: Porphyry copper (Berger and others, 2008; Cox, 1986; John and others, 2010)

Grade and tonnage model: Porphyry copper, Cu-Au subtype (Singer and others, 2008)

Table A1 summarizes selected assessment results.

Location

The tract extends for about 3,500 km from central Yunnan province in China in two belts, a western belt that runs through 

Thailand, northern Lao People’s Democratic Republic (Laos), and western Cambodia, and an eastern belt that trends southeast 

through much of the length of Vietnam and Lao People’s Democratic Republic, including some areas in northern Cambodia 

(fig. A1).

Geologic Feature Assessed

Carboniferous through Triassic island and continental arcs formed by subduction of Paleotethyan oceanic crust (the Loei 

and Truong Son volcanic arcs).

1

U.S. Geological Survey, Menlo Park, California, United States.

2

Royal Thai Government Department of Mineral Resources, Bangkok, 

Thailand. 3

U.S. Geological Survey, Reston, Virginia, United States.

4

Department of Geology and Minerals of Vietnam, Hanoi, Vietnam.

5

Department of Geology and Mines, Phnom Penh, Cambodia.

Table A1. Summary of selected resource assessment results for tract 142pCu7021, Sukhothai—China, Myanmar, Thailand, Lao 

People’s Democratic Republic, Cambodia, and Vietnam.

[km, kilometers; km2, square kilometers; t, metric tons]

Date of 

assessment

Assessment depth 

(km)

Tract area 

(km)

Known copper 

resources (t)

Mean estimate of 

undiscovered copper 

resources (t)

Median estimate of 

undiscovered copper 

resources (t)

February 2010 1 354,260 1,171,200 37,000,000 24,000,000
Appendix A—Tract 142pCu7021 59

Delineation of the Permissive Tract

Tectonic Setting

The plate tectonic history of Southeast Asia is still a 

matter of contention. The widespread Carboniferous through 

Triassic magmatic rocks that define the Sukhothai tract 

are, however, all related to the amalgamation of a series 

of microcontinents that were rifted off Gondwana and 

drifted north as a result of subduction of the Paleotethyan 

ocean (Wakita and Metcalfe, 2005). The Sukhothai island 

arc system, as defined by Sone and Metcalfe (2008), is the 

result of the eastward subduction of Paleotethyan ocean 

floor beneath Indochina that began in the latest Carboniferous. This arc, which ended in Late Triassic time when the 

Sibumasu terrane (fig. 5A) collided with Indochina, constitutes the western part of the tract. In northern Thailand and 

northern Lao People’s Democratic Republic, the Loei Belt 

consists of similar Permian and Triassic volcanic and plutonic rocks, although the Loei Belt is exposed at a somewhat 

deeper erosion level (Royal Thai Government Department 

of Mineral Resources, 2010). The Loei Belt also contains 

Silurian-Devonian volcanic and volcaniclastic rocks, but 

these are not part of the Sukhothai system (Koshitanont and 

others, 2008). Further east, the Truong Son igneous belt, in 

Lao People’s Democratic Republic and Vietnam, consists of 

Permian and Triassic intermediate and felsic volcanic and 

plutonic rocks, mostly calc-alkaline, with a few peraluminous granites (Hoa and others, 2008).

Geologic Criteria

The digital geologic map used to select the rocks that 

define the permissive tract is a compilation of digital maps 

of each of the countries involved, Myanmar, Lao People’s 

Democratic Republic, Cambodia, Thailand, Vietnam, and 

China (Yunnan) that were prepared by a group at the University of Tasmania (Khin Zaw and others, 1999). These maps 

were compiled from a number of sources of varying quality 

and scale. Geological studies of many areas, particularly near 

national borders, have been hampered by difficult terrain, 

lack of infrastructure, wars and insurgencies, widespread land 

mines and unexploded bombs, and freelance bandits (Burret, 

1999).

The digital geologic map does not always reflect the most 

recent radiometric age determinations or petrologic studies on 

the rocks in the tract, whose ages are not always accurately 

known. Many of the rocks have not been dated precisely 

nor have they been studied petrologically. Hence, it is likely 

that some rocks that are not permissive for porphyry copper 

deposits are included, either because they are not actually 

Carboniferous or Permo-Triassic in age, are peraluminous, or 

are otherwise not strictly part of the volcanic-arc assemblage. 

Ultramafic rocks, peraluminous granites, and widespread areas 

of dominantly silicic volcanism are excluded, but overall, the 

team chose to err on the side of inclusion.

To define the area included in the permissive tract, igneous map units were classified as permissive or nonpermissive, based on the geologic criteria described above, that is 

calc-alkaline and alkaline volcanic and plutonic rocks of Late 

Carboniferous, Permian, and Triassic ages (table A2). A 10-km 

buffer was applied to the polygons for permissive plutonic 

rocks, and a 2-km buffer was applied to permissive volcanicrock polygons. This expanded the area of the tract to include 

all known porphyry copper deposits and significant associated 

prospects and accounts for uncertainties in the cartographic 

position of mapped boundaries, as well as possible unexposed 

or unmapped permissive rocks.

After buffering, the limited geophysical and geochemical 

information was examined to be sure that any other evidence 

of unmapped permissive rocks or hydrothermal systems was 

included. A smoothing routine was applied to the resulting 

polygons, and the tract was trimmed by any terrane-bounding 

faults. The resulting tract was compared to several maps that 

delineate parallel belts of granitoids of contrasting composition in Southeast Asia to ensure that the tract was restricted 

to the I-type calc-alkaline rocks; these maps include those of 

Cobbing and others (1992) and Putthapiban (2002). In addition, a newly compiled 1:1,000,000-scale digital geologic map 

of Thailand provided by the Royal Thai Government Department of Mineral Resources (written commun., 2010) was used 

to refine that part of the tract in Thailand. Finally, any areas 

that are intruded by post-Triassic intrusions were excluded, 

and the resulting tract shapefile was clipped to the shoreline 

to eliminate undersea areas (U.S. Department of State, 2009). 

The tract is shown in figure A1.

Known Deposits

The Phu Kham porphyry copper-gold deposit (table A3) 

in the Lao People’s Democratic Republic is emplaced in a 

sequence of Permian mixed volcanic and clastic rocks about 

120 km north of Vientane, the Lao capital. The deposit is 

90-percent owned by PanAust, an Australian mining company, 

and it went into production as an open-pit mine in April 2008, 

with a scheduled mine life of more than 12 years (PanAust, 

2010). Few geologic details have been published, but Kamvong (2006) reported that the mineralization is associated with 

a series of intermediate-composition granitoid rocks whose 

zircons have been dated by U-Pb methods at about 292 Ma 

(Manaka and others, 2008).

The present resource (measured + indicated + inferred) at 

Phu Kham is 183,000,000 tons at 0.64 percent copper, 0.24 g/t 

gold, and 2.0 g/t silver (no molybdenum reported) at a cutoff 

grade of 0.3 percent copper. The resource is open to the north 

and beneath the floor of the designed pit and further development drilling continues (PanAust, 2010). A slightly larger 

resource (277,000,000 tons at 0.51 percent copper) based on a 

lower cutoff grade was reported by Singer and others (2008).

Several other undeveloped copper-gold prospects, including one called Pha Nai, are present within the PanAust concession within 20 km of Phu Kham.
60 Porphyry Copper Assessment of Southeast Asia and Melanesia 

Map unit Map symbol Lithology Age range

16-Granitoid plutons (Laos) gMz Granite, tonalite, and 

granodiorite

Triassic to Jurassic

18-Granitoid plutons (Laos) gPz3 Granodiorite and monzogranite Permian to Triassic

19-Granitoid plutons (Laos) gPz3 Granodiorite and monzogranite Carboniferous

240-Intrusive rocks (Vietnam) R123-4 Granite, granophyre, and 

granodiorite

Late Paleozoic to Early Mesozoic

250-Intrusive rocks (Vietnam) U2-4

255-Intrusive rocks (Vietnam) d1-4

391-Intrusive rocks (Yunnan) rn4-rn52 Monzonitic granite Late Paleozoic to Mesozoic

403-Intrusive rocks (Yunnan) rx41 K-feldspar granite Early late Paleozoic

404-Intrusive rocks (Yunnan) rn41 Monzonitic granite Early late Paleozoic

405-Intrusive rocks (Yunnan) rd41 Granodiorite Early late Paleozoic

834-Granite (Thailand) gr Granite, granodiorite, and 

granite

Paleozoic to Mesozoic

7-Shallow shelf sequence (Laos) Pz3 Volcanosedimentary rocks Permian-Triassic

12-Volcanosedimentary 

sequence (Laos)

Pz1 Volcanosedimentary rocks Cambrian to Silurian (some are 

Permian to Triassic)

82-Stratified rocks (Yunnan) P21 Basalt with pyroclastic rocks Upper Permian

83-Stratified rocks (Yunnan) P2 Basalt, carbonate rocks, clastic 

rocks

Upper Permian

113-Stratified rocks (Vietnam) T2 Acid volcanics Middle Triassic

132-Stratified rocks (Vietnam) C-P Intermediate volcanics Carboniferous to Permian

515-Dacite and tuffs 

(Cambodia)

T2 Dacite and tuffs Middle Triassic

517-Rhyolite, dacite, tuffs 

(Cambodia)

T1-2 Rhyolite, dacite, and tuffs Middle Triassic

520-Volcanoclastics (Cambodia) T Volcanoclastics Triassic

524-Andesite, rhyolite 

(Cambodia)

C3-P Andesite and rhyolite Upper Carboniferous to Permian

526-Andesite, rhyolite, tuffs 

(Cambodia)

C Andesite, rhyolite, and tuffs Carboniferous

832-Volcanics complexes 

(Thailand)

Mv Rhyolite, andesite, tuff, and 

agglomerate

Mesozoic

Rhyolite, tuff, and agglomerate Permian to Triassic

Intrusive rocks

Volcanic rocks

Table A2. Map units that define tract 142pCu7021, Sukhothai—China, Myanmar, Thailand, Lao People’s Democratic Republic, 

Cambodia, and Vietnam.

[Map unit, age range, and principal lithologies are based on digital map compilations, as cited in table A5]

Although Singer and others (2008) included Phu Lon 

(Thailand) in their global porphyry copper database, Phu Lon 

(see below) is a skarn deposit, not a porphyry copper deposit.

Prospects, Mineral Occurrences, and Related 

Deposit Types

The descriptions of prospects (table A4) are divided into 

those with most of the characteristics of porphyry copper systems and those that are primarily skarn deposits, although they 

are associated with calc-alkaline granitoid intrusions.

Porphyry Copper Prospects

PanAust is actively exploring the Puthep project in 

northern Thailand, about 100 km southwest of the Lao capital 

of Vientane (fig. A1). There are two sites of interest there, 

now called Put 1 and Put 2, formerly known as Phu Hin Lek 

Fai and Phu Thong Daeng. These prospects were discovered 
Appendix A—Tract 142pCu7021 61

in the 1960s (Jacobsen and others, 1969) and are about 10 km 

apart. Put 1 has a resource (measured + indicated + inferred) 

of 264,000,000 tons at 0.43 percent copper and 0.13 g/t gold 

at a cutoff grade of 0.25 percent copper. Put 2 has an inferred 

resource of 72,000,000 tons at 0.42 percent copper at a cutoff 

grade of 0.1 percent copper. Both prospects remain under 

active development (PanAust, 2010).

These outcropping porphyry copper systems are hosted in 

Carboniferous limestone and shale and are related to intermediate-composition intrusions of presumed Permo-Triassic age. 

The majority of the copper is in a subhorizontal bed of supergene chalcocite that averages 30 m in thickness (PanAust, 

2010). The deposits were discovered by exploring occurrences 

of magnetite and malachite in gossans exposed at the surface.

In Vietnam, near Sa Thay, chalcopyrite-bearing quartz 

veinlets and disseminations have been discovered in the 

subvolcanic Middle to Late Triassic Van Canh Complex. 

Numerous varieties of intermediate-composition granitoid and 

volcanic rocks are found in the region. Several areas of pyritequartz-sericite alteration have been identified in the region, 

along with traces of secondary potassium feldspar. Copper 

contents of surface samples are as high as 0.43 percent, with 

gold as high as 0.3 g/t. Notably, molybdenite is part of the 

assemblage, and molybdenum contents reach 840 ppm (Hoa 

and others, 2006).

Copper-Gold Skarn Deposits

The Phu Lon deposit in Thailand (fig. A1) is a coppergold skarn deposit associated with a composite intermediatecomposition granitoid intrusion (Muenlek and others, 1988; 

Pisutha-Arnond and others, 1993; Sitthithaworn and others, 

1993; Kamvong and Khin Zaw, 2005, 2009). It is located in 

the northern part of the country in the Loei magmatic belt, 

adjacent to the Mekong River, which forms the border with 

Lao People’s Democratic Republic. It was partially drilled 

in the 1980s, and a resource of nearly 20,000,000 tons was 

delineated with grades greater than 1 percent copper, gold 

grades near 1 g/t, and silver grades of 4–5 g/t. The presently 

accepted resource (Vudhichativanich and Sitthithaworn, 1993) 

is 53,000,000 tons at 1.7 percent copper and 0.45 g/t gold, 

although other values have been published. The present state 

of development of this deposit is not known.

The deposit consists primarily of mineralized garnetclinopyroxene skarn that is immediately adjacent to the southern part of the Phu Lon pluton. The pluton consists of diorite, 

monzodiorite, and quartz monzonite and shows evidence of 

magma mingling; the pluton has a middle Triassic U-Pb zircon 

date of 244±4 Ma (Kamvong and Khin Zaw, 2005, 2009).

In south-central Lao People’s Democratic Republic, the 

Sepon project is a 1,250 km2 contract area of various gold and 

copper deposits that, as of 2009, contain nearly 4 million oz of 

gold and nearly 2 million tons of copper (MMG, 2009). Gold 

has been produced since 2002, with copper production starting 

in 2005. The production is from numerous open-pit mines 

throughout the area.

The copper deposit currently being mined (Khanong) 

is a near-surface, supergene-enriched chalcocite and copperoxide orebody derived from skarn and replacement deposits in 

carbonate rocks; it is extremely high-grade, with head grades 

Table A3. Identified porphyry copper resources in tract 142pCu7021, Sukhothai—China, Myanmar, Thailand, Lao People’s Democratic Republic, Cambodia, and Vietnam.

[Ma, million years; Mt, million metric tons; t, metric ton; %, percent; g/t, gram per metric ton; n.d., no data. Cu-Au subtype, deposits that have Au/Mo ratios 

>30 or average Au grades >0.2 g/t. Contained Cu in metric tons is computed as tonnage (Mt × 1,000,000) × Cu grade (percent)]

Name Latitude Longitude Subtype Age 

(Ma)

Tonnage 

(Mt)

Cu 

(%)

Mo 

(%)

Au 

(g/t)

Ag 

(g/t)

Contained 

Cu (t)

Reference

Phu 

Kam1

18.918 102.907 Cu-Au 292 183 0.64 n.d. 0.24 2 1,171,200 PanAust (2010) 

1

Deposit is open to the north and below the planned pit, and development continues.

Table A4. Significant prospects and occurrences in tract 142pCu7021, Sukhothai—China, Myanmar, Thailand, Lao People’s Democratic Republic, Cambodia, and Vietnam.

 [%, percent; g/t, grams per metric ton; Mt, million metric tons, Ma, million years]

 Name Latitude Longitude Age (Ma) Comments Reference

Puthep (Put 1 

and 2)

 17.45 101.8 Permian–Triassic(?) Partial resource: >264 Mt at 

0.43% Cu and 0.13 g/t Au (cutoff grade 0.25% Cu).

PanAust (2010)

Sa Thay 14.39 107.83 Triassic Cu up to 0.43%; Au up to 0.3 

ppm; Mo up to 840 ppm.

Hoa and others (2006)

Phu Lon 18.2 102.14 244 Skarn; 53 Mt tons at 1.7% Cu 

and 0.45 g/t Au.

Kamvong and Khin Zaw (2005)

Sepon 16.96 106 Permian–Triassic(?) Skarn and replacement: 2 Mt of 

Cu; 4 Moz of Au.

Manini and Albert (2003)
62 Porphyry Copper Assessment of Southeast Asia and Melanesia 

in excess of 5 percent copper. As of 2009, the total supergene 

copper resource (measured + indicated + inferred) at Sepon 

was 58,800,000 tons at 2.4 percent copper; the total primary 

copper resource was 23,300,000 tons at 1.0 percent copper, 0.3 

g/t gold, and 6 g/t silver. There are two larger prospect areas 

about 7 km away that have not been fully explored.

CRA-Rio Tinto and Oxiana discovered the deposits during 1993–2003 (Manini and Albert, 2003), but exploration of 

the district is far from complete. The known deposits appear 

to be related to emplacement of presumably Permo-Triassic 

intermediate-composition granitoid stocks into Devonian 

through Carboniferous marine sedimentary rocks. The resulting mineral deposits are primarily Cu-Au skarns and disseminated Au deposits, but Mo-Cu stockwork mineralization is 

associated with the stocks (Manini and Albert, 2003), and Sillitoe (2010) has called the district a porphyry copper deposit.

Several other copper-bearing skarn and vein occurrences 

are present throughout the Sukhothai tract, but few details 

about them are known (Khin Zaw and others, 1999; Royal 

Thai Government Department of Mineral Resources, 2010). 

One cluster is in northern Lao People’s Democratic Republic 

in the northern part of the Sukhothai island arc, where several 

small copper vein occurrences are known. Farther north and 

east, in the northernmost part of the Loei Belt, several more 

copper-bearing skarns and veins lie just to the northeast of the 

Pha Nai prospect being explored by PanAust. Another cluster 

of copper-bearing vein occurrences is further east, along the 

border with Vietnam. Copper-bearing vein occurrences also 

are common in the central part of the Loei Belt, from just 

north of the Phu Lon skarn deposit southwest to the region 

surrounding the Puthep project. Further south in the Loei Belt, 

copper-bearing skarn and vein occurrences become less common, but a few are found even in Cambodia, where the Loei 

Belt disappears under the Gulf of Thailand. These copperbearing skarn and vein occurrences are even less common 

along the Lao-Vietnam border in the Truong Son Belt, but 

difficulty of access makes this area extremely poorly known.

The Minle deposit, in southwest Yunnan Province, China, has 

been described as a porphyry copper deposit (Li, 2000) and 

is described by Hou and others (2007), along with the nearby 

Wenyu copper deposit, as being related to a Triassic post-collisional bimodal volcanic suite. Unfortunately, these deposits 

can neither be located, nor is a description of them available.

Exploration History

Throughout much of this region, exploration for porphyry 

copper deposits is at a very early stage. In a 1999 review of 

copper and gold exploration in Southeast Asia, Feebrey (1999) 

did not mention any of the deposits and prospects compiled 

for this tract. Vietnam, Lao People’s Democratic Republic, 

and Cambodia have been engulfed in war from the 1940s until 

very recently, and many of the countries are still in the process 

of developing effective mining laws that support modern mineral-exploration activities. Cambodia, for example, passed its 

first mining law in 2001 (Wu, 2002). There is not an adequate 

aeromagnetic map of the region, and there have been very few 

regional stream-sediment geochemical surveys.

The following summary of geologic mapping is based on 

Burrett (1999). Geologists of the British Geological Survey 

mapped Myanmar, but there has been little activity since 

1939. Lao People’s Democratic Republic has only begun to be 

adequately mapped, mostly since the mid 1990s. Cambodia 

and Vietnam were mapped by French geologists prior to the 

1950s and 1960s, but modern work is limited. Yunnan has 

been mapped by the Chinese, but detailed maps are not available. Geologic maps of peninsular Malaysia, produced by the 

Malaya Geological Survey, are reliable. In Thailand, there was 

little geological study prior to the 1950s, although the maps 

made more recently by the Geological Survey division of the 

Royal Thai Department of Mineral Resources are of high quality.

There has been a steady acceleration of exploration by 

outside corporate geologists, many from China and Australia, 

in the first decade of the 21st century, but the results of that 

work are only beginning to be reported. The earliest outside 

workers may have been with CRA Exploration (now Rio 

Tinto), which began work in Lao People’s Democratic Republic in 1989 (Feebrey, 1999).

Sources of Information

Principal sources of information used by the assessment 

team for delineation of the tract are listed in table A5.

Grade and Tonnage Model Selection

The gold grade at Phu Kam is consistent with the porphyry copper-gold model. The data on prospects and related 

skarn deposits also suggests that gold will be an important 

part of the resource at any undiscovered deposits in the tract. 

ANOVA tests comparing the known deposit with a global 

porphyry copper-gold model indicate that this model (or a 

general model) is appropriate for the simulation of undiscovered resources in the tract, although no data are available for 

testing molybdenum (table 6). We used the porphyry coppergold submodel of Singer and others (2008) for the assessment 

of the Sukhothai tract.

Estimate of the Number of Undiscovered Deposits

Rationale for the Estimate

The tract contains one known porphyry copper deposit 

(Phu Kam) and at least one other advanced prospect (Phutep 

project), as well as other surface indications of porphyry 

copper-style mineralization (Sa Thay). There are also two 
Appendix A—Tract 142pCu7021 63

gold-rich skarn districts with porphyry copper affinity (Sepon 

and Phu Lon). In addition, there are numerous copper- and 

gold-bearing vein and skarn prospects throughout the tract that 

are indicative of the porphyry copper environment.

The tract is heavily vegetated, and much of the terrain is 

steep and rugged, limiting accessibility and inhibiting exploration. Political turmoil prevented any serious exploration in most 

parts of the tract from the 1940s until nearly the end of the 20th 

century. The aftermath of war—continued political turmoil and 

large numbers of unexploded mines and bombs—continues to 

inhibit mineral exploration. When compared to many other parts 

of the world, this tract must be considered underexplored.

All these factors contributed to the assessment team’s estimate that there is at least a 50-percent chance that eight or more 

undiscovered deposits exist in the tract (table A6). The Phutep 

project will almost certainly become a deposit in the future, and 

the team concluded that at least two of the other mineralized 

areas probably contain a porphyry deposit that will be revealed 

by continued exploration and development, thus three undiscovered deposits at the 90-percent probability level are estimated. It 

is also likely that another discovery will be made near Phu Kam.

The team did not apply the deposit density models of 

Singer and others (2005) directly during the assessment; however the team estimate of 4 deposits/100,000 km2 is low compared to the observed range in deposit density in thoroughly 

explored, highly prospective porphyry copper tracts worldwide.

Probabilistic Assessment Simulation 

Results

Undiscovered resources for the tract were estimated by 

combining the team’s estimate for numbers of undiscovered 

porphyry copper deposits with the porphyry copper-gold 

model of Singer and others (2008) using the EMINERS 

program (Root and others, 1992; Bawiec and Spanski, 2012; 

Duval, 2012). Selected simulation results are reported in table 

A7. Results of the Monte Carlo simulation are presented as a 

cumulative frequency plot (fig. A2). The cumulative frequency 

plot shows the estimated resource amounts associated with 

cumulative probabilities of occurrence, as well as the mean, 

for each commodity and for total mineralized rock.

Table A6. Undiscovered deposit estimates, deposit numbers, tract area, and deposit density for tract 142pCu7021, Sukhothai—China, 

Myanmar, Thailand, Lao People’s Democratic Republic, Cambodia, and Vietnam.

[NXX, estimated number of deposits associated with the xxth percentile; Nund, expected number of undiscovered deposits; s, standard deviation; Cv%, coefficient 

of variance; Nknown, number of known deposits in the tract that are included in the grade and tonnage model; Ntotal, total of expected number of deposits plus 

known deposits; km2, area of permissive tract in square kilometers; Ntotal/100k km2, deposit density reported as the total number of deposits per 100,000 km2. 

Nund, s, and Cv% are calculated using a regression equation (Singer and Menzie, 2005)]

Table A5. Principal sources of information used for tract 142pCu7021, Sukhothai—China, Myanmar, Thailand, Lao People’s Democratic Republic, Cambodia, and Vietnam. 

[NA, not applicable; MMAJ, Metal Mining Agency of Japan; AMIRA, AMIRA International Ltd (http://www.amira.com.au/); CCOP, Coordinating Committee 

for Geoscience Programmes in East and Southeast Asia]

Theme Name or Title Scale Citation

Geology Digital geologic map of East and Southeast Asia 1:2,000,000 CCOP and Geological Survey of Japan (1997)

Digital geologic maps of Myanmar, Laos, Cambodia, 

Thailand, Vietnam, and Yunnan Province, China

 1;250,000; 

1:500,000

Khin Zaw and others (1999)

 Mineral

occurrences

Porphyry copper deposits of the world: database, map, and 

grade and tonnage models

NA Singer and others (2008)

AMIRA database NA Khin Zaw and others (1999)

MMAJ database NA Metal Mining Agency of Japan (1998)

World Minerals Geoscience Database NA Natural Resources Canada (2010)

 Consensus undiscovered deposit estimates Summary statistics

Tract area 

(km2

)

Deposit density 

(Ntotal/100k km2)

N90 N50 N10 N05 N01 Nund s Cv% Nknown Ntotal

3 8 26 26 26 12 8.5 73 1 13 354,260 4
64 Porphyry Copper Assessment of Southeast Asia and Melanesia 

References Cited

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Kamvong, T., 2006, Geology and genesis of porphyry-skarn 

Cu-Au deposits at the northern Loei Fold Belt, northeast 

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Table A7. Results of Monte Carlo simulations of undiscovered resources for tract 142pCu7021, Sukhothai—China, Myanmar, Thailand, Lao People’s Democratic Republic, Cambodia, and Vietnam.

[Cu, copper; Mo, molybdenum; Au, gold; and Ag, silver; in metric tons; Rock, in million metric tons]

Material

 Probability of at least the indicated amount Probability of

 0.95 0.9 0.5 0.1 0.05 Mean Mean or 

greater None

Cu 900,000 2,900,000 24,000,000 90,000,000 110,000,000 37,000,000 0.38 0.03

Mo 0 0 89,000 590,000 830,000 210,000 0.31 0.11

Au 84 250 1,900 6,300 7,700 2,700 0.4 0.03

Ag 0 220 5,200 35,000 52,000 12,000 0.29 0.08

Rock 200 640 5,100 18,000 22,000 7,400 0.4 0.03
Appendix A—Tract 142pCu7021 65

Kamvong, T., and Khin Zaw, 2005, Geology and genesis of 

Phu Lon copper-gold skarn deposit, northeast Thailand: 

International conference on Geology, Geotechnology 

and Mineral Resources of Indochina (GEOINDO 2005), 

November 28–30, 2005, Khon Kaen, Thailand. (Also 

available at http://library.dmr.go.th/library/9346.pdf.)

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of skarn-forming fluids from the Phu Lon deposit, northern 

Loei Fold Belt, Thailand—Evidence from fluid inclusion 

and isotope studies: Journal of Asian Earth Sciences, v. 34, 

p. 624–633.

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deposits in mainland Southeast Asia (P390A): Australia, 

University of Tasmania, Centre for Ore Deposit Research, 

Project P390A, (unpaginated, includes CD-ROM with GIS 

database). [Proprietary report].

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Thanasuthipitak, T., Zaw, K., and Meffre, S., 2008, 

Petrochemistry and zircon age determination of LoeiPhetchabun volcanic rocks: Proceedings of the International 

Symposia on Geoscience Resources and Environments 

of Asian Terranes (GREAT 2008), 4th IGCP 516 and 5th 

APSEG, Bangkok, Thailand, p. 272–278.

Li, W., 2000, The use of transient electromagnetic methods in 

mineral exploration in the Minle porphyry copper deposit, 

Yunnan, China: Geophysical and Geochemical Exploration, 

v. 24, p. 391–393.

Manaka, T., Khin Zaw, and Meffre, S., 2008, Geological and 

tectonic setting of Cu-Au deposits in northern Lao PDR: 

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Resources and Environments of Asian Terranes (GREAT 2008), 

4th IGCP 516 and 5th APSEG, Bangkok, Thailand, p. 254–257.

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of the Sepon gold and copper deposits, Laos: Sydney 

Mineral Exploration Discussion Group (SMEDG): AIG 

Symposium, Sydney, Australia, accessed August 12, 2010, at 

http://www.smedg.org.au/Tiger/Sepon.htm.

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resources map of Asia: Metal Mining Agency of Japan, 43 

p.,1 sheet, scale 1:10,000,000.

Muenlek, S., Choochotiros, P., Muenlek, P., and 

Vudhichatiwanich, S., 1988, Phu Lon-Ban Na Ngiu Gold 

Prospect, Amphoe Sangkhom, Changwat Nong Khai: 

Department of Mineral Resources, Thailand Economic 

Geology Report Number 14, 120 p.

MMG, 2009, Sepon project, MMG and Laos, growing 

together: MMG Web page accessed August 12, 2010, at 

http://www.mmgroupltd.com/common/files/MMG_LXML_

Sep-09.pdf.

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database: Natural Resources Canada Web page, accessed 

August 12, 2010, at http://gsc.nrcan.gc.ca/wmgdb/index_e.php.

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Web page accessed August 12, 2010, at http://www.panaust.

com.au/PNA_ProjectsPhuKham.html.

Pisutha-Arnond, V., Sunmanee, S., and Yaemniyom, S., 

1993, Copper-iron-gold-silver skarn prospect at Phu Lon, 

Changwat Nong Khai, northeastern Thailand—A porphyrystyle mineralization: Proceedings of the 29th International 

Geological Congress, 1992, Mineral Resources Symposia 

volume A, Resource Geology, Special Issue no. 15, Tokyo, 

Japan, p. 265–274.

Putthapiban, P., 2002, Geology and geochronology of the 

igneous rocks of Thailand: Proceedings of the Symposium 

on Geology of Thailand, August 2002. (Also available at 

http://www.dmr.go.th/dmr_data/DMR_eng/geology/igneous/

igneous01.htm.)

Root, D.H., Menzie, W.D., and Scott, W.A., 1992, Com-puter 

Monte Carlo simulation in quantitative resource estimation: 

Natural Resources Research, v. 1, no. 2, p. 125–138.

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2010, Royal Thai Government Department of Mineral 

Resources Web site: accessed August 12, 2010, at http://

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meta04.htm#e43.

Sillitoe, R.H., 2010, Porphyry copper systems: Economic 

Geology, v. 105, p. 3–41.

Singer, D.A., 2008, Mineral deposit densities for estimating 

mineral resources: Mathematical Geosciences, v. 40, p. 

33–46.

Singer, D.A., Berger, V.I., Menzie, W.D., and Berger, B.R., 

2005, Porphyry copper density: Economic Geology, v. 100, 

no. 3, p. 491–514.

Singer, D.A., Berger, V.I., and Moring, B.C., 2008, Porphyry 

copper deposits of the world—Database and grade and 

tonnage models, 2008: U.S. Geological Survey Open-File 

Report 2008–1155, accessed June 1, 2011, at http://pubs.usgs.

gov/of/2008/1155/.

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estimating the number of undiscovered mineral deposits—An 

example with porphyry copper deposits, in Cheng, Qiuming, 

and Bonham-Carter, Graeme, eds., Proceedings of IAMG—

The annual conference of the International Association for 

Mathematical Geology: Toronto, Canada, York University, 

Geomatics Research Laboratory, p. 1028–1033.

Sitthithaworn, E., Albino, G.V., and Fyfe, W.S., 1993, 

Copper-gold porphyry and skarn mineralization at Phu 
66 Porphyry Copper Assessment of Southeast Asia and Melanesia

Lon, northern Thailand: Transactions of the Institution of 

Mining and Metallurgy, Section B, v. 102, p. B181–B191.

Sone, M., and Metcalfe, I., 2008, Parallel Tethyan sutures in 

mainland Southeast Asia—New insights for Palaeo-Tethys 

closure and implications for the Indosinian orogeny: Comptes 

Rendus Geoscience, v. 340, p. 166–179.

U.S. Department of State, 2009, Small-scale digital international 

land boundaries (SSIB)—Lines, edition 10, and polygons, 

beta edition 1, in Boundaries and sovereignty encyclopedia 

(B.A.S.E.): U.S. Department of State, Office of the 

Geographer and Global Issues.

Vudhichativanich, S., and Sitthithaworn, E., 1993, Au-Cu mineralization at Phu Lon, northeastern Thailand: Proceedings 

of the 29th International Geological Congress, 1992, Mineral 

Resources Symposia volume A, Resource Geology, Special 

Issue no. 15, Tokyo, Japan, p. 231–239.

Wakita, K., and Metcalfe, I., 2005, Ocean plate stratigraphy in 

East and Southeast Asia: Journal of Asian Earth Sciences, v. 

24, p. 679–702.

Wu, J.C., 2002, The mineral industries of Cambodia and Laos: 

U.S. Geological Survey, 2002 Minerals Yearbook, 

p. 7.1–7.5, accessed August 15, 2011, at http://minerals.usgs.

gov/minerals/pubs/country/asia.html#cb.
95° E 105° E

25° N15° N

!

!

!

!

!

!

!

!

!

!

!

!

Sepon

Sa Thay

Phu Lon

Phu Kam

Puthep (Put 1 and 2)

Hanoi

Kunming

Guiyang

Rangoon

Changsha

Guangzhou

Ho Chi Minh City

CHINA

MYANMAR

LAOS

THAILAND

VIETNAM

CAMBODIA

INDIA

Andaman Sea

Gulf of Thailand

SOUTH CHINA SEA

100°

30°N20°N10°N

MM

Political boundary source: U.S. Department of State (2009)Projection: Asia South Albers Equal Area Conic;Central meridian 105° E; latitude of origin 15° S

EX

0 200 400 KILOMETERS0 100 200 MILES

Othe

Porpdeptrac

Ass142pPorpprostrac

100 300

Area of Map

Figure A1. Map showing tract location, known deposits, and significant porphyry copper prospects for tract 142pCu7021, Sukhothai—China, Thaiple’s Democratic Republic, Cambodia, and Vietnam. MM, known deposits, Myanmar; TH, Thailand.
68 Porphyry Copper Assessment of Southeast Asia and Melanesia

Material, in metric tons

0.1 1 10 100 1k 10k 100k 1M 10M 100M 1B 10B 100B 1Tr

Probability

1.00

0.90

0.80

0.70

0.60

0.50

0.40

0.30

0.20

0.10

0.00

Mean Au Mean Rock Mean Cu

Mean Ag

Mean Mo

Cu

Mo

Au

Ag

Rock

Mean Cu

Mean Mo

Mean Au

Mean Ag

Mean Rock

EXPLANATION

Figure A2. Cumulative frequency plot showing the results of Monte Carlo computer simulation of undiscovered 

resources in 142pCu7021, Sukhothai—China, Thailand, Myanmar, Lao People’s Democratic Republic, Cambodia, and 

Vietnam. k, thousands; M, millions; B, billions; Tr, trillions.
Appendix B—Tract 142pCu7022 69

Deposit Type Assessed: Porphyry copper, copper-gold subtype

Descriptive model: Porphyry copper (Berger and others, 2008; Cox, 1986; John and others, 2010)

Grade and tonnage model: Porphyry copper, Cu-Au subtype (Singer and others, 2008)

Table B1 summarizes selected assessment results.

Appendix B. Porphyry Copper Assessment for Tract 142pCu7022, 

Malaysia—Malaysia, Thailand, Singapore, and Indonesia

By Steve Ludington1, Sze Wah Alexander Yan2, Jane M. Hammarstrom3, and Gilpin R. Robinson, Jr.3,

with contributions from Bambang Tjahjono Setiabudi4

 and Chen Shick Pei5

Table B1. Summary of selected resource assessment results for tract 142pCu7022, Malaysia—Malaysia, Thailand, Singapore, and 

Indonesia.

[km, kilometers; km2, square kilometers; t, metric tons]

1:2,000,000 Assessment

depth (km)

Tract area 

(km2)

Known copper 

resources (t)

Mean estimate of 

undiscovered copper 

resources (t)

Median estimate of

undiscovered 

copper resources (t)

February 2010 1 60,000 810,000 8,900,000 3,500,000

1

U.S. Geological Survey, Menlo Park, California, United States.

2

Minerals and Geoscience Department Malaysia, Kota Kinabalu, Malaysia.

3

U.S. Geological Survey, Reston, Virginia, United States.

4

Geological Agency of Indonesia, Bandung, Indonesia.

5

Coordinating Committee for Geoscience Programmes in East and Southeast Asia (CCOP) Technical Secretariat, Bangkok, Thailand.

Location

The tract extends for about 700 km from the southernmost tip of Thailand, through peninsular Malaysia, and it includes the 

northern margin of Singapore Island and parts of two of the Indonesian Tin Islands (fig. B1).

Geologic Feature Assessed

Assemblage of Carboniferous through Triassic rocks formed as both island arcs and continental arcs by subduction of 

Paleotethyan oceanic crust below the East Malaya terrane.

Delineation of the Permissive Tract

Tectonic Setting

The plate tectonic history of Southeast Asia is still a matter of contention. The Carboniferous through Triassic magmatic rocks 

that define the Malaysia tract are, however, all related to the amalgamation of a series of microcontinents that were rifted off Gond-
70 Porphyry Copper Assessment of Southeast Asia and Melanesia

wana (fig. 5A) and drifted north as a result of subduction of the 

Paleotethyan ocean (Wakita and Metcalfe, 2005). The Sukhothai island-arc system, as defined by Sone and Metcalfe (2008), 

is the result of the eastward subduction of Paleotethyan ocean 

floor beneath Indochina; subduction began in the latest Carboniferous and ended in the Late Triassic, when Sibumasu collided 

with East Malaya (fig. 5A). Sone and Metcalfe (2008) assign 

all of the area delineated as the Malaysia tract to this island-arc 

system. However, Metcalfe (2008), in the same volume, suggests that only the central ranges of Malaysia are part of this 

arc, presumably assigning the rocks in the eastern part of the 

country to a continental arc. We excluded much of the eastern 

part of Malaysia from this tract, based primarily on the distribution of mineral prospects; in the excluded eastern part, nearly 

all the prospects contain major tin and (or) tungsten, and none 

contain copper, indicating that the rocks there, like those west 

of the Bentong-Raub suture (fig. 5A), are collision-related, and 

unlikely to be associated with porphyry copper deposits.

Geologic Criteria

The digital geologic map used to select the rocks that 

define the permissive tract is a compilation of digital maps of 

Thailand and Malaysia that were prepared by a group at the 

University of Tasmania (Khin Zaw and others, 1999). The 

digital geologic map does not always reflect the most recent 

radiometric age determinations or petrologic studies on the 

rocks in the tract, whose ages are not always accurately known. 

At the same time, many of the rocks have not been dated 

precisely nor have they been studied extensively petrologically. 

Hence, it is likely that some rocks that are not permissive for 

porphyry copper deposits are included, either because they are 

not actually Permian to Triassic in age, are peraluminous, or 

are otherwise not strictly part of the volcanic-arc assemblage. 

Ultramafic rocks, peraluminous granites, and widespread areas 

of dominantly silicic volcanism are excluded.

To define the area included in the permissive tract, we 

first classified igneous map units as permissive or not, based 

on the geologic criteria described above, that is calc-alkaline 

and alkaline volcanic and plutonic rocks of Late Carboniferous, Permian, and Triassic ages. In Malaysia, the geologic map 

attribution does not distinguish between I-type, arc-related 

igneous rocks and S-type, collision-related rocks, and we 

relied primarily on the maps of Cobbing and others (1992) 

to assign polygons as permissive or not. The maps by Cobbing and others (1992) also were used to delineate the small 

part of the tract on Batam and Bintan Islands, Indonesia, 

based on the presence of I-type granites. To the polygons 

(fig. B1) that represent these permissive rocks, we applied a 

10-km buffer to plutonic-rock polygons and a 2-km buffer to 

volcanic-rock polygons; this expanded the area of the tract to 

include all porphyry copper deposits and significant associated 

prospects and accounts for uncertainties in the cartographic 

position of mapped boundaries, as well as possible unexposed 

or unmapped permissive rocks. Digital map units chosen as 

permissive are listed in table B2.

After buffering, the limited geophysical and geochemical 

information was examined to ensure inclusion of any other evidence of unmapped permissive rocks or hydrothermal systems. 

A smoothing routine was applied to the resulting polygons, and 

the tract was trimmed on the southwest by the Benton-Raub 

suture. The tract was compared to several maps that delineate 

parallel belts of granitoids of contrasting composition in Southeast Asia to be sure that the tract is restricted to the I-type calcalkaline rocks; these maps include those of Cobbing and others 

(1992) and Putthapiban (2002). There are a few outcrops of 

Cretaceous and Tertiary volcanic rocks within the tract, but they 

are neither thick nor widespread. Finally, the resulting shapefile 

was clipped to the shoreline to eliminate undersea areas (U.S. 

Department of State, 2009). There are no known post-Triassic 

intrusions in the tract. The tract is shown in figure B1.

Known Deposits

The Mengapur deposit is listed by Singer and others 

(2008) as a porphyry copper deposit of 45,000,000 tons, a copper grade of 1.8 percent and a gold grade of 0.6 g/t, but it is better considered to be a copper-gold-iron skarn deposit (table B3). 

The six oxidized orebodies being exploited at present, as well as 

seven sulfide bodies, form a ring around a poorly-mineralized 

adamellite intrusion (Kiang, 2008).

Mengapur was discovered in 1979 by the Geological Survey of Malaysia through regional geochemical sampling. It was 

prospected during 1983–1993 by MMC, who drilled 198 holes 

that amounted to 58,000 m of core. In 2006, Malaco Mining 

began the redevelopment of the project, and production started 

in September 2008. The main ore mineral is chalcopyrite, but 

magnetite also is recovered as a byproduct. According to Wong 

and Lee (1986), additional ore minerals include galena, molybdenite, pyrite, and sphalerite. Another small copper-gold skarn 

prospect, Bukit Botak, is about 2 km northwest of Mengapur 

(Heng and others, 2003).

Prospects, Mineral Occurrences, and Related 

Deposit Types

There is a surprising lack of copper-bearing prospects in 

Malaysia. Pekan, located about 35 km south of Mengapur, is 

reported to be related to volcanogenic massive sulfide deposits 

nearby. Several copper-bearing prospects in the northern part 

of the tract include a polymetallic skarn and gold-vein deposits. 

None of these prospects were considered significant.

A number of gold deposits are present in the Central Gold 

Belt, about 100 km to the west of Mengapur. Most of them are 

related to intermediate-composition intrusions and are perhaps 

best regarded as polymetallic veins, as they commonly contain 

moderate amounts of copper, lead, and zinc (Hassan and Purwanto, 2002; Wong and Lee, 1986).

Exploration History

The assessment team found little information about exploration for porphyry copper deposits in Malaysia and therefore 
Appendix B—Tract 142pCu7022 71

surmised that there has been little exploration. Exploration has 

focused on tin and, within the tract, gold and base metals in the 

Kuala Lipis-Raub and Jeli-Gua Musang areas in the western 

part of the tract.

The geologic maps of peninsular Malaysia produced by the 

Malaysia Geological Survey are reported to be reliable (Burrett, 

1999). The assessment team found no evidence of any current 

exploration by non-Malaysian mining companies.

Sources of Information

Principal sources of information used by the assessment 

team for delineation of the tract are listed in table B4.

Grade and Tonnage Model Selection

The known copper-skarn deposits in the tract are gold-rich, 

and gold likely will be an important part of the resource at any 

undiscovered deposits in the tract. Many of the rocks that define 

the tract represent accreted island-arc rocks that were originally 

emplaced on oceanic crust. The porphyry copper-gold submodel 

of Singer and others (2008) was selected for the assessment of 

the Malaysia tract (table 6).

Estimate of the Number of Undiscovered Deposits

Rationale for the Estimate

The tract contains a large gold-rich skarn deposit with 

porphyry copper affinity (Mengapur). In addition, there are scattered copper- and gold-bearing vein and skarn prospects, as well 

as numerous gold-rich polymetallic vein deposits throughout 

the tract that are indicative of the porphyry copper environment. 

The tract is heavily vegetated and most historical exploration 

has been for alluvial tin and gold.

All these factors contributed to the assessment team’s 

estimate that there is at least an even chance that two or more 

undiscovered deposits exist in the tract (table B5). The deposit 

density obtained from the estimate is five deposits/100,000 km2

, 

which is less prospective than would be predicted by the global 

deposit-density model of Singer and others (2005).

Table B3. Identified porphyry copper resources in tract 142pCu7022, Malaysia—Malaysia, Thailand, Singapore, and Indonesia.

[Ma, million years; Mt, million metric tons; t, metric ton; %, percent; g/t, gram per metric ton; Cu-Au subtype, deposits that have Au/Mo ratios >30 or average 

Au grades >0.2 g/t; n.d., no data. Contained Cu in metric tons is computed as tonnage (Mt × 1,000,000) × Cu grade (percent)]

Name Latitude Longitude Subtype Age (Ma) Tonnage 

(Mt)

Cu

(%)

Mo

(%)

Au

(g/t)

Ag

(g/t)

Contained 

Cu (t) Reference

Mengapur1 3.746 102.825 Cu-Au presumed 

Triassic 45 1.8 n.d. 0.6 n.d. 810,000 Kiang (2008)

1

Deposit is best considered a Cu-Au-Fe skarn deposit.

Table B2. Map units that define tract 142pCu7022, Malaysia—Malaysia, Thailand, Singapore, and Indonesia.

[Map unit, age range, and principal lithologies are based on a digital compilation of geologic maps of Thailand and Indonesia (Khin Zaw and others, 1999)]

Map unit Map symbol Lithology Age range

Intrusive rocks

30-Acid intrusives (undifferentiated) (Malaysia) Ag Acid intrusives Triassic and unknown

31-Intermediate intrusives (undifferentiated) Ig Intermediate intrusives Paleozoic and Mesozoic

834-Granite, granodiorite, and minor diorite (Thailand) gr Granite, granodiorite, and minor diorite Triassic and unknown

Volcanic rocks

420-Ignimbrite K Ignimbrite Triassic

421-Acid to intermedite volcanics K Dacite and rhyolite Triassic

422-Intermediate to basic volcanics K Andesite and basalt Triassic

520-Ignimbrite P Ash-flow tuff Permian

521-Acid to intermediate volcanics C Dacite and rhyolite Carboniferous

522-Intermediate to basic volcanics P Andesite and basalt Permian

621-Acid to intermediate volcanics C Dacite and rhyolite Carboniferous

622-Intermediate to basic volcanics C Andesite and basalt Carboniferous
72 Porphyry Copper Assessment of Southeast Asia and Melanesia

Probabilistic Assessment Simulation 

Results

Undiscovered resources for the tract were estimated by 

combining the team’s estimate for numbers of undiscovered 

porphyry copper deposits with the porphyry copper-gold 

model of Singer and others (2008) using the EMINERS 

program (Root and others, 1992; Bawiec and Spanski, 

2012; Duval, 2012). Selected simulation results are reported 

in table B6. Results of the Monte Carlo simulation are 

presented as a cumulative frequency plot (fig. B2). The 

cumulative frequency plot shows the estimated resource 

amounts associated with cumulative probabilities of 

occurrence, as well as the mean, for each commodity and for 

total mineralized rock.

Table B4. Principal sources of information used for tract 142pCu7022, Malaysia—Malaysia, Thailand, Singapore, and Indonesia.

[NA, not applicable; MMAJ, Metal Mining Agency of Japan; AMIRA, AMIRA International Ltd (http://www.amira.com.au/); CCOP, Coordinating Committee 

for Geoscience Programmes in East and Southeast Asia]

Theme Name or title Scale Citation

Geology Digital geologic map of East and Southeast Asia 1:2,000,000 CCOP and Geological Survey of Japan (1997)

Digital geologic maps of Myanmar, Laos, Cambodia, 

Thailand, Vietnam, and Yunnan Province, China

 1;250,000;

 1:500,000 

Khin Zaw and others (1999)

Mineral 

occurrences

Porphyry copper deposits of the world: database, 

map, and grade and tonnage models

 NA Singer and others (2008)

AMIRA database NA Khin Zaw and others (1999)

MMAJ database NA Metal Mining Agency of Japan (1998)

World Minerals Geoscience Database NA Natural Resources Canada (2010)

Table B5. Undiscovered deposit estimates, deposit numbers, tract area, and deposit density for tract 142pCu7022, Malaysia—Malaysia, 

Thailand, Singapore, and Indonesia.

[NXX, estimated number of deposits associated with the xxth percentile; Nund, expected number of undiscovered deposits; s, standard deviation; Cv%, coefficient 

of variance; Nknown, number of known deposits in the tract that are included in the grade and tonnage model; Ntotal, total of expected number of deposits plus 

known deposits; km2, area of permissive tract in square kilometers; Ntotal/100k km2, deposit density reported as the total number of deposits per 100,000 km2. 

Nund, s, and Cv% are calculated using a regression equation (Singer and Menzie, 2005)]

 Consensus undiscovered deposit estimates Summary statistics Tract area 

(km2

)

Deposit density 

(Ntotal/100k km2) N90 N50 N10 N05 N01 Nund s Cv% Nknown Ntotal

1 2 6 6 6 2.8 2 70 1 3.8 60,000 6

Table B6. Results of Monte Carlo simulations of undiscovered resources for tract 142pCu7022, Malaysia—Malaysia, Thailand, 

Singapore, and Indonesia.

[Cu, copper; Mo, molybdenum; Au, gold; and Ag, silver; in metric tons; Rock, in million metric tons]

Material

Probability of at least the indicated amount Probability of

0.95 0.9 0.5 0.1 0.05 Mean Mean or 

greater

None

Cu 0 180,000 3,500,000 23,000,000 40,000,000 8,900,000 0.26 0.06

Mo 0 0 5,200 130,000 280,000 52,000 0.2 0.39

Au 0 20 300 1,700 2,500 640 0.3 0.06

Ag 0 0 540 6,500 13,000 2,900 0.2 0.3

Rock 0 44 760 4,700 8,100 1,800 0.28 0.06
Appendix B—Tract 142pCu7022 73

References Cited

Bawiec, W.J., and Spanski, G.T., 2012, Quick-start guide for 

version 3.0 of EMINERS—Economic Mineral Resource 

Simulator: U.S. Geological Survey Open-File Report 

2009–1057, 26 p., accessed June 30, 2012, at http://pubs.

usgs.gov/of/2009/1057. (This report supplements USGS OFR 

2004–1344.)

Berger, B.R., Ayuso, R.A., Wynn, J.C., and Seal, R.R., 2008, 

Preliminary model of porphyry copper deposits: U.S. 

Geological Survey Open-File Report 2008–1321, 55 p., 

accessed May 15, 2009, at http://pubs.usgs.gov/of/2008/1321.

Burrett, C. F., 1999, Accuracy of geological mapping and crossborder correlations, in Khin Zaw, Burrett, C.F., Berry, R.F., 

and Bruce, E., 1999, Geological, tectonic, and metallogenic 

relations of mineral deposits in mainland Southeast Asia 

(P390A): Australia, University of Tasmania, Centre for Ore 

Deposit Research, School of Earth Sciences, p. 58–62.

Cobbing, E.J., Pitfield, P.E.J., Darbyshire, D.P.F., and Mallick, 

D.I.J., 1992, The granites of the South-East Asian tin belt: 

British Geological Survey, Overseas Memoir 10, 369 p.

Coordinating Committee for Coastal and Offshore Geoscience 

Programmes in East and Southeast Asia (CCOP) and 

Geological Survey of Japan, 1997, Digital geologic map of 

East and Southeast Asia: Geological Survey of Japan, Digital 

Geoscience Map G-2 scale 1:2,000,000, CD-ROM.

Cox, D.P., 1986, Descriptive model of porphyry Cu, in Cox, 

D.P., and Singer, D.A., eds., 1986, Mineral deposit models: 

U.S. Geological Survey Bulletin 1693, p. 76. (Also available 

at http://pubs.usgs.gov/bul/b1693/.) 

Duval, J.S., 2012, Version 3.0 of EMINERS—Economic 

Mineral Resource Simulator: U.S. Geological Survey Open 

File Report 2004–1344, accessed July 5, 2012, at http://pubs.

usgs.gov/of/2004/1344.

Hassan, W.F.W., and Purwanto, H.S., 2002, Type deposits of 

primary gold mineralization in the Central Belt of Peninsular 

Malaysia: Geological Society of Malaysia, Annual Geological 

Conference 2002, p. 111–115.

Heng, G.S., Hoe, T.G., and Umor, M.R., 2003, Fluid inclusions 

studies of Bukit Botak skarn deposit, Mengapor, Pahang: 

Geological Society of Malaysia, Bulletin 46, p. 231–238.

John, D.A., Ayuso, R.A., Barton, M.D., Blakely, R.J., Bodnar, 

R.J., Dilles, J.H., Gray, Floyd, Graybeal, F.T., Mars, J.C., 

McPhee, D.K., Seal, R.R., Taylor, R.D., and Vikre, P.G., 

2010, Porphyry copper deposit model, chap. B of Mineral 

deposit models for resource assessment: U.S. Geological 

Survey Scientific Investigations Report 2010–5070–B, 169 

p., accessed September 8, 2010, at http://pubs.usgs.gov/

sir/2010/5070/b/.

Khin Zaw, Burrett, C.F., Berry, R.F., and Bruce, E., 1999, 

Geological, tectonic, and metallogenic relations of mineral 

deposits in mainland Southeast Asia (P390A): Australia, 

University of Tasmania, Centre for Ore deposit Research, 

Project P390A, (unpaginated, includes CD-ROM with GIS 

database). [Proprietary report.]

Kiang, S.H., 2008, The development of the Mengapur copper 

mine, Malaysia: 8th Asia Pacific Mining Conference, 

October 14–16, 2008, Manila, Philippines, accessed August 

12, 2010, at http://www.afmaasean.org/presentation/

day2/TheDevelopementoftheMengapurCopperMineMrSiaHokKiang.pdf.

Metal Mining Agency of Japan (MMAJ), 1998, Mineral 

Resources Map of Asia: Metal Mining Agency of Japan, 

43 p., 1 sheet, scale 1:10,000,000.

Metcalfe, I., 2008, Gondwana dispersion and Asian 

accretion—An update: Proceedings of the international 

Symposia on Geoscience Resources and Environments 

of Asian Terranes (GREAT 2008), 4th IGCP 516 and 5th 

APSEG, Bangkok, Thailand, p. 23–25.

Natural Resources Canada, 2010, World minerals geoscience 

database: accessed August 12, 2010, at http://gsc.nrcan.

gc.ca/wmgdb/index_e.php.

Putthapiban, P., 2002, Geology and geochronology of the 

igneous rocks of Thailand: Proceedings of the Symposium 

on Geology of Thailand, August 2002. (Also available at 

http://www.dmr.go.th/dmr_data/DMR_eng/geology/

igneous/igneous01.htm.)

Root, D.H., Menzie, W.D., and Scott, W.A., 1992, Computer 

Monte Carlo simulation in quantitative resource estimation: 

Natural Resources Research, v. 1, no. 2, p. 125–138.

Singer, D.A., Berger, V.I., Menzie, W.D., and Berger, B.R., 

2005, Porphyry copper density: Economic Geology, v. 100, 

no. 3, p. 491–514.

Singer, D.A., Berger, V.I., and Moring, B.C., 2008, Porphyry 

copper deposits of the world—Database and grade and 

tonnage models, 2008: U.S. Geological Survey Open-File 

Report 2008–1155, accessed June 1, 2011, at http://pubs.

usgs.gov/of/2008/1155/.

Sone, M., and Metcalfe, I., 2008, Parallel Tethyan sutures 

in mainland Southeast Asia—New insights for PalaeoTethys closure and implications for the Indosinian orogeny: 

Comptes Rendus Geoscience, v. 340, p. 166–179.

U.S. Department of State, 2009, Small-scale digital 

international land boundaries (SSIB)—Lines, edition 10, 

and polygons, beta edition 1, in Boundaries and sovereignty 

encyclopedia (B.A.S.E.): U.S. Department of State, Office 

of the Geographer and Global Issues.
74 Porphyry Copper Assessment of Southeast Asia and Melanesia

Wakita, K., and Metcalfe, I., 2005, Ocean plate stratigraphy in 

East and Southeast Asia: Journal of Asian Earth Sciences, v. 

24, p. 679–702.

Wong, W.S., and Lee, A.K., 1986, Gold investigation in the 

Sungai Luit area, Mengapur base metal district, Pahang: 

GEOSEAV Proceedings, v. 2, Bulletin of the Geological 

Society of Malaysia, no. 20, p. 667–700.
References Cited 75

Figure B1. Map showing tract location and porphyry copper deposits for tract 142pCu7022, Malaysia—Malaysia, Thailand, Singapore, and Indonesia. ID, Indonesia; KH, Cambodia; MM, Myanmar; MY, Malaysia; TH, Thailand.

102° E 104° E

6° N

2° N

!

!

!

!

!

!

!

!

!

!

!

!

Kuantan

Kuala

Terengganu

Kuala

Lumpur

Seremban

Melaka

Johor

Baharu

Pekanbaru

Singapore

Kota

Baharu

Mengapur

MALAYSIA

THAILAND

INDONESIA

SINGAPORE

Malacca Strait

South China Sea

Sumatra Batam Island

Bintan Island

100°E 110°E

20°N

10°N

0°

10°S

TH

ID ID

MY

MY

KH

MM

INDIAN OCEAN

Political boundary source: U.S. Department of State (2009)

Projection: Asia South Albers Equal Area Conic;

Central meridian 103° E; latitude of origin 15° S

EXPLANATION

Porphyry copper deposit

Assessed porphyry copper tract

142pCu7022

0 5025 75 100 KILOMETERS

0 25 50 MILES

Area of Map
76 Porphyry Copper Assessment of Southeast Asia and Melanesia Probability

1.00

0.90

0.80

0.70

0.60

0.50

0.40

0.30

0.20

0.10

0.00

Material, metric tons

0.01 0.1 1 10 100 1k 10k 100k 1M 10M 100M 1B 10B 100B

Mean Cu

Mean Mo

Mean Au Mean Rock

Mean Ag

Cu

Mo

Au

Ag

Rock

Mean Cu

Mean Mo 

Mean Au

Mean Ag

Mean Rock 

EXPLANATION

Figure B2. Cumulative frequency plot showing the results of Monte Carlo computer simulation of undiscovered 

resources in tract 142pCu7022, Malaysia—Malaysia, Thailand, Singapore, and Indonesia. k, thousands; M, millions; 

B, billions; Tr, trillions.
Appendix C—Tract 142pCu7023 77

Appendix C. Porphyry Copper Assessment for Tract 142pCu7023, 

Mekong Delta—Vietnam, Cambodia, and Lao People’s Democratic Republic

By Steve Ludington1, Jane M. Hammarstrom2, and Gilpin R. Robinson, Jr.2, with contributions from Wudhikarn 

Sukserm3

, Pairatt Jarnyaharn3, Pichai Otarawanna3, Boonsong Yokartt3, Sompob Wongsomasak3, 

Nguyen Van Quy4

, Sieng Sotham5, I.M. Sim5, and Takehiro Sakimoto3

1

U.S. Geological Survey, Menlo Park, California, United States.

2

U.S. Geological Survey, Reston, Virginia, United States.

3

Royal Thai Government Department of Mineral Resources, Bangkok, Thailand.

4

Department of Geology and Minerals of Vietnam, Hanoi, Vietnam.

5

Department of Geology and Mines, Phnom Penh, Cambodia.

Deposit Type Assessed: Porphyry copper

Descriptive model: Porphyry copper (Berger and others, 2008; Cox, 1986; John and others, 2010)

Grade and tonnage model: Porphyry copper, general model (Singer and others, 2008)

Table C1 summarizes selected assessment results.

Location

The tract is within an area about 500 by 700 km in the central part of Cambodia and the southern part of Vietnam; it also 

includes a small area in southeast Lao People’s Democratic Republic (Laos) (fig. C1).

Geologic Feature Assessed

A field of Jurassic and Cretaceous intrusive and volcanic rocks that are the result of subduction of the Pacific Plate beneath 

southern Indochina.

Table C1. Summary of selected resource assessment results for tract 142pCu7023, Mekong Delta—Vietnam, Cambodia, and Laos.

[km, kilometers; km2, square kilometers; t, metric tons; n.d., no data]

Date of 

assessment

Assessment depth 

(km)

Tract area 

(km2)

Known copper 

resources (t)

Mean estimate of 

undiscovered copper 

resources (t)

Median estimate of 

undiscovered copper 

resources (t)

February 2010 1 91,220 n.d. 28,000,000 16,000,000
78 Porphyry Copper Assessment of Southeast Asia and Melanesia 

polygons; this expanded the area of the tract to include all 

porphyry copper deposits and significant associated prospects 

and accounts for uncertainties in the cartographic position of 

mapped boundaries, as well as possible unexposed or unmapped 

permissive rocks. Digital map units chosen as permissive are 

listed in table C2.

After buffering, the limited available geophysical and 

geochemical information was examined to be sure that any 

other evidence of unmapped permissive rocks or hydrothermal 

systems was included in the tract. A smoothing routine was 

applied to the resulting polygons. Finally, the resulting shapefile 

was clipped to the shoreline to eliminate undersea areas (U.S. 

Department of State, 2009). There are no known Cenozoic 

intrusions in the tract. The tract is shown in figure C1.

Known Deposits

There are no known porphyry copper deposits within the 

tract.

Prospects, Mineral Occurrences, and Related 

Deposit Types

The only significant porphyry copper prospect identified 

in the tract is the Porphyry Creek project (table C3), which 

includes stockwork mineralization on the margins of a Jurassic pluton (Elray Resources, Inc., 2010). Whereas most of the 

exploration activities have been in search of gold deposits and 

many of the mineralized areas probably represent polymetallic 

veins, observations of chalcopyrite-bearing veinlets in propylitically altered quartz diorite porphyry, hydrothermal breccias, and 

porphyritic textures in Jurassic intrusive rocks suggest that a 

porphyry copper system may be present.

Southern Gold, Ltd., is exploring primarily for gold in the 

part of the tract that is in eastern Cambodia, and at their Snoul 

project they have encountered short intervals that grade 0.3–0.5 

percent copper, in addition to significant gold values in an area 

of shallow diorite intrusions (Southern Gold, Ltd., 2010).

Olympus Pacific Minerals, Inc., also is exploring a region 

called Tien Thuan, in southern Vietnam, that may contain porphyry-style mineralization of the appropriate age to be included 

in this tract. This area was discovered by the Geological Survey 

of Vietnam in the 1980s and has been explored primarily for 

gold deposits (Olympus Pacific Minerals, 2010).

There are scattered gold- and copper-bearing skarns, 

polymetallic veins, and a molybdenum-rich porphyry prospect 

(Phnom Basset) in the tract. The team expects that with continued grassroots exploration, more prospects will be discovered.

Exploration History

Throughout much of this tract, exploration for porphyry 

copper deposits is at an early stage. In a 1999 review of copper 

and gold exploration in Southeast Asia, Feebrey (1999) did not 

mention a single one of the deposits and prospects included 

Delineation of the Permissive Tract

Tectonic Setting

Although the Paleozoic plate tectonic history of Southeast Asia is still a matter of some contention, the Jurassic and 

Cretaceous rocks that define the Mekong Delta tract are almost 

certainly related to southwest-directed subduction of the Pacific 

Plate beneath Indochina.

The igneous rocks that define this tract appear to be a 

typical calc-alkaline subduction-related suite. Intrusive rocks 

range in composition from diorite to granite and volcanic rocks 

range in composition from andesite to rhyolite. Thuy and others 

(2004) showed that the rocks in southern Vietnam are metaluminous I-type granitoids that vary in composition from about 56 to 

76 wt. percent silica, and they attributed them to subduction of 

the Pacific Plate below Vietnam. Limited information indicates 

this to be true for the rocks in Cambodia, as well.

Outside the Mekong Delta tract there are a few igneous 

rocks of Jurassic and Cretaceous age that were not included 

in any permissive tract. The age and origin of these excluded 

rocks are uncertain and they do not seem to be associated with 

any important mineral prospects. These include a few granites, 

diorites, and rhyolitic volcanic rocks emplaced along the Red 

River Fault Zone in northern Vietnam and southern Yunnan 

(fig. 5A), a small group of granites and diorites in southernmost 

Yunnan that are scattered between the Red River Fault Zone and 

the eastern margin of a Gangdese-Tethyan tract and a few outcrops of volcanic rocks of varied composition in Malaysia. The 

Malaysian rocks are all within the Malaysia tract and overlie the 

Permo-Triassic permissive rocks there.

Geologic Criteria

The digital geologic map used to select the rocks that 

define the permissive tract is a compilation of digital maps of 

Vietnam, Cambodia, and Lao People’s Democratic Republic 

that were prepared by a group at the University of Tasmania 

(Khin Zaw and others, 1999). The digital geologic map does not 

always reflect the most recent radiometric-age determinations 

or petrologic studies on the rocks in the tract, whose ages are 

not always accurately known. At the same time, many of the 

rocks have not been dated precisely, nor have they been studied 

extensively petrologically. Hence, it is likely that some rocks 

may have been included that are not permissive for porphyry 

copper deposits, either because they are not actually Jurassic 

or Cretaceous in age, or are otherwise not strictly part of the 

volcanic-arc assemblage. Ultramafic rocks and widespread 

areas of dominantly silicic volcanism are excluded.

To define the area included in the permissive tract, the 

assessment team first classified igneous map units as permissive or not, based on the geologic criteria described above; that 

is, calc-alkaline and alkaline volcanic and plutonic rocks of 

Jurassic and Cretaceous ages. To the polygons that represent 

these permissive rocks, a 10-km buffer was applied to plutonicrock polygons and a 2-km buffer was applied to volcanic-rock 
Appendix C—Tract 142pCu7023 79

Table C2. Map units that define tract 142pCu7023, Mekong Delta—Vietnam, Cambodia, and Laos.

[Map unit, age range, and principal lithologies are based on a digital compilation of geologic maps of Thailand and Indonesia (Khin Zaw and others, 1999)]

 Map unit Map symbol Lithology Age range

Intrusive rocks

230-Intrusive rocks (Vietnam) R2-5 Granodiorite, granite, granosyenite Late Mesozoic to early Cenozoic

235-Intrusive rocks (Vietnam) R1-5 Diorite, granodiorite, granite Late Mesozoic to early Cenozoic

532-Diorite and granite (Cambodia) 6 Diorite, granite, monzonite Cretaceous to early Tertiary

533-Dinhquan Complex (Cambodia) 5 Diorite, granodiorite, granites Late Jurassic to Cretaceous

Volcanic rocks

63-Acid volcanics (Vietnam) K Rhyolite Cretaceous

72-Intermediate volcanics (Vietnam) J3-K Andesite Upper Jurassic to Cretaceous

510-Andesite and dacite (Cambodia) J3-K Andesite, dacite, tuffs Upper Jurassic to Cretaceous

512-Undifferentiated acid volcanics (Cambodia) J Felsic volcanic rocks Jurassic

513-Rhyolite and dacite (Cambodia) J Rhyolite and dacite Jurassic

Table C3. Significant prospects and occurrences in tract 142pCu7023, Mekong Delta—Vietnam, Cambodia, and Laos.

Name Latitude Longitude Age Comments Reference

Porphyry 

Creek

13.53 105.13 Jurassic Stockwork mineralization (chalcopyrite) on pluton 

margin.

Elray Resources, Inc. (2010)

Snoul 12.15 106.61 presumed

Mesozoic

Cu and Au mineralization related to diorite intrusions; 

location approximate.

Southern Gold, Ltd. (2010)

Tien Thuan 14.03 108.55 presumed

Mesozoic

Porphyry-style mineralization; location approximate. Olympus Pacific Minerals 

(2010)

in this tract. Vietnam, Lao People’s Democratic Republic, and 

Cambodia have been engulfed in war from the 1940s until 

very recently, and many of the countries are still in the process of developing effective mining laws that support modern mineral exploration activities. Cambodia, for example, 

passed its first mining law in 2001 (Wu, 2002). There is no 

adequate aeromagnetic map of the region, and few regional 

stream-sediment geochemical surveys have been done.

Burrett (1999) indicated that Lao People’s Democratic 

Republic has only begun to be adequately mapped, mostly 

since the mid 1990s, whereas Cambodia and Vietnam 

were mapped by French geologists prior to the 1950s and 

60s. Nevertheless, modern work in these two countries is 

limited.

There has been a steady acceleration of exploration by 

corporate geologists, many from China and Australia, in the 
80 Porphyry Copper Assessment of Southeast Asia and Melanesia

Table C4. Principal sources of information for tract 142pCu7023, Mekong Delta—Vietnam, Cambodia, and Laos.

[NA, not applicable; MMAJ, Metal Mining Agency of Japan; AMIRA, AMIRA International, Ltd. (http://www.amira.com.au/)]

Theme Name or Title Scale Citation

Geology Digital geologic map of East and Southeast Asia 1:2,000,000 CCOP and Geological Survey of Japan (1997)

Digital geologic maps of Myanmar, Laos, Cambodia, 

Thailand, Vietnam, and Yunnan Province, China

1:250,000 

1:500,000

Khin Zaw and others (1999)

Mineral

occurrences

Porphyry copper deposits of the world: database, map, 

and grade and tonnage models

NA Singer and others (2008)

AMIRA database NA Khin Zaw and others (1999)

MMAJ database NA Metal Mining Agency of Japan (1998)

World Minerals Geoscience Database NA Natural Resources Canada (2010)

first decade of the 21st century. The earliest outside workers may have been with CRA Exploration (now Rio Tinto), 

which began work in Lao People’s Democratic Republic in 

1989 (Feebrey, 1999).

Sources of Information

Principal sources of information used by the assessment 

team for delineation of the tract are listed in table C4.

Grade and Tonnage Model Selection

As there is no information about grades of porphyry-style 

mineralization in the tract, combined with the fact that it is a 

fundamentally continental arc, the team chose to use the general porphyry copper model of Singer and others (2008) for 

the assessment of the Mekong Delta tract (table 6).

Estimate of the Number of Undiscovered Deposits

Rationale for the Estimate

There are widespread skarn and porphyry-exploration 

targets related to the Jurassic and Cretaceous plutons in the 

tract, as well as numerous pluton-related gold-bearing veins. 

Most of this tract was not explored between World War II 

and at least the mid-1980s. Modern exploration has been 

done only during the last decade, and the tract is considered 

underexplored. Much of the area is covered with surficial 

deposits or is strongly laterized, making grassroots exploration difficult.

All these factors contributed to the assessment team’s 

estimate that there is at least an even chance that six or 

more undiscovered deposits exist in the tract (table C5). The 

deposit density obtained from the estimate is eight deposits/100,000 km2

, which is somewhat less prospective than 

would be predicted by the global deposit-density model of 

Singer and others (2005).

Probabilistic Assessment Simulation 

Results

Undiscovered resources for the tract were estimated by 

combining the team’s estimate for numbers of undiscovered 

porphyry copper deposits with the porphyry copper-gold model 

of Singer and others (2008) using the EMINERS program 

(Root and others, 1992; Bawiec and Spanski, 2012; Duval, 

2012). Selected simulation results are reported in table C6.

Results of the Monte Carlo simulation are presented as a cumulative frequency plot (fig. C2). The cumulative frequency plot 

shows the estimated resource amounts associated with cumulative probabilities of occurrence, as well as the mean, for each 

commodity and for total mineralized rock.
Appendix C—Tract 142pCu7023 81

References Cited

Bawiec, W.J., and Spanski, G.T., 2012, Quick-start guide for 

version 3.0 of EMINERS—Economic Mineral Resource 

Simulator: U.S. Geological Survey Open-File Report 

2009–1057, 26 p., accessed June 30, 2012, at http://pubs.

usgs.gov/of/2009/1057. (This report supplements USGS OFR 

2004–1344.)

Berger, B.R., Ayuso, R.A., Wynn, J.C., and Seal, R.R., 2008, 

Preliminary model of porphyry copper deposits: U.S. Geological Survey Open-File Report 2008–1321, 55 p., accessed 

May 15, 2009, at http://pubs.usgs.gov/of/2008/1321/.

Burrett, C. F., 1999, Accuracy of geological mapping and crossborder correlations, in Khin Zaw, Burrett, C.F., Berry, R.F., 

and Bruce, E., 1999, Geological, tectonic, and metallogenic 

relations of mineral deposits in mainland Southeast Asia 

(P390A): Australia, University of Tasmania, Centre for Ore 

Deposit Research, School of Earth Sciences, p. 58–62.

Cobbing, E.J., Pitfield, P.E.J., Darbyshire, D.P.F., and Mallick, 

D.I.J., 1992, The granites of the South-East Asian tin belt: 

British Geological Survey, Overseas Memoir 10, 369 p.

Coordinating Committee for Coastal and Offshore Geoscience 

Programmes in East and Southeast Asia (CCOP) and 

Geological Survey of Japan, 1997, Digital geologic map of 

East and Southeast Asia: Geological Survey of Japan, Digital 

Geoscience Map G-2 scale 1:2,000,000, CD-ROM.

Cox, D.P., 1986, Descriptive model of porphyry Cu, in Cox, 

D.P., and Singer, D.A., eds., 1986, Mineral deposit models: 

U.S. Geological Survey Bulletin 1693, p. 76. (Also available 

at http://pubs.usgs.gov/bul/b1693/.)

Duval, J.S., 2012, Version 3.0 of EMINERS—Economic 

Mineral Resource Simulator: U.S. Geological Survey Open 

File Report 2004–1344, accessed July 5, 2012, at http://pubs.

usgs.gov/of/2004/1344.

Elray Resources Inc., 2010, Porphyry Creek project: accessed 

July 1, 2010, at http://www.elraymining.com/documents/

porphyry_project.html.

Feebrey, C.A., 1999, Copper and gold exploration in Southeast Asia: SGA News, no. 7, accessed August 12, 2010, 

at https://www.e-sga.org/fileadmin/sga/newsletter/news7/

art1.html.

Table C5. Undiscovered deposit estimates, deposit numbers, tract area, and deposit density for tract 142pCu7023, Mekong Delta—

Vietnam, Cambodia, and Laos.

[NXX, estimated number of deposits associated with the xxth percentile; Nund, expected number of undiscovered deposits; s, standard deviation; Cv%, coefficient 

of variance; Nknown, number of known deposits in the tract that are included in the grade and tonnage model; Ntotal, total of expected number of deposits plus 

known deposits; km2, area of permissive tract in square kilometers; Ntotal/100k km2, deposit density reported as the total number of deposits per 100,000 km2. 

Nund, s, and Cv% are calculated using a regression equation (Singer and Menzie, 2005)]

 Consensus undiscovered deposit estimates Summary statistics Tract area 

(km2

)

Deposit density 

(Ntotal/100k km2) N90 N50 N10 N05 N01 Nund s Cv% Nknown Ntotal

1 6 16 16 16 7.4 5.4 73 0 7.4 91,220 8

Table C6. Results of Monte Carlo simulations of undiscovered resources for tract 142pCu7023, Mekong Delta—Vietnam, Cambodia, 

and Laos.

[Cu, copper; Mo, molybdenum; Au, gold; and Ag, silver; in metric tons; Rock, in million metric tons]

Material

Probability of at least the indicated amount Probability of

 0.95 0.9 0.5 0.1 0.05 Mean Mean or greater None

Cu 0 650,000 16,000,000 69,000,000 99,000,000 28,000,000 0.34 0.06

Mo 0 0 290,000 2,100,000 3,200,000 790,000 0.28 0.12

Au 0 0 380 1,800 2,400 710 0.34 0.12

Ag 0 0 3,500 24,000 37,000 9,200 0.27 0.17

Rock 0 150 3,600 15,000 20,000 5,700 0.35 0.06
82 Porphyry Copper Assessment of Southeast Asia and Melanesia

John, D.A., Ayuso, R.A., Barton, M.D., Blakely, R.J., Bodnar, 

R.J., Dilles, J.H., Gray, Floyd, Graybeal, F.T., Mars, J.C., 

McPhee, D.K., Seal, R.R., Taylor, R.D., and Vikre, P.G., 

2010, Porphyry copper deposit model, chapter B of Mineral 

deposit models for resource assessment: U.S. Geological 

Survey Scientific Investigations Report 2010–5070–B, 

169 p., accessed January 15, 2011, at http://pubs.usgs.gov/

sir/2010/5070/b/.

Khin Zaw, Burrett, C.F., Berry, R.F., and Bruce, E., 1999, 

Geological, tectonic, and metallogenic relations of mineral 

deposits in mainland Southeast Asia (P390A): Australia, 

University of Tasmania, Centre for Ore deposit Research, 

Project P390A, (unpaginated, includes CD-ROM with GIS 

database). [Proprietary report.]

Metal Mining Agency of Japan (MMAJ), 1998, Mineral 

Resources Map of Asia: Metal Mining Agency of Japan, 

43 p.,1 sheet, scale 1:10,000,000.

Natural Resources Canada, 2010, World minerals geoscience 

database: accessed August 12, 2010, at http://gsc.nrcan.

gc.ca/wmgdb/index_e.php.

Olympus Pacific Minerals, 2010, Tien Thuan project: accessed 

August 12, 2010, at http://www.olympuspacific.com/vietnam-tien-thuan.

Root, D.H., Menzie, W.D., and Scott, W.A., 1992, Computer 

Monte Carlo simulation in quantitative resource estimation: 

Natural Resources Research, v. 1, no. 2, p. 125–138.

Singer, D.A., Berger, V.I., Menzie, W.D., and Berger, B.R., 

2005, Porphyry copper density: Economic Geology, v. 100, 

no. 3, p. 491–514.

Singer, D.A., Berger, V.I., and Moring, B.C., 2008, Porphyry 

copper deposits of the World—Database and grade and 

tonnage models: U.S. Geological Survey Open-File Report 

2008–1155, accessed June 1, 2011, at http://pubs.usgs.gov/

of/2008/1155/. 

Singer, D.A., and Menzie, W.D., 2005, Statistical guides to 

estimating the number of undiscovered mineral deposits—

An example with porphyry copper deposits, in Cheng, 

Qiuming, and Bonham-Carter, Graeme, eds., Proceedings 

of IAMG—The annual conference of the International 

Association for Mathematical Geology: Toronto, Canada, 

York University, Geomatics Research Laboratory, p. 

1028–1033

Southern Gold, Ltd., 2010, Snoul project: accessed August 

12, 2010, at http://www.southerngold.com.au/project.

php?id=32.

Thuy, N., Satir, M., Siebel, W., Vennemann, T., and van Long, 

T., 2004, Geochemical and isotopic constraints on the 

petrogenesis of granitoids from the Dalat zone, southern 

Vietnam: Journal of Asian Earth Sciences, v. 23, p. 467–482.

U.S. Department of State, 2009, Small-scale digital 

international land boundaries (SSIB)—Lines, edition 10, 

and polygons, beta edition 1, in Boundaries and sovereignty 

encyclopedia (B.A.S.E.): U.S. Department of State, Office 

of the Geographer and Global Issues.

Wu, J.C., 2002, The mineral industries of Cambodia and 

Laos: U.S. Geological Survey, 2002 Minerals Yearbook, p. 

7.1–7.5, accessed August 15, 2011, at http://minerals.usgs.

gov/minerals/pubs/country/asia.html#cb.
105° E 110° E

15° N10° N

!

Porphyry Creek

Snoul

Tien 

Thuan

Ho Chi Minh City

THAILAND

VIETNAM

CAMBODIA

LAOS Gulf of Thailand South China Sea

100°E 

20°N10°N

0°

MM

TH

ID

L

M

Political boundary source: U.S. Department of State (2009)Projection: Asia South Albers Equal Area Conic;Central meridian 105° E; latitude of origin 15° S

0 100 50 150 200 KILOMETERS

0 50 100 MILES

E

OthAss142pPorprostrac

Figure C1. Map showing tract location and significant porphyry copper prospects for tract 142pCu7023, Mekong Delta—Vietnam, Cambodia, and 

Lao People’s Democratic Republic; MM, Myanmar; MY, Malaysia; TH, Thailand.
84 Porphyry Copper Assessment of Southeast Asia and Melanesia

Material, in metric tons

0.01 0.1 1 10 100 1k 10k 100k 1M 10M 100M 1B 10B 100B

Probability

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

Mean Cu

Mean Mo

Mean Au

Mean Ag

Mean Rock

Cu

Mo

Au

Ag

Rock

Mean Cu

Mean Mo 

Mean Au

Mean Ag

Mean Rock

EXPLANATION

Figure C2. Cumulative frequency plot showing the results of Monte Carlo computer simulation of undiscovered 

resources in tract 142pCu7023, Mekong Delta—Vietnam, Cambodia, and Laos. k, thousands; M, millions; B, billions; Tr, 

trillions.
Appendix D—Tract 142pCu7024 85

Appendix D. Porphyry Copper Assessment for Tract 142pCu7024, 

Wuntho-Popa—Myanmar and India

By Steve Ludington1, Jane M. Hammarstrom2, and Gilpin R. Robinson, Jr.2, with contributions from Khin Zaw3

and Dennis P. Cox1

1

U.S. Geological Survey, Menlo Park, California, United States.

2

U.S. Geological Survey, Reston, Virginia, United States.

3

University of Tasmania, Hobart, Australia.

Table D1. Summary of selected resource assessment results for tract 142pCu7024, Wuntho-Popa—Myanmar and India.

[km, kilometers; km2, square kilometers; t, metric tons]

Date of 

assessment

Assessment 

depth (km)

Tract area 

(km2)

Known copper 

resources (t)

Mean estimate of

undiscovered copper 

resources (t)

Median estimate

of undiscovered copper

resources (t)

February 2010 1 45,260 6,290,000 8,800,000 1,700,000

Deposit Type Assessed: Porphyry copper

Descriptive model: Porphyry copper (Berger and others, 2008; Cox, 1986; John and others, 2010)

Grade and tonnage model: Porphyry copper, general model (Singer and others, 2008)

Table D1 summarizes selected assessment results.

Location

This tract is primarily in Myanmar and although narrow, may extend for about 1,600 km from north to south, including two 

small volcanic islands (Barren and Narcondam) in the Andaman Sea that belong to India (fig. D1).

Geologic Feature Assessed

A linear belt of Late Cretaceous through Holocene volcanic rocks related to subduction of the Indian Ocean Plate below 

Indochina.

Delineation of the Permissive Tract

Tectonic Setting

The igneous rocks that define the Wuntho-Popa tract are almost certainly related to northeast-directed subduction of the Indian 

subcontinent and the Indian Ocean Plate beneath Indochina along the Sunda subduction zone (Mitchell, 1993; Curray, 2005; Chan-
86 Porphyry Copper Assessment of Southeast Asia and Melanesia

drasekharam and others, 2009). On the mainland of Myanmar, 

this subduction is oblique. The area is called the Wuntho-Popa 

magmatic arc by Mitchell and others (2008) and the Pegu Yoma 

volcanic arc by Fan and Ko (1994). It is the northern continuation of the Sunda Arc.

Geologic Criteria

The few igneous rocks exposed at the surface in this tract 

are primarily mafic calc-alkaline (Mitchell and others, 2008), 

although some of the younger Plio-Pleistocene rocks in this 

belt have alkaline affinities (Maury and others, 2004). The 

granodiorites exposed in the northern part of the belt are as old 

as about 90 Ma (Mitchell, 1993). At the same time, emplacement of some of the younger rocks also may be guided by the 

Sagaing Fault (fig. 5A), a major right-lateral structure that helps 

to accommodate the ongoing northward movement of the Indian 

Ocean Plate.

In the Andaman Sea, rocks on Barren Island (fig. D1) 

range in composition from basalt to andesite, whereas those on 

Narcondam Island (fig. D1) include andesite and dacite (Chandrasekharam and others, 2009).

Unexposed Miocene (and possibly older) volcanic rocks 

may be present at shallow depths along the axis of the Eastern 

Volcanic Line, as depicted by Myint (1994). The team used the 

inferred position of that line to delineate a narrow corridor as permissive. Because volcanic rocks may be present at shallow depth 

beneath the Irrawaddy River floodplain and delta sediments, this 

subjective delineation was used rather than the more conventional 

buffering of volcanic outcrops. The permissive map units chosen 

are characterized as code 29, Cenozoic volcanic rocks on the 

digital geologic map used (Khin Zaw and others, 1999), although 

some of these outcrops are older (Mitchell, 1993).

The team also examined the limited geophysical and 

geochemical information to be sure that any other evidence 

of unmapped permissive rocks or hydrothermal systems was 

included. Finally, the resulting shapefile was clipped to the 

shoreline to eliminate undersea areas (U.S. Department of State, 

2009). There are no known Cenozoic intrusions in the tract. The 

tract is shown in figure D1.

Known Deposits

The single known porphyry copper deposit, Monywa (fig. 

D1, table D2), is atypical in that most of the ore delineated is 

enriched by supergene processes and it is exposed at a very shallow level. The deposit has been classified in a variety of ways 

(Nansatsu-type massive sulfide, transitional between Kuroko 

massive sulfide and porphyry copper, supergene-enriched 

porphyry copper, high-sulfidation (copper-rich) epithermal); the 

team sided with Sillitoe (United Nations, 1978) and Singer and 

others (2008) and considers it to be a porphyry copper deposit 

for the purposes of this assessment. The description of Monywa 

is primarily from Mitchell and others (2008), but there are also 

descriptions in Krisl (1975) and Winn and Kirwin (1998).

Monywa consists of four mineralized areas that are in close 

proximity, Sabetaung, Sabetaung South (both presently in 

production), Kyisintaung, and Letpadaung (both unmined). The 

total resource at Monywa has not been finally delineated, but 

it is in the neighborhood of 2,000,000,000 tons, with a copper 

grade of about 0.35 percent [Singer and others (2008) list it as 

1,700,000,000 tons at 0.37 percent copper]. Precious metals 

are not recovered from the oxide material now being mined by 

heap-leach and processed by solvent extraction-electrowinning 

(SX-EW) methods. However, samples from drill core at the 

Kyisintaung deposit averaged 0.15 g/t gold and 23 g/t silver. The 

deposit appears to have been formed in the late Miocene.

Prospects, Mineral Occurrences, and Related 

Deposit Types

The most important prospect in the area is Shangalon (fig. 

D1, table D3), which is Eocene in age (Goossens, 1977, 1978; 

Win and Myint, 1998). This area was drilled by the Burmese 

government (with the help of the United Nations Development 

Program) in the mid-1970s, and a possible (only partly delineated) resource of about 9,000,000 t with copper grade of 0.23 

percent was reported (Singer and others, 2008). Although not 

included in the resource, the deposit contains both molybdenum 

and gold. The area was further explored by Ivanhoe (who was 

developing Monywa at the time) in the mid-1990s before they 

left the country.

Most major outcrop areas of volcanic rock within the tract 

have either porphyry copper prospects or epithermal preciousmetal mineralization, all poorly documented (Win and Myint, 

1998).

Exploration History

Geologists of the British Geological Survey mapped Myanmar, but there has been little activity since 1939 (Burrett, 1999). 

Systematic modern geologic mapping, regional stream-sediment 

surveys, and airborne geophysical data are lacking.

Western mineral-exploration groups began to operate in 

the country in the 1980s, but this work came to an end recently 

because of political factors (Ivanhoe Mines, 2010). Other foreign 

companies, notably from China and India, continue to operate in 

Myanmar (Global Times, 2010).

Sources of Information

Principal sources of information used by the assessment 

team for delineation of the tract are listed in table D4.

Grade and Tonnage Model Selection

As there is no reliable information about gold grades of 

porphyry-style mineralization in the tract, we chose to use the 
Appendix D—Tract 142pCu7024 87

Table D2. Identified porphyry copper resources in tract 142pCu7024, Wuntho-Popa—Myanmar and India.

[Ma, million years; Mt, million metric tons; t, metric ton; %, percent; g/t, gram per metric ton; Cu-Mo subtype, deposits that have Au/Mo ratios <3 or average 

Mo grades >0.03 percent; Cu-Au subtype, deposits that have Au/Mo ratios >30 or average Au grades >0.2 g/t; n.d., no data, NA, not applicable. Contained Cu 

in metric tons is computed as tonnage (Mt × 1,000,000) × Cu grade (percent)]

Name Latitude Longitude Subtype Age (Ma) Tonnage 

(Mt) Cu (%) Mo (%) Au (g/t) Ag (g/t) Contained 

Cu (t) Reference

Monywa 22.13 95.041 NA Late

Miocene

1,700 0.37 n.d. n.d. n.d. 6,290,000 Mitchell and 

others (2008)

Table D3. Significant prospects and occurrences in tract 142pCu7024, Wuntho-Popa—Myanmar and India.

[Ma, million years; %, percent; Mt, million metric tons]

Name Latitude Longitude Age (Ma) Comments Reference

Shangalon 23.71 95.52 Eocene Partly delineated resource of about 9 

Mt at 0.23% Cu; contains Mo and Au. Win and Myint (1998)

Table D4. Principal sources of information for tract 142pCu7024, Wuntho-Popa—Myanmar and India.

[NA, not applicable]

Theme Name or title Scale Citation

Geology Digital geologic map of East and Southeast Asia 1:2,000,000 CCOP and Geological Survey of Japan (1997)

Digital geologic map of Myanmar 1:500,000 Khin Zaw and others (1999)

Mineral

occurrences

Porphyry copper deposits of the world: database, map, and 

grade and tonnage models

NA Singer and others (2008)

AMIRA database NA Khin Zaw and others (1999)

MMAJ database NA Metal Mining Agency of Japan (1998)

World Minerals Geoscience Database NA Natural Resources Canada (2010)

general porphyry copper model of Singer and others (2008) for 

the assessment of the Wuntho-Popa tract (table 6). The magmatic arc in mainland Myanmar probably should be considered 

a continental arc. At the present day, the subduction zone in 

Myanmar is still continent against continent.

Estimate of the Number of Undiscovered Deposits

Rationale for the Estimate

There is one large deposit (Monywa) and one significant 

prospect (Shangalon) in the tract, along with numerous other 

porphyry, skarn, and epithermal prospects. Because modern 

geophysical methods have not been employed to search for 

shallow intrusions, and because there is little active exploration, 

this tract can be considered to be underexplored. However, the 

presence of porphyry copper and epithermal prospects suggests 

that this tract could be prospective. The assessment of this tract 

is problematic because there is no reliable way to estimate how 

thick the cover may be over any buried (and potentially mineralized) volcanic rocks and hypabyssal intrusions.

All these factors contributed to the assessment team’s 

estimate that there is at least an even chance that an undiscovered deposit exists in the tract and that there could be as many 

as nine undiscovered deposits (table D5). The deposit density 

obtained from the team estimate is seven deposits/100,000 
88 Porphyry Copper Assessment of Southeast Asia and Melanesia

km2, which is somewhat less prospective than would be 

predicted by the global deposit-density model of Singer and 

others (2005).

Probabilistic Assessment Simulation 

Results

Undiscovered resources for the tract were estimated by 

combining the team’s estimate for numbers of undiscovered 

porphyry copper deposits with the general porphyry copper model of Singer and others (2008) using the EMINERS 

program (Root and others, 1992; Bawiec and Spanski, 2012; 

Duval, 2012). Selected simulation results are reported in table 

D6. Results of the Monte Carlo simulation are presented as a 

cumulative frequency plot (fig. D2). The cumulative frequency 

plot shows the estimated resource amounts associated with 

cumulative probabilities of occurrence, as well as the mean, 

for each commodity and for total mineralized rock.

References Cited

Bawiec, W.J., and Spanski, G.T., 2012, Quick-start guide for 

version 3.0 of EMINERS—Economic Mineral Resource 

Simulator: U.S. Geological Survey Open-File Report 

2009–1057, 26 p., accessed June 30, 2012, at http://pubs.

usgs.gov/of/2009/1057. (This report supplements USGS 

OFR 2004–1344.)

Berger, B.R., Ayuso, R.A., Wynn, J.C., and Seal, R.R., 

2008, Preliminary model of porphyry copper deposits: 

U.S. Geological Survey Open-File Report 2008–1321, 

55 p., accessed May 15, 2009, at http://pubs.usgs.gov/

of/2008/1321.

Burrett, C. F., 1999, Accuracy of geological mapping and 

cross-border correlations, in Khin Zaw, Burrett, C.F., 

Berry, R.F., and Bruce, E., 1999, Geological, tectonic, and 

metallogenic relations of mineral deposits in mainland 

Southeast Asia (P390A): Australia, University of Tasmania, Centre for Ore Deposit Research, School of Earth 

Sciences, p. 58–62.

Chandrasekharam, D., Santo, A.P., Capaccioni, B., Vaselli, 

O., Alam, M.A., Manetti, P., and Tassi, F., 2009, Volcanological and petrological evolution of Barren Island (Andaman Sea, Indian Ocean): Journal of Asian Earth Sciences, 

v. 35, p. 469–487.

Coordinating Committee for Coastal and Offshore Geoscience Programmes in East and Southeast Asia (CCOP) and 

Geological Survey of Japan, 1997, Digital geologic map 

of East and Southeast Asia: Geological Survey of Japan, 

Digital Geoscience Map G-2 scale 1:2,000,000, CD-ROM.

Table D6. Results of Monte Carlo simulations of undiscovered resources for tract 142pCu7024, Wuntho-Popa—Myanmar and India.

[Cu, copper; Mo, molybdenum; Au, gold; and Ag, silver; in metric tons; Rock, in million metric tons]

Material

Probability of at least the indicated amount Probability of

0.95 0.9 0.5 0.1 0.05 Mean Mean or 

greater

None

Cu 0 0 1,700,000 22,000,000 40,000,000 8,800,000 0.25 0.29

Mo 0 0 9,700 590,000 1,300,000 250,000 0.19 0.45

Au 0 0 23 620 1,000 230 0.24 0.42

Ag 0 0 0 6.900 14,000 3,000 0.19 0.52

Rock 0 0 400 4,700 8,300 1,800 0.26 0.29

Table D5. Undiscovered deposit estimates, deposit numbers, tract area, and deposit density for tract 142pCu7024, Wuntho-Popa—

Myanmar and India.

[NXX, estimated number of deposits associated with the xxth percentile; Nund, expected number of undiscovered deposits; s, standard deviation; Cv%, coefficient 

of variance; Nknown, number of known deposits in the tract that are included in the grade and tonnage model; Ntotal, total of expected number of deposits plus 

known deposits; km2, area of permissive tract in square kilometers; Ntotal/100k km2, deposit density reported as the total number of deposits per 100,000 km2. 

Nund, s, and Cv% are calculated using a regression equation (Singer and Menzie, 2005)]

Consensus undiscovered 

deposit estimates Summary statistics Tract area 

(km2

)

Deposit density 

(Ntotal/100k km2)

N90 N50 N10 N05 N01 Nund s Cv% Nknown Ntotal

0 1 5 9 9 2.2 2.7 120 1 3.2 45,260 7
Appendix D—Tract 142pCu7024 89

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D.P., and Singer, D.A., eds., 1986, Mineral deposit models: 

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Resource Simulator: U.S. Geological Survey Open File Report 

2004–1344, accessed July 5, 2012, at 

http://pubs.usgs.gov/of/2004/1344.

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definitions, geologic relationships and extension into China, India 

and Thailand, in Nutalaya, P., ed., Geology and mineral resources 

of Southeast Asia: Proceedings of the 3rd Regional Conference 

GEOSEA, Bangkok, p. 431–536.

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copper deposit (Burma), Mineralium Deposita 12, 37–47 (1977): 

Mineralium Deposita, v. 13, p. 275–277.

Ivanhoe Mines, 2010, Fact file—The Monywa copper project: 

accessed August 12, 2010, at http://www.Ivanhoemines.com/pdf/

Monywa-Fact-file.pdf.

Khin Zaw, Burrett, C.F., Berry, R.F., and Bruce, E., 1999, Geological, 

tectonic, and metallogenic relations of mineral deposits in 

mainland Southeast Asia (P390A): Australia, University of 

Tasmania, Centre for Ore Deposit Research, Project P390A, 

(unpaginated, includes CD-ROM with GIS database). [Proprietary 

report.]

Krisl, P.H., 1975, Geology of the NW-part of Monywa copper area 

(Lower Chindwin District, Burma): Post-graduate training in 

mineral exploration, BUR/76/516, Rangoon Arts and Science 

University, Rangoon.

Maury, R.C., Pubellier, M., Rangin, C., Wulput, L., Cotton, J., 

Socquet, A., Bellon, H., Guillaud, J-Ph., and Htun, H.M., 2004, 

Quaternary calc-alkaline and alkaline volcanism in an hyperoblique convergence setting—Central Myanmar and western 

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the western Myanmar (Burma)-Assam region: Journal of the 

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Mitchell, A.H.G., Myint, W., Lynn, K., Htay, M.T., Oo, 

M., and Zaw, T., 2008, The Monywa copper deposits, 

Myanmar—Chalcocite-covellite veins and breccia dykes 

in a Late Miocene epithermal system: Proceedings of the 

International Symposia on Geoscience Resources and 

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Natural Resources Research, v. 1, no. 2, p. 125–138.

Singer, D.A., Berger, V.I., Menzie, W.D., and Berger, B.R., 

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no. 3, p. 491–514.

Singer, D.A., Berger, V.I., and Moring, B.C., 2008, Porphyry 

copper deposits of the world—Database and grade and 

tonnage models, 2008: U.S. Geological Survey Open-File 

Report 2008–1155, accessed June 1, 2011, at http://pubs.

usgs.gov/of/2008/1155/.

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estimating the number of undiscovered mineral deposits—An 

example with porphyry copper deposits, in Cheng, Qiuming, 

and Bonham-Carter, Graeme, eds., Proceedings of IAMG—

The annual conference of the International Association for 

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boundaries (SSIB)—Lines, edition 10, and polygons, beta edition 

1, in Boundaries and sovereignty encyclopedia (B.A.S.E.): U.S. 

Department of State, Office of the Geographer and Global Issues.

Win, S., and Myint, M.M., 1998, Mineral potential of Myanmar: 

Resource Geology, v. 48, p. 209–218.

Winn, K., and Kirwin, D.J., 1998, Exploration, geology, and 

mineralization of the Monywa copper deposits, central 

Myanmar, in Porphyry and hydrothermal copper and gold 

deposits—A global perspective: Perth, Proceedings of the 

Australian Mineral Foundation Conference, p. 61–74.
90 Porphyry Copper Assessment of Southeast Asia and Melanesia

!

!

!

MYANMAR

INDIA

INDIA

CHINA

THAILAND

Rangoon

Shangalon

Monywa

94°E 98°E

26°N

18°N

Narcondam Island

Barren Island

CHINA

90°E 100°E

30°N

20°N

10°N

Political boundary source U.S. Department of State (2009)

Projection: Asia South Albers Equal Area Conic;

Central meridian 95° E; latitude of origin 15° S

0 50 100 150 200 KILOMETERS

0 50 100 MILES

EXPLANATION

Porphyry copper

Porphyry copper deposit

Assessed porphyry copper tract

142pCu7024

Other porphyry copper tracts

Porphyry copper prospect

Area 

of 

Map

Figure D1. Map showing tract location, deposit, and significant porphyry copper prospects for tract 142pCu7024, 

Wuntho-Popa—Myanmar and India.
References Cited 91

Material, in metric tons

0.01 0.1 1 10 100 1k 10k 100k 1M 10M 100M 1B 10B 100B

Probability

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

Mean Rock

Mean Ag

Mean Au

Mean Mo

Mean Cu

Cu

Mo

Au

Ag

Rock

Mean Cu

Mean Mo 

Mean Au

Mean Ag

Mean Rock

EXPLANATION

Figure D2. Cumulative frequency plot showing the results of Monte Carlo computer simulation of undiscovered 

resources in tract 142pCu7024, Wuntho-Popa—Myanmar and India. k, thousands; M, millions; B, billions; Tr, trillions.
92 Porphyry Copper Assessment of Southeast Asia and Melanesia 

Appendix E. Porphyry Copper Assessment for Tract 142pCu7020, 

Sumatra Island—Indonesia

By Gilpin R. Robinson, Jr.1, Jane M. Hammarstrom1, Steve Ludington2, Arthur A. Bookstrom3, Alexander Yan 

Sze Wah4

, Bambang Tjahjono Setiabudi5, Dwi Nugroho Sunuhadi3, Sewit A. Yenie1, and Michael L. Zientek3, 

with contributions from Chen Shick Pei6

Deposit Type Assessed: Porphyry copper

Descriptive model: Porphyry copper (Cox, 1986; Berger and others, 2008; John and others, 2010)

Grade and tonnage model: Porphyry copper, general model (Singer and others, 2008)

Table E1 summarizes selected assessment results.

Table E1. Summary of selected resource assessment results for tract 142pCu7020, Sumatra Island—Indonesia.

[km, kilometers; km2, square kilometers; t, metric tons]

Date of 

assessment

Assessment 

depth (km)

Tract area 

(km2)

Known copper 

resources (t)

Mean estimate of 

undiscovered copper 

resources (t)

Median estimate of

undiscovered copper

resources (t)

February 

2010 1 131,030 900,000 23,000,000 13,000,000

Location

The tract includes western Sumatra Island from the northern tip to the southern tip (fig. E1).

Geologic Feature Assessed

An Eocene-Pliocene continental magmatic arc that straddles the northwest-trending Sumatran Fault Zone in 

western Sumatra.

1

U.S. Geological Survey, Reston, Virginia, United States.

2

U.S. Geological Survey, Menlo Park, California, United States.

3

U.S. Geological Survey, Spokane, Washington, United States.

4

Minerals and Geoscience Department, Sabah, Malaysia.

5

Directorate of Mineral Resources Inventory, Geological Agency of Indonesia, Bandung, Indonesia.

6

Coordinating Committee for Geoscience Programmes in East and Southeast Asia (CCOP) Technical Secretariat, Bangkok, Thailand.
Appendix E—Tract 142pCu7020 93

Delineation of the Permissive Tract

Tectonic Setting

The mid- to late Tertiary porphyry copper tract on Sumatra 

Island incorporates a magmatic arc developed in response to 

oblique subduction of the Indian Plate under continental crust 

of the Sundaland part of the Eurasian Plate (Garwin and others, 

2005). The tract includes Eocene to Pliocene intrusive- and 

volcanic-rock units but excludes thick overlying Quaternary 

volcanic and sedimentary units. The intrusive centers and the 

porphyry copper deposits and prospects are localized along the 

right-lateral Sumatran Fault system (fig. E2) that initiated during the Miocene in response to oblique subduction (Barber and 

others, 2005).

The Sumatra Island tract is the northwestern part of the 

3,800-km-long Eocene to Holocene Sunda-Banda magmatic 

arc (fig. 5B,C). The Sunda-Banda magmatic arc stretches 

from Sumatra to the easternmost part of the Sunda-Banda Arc 

northeast of Timor (fig. 5C). The western boundary of the 

Sumatra Island tract is the Indian Ocean; the eastern boundary 

overlaps but is near the northwest-striking right-lateral, strikeslip Sumatra Fault system that structurally localized many of the 

Tertiary intrusive centers and where the tract is overlain by thick 

sequences of Quaternary sedimentary and volcanic rocks to the 

northeast. The southeastern termination of the tract occurs at the 

Sunda Strait that separates Sumatra Island from Java (fig. E2, 

fig. 5C). The Sunda Strait is an extensional basin formed at the 

transition from oblique subduction to the northwest along the 

Sunda Trench to frontal subduction to the east along the Java 

Trench (Huchon and Le Pichon, 1984).

Geologic Criteria

The geologic units that define the permissive tract, shown 

in figure E3, are calc-alkaline igneous rocks of Eocene to Pliocene age (most are mid-Miocene). Igneous rock map units of 

uncertain age, that span this age range but may be as old as Cretaceous, are included in the tract. Most of the plutonic rocks that 

crop out within the tract are numerous small bodies of dioritegranodiorite (some porphyritic) and a few granite-granodiorite 

bodies (table E2). The chemistry of these rocks is calc-alkaline, 

but some sodic variants known as adakites are present (Barber 

and others, 2005).

Calc-alkaline volcanic rocks are considered permissive 

for porphyry copper deposits as they are localized near 

and often overlie intrusive centers that may host porphyry 

deposits and may include small unmapped intrusive bodies 

within their borders. The volcanic rocks that define the tract 

include andesite flows and tuffs, dacite and associated dacitic 

tuffs and breccias, and basalt flows (table E2). Two areas 

of volcanoclastic sediments in northern Sumatra have been 

included as they delineate probable intrusive centers that are 

not identified by volcanic rocks alone. Mid-Tertiary bimodal 

rhyolite-basalt sequences and andesitic tuffs that are primarily 

within marine carbonate rocks (fringing reefs bordering 

the oceanic islands) or clastic sedimentary rocks have been 

excluded from the tract. These distal volcanic deposits in 

carbonates and sediments are interpreted to be part of the 

accretionary-wedge complex, and their sites of deposition were 

not likely to be near the intrusive centers that host porphyry 

copper deposits. A few high-K alkaline-series volcanic rocks 

occur in a back-arc setting (Barber and others, 2005).

The team used 1:250,000-scale geologic maps (table E2; 

Geological Research and Development Centre, 1987–2000) to 

identify areas of permissive rock types, based on the map legend 

attribute information describing map-unit rock types, composition, and age. The maps were scanned and rectified, and the 

areas of permissive rock units were digitized by hand to build 

an attributed digital GIS file used to define the permissive tract. 

After choosing the polygons and groups of polygons that represent the surface expressions of permissive igneous intrusions, 

a 10-km buffer was applied to account for a spatial uncertainty 

of approximately 2 km in the digitized geology and deposit 

location data and the possibility that deposits may be associated 

with intrusions that expand beneath their surface expression and 

are also less than 1 kilometer beneath the land surface. A 2-km 

buffer was applied around the permissive volcanic units, as 

these may be imprecisely located and partly covered. A polygon 

aggregation and smoothing process was applied to the revised 

buffered permissive geologic map units to produce a preliminary permissive tract. The processing approximates manual 

delineation of a tract but is rapid and reproducible. The processing steps include (1) unioning all permissive unit buffers and 

other polygon features that comprise the framework of the tract, 

(2) aggregating unioned polygons using an aggregation distance 

of 50 km and a minimum hole size of 2,000 km2

, (3) simplifying the aggregated polygons using a bend-simplify algorithm 

with a simplification tolerance of 5 km, and (4) line-smoothing 

the simplified polygons using an algorithm (PAEK, polynomial 

approximation with exponential kernel) with a tolerance of 20 

km. Necking, thinning and contraction of the polygons resulting 

from the above processing necessitated manual cleaning of the 

preliminary tract (for example, polygon necks removed). Final 

tracts were compared to the permissive geologic features in 

source maps to ensure that original permissive boundaries were 

honored. All operations were carried out in ArcGIS 9.3 using 

standard tools available in the Arc Toolbox.

These revised preliminary tract polygons were further 

modified by comparison with the scanned and rectified geologic 

maps to exclude areas where Quaternary volcanic rocks and 

sedimentary deposits are greater than 1 km in thickness. The 

resulting tract shapefile was clipped to the shoreline to eliminate 

undersea areas (U.S. Department of State, 2009).

The use of a polygon-aggregation distance of 50 km resulted 

in a tract outline consistent with the expectation of the Indonesian geologic expert, Bambang Tjahjono Setiabudi, and with the 

distribution of copper and gold occurrences in mineral-occurrence 

the Indonesia databases (Coordinating Committee for Geoscience 

Programmes in East and Southeast Asia (CCOP), 1997; Directorate of Mineral Resources and Inventory, 2004a,b). The distribution of these mineral occurrences was not used to delineate tract 
94 Porphyry Copper Assessment of Southeast Asia and Melanesia

Table E2. Map units that define tract 142pCu7020, Sumatra Island—Indonesia.

[Geologic map, map unit, geologic-age range, and principal rock types from 1:250,000 scale geologic maps, compiled by the Geological Research and Development Centre, Badung, Indonesia, 1987–2000]

Geologic map Map unit Age range Rock types

Intrusive rocks

420 Tmiu Pliocene to Miocene Diorite-granodiorite

0421-0521 Tii Oligocene Microdiorite

0421-0521 Tir Oligocene Diorite-melanodiorite

0421-0521 TMi Cretaceous to Oligocene Granodiorite, diorite

0421-0521 TMigs Cretaceous to Oligocene Granodiorite, gabbro

0421-0521 Tmiu Middle to late Miocene Diorite-granodiorite

520 Tib Early to late Oligocene Bateekeubeue intrusion

520 Tibm Middle Miocene Granodiorite

520 Tid Early to middle Miocene Diorite

520 Tit Middle Miocene Diorite to granodiorite

618 Tmip Middle to late Miocene Quartz microdiorite

618 Tmit Middle to late Miocene Diorite, microdiorite

618 Tmvp Middle to late Miocene Dolerite sills

619 Tmig Middle Miocene Microdiorite

619 Tmis Middle Miocene Microdiorite

620 Til Middle Miocene Leucogranite

0617-0717 Tlih Paleogene Fine-grained granite porphyry

0617-0717 Tliu Paleogene? Granodiorite, diorite

0617-0717 Tmi Miocene Microdiorite, diorite

0617-0717 Tmisi Miocene Granodioritic to dioritic

0617-0717 Tmiti Miocene Granodiorite

715 Tgr Eocene and Oligocene Granite, quartz diorite

716 TMi Eocene and Oligocene Granodiorite-granite

716 TMiab Eocene and Oligocene Granodiorite, Adamellite

716 Tmibi Miocene Subvolcanic microgranites

716 Tmid Miocene Subvolcanic porph. microdiorites

716 TMik Eocene and Oligocene Leucogranite, granodiorite

716 TMimn Eocene and Oligocene Granodiorite, granite

716 Tmipl Miocene Granodiorite, diorite

716 Tmisp Miocene Subvolcanic porph. microdiorites

716 Tmiti Miocene Granodiorite

716 TMiu Eocene and Oligocene Granodiorite

716 Tuim Pliocene Feldspar granite porphyry

718 Tmi Miocene Diorite

718 Tmitj Miocene Diorite

0714-0814 Tdb Miocene Diabase dikes and sills

0714-0814 Tgdr Miocene Hornblende granite-granodiorite

0714-0814 Tgr Miocene Biotite granite, granite porphyry

0813-0812 Tmda Miocene Dacite

0813-0812 Tmdi Miocene Diorite
Appendix E—Tract 142pCu7020 95

0813-0812 Tpgdl Pliocene Granodiorite

0813-0812 Tpgds Pliocene Granodiorite

0813-0812 Tpgr Pliocene Granite

0911-0910 Tmdi Middle Miocene Diorite

0911-0910 Tmg Middle Miocene Granite

912 Tmdi Middle Miocene Diorite

912 Tmgr Middle Miocene Granite

912 Tpan Pliocene Andesite

913 Tmdi Middle Miocene Diorite (chloritized)

913 Tpgr Pliocene Granite, granodiorite

1010 Tm Middle Miocene Granite, granodiorite-diorite

1110 Tejg Eocene Granite

1110 Tmda Oligocene to early Miocene Dacite

1110 Tmgr Oligocene to early Miocene Granite, granodiorite

Volcanic rocks

0421-0521 Tmvc Middle to late Miocene Intermediate volcanics

519 Tlva Oligocene to Miocene Andesite, basalt

519 Tlvs Oligocene to Miocene Felsic, intermediate and mafic lava

520 Tmvc Late Miocene Felsic volcanics (reworked)

618 Tmvh Middle to late Miocene Andesite, dacites

618 Tmvo Middle to late Miocene Andesitic agglomerates

618 Tmvp Middle to late Miocene Andesite

618 Tmvt Middle to late Miocene Andesitic volcanics

619 Tlvk Early Miocene Andesite

619 Tmva Middle Miocene Andesite

619 Tmvt Middle Miocene Andesite

620 Tlvm Early Miocene Felsic to intermediate pyroclastics

715 Ta Eocene and Oligocene Andesite (basaltic)

716 Tlvl Eocene and Oligocene Porphyritic pyroxene absarokitic lavas

716 Tmv Miocene Undifferentiated volcanics

716 Tmvab Miocene Porphyritic andesites

716 Tmvam Miocene Intermediate volcaniclastics and lava

716 Tmvsg Miocene Porphyritic andesites

716 Tmvsk1 Miocene Andesite lava

716 Tmvsk2 Miocene Reworked volcanic deposits

716 Tuvm Pliocene Acid to basic lavas

0617-0717 Tlis Late Eocene Porphyritic andesites, microdiorite

0617-0717 Tmva Miocene Andesite

0617-0717 Tmvak Miocene Andesite, basalt

0617-0717 Tmvna Miocene Intermediate volcanics

0617-0717 Tmvp Miocene Andesite, basalt

0714-0814 Tb Eocene to Oligocene Ignimbrite, tuff

Table E2. Map units that define tract 142pCu7020, Sumatra Island—Indonesia.—Continued

Geologic map Map unit Age range Rock types

Intrusive rocks
96 Porphyry Copper Assessment of Southeast Asia and Melanesia

0617-0717 Tmvp Miocene Andesite, basalt

0714-0814 Tb Eocene to Oligocene Ignimbrite, tuff

0714-0814 Tomp Miocene to Oligocene Intermediate volcanics

718 Tmvh Miocene Andesite-dacite

718 Tmvo Miocene Andesite

718 Tuvs Miocene to Pliocene Andesite

718 Tuvsu Miocene to Pliocene Andesite

0813-0812 Tomh Oligocene Andesite

815 Ta Miocene Andesite

0911-0910 Tmba Middle to late Miocene Dacitic volcanic breccia

0911-0910 Tml Middle to late Miocene Dacitic breccia

0911-0910 Tmpl Pliocene Andesitic to basaltic volcanic breccia

0911-0910 Tomh Oligocene to early Miocene Andesite-basalt lavas

912 Tmba Late Miocene Dacite volcanic breccia

912 Tml Late Miocene Dacite breccia

912 Tmpl Pliocene Epiclastic volcanic breccia

912 Tomh Oligocene to early Miocene Andesite-basalt lavas

912 Tpok Paleocene to Oligocene Volcanic breccia

913 Tmba Late Miocene Dacite tuff

913 Tomh Oligocene to early Miocene Volcanic breccia

1010 Tmba Middle to late Miocene Dacitic volcanic breccias

1010 Tmpl Pliocene to late Miocene Andesite, Dacite tuffs

1010 Tomh Oligocene to early Miocene Volcanic breccia

1010 Tpok Oligocene-Paleocene Andesite breccia

1011 Tmba Middle to late Miocene Dacitic volcanic breccia

1011 Tmpl Late Miocene to Pliocene Basalt-andesite

1011 Tomh Early Miocene-Oligocene Andesite-basalt

1011 Tpok Paleocene to Oligocene Volcanic breccia

1017-1016 Tma Miocene Andesite

1110 Tomh Miocene to early Oligocene Andesite-basalt

1110 Tpv Pliocene Andesite

boundaries; however, the locations of (1) major and minor copper 

deposits, prospects, and occurrences, and (2) hydrothermal goldcopper deposits and prospects lacking lead as a secondary commodity or galena, as a prominent mineral, listed in the Indonesian 

mineral-occurrence database, are localized within the Sumatra 

Island tract. Two areas of hydrothermal gold-copper veins that 

list lead as a significant commodity or galena as a common vein 

mineral in the mineral-occurrence databases occur in sedimentary 

and metasedimentary rocks located outside of the tract. These 

lead-bearing vein occurrences are in 1:250,000-scale maps sheets 

(map numbers 0914 and 0915, Geological Research and Development Center, 1987–2000) that lack identified intrusive- and 

volcanic-rock units considered permissive for porphyry copper 

deposits, are located more than 60 km east of the nearest bodies of permissive volcanic rocks, and are more than 150 km east 

of the Sumatran Fault system that has localized the distribution 

of the igneous systems associated with known porphyry copper deposits and prospects in the tract. The lead-bearing veins 

occur in Quaternary to late Tertiary sedimentary rocks, primarily 

sandstones, mudstones, and marls with minor tuffaceous volcaTable E2. Map units that define tract 142pCu7020, Sumatra Island—Indonesia.—Continued

Geologic map Map unit Age range Rock types

Intrusive rocks
Appendix E—Tract 142pCu7020 97

nic beds, deposited on Jurassic igneous and metamorphic rock 

continental basement. Based on interpretative geologic cross 

sections through these map areas, the sedimentary rock sections 

hosting the vein occurrences are greater than 1 km in thickness. 

The sedimentary rocks are overlain by Quaternary alluvial sediments in many areas. The lead-bearing veins probably represent 

polymetallic vein systems that are unrelated to porphyry systems 

and are not likely to be proximal to buried porphyry systems. The 

Sumatra Island tract includes at least five national parks and a 

number of nature reserves.

Known Deposits

The only known porphyry copper deposit is the Miocene 

Tangse porphyry copper-molybdenum deposit located in the 

northern part of the Sumatra Island tract (fig. E1; table E3). At 

Tangse, an outcrop of stockwork-altered porphyry was discovered during a British-Indonesian government sponsored regional 

geologic mapping and exploration geochemistry program in 

1976. The discovery was followed by soil sampling, geophysical studies, and exploratory drilling between 1979 and 1981 (van 

Leeuwen, 1994). The exploration program identified a zone of 

anomalous copper concentrations in a 5-km-long and 1–2-kmwide zone of altered, fractured, and leached porphyry stock (van 

Leeuwen and others, 1987). The Tangse deposit is hosted in a 

zone of intrusive and volcanic rocks localized by the northwesttrending Sumatran Fault Zone (figs. E2 and E3) that traverses the 

length of Sumatra. The copper-molybdenum mineralization is 

hosted in a multiphase quartz diorite stock, and the development 

of alteration and mineralization occurred between 13 and 9 Ma 

(van Leeuwen, 1994). Although early potassic alteration (biotite), 

overprinted by phyllic alteration (sericite-quartz) and associated 

sulfide mineralization, in turn overprinted and surrounded by 

propylitic alteration (chlorite-epidote-carbonate), is continuous in 

the overall deposit area, subeconomic to economic copper grades 

are irregular in distribution (van Leeuwen and others, 1987), and 

the deposit has not been mined. Reserve-resource estimates are 

600 million tons of low-grade material at 0.15 percent copper 

(table E3), including 30 million tons of ore at 0.3–0.6 percent 

copper and 0.02–0.03 percent molybdenum (van Leeuwen and 

others, 1987). Oxidation and leaching of the deposit has resulted 

in patchy development of supergene copper enrichment (Taylor 

and van Leeuwen, 1980).

Prospects, Mineral Occurrences, and Related 

Deposit Types

In addition to Tangse, there are four or five main clusters of additional porphyry copper prospects and occurrences 

representing about a dozen prospects and occurrences in the 

Sumatra Island tract (table E4; Directorate of Mineral Resources 

Inventory, Bandung, Indonesia, written commun., 2004), which 

contain copper, gold, molybdenum, and base metals. The Mudik 

copper-gold porphyry prospect was identified in the early 1970s 

by regional stream-sediment sampling. Prospecting in the vicinity of geochemical anomalies at Mudik found numerous brecciated pyritic boulders, spread over a 2 km2

 area, containing up 

to 7.5 g/t gold (Grunsky and Smee, 1999). Low-grade porphyry 

copper prospects at Geunteut, Dusun, Sigalagala, Danu Diatas, and Siuluk Deras (fig. E1) are associated with arc-parallel 

faults that are part of the Sumatran Fault system and Miocene to 

Pliocene diorite to granodiorite stocks emplaced within segments and jogs of the Fault system (Barber and others, 2005). 

A number of areas surrounding or adjacent to the porphyry 

prospects contain numerous prospects and anomalies of copper, 

gold, and base metals in soil and sediment samples, such as at 

the Takengon prospect in the Aceh Province, North Sumatra. 

The Takengon prospect includes and surrounds the epithermal 

gold Collins prospect. Exploration at Collins identified two 

11-m drill intercepts with 22 and 15 g/t gold, respectively (East 

Asia Minerals Corporation, 2010). At Takengon, two areas of 

Tertiary porphyry-style copper mineralization and an area of 

Au-Cu skarn mineralization lie adjacent to the gold-bearing 

vein swarm and stockwork at the Collins prospect. Supergeneenriched copper porphyry mineralization adjacent to the 

epithermal gold Collins prospect contains 2.58 percent copper 

and elevated gold (East Asia Minerals Corporation, 2010). Geophysical studies suggest that the epithermal vein and stockwork 

systems at the Collins prospect coalesce below the surface in a 

larger porphyry-style system (East Asia Minerals Corporation, 

2010). Some placer-gold occurrences also are present in streams 

draining to the west coast.

Exploration History

Minerals exploration has taken place throughout Sumatra 

Island at a prospect and district scale along with geochemical sampling of soils and sediments on a regional scale. The 

Dutch undertook systematic mineral exploration and development between the 1840s and 1930s (Van Bemmelen, 1949) that 

ceased during and after World War II and Indonesian independence. Revision of Indonesian mining and finance laws under 

President Suharto in 1967 initiated new mineral-exploration 

activity from the late 1960s to present. Porphyry-associated 

mineral occurrences at Danu Diatas, Siuluk Deras, and Danau 

Dipatiempat were discovered during mineral exploration during 

the 1960s to 1990s, and the Tangse deposit and other prospects, 

such as Dusun, were identified through regional geologic mapping and geochemical sampling during this period (van Leeuwen, 1994). Geochemical and geophysical surveys also were 

done, but this information was not available during this assessment. The individual porphyry copper prospects have received 

prospect-level geochemical and geological exploration and rock 

chip sampling. Drilling has taken place on the Tangse deposit, 

the Dusun prospects, the Takengon (Collins) prospect, and probably on the Mundik prospect (Barber and others, 2005; Dalimunthe and others, 1997a,b). Companies that have been active on 

these prospects are Rikit Atlas Minerals, Newcrest Mining, and 

East Asia Minerals Corporation.
98 Porphyry Copper Assessment of Southeast Asia and Melanesia

Table E3. Identified porphyry copper resources in tract 142pCu7020, Sumatra Island—Indonesia.

[Ma, million years; Mt, million metric tons; t, metric ton; %, percent; g/t, gram per metric ton; NA, not applicable. Contained Cu in metric tons is computed as 

tonnage (Mt × 1,000,000) × Cu grade (percent); n.d., no data] 

Name Latitude Longitude Subtype Age 

(Ma)

Tonnage 

(Mt)

Cu 

(%)

Mo 

(%)

Au 

(g/t)

Ag 

(g/t)

Contained 

Cu (t) Reference

Tangse 5.033 95.95 NA 11 600 0.15 0.02 n.d. n.d. 900,000 Djaswadi (1993), Taylor and van Leeuwan 

(1980), van Leeuwen (1994); van Leeuwen 

and others (1987) 

Table E4. Significant prospects and occurrences in tract 142pCu7020, Sumatra Island—Indonesia.

[g/t, grams per metric ton; Ma, million years; n.d., no data]

 Name Latitude Longitude Age (Ma) Comments Reference

Mudik –1.7 101.25 Miocene Prospect, 7.5 g/t Au in pyritic boulders. Grunsky and Smee (1999)

Takengon

(Collins

prospect)

4.834 96.594 Tertiary Cu-porphyry mineralization, Au-Cu skarn, 

and epithermal Au vein stockworks with 

supergene enrichment at Collins prospect 

area at Takengon.

East Asia Minerals Corporation (2010)

Geunteut 5.012 95.603 14 Cu-Mo-Au in granodiorite stock. Bennett and others (1981); Coulson and 

others (1988)

Dusun 4.213 97.209 n.d. Stockwork in diorite-tonalite porphyry. Cameron and others (1983); Miswar and 

Coulson (1987); Dalimunthe and others 

(1997a, b); Bryant and Carlile (1980)

Sigalagala 3.396 97.894 9–11 Cu-Mo stockwork in diorite porphyry. Cameron and others (1982); Johnson and 

others (1987)

Danu Diatas –1.089 100.704 Pliocene Cu-Mo in propylitized rhyolite overlying 

granite porphyry.

Barber and others (2005)

Siuluk Deras –1.952 101.206 Pliocene Cu-Mo in propylitized diorite. Barber and others (2005)

Danau 

Dipatiempat

–2.847 101.934 Miocene to 

Pliocene

Low-grade Cu in argillized diorite in 

Tertiary volcanic rocks.

van Leeuwen (1978)

Tanjung Sakti –4.474 103.126 Mid-Miocene Low-grade Cu in brecciated and 

propylitized diorite stock.

Acquino (1988)

Sources of Information

Principal sources of information used by the assessment 

team for delineation of 142pCu7020 are listed in table E5.

Grade and Tonnage Model Selection

Tangse, the only deposit with identified resources 

within the tract, is a porphyry copper-molybdenum deposit 

with no reported gold grade. Analysis of variance tests 

on ore tonnage and grade data (table 6) showed that the 

Tangse porphyry copper deposit is consistent with the 

deposit populations in the general porphyry copper model 

for the world (Singer and others, 2008). This model 

was deemed the most appropriate model for estimation 

of undiscovered resources in the Sumatra Island tract, 

consistent with the reasoning and recommendations of 

Drew and Singer (2005).
Appendix E—Tract 142pCu7020 99

Table E5. Principal sources of information used for tract 142pCu7020, Sumatra Island—Indonesia.

[NA, not applicable]

 Theme Name or title Scale Citation

Geology Digital geologic map of Indonesia 1:1,000,000 Directorate of Mineral Resources and Inventory (2004a)

Systematic geologic map, Indonesia 1:250,000 Geological Research and Development Centre (1987–2000)

Mineral

occurrences

Porphyry copper deposits of the world: data 

base, map, and grade and tonnage models

NA Singer and others (2008)

Digital mineral occurrence data base NA Directorate of Mineral Resources and Inventory (2004b)

Mineral occurrence reports NA Djaswadi (1993), Miscellaneous company reports

Estimate of the Number of Undiscovered Deposits

Rationale for the Estimate

The team reviewed the results of a preliminary 

assessment done in February 2005; preliminary estimates 

were revised in 2010 (table E6) utilizing larger-scale 

geologic map information and incorporating the results of 

more recent exploration activity and geologic research in 

the area. The method of estimation was subjective and based 

on expert opinion and on analogy with geologically similar 

well-explored areas the team was familiar with in other 

regions of Southeast Asia and the world.

Takengon is one of the prospects judged to be likely to 

contain ore grades and tonnages consistent with the general 

porphyry copper deposit model, and it provides the rationale 

for the estimate of 1 deposit at 90-percent confidence.

Considerations that influenced estimates at 50- and 

10-percent confidence levels include the presence of the 

Tangse porphyry copper deposit and the number of additional 

porphyry-copper systems, prospects and occurrences along 

a well- defined magmatic arc. Strike-slip faulting within 

the tract provides evidence for a favorable structural setting 

for porphyry copper emplacement. In addition, several 

epithermal gold (low-sulfidation) and base-metal vein 

deposits also are present and could indicate the presence of 

buried porphyry systems, especially in the areas of gold, 

copper, and base-metal anomalies or occurrences that cluster, 

sometimes in the vicinity of known porphyry prospects. 

Another consideration was the presence of voluminous 

Eocene to Miocene intrusive and volcanic rocks in the tract 

that might host porphyry copper deposits in areas where 

uplift and erosion has been less intense and extensive, and 

extensive areas of Quaternary volcanic rocks that may cover 

unexposed porphyry copper deposits that lie at depths of less 

than 1 km. The estimate results in a mean of 7.1 expected 

undiscovered porphyry copper deposits in Sumatra Island 

within the tract and, when combined with the known Tangse 

deposit gives a density of five deposits/100,000 km2

. The 

team did not apply the deposit density models of Singer 

and others (2005) directly during the assessment, however 

our estimate of 5 deposits/100,000 km2 is consistent with, 

but at the lower end of, their reported observed range in 

deposit density in thoroughly explored porphyry copper 

tracts worldwide. This low prospectivity for porphyry copper 

deposits in the Sumatra tract, as assigned by the assessment 

team, reflects the recognition that no large porphyry systems 

are known in the continental-arc segment of the SundaBanda Arc and that the oblique nature of subduction and 

lack of plate reorganization during the late Tertiary in this 

area may decrease the likelihood of porphyry copper deposit 

development as compared to other prospective arcs in the 

region.

Probabilistic Assessment Simulation 

Results

Undiscovered resources for the Sumatra permissive 

tract 142pCu7020 were estimated by combining consensus 

estimates for numbers of undiscovered porphyry copper 

deposits (table E6) with the general grade and tonnage 

model of Singer and others (2008) using the EMINERS 

program (Root and others, 1992; Bawiec and Spanski, 

2012; Duval, 2012). Selected output parameters are 

reported in table E7. Results of the Monte Carlo simulation 

are presented as a cumulative frequency plot (fig. E4).The 

cumulative frequency plot shows the estimated resource 

volumes associated with cumulative probabilities of 

occurrence, as well as the mean for each commodity and for 

total mineralized rock.
100 Porphyry Copper Assessment of Southeast Asia and Melanesia

References Cited

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Center, Bandung, scale 1:250,000.

Cameron, N.R., Bennett, J.D., Bridge, D. McC., Djunuddin, 

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geology of the Tapaktuan Quadrangle (0519), Sumatra: 

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Table E7. Results of Monte Carlo simulations of undiscovered resources for tract 142pCu7020—Indonesia.

[Cu, copper; Mo, molybdenum; Au, gold; and Ag, silver; in metric tons; Rock, in million metric tons]

Material

Probability of at least the indicated amount Probability of

 0.95 0.9 0.5 0.1 0.05 Mean Mean or 

greater

None

Cu 0 490,000 13,000,000 56,000,000 90,000,000 23,000,000 0.32 0.07

Mo 0 0 230,000 1,600,000 2,600,000 640,000 0.27 0.14

Au 0 0 300 1,500 2,200 600 0.32 0.13

Ag 0 0 2,500 20,000 32,000 7,800 0.26 0.19

Rock 0 120 2,800 12,000 18,000 4,800 0.34 0.07

Table E6. Undiscovered deposit estimates, deposit numbers, tract area, and deposit density for tract 142pCu7020, Sumatra Island—

Indonesia.

[NXX, estimated number of deposits associated with the xxth percentile; Nund, expected number of undiscovered deposits; s, standard deviation; Cv%, coefficient 

of variance; Nknown, number of known deposits in the tract that are included in the grade and tonnage model; Ntotal, total of expected number of deposits plus 

known deposits; km2, area of permissive tract in square kilometers; Ntotal/100k km2, deposit density reported as the total number of deposits per 100,000 km2. 

Nund, s, and Cv% are calculated using a regression equation (Singer and Menzie, 2005)]

 Consensus undiscovered deposit estimates Summary statistics Tract area 

(km2

)

Deposit density 

(Ntotal/100k km2

)

N90 N50 N10 N05 N01 Nund s Cv% Nknown Ntotal

1 5 13 13 13 6.1 4.3 71 1 7.1 131,030 5
Appendix E—Tract 142pCu7020 101

Committee for Coastal and Offshore Geoscience Programmes 

in East and Southeast Asia (CCOP) and Geological Survey 

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Asia: Geological Survey of Japan, Digital Geoscience Map 

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Hariwidjaja, and Somantri, 1988, Further geochemical 

and geophysical investigations of granitic intrusions and 

associated skarns north of Geunteut, Aceh Province, 

Northern Suma-tra: Directorate of Mineral Resources, 

Bandung, Indonesia, NSGMEP Report Series No. 23.

Cox, D.P., 1986, Descriptive model of porphyry Cu, in Cox, 

D.P., and Singer, D.A., eds., Mineral deposit models: U.S. 

Geological Survey Bulletin 1693, p. 77.

Dalimunthe, P., Norris, R.G., Heryawan, B., 1997a, Summary 

of exploration activities, Upper Ise-Ise prospect, 1989–

1996: Unpublished report, PT Rio Tinto, Indonesia.

Dalimunthe, P., Norris, R.G., Hendrawan, D., and Heryawan, 

B., 1997b, Summary of exploration activities, Upper and 

Lower Tengekereng prospects, 1989–1996: Unpublished 

report, PT Rio Tinto, Indonesia.

Directorate of Mineral Resources and Inventory, 2004a, 

Digital geologic map: Jakarta, Indonesia, Indonesian 

Ministry of Energy and Mineral Resources, scale 

1:1,000,000. [Proprietary data.]

Directorate of Mineral Resources and Inventory, 2004b, 

Digital mineral occurrence database: Jakarta, Indonesia, 

Indonesian Ministry of Energy and Mineral Resources. 

[Proprietary data.]

Djaswadi, S., 1993 Prospective of base metal minerals in 

Indonesia: Bandung, Ministry of Mines and Energy of 

Republic of Indonesia, Directorate of Mineral Resources 

Special Publication, 229 p.

Drew, L.J., and Singer, D.A., 2005, Identifying the appropriate 

porphyry-copper deposit grade-tonnage model for a 

large-scale mineral resource assessment in South East 

Asia, in Chen, Qiuming, and Bonham-Carter, Graeme, 

eds., Proceedings of IAMG—The annual conference of 

the International Association for Mathematical Geology: 

Toronto, Canada, York University, Geomatics Research 

Laboratory, p. 1034–1039.

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Mineral Resource Simulator: U.S. Geological Survey Open 

File Report 2004–1344, accessed July 5, 2012, at http://

pubs.usgs.gov/of/2004/1344.

East Asia Minerals Corporation, 2010, Takengon, North 

Sumatra: accessed February 10, 2010, at http://www.

eaminerals.com/s/Takengon.aspHU.

Garwin, S., Hall, R., and Watanabe, Y., 2005, Tectonic setting, 

geology, and gold and copper mineralization in Cenozoic 

magmatic arcs of southeast Asia and the west Pacific, in

Hedenquist, T.W., Thompson, J.F.H., Goldfarb, R.J., and 

Richards, J.P., eds., One hundredth anniversary volume 

1905–2005: Littleton, Colorado, Society of Economic 

Geologists, p. 891–930.

Geological Research and Development Centre, 1987–2000, 

Systematic geologic map, Indonesia, map nos. 0420, 0421, 

0519, 0520, 0521, 0617, 0618, 0619, 0620, 0714, 0715, 

0716, 0717, 0718, 0719, 0812, 0813, 0814, 0815, 0816, 

0817, 0818, 0911, 0912, 0913, 0914, 0915, 0916, 0917, 

1010, 1011, 1012, 1013, 1014, 1015, 1016, 1110, 1111, 

1112, 1113: Bandung, Geological Survey of Indonesia, scale 

1:250,000.

Grunsky, E.C., and Smee, B.W., 1999, The differentiation of 

soil types and mineralization from multi-element geochemistry using multivariate methods and digital topography: 

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Sumatra fault: Geology, v. 12, p. 668–672.

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R.J., Dilles, J.H., Gray, Floyd, Graybeal, F.T., Mars, J.C., 

McPhee, D.K., Seal, R.R., Taylor, R.D., and Vikre, P.G., 

2010, Porphyry copper deposit model, chap. B of Mineral 

deposit models for resource assessment: U.S. Geological 

Survey Scientific Investigations Report 2010–5070–B, 169 

p., accessed September 8, 2010, at http://pubs.usgs.gov/

sir/2010/5070/b/.

Johnson, C.C., Coulson, F.I.E., and Sumartono, 1987, Mineral 

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Sumatra: Bandung, Indonesia, Directorate of Mineral 

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Miswar, Johnson, C.C., and Coulson, F.I.E., 1987, Further 

mineral investigations at the Dusun Intrusive Complex, 

Aceh Province, N Sumatra: Bandung, Indonesia, Directorate 

of Mineral Resources, NSGMEP Report Series no. 16.

Root, D.H., Menzie, W.D., and Scott, W.A., 1992, Computer 

Monte Carlo simulation in quantitative resource estimation: 

Natural Resources Research, v. 1, no. 2, p. 125–138.

Singer, D.A., and Menzie, W.D., 2005, Statistical guides to 

estimating the number of undiscovered mineral deposits—

An example with porphyry copper deposits, in Cheng, 

Qiuming, and Bonham-Carter, Graeme, eds., Proceedings 

of IAMG—The annual conference of the International 

Association for Mathematical Geology: Toronto, Canada, 

York University, Geomatics Research Laboratory, 

p. 1028–1033.
102 Porphyry Copper Assessment of Southeast Asia and Melanesia

Singer, D.A., Berger, V.I., Menzie, W.D., and Berger, B.R., 

2005, Porphyry copper density: Economic Geology, v. 100, 

no. 3, p. 491–514.

Singer, D.A., Berger, V.I., and Moring, B.C., 2008, Porphyry 

copper deposits of the world—Database and grade and 

tonnage models, 2008: U.S. Geological Survey Open-File 

Report 2008–1155, accessed June 1, 2011, at http://pubs.

usgs.gov/of/2008/1155/.

Taylor, D., and van Leeuwen, T., 1980, Porphyry type deposits 

in Southeast Asia: Mining Geology Special Issue, v. 8, 

p. 95–116.

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polygons, beta edition 1, in Boundaries and sovereignty 

encyclopedia (B.A.S.E.): U.S. Department of State, Office 

of the Geographer and Global Issues.

Van Bemmelen, R.W., 1949, The geology of Indonesia: The 

Hague, Govt. Printing Office, 2 volumes.

van Leeuwen, T.M., 1978, Final report general survey and 

exploration Sumatera Blocks 7, 8 and 9: PT Rio Tinto Indonesia, Report no. 245.

van Leeuwen, T.M., 1994, 25 years of mineral exploration and 

discovery in Indonesia: Journal of Geochemical Exploration, v. 50, p. 13–90.

van Leeuwen, T.M., Taylor, R.P., and Hutagalung, J., 1987, The 

geology of the Tangse porphyry copper-molybdenum prospect, Aceh, Indonesia: Economic Geology, v. 82, p. 27–42.
95° E 100° E 105° E

5° N

0°

5° S

!

!

!

Medan

Mudik

Dusun

Tangse

Geunteut

Sigalagala

Danu Diatas

Siuluk

Deras

Tanjung Sakti

Danau Dipatiempat

Takengon (Collins prospect)

Singapore

INDONESIA

MALAYSIA

SINGAPORE

90°E 

20°N

0°

20°S

Political boundary source: U.S. Department of State (2009)Projection: Asia South Albers Equal Area Conic;Central meridian 100° E; latitude of origin 15° S

E

0 100 200 300 400 KILOMETERS0 100 200 MILES

OtheAss142pPorp

Porpdeptrac

INDIAN OCEAN

Andaman Sea

South China Sea

Malacca Strait

Java Sea

INDIA

M

IN

Area of Map

Figure E1. Map showing tract location, known deposits, and significant porphyry copper prospects for tract 142pCu7020, Sumatra Island—Indon

China; IN, India; ID, Indonesia; MM, Myanmar; MY, Malaysia; TH, Thailand.
(

( ( 

( ( ( ( ( ( ( (

(

( ( ( ( (

(

( ( ( ( ( ( ( (

(

(

( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( 

(

(

(

(

( 

( ( ( ( ( ( ( 

( ( ( ( ( (

!

!

!

!

!

SUNDA TRENCH INDONESIA

MALAYSIA

MALAYSIA

INDONESIA

Java

JAVA TRENCH

Bali

Sumbawa

INDONESIA

Sumatra

SUMATRAN FAULT

Mudik

Dusun

Tangse

Geunteut

Sigalagala

Danu Diatas

Siuluk Deras

Tanjung Sakti

Takengon (Collins prospect)

Danau Dipatiempat

Medan

Bandung

Surabaja

Semarang

Singapore

INDIAN OCEAN

Sunda Strait

SOUTH CHINA SEA

Java Sea

100° E 110° E

0°

10° S

Base from ESRI ArcGIS Online (2009)World Shaded ReliefPolitical boundary source: U.S. Department of State (2009)Projection: Asia South Albers Equal Area Conic;Central meridian 108° E; latitude of origin 15° S

0 100 200 300 400 KILOMETERS0 100 200 MILES

E

As 1PoPoPePeEu

( (

(

SuSpStrTh

Figure E2. Map showing the regional setting for tract 142pCu7020, Sumatra Island—Indonesia.
( ( ( (

(

( ( ( (

(

( (

(

( ( ( ( ( ( (

(

(

(

( ( ( ( ( (

( (

( ( ( ( ( ( ( ( ( ( ( ( 

!

!

!

Mudik

Dusun

Tangse

Geunteut

Sigalagala

Danu Diatas

Siuluk Deras

Tanjung Sakti

Danau Dipatiempat

Takengon (Collins prospect)

SUNDA TRENCH

Sumatra

SUMATRAN FAULT

Medan

Singapore

INDONESIA

MALAYSIA

INDIAN OCEAN

Malacca Strait

South China Sea

Java Sea

95° E 100° E 105° E

5° N

0°

5° S

Base from ESRI ArcGIS Online (2009)World Shaded ReliefPolitical boundary source: U.S. Department of State (2009)Projection: Asia South Albers Equal Area Conic;Central meridian 100° E; latitude of origin 15° S

0 100 200 300 400 KILOMETERS0 100 200 MILES

E

As 1PoPoPePeEu

( ( Su

Str

Figure E3. Map showing the distribution of permissive igneous rocks, tectonic features, and porphyry copper deposits and prospects for tra

Island—Indonesia.
106 Porphyry Copper Assessment of Southeast Asia and Melanesia

0.01 0.1 1 10 100 1k 10k 100k 1M 10M 100M 1B 10B 100B

Material, in metric tons

1.00

0.90

0.80

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

Probability

Mean Cu

Mean Mo

Mean Au

Mean Ag

Mean Rock

Cu

Mo

Au

Ag

Rock

Mean Cu

Mean Mo

Mean Au

Mean Ag

Mean Rock

EXPLANATION

Figure E4. Cumulative frequency plot showing the results of Monte Carlo computer simulation of undiscovered 

resources in tract 142pCu7020, Sumatra Island—Indonesia. k, thousands; M, millions; B, billions; Tr, trillions.
Appendix F—Tract 142pCu7025 107

Appendix F. Porphyry Copper Assessment for Tract 142pCu7025, 

Sunda-Banda Arc—Indonesia

By Gilpin R. Robinson1, Jr., Jane M. Hammarstrom1, Steve Ludington2, Arthur A. Bookstrom3, Sewit A. Yenie1, 

Bambang Tjahjono Setiabudi4

, Dwi Nugroho Sunuhadi3 and Michael L. Zientek3, with contributions from 

Gwaibo Kopi5

Deposit Type Assessed: Porphyry copper, Cu-Au subtype

Descriptive model: Porphyry copper (Berger and others, 2008; John and others, 2010); Porphyry copper-gold 

(Cox, 1986; Cooke and others, 1998)

Grade and tonnage model: Porphyry copper, Cu-Au subtype (Singer and others, 2008)

Table F1 summarizes selected assessment results.

Table F1. Summary of selected resource assessment results for tract 142pCu7025, Sunda-Banda Arc—Indonesia.

[km, kilometers; km2, square kilometers; t, metric tons; NA, not applicable; n.d., no data]

Date of assessment Assessment 

depth (km)

Sub-tract Tract area 

(km2)

Known copper 

resources (t)

Mean estimate of 

undiscovered 

copper resources (t)

Median estimate of 

undiscovered copper 

resources (t)

February 2010 1 a 61,200 n.d. 10,000,000 4,200,000

b 22,550 7,216,000 15,000,000 8,000,000

c 5,670 n.d. 2,100,000 0

Total 89,420 7,216,000 27,00,000 NA

1

U.S. Geological Survey, Reston, Virginia, United States.

2

U.S. Geological Survey, Menlo Park, California, United States.

3

U.S. Geological Survey, Spokane, Washington, United States.

4

Directorate of Mineral Resources Inventory, Geological Agency of Indonesia, Bandung, Indonesia.

5

Geological Survey of Papua New Guinea.

Location

The tract includes southern Java (Jawa) extending eastward to Wetar Island, incorporating several other Greater Sunda 

Islands (fig. F1).

Geologic Feature Assessed

The eastern part of the Eocene to Holocene Sunda-Banda magmatic arc from Java (Jawa) to east of Wetar Island.
108 Porphyry Copper Assessment of Southeast Asia and Melanesia

Delineation of the Permissive Tract

Tectonic Setting

The Sunda-Banda Arc tract is the eastern part of the 

3,800-km-long Eocene to Holocene Sunda-Banda magmatic arc 

that stretches from Sumatra to east of Damar Island (fig. 5C). 

Porphyry copper mineralization in the tract, most of which is 

Miocene to Pliocene age, is generally associated with bodies of 

andesite porphyry, dacite porphyry, breccia, and tonalite porphyry (table F2). The largest known porphyry copper deposit, 

Batu Hijau, is 3.7 Ma (Garwin and others, 2005).

The long, elongated tract delineates a mid-Tertiary magmatic arc developed in response to frontal subduction of the 

Indian Ocean Plate along the Java Trench in the west and Timor 

Trough to the east (fig. F2). The tract has been subdivided into 

3 sub-tracts (fig. F3) based on differences in basement type, 

tectonics, and subduction history. The western part of the tract 

comprising Java (Jawa), sub-tract a, is a magmatic arc constructed on continental crust of the Eurasian Plate. Sub-tract b, 

east of Java (Jawa) extending from Bali to west Flores Islands, 

is an island arc constructed on oceanic crust (Carlile and Mitchell, 1994) and the magmatism in this area shows the smallest 

amount of geochemical influence from thinned continental 

crust or subducted continental-crust-derived sediments along 

the Sunda-Banda Arc trend (Elburg and others, 2004). Sub-tract 

c, extending from east Flores to Wetar Islands, is an island arc 

constructed on oceanic crust or highly thinned continental crust 

(Carlile and Mitchell, 1994). Magmatism in this area is geochemically influenced by Australian continental-crust materials 

(thinned continental crust or subducted continental-crust sediments; Elburg and others, 2004). In the late Miocene to Pliocene, collision of the Australian continent with the Sunda-Banda 

Arc shut off subduction along the Timor Trough and initiated 

a polarity shift to southward subduction of oceanic crust of the 

marginal Banda Sea beneath the arc in the sub-tract c area (Garwin and others, 2005).

Geologic Criteria

The entire tract includes Eocene to Pliocene intrusive- and 

volcanic-rock units but excludes thick overlying Quaternary 

volcanic and sedimentary units. The geologic units that define 

the permissive tract are calc-alkaline igneous rocks of Eocene to 

Pliocene age (most are mid-Miocene). Igneous-rock map units 

of uncertain age, that span this age range but may be as old as 

Cretaceous, have been included in the tract. Most of the plutonic 

rocks that crop out within the tract are small bodies of dioritegranodiorite (some porphyritic) and a few granite-granodiorite 

bodies (table F2). The chemistry of these rocks is calc-alkaline, 

but some sodic variants known as adakites are present (Elburg 

and others, 2004; Barber and others, 2005).

Calc-alkaline volcanic rocks are considered permissive 

for porphyry copper deposits because they are localized near, 

and often overlie, the intrusive centers where porphyry copper deposits often occur. These volcanic-rock map units may 

include small unmapped intrusive bodies within their borders. 

The volcanic rocks that define the tract include andesite flows 

and tuffs, dacite and associated dacitic tuffs and breccias, and 

basalt flows (table F2). Mid-Tertiary bimodal rhyolite-basalt 

sequences and andesitic tuffs that are primarily within marine 

carbonate rocks (fringing reefs bordering the oceanic islands) 

or clastic sedimentary rocks have been excluded from the tract. 

These distal volcanic deposits in carbonates and sediments are 

interpreted to be part of the accretionary-wedge complex, and 

their sites of deposition were not likely to be near the intrusive centers that host porphyry copper deposits. A few high-K 

alkaline series volcanic rocks occur in a back-arc setting (Barber 

and others, 2005).

The team used 1:250,000-scale geologic maps (table F2) 

to identify areas of permissive rock types, based on the map 

legend attribute information describing map-unit rock types, 

composition, and age. The distribution of the permissive rock 

units is shown in figure F3. The maps were scanned and rectified, and the areas of permissive rock units were digitized by 

hand to build an attributed digital GIS file used to define the 

permissive tract. After choosing the polygons and groups of 

polygons that represent the surface expressions of permissive 

igneous intrusions, we applied a 10-km buffer around them to 

account for a spatial uncertainty of approximately 2 km in the 

digitized geology and deposit location data and the possibility that deposits may be associated with intrusions that expand 

beneath their surface expression and also are less than 1 km 

beneath the land surface. A 2-km buffer was applied around the 

permissive volcanic units, as these may be imprecisely located 

and partly covered. The locations of (1) major and minor copper deposits, prospects, and occurrences and (2) hydrothermal 

gold-copper deposits and prospects listed in the Indonesian 

mineral-occurrence database (Directorate of Mineral Resources 

and Inventory, 2004a,b) correlated with the buffer polygons. In 

some areas, the buffer polygons were extended and modified 

to include the deposits and prospects in this database that were 

located outside of, but near, the buffer polygons. A polygon 

aggregation and smoothing process was applied to the revised 

buffered permissive geologic map units to produce a preliminary permissive tract. The processing approximates manual 

delineation of a tract but is rapid and reproducible. The processing steps include (1) unioning all permissive unit buffers and 

other polygon features that comprise the framework of the tract, 

(2) aggregating unioned polygons using an aggregation distance 

of 50 km and a minimum hole size of 2,000 km2

, (3) simplifying the aggregated polygons using a bend-simplify algorithm 

with a simplification tolerance of 5 km, and (4) line-smoothing 

the simplified polygons using an algorithm (PAEK, polynomial 

approximation with exponential kernel) with a tolerance of 20 

km. Necking, thinning and contraction of the polygons resulting 

from the above processing necessitated manual cleaning of the 

preliminary tract (for example, polygon necks removed). Final 

tracts were compared to the permissive geologic features in 

source maps to ensure that original permissive boundaries were 

honored. All operations were carried out in ArcGIS 9.3 using 

standard tools available in the Arc Toolbox.
Appendix F—Tract 142pCu7025 109

Table F2. Map units that define tract 142pCu7025, Sunda-Banda Arc—Indonesia.

[Geologic map, map unit, geologic-age range, and principal rock types from 1:250,000 scale geologic maps, compiled by the Geological Research and Development Centre, Badung, Indonesia, 1987–2000]

 Map unit Map symbol Lithology Age range

Intrusive rocks

142pCu7025a, Java 

1 (Western Jawa) Tmi Granite, granodiorite Late early Miocene

1 (Western Jawa) Tlmi Porphyritic diorite, porphyritic andesite Early Miocene

1 (Western Jawa) Tomi Granodiorite Late Oligocene to early Miocene

2 (Middle Jawa) Tpib Diorite Pliocene

2 (Middle Jawa) Tmik Plagioclase porphyry, basalt Late Miocene

2 (Middle Jawa) Tpi Intrusive rocks and andesite-basalt volcanic plug Pliocene

2 (Middle Jawa) Tmi Diorite Middle to late Miocene

3 (Eastern Jawa) Tmi Andesite Early to middle Miocene

142pCu7025b. Bali to west Flores Islands 

1807 Tmi Dacite, basalt Middle Miocene

2007 Tdi Diorite Lower to middle Miocene

2007 Tsy Syenite Lower to middle Miocene

2007 Tt Tonalite-trachyte Lower to middle Miocene

2007 Tda Dacite Lower to middle Miocene

2107 Tmg Granodiorite Late Miocene

2107 Tmd Quartz diorite Late Miocene

2109-2108-2208 Tdi Diorite Middle Miocene

2109-2108-2208 Tgr Granite, monzonite Eocene to Oligocene

2207 Tmg Granite, granodiorite Middle Miocene

142pCu7025c, east Flores to Wetar Islands

2207 Tmg Granite, granodiorite Middle Miocene

2307 Tpdi Quartz diorite Pliocene

2307 Tmgd Granodiorite Upper Miocene

2508 Tmdi Diorite Middle Miocene

2508 Tmgd Granodiorite Middle Miocene

2508 Tmgr Granite Middle Miocene

2508 Tmda Dacite Middle Miocene

Volcanic rocks

142pCu7025a, Java 

1 (Western Jawa) Tmib Andesite Early to late Miocene

1 (Western Jawa) Tnv Andesite and basalt breccia and lava Pliocene
110 Porphyry Copper Assessment of Southeast Asia and Melanesia

1 (Western Jawa) Tpvs Tuff Pliocene

1 (Western Jawa) Tpi Andesite Pliocene

1 (Western Jawa) Tmvs Volcanic breccia, tuff Late Miocene

1 (Western Jawa) Tlvs Volcanic breccia, tuff Early Miocene

1 (Western Jawa) Tomv Andesite Late Oligocene to early Miocene

1 (Western Jawa) Temv Volcanic breccia, tuff Late Eocene to early Miocene

2 (Middle Jawa) Tnvb Andesitic to basaltic volcanic breccia, lava flow 

and tuff

Late Miocene

2 (Middle Jawa) Tpv Volcanic breccia, tuff Pliocene

2 (Middle Jawa) Tnv Andesite and basalt breccia and lava Middle Miocene to Pliocene

2 (Middle Jawa) Tmv Andesite and basalt lava and breccia Early to middle Miocene

2 (Middle Jawa) Tomv Andesite, basalt, and dacite Late Oligocene to early Miocene

3 (Eastern Jawa) Tlmv Dacite, andseite, basalt Early to middle Miocene

3 (Eastern Jawa) Tomv Andesite and basalt lava, breccia, and tuff Late Oligocene to early Miocene

3 (Eastern Jawa) Tomw Basalt Late Oligocene to early Miocene

3 (Eastern Jawa) Tmv Andesite, basalt and dacite Middle Miocene

142pCu7025b, Bali to west Flores Islands 

1707 Tpvp Andesite-basalt lava and breccia Pliocene

1707 Tpva Lava Pliocene

1707 Tomu Volcanic breccia and lava Oligocene to early Miocene

1807 Tomp Volcanic breccia and lava Oligocene to early Miocene

1807-1907 Tmv Andesitic volcanic breccia Early to middle Miocene

1807-1907 Tmi (a,b,d,u) Andesite, basalt Middle to late Miocene

2007 Tmv Dacite, porphyritic dacite Lower to middle Miocene

2007 Tlmv Andesite, basalt Lower Miocene

2007 Ta Andesite Middle-lower Miocene

2107 Tmt Volcanic lava and breccia Middle to late Miocene

2109-2108-2208 Tomk Andesite and basalt volcanic breccia and lava Early Miocene

2109-2108-2208 Tan Andesite Middle Miocene

2207 Tmt Dacitic lava Middle Miocene

2207 Tmk Volcanic breccia Early Miocene

Table F2. Map units that define tract 142pCu7025, Sunda-Banda Arc—Indonesia.—Continued

[Geologic map, map unit, geologic-age range, and principal rock types from 1:250,000 scale geologic maps, compiled by the Geological Research and 

Development Centre, Badung, Indonesia, 1987–2000]

 Map unit Map symbol Lithology Age range

Volcanic rocks
Appendix F—Tract 142pCu7025 111

142pCu7025c, east Flores to Wetar Islands

2207 Tmt Dacitic lava Middle Miocene

2207 Tmk Volcanic breccia Early Miocene

2307 Tmpa Volcanic lava and breccia Upper Miocene

2508 Tmpa Andesite and basalt lava 

 and breccia

 Late Miocene to Pliocene

2508 Tmn Dacite lavas Late Miocene to Pliocene

2508 Tmt Andesite and basalt breccia Early Miocene

2711, 2509, 2709, 2508, 

2608, 2708, 2507, 2607, 

2707

 Tv Andesite, basalt Pliocene

Table F2. Map units that define tract 142pCu7025, Sunda-Banda Arc—Indonesia.—Continued

[Geologic map, map unit, geologic-age range, and principal rock types from 1:250,000 scale geologic maps, compiled by the Geological Research and Development Centre, Badung, Indonesia, 1987–2000]

Map unit Map symbol Lithology Age range

Volcanic rocks

These revised preliminary-tract polygons were further 

modified by comparison with the scanned and rectified geologic maps to exclude areas where Quaternary volcanic rocks 

and sedimentary deposits are greater than 1 km in thickness. 

The final tract boundary was clipped to the shoreline to eliminate undersea areas (U.S. Department of State, 2009).

The Sunda-Banda Arc tract includes the southern part 

of Java (Jawa), areas within and between the islands of Bali, 

and Sumbawa (Nusa Tenggara Barat), Flores (Nusa Tenggara 

Timur), and Maluku. The Sunda-Banda Arc tract includes at 

least 10 national parks and a number of nature reserves.

Known Deposits

The Batu Hijau porphyry copper-gold deposit (1.64 

billion metric tons at 0.44 percent copper, 0.35 g/t gold) on 

Sumbawa Island (fig. F3), the only porphyry deposit in the 

overall Sunda-Banda Arc tract (table F3) with identified 

resources (Singer and others, 2008), is located in sub-tract b. 

The deposit and other prospects in the region were discovered 

in early 1990 as a result of a reconnaissance stream-sediment 

sampling program (carried out by Newmont) and the subsequent discovery of malachite-stained float and outcrop. The 

copper-gold mineralization is hosted by a tonalite intrusive 

complex with diorite and metavolcanic wallrocks. The orebody is cylindrical, with a vertical extent of more than 650 

m. Potassic core-zone alteration grading outward to extensive 

propylitic alteration hosts most of the ore mineralization (van 

Leeuwen, 1994). Sulfide and ore minerals are bornite, chalcopyrite, molybdenite, pyrite, sphalerite, galena, and electrum. 

Supergene ore minerals include chalcocite/digenite, covellite, 

cuprite, and malachite (Garwin, 2002). At the beginning of the 

21st century, Batu Hijau was the tenth largest copper mine in 

the world, accounting for approximately 2.5 percent of global 

production; mine production at Batu Hijau from September 

2009 to September 2010 was 190,509 metric tons of copper 

and 15,705 kilograms of gold (Steel Guru, 2010).

Prospects, Mineral Occurrences, and Related 

Deposit Types

There are numerous additional prospects and anomalies 

of gold and copper within the Sunda-Banda Arc tract (table 

F4). The western part of the Sunda-Banda Arc tract contains 

the gold and gold-copper districts of Cikotok, Gunung Pongkor, Cikondang, Koelon Progo, and Jampang in West Java 

(Jawa) Island, including the Porgera and Tjibadong epithermal 

gold deposits. East Java (Jawa) contains the Pagergunung, 

Gunung Kumitir and Gunung Tumpanqpitu, Trenggalek, 

Muara Mandilis, Baban Timur, and Baban Timur porphyry 

prospects. There are also new discoveries of porphyry-style 

mineralization at the Gunung Tumpanqpitu, Gunung Kumitir, 

and Pagergunung prospects and in East Java (Jawa).

Sub-tract a: The Miocene andesite volcanic rocks along 

the southern coast of Java host several porphyry occurrences 

associated with diorite intrusions and stocks, including the 

Ciemas, Tujuh-Bukit (Tumpangpita), and Tirtomoyo prospects 

(fig. F3). The Dutch explored near the Ciemas prospect in 
112 Porphyry Copper Assessment of Southeast Asia and Melanesia

Table F3. Identified porphyry copper resources in tract 142pCu7025, Sunda-Banda Arc—Indonesia.

[Ma, million years; Mt, million metric tons; t, metric ton; %, percent; g/t, gram per metric ton; Cu-Au subtype, deposits that have Au/Mo ratios >30 or average 

Au grades >0.2 g/t; n.d., no data. Contained Cu in metric tons is computed as tonnage (Mt × 1,000,000) × Cu grade (percent)]

Name Latitude Longitude Subtype Age (Ma) Tonnage 

(Mt) Cu (%) Mo (%) Au (g/t) Ag (g/t) Contained 

Cu (t) Reference

Batu Hijau -8.96 116.87 Cu-Au 3.7 1,640 0.44 n.d. 0.35 n.d. 7,216,000 Garwin (2002), Clode 

and others (1999), 

Imai and Ohno (2005), 

Maula and 

Levet (1996)

1922–24, and local mining for gold began in the 1980s (van 

Leeuwen, 1994). The gold-ore vein stockwork at Ciemas is in 

a Miocene dacite porphyry intruded into early Miocene andesitic volcanic rocks that display argillization and silicification 

(van Leeuwen, 1994). Drilling at the Tujuh-Bukit porphyry 

copper-gold prospect (Tumpangpita area) yielded an inferred 

resource of 500 Mt at 0.4 percent copper and 0.5 g/t gold at 

a cutoff grade of 0.2 percent copper (Intrepid Mines Limited, 

2010). Resources at Tujuh-Bukit are open in all directions. The 

Tirtomoyo prospect is a diorite porphyry copper-gold stockwork associated with base-metal skarn in Miocene volcanic 

rocks. The Dutch report evidence of mining of the base-metal 

skarn by the Japanese during World War II (van Leeuwen, 

1994). High-sulfidation alteration and epithermal mineralization is reported to overprint the porphyry copper-gold mineralization event (Arc Exploration Limited, 2010).

Sub-tract b: Sub-tract b contains the Batu Hijau porphyry deposit and a number of porphyry copper-gold 

prospects with recent exploration activity (table F4). The 

Dodo-Elang porphyry copper-gold prospect occurs in small 

bodies of diorite and feldspar porphyry associated with 

granodiorite intruded into andesitic volcanic rocks. Potassic, 

propylitic, phyllic, and advanced argillic alteration styles are 

widespread and intense. Widespread copper-gold mineralization in the alteration zones generally is low grade but is 

highest (>0.5 percent copper and 0.5 g/t gold) in the potassic 

alteration zones (van Leeuwen, 1994). Rock geochemistry 

of surface and drill-core samples indicates a northeastsouthwest elongate copper zone more than 1.5 km long by 

0.8 km wide trending into the adjacent East Elang prospect 

area. Inferred resources at Dodo-Elang are estimated to be 

greater than 1 billion tons at undisclosed grades (Southern 

Arc Minerals, Inc., 2010c) At the Selodong prospect, coppergold mineralization occurs in phyllic- and propylitic- altered 

dacite porphyry stocks that have intruded andesitic and rhyodacitic volcanic rocks. Trenching has reported ore grades 

of 0.20 percent copper and 0.88 g/t gold, and rock samples 

have returned grades up to 0.4 percent copper, 0.4 g/t gold, 

and 400 ppm molybdenum (Southern Arc Minerals, Inc., 

2010a). Drilling at 7 of 15 exploration targets in a 7 by 3 km 

area provides an inferred resource of 225 million tons at 0.24 

percent copper and 0.33 g/t gold.

Sub-tract c: No porphyry copper prospects are known in 

the Sub-tract c area. The Weta epithermal gold deposit lies in 

Sub-tract c in the eastern part of the Sunda-Banda Arc tract.

Exploration History

Detailed exploration in West and East Java (Jawa) has 

taken place according to Directorate of Mineral Resources 

(Aneka Tambang) and is also documented in the private company reports residing in that agency. This exploration activity 

has generated a series of grouped gold and copper anomalies, 

many of which have led to discoveries of porphyry goldcopper prospects. Geophysical exploration in the region has 

been described by Turner (1993). The Batu Hijau deposit was 

discovered in 1990 from studies investigating gold and copper 

anomalies identified as a result of a stream-sediment sampling 

program in Sumbawa done by Newmont in the late 1980s. The 

history of prospect geochemical exploration at Batu Hijau is 

described by Meldrum and others (1994).

Sources of Information

Principal sources of information used by the assessment 

team for delineation of 142pCu7025 are listed in table F5.

Grade and Tonnage Model Selection

The choice of the porphyry copper-gold subtype model 

of Singer and others (2008) to assess for porphyry copper 

deposits in the Sunda-Banda Arc sub-tract a area was based on 

the grade characteristics of the Ciemas prospect, the gold-rich 

nature of the related epithermal systems in the tract area, and 

geologic characteristics of the Sunda-Banda magmatic arc.
Appendix F—Tract 142pCu7025 113

Table F4. Significant prospects and occurrences in tract 142pCu7025, Sunda-Banda Arc—Indonesia.

[Ma, million years; n.d., no data; %, percent; g/t, grams per metric ton; km, kilometers, m, meters. Rank 4=prospect in global database of Singer and others 

(2008) or >16,000 t contained copper; Rank 3=drilled, with >20 m of 0.2% or more Cu. Rank 2=drilled or trenched with <20 m of 0.2% Cu or <0.2% Cu, or 

past or ongoing exploration. Rank 1=copper occurrence that may be related to porphyry-type mineralization based on stream sediment or magnetic anomaly or 

location along structural trend]

 Name Latitude Longitude Age 

(Ma) Comments Reference Rank

142pCu7025a, Java Island

Ciemas −7.22 106.56 3.1 1.5 by 0.75 km Au-Cu-Mo anomaly. 10 drill holes show 

~0.2% Cu and ~0.2 g/t Au.

McInnes and others 

(2004)

2

Tirtomoyo −7.93 111.088 n.d. Reported assays of ore materials range from 1.08 to 

9.6% Cu, 0.1 to 15.0 g/t Au, 27 to 96 g/t Ag. Southern 

Arc noted the presence of high sulfidation veining 

overprinting earlier porphyry Cu-Au mineralizing events. 

Southern Arc Minerals Inc. 

(2010b)

2

Tujuh-Bukit −8.583 114.017 n.d. Intrepid Mines in 2010 reports drill intercepts of 118m 

at 0.37g/t Au and 0.36% Cu, and 455 m at 0.39g/t Au, 

0.34% Cu and 72 ppm Mo. Inferred resources of 500 

million tons at 0.4% Cu and 0.5 g/t Au at 0.2% Cu cutoff 

grade.

Intrepid Mines Limited 

(2010) 

4

Trenggalek −8.266 111.812 n.d. Outcropping epithermal gold-silver veins targeted for 

drilling in 2010; hydrothermal breccia, silica caps.

 Arc Exploration Limited 

(2010)

2

Pekalongan −7.423 109.861 n.d. Assays of mineralized diorite and andesite report up to 

0.46 g/t Au and 0.47% Cu. Stream-sediment geochemical 

survey completed but with generally low Au and Cu 

results.

Austindo Resources 

Corporation NL (2010)

1

142pCu7025b, Bali to west Flores Islands

Selodong −8.857 116.023 n.d. Drill core assays report 0.16–0.28% Cu and 0.28–0.56 g/t 

Au. 7 by 3 km target area yields inferred resources of 225 

million tons at 0.24% Cu and 0.33 g/t Au.

Southern Arc Minerals, 

Inc. (2010a)

3

Dodo-Elang −8.872 117.318 n.d. Rock geochemistry of surface and drill core samples 

indicate a NE-SW elongate copper zone more than 1.5 

km long by 0.8 km wide trending into the adjacent East 

Elang prospect. Inferred resources of 1 billion tons at 

undisclosed grades. 

van Leeuwen (1994), 

Southern Arc Minerals, Inc. 

(2010c)

2

Sabarati −8.567 117.569 n.d. Prospect Arc Exploration Limited 

(2010)

1

Hulu −8.762 118.458 n.d. Prospect Arc Exploration Limited 

(2010)

1

Bima −8.624 119 n.d. The geological and geochemical results from Kowo 

suggest the possibility of a buried porphyry copper-gold 

target; additional soil sampling planned. 

Arc Exploration Limited 

(2009, 2010)

1
114 Porphyry Copper Assessment of Southeast Asia and Melanesia

Table F5. Principal sources of information used for tract 142pCu7025, Sunda-Banda Arc—Indonesia.

[NA, not applicable]

 Theme Name or title Scale Citation

Geology Digital geologic map of Indonesia 1:1,000,000 Directorate of Mineral Resources and Inventory (2004a)

Systematic geologic map, Indonesia 1:250,000 Geological Research and Development Centre (1987–2000)

Mineral 

occurrences

Porphyry copper deposits of the world: 

database, map, and grade and tonnage 

models

NA Singer and others (2008)

Digital mineral occurrence data base NA Directorate of Mineral Resources and Inventory (2004b)

Exploration Exxploration overview Indonesia NA van Leeuwen (1994), Setiabudhi (2004, 2010 written 

commun.)

Commercial databases NA Infomine, Intierra, MEG

Company Web sites NA Austindo Resources Corporation NL (2010), Southern Arc 

Minerals, Inc. (2010), Arc Exploration Limited (2010), 

Intrepid Mines Limited (2010)

The Batu Hijau deposit in sub-tract b is classified as a 

porphyry copper-gold deposit by Singer and others (2008). 

The porphyry copper-gold subtype model is used for subtract b based on the characteristics of the Batu Hijau deposit, 

the gold-rich nature of the related epithermal systems in the 

tract area, and geologic characteristics of the magmatic arc in 

this area. The arc magmatism in sub-tract b is developed on 

oceanic crust in a subduction setting lacking influence from 

continental crust or sediments derived from continental crust 

(Elburg and others, 2004), and the copper-gold subtype model 

is judged to be appropriate for this area.

No deposits or prospects are known in sub-tract c. The 

choice of the porphyry copper-gold subtype model of Singer 

and others (2008) to assess for porphyry copper deposits in 

the Sunda-Banda Arc sub-tract c area was based the gold-rich 

nature of epithermal systems in the tract area and geologic 

characteristics of the Sunda-Banda magmatic arc (table 6).

Rationale for the Estimate

The results of a preliminary assessment done in February 2005 were revised by utilizing larger-scale geologic map 

information and incorporating the results of more recent 

exploration activity and geologic research in the area. The 

assessment team reestimated the number of porphyry copper 

and copper-gold deposits in the Sunda-Banda Arc sub-tracts at 

the 90, 50, and 10 probability confidence levels during February 2010. The method of estimation was subjective and based 

on expert opinion and on analogy with geologically similar 

thoroughly explored areas in other regions of Southeast Asia 

and the world with which the team was familiar.

Sub-tract a: The assessment team recognized that no 

large porphyry-style systems are known in the continental-arc 

portion of the Sunda-Banda arc underlying Java (Jawa) (De 

Waele and others, 2009; Garwin and others, 2005). Undiscovered porphyry copper deposits are most likely to occur 

in Miocene andesite volcanic rocks and associated intrusive 

centers located along the southern coast of Java (Jawa) that 

host a number of porphyry copper-gold occurrences associated 

with diorite intrusions and stocks. This area has been explored, 

but the team concluded that future exploration around the 

Tujuh-Bukit and possibly the Ciemas and other prospects, may 

identify one or more deposits at 90-percent confidence and 

two or more deposits at 50-percent confidence, but more than 

eight undiscovered deposits were unlikely in the sub-tract.

Sub-tract b: Sub-tract b, a part of the Sunda-Banda Arc 

developed on oceanic crust, is highly prospective for porphyry 

copper deposits, hosting the large Batu Hijau porphyry coppergold deposit and a number of porphyry copper-gold prospects 

under current exploration that have not been fully evaluated. 

Of these prospects, Selodong and Dodo-Elang are most likely 

to have grade and tonnage characteristics consistent with the 

porphyry copper-gold model. Ongoing exploration is likely 

to identify additional prospects, particularly in the vicinity 

of epithermal gold prospects. The team estimated that one or 

more porphyry copper-gold deposits are likely at 90-percent 
Appendix F—Tract 142pCu7025 115

confidence and that four or more deposits are likely at 50-percent confidence, but more than 10 undiscovered deposits are 

unlikely in the sub-tract.

Sub-tract c: No porphyry copper prospects are known 

in the sub-tract c area, however, the epithermal gold deposit 

at Wetar may be the surface manifestation of underlying 

porphyry-style mineralization at unknown depth. The panel 

estimated a 10-percent chance that two porphyry copper-gold 

deposits may be present in the sub-tract. The panel concluded 

that there is a 10-percent chance that a subsurface porphyry 

copper system may be present within 1 km of the land surface 

at Wetar and that another potential deposit may lie under 

young volcanic cover. The tract area likely to host porphyrystyle mineralization in sub-tract c is small (<6,000 km2

), the 

arc magmatism is young (mostly Pliocene to Holocene), and 

the estimated occurrence of undiscovered porphyry deposits at 

depths shallower than 1 km is likely to be low.

Tract Summary: The combined assessment results for 

sub-tracts a, b, and c result in a mean estimate of 9.8 expected 

undiscovered deposits in the overall tract. Considerations 

taken into account during the overall tract estimation process 

were the gold-rich nature of the porphyry-style prospects and 

that at least 20 gold and gold-copper anomalies or mineralized 

centers are known throughout the Sunda-Banda Arc tract and 

include a number of copper-gold epithermal veins and porphyry copper-gold prospects. A major additional consideration 

was the presence of extensive sedimentary and volcanic cover 

rocks and their ability to hide concealed deposits. In addition, 

copper and gold occurrences and anomalies cluster throughout 

most of the Sunda-Banda Arc tract (Directorate of Mineral 

Resources and Inventory, 2004a; table F4).

The mean estimate of 9.8 undiscovered deposits for 

all three sub-tracts, when added to Batu Hijau, result in a 

density of 10.9 deposits/100,000 km2, consistent with the 

observed range in deposit density in thoroughly explored 

porphyry copper tracts worldwide as reported by Singer and 

others (2005).

Probabilistic Assessment Simulation 

Results

Undiscovered resources for the Sunda-Banda Arc tract 

142pCu7025 were estimated by combining consensus estimates 

for numbers of undiscovered porphyry copper deposits (table 

F6) with the porphyry copper-gold subtype grade and tonnage model of Singer and others (2008) using the EMINERS 

program (Root and others, 1992; Bawiec and Spanski, 2012; 

Duval, 2012). Selected output parameters are reported in table 

F7. Results of the Monte Carlo simulations are presented 

as cumulative frequency plots (fig. F4A–C).The cumulative 

frequency plots for each sub-tract show the estimated resource 

volumes associated with cumulative probabilities of occurrence, as well as the mean, for each commodity and for total 

mineralized rock.

Table F6. Undiscovered deposit estimates, deposit numbers, tract area, and deposit density for tract 142pCu7025, Sunda-Banda Arc—

Indonesia.

[NXX, Estimated number of deposits associated with the xxth percentile; Nund, expected number of undiscovered deposits; s, standard deviation, Cv%, coefficient 

of variance; Nknown, number of known deposits in the tract that are included in the grade and tonnage model; Ntotal, total of expected number of deposits plus 

known deposits; km2, area of permissive tract in square kilometers; Ntotal/100k km2, deposit density reported as the total number of deposits per 100,000 km2. 

Nund, s, and Cv% are calculated using a regression equation (Singer and Menzie, 2005). NA, not applicable]

 Consensus undiscovered deposit estimates Summary statistics Tract area 

(km2

)

Deposit 

density 

(Ntotal/100k 

km2

) N90 N50 N10 N05 N01 Nund s Cv% Nknown Ntotal

142pCu7025a, Java Island

1 2 8 8 8 3.4 2.7 80 0 3.4 61,200 6

142pCu7025b, Bali to west Flores Islands

1 4 10 10 10 4.8 3.3 68 1 5.8 22,550 26

142pCu7025c, east Flores to Wetar Islands

0 0 2 2 3 0.63 1 160 0 0.63 5,670 11

Total 9.8 NA NA 1 10.8 89,420 12
116 Porphyry Copper Assessment of Southeast Asia and Melanesia

Table F7. Results of Monte Carlo simulations of undiscovered resources for tract 142pCu7025, Sunda-Banda Arc—Indonesia.

[Cu, copper; Mo, molybdenum; Au, gold; and Ag, silver; in metric tons; Rock, in million metric tons; NA, not applicable. Quantiles are not additive; means are 

additive]

Material

 Probability of at least the indicated amount Probability of

0.95 0.9 0.5 0.1 0.05 Mean Mean or greater None

Sub-tract a, Java Island

Cu 0 170,000 4,200,000 28,000,000 44,000,000 10,000,000 0.28 0.07

Mo 0 0 6,900 160,000 340,000 59,000 0.21 0.37

Au 0 18 350 2,100 3,100 770 0.31 0.07

Ag 0 0 700 7,600 17,000 3,500 0.2 0.28

Rock 0 40 900 5,800 9,300 2,100 0.3 0.07

Sub-tract b, Bali to west Nusa Tenggara Islands

Cu 0 410,000 8,000,000 41,000,000 59,000,000 15,000,000 0.31 0.07

Mo 0 0 19,000 270,000 470,000 91,000 0.24 0.27

Au 0 40 650 2,800 3,800 1,100 0.34 0.07

Ag 0 0 1,500 12,000 25,000 5,000 0.22 0.2

Rock 0 93 1,700 8,500 11,000 3,100 0.33 0.07

Sub-tract c, east Nusa Tenggara to Wetar Islands

Cu 0 0 0 4,700,000 9,800,000 2,100,000 0.18 0.59

Mo 0 0 0 15,000 50,000 12,000 0.11 0.8

Au 0 0 0 360 760 150 0.2 0.59

Ag 0 0 0 1,100 2,600 690 0.13 0.75

Rock 0 0 0 940 2,200 420 0.19 0.59

Summary of undiscovered resources for combined sub-tracts a, b, and c

Cu NA NA NA NA NA 27,00,000 NA NA

Mo NA NA NA NA NA 160,000 NA NA

Au NA NA NA NA NA 2,000 NA NA

Ag NA NA NA NA NA 9,200 NA NA

Rock NA NA NA NA NA 5,600 NA NA
Appendix F—Tract 142pCu7025 117

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1998, Australian and western Pacific porphyry Cu-Au 

deposits: Journal of Australian Geology and Geophysics, 

v. 17, no. 4, p. 97–104.

Cox, D.P., 1986, Descriptive model of porphyry Cu-Au 

(Model 20c), in Cox, D.P., and Singer, D.A., eds., 1986, 

Mineral deposit models: U.S. Geological Survey Bulletin 

1693, p. 110. (Also available at http://pubs.usgs.gov/bul/

b1693/.)

De Waele, B., Williams, P., and Chan, G., 2009, Tectonic controls on the distribution of large copper and gold deposits 

in Southeast Asia to identify productive and non-productive 

structures: Proceedings of the Tenth Biennial SGA meeting, 

August 17-19, 2009, Townsville, Australia, p. 933–935.

Directorate of Mineral Resources and Inventory, 2004a, Digital geologic map: Jakarta, Indonesia, Indonesian Ministry of 

Energy and Mineral Resources, scale 1:1,000,000. [Proprietary data.]

Directorate of Mineral Resources and Inventory, 2004b, 

Digital mineral occurrence database: Jakarta, Indonesia, 

Indonesian Ministry of Energy and Mineral Resources. 

[Proprietary data.]

Duval, J.S., 2012, Version 3.0 of EMINERS—Economic Mineral Resource Simulator: U.S. Geological Survey Open File 

Report 2004–1344, accessed July 5, 2012, at http://pubs.

usgs.gov/of/2004/1344. 

Elburg, M.A., van Bergen, M.J., and Foden, J.D., 2004, 

Subducted upper and lower continental crust contributes to 

magmatism in the collision sector of the Sunda-Banda arc, 

Indonesia: Geology, v. 32, no. 1, p. 41–44.

Garwin, S., 2002, Ore geology setting of intrusion-related 

hydrothermal systems near Batu Hijau porphyry coppergold deposit, Sumbawa, Indonesia, in Goldfarb, R.J., and 

Nielsen, R.L., eds., Integrated method for discovery—

Global exploration in the twenty-first century: Society of 

Economic Geologists Special Publication 9, p. 333–366.

Garwin, S., Hall, R., and Watanabe, Y., 2005, Tectonic setting, 

geology, and gold and copper mineralization in Cenozoic 

magmatic arcs of southeast Asia and the west Pacific, in

Hedenquist, T.W., Thompson, J.F.H., Goldfarb, R.J., and 

Richards, J.P., eds., One hundredth anniversary volume 

1905–2005: Littleton, Colorado, Society of Economic 

Geologists, p. 891–930.

Geological Research and Development Centre, 1987–2000, 

Systematic geologic map, Indonesia, map nos. 1108, 1109, 

1110, 1208, 1209, 1210, 1308, 1309, 1407, 1408, 1409, 

1507, 1508, 1509, 1607, 1608, 1609, 1707, 1708, 1707, 

1807, 1907, 2007, 2107, 2207, 2307, 2407, 2408, 2508: 

Bandung, Geological Survey of Indonesia, scale 1:250,000.

Imai, A., and Ohno, S., 2005, Primary ore mineral assemblage 

and fluid inclusion study of the Batu Hijau porphyry Cu-Au 

deposit, Sumbawa Indonesia: Resource Geology, v. 55, 

no. 3, p. 239–248.

Intrepid Mines Limited, 2010, Tujuh Bukit Project, East Java: 

accessed February 10, 2010, at http://www.intrepidmines.

com/index.php?option=com_contentandview=articleandid=

84andItemid=124.
118 Porphyry Copper Assessment of Southeast Asia and Melanesia

John, D.A., Ayuso, R.A., Barton, M.D., Blakely, R.J., 

Bodnar, R.J., Dilles, J.H., Gray, Floyd, Graybeal, F.T., 

Mars, J.C., McPhee, D.K., Seal, R.R., Taylor, R.D., and 

Vikre, P.G., 2010, Porphyry copper deposit model, chap. 

B of Mineral deposit models for resource assessment: 

U.S. Geological Survey Scientific Investigations Report 

2010–5070–B, 169 p., accessed September 8, 2010, at 

http://pubs.usgs.gov/sir/2010/5070/b/.

Kamitani, M., and Naito, K., eds., 1998, Mineral resource 

map of Asia: Metal Mining Agency of Japan, scale 

1:35,000,000, accessed February 10, 2010, at www.mmaj.

go.jp/mric_web/deposit/index.htm.

Maula, S., and Levet, B., 1996, Porphyry copper gold 

signatures and the discovery of the Batu Hijau deposit, 

Sumbawa, Indonesia, in Porphyry related copper and 

gold deposits of the Asia Pacific region: Conference 

Proceedings, Australian Mineral Foundation, Glenside, 

South Australia, p. 8.1–8.13.

McInnes, B.I.A., Evans, N.J., Sukarna, D., Permanadewi, 

S., Garwin, S., Belousova, E., Griffin, W.L., and Fu, 

F., 2004, Thermal histories of Indonesian porphyry 

copper-gold deposits determined by U-Th-He, U-Pb, 

Re-Os, K-Ar and Ar-Ar methods, in Predictive mineral 

discovery under cover: Perth, Western Australia, 

Society of Economic Geologists 2004 session abstracts, 

CDROM, p. 343–346.

Meldrum, S.J., Aquino, R.S., Gozales, R.I., Burke, R.J., 

Suyadi, Artha, Irianto, Bombang, and Clarke, D.S., 1994, 

The Batu Hijau porphyry copper-gold deposit, Sumbawa 

Island, Indonesia: Journal of Geochemical Exploration, v. 

50, p. 203–220.

Root, D.H., Menzie, W.D., and Scott, W.A., 1992, Computer 

Monte Carlo simulation in quantitative resource 

estimation: Natural Resources Research, v. 1, no. 2, 

p. 125–138.

Singer, D.A., and Menzie, W.D., 2005, Statistical guides to 

estimating the number of undiscovered mineral deposits—

An example with porphyry copper deposits, in Cheng, 

Qiuming, and Bonham-Carter, Graeme, eds., Proceedings 

of IAMG—The annual conference of the International 

Association for Mathematical Geology: Toronto, Canada, 

York University, Geomatics Research Laboratory, p. 

1028–1033.

Singer, D.A., Berger, V.I., Menzie, W.D., and Berger, B.R., 

2005, Porphyry copper density: Economic Geology, v. 

100, no. 3, p. 491–514.

Singer, D.A., Berger, V.I., and Moring, B.C., 2008, 

Porphyry copper deposits of the world—Database and 

grade and tonnage models, 2008: U.S. Geological Survey 

Open-File Report 2008–1155, accessed June 1, 2011, at 

http://pubs.usgs.gov/of/2008/1155/.

Southern Arc Minerals, Inc., 2010a, Selodong, West Lombok 

project, Central Java: accessed February 10, 2010, at http://

www.southernarcminerals.com/projects/lombok/west_

lombok/project_activities/selodong_intrusive_complex/.

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project, Central Java: accessed February 10, 2010, at http://

www.southernarcminerals.com/projects/java/wonogiri/.

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Vale enter into option/joint venture agreement: accessed 

December 20, 2010, at http://www.southernarcminerals.com/

news/news_releases/index.php?andcontent_id=240/.

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accessed December 20, 2010, at http://www.steelguru.com/

metals_news/Batu_Hijau_gold_and_copper_production_

up/173935.html.

Turner, S.J., 1993, A systematic exploration approach leading to 

two significant discoveries in Indonesia, in Romberger, S.B., 

and Fletcher, D.I., eds., Integrated methods in exploration 

and discovery—Conference program and extended abstracts: 

Littleton, Colorado, Society of Economic Geologists, p. 

AB121–AB123.

U.S. Department of State, 2009, Small-scale digital 

international land boundaries (SSIB)—Lines, edition 10, 

and polygons, beta edition 1, in Boundaries and sovereignty 

encyclopedia (B.A.S.E.): U.S. Department of State, Office 

of the Geographer and Global Issues.

van Leeuwen, T.M., 1994, 25 years of mineral exploration and 

discovery in Indonesia: Journal of Geochemical Exploration, 

v. 50, p. 13–90.
Figure F1. Map showing tract location, known deposits, and significant porphyry copper prospects for tract 142pCu7025, Sunda-Banda Arc—Ind

MY, Malaysia.

105° E 110° E 115° E 120° E 

5° S

10° S

! !

!

!

!

!

!

!

!

!

!

!

Bandung

Semarang

Yogyakarta

Tanjungkarang-Telukbetung

Jakarta

Kendari

Makassar

Surabaja

Mataram

Kupang

Batu Hijau

Bima

Ciemas Dodo-Elang

Hulu

Pekalongan

Sabarati

Selodong

Tirtomoyo

Trenggalek

Tujuh-Bukit

INDONESIA

INDONESIA

INDONESIA

INDON

TIMOR-LESTE

Java Sea 

 INDIAN OCEAN 

Flores Sea 142pCu7025a 142pCu7025b 142pCu7025c

MY

ID ID

MY

110°E 

0°

10°S20°S

Political boundary source: U.S. Department of State (2009)Projection: Asia South Albers Equal Area Conic;Central meridian 115° E; latitude of origin 15° S

EXPLANATION

Other porphyry copper tractsAssessed porphyry copper tract 142pCu7025Porphyry copper depositPorphyry copper prospect

0 100 200 300 400 KILOMETERS0 100 200 MILES

Area of 

Map
(

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!

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SUNDA TRENCH

SUMATRAN FAULT

Sumatra INDONESIA

MALAYSIA

MALAYSIA

Kalimantan

JAVA TRENCH

INDONESIA

TIMOR TROUGH

AUSTRALIA

VIETNAM

THAILAND

WEST

SULAWESI

KINABALU FAULT

PALU-KORO FAULT

Hulu

Bima

Ciemas

Selodong

Tirtomoyo

Trenggalek

Pekalongan

Dodo-Elang

Batu Hijau Tujuh-Bukit

Sabarati

Medan

Bandung Semarang

Surabaja

Singapore

Ho Chi Minh City

South China Sea

INDIAN OCEAN

Banda Sea

Celebes Sea

Java Sea

Sunda Strait

Makassar Strait

100° E 110° E 120° E 130° E

10° N

0°

10° S

Base from ESRI ArcGIS Online (2009)World Shaded ReliefPolitical boundary source: U.S. Department of State (2009)Projection: Asia South Albers Equal Area Conic;Central meridian 115° E; latitude of origin 15° S

0 200 400 600 800 KILOMETERS

0 200 400 MILES

A PoPoPePeA

( (

(

SuSpStTh

E

Figure F2. Map showing the regional setting for tract 142pCu7025, Sunda-Banda Arc—Indonesia.
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122 Porphyry Copper Assessment of Southeast Asia and Melanesia

Figure F3. Map showing the distribution of permissive igneous rocks, tectonic features, and porphyry copper deposits and 

prospects for tract 142pCu7025, Sunda-Banda Arc—Indonesia. 142pCu7025a, Java (Jawa) Island. 142pCu7025b, Bali to west 

Flores Islands. 142pCu7025c, east Flores to Wetar Islands.

( ( ( ( ( ( ( ( (

(

(

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( ( ( ( ( ( ( ( ( ( ( ( ( ( 

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!

!

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Bandung

Semarang

Yogyakarta

Tanjungkarang-Telukbetung

Jakarta

Surabaja

Ciemas

Pekalongan

Tirtomoyo

Trenggalek Tujuh-Bukit

INDONESIA

INDONESIA

JAVA TRENCH 

Bali

Java

INDIAN OCEAN

Java Sea

142pCu7025a

105° E 115° E 

5° S

10° S

Base from ESRI ArcGIS Online (2009)

World Shaded Relief

Political boundary source: U.S. Department of State (2009)

Projection: Asia South Albers Equal Area Conic;

Central meridian 115° E; latitude of origin 15° S

0 100 200 300 400 KILOMETERS

0 100 200 MILES
References Cited 123 ( 

( ( ( ( ( ( 

( ( ( ( ( ( ( ( ( (

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Kendari

Makassar

Dili

Mataram

Kupang

Batu Hijau

Bima

Dodo-Elang

Hulu

Sabarati

Selodong

INDONESIA

TIMOR-LESTE

INDONESIA

TIMOR-LESTE

TIMOR TROUGH

Wetar

Flores

Sumbawa

Timor Sea

Banda Sea

Flores Sea

142pCu7025b

142pCu7025c

125° E

EXPLANATION

Eurasian continental crust

Australian continental crust Porphyry copper deposit

Porphyry copper prospect

Permissive intrusive rock

Permissive volcanic rock

( (

(

Subduction zone

Spreading center

Strike-slip fault

Thrust fault

Assessed porphyry copper

 tract 142pCu7025
124 Porphyry Copper Assessment of Southeast Asia and Melanesia

1.00

0.90

0.80

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

Probability

0.01 0.1 1 10 100 1k 10k 100k 1M 10M 100M 1B 10B 100B

Material, in metric tons

Mean Rock Mean Cu

Mean Au

Mean Ag

Mean Mo

Cu

Mo

Au

Ag

Rock

Mean Cu

Mean Mo

Mean Au

Mean Ag

Mean Rock

EXPLANATION A

Figure F4. Cumulative frequency plots showing the results of Monte Carlo computer simulations of undiscovered 

resources in tract 142pCu7025, Sunda-Banda Arc-Indonesia. A,142pCu7025a, Java (Jawa) Island. B, 142pCu7025b, Bali 

to west Flores Islands. C, 142pCu7025c, east Flores to Wetar Islands. k, thousands; M, millions; B, billions; Tr, trillions.

1.00

0.90

0.80

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

Probability

0.01 0.1 1 10 100 1k 10k 100k 1M 10M 100M 1B 10B 100B

Material, in metric tons

Mean Cu

Mean Mo

Mean Au

Mean Ag

Mean Rock

Cu

Mo

Au

Ag

Rock

Mean Cu

Mean Mo

Mean Au

Mean Ag

Mean Rock

EXPLANATION B
Appendix F—Tract 142pCu7025 125

1.00

0.90

0.80

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

Probability

0.01 0.1 1 10 100 1k 10k 100k 1M 10M 100M 1B 10B 100B

Material, in metric tons

Mean Cu Mean Au

Mean Ag

Mean Rock

Mean Mo

Cu

Mo

Au

Ag

Rock

Mean Cu

Mean Mo

Mean Au

Mean Ag

Mean Rock

EXPLANATION C

Figure F4.—Continued
126 Porphyry Copper Assessment of Southeast Asia and Melanesia

1

U.S. Geological Survey, Reston, Virginia, United States.

2

Directorate of Mineral Resources Inventory, Geological Agency of Indonesia, Bandung, Indonesia.

3

U.S. Geological Survey, Menlo Park, California, United States.

4

U.S. Geological Survey, Spokane, Washington, United States.

5

Geologic Survey of Papua New Guinea.

Table G1. Summary of selected resource assessment results for tract 142pCu7026, West Sulawesi—Indonesia.

[km, kilometers; km2, square kilometers; t, metric tons; n.d., no data]

Date of 

assessment

Assessment depth 

(km)

Tract area 

(km2)

Known copper 

resources (t)

Mean estimate of 

undiscovered copper 

resources (t)

Median estimate of

undiscovered copper 

resources (t)

February 2010 1 60,270 n.d. 3,400,000 650,000

Appendix G. Porphyry Copper Assessment for Tract 142pCu7026, 

West Sulawesi—Indonesia

By Gilpin R. Robinson, Jr.1, Bambang Tjahjono Setiabudi2, Dwi Nugroho Sunuhadi2, Jane M. Hammarstrom1, 

Steve Ludington3

, Arthur A. Bookstrom4, Sewit A. Yenie1, and Michael L. Zientek4, with contributions from 

Gwaibo Kopi5

Deposit Type Assessed: Porphyry copper, copper-gold subtype

Descriptive model: Porphyry copper (Berger and others, 2008; John and others, 2010); Porphyry copper-gold 

(Cox, 1986; Cooke and others, 1998)

Grade and tonnage model: Porphyry copper, Cu-Au subtype (Singer and others, 2008)

Table G1 summarizes selected assessment results.

Location

The tract occupies most of the west half of the Island of Sulawesi in Indonesia (fig. G1).

Geologic Feature Assessed

Tract 142pCu7026 includes Miocene to Pliocene igneous rocks in the southern portion of the 1,200 km long SulawesiSangihe magmatic arc, located in southwestern Sulawesi.

Delineation of the Permissive Tract

Tectonic Setting

The West Sulawesi magmatic arc is part of the 1,200-km-long Sulawesi-Sangihe magmatic arc, which has been active since 

the Miocene. The regional geologic and tectonic setting of the West Sulawesi tract is shown in figure G2. The West Sulawesi Arc 
Appendix G—Tract 142pCu7026 127

is partly developed on continental crust containing pre-Tertiary 

polymetamorphic rocks and Cretaceous plutons, and it has a 

complex history including three overlapping volcanic-arc events 

(Taylor and van Leeuwen, 1980; Garwin and others, 2005):

1. Cretaceous to Paleocene subduction over a westdipping subduction zone resulted in the development 

of a north-northwest-trending calc-alkaline volcanic 

arc as West Sulawesi was accreted to the Sundaland 

continental-crust block bordering Kalimantan during a 

late Cretaceous orogenic event. Arc volcanism ceased 

in the Eocene as West Sulawesi rifted away from Kalimantan with the development of oceanic crust in the 

Makassar Straits (fig. G3).

2. A middle Miocene to early Pliocene volcanic arc developed over a west dipping subduction zone. Western 

Sulawesi formed an island arc east of its present position accompanied by andesitic volcanism and diorite to 

granodiorite intrusions.

3. Displacement of the arc system over the Makassar 

Straits and Celebes Sea occurred in response to collision of the Banggai-Sula continental fragment of 

the Australian Plate (fig. G3) with the Sulawesi Arc 

(Carlile and others, 1990). This collision and displacement resulted in Pliocene to Pleistocene uplift of the 

composite arc system. Rapid erosion associated with 

this uplift exposed many of the Cretaceous to Paleocene intrusions at depth levels greater than depths at 

which porphyry copper deposits are likely to occur.

Geologic Criteria

Based on local geologic history, including tectonics, uplift, 

and erosion, porphyry copper deposits in the tract are likely to 

be restricted to Miocene to Pliocene igneous rocks in this magmatic arc. Nearby porphyry copper deposits in the western part 

of the adjacent North Sulawesi-Sangihe tract, including Tombuliato and Tapadaa, are dated at 3 and 3.75 Ma, respectively (van 

Leeuwen, 1994). These deposits are thought to have formed in 

an island-arc setting above two opposed subduction zones, in 

contrast to the continental-arc setting of the West Sulawesi tract 

(van Leeuwen, 1994). The Malala low-fluorine molybdenum 

deposit located in the northern part of the West Sulawesi tract 

is associated with intrusions dated at about 4 Ma. Malala is 

interpreted to have formed in a postsubduction continental-arc 

setting following the collision of several continental microplates 

with Sulawesi (tectonic event 3, above; van Leeuwen and others, 1994).

The geologic units that define the permissive tract are 

calc-alkaline and potassic calc-alkaline to alkaline igneous 

rocks of Miocene to Pliocene age. Some igneous-rock map units 

of uncertain Tertiary age, that span this age range but may be 

as old as Eocene, have been included in the tract. Most of the 

plutonic rocks that crop out within the tract are numerous small 

bodies of diorite-granodiorite (some porphyritic) and a few 

granite-granodiorite bodies in the calc-alkaline rock series, and 

bodies of monzonite (map unit Tgr), monzodiorite, and syenite 

(monzodiorite and syenite not shown at map scale) and leucitebearing volcanic rocks (map unit Tma) in the potassic calcalkaline and alkaline rock series (table G2). The distribution of 

permissive intrusive and volcanic rocks is shown in figure G3.

Calc-alkaline volcanic rocks are considered permissive 

for porphyry copper deposits as they are localized near and 

often overlie intrusive centers that may host porphyry deposits and may include small unmapped intrusive bodies within 

their borders. The volcanic rocks that define the tract include 

andesite flows and tuffs, dacite and associated dacitic tuffs and 

breccias, and basalt flows (table G2). Mid-Tertiary basalt and 

basalt-dike complexes (oceanic crust), bimodal rhyolite-basalt 

sequences, and andesitic tuffs that are primarily within marine 

carbonate rocks (fringing reefs bordering the oceanic islands) or 

clastic sedimentary rocks have not been used to define the tract 

but are incorporated locally in the tract because of proximity 

to other permissive rock units. These basaltic dike complexes 

and the distal volcanic deposits in carbonates and sediments are 

interpreted to be part of the accretionary-wedge complex and 

their sites of deposition were not likely to be near the intrusive 

centers that host porphyry copper deposits. A K-calc-alkaline 

intrusive and volcanic province occurs in the northern part of 

the West Sulawesi tract, and a K-alkaline-shoshonitic volcanic 

province occurs in the southern part of the tract (Soeria-Atmadja 

and others, 1999), possibly in a back-arc tectonic setting (Taylor 

and van Leeuwen, 1980) or postsubduction magmatic-arc setting (Soeria-Atmadja and others, 1999).

Data used to construct the tract included 1:1,000,000-scale 

geology and local and regional mineral occurrence databases 

(Directorate of Mineral Resources and Inventory, 2004a,b) and 

1:250,000-scale published geologic maps (table G2) to identify 

areas of permissive rock types, based on the map legend attribute information describing map unit rock types, composition, 

and age. The 1:250,000-scale maps were scanned and rectified 

and the areas of permissive rock units were digitized by hand to 

supplement the partial digital geology coverage at 1:1,000,000-

scale provided by the Indonesian Directorate of Mineral 

Resources and Inventory (2004a). This enhanced GIS file was 

used to define the permissive tract. After choosing the polygons 

and groups of polygons that represent the surface expressions 

of permissive igneous intrusions, a 10-km buffer was applied 

to account for a spatial uncertainty of approximately 2 km in 

the digitized geology and deposit location data and the possibility that deposits may be associated with intrusions that expand 

beneath their surface expression and are also less than 1 kilometer beneath the land surface. A 2-km buffer was applied around 

the permissive volcanic units, as these may be imprecisely 

located and partly covered.

A polygon aggregation and smoothing process was 

applied to the revised buffered permissive geologic map units 

to produce a preliminary permissive tract. The processing 

approximates manual delineation of a tract but is rapid and 

reproducible. The processing steps include (1) unioning all 

permissive unit buffers and other polygon features that comprise 
128 Porphyry Copper Assessment of Southeast Asia and Melanesia

Table G2. Map units that define tract 142pCu7026, West Sulawesi—Indonesia.

[Map unit, geologic-age range, and principal rock types from 1:250,000 scale geologic maps, compiled by the Geological Research and Development Centre, Badung, Indonesia, 1987–2000]

Map unit Lithology Age range

Intrusive rocks

d, di Diorite Late Miocene

gd Granodiorite Early Miocene

gr Granite, granodiorite Miocene

Tdi Diorite Middle Miocene

Tgr Granite, monzonite Eocene to Oligocene

Tmpg Granite Pliocene

Tmpi Granite, granodiorite, diorite Middle Miocene to Pliocene

Tpkg Granite, granodiorite Pliocene

Volcanic rocks

t Trachyte or andesite Pliocene

Tan Andesite Middle to late Miocene

Tma Leucite-basaltic tuff Middle to late Miocene

Tmav Volcanic tuff Late-middle Miocene

Tmb Volcanic tuff Middle Miocene

Tmcv Volcanic breccia Pliocene to late Miocene

Tmkv Lava Middle Miocene

Tml Andesite Middle to late Miocene

Tmpv Basalt, andesite Pliocene to late Miocene

Tmrt Volcanic tuff Early to middle Miocene

Tmtv Andesite, basalt Middle Miocene to Pliocene

Tolv Andesite, basalt Oligocene

Tomk Andesite, basalt Early Miocene

Toml Andesitic-basaltic tuff Oligocene

Tpbc Eruptive center Pliocene

Tpbl Lava Pliocene

Tpbv Lava Pliocene

Tplv Andesite, basalt Eocene to Pliocene

Tppl Trachyte Pliocene

Tppv Trachyte, andesite Pliocene

the framework of the tract, (2) aggregating unioned polygons 

using an aggregation distance of 50 km and a minimum hole 

size of 2,000 km2, (3) simplifying the aggregated polygons 

using a bend-simplify algorithm with a simplification tolerance 

of 5 km, and (4) line-smoothing the simplified polygons using 

an algorithm (PAEK, polynomial approximation with exponential kernel)with a tolerance of 20 km. Necking, thinning, and 

contraction of the polygons resulting from processing required 

a subsequent manual cleaning step (for example, to remove 

polygon necks). Final tract boundaries were compared to the 

permissive geologic features in source materials to ensure that 

original permissive boundaries were honored. All operations 

were carried out in ArcGIS 9.3 using standard tools available in 

the Arc Toolbox.

These revised preliminary-tract polygons were further 

modified by comparison with the scanned and rectified geologic 

maps to exclude areas where Quaternary volcanic rocks or sedimentary deposits are greater than 1 km in thickness. As a last 

step, the tract boundary was clipped to the shoreline to eliminate 

undersea areas (U.S. Department of State, 2009).
Appendix G—Tract 142pCu7026 129

The West Sulawesi tract encompasses the western part of 

Sulawesi Island. The tract includes the southern Miocene to 

Pliocene portion of the 1,200-km-long North Sulawesi-Sangihe 

magmatic arc located in the southwestern part of Sulawesi, 

bounded by the coast of Sulawesi along the west and south 

boundary of the tract; the extent of Miocene to Pliocene volcanic and intrusive rocks define the eastern boundary, and the 

northern border of the West Sulawesi tract is delineated by a 

set of northwest-striking faults that follow a rotation hingeline 

extending from the intersection of the north Sulawesi Trench 

with regional Palu-Koro Fault Zone (fig. G3; Walpersdorf and 

others, 1998). Neogene plate motions, magma chemistry types, 

and the migration trend of volcanism differs across this rotation 

hingeline that delineates the West Sulawesi tract from the North 

Sulawesi tract (142pCu7027). Potassic calc-alkaline volcanism 

is restricted to the West Sulawesi tract (Walpersdorf and others, 

1998).

The West Sulawesi tract defines an area where the estimated number of undiscovered deposits was expected to be 

significantly different than in the adjacent North Sulawesi tract 

because of differences in the geology, plate-tectonic settings, 

extent and depth of cover, number of known prospects and 

deposits, and thoroughness of exploration. A number of gold 

and base-metal occurrences and prospects associated with 

Tertiary intrusive and volcanic rocks, including volcanogenic 

massive sulfide deposits, are located in the West Sulawesi tract 

(Djaswadi, 1993). A few national parks and nature reserves are 

located in the tract.

Known Deposits

No porphyry copper deposits are known to be present in 

the West Sulawesi tract, however the tract does contain the 

Malala porphyry molybdenum deposit (dated at 4.14 Ma) in 

the northern part of the tract. The Malala deposit is a low-fluorine molybdenum-rich porphyry system in quartz monzonite 

in a composite Miocene to Pliocene granite-quartz monzonitegranodiorite batholith (Soeria-Atmadja and others, 1999). 

The Malala deposit contains 100 Mt of ore resources at 0.14 

percent MoS2

. The molybdenum mineralization is associated 

with a late-stage quartz monzonite stock in the roof zone of a 

composite pluton emplaced during an arc-continent collision 

magmatic event in the late Miocene to Pliocene (Taylor and 

van Leeuwen, 1980).

Prospects, Mineral Occurrences, and Related 

Deposit Types

The Sassak prospect (table G3) lies in the central part of 

the tract associated with an intrusive complex of shoshonitic 

affinity (Soeria-Atmadja and others, 1999). Although gold 

grades are not reported for the prospect, Sassak was identified 

as a Cu-Au porphyry deposit by Soerai-Atmadja and others 

(1999) and Singer and others (2008). The porphyry-style mineralization at Sassak occurs in a series of small Miocene (10.6 

Ma) alkaline stocks, including monzodiorite, monzonite, and 

syenite, that are satellite intrusions near the southern margin of 

the Mamasa monzonite batholith (Soeria-Atmadja and others, 

1999). These stocks intruded early Miocene andesitic lavas 

and breccias. Porphyry-style mineralization probably occurred 

at about the time of emplacement of a series of northeasttrending intermediate and alkaline dikes. The prospect has 

little economic significance because of its small size and low 

grade (Taylor and van Leeuwen, 1980). Near Sassak, occurrences of gold-base metal vein and gold-bearing quartz veins 

are widespread along the northern margin of the Mamasa 

batholith (Soeria-Atmadja and others, 1999).

The medium-sized gold deposit at Awak, in the middle 

of the tract, occurs in quartz veins, breccias, and stockworks 

emplaced along a series of shallow-dipping shear zones in 

Cretaceous metamorphic rocks (fig. G3; Sillitoe, 1995). Additional base-metal and copper occurrences lie in the northern 

and southern parts of the tract.

Exploration History

There was regional- and prospect-scale exploration by 

the Dutch in the colonial period between the 1840s and 1930s 

and deposit-scale exploration around mines and occurrences 

that began in the 1960s and continued episodically through 

the 1990s (van Leeuwen, 1994). Exploration geochemistry 

and mapping in the late 1960s through 1970s was initiated in 

Sulawesi based on recognition of widespread Tertiary calcalkaline rocks in an island-arc or continental-arc setting, a 

few known copper occurrences, and the possibility that the 

porphyry copper districts in the Philippines might extend 

southward into Sulawesi. The Sassak porphyry prospect was 

discovered during the late 1960s during a reconnaissance 

geological survey of West Sulawesi by geologists of the Geological Survey of Indonesia. Stream-sediment sampling and 

trenching was used to delineate the prospect area followed by 

a detailed mapping and drilling program in the 1970s. Exploration activity in the region was mostly by RTZ, Kennecott, 

and Newmont joined by other junior exploration companies 

based in the Southeast Asia region, such as Tropic Endeavour 

Indonesia (TEI) (van Leeuwen, 1994).

Sources of Information

Principal sources of information used by the assessment 

team for delineation of 142pCu7026 are listed in table G4.

Grade and Tonnage Model Selection

The porphyry Cu-Au subtype model (Singer and others, 2008) was selected to assess the undiscovered resources 

associated with porphyry copper deposits in the West Sulawesi 

tract (table 6). The model selection for the tract is based on 

the geological, mineralogical, and geochemical features of 
130 Porphyry Copper Assessment of Southeast Asia and Melanesia

the Sassak prospect, which is considered a porphyry Cu-Au 

deposit type by Soeria-Atmadja and others (1999) and Singer 

and others (2008), the gold-rich nature of the related epithermal systems in the tract area, and the K-alkaline nature of the 

intrusive and volcanic rocks in the tract area.

Estimate of the Number of Undiscovered Deposits

Rationale for the Estimate

The numbers of undiscovered porphyry copper deposits in 

West Sulawesi tract were estimated at 90, 50, 10, and 5 probability percentiles in February 2010 on the basis of subjective 

estimation (table G5). The method of estimation was based on 

expert opinion and on analogy with geologically similar areas 

the in other regions of Southeast Asia and the world with which 

the team was familiar.

The estimate results in a mean of 1.1 expected undiscovered deposits yielding an estimated density of 1.8 porphyry 

copper deposits/100,000 km2

. Considerations that influenced 

the estimate were the presence of several centers of gold and 

copper occurrences throughout the tract, including the Awak 

gold deposit and gold-copper occurrences north of the Mamasa 

batholith. There was discussion about the significance of the 

Sassak prospect, with the conclusion that it is likely to be a porphyry copper-gold system, but is of little economic significance 

because of its small size. A small number of mineral occurrences in the tract are compatible with the porphyry coppergold models and rocks types, such as diorite, granodiorite, and 

monzonite. These calc-alkaline to alkaline intrusive rocks are 

considered potential host rocks for porphyry copper-gold deposits; however, significant porphyry copper prospects are lacking 

in the tract. Cessation of westward dipping subduction under the 

tract in the late Miocene followed by extensive uplift and erosion during the Pliocene to Pleistocene in the tract may limit the 

likelihood of undiscovered porphyry copper deposits. The tract 

may have some potential for porphyry copper-gold deposits 

formed in a postsubduction setting (Richards, 2009); postsubduction tectonics may have stimulated the generation of the 

Pliocene potassic calc-alkaline to alkaline igneous rocks in the 

tract (Soeria-Atmadja and others, 1999). A postsubduction tectonic setting is postulated for the Pliocene Malala molybdenum 

porphyry deposit located in the northern part of the tract (van 

Leeuwen and others, 1994). The uncertainty associated with the 

assessment results for this tract reflects the uncertain porphyry 

potential in the tract with subduction probably ending around or 

slightly before the Pliocene, rapid post-Pliocene uplift and erosion, large areas of intrusions lacking associated volcanic rocks 

in the northern half of the tract, and the potential that a portion 

of these intrusive rocks in the north are collision-related rather 

than subduction related. The team did not apply the deposit 

Table G3. Significant prospects and occurrences in tract 142pCu7026, West Sulawesi—Indonesia.

[Ma, million years; %, percent]

Name Latitude Longitude Age (Ma) Comments Reference

Sassak -3.158 119.48 10.6 Explored 1969–1976. 0.1 to 0.6% 

Cu reported. Prospect has little 

economic significance.

Djaswadi (1993), Taylor and 

van Leeuwan (1980)

Table G4. Principal sources of information used for tract 142pCu7026, West Sulawesi—Indonesia. 

[NA, not applicable]

Theme Name or title Scale Citation

Geology Digital geologic map of Indonesia 1:1,000,000 Directorate of Mineral Resources and 

 Inventory (2004a)

Systematic geologic map, Indonesia 1:250,000 Geological Research and Development 

 Centre (1987–2000)

Mineral

occurrences

Porphyry copper deposits of the world: 

database, map, and grade and tonnage 

models

NA Singer and others (2008)

Digital mineral occurrence database NA Directorate of Mineral Resources and 

 Inventory (2004b)
Appendix G—Tract 142pCu7026 131

density models of Singer and others (2005) directly during the 

assessment; however, the estimate of 1.8 deposits/100,000 km2 

is low compared to the observed deposit-density range reported 

by them. This is consistent with the assessment team’s evaluation that this relatively well-explored tract is not likely to be 

highly prospective for undiscovered porphyry copper-gold or 

porphyry copper deposits.

Probabilistic Assessment Simulation 

Results

Undiscovered resources for the West Sulawesi permissive tract 142pCu7026 were estimated by combining consensus estimates for numbers of undiscovered porphyry copper 

deposits (table G5) with the copper-gold subtype grade and 

tonnage model of Singer and others (2008) using the EMINERS 

program (Root and others, 1992; Bawiec and Spanski, 2012; 

Duval, 2012). Selected output parameters are reported in table 

G6. Results of the Monte Carlo simulation are presented as a 

cumulative frequency plot (fig. G4). The cumulative frequency 

plot shows the estimated resource volumes associated with 

cumulative probabilities of occurrence, as well as the mean, for 

each commodity and for total mineralized rock.

References Cited

Bawiec, W.J., and Spanski, G.T., 2012, Quick-start guide for 

version 3.0 of EMINERS—Economic Mineral Resource 

Simulator: U.S. Geological Survey Open-File Report 

2009–1057, 26 p., accessed June 30, 2012, at http://pubs.

usgs.gov/of/2009/1057. (This report supplements USGS OFR 

2004–1344.)

Berger, B.R., Ayuso, R.A., Wynn, J.C., and Seal, R.R., 2008, 

Preliminary model of porphyry copper deposits: U.S. Geological Survey Open-File Report 2008–1321, 55 p., accessed 

May 15, 2010, at http://pubs.usgs.gov/of/2008/1321.

Carlile, J.C., Digdowirogo, S., and Darius, K., 1990, Geologic 

setting, characteristics, and regional exploration for gold in 

the volcanic arcs of North Sulawesi, Indonesia, in Hedenquist, J.W., White, N.C., and Siddeley, G., eds., Epithermal 

gold mineralization of the circum-Pacific—Geology, geochemistry, origin and exploration, I: Journal of Geochemical 

Exploration, v. 35, p. 105–140.

Table G5. Undiscovered deposit estimates, deposit numbers, tract area, and deposit density for tract 142pCu7026, West Sulawesi—

Indonesia.

[NXX, estimated number of deposits associated with the xxth percentile; Nund, expected number of undiscovered deposits; s, standard deviation; Cv%, coefficient 

of variance; Nknown, number of known deposits in the tract that are included in the grade and tonnage model; Ntotal; total of expected number of deposits plus 

known deposits; km2, area of permissive tract in square kilometers; Ntotal/100k km2, deposit density reported as the total number of deposits per 100,000 km2. 

Nund, s, and Cv% are calculated using a regression equation (Singer and Menzie, 2005). In cases where individual estimates were tallied in addition to the consensus estimate, individual estimates are listed]

 Consensus undiscovered deposit estimates Summary statistics Tract area 

(km2

)

Deposit density 

(Ntotal/100k km2)

N90 N50 N10 N05 N01 Nund s Cv% Nknown Ntotal

0 1 2 3 3 1.1 0.98 91 0 1.1 60,270 1.8

Table G6. Results of Monte Carlo simulations of undiscovered resources for tract 142pCu7026, West Sulawesi—Indonesia.

Material

Probability of at least the indicated amount Probability of

0.95 0.9 0.5 0.1 0.05 Mean Mean or 

greater

None

Cu 0 0 650,000 7,900,000 15,000,000 3,400,000 0.21 0.3

Mo 0 0 0 33,000 81,000 19,000 0.14 0.68

Au 0 0 66 610 1,100 240 0.24 0.3

Ag 0 0 0 2,000 4,300 1,100 0.15 0.59

Rock 0 0 150 1,600 3,200 680 0.22 0.3
132 Porphyry Copper Assessment of Southeast Asia and Melanesia

Cooke, D.R., Heithersay, P.S., Wolfe, R., and Calderon, A.L., 

1998, Australian and western Pacific porphyry Cu-Au deposits: Journal of Australian Geology and Geophysics, 

v. 17, no. 4, p. 97–104.

Cox, D.P., 1986, Descriptive model of porphyry Cu-Au (Model 

20c), in Cox, D.P., and Singer, D.A., eds., 1986, Mineral 

deposit models: U.S. Geological Survey Bulletin 1693, p. 

110. (Also available at http://pubs.usgs.gov/bul/b1693/.)

Directorate of Mineral Resources and Inventory, 2004a, Digital 

geologic map: Jakarta, Indonesia, Indonesian Ministry 

of Energy and Mineral Resources, scale 1:1,000,000. 

[Proprietary data.]

Directorate of Mineral Resources and Inventory, 2004b, Digital 

mineral occurrence database: Jakarta, Indonesia, Indonesian 

Ministry of Energy and Mineral Resources. [Proprietary data.]

Djaswadi, S., 1993, Prospective of base metal minerals in 

Indonesia: Bandung, Ministry of Mines and Energy of 

Republic of Indonesia, Directorate of Mineral Resources 

Special Publication, 229 p. 

Duval, J.S., 2012, Version 3.0 of EMINERS—Economic 

Mineral Resource Simulator: U.S. Geological Survey Open 

File Report 2004–1344, accessed July 5, 2012, at http://

pubs.usgs.gov/of/2004/1344.

Garwin, S., Hall, R., and Watanabe, Y., 2005, Tectonic setting, 

geology, and gold and copper mineralization in Cenozoic 

magmatic arcs of southeast Asia and the west Pacific, in

Hedenquist, T.W., Thompson, J.F.H., Goldfarb, R.J., and 

Richards, J.P., eds., One hundredth anniversary volume 

1905–2005: Littleton, Colorado, Society of Economic Geologists, p. 891–930.

Geological Research and Development Centre, 1987–2000, 

Systematic Geologic Map, Indonesia, map nos. 2010, 2011, 

2012, 2013, 2014, 2015, 2016, 2109, 2110, 2111, 2112, 2113, 

2114, 2115, 2116, 2117: Bandung, Geological Survey of 

Indonesia, scale 1:250,000.

John, D.A., Ayuso, R.A., Barton, M.D., Blakely, R.J., Bodnar, 

R.J., Dilles, J.H., Gray, Floyd, Graybeal, F.T., Mars, J.C., 

McPhee, D.K., Seal, R.R., Taylor, R.D., and Vikre, P.G., 

2010, Porphyry copper deposit model, chap. B of Mineral 

deposit models for resource assessment: U.S. Geological 

Survey Scientific Investigations Report 2010–5070–B, 169 

p., accessed September 8, 2010, at http://pubs.usgs.gov/

sir/2010/5070/b/.

Richards, J.P., 2009, Postsubduction porphyry Cu-Au and epithermal Au deposits—Products of remelting of subductionmodified lithosphere: Geology, v. 37, no. 3, p. 247–250.

Root, D.H., Menzie, W.D., and Scott, W.A., 1992, Computer 

Monte Carlo simulation in quantitative resource estimation: 

Natural Resources Research, v. 1, no. 2, p. 125–138.

Sillitoe, R.H., 1995, Exploration and discovery of base- and 

precious-metal deposits in the Circum-Pacific region during 

the last 25 years: Tokyo, Society of Resource Geology, 

Resource Geology Special Issue no. 19, 119 p.

Singer, D.A., and Menzie, W.D., 2005, Statistical guides to 

estimating the number of undiscovered mineral deposits—An 

example with porphyry copper deposits, in Cheng, Qiuming, 

and Bonham-Carter, Graeme, eds., Proceedings of IAMG—

The annual conference of the International Association for 

Mathematical Geology: Toronto, Canada, York University, 

Geomatics Research Laboratory, p. 1028–1033.

Singer, D.A., Berger, V.I., Menzie, W.D., and Berger, B.R., 

2005, Porphyry copper density: Economic Geology, v. 100, 

no. 3, p. 491–514.

Singer, D.A., Berger, V.I., and Moring, B.C., 2008, Porphyry 

copper deposits of the world—Database and grade and 

tonnage models, 2008: U.S. Geological Survey Open-File 

Report 2008–1155, accessed June 1, 2011, at http://pubs.usgs.

gov/of/2008/1155/.

Soeria-Atmadja, R., Priadi, B., van Leeuwen, T.M., and 

Kavalieris, I., 1999, Tectonic setting of porphyry Cu-Au, 

Mo, and related mineralization associated with contrasted 

Neogene magmatism in the Western Sulawesi Arc: The Island 

Arc, v. 8, p. 47–55.

Taylor, D., and van Leeuwen, T.M., 1980, Porphyry-type 

deposits in Southeast Asia, in lshihara, S., and Takenouchi, S., 

eds., Granitic magmatism and related mineralization: Mining 

Geology, Special Issue, v. 8, p. 95–116.

U.S. Department of State, 2009, Small-scale digital international 

land boundaries (SSIB)—Lines, edition 10, and polygons, 

beta edition 1, in Boundaries and sovereignty encyclopedia 

(B.A.S.E.): U.S. Department of State, Office of the 

Geographer and Global Issues.

van Leeuwen, T.M., 1994, 25 years of mineral exploration and 

discovery in Indonesia: Journal of Geochemical Exploration, 

v. 50, p. 13–90.

van Leeuwen, T.M., Taylor, R., Coote, A., and Longstaffe, 

F.J. 1994, Porphyry molybdenum mineralization in a 

continental collision setting at Malala, northwest Sulawesi, 

Indonesia, in van Leeuwen, T.M., Hedenquist, J.W., James 

L.P., and Dow, J.A.S., eds., Indonesian mineral deposits—

Discoveries of the past 25 Years: Journal of Geochemical 

Exploration, v. 50, p. 279–315.

Walpersdorf, A., Rangin C., and Vigny, C., 1998, GPS 

compared to long-term geologic motion of the north arm of 

Sulawesi: Earth and Planetary Science Letters, v. 159, 

p. 47–55.
Appendix G—Tract 142pCu7026 133

120° E 122° E

2° S

6° S

!

!

INDONESIA

Kendari

Makassar

Sassak

Makassar Strait

Flores Sea

Gulf of Boni

Celebes Sea

Gulf of Tomini

Banda Sea

110°E 130°E

20°N

0°

20°S

INDIAN OCEAN

AUSTRALIA

PH

ID

MY

VN

Political boundary source: U.S. Department of 

State (2009)

Projection: Asia South Albers Equal Area Conic;

Central meridian 120° E; latitude of origin 15° S

0 50 100 150 200 KILOMETERS

0 50 100 MILES

EXPLANATION

Assessed porphyry copper tract

142pCu7026

Other porphyry copper tracts

Porphyry copper prospect;

prospects associated with other

tracts shown in gray

Area of Map

Figure G1. Map showing tract location and significant porphyry copper prospects for tract 142pCu7026, West 

Sulawesi—Indonesia. ID, Indonesia; MY, Malaysia; PH, Philippines; VN, Vietnam.
(

(

(

(

( ( ( (

( ( ( ( ( ( (

(

( ( ( ( ( ( ( ( ( ( (

( ( ( ( (

( (

(

(

(

(

( (

(

(

(

(

( ( (

( ( ( ( ( ( ( ( ( ( ( (

(

(

( (

( ( ( (

(

(

( ( ( (

(

(

(

( ( ( ( ( (

( (

(

(

(

(

(

(

( ( (

(

(

( (

(

(

(

( ( ( 

(

(

(

(

!

!

! !

!

JAVA TRENCH TIMOR TROUGH

PALU-KORO FAULT

KINABALU FAULT

PHILIPPINE

SEA PLATE

Kalimantan

Gulf of Carpentaria

Sassak

Bandung Surabaja

Semarang

INDONESIA

MALAYSIA

AUSTRALIA

INDONESIA

INDIAN OCEAN

South China Sea

Java Sea

Banda Sea

Timor Sea

Arafura Sea

Celebes Sea PACIFIC OCEAN

Sulu Sea

Makassar Strait

110° E 120° E 130° E

0°

10° S

Base from ESRI ArcGIS Online (2009)World Shaded ReliefPolitical boundary source: U.S. Department of State (2009)Projection: Asia South Albers Equal Area Conic;Central meridian 115° E; latitude of origin 15° S

0 200 400 600 800 KILOMETERS0 200 400 MILES

E

As 1PoPePeAu

( (

(

SuSpStrTh

Eu

Figure G2. Map showing the regional setting for tract 142pCu7026, West Sulawesi—Indonesia.
Appendix G—Tract 142pCu7026 135

( ( (

(

(

( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( 

( ( (

( (

( ( ( (

(

(

(

(

(

(

(

( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( (

( ( ( ( ( ( ( ( (

!

!

!

!

!

!

!

!

!

INDONESIA

INDONESIA

Kendari

Makassar

Samarinda

Balikpapan

Kupang

Sassak

North Sulawesi

PALU-KORO FAULT

West Sulawesi

Celebes Sea

Banda Sea

Flores Sea

Makassar Strait

118° E 122° E

2° N

6° S

Awak Au

Malala Mo

Base from ESRI ArcGIS Online (2009)

World Shaded Relief

Political boundary source: U.S. Department of State (2009)

Projection: Asia South Albers Equal Area Conic;

Central meridian 120° E; latitude of origin 15° S

0 50 100 150 200 KILOMETERS

0 50 100 MILES

EXPLANATION

Assessed porphyry copper tract

142pCu7026

Permissive intrusive rock

Porphyry copper prospect

Permissive volcanic rock

Australian continental crust

Eurasian continental crust

( (

(

Subduction zone

Spreading center

Strike-slip fault

Thrust fault

Other mineral prospect

INDIAN OCEAN

Savu Sea

Gulf of Tomini

BS

Figure G3. Map showing the distribution of permissive igneous rocks, tectonic features, and porphyry copper prospects 

for tract 142pCu7026, West Sulawesi—Indonesia. BS, Banggai-Sulu continental fragment.
136 Porphyry Copper Assessment of Southeast Asia and Melanesia

Mean Cu Mean Rock

Mean Ag

Mean Mo

Mean Au

0.01 0.1 1 10 100 1k 10k 100k 1M 10M 100M 1B 10B 100B

Material, in metric tons

1.00

0.90

0.80

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

Probability

Cu

Mo

Au

Ag

Rock

Mean Cu

Mean Mo

Mean Au

Mean Ag

Mean Rock

EXPLANATION

Figure G4. Cumulative frequency plot showing the results of Monte Carlo computer simulation of undiscovered 

resources in tract 142pCu7026, West Sulawesi—Indonesia. k, thousands; M, millions; B, billions; Tr, trillions.
Appendix H—Tract 142pCu7027 137

Appendix H. Porphyry Copper Assessment for Tract 142pCu7027, 

North Sulawesi-Sangihe—Indonesia

By Gilpin R. Robinson, Jr.1, Bambang Tjahjono Setiabudi2, Dwi Nugroho Sunuhadi2, Jane M. Hammarstrom1, 

Steve Ludington3

, Arthur A. Bookstrom4, Sewit A. Yenie1, and Michael L. Zientek4, with contributions from 

Gwaibo Kopi5

Deposit Type Assessed: Porphyry copper, copper-gold subtype

Descriptive model: Porphyry copper (Berger and others, 2008; John and others, 2010), Porphyry copper-gold 

(Cox, 1986; Cooke and others, 1998)

Grade and tonnage model: Porphyry copper, Cu-Au subtype (Singer and others, 2008)

Table H1 summarized selected assessment results.

Table H1. Summary of selected resource assessment results for tract 142pCu7027, North Sulawesi-Sangihe—Indonesia.

[km, kilometers; km2, square kilometers; t, metric tons]

Date of assessment Assessment 

depth (km)

Tract area 

(km2)

Known copper 

resources (t)

Mean estimate of 

undiscovered copper 

resources (t)

Median estimate of

undiscovered copper 

resources (t)

 February 2010 1 20,330 2,040,300 8,900,000 3,800,000

1

U.S. Geological Survey, Reston, Virginia, United States.

2

Directorate of Mineral Resources Inventory, Geological Agency of Indonesia, Bandung, Indonesia.

3

U.S. Geological Survey, Menlo Park, California, United States.

4

U.S. Geological Survey, Spokane, Washington, United States.

5

Geologic Survey of Papua New Guinea.

Location

The tract includes almost all of North Sulawesi (areas not included in tract 142pCu7026) and the southeastern part of 

Sangihe Island (fig. H1).

Geologic Feature Assessed

This tract includes the Miocene to Pliocene volcanic- and intrusive-rock part of the North Sulawesi-Sangihe magmatic arc.
138 Porphyry Copper Assessment of Southeast Asia and Melanesia

Delineation of the Permissive Tract

Tectonic Setting

The North Sulawesi magmatic arc is part of the 

1,200-km-long North Sulawesi-Sangihe magmatic arc, which 

has been active since the Eocene. The porphyry copper deposits in North Sulawesi are late Miocene to Pliocene in age. 

They formed in an island-arc setting developed on oceanic 

crust above two opposing subduction zones that formed as a 

result of northward displacement of Sulawesi over a developing south-dipping subduction zone in the Celebes Sea that initiated in response to late Tertiary interaction of the Australian 

and Pacific Plates (Carlile and others, 1990; Kavalieris and 

others, 1992; Perello, 1994). The regional geologic and tectonic setting of the tract is shown in figure H2 and is described 

in more detail below.

The North Sulawesi magmatic arc is an island-arc 

complex developed on Cretaceous to Paleogene oceanic crust 

(Carlile and others, 1990). It developed during multistage 

and multidirectional subduction from the Eocene to present 

(Kavalieris and others, 1992; Hall, 1996, 2002; Pearson and 

Caira, 1999; Simandjuntak and Barber, 1999) in the complex 

convergence zone of the Eurasian, Pacific, and Australian 

Plates (Carlile and others, 1990). Collision of the BanggaiSula continental crust fragment of the Australian Plate with 

Sulawesi displaced Sulawesi westward resulting in the 90 

degree clockwise rotation of the North Arm to its present 

east-west orientation and displacement of the North Sulawesi 

Arc northward over the Celebes Sea (fig. H2; Carlile and 

others, 1990; Walpersdorf and others, 1998). This westward 

displacement and rotation of the volcanic arc developed 

a series of extensional basins; volcanism tends to young 

progressively eastward along the North Arm of Sulawesi 

toward the Sangihe Trench that is the locus of Holocene 

volcanism (Carlile and others, 1990). Formation of the calcalkaline volcanic rocks, porphyritic diorite intrusions, and 

related porphyry copper deposits, occurred during magmaticarc activity from 11 to 2.5 Ma that has been related to the 

subduction of oceanic-rise microplates under North Sulawesi 

along the Sulawesi and Sangihe Troughs. Displacement of 

the arc system over the Celebes Sea has resulted in Pliocene 

to Pleistocene uplift of the composite-arc system. Rapid 

erosion associated with this uplift (Kavalieris and others, 

1992; Perello, 1994) exposed many of the Paleogene to early 

Miocene intrusions at depths greater than depths at which 

porphyry copper deposits are likely to occur.

Geologic Criteria

The geologic units that define the permissive tract are 

calc-alkaline igneous rocks of Miocene to Pliocene age (fig. 

H3). Some igneous-rock map units of uncertain Tertiary 

age, that span this age range but may be as old as Paleogene, 

have been included in the tract. Most of the plutonic rocks 

that crop out within the tract are numerous small bodies of 

Miocene to Pliocene diorite, quartz diorite, granodiorite, and 

granite (table H2).

Calc-alkaline volcanic rocks are considered permissive for porphyry copper deposits as they are localized near 

and often overlie intrusive centers that may host porphyry 

deposits and may include small, unmapped intrusive bodies 

within their borders. The volcanic rocks that define the tract 

are late Tertiary andesite flows and pyroclastics, andesite, 

lapilli tuff, trachyandesite, andesite porphyry, volcanic breccia, dacite, and basalt (table H2). Tertiary bimodal rhyolitebasalt sequences and andesitic tuffs that are primarily within 

marine carbonate rocks (fringing reefs bordering the oceanic 

islands) or clastic sedimentary rocks were not used to define 

the tract but are incorporated locally in the tract based on 

proximity to other permissive rock units. These distal volcanic deposits in carbonates and sediments are interpreted to 

be part of the accretionary-wedge complex, and their sites 

of deposition were not likely to be near the intrusive centers 

that host porphyry copper deposits (Taylor and van Leeuwen, 

1980).

Data used to construct the tract include 1:1,000,000-

scale geology (Directorate of Mineral Resources and Inventory, 2004a) and published 1:250,000-scale geologic maps 

(table H2) to identify areas of permissive rock types, based 

on the map legend attribute information describing map 

unit rock types, composition, and age. The regional mineral 

occurrence database (Directorate of Mineral Resources and 

Inventory, 2004b) was used to evaluate how the distribution of mineral occurrences corresponded to the prototract 

area. The 1:250,000-scale maps were scanned and rectified, 

and the areas of permissive rock units were digitized by 

hand to supplement the partial digital geology coverage at 

1:1,000,000-scale provided by the Indonesian Directorate of 

Mineral Resources (2004a). This enhanced GIS file was used 

to define the permissive tract. After choosing the polygons 

and groups of polygons that represent the surface expressions 

of permissive igneous intrusions, we applied a 10-km buffer 

around them to account for a spatial uncertainty of approximately 2 km in the digitized geology and deposit location data 

and the possibility that deposits may be associated with intrusions that expand beneath their surface expression and are also 

less than 1 km beneath the land surface. A 2-km buffer was 

applied around the permissive volcanic units, as these may be 

imprecisely located and partly covered.

A polygon aggregation and smoothing process was 

applied to the revised buffered permissive geologic map 

units to produce a preliminary permissive tract. The processing approximates manual delineation of a tract but is rapid 

and reproducible. The processing steps include (1) unioning 

all permissive unit buffers and other polygon features that 

comprise the framework of the tract, (2) aggregating unioned 

polygons using an aggregation distance of 50 km and a minimum hole size of 2,000 km2

, (3) simplifying the aggregated 

polygons using a bend-simplify algorithm with a simplification tolerance of 5 km, and (4) line-smoothing the simplified 
Appendix H—Tract 142pCu7027 139

polygons using an algorithm (PAEK, polynomial approximation with exponential kernel) with a tolerance of 20 km. Necking, thinning, and contraction of the polygons resulting from 

processing required a subsequent manual cleaning step (for 

example, to remove polygon necks). Final tract boundaries 

were compared to the permissive geologic features in source 

materials to ensure that original permissive boundaries were 

honored. All operations were carried out in ArcGIS 9.3 using 

standard tools available in the Arc Toolbox.

These revised preliminary-tract polygons were further 

modified by comparison with the scanned and rectified geologic maps to exclude areas where Quaternary volcanic rocks 

or sedimentary deposits are greater than 1 km in thickness. As 

a last step, the tract boundary was clipped to the shoreline to 

eliminate undersea areas (U.S. Department of State, 2009).

The outer boundary of the tract largely follows the coast 

line of the island chain in North Sulawesi and extends to the 

north to the island of Sangihe. The western border of the North 

Sulawesi tract is delineated by a set of northwest-striking 

regional faults that follow a rotation hingeline extending from 

the intersection of the north Sulawesi Trench with regional 

Palu-Koro Fault Zone (fig. H2; Walpersdorf and others, 1998). 

This fault zone marks the transition from dominantly Eurasian 

continental-crust basement to the west to dominantly oceanic 

crust to the east underlying the volcanic-arc system (fig. H2; 

Carlile and others, 1990). Neogene plate motions and the 

migration trend of volcanism differ across this rotation hingeline that delineates the North Sulawesi tract from the West 

Sulawesi tract. The eastern border of the tract is delineated by 

Quaternary stratovolcanoes, some active, along the eastern tip 

of North Sulawesi (Hall, 2002; Kavalieris and others, 1992; 

Simandjuntak and Barber, 1999). Much of the tract is covered 

with Quaternary and Neogene sedimentary and volcanic rocks. 

The North Sulawesi tract contains a number of national parks 

and nature reserves.

Known Deposits

Two porphyry copper-gold deposits with identified 

resources lie in the south-central part of the North Sulawesi 

tract (table H3). They are the Tapadaa (3.75 Ma, containing estimated resources of 43 Mt at 0.54 percent copper and 

0.075 g/t gold) and Tombulilato (3.0 Ma, containing estimated 

resources of 287 Mt at 0.63 percent copper and 0.47 g/t gold) 

deposits, which include the Cabang Kiri East (132 Mt), Sungai 

Mak (82 Mt), and Kayubulan Ridge (73 Mt) deposits (Singer 

and others, 2008). The primary copper mineralization at the 

Tapadaa and Tombulilato deposits occurs in small high-level 

quartz diorite bodies with local supergene enrichment (Lowder 

and Dow, 1976, 1978). The Tapadaa deposits are localized 

within northwest-striking structurally controlled blocks in a 

Table H2. Map units that define tract 142pCu7027, North Sulawesi-Sangihe—Indonesia.

[Map unit, geologic-age range, and principal rock types from 1:250,000 scale geologic maps, compiled by the Geological Research and Development Centre, 

Badung, Indonesia, 1987–2000]

Map unit Age range Rock types

Intrusive rocks

gd Miocene Granodiorite

gr Miocene Granite

Tmb Early to middle Miocene Diorite, quartz diorite

Tmbo Miocene Diorite, granodiorite

Tpb Pliocene Granodiorite, granite

QTi(d) Pliocene to Pleistocene Diorite

Volcanic rocks

Tmv Miocene Andesite, basalt

Tmvl Miocene Andesite, basalt

Tppv Pliocene Dacite, andesite

Tpwv Pliocene Andesite, basalt

tr Miocene Trachyte

Ttv Miocene Volcanic breccia

Tnbv Miocene to Pliocene Volcanics

QTi(a) Pliocene to Pleistocene Andesite
140 Porphyry Copper Assessment of Southeast Asia and Melanesia

Table H3. Identified porphyry copper resources in tract 142pCu7027, North Sulawesi-Sangihe—Indonesia.

[Ma, million years; Mt, million metric tons; t, metric ton; %, percent; g/t, gram per metric ton; Cu-Au subtype, deposits that have Au/Mo ratios >30 or average Au 

grades >0.2 g/t; NA, not applicable; n.d., no data. Contained Cu in metric tons is computed as tonnage (Mt × 1,000,000) × Cu grade (percent)]

Name Latitude Longitude Subtype Age 

(Ma)

Tonnage 

(Mt) Cu (%) Mo (%) Au 

(g/t)

Ag 

(g/t)

Contained 

Cu (t) Reference

Tapadaa 0.517 123.21 NA 3.75 43 0.54 n.d. 0.075 n.d. 232,200 Singer and others (2008), Djaswadi 

(1993), Lowder and Dow (1976), 

Lowder and Dow (1978), Taylor and 

van Leeuwan (1980),van Leeuwen 

(1994)

Tombulilato0.345 123.4 Cu-Au 3 287 0.63 n.d. 0.47 n.d. 1,808,100 Singer and others (2008), Carlile and 

Kirkegaard (1985), Carlile and others 

(1990), Djaswadi (1993), Lowder and 

Dow (1978), Pearson and Caira (1999), 

Perello (1994)

Table H4. Significant prospects and occurrences in tract 142pCu7027, North Sulawesi-Sangihe—Indonesia.

[Ma, million years; %, percent; n.d., no data]

Name Latitude Longitude Age (Ma) Comments Reference

Bulagidun 0.952 121.77 8.75 14.4 Mt at 0.61% Cu 

and 0.68 g/t Au; ≤0.2% 

Mo reported.

Carlile and others (1990), Djaswadi (1993), Lubis 

and others (1994), Pearson and Caira (1999), 

Taylor and van Leeuwan (1980) 

Sangihe 3.433 125.567 n.d. Includes Bawone 

prospect.

East Asia Minerals Corporation (2010)

few small multistage intrusions of quartz diorite of Pliocene 

age (van Leeuwen, 1994).

At Tombulilato, eight mineralized intrusive bodies of 

quartz diorites to dacite porphyries of late Pliocene age occur 

within an area of 20 km2

 (van Leeuwen, 1994). Ore-grade 

mineralization occurs in both argillic and advanced argillic 

alteration. The intrusions vary from cylindrical stocks to dikes 

and subhorizontal sills, often with hydrothermal breccias, 

emplaced into volcanic rocks (Lowder and Dow, 1978). The 

Tombulilato district was included in a national park in 1991.

Prospects, Mineral Occurrences, and Related 

Deposit Types

The Bulagidun porphyry prospect, in the northwestern 

corner of the tract, was discovered in 1987 by BHP-Utah 

(table H4). The copper-gold mineralization at Bulagidun 

occurs in breccia bodies that border a potassically altered 

diorite to quartz-diorite stock intruded into andesitic volcanic 

rocks dated at 9.4 Ma. The mineralization at Bulagidun differs 

from the other porphyry deposits in North Sulawesi by being 

slightly older, and it is hosted exclusively in breccias with 

tourmaline and potassium feldspar alteration. Trenching, soil 

and rock sampling, and exploratory drilling identified inferred 

resources of 14.4 Mt at 0.61 percent copper and 0.68 g/t gold 

(van Leeuwen, 1994). Bulagidun is not considered a known 

deposit as resources are likely open at depth (Singer and others, 2008).

The tract contains several epithermal gold deposits and 

sediment-hosted gold deposits that may have an association 

with porphyry systems. A number of epithermal gold occurrences in the Pani volcanic complex (Kavaleris and others, 

1990) are south of Bulagidun near the southwestern corner of 

the tract. Several epithermal gold deposits lie in the northeastern part of the tract on Sangihe Island. The Sangihe prospect 

is hosted by diorite and andesite plugs that have intruded a 

sequence of andesite flows and minor associated volcani-
Appendix H—Tract 142pCu7027 141

Table H5. Principal sources of information used for tract 142pCu7027, North Sulawesi-Sangihe—Indonesia.

[NA, not applicable]

Theme Name or title Scale Citation

Geology Digital geologic map of Indonesia 1:1,000,000 Directorate of Mineral Resources and Inventory (2004a)

Systematic geologic map, Indonesia 1:250,000 Geological Research and Development Centre (1987–2000)

Mineral

occurrences

Porphyry copper deposits of the world: 

database, map, and grade and tonnage 

models

NA Singer and others (2008)

Digital mineral occurrence database NA Directorate of Mineral Resources and Inventory (2004b)

clastic rocks that emanated from the Taware volcano in the 

southeastern part of Sangihe Island (table H4). Xenoliths of 

gabbro and diorite in the andesites suggest that mafic oceanic 

basement underlies the island. Epithermal gold mineralization 

exploration targets (both high- and low-sulfidation types) in 

volcanic rocks are related to copper and gold-bearing quartzvein stockworks associated with a diorite stock in andesitic 

volcanic rocks. Porphyry-copper-style mineralization occurs 

within the diorite stock and andesite with stockwork-vein 

systems, potassic alteration (biotite-magnetite) at depth grading upwards into phyllic (sericite) alteration, and late quartzcarbonate veins (Carlile and others, 1990). Although the 

exploration program is focused on epithermal gold deposits, 

the intrusion-hosted stockwork, outcrops of porphyry copper 

mineralization on Taware Ridge (Carlile and others, 1990), 

porphyry-style alteration, association of gold mineralization 

with magnetic lows at depth, and drill-core results all indicate potential for porphyry copper-gold mineralization at the 

prospect (East Asia Minerals Corporation, 2010).

Exploration History

There was regional- and prospect-scale exploration 

by the Dutch in the colonial period from the 1860s through 

the 1930s and deposit-scale exploration around mines and 

occurrences that began in the 1960s and continued episodically through the 1990s (van Leeuwen, 1994). Exploration 

geochemistry and mapping in the late 1960s through 1970s 

was initiated in North Sulawesi based on recognition of 

widespread Tertiary calc-alkaline rocks in an island-arc setting, a few known copper occurrences, and the possibility 

that the porphyry copper districts in the Philippines might 

extend southward into Sulawesi. The tract area is thoroughly explored on a district, regional, and deposit scale. 

The Tapadaa, Tombulilato, and Cabang Kiri deposits were 

discovered in the early 1970s based on stream-sediment 

exploration geochemistry followed by geologic mapping, 

rock geochemistry sampling, and drilling by Kennecott. 

The Tombulilato district was further explored in the early 

1980s by TEI and Utah International that outlined inferred 

resources of 295 Mt averaging 0.57 percent copper and 0.47 

g/t gold in three main mineralized areas (van Leeuwen, 

1994). The Bulagidun prospect was discovered in 1987 during an exploration geochemistry-sampling program searching 

for gold deposits. Exploration by BHP-Utah during the late 

1980s followed up on geochemical anomalies identified in 

the early 1970s. Drilling has taken place at the porphyry copper deposits and occurrences and at the larger gold prospects 

(Garwin and others, 1995).

Sources of Information

Principal sources of information used by the assessment 

team for delineation of 142pCu7027 are listed in table H5.

Grade and Tonnage Model Selection

The porphyry copper-gold subtype model (Singer 

and others, 2008) was selected to assess the undiscovered 

resources associated with porphyry copper deposits in the 

North Sulawesi tract (table 6). The model selection for the 

tract is based on the ore grade and tonnage characteristics of 

the Tampakan, Tombulilato, and Tapadaa deposits and Bulagidun prospect, the gold-rich nature of the related epithermal 

systems in the tract area, and geologic characteristics of the 

magmatic arc in this area. Based on the gold-grade classification criteria of Singer and others (2008), the Tombulilato 

deposit and Bulagidun prospect are classified as porphyry 

copper-gold type deposits. The arc magmatism is developed 
142 Porphyry Copper Assessment of Southeast Asia and Melanesia

on oceanic crust in a subduction setting that lacks influence 

from continental crust or sediments derived from continental crust, and the copper-gold subtype model is judged to be 

appropriate.

Estimate of the Number of Undiscovered 

Deposits

Rationale for the Estimate

There has been a high level of exploration dating from 

the Dutch period (1840s to 1930s) and from the 1960s by private mining companies. The tract area is thoroughly explored 

on a district, regional, and deposit scale, although areas with 

Quaternary volcanic or sediment cover are likely to be less 

well explored. Drilling has taken place at the porphyry copper deposits and occurrences and at the larger gold prospects 

(Garwin and others, 1995).

The number of undiscovered porphyry copper deposits 

in the North Sulawesi tract in the 90, 50, and 10 probability 

percentiles was estimated in February 2010 (table H6). The 

method of estimation was subjective and based on expert opinion and on analogy with geologically similar areas in other 

regions of Southeast Asia and the world.

The estimate in the North Sulawesi tract results in a mean 

of 2.8 expected undiscovered deposits, and when combined 

with the Tapadaa and Tombolilato deposits, results in a density 

of 23.5 deposits/100,000 km2. One consideration used in the 

estimation processes was that a number of porphyry coppergold deposits cluster in small areas (Singer and others, 2005), 

such as the Cabang Kiri East, Sungai Mak, and Kayubulan 

Ridge deposits, which were included in the grade and tonnage 

for Tombolilato. In addition, there are a number of epithermal gold occurrences throughout the tract that may have an 

association with porphyry systems. Sillitoe (1994) speculates 

that the epithermal gold mineralization in the Pani volcanic 

complex may be related to a deeper porphyry system. The estimate was based on a high degree of exploration known to have 

taken place within the tract, with consideration of a possibility 

that additional deposits might be hidden under the extensive 

sedimentary and volcanic cover on the island, particularly in 

the Sangihe area (table H2). The Sangihe prospect, located 

on the less explored Sangihe Island, is judged to be likely to 

contain ore grades and tonnages consistent with the porphyry 

copper-gold deposit subtype model and, together with the 

incompletely delineated resources at Bulagidun, provides part 

of the rationale for the a team’s estimate of 1 deposit at 90-percent confidence in this otherwise thoroughly explored tract. 

The team did not apply the deposit density models of Singer 

and others (2005) directly during the assessment, however 

the estimate of 23.5 deposits/100,000 km2

 is consistent with, 

and slightly above, the average of the observed range in their 

deposit- density model.

Probabilistic Assessment Simulation 

Results

Undiscovered resources for the North Sulawesi permissive tract 142pCu7027 were estimated by combining consensus estimates for numbers of undiscovered porphyry copper 

deposits (table H6) with the porphyry coper-gold subtype 

grade and tonnage model of Singer and others (2008) using 

the EMINERS program (Root and others, 1992; Bawiec and 

Spanski, 2012; Duval, 2012). Selected output parameters 

are reported in table H7. Results of the Monte Carlo simulation are presented as a cumulative-frequency plot (fig. H4). 

The cumulative-frequency plot shows the estimated resource 

volumes associated with cumulative probabilities of occurrence, as well as the mean, for each commodity and for total 

mineralized rock.

Table H6. Undiscovered deposit estimates, deposit numbers, tract area, and deposit density for tract 142pCu7027, North SulawesiSangihe—Indonesia.

[NXX, estimated number of deposits associated with the xxth percentile; Nund, expected number of undiscovered deposits; s, standard deviation; Cv%, coefficient of 

variance; Nknown, number of known deposits in the tract that are included in the grade and tonnage model; Ntotal, total of expected number of deposits plus known 

deposits; km2, area of permissive tract in square kilometers; Ntotal/100k km2, deposit density reported as the total number of deposits per 100,000 km2. Nund, s, and 

Cv% are calculated using a regression equation (Singer and Menzie, 2005). In cases where individual estimates were tallied in addition to the consensus estimate, 

individual estimates are listed]

 Consensus undiscovered deposit estimates Summary statistics Tract area 

(km2

)

Deposit density 

(Ntotal/100k km2)

N90 N50 N10 N05 N01 Nund s Cv% Nknown Ntotal

1 2 6 6 6 2.8 2 70 2 4.8 20,330 24
Appendix H—Tract 142pCu7027 143

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Table H7. Results of Monte Carlo simulations of undiscovered resources for tract 142pCu7027, North Sulawesi-Sangihe—Indonesia.

[Cu, copper; Mo, molybdenum; Au, gold; and Ag, silver, in metric tons; Rock, in million metric tons]

Material

Probability of at least the indicated amount Probability of

0.95 0.9 0.5 0.1 0.05 Mean Mean or 

greater

None

Cu 0 220,000 3,800,000 23,000,000 38,000,000 8,900,000 0.26 0.06

Mo 0 0 4,900 120,000 280,000 51,000 0.21 0.39

Au 0 22 310 1,700 2,600 650 0.3 0.06

Ag 0 0 590 6,000 12,000 2,900 0.19 0.29

Rock 0 52 790 4,900 8,000 1,800 0.28 0.06
144 Porphyry Copper Assessment of Southeast Asia and Melanesia

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no. 1–2, p. 47–55.
122° E 124° E 126° E

2° N

Sangihe

Tapadaa

Bulagidun

Tombulilato

INDONESIA

Celebes Sea

Molucca Sea

Gulf of Tomini

110°E 

20°N10°N

0°

10°S20°S

CHINA

ID

MY

INDIAN OCEA

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Figure H1. Map showing tract location, known deposits, and significant porphyry copper prospects for tract 142pCu7027, North Sulawesi-Sangi

ID, Indonesia; MY, Malaysia; PH, Philippines.
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Figure H2. Map showing the regional setting for tract 142pCu7027, North Sulawesi-Sangihe—Indonesia.
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Projection: Asia South Albers Equal Area Conic;Central meridian 100° E; latitude of origin 15° S

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Figure H3. Map showing the distribution of permissive igneous rocks, tectonic features, and porphyry copper deposits and prospects for tract 1

Sulawesi-Sangihe—Indonesia.
148 Porphyry Copper Assessment of Southeast Asia and Melanesia

0.01 0.1 1 10 100 1k 10k 100k 1M 10M 100M 1B 10B 100B

Material, in metric tons

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EXPLANATION

Figure H4. Cumulative frequency plot showing the results of Monte Carlo computer simulation of undiscovered 

resources 142pCu7027, North Sulawesi-Sangihe—Indonesia. k, thousands; M, millions; B, billions; Tr, trillions.
Appendix I—Tract 142pCu7019 149

Appendix I. Porphyry Copper Assessment for Tract 142pCu7019, 

Central Kalimantan—Indonesia and Sabah and Sarawak, 

Malaysia

By Gilpin R. Robinson Jr.1, Alexander Yan Sze Wah2, Bambang Tjahjono Setiabudi3, Dwi Nugroho Sunuhadi3, 

Jane M. Hammarstrom1

, Steve Ludington4, Arthur A. Bookstrom5, Sewit A. Yenie1, and Michael L. Zientek5, 

with contributions from Chen Shick Pei6

 and Gwaibo Kopi7

Deposit Type Assessed: Porphyry copper, copper-gold subtype

Descriptive model: Porphyry copper (Berger and others, 2008; John and others, 2010); Porphyry copper-gold 

(Cox, 1986; Cooke and others, 1998); Postsubduction porphyry copper-gold (Richards, 2009)

Grade and tonnage model: Porphyry copper, Cu-Au subtype (Singer and others, 2008)

Table I1 summarizes selected assessment results.

Table I1. Summary of selected resource assessment results for tract 142pCu7019, Central Kalimantan—Indonesia.

[km, kilometers; km2, square kilometers; t, metric tons]

Date of assessment Assessment 

depth (km)

Tract area 

(km2)

Known copper 

resources (t)

Mean estimate of 

undiscovered copper 

resources (t)

Median estimate of

undiscovered copper 

resources (t)

February 2010 1 144,580 940,800 40,000,000 25,000,000

Location

The tract incorporates several irregular elongated belts that trend from eastern Sabah and northeastern Kalimantan southwards through central to west Kalimantan into Sarawak, generally south of, but roughly parallel to, the Indonesia-Malaysia 

border in Borneo (fig. I1).

Geologic Feature Assessed

A dispersed belt of Tertiary intermediate intrusive and volcanic rocks that postdate pre-Eocene subduction and deformation, 

uplift, and erosion of pre-Miocene rocks and continental basement in Kalimantan.

1

U.S. Geological Survey, Reston, Virginia, United States.

2

Minerals and Geoscience Department, Sabah, Malaysia.

3

Directorate of Mineral Resources Inventory, Geological Agency of Indonesia, Bandung, Indonesia.

4

U.S. Geological Survey, Menlo Park, California, United States.

5

U.S. Geological Survey, Spokane, Washington, United States.

6

Coordinating Committee for Geoscience Programmes in East and Southeast Asia (CCOP) Technical Secretariat, Bangkok, Thailand.

7

Geologic Survey of Papua New Guinea.
150 Porphyry Copper Assessment of Southeast Asia and Melanesia

Delineation of the Permissive Tract

Tectonic Setting

The tract encloses a dispersed belt of late Oligocene 

to Pliocene intermediate intrusive and volcanic rocks that 

postdate folding, thrusting, uplift, and erosion of preMiocene rocks and continental basement in Kalimantan. 

The relation of these mid- to late Tertiary intrusive rocks 

to subduction is unclear, and the tectonic setting for the 

porphyry copper deposits that occur in this tract likely is 

related to the postsubduction porphyry copper-gold deposit 

model described by Richards (2009). The regional geologic 

and tectonic setting of the tract is shown in figure I2.

Geologic Criteria

The igneous rocks that define the tract occur as a dispersed belt of small-volume erosional remnants of high-level 

andesitic to trachy-andesitic volcanic centers of late Oligocene 

to Pliocene age, many of them associated with gold deposits 

and prospects (fig. I3). These calc-alkaline stocks and volcanic rocks are part of an elongated magmatic belt developed 

on continental crust that overlaps geographically, and partly 

overlaps but mostly postdates in time, with widespread uplift 

and erosion, folding of pre-Miocene sequences, and development of a regional unconformity in Borneo (Hutchison, 2005; 

Moss and others, 1998). This deformation, uplift, and rapid 

erosion is interpreted to record collision between the extended 

passive continental margin of South China that underthrust the 

northern part of the Eurasian Sundaland continental margin in 

Borneo and ended Cretaceous to Paleogene subduction of the 

proto-South China Sea (Hutchison, 2005; Hall and Wilson, 

2000). Slab-pull forces, together with plate reorganization and 

rotation associated with the impact of the Australia Plate with 

the Philippine Plate to the east, likely drove the South ChinaBorneo continent-continent collision in the Paleogene (Hall 

and Wilson, 2000).

The Cretaceous I-type calc-alkaline plutonic and volcanic 

rocks that occur in the Schwaner Mountains (fig. I3) in West 

Kalimantan and elsewhere within and bordering the tract are 

associated with the Cretaceous to Paleocene subduction event 

(Hutchison, 2005). These rock units have been excluded from 

the tract as they are associated with an earlier tectonic event. 

Porphyry copper deposits may have developed during this 

Cretaceous subduction event, but are unlikely to be preserved 

in central Kalimantan because of post-intrusion uplift and 

erosion. Copper and gold mineralization generally is not 

recognized in these rocks; however, the Ibu porphyry copper 

prospect in the western part of the tract has an uncertain age 

and may be related to this older subduction event (Viaene and 

others, 1981).

The late Oligocene to Pliocene intrusive and volcanic rocks in the tract have calc-alkaline to mildly alkaline 

chemistry. Some of the calc-alkaline intrusive rocks are low 

in potassium and enriched in sodium and are classified as 

adakites (Hutchison, 2005). Adakites are associated with 

gold mineralization at Bau and other prospects in the tract. In 

addition, shoshonitic basaltic-andesite volcanic rocks occur at 

some intrusive centers and host gold mineralization at Muyup 

and Masupa Ria (Abidin, 1996; Thompson and others, 1994). 

Although the limited chemical data for these rocks indicate 

a calc-alkaline to mildly alkaline (high K±Na calc-alkaline) 

arc-like chemical signature, regional data and reconstructions 

suggest that these rocks are unlikely to be related to active 

subduction as no convergent plate margins of this age have 

been identified in the area (Moss and others, 1998; Hutchison, 

2005). In contrast to the other Tertiary subduction-related 

magmatic arcs in Indonesia, the central Kalimantan magmatic 

belt and surrounding Borneo are aseismic for earthquakes of 

magnitude 5 or greater, and geophysical evidence for a subducted slab under the arc is not apparent (Garwin and others, 

2005). The dispersed belt of calc-alkaline magmatism may be 

related to counter-clockwise rotation of Borneo in response 

to plate reorganization following Australia’s collision with 

the Philippine Sea Plate (Hall, 1996) causing a thickening of 

the crust and mantle instability, possibly involving an older 

(Cretaceous?) subducted slab (Moss and others, 1998). Any 

porphyry copper deposits likely to occur in this tract probably 

are related to the postsubduction porphyry copper-gold deposit 

model described by Richards (2009). Based on geologic 

history in this tract, including tectonics, uplift and erosion, 

all porphyry copper deposits are likely to be of Miocene to 

Pliocene age.

Data used to construct the Central Kalimantan tract 

include the Geological Map of Borneo (1:1,500,000; Tate, 

2002), Digital Geological Map of Malaysia (1,1,000,000; 

Minerals and Geoscience Department, 2004), Geological Map 

of Sabah, Malaysia (1:500,000; Director-General Geological 

Survey of Malaysia, 1985), and digital GIS files for Indonesia, 

provided from the Coordinating Committee for Geoscience 

Programmes in East and Southeast Asia (CCOP) at a scale of 

1:1,000,000 (table I5). The CCOP developed these GIS files 

using the 1:1,000,000 Preliminary Geologic Map, Kalimantan 

(Pieters and Supriatna, 1989) These maps and map-based GIS 

databases were used to identify permissive rock types, based 

on the map legend attribute information describing map-unit 

rock types, composition, and age (table I2). In addition, the 

Kinabalu Fault Zone of Tokuyama and Yoshida (1974) has 

been used to define part of the tract in central Sabah, Malaysia 

because a series of small Tertiary porphyritic diorite and acidic 

dikes and sills (not shown at map scale) are localized along a 

series of northwest-trending faults in the Kinabalu Fault Zone. 

The Kinabalu Fault Zone includes serpentinites, peridotites, 

ophiolitic rocks, and cherts that mark a tectonic boundary 

interpreted as a continent-island arc collision zone in the Cretaceous to Paleogene in Sabah (Kosaka and Wakita, 1978).

After choosing the polygons and groups of polygons 

that represent the surface expressions of permissive igneous intrusions, a 10-km buffer was applied to account for a 

spatial uncertainty of approximately 2 km in the digitized 
Appendix I—Tract 142pCu7019 151

geology, deposit location data, and the possibility that deposits 

may be associated with intrusions that expand beneath their 

surface expression and are also less than 1 km beneath the 

land surface. A 2-km buffer was applied around the permissive 

volcanic units, as these may be imprecisely located and partly 

covered. A 15-km buffer was applied around the Kinabalu 

Fault Zone in central Sabah to delineate an area of mid- to late 

Tertiary dikes and sills (not shown at map scale) that might 

host porphyry copper deposits.

A polygon aggregation and smoothing process was 

applied to the revised buffered permissive geologic map 

units to produce a preliminary permissive tract. The processing approximates manual delineation of a tract but is rapid 

and reproducible. The processing steps include (1) unioning 

all permissive unit buffers and other polygon features that 

comprise the framework of the tract, (2) aggregating unioned 

polygons using an aggregation distance of 50 km and a minimum hole size of 2,000 km2

, (3) simplifying the aggregated 

polygons using a bend-simplify algorithm with a simplification tolerance of 5 km, and (4) line-smoothing the simplified 

polygons using an algorithm (PAEK, polynomial approximation with exponential kernel) with a tolerance of 20 km. Necking, thinning, and contraction of the polygons resulting from 

processing required a subsequent manual cleaning step (for 

example, to remove polygon necks). Final tract boundaries 

were compared to the permissive geologic features in source 

materials to ensure that original permissive boundaries were 

honored. All operations were carried out in ArcGIS 9.3 using 

standard tools available in the Arc Toolbox.

These revised preliminary-tract polygons were further 

modified by comparison with the scanned and rectified geologic maps to exclude areas where Quaternary volcanic rocks 

or sedimentary deposits are greater than 1 km in thickness. 

The final tract boundary was clipped to the shoreline to eliminate undersea areas (U.S. Department of State, 2009).

The plutonic rocks that crop out within the entire tract 

include numerous small bodies and intrusive centers of 

granodiorite, diorite, porphyritic dacite, and adamellite of late 

Oligocene to Pliocene age. Quartz monzonite bodies of late 

Miocene to Pliocene age also are present in Sabah. The volcanic rocks include high-level andesitic and trachy-andesitic 

intrusive centers and areas of basaltic andesite, andesite, and 

dacite. The distribution of the intrusive and volcanic rocks that 

define the tract is shown in figure I3. The Central Kalimantan 

tract includes at least 5 national parks and a number of nature 

reserves.

Known Deposits

The Mamut deposit (Kosaka and Wakita, 1978), the only 

known porphyry copper deposit with identified resources in 

the tract (table I3), is located within a cluster of porphyry prospects in the northeastern limb of the elongated magmatic belt 

in Sabah. It consists of disseminated copper sulfide minerals in 

Table I2. Map units that define tract 142pCu7019, Central Kalimantan—Indonesia.

[Map unit, geologic-age range, and principal rock types from 1:1,000,000 scale geologic maps, compiled by the Geological Research and Development Centre, 

Indonesia, (Pieters and Supriatna, 1989) and 1:500,000 scale geologic maps compiled by the Geological Survey of Malaysia (Minerals and Geoscience Department, 2004; Tate, 2002)]

Map unit Age range Rock types

Intrusive rocks

Toms Oligocene to Pliocene Granodiorite, diorite, porphyritic dacite

Toni Oligocene to Pliocene Intrusive center

Intrusive [Sabah Pr.] Late Miocene to Pliocene Quartz monzonite, granodiorite

Intrusive [Sabah Pr.] Pliocene Diorite, microgranodiorite, microgranite

Nmi (Tate, 2002); IgWS (Minerals and Geoscience Department, 

2004a) [Sarawak Pr.]

Miocene I-type intrusive bodies and centers, including andesite and 

basalt plugs

Volcanic rocks

Toma Oligocene to Pliocene Andesite

Tomj Oligocene to Pliocene Andesitic volcanics

Tomv Oligocene to Pliocene Intermediate volcanics

Extrusive [Sabah Pr.] Pliocene Dacite, andesite, porphyritic andesite
152 Porphyry Copper Assessment of Southeast Asia and Melanesia

brecciated, quartz-veined, granodiorite porphyry. The ore metals include copper, gold, silver, and zinc with small quantities 

of molybdenum and mercury. Mineable ore reserves are about 

83 million metric tons at 0.59 percent copper. Tonnage and 

grade estimates for the identified resources reported in Singer 

and others (2008) are 196 Mt at 0.48 percent copper, 0.001 

percent molybdenum, 2.5 g/t silver, and 0.5 g/t gold.

Prospects, Mineral Occurrences, and Related 

Deposit Types

The late-Oligocene to Pliocene Kalimantan magmatic 

belt (termed central Kalimantan Arc by Garwin and others, 

2005) is known principally for its epithermal gold deposits 

(Garwin and others, 2005). Many of the epithermal gold 

deposits in the tract are postulated to be the near-surface 

manifestations of porphyry copper systems (Corbett and 

Leach, 1998; Sillitoe and Bonham, 1990) and porphyry-style 

copper-gold and associated deposit types (table I4) are increasingly being recognized during ongoing exploration around 

the known epithermal gold deposits and associated volcanic 

centers in the tract (Geiger and others, 2002).

The Ibu porphyry copper occurrence (0.2 percent copper; 

0.4 to 96 ppm molybdenum; 0.41 g/t gold) lies in the western part of Central Kalimantan tract in Indonesia. Intrusive 

rocks associated with the Ibu porphyry copper occurrence are 

aplite and granodiorite porphyry, and nearby intrusive rocks 

are composed of diorite, quartz diorite, and tonalite. The Ibu 

prospect has an uncertain age, but may be as old as Cretaceous 

if it is related to the nearby dated diorite-quartz diorite pluton. 

In this association it would represent a porphyry system 

preserved in a shallow erosional remnant of the calc-alkaline 

intrusions emplaced during Cretaceous-Paleogene subduction 

of the proto-South China Sea. However, the Ibu prospect may 

be Tertiary age in a similar setting to other porphyry coppergold prospects, such as at Beruang Trengah, where small 

mid-Tertiary igneous centers have intruded into the contact 

zone between older Cretaceous plutons and adjacent metasedimentary rocks. Alteration minerals associated with the Ibu 

porphyry copper prospect include biotite, sericite, albite, 

carbonate minerals, magnetite, chlorite, and epidote, as well as 

tourmaline and zeolite. Sulfide and ore minerals include bornite, chalcopyrite, molybdenite, pyrite, galena, gold, sphalerite, 

bournonite, and cosalite (Pb2

Bi2S5). Supergene minerals and 

associated ore minerals include chalcocite, covellite, digenite, 

and limonite (Viaene and others, 1981).

All other known gold and gold-copper prospects in the 

tract are mid-Tertiary or younger in age, such as the Tertiary 

Bau epithermal gold deposit that lies north of Ibu in Malaysia. 

Bau is considered to be a sediment-hosted or Carlin-type disseminated gold deposit associated with the outlying alteration 

surrounding and overlying porphyry intrusion centers (Sillitoe 

and Bonham, 1990). At least four porphyry stocks in the 30 

km by 8 km Bau District exhibit porphyry-style mineralization, including potassic and sericitic alteration with quartz 

stockworks carrying low-grade copper-molybdenum-gold 

mineralization (Sillitoe and Bonham, 1990). Gold has been 

mined in the Bau District since at least the last century with a 

recorded output of about 44,688 kg gold. Mining first started 

from 1899 to 1921 where nearly 31,104 kg of gold was produced. Other areas of weak porphyry type copper-gold mineralization are present in West Sarawak along with surrounding 

gold deposits in the region (Viaene and others, 1981; Singer 

and others, 2005).

The large Kelian, Indomuro, Muyup, and Manparia epithermal gold deposits are associated with felsic to intermediate 

porphyritic bodies in the south-central part (Banjarmansin) 

of the Central Kalimantan tract (Setiabudi, 2001). The Mount 

Muro deposit is a quartz-alunite gold deposit in a diatreme 

breccia pipe. The Masuparia porphyry copper-gold prospect 

borders the Mount Muro gold mine and the Mount Muro 

deposit is likely a near-surface manifestation of the deeper 

porphyry copper system exposed at Masuparia (Prosperity 

Resources Limited, 2010). Kelian is a disseminated, low sulfidation, epithermal gold deposit. Similar to Mount Muro, the 

epithermal gold mineralization at Kelian was preceded by and 

is hosted in a maar-diatreme breccia complex (Davis and others, 2008). The Kelian mine ceased its primary mining operations in 2004. The Baroi gold prospect is operated by Kalimantan Gold Corporation, Ltd., and is interpreted as related 

to a porphyry system (Directorate of Mineral Resources and 

Table I3. Identified porphyry copper resources in tract 142pCu7019, Central Kalimantan—Indonesia.

[Ma, million years; Mt, million metric tons; t, metric ton; %, percent; g/t, gram per metric ton; Cu-Au subtype, deposits that have Au/Mo ratios >30 or average Au 

grades >0.2 g/t. Contained Cu in metric tons is computed as tonnage (Mt × 1,000,000) × Cu grade (percent)]

Name Latitude Longitude Subtype Age 

(Ma)

Tonnage 

(Mt) Cu (%) Mo 

(%)

Au 

(g/t)

Ag 

(g/t)

Contained 

Cu (t) Reference

Mamut 6.033 116.46 Cu-Au 7 196 0.48 0.001 0.5 2.5 940,800 Singer and others (2008),Clark (1993), 

Imai (2000), Kirk (1967), Kosaka and 

Wakita (1978), Nagano and others (1977), 

Tarkian and Stribrny (1999), Taylor and van 

Leeuwan (1980), United Nations (1985)
Appendix I—Tract 142pCu7019 153

Table I4. Significant prospects and occurrences in tract 142pCu7019, Central Kalimantan—Indonesia.

[Rank 4=Prospect listed in global database of Singer and others (2008) or <16,000 t of ore established by drilling. Rank 3=drilled, with >20 m of 0.2% or more 

Cu. Rank 2=drilled or trenched with <20 m of 0.2% Cu or <0.2% Cu, or past or ongoing exploration. Rank 1=copper occurrence that may be related to porphyrytype mineralization based on stream sediment or magnetic anomaly or location along structural trend. n.d., no data; %, percent; g/t, grams per metric ton; km, 

kilometers; m, meters; n.d., no data; Ma, million years; Mt, million meteric tons]

Name Latitude Longitude Age 

(Ma) Comments Reference Rank

Kalimantan 

Gold (KGC 

CoW)

–0.583 113.333 n.d. Includes the following prospects: Beruang Tengah, 

Beruang Kanan, Tumbang Huoi, Mamuring, Kalang. 

Surface sampling at Beruang Kanan has defined a 

1,100 m long by 400–600 m wide zone of >0.1% Cu 

and broad spaced drilling had delineated 80–90 Mt 

at 0.5–0.6% Cu to a depth of about 200 m; 167 m at 

0.59% Cu in porphyry style alteration; Grade 0.89% 

Cu from a 79 m drill hole interval on the Beruang 

Kanan prospect. The broad elements of porphyry 

system are present at Beruang Tengah, but grades 

encountered in the shallow drilling to date are not 

economic.

Geiger and others (2002), 

Management Report (2009), 

Kalimantan Gold Corporation, Ltd. 

(2008, 2010)

4

Masuparia -0.56 114.022 n.d. Drill core intercepts in porphyry Cu-Au 

mineralization identified in Phelps Dodge Corp. 

prospect bordering the Mount Muro gold deposit. 

Drill core assays report 0.18–0.26% Cu and 0.32–

0.50 g/t Au. Geophysical studies indicate a larger 

porphyry system than has been drill tested

Corbett and Leach (1998), Prosperity 

Resources Limited (2010)

4

Baroi gold 

prospect

-0.5 113.18 n.d. Drill hole intersections 5 to 24 m at 0.12 to 2.16% 

Cu, 0.02 to 0.11 g/t Au, 2 to 37.4 g/t Ag. Exposed. 

Prospect was 83 m at 2.64% Cu and 0.22g/t Au

Kalimantan Gold Corporation, Ltd. 

(2003, 2004, 2008)

4

Nungkok 6.1 116.466 8 0.42 to 0.57% Cu. In drill core 0.008 to 0.025% Mo. Saigusa (1973), Nagano and others 

(1977), Taylor and Van Leeuwen 

(1980), Singer and others (2008)

4

Bongkud 6.033 116.75 n.d. A 5 km long WNW porphyry Cu zone, intersects: 331 

m at 0.31% Cu, 0.7 g/t Au; 169 m at 0.4% Cu and 

0.9 g/t Au; 123 m at 0.43% Cu, 0.95 g/t Au; 74 m at 

0.57% Cu, 0.95 g/t Au. Oxidized zone 45 m thick at 

3.5% Cu.

Feebrey (2001), Imai (2000), Perilya 

(2007), United Nations (1985), Singer 

and others (2008)

4

Mansur -0.533 113.2 n.d. A review of prospects in the immediate area suggests 

the present level of erosion has exposed the upper 

levels of the Mansur porphyry system. The deeper 

seated magnetic anomaly represents a valid porphyry 

Cu target at depth. Drill intercepts below soil Cu 

anomaly area report low grade (0.2% Cu) porphyrystyle mineralization.

Geiger and others (2002), 

Management Report (2009)

3

Ibu 0.833 109.25 105? Porphyry copper prospect of uncertain age. Viaene and others (1981), Singer and 

others (2008)

2

Sungai Imbak 5.267 117.117 n.d. Sulfide veins genetically related to diorite porphyry 

sills and dikes.

[Malaysia] Task Force 4 (1998) 1

Ruwai -1.367 111.167 n.d. Porphyry Cu-Au prospect with adjacent skarn/

replacement mineralization.

Scorpion Mineral (1998) 1
154 Porphyry Copper Assessment of Southeast Asia and Melanesia

Inventory, 2004b). The Mansur porphyry copper-gold prospect 

was identified during exploration activity in the early 1990s 

following stream-sediment gold anomalies identified in the 

area during the 1980s. The Mansur prospect is located within 

a large circular feature that has an associated strong magnetic 

anomaly, coinciding with a mid-Tertiary diorite intrusion 

and younger feldspathic porphyry dikes intruded into clastic 

metasedimentary rocks. A halo of high copper concentrations in soils is localized along the western diorite-hornfels 

contact (Geiger and others, 2002). Epithermal gold mineralization hosted by a diatreme-dacite dome complex occurs at 

Lakapoi, located 10-km south-southwest of Mansur, and it 

likely formed at a shallower level than the porphyry system at 

Mansur. Porphyry copper-gold prospects at Beruang Tengah 

(including the nearby Beruang Kanan prospect) are located in 

a 10–12-km-wide circular feature that lies at the intersection 

of northeast and northwest trending structures. The coppergold mineralization occurs in a number of andesite-to-dacite 

and quartz-diorite intrusions that have been emplaced at the 

contact between metasedimentary rocks to the west and older 

granodiorites to the east (Geiger and others, 2002). The Bukit 

Mantri and Nagos epithermal gold deposits are present in the 

south part of the tract (Yan, 1991; United Nations, 1985). A 

number of gold placer deposits also are present within the 

tract.

A few porphyry copper-gold prospects and occurrences 

are present in the northeast part of the tract in Sabah. The 

Mamut deposit and the Nungkok and Bungkud (Bukit Tampang) are nearby porphyry copper-gold prospects. Five of the 

porphyry copper-gold prospects in table I4 are in the Singer 

and others (2008) porphyry copper database (rank=4; table I4) 

and seven of the prospects have been drilled or trenched during exploration (rank>1; table I4).

Exploration History

Exploration for gold and porphyry copper deposits was 

done in the Western Kalimantan tract on a regional scale and 

some prospect exploration and sampling was done at the more 

significant mineral occurrences. Gold mining has taken place 

at Bau since the early 1900s. The Ibu porphyry copper occurrence was discovered in the 1970s. Geochemical and airborne 

geophysical surveys were done by both mineral-exploration 

companies and government agencies in West Sarawak and 

West Kalimantan in the 1980s.

The Mamut porphyry copper deposit was discovered in 

1966. The mine ceased operation in mid-1999 after operating 

for about 24 years. Exploration took place in the tract in the 

late 1960s with geochemical prospecting over the entire area 

with some airborne geophysics on regional- and districtscales. Bongkud was discovered in 1999. The major exploration in the Sabah Central belt tract was done by the UNDP 

Labuk Valley Project (1964–1967), Malaysian-German 

Mineral Exploration project (1980–1985) and MMAJ-GSM 

Supra Regional Project Central Sabah Project (1990–1996). 

The Mamut copper deposit was mined out after 24 yrs of 

operation, producing a total of 2.4 million metric tons of 

copper concentrate (600,000 t of copper), 44.55 t of gold, 

and 294.49 t of silver.

The area within the North Central Kalimantan tract in 

the area of the Kalimantan Gold Corporation, Ltd. (KGC), 

contract of work (COW) area has been explored extensively 

by private mining companies, particularly in the 1980s and 

1990s. Specific prospect-scale exploration has taken place at 

the Mount Muro deposit. Exploration activities by the KGC 

since 1990 used regional geochemical, geophysical, and 

field-mapping methods to identify more than 30 porphyry and 

porphyry- related copper-gold prospects in central Kalimantan, 

few of which had any detailed exploration as of 2002 (Geiger 

and others, 2002). Preliminary exploration targets have been 

identified from large circular features that are evident on satellite, Landsat radar, and aerial-photo images. These features 

commonly coincide with mid- to late Tertiary intrusions and 

are associated with circular and donut-shaped aeromagnetic 

anomalies (Geiger and others, 2002). Targeted field mapping 

and geochemical surveys have been used to further define 

exploration targets in the KGC prospect area.

Sources of Information

Principal sources of information used by the assessment 

team for delineation of 142pCu7019 are listed in table I5.

Grade and Tonnage Model Selection

The grade and tonnage model used in this assessment 

was the porphyry copper-gold subtype described by Singer 

and others (2008), and this subtype is the target of most 

current exploration for porphyry copper deposits in the 

tract (table 6). The geologic characteristics and reported ore 

grades and tonnages are consistent with the porphyry coppergold subtype as described by Singer and others (2008). The 

reported average gold grade of 0.5 g/t for Mamut is greater 

than the gold-grade criteria (>0.2 g/t), and the Au/Mo ratio 

of 500 is greater than the Au/Mo-ratio criteria (Au/Mo>30) 

used by Singer and others (2008) to classify deposits as 

copper-gold subtype. The geologic features and tectonic 

setting of the tract also is consistent with the postsubduction 

tectonic model for porphyry copper-gold deposits described 

by Richards (2009).

Estimate of the Number of Undiscovered Deposits

Rationale for the Estimate

The results of a preliminary assessment done in February 2005 for porphyry copper tracts in Borneo were reviewed 
Appendix I—Tract 142pCu7019 155

in 2009 and 2010. Revised estimates were developed using 

larger-scale geologic map information and incorporating 

the results of more recent exploration activity and geologic 

research on porphyry copper-gold deposits in the area. The 

assessment team redefined the 2005 preliminary tract boundaries and reestimated the number of porphyry copper-gold 

deposits in the Central Kalimantan tract at the 90, 50, and 

10 probability confidence levels during February 2010 on 

the basis of one known porphyry copper or porphyry-related 

deposit and a number of prospects and exploration targets 

(table I6). The method of estimation was subjective and 

based on expert opinion and on analogy with geologically 

similar areas.

The estimate was influenced by an identified porphyry 

copper occurrence in the western part of the tract at Ibu and 

mid-Tertiary intrusions in West Sarawak that have petrologic characteristics and alteration consistent with porphyry 

copper-style (potassic, phyllic) alteration. Geochemical 

surveys have identified soil copper anomalies at Sebemban, 

Bukit Punda, Mudieng and Bukit Nimong.

Exploration for porphyry copper-gold deposits is ongoing 

in the south-central part of the tract (Geiger and others, 2002), 

Table I5. Principal sources of information used for tract 142pCu7019, Central Kalimantan—Indonesia.

[NA, not applicable]

 Theme Name or title Scale Citation

Geology Preliminary geologic map, Kalimantan 1:1,000,000 Pieters and Supriatna (1989)

Geological map of Borneo 1:1,500,000 Tate (2002)

Digital geologic map of Malaysia 1:1,000,000 Minerals and Geoscience Department (2004)

Digital geologic map of Indonesia 1:1,000,000 Directorate of Mineral Resources and Inventory 

(2004a)

Geological map of Sabah 1:500,000 Director-General Geological Survey of Malaysia 

(1985)

Mineral occurrences Porphyry copper deposits of the world: 

database, map, and grade and tonnage 

models

NA Singer and others (2008)

Mineral resource map of Asia 1:35,000,000 Kamitani, and Naito, eds. (1998)

Digital mineral occurrences database NA Minerals and Geoscience Department (written commun., 2004)

Digital mineral occurrences database 1:1,000,000 Directorate of Mineral Resources and Inventory 

(2004a,b)

Atlas of mineral resources of the 

ESCAP region, v. 1, Malaysia

NA United Nations (1985)

Table I6. Undiscovered deposit estimates, deposit numbers, tract area, and deposit density for tract 142pCu7019, Central Kalimantan—Indonesia.

[NXX, Estimated number of deposits associated with the xxth percentile; Nund, expected number of undiscovered deposits; s, standard deviation; Cv%, coefficient of 

variance; Nknown, number of known deposits in the tract that are included in the grade and tonnage model; Ntotal, total of expected number of deposits plus known 

deposits; km2

, area of permissive tract in square kilometers; Ntotal/100k km2, deposit density reported as the total number of deposits per 100,000 km2. Nund, s, and 

Cv% are calculated using a regression equation (Singer and Menzie, 2005)]

 Consensus undiscovered deposit estimates Summary statistics Tract area 

(km2

)

Deposit density 

(Ntotal/100k km2)

N90 N50 N10 N05 N01 Nund s Cv% Nknown Ntotal

3 8 30 30 30 13 10 78 1 14 144,580 10
156 Porphyry Copper Assessment of Southeast Asia and Melanesia

Table I7. Results of Monte Carlo simulations of undiscovered resources for tract 142pCu7019, Central Kalimantan—Indonesia.

[Cu, copper; Mo, molybdenum; Au, gold; and Ag, silver; in metric tons; Rock, in million metric tons]

Material

 Probability of at least the indicated amount Probability of

0.95 0.9 0.5 0.1 0.05 Mean Mean or 

greater

None

Cu 1,000,000 2,800,000 25,000,000 100,000,000 130,000,000 40,000,000 0.38 0.03

Mo 0 0 95,000 640,000 890,000 230,000 0.31 0.11

Au 100 250 1,900 6,900 8,600 2,900 0.39 0.03

Ag 0 230 5,400 38,000 56,000 13,000 0.29 0.07

Rock 240 640 5,200 20,000 24,000 8,100 0.39 0.03

and new porphyry copper-gold discoveries may occur in this 

area. The estimate was influenced by the nature and occurrence of porphyry and epithermal copper-gold prospects in 

this area, such as the Baroi, Beruang Kanan, Mansur, and 

Masuparia prospects, as well as several epithermal gold prospects that may be surface manifestations of porphyry coppergold-related systems (Corbett and Leach, 1998). Also taken 

into consideration for the estimate was the fact that from 

1987 to 2002 more than 30 prospective porphyry copper-gold 

exploration targets were identified in the south-central part 

of the tract and that few of these have been explored in any 

detail (Geiger and others, 2002). A number of gold and copper occurrences or prospects occur in the overall tract area, 

and at least four major epithermal gold districts within the 

tract are considered to have some relationship to porphyrystyle systems. Seven prospects included in table I4 have been 

drilled or trenched during exploration reporting intercepts 

with grades exceeding 0.2 percent copper (rank>1; table 

I4); five of the prospects are in the Singer and others (2008) 

database.

Other factors taken into consideration for the estimation 

were (1) the recognition that exploration for porphyry-style 

copper-gold deposits in the tract mostly began in the 1980s; 

(2) that more than 750 small intrusive centers of appropriate age, chemistry, and setting to potentially host porphyry 

deposits occur in the tract; (3) that most of these centers are 

in remote areas in the central part of the tract where few 

have received even reconnaissance exploration; and (4) that 

if even a small proportion of these intrusive centers host 

porphyry-style systems, a number of undiscovered porphyry 

copper-gold deposits may occur in the tract. The 90-percent 

confidence-level estimate of three undiscovered deposits is 

consistent with the underexplored nature of the tract and the 

large number of identified porphyry prospects. Eight undiscovered deposits at 50-percent confidence level was judged 

appropriate based on the exploration status of the tract and 

the large number of small intrusive centers of appropriate 

age, chemistry, and setting that potentially could host porphyry deposits.

The estimate resulted in a mean of 13 expected undiscovered deposits and when added to the Mamut deposit 

resulted in a density of 10.0 deposits/100,000 km2

 (table I6), 

consistent with the observed range, but on the low-range 

side, of porphyry deposit density as reported by Singer and 

others (2005).

Probabilistic Assessment Simulation 

Results

Undiscovered resources for the tract were estimated by 

combining consensus estimates for numbers of undiscovered 

porphyry copper deposits (table I6) with the copper-gold 

porphyry subtype model (Singer and others, 2008) using the 

EMINERS program (Root and others, 1992; Bawiec and 

Spanski, 2012; Duval, 2012). Selected output parameters are 

reported in table I7. Results of the Monte Carlo simulation are 

presented as a cumulative frequency plot (fig. I4). The cumulative frequency plot shows the estimated resource volumes 

associated with cumulative probabilities of occurrence, as well 

as the mean, for each commodity and for total mineralized rock.

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158 Porphyry Copper Assessment of Southeast Asia and Melanesia

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Appendix I—Tract 142pCu7019 159

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110° E 115° E 5° N0° Ibu Ruwai Mamut Mansur Nungkok Bongkud Masuparia Sungai Imbak Baroi gold prospect Kalimantan Gold (KGC CoW) MALAYSIA INDONESIA BRUNEI SOUTH CHINA SEA Sulu Sea Celebes Sea Makassar Strait 100°E 

20°N0° 20°S 

CHIN

THID 

MY 

V

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Political boundary source: U.S. Department of State (2009) Projection: Asia South Albers Equal Area Conic; Central meridian 115° E; latitude of origin 15° S 0 50 100 150 200 KILOMETERS 0 50 100 MILES EX

OtheAsse142pPorp

Porp

Figure I1. Map showing tract location, known deposits, and significant porphyry copper prospects for tract 142pCu7019, Central Kalimantan—IndMY, Malaysia; PH, Philippines; TH, Thailand; VN, Vietnam.
Figure I2. Map showing the regional setting for tract 142pCu7019, Central Kalimantan—Indonesia.

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Kalimantan Gold(KGC CoW)

JAVA TRENCH

PALU-KORO FAULT

KINABALU FAULT

COTOBATO FAULT

INDONESIA

MALAYSIA

MALAYSIA

CAMBODIA VIETNAM

THAILAND

THAILAND

MYANMAR

INDONESIA

INDONESIA

PHILIPPINES

West Sulawesi

SOUTH CHINA SEA

Gulf of Thailand

Andaman Sea

INDIAN OCEAN

Java Sea

Celebes Sea

Makassar Strait

Banda Sea

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Semarang

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Ho Chi Minh City

100° E 110° E 120° E

10° N

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Base from ESRI ArcGIS Online (2009)World Shaded ReliefPolitical boundary source: U.S. Department of State (2009)Projection: Asia South Albers Equal Area Conic;Central meridian 115° E; latitude of origin 15° S

0 200 400 600 800 KILOMETERS

0 200 400 MILES

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( ( ( MALAYSIA INDONESIA Ibu Ruwai Mansur Baroi gold prospect Kalimantan Gold (KGC CoW) Mamut Nungkok Bongkud Masuparia Sungai Imbak South China Sea Celebes Sea Sulu Sea Makassar Strait 110°E 115°E 5°N0° KINABALU FAULT Base from ESRI ArcGIS Online (2009) World Shaded Relief Political boundary source: U.S. Department of State (2009) Projection: Asia South Albers Equal Area Conic; Central meridian 100° E; latitude of origin 15° S 0 50 100 150 200 KILOMETERS 0 50 100 MILES E

Ass 14PorPorPerPerEur

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Schwaner Mountains Figure I3. Map showing the distribution of permissive igneous rocks, tectonic features, and porphyry copper deposits and prospects for tract 14

Kalimantan—Indonesia.
Appendix I—Tract 142pCu7019 163

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

Probability

Material, in metric tons

0.01 0.1 1 10 100 1k 10k 100k 1M 10M 100M 1B 10B 100B

Cu

Mo

Au

Ag

Rock

Mean Cu

Mean Mo

Mean Au

Mean Ag

Mean Rock

EXPLANATION

Mean Cu

Mean Mo

Mean Au

Mean Ag

Mean Rock

Figure I4. Cumulative frequency plot showing the results of Monte Carlo computer simulation of undiscovered resources in tract 

142pCu7019, Central Kalimantan—Indonesia. k, thousands; M, millions; B, billions; Tr, trillions.
164 Porphyry Copper Assessment of Southeast Asia and Melanesia 

Appendix J. Porphyry Copper Assessment for Tract 142pCu7201, 

Ambon Arc, Central Molucca Islands—Indonesia

By Jane M. Hammarstrom1, Bambang Tjahjono Setiabudi2, Dwi Nugrono Sunuhadi2, Gilpin R. Robinson, Jr.1, 

Connie L. Dicken1

, Steve Ludington3, Arthur A. Bookstrom4, and Michael L. Zientek4, with contributions from 

Gwaibo Kopi5

 and Dennis P. Cox3

Deposit Type Assessed: Porphyry copper, copper-gold subtype

Descriptive model: Porphyry copper (Berger and others, 2008; John and others, 2010); Porphyry copper-gold 

(Cox, 1986; Cooke and others, 1998)

Grade and tonnage models: Porphyry copper, copper-gold subtype (Singer and others, 2008)

Table J1 summarizes selected assessment results.

Table J1. Summary of selected resource assessment results for tract 142pCu7201, Ambon Arc, Central Molucca Islands—Indonesia.

[km, kilometers; km2, square kilometers; t, metric tons; n.d., no data]

Date of 

assessment

Assessment 

depth (km)

Tract 

area 

(km2)

Known 

copper 

resources (t)

Mean estimate of 

undiscovered copper 

resources (t)

Median estimate of

undiscovered copper

resources (t)

February 2010 1 1,540 n.d. 3,100,000 660,000

Location

The tract includes Ambelau, Ambon, Haraku, Saparua, Nusa Luat, Kelang, Manipa, and western Seram Islands, Indonesia 

(fig. J1).

Geologic Feature Assessed

Pliocene-Quaternary Ambon island arc (northern Outer Banda Arc), eastern Indonesia.

1

U.S. Geological Survey, Reston, Virginia, United States.

2

Center for Geological Resources, Geological Agency of Indonesia, West Java, Indonesia.

3

U.S. Geological Survey, Menlo Park, California, United States.

4

U.S Geological Survey, Spokane, Washington, United States.

5

Mineral Resources Authority, Papua New Guinea.
Appendix J—Tract 142pCu7201 165

Delineation of the Permissive Tract

Tectonic Setting

The tract outlines igneous rocks that are permissive for 

porphyry copper deposits within the Pliocene-Quaternary 

Ambon Arc. The Ambon Arc extends from Ambelau Island 

across western Seram and Ambon Island to the small islands 

of the Banda Archipelago (figs. J1, J2). The Ambon Arc 

represents the northernmost, curved segment of the Banda 

Arc system. The west-facing, curvilinear Banda Arc system, 

which borders the Banda Sea from Wetar to Ambon, formed at 

the intersection of the Indo-Australian, Pacific, and Eurasian 

Plates. Tectonic models proposed for the Banda Sea in eastern 

Indonesia have interpreted the Ambon Arc as (1) a segment 

of the east-west-trending Sunda-Banda Arc that has been 

displaced to the north and rotated counter-clockwise since 

the Miocene as a consequence of northward and westward 

motion of the Australian and Pacific Plates, respectively; (2) 

not related to subduction; or (3) the result of active subduction along the Seram Trough (Honthaas and others, 1999). 

More recent seismic and stratigraphic studies suggest that the 

Seram Trough is a foredeep at the front of a developing fold 

and thrust belt on Seram that represents a post-Miocene zone 

of thrusting within the Australian continental margin, although 

subduction cannot be ruled out (Pairault and others, 2003).

Honthaas and others (1999) defined the Ambon Arc as a 

separate arc based on the distinctive geochemistry of Pliocene 

and younger volcanic rocks, the problematic interpretations of 

the Banda Arc as a single arc that requires a single bent subducting slab between Wetar and Ambon (fig. J2), and seismic 

data (McCaffrey, 1988) that support two discrete subduction 

zones: (1) southward subduction of Irian Jaya continental crust 

beneath Seram along the Seram Trough (fig. J2) and (2) northward subduction beneath Wetar.

Banda Arc rocks include geographically distinct geochemical suites in terms of K2

O contents, Sr-Nd-Pb isotopes, 

and oxygen-isotope signatures. These distinct suites are interpreted as indications of variable contributions of subducted 

continental material to depleted MORB-type mantle-derived 

magmas (Vroon and others, 2001) and possibly as indications 

of multiple subduction zones (Whitford and Jezek, 1979).

The Ambon Arc represents two suites of island-arc 

magmas: (1) 5–3.2 Ma, low-K calc-alkaline volcanic rocks 

(basalts, andesites, dacites, rhyolites) evolved from basaltic 

magmatism related to mantle melting above the Western Irian 

Jaya Plate as it subducts along the Seram Trough (north of 

Seram); and (2) 2.3–1 Ma, high-K calc-alkaline andesites, 

dacites, rhyolites, and granites, including cordierite-bearing 

dacites (ambonites) and granites that represent low-K magmas 

that assimilated continental crust. The cordierite-bearing rocks 

on Ambon have high K, Rb, Cs, and 87Sr/86Sr ratios (~0.715) 

that probably reflect a contribution from partial melting of 

pelitic sediments (Whitford and Jezek, 1979). Both low- and 

high-K rocks on Ambelau, Ambon, Kelang Haruku, Saparua, 

and Seram have subduction-type geochemical signatures, such 

as low TiO2 and high Al2O3 mafic lavas, negative Nb anomalies, and high LILE/HFSE and LREE/HFSE ratios (Honthaas 

and others, 1999).

Ambon, Seram, and Kelang are underlain by Paleozoic 

metamorphic basement; Ambelau and Haraku are composed 

entirely of Pliocene and younger andesitic volcanic rocks.

Geologic Criteria

The tract delineates Pliocene to Pleistocene intrusive and 

volcanic rocks (table J2; fig. J3), as shown on a digital geologic map provided by Coordinating Committee for Coastal 

and Offshore Geoscience Programmes in East and Southeast 

Asia (CCOP) and Geological Survey of Japan (1997) and 

Table J2. Map units that define tract 142pCu7201, Ambon Arc, Central Molucca Islands—Indonesia.

[Map unit, geologic-age range, and principal rock types from 1:250,000 scale geologic maps, compiled by the Geological Research and Development Centre, 

Badung, Indonesia, 1987–2000]

Map unit Map symbol Lithology Age range

Intrusive rocks

 Ambon granite Ti(d,g) Biotite granite, biotite cordierite granite, diorite Pliocene to Pleistocene

Volcanic rocks 

Ambelau volcanic rocks Tpav Andesitic lava and pyroclastics Pliocene

Ambon volcanic rocks Tpav Andesite, dacite, breccias, tuff Pliocene to Pleistocene 

Kelang volcanic rocks Tmkv Lava, andesite, breccia, tuff, conglomerate Pliocene to Pleistocene

Andesite (Buru) Tpa Biotite andesite Pliocene
166 Porphyry Copper Assessment of Southeast Asia and Melanesia 

1:250,000-scale geologic maps of the Buru, Ambon, and 

Masohi quadrangles (Tjokrosapoetro and others, 1993a,b,c). 

The cordierite-bearing rocks and granites of the high-K suite 

(Ambon granite) are unlikely associations for porphyry copper mineralization and probably are unrelated. However, no 

detailed geologic maps are available to show the distribution of the two suites, in part because of heavy vegetation, 

steep terrain, complex structure, and difficult access. The 

1:250,000-scale geologic maps show all intrusive rocks as 

Ambon granite. The high-K rocks sampled by Honthaas and 

others (1999) were collected near-shore along the periphery of 

Ambon, Haraku, and Sapura. Low-K samples were collected 

near-shore in southern Seram and eastern Kelang. Exploration 

reports for Ambon Island describe intrusive rocks of intermediate composition, ranging from andesite to granodiorite, 

monzonite, and diorite (Quantitative Resource Assessment 

Team [BPPT], 1997; Menzie and others, 1997). Small areas of 

biotite andesite are mapped on the southern shore of Buru.

The Banda Archipelago represents emerged segments of 

a 5-km-high volcanic structure that includes the recently active 

(1988) Banda Api volcano (fig. J2) in the Ambon Arc segment. Although the lithologies (dacitic and andesitic volcanic 

rocks) are permissive for porphyry associations, volcanic 

centers were excluded from the permissive tract based on the 

thickness of volcanic cover (>1 km) over any possible porphyry copper deposits which may be forming at depth. Ambon 

and nearby islands are transpressive fault blocks that have 

been uplifted and eroded during the Pliocene to Pleistocene. 

Exposed coral reefs rimming the volcanic islands indicate 

rapid uplift (Menzie and others, 1997).

the shoreline to eliminate undersea areas (U.S. Department 

of State, 2009). Permissive areas may be present offshore, 

in areas below ocean level in the Kepulauan Maluku and the 

islands around the city of Ambon; however, assessment protocols limit permissive areas to those above sea level.

Known Deposits

None.

Prospects, Mineral Occurrences, and Related 

Deposit Types

The tract contains the Pliocene-Quaternary Hila porphyry 

copper-gold prospect and associated occurrences (table J3). 

At Hila, chalcopyrite and pyrite are present in veinlets and 

stockworks in Ambon andesites; quartz is the main gangue 

mineral (Menzie and others, 1997). Grab samples of volcanic 

rocks contain as much as 0.014 g/t gold, 530 ppm zinc, and 

1,550 ppm copper (Menzie and others, 1997). The samples 

included altered (sericite, chlorite) porphyritic volcanic rock, 

fine-grained volcanic rock with disseminated pyrite, bleached 

rock with quartz stockworks, and hydrothermal breccia.

Exploration on Ambon Island by Indo Metals in the 

1990s identified 42 showings classified as (1) high-grade polymetallic Cu-Pb-Zn-Ag replacements in breccias and volcanic 

rocks, (2) base-metal quartz veins, and (3) disseminated chalcopyrite in altered diorite intrusions. A cluster of three copper 

prospects identified in a 13 by 7 km area on the northwest 

Table J3. Significant prospects and occurrences in tract 142pCu7201, Ambon Arc, Central Molucca Islands—Indonesia.

[Ma, million years; t, metric ton; g/t, gram per metric ton; Rank 2=drilled or trenched with <20 m of 0.2% Cu or <0.2% Cu, or past or ongoing exploration]

Name Latitude Longitude Age (Ma) Comments Reference Rank

Hila -3.612 128.092 3.6 Porphyry Cu-Au prospect on Ambon 

Island. Grab samples contain ≤0.014 

g/t Au, 530 ppm Zn, 1,550 ppm Cu. 

Age of mineralization is Pliocene or 

younger.

Menzie and others (1997), Indo Metals, Ltd. 

(1997), Whyte (1998), Singer and others 

(2008).

2

Map units were classified into generalized units by age 

and lithologic class (igneous volcanic, igneous plutonic) based 

on map-legend attributes. From this digital database of map 

units grouped by age and lithology, all Tertiary igneous rocks 

were selected. Using GIS tools, a 5-km buffer was applied 

around mapped igneous contacts of permissive lithologies to 

account for spatial uncertainty in digitized geology and for 

the possibility of greater extent of permissive rocks within a 

kilometer of the surface.

The buffered map units were dissolved using GIS processing tools. Finally, the resulting shapefile was clipped to 

coast of Ambon is associated with stream-sediment copper 

anomalies; the Buyang prospect in altered leucodiorite and 

volcanic rocks was considered to represent part of a porphyry 

system (Indo Metals, Ltd., 1997). At the southwestern tip of 

Ambon Island, a 6 by 4.5 km area with copper and gold showings (outcrop, float) was defined (Indo Metals, Ltd., 1997). All 

of the prospects identified were within 6 km of coastal areas; 

the interior of the island was considered equally prospective 

but due to the inaccessible terrain, would require exploration 

with helicopter support. Exploration also identified a 10-kmlong belt of copper showings in northwestern Ambon; these 
Appendix J—Tract 142pCu7201 167

showings include chalcopyrite stringers and disseminations in 

diorite and a soil copper geochemical anomaly over a 700 by 

600 m area (Whyte, 1998).

Exploration suggested that felsic cores of volcanic complexes exhibit copper-dominant porphyry-style mineralization 

flanked by replacements and polymetallic massive sulfides; 

gold tends to be associated with the porphyry-style of mineralization (Whyte, 1998). The Wai Ira polymetallic prospect was 

drilled on Haruku during the 1997–1998 exploration period; 

23 mineral occurrences including porphyry were identified in 

the central part of Haraku.

Exploration History

Sulfide mineral occurrences were discovered by Hila 

villagers in 1992. The Indonesian government and the USGS 

completed a reconnaissance study in 1994 (Menzie and others, 

1997). Consolidated Magna Ventures, Ltd., did reconnaissance 

stream-sediment sampling and prospecting in 1996 to follow 

up copper, gold, and base-metal anomalies detected by P.T. 

Nusa Namorle Mining during their 1987 exploration program. 

Indo Metals, Ltd. (Indo Metals, Ltd., 1997; Whyte, 1998) 

explored Ambon and adjacent islands in 1997 as part of its 

Malaku Joint Venture; the contracts of work (COWs) included 

Haruku, Ambon, Nusa Laut, and Saparua Islands. The lack 

of subsequent exploration and development activity may be 

explained by social, political, and environmental issues that 

have arisen in subsequent years. In 2008, PT Oxindo Exploration and a local Indonesian company established a cooperative 

agreement to explore a number of porphyry copper project 

areas in Ambon (OZ Minerals, Ltd., 2008); however, reports 

on that work were not available.

Sources of Information

Principal sources of information used by the assessment 

team for delineation of the tract are listed in table J4.

Grade and Tonnage Model Selection

Because no well-characterized deposits are present in the 

tract, there is no statistical basis for testing models (table 6). 

In such cases, the default solution is to use a general porphyry 

copper model; however, Hila is described as a copper-gold 

porphyry prospect (Menzie and others, 1997). Chemical 

analyses of three grab samples reported <1 ppm molybdenum, 

and no molybdenite is reported in descriptions of the area. The 

crustal input indicated by the geochemistry of the arc rocks 

and the continental metamorphic basement below Seram support use of a general model that includes all porphyry copper 

subtypes. The magmas that produced the porphyry-related 

rocks have a subduction-related signature. Although contamination by crustal sediments led to the unusual ambonite compositions, the ambonite rocks probably are not associated with 

the copper mineralization. Copper-gold porphyry deposits, 

such as the giant (4.2 Mt contained copper) Batu Hijau deposit 

of Indonesia, are present in the Sunda Arc. The complex 

tectonic setting and classification of Hila as a copper-gold 

prospect were the basis for selecting the copper-gold subtype 

model for the simulation.

Estimate of the Number of Undiscovered Deposits

Rationale for the Estimate

The assessment team considered the Hila porphyry 

copper prospect, the number of mineral occurrences (>30), 

geographically distinct areas characterized by copper and gold 

stream-sediments anomalies, and porphyry-style hydrothermal 

alteration as indications of porphyry systems on Ambon. In 

addition, hidden deposits may be present within 1 km of the 

surface under volcanic cover. The exposed intrusive rocks represent a small portion of the tract area; a cluster of occurrences 

near the Hila gold prospect are controlled by strike-slip and 

duplex faulting (Menzie and others, 1997; Tjokrosapoetro and 

others, 1993a). On the basis of a site visit, Menzie and others 

(1997) suggested that the possible presence of porphyry copper-gold deposits on Ambon merited further study. The central 

part of Ambon is poorly explored. Small bodies mapped as 

Ambon Granite on Manipa and southwestern Seram suggest 

that levels of exposure may be appropriate for preservation of 

porphyry systems.

The small area of permissive rocks is a limiting factor 

on the numbers of deposits that could be present. Exposed 

intrusions in the western part of Ambon Island indicate that 

uplift may have been sufficient to expose porphyry systems 

there. In other parts of the tract, where only volcanic rocks are 

shown on available maps, insufficient uplift and erosion may 

have occurred to bring porphyry deposits to within 1 km of the 

surface.

The team estimated a 50-percent chance of one or more 

undiscovered deposits and a 10-percent chance of two or more 

deposits (table J5). The 5- and 1-percent estimates are also 

two or more deposits, based on the team’s expectations that 

there is insufficient room for additional deposits in the tract. 

The 50-percent estimate is based on the likelihood that, if fully 

explored, the Hila prospect area could represent a deposit like 

those in the grade-and-tonnage model. Based on the number of 

documented copper occurrences and the area under volcanic 

cover, the other estimates are consistent with a general guideline that between 1 and 10 percent of occurrences might be 

mineral deposits consistent with the grade-and-tonnage model 

(Singer and Menzie, 2010). The mean number of deposits for 

this distribution of estimates is 1.0±0.8 with a high coefficient 

of variation of 79 percent, indicating a high degree of uncertainty. Although the tract area is small, given the amount of 

cover and the distribution of permissive rocks on a number 
168 Porphyry Copper Assessment of Southeast Asia and Melanesia 

Table J4. Principal sources of information used for tract 142pCu7201, Ambon Arc, Central Molucca Islands—Indonesia. 

[NA, not applicable; CCOP, Coordinating Committee for Coastal and Offshore Geoscience Programmes in East and Southeast Asia]

Theme Name or Title Scale Citation

Geology Digital geologic map of East and Southeast Asia 1:2,000,000 CCOP and Geological Survey of Japan (1997)

Digital geologic map of Indonesia 1;100,000 Directorate of Mineral Resources and Inventory (2004a)

Geologic map of the Ambon quadrangle, Maluku 1:250,000 Tjokrosapoetro and others (1993c)

Geologic map of the Masohi quadrangle, Maluku 1:250,000 Tjokrosapoetro and others (1993a)

Geologic map of the Buru quadrangle, Maluku 1:250,000 Tjokrosapoetro and others (1993b)

Mineral 

occurrences

Porphyry copper deposits of the world: database, 

map, and grade and tonnage models

NA Singer and others (2008)

Digital mineral occurrence data base NA Directorate of Mineral Resources and Inventory (2004b)

The Hila prospect—a recently discovered occurrence 

on Ambon Island, Republic of Indonesia

NA Menzie and others (1997)

Exploration Indo Metals Ltd. announces 42 new base metalsilver-gold showings discovered on the Maluku Joint 

Venture’s Ambon Island property

NA Indo Metals, Ltd. (1997)

Base Metals—Maluku base metal project a 

prospecting triumph

NA Whyte (1998)

Table J5. Undiscovered deposit estimates, deposit numbers, tract area, and deposit density for tract 142pCu7201, Ambon Arc, Central 

Molucca Islands—Indonesia.

[NXX, estimated number of deposits associated with the xxth percentile; Nund, expected number of undiscovered deposits; s, standard deviation; Cv%, coefficient of 

variance; Nknown, number of known deposits in the tract that are included in the grade and tonnage model; Ntotal, total of expected number of deposits plus known 

deposits; km2, area of permissive tract in square kilometers; Ntotal/100k km2, deposit density reported as the total number of deposits per 100,000 km2. Nund, s, and 

Cv% are calculated using a regression equation (Singer and Menzie, 2005). In cases where individual estimates were tallied in addition to the consensus estimate, 

individual estimates are listed.

 Consensus undiscovered 

 deposit estimates Summary statistics Tract area 

(km2

)

Deposit density 

(Ntotal/100k km2)

N90 N50 N10 N05 N01 Nund s Cv% Nknown Ntotal

0 1 2 2 2 1 0.79 79 0 1 1,540 65
Appendix J—Tract 142pCu7201 169

Table J6. Results of Monte Carlo simulations of undiscovered resources for tract 142pCu7201, Ambon Arc, Central Molucca Islands—

Indonesia.

[Cu, copper; Mo, molybdenum; Au, gold; and Ag, silver; in metric tons; Rock, in million metric tons]

Material

Probability of at least the indicated amount Probability of

0.95 0.9 0.5 0.1 0.05 Mean Mean or 

greater

None

Cu 0 0 660,000 6,700,000 13,000,000 3,100,000 0.21 0.3

Mo 0 0 0 32,000 73,000 18,000 0.14 0.69

Au 0 0 65 560 1,000 230 0.23 0.3

Ag 0 0 0 1,700 3,400 1,000 0.15 0.6

Rock 0 0 150 1,300 2,900 620 0.22 0.3

of islands there could be two or more deposits, albeit at a low 

probability of occurrence. The small size of the tract area (1,540 

km2) results in a high apparent deposit density (table J5).

Probabilistic Assessment Simulation 

Results

Undiscovered resources for the tract were estimated by 

combining consensus estimates for numbers of undiscovered 

porphyry copper deposits with the porphyry copper-gold subype model of Singer and others (2008), using the EMINERS 

program (Root and others, 1992; Bawiec and Spanski, 2012; 

Duval, 2012). Selected simulation results are reported in table 

J6. Results of the Monte Carlo simulations are presented as a 

cumulative frequency plot (fig. J4). The cumulative frequency 

plot shows the estimated amounts of resource associated with 

cumulative probabilities of occurrence, as well as the mean, 

for each commodity and for total mineralized rock.

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a prospecting triumph: The Northern Miner, June 29, 1998.
Figure J1. Map showing tract location and significant porphyry copper prospects for tract 142pCu7201, Ambon Arc, Central Molucca Islands—

MY, Malaysia; PH, Philippines; PG, Papua New Guinea.

126° E 128° E 130° E

2° S4° S

INDONESIA

Nusa Luat Island

Ambelau Island

Ambon Island

Kelang Island

Manipa Island

Hila

Buru Island Haraku Island Saparua Island

Seram Island

Banda Sea

Molucca Sea

Seram Sea

120°E 

20°N

0°

20°S

ID

MY

Political boundary source: U.S. Department of State (2009)Projection: Asia South Albers Equal Area Conic;Central meridian 127° E; latitude of origin 15° S

0 25 50 75 100 KILOMETERS

0 25 50 MILES

EX

OtheAsse142pPorp
BANDA ARCHIPELAGO 120° E 125° E 130° E 0° 5° S

(

(

( ( (

(

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BANDA

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Bird’s

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Halmahera

TIMOR TROUGH

SORONG FAULT

SERAM TROUGH

SERAM TROUGH

SUNDA-BANDA ARC

JAVA TRENCH

Flores Sea

A

MBO

N

ARC

Arafura Sea

Base source: National Oceanic and Atmospheric Administration (2009)ETOPO1 1 Arc-Minute Global Relief ModelPolitical boundary source: U.S. Department of State (2009)Projection: Asia South Albers Equal Area Conic;Central meridian 128° E; latitude of origin 15° S

0 100 200 300 400 KILOMETERS

0 100 200 MILES

#* 

( ( 

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!(

EX

Figure J2. Map showing the regional setting for tract 142pCu7201, Ambon Arc, Central Molucca Islands—Indonesia.
Seram Sea

Banda Sea

( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( (

INDONESIA

INDONESIA

Hila

128° E

4° S

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0 25 50 75 100 KILOMETERS

0 25 50 MILES

E

As 1PoPePeEu

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Figure J3. Map showing the distribution of permissive igneous rocks, tectonic features, and porphyry copper deposits and prospects for tract 1

Central Molucca Islands—Indonesia.
174 Porphyry Copper Assessment of Southeast Asia and Melanesia 

1.00

0.90

0.80

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

Probability

0.01 0.1 1 10 100 1k 10k 100k 1M 10M 100M 1B 10B 100B

Material, in metric tons

Mean Cu Mean Rock

Mean Ag

Mean Mo

Mean Au

Cu

Mo

Au

Ag

Rock

Mean Cu

Mean Mo

Mean Au

Mean Ag

Mean Rock

EXPLANATION

Figure J4. Cumulative frequency plot showing the results of Monte Carlo computer simulation of undiscovered 

resources in tract 142pCu7201, Ambon Arc, Central Molucca Islands—Indonesia. k, thousands; M, millions; B, billions; 

Tr, trillions.
Appendix K—Tract 142pCu7202 175

Appendix K. Porphyry Copper Assessment for Tract 142pCu7202, 

Halmahera Arc, North Molucca Islands—Indonesia

By Jane M. Hammarstrom1, Bambang Tjahjono Setiabudi2, Dwi Nugrono Sunuhadi2, Gilpin R. Robinson, Jr.1, 

Connie L. Dicken1

, Steve Ludington3, Arthur A. Bookstrom4, and Michael L. Zientek4, with contributions from 

Gwaibo Kopi5

 and Dennis P. Cox3

Deposit Type Assessed: Porphyry copper, copper-gold subtype

Descriptive model: Porphyry copper (Berger and others, 2008; John and others, 2010); Porphyry copper-gold (Cox, 

1986; Cooke and others, 1998)

Grade and tonnage models: Porphyry copper, copper-gold subtype (Singer and others, 2008)

Table K1 summarizes selected assessment results.

Table K1. Summary of selected resource assessment results for tract 142pCu7202, Halmahera Arc—North Molucca Islands, Indonesia. 

[km, kilometers; km2, square kilometers; t, metric tons]

Date of 

assessment

Assessment depth 

(km)

Tract area 

(km2)

Known copper 

resources (t)

Mean estimate of 

undiscovered copper 

resources (t)

Median estimate of 

undiscovered copper 

resources (t)

February 2010 1 12,250 254,100 4,800,000 870,000

1

U.S. Geological Survey, Reston, Virginia, United States.

2

Center for Geological Resources, Geological Agency of Indonesia, West Java, Indonesia.

3

U.S. Geological Survey, Menlo Park, California, United States.

4

U.S Geological Survey, Spokane, Washington, United States.

5

Mineral Resources Authority, Papua New Guinea.

Location

The tract includes islands of North Maluku Province (Maluku Utara), Indonesia (fig. K1).

Geologic Feature Assessed

Neogene Halmahera island arc.

Delineation of the Permissive Tract

Tectonic Setting

The tract was delineated for Neogene igneous rocks of the Halmahera Arc along the western parts of Morotai and Halmahera Islands, Bacan Island, Obi Island, and several smaller islands of the North Moluccas in the Indonesian Province of North 
176 Porphyry Copper Assessment of Southeast Asia and Melanesia 

Maluku (fig. K1). The 400-km-long, approximately northsouth, Neogene to Holocene Halmahera magmatic arc extends 

from the western splay of the Sorong Fault at Obi Island in 

southwestern Halmahera, through Bacan Island and western 

Halmahera, to an area near the Philippine Trench north of the 

island of Morotai (fig. K2). Basement rocks for the Neogene 

arc in western Halmahera include Mesozoic or Tertiary volcanic rocks. The northeastern part of Halmahera Island lies on a 

basement of Cretaceous to Paleocene ophiolitic oceanic crust. 

After collision with the northern Australian margin at about 22 

Ma and a period of quiescence, late Miocene to Pliocene magmatism related to east-dipping subduction of the Molucca Sea 

Plate migrated from south to north. The Molucca Sea Plate 

is almost entirely consumed by eastward subduction beneath 

the Halmahera Arc fragment of the Philippine Sea Plate and 

westward subduction beneath the Sangihe Arc of eastern Indonesia (Widiwijayanti and others, 2004). The collision zone at 

the convergence of the Halmahera and Sangihe Arcs marks the 

southern terminus of the Philippine mobile belt.

Geologic Criteria

Neogene arc rocks include diorite to granodiorite intrusions and andesites, with geochemical signatures indicating 

contributions of continental crust attributed to underlying 

Australian continental crust displaced along the Sorong Fault 

(Garwin and others, 2005). The northern, intraoceanic part of 

the arc has active volcanoes. The Neogene volcanic rocks are 

medium-to-high-K calc-alkaline two-pyroxene andesites and 

hornblende-bearing andesites with REE patterns and niobium 

depletion trends that are characteristic of West Pacific volcanic 

arcs (Hakim and Hall, 1991). The Bacan segment of the arc 

hosts dacites with continental trace-element signatures, as well 

as Quaternary basalts and andesites with oceanic affinities 

(Palmer, 1991). The oldest Neogene arc rocks (~11 Ma) are on 

Obi Island (MacPherson and others, 2003). The Neogene arc 

was produced by a mantle wedge that may have varied in the 

amount of prior melt extraction (depletion) along the length of 

the arc, and been metasomatized by fluids released from dehydration of subducted sediment and oceanic crust (MacPherson 

and others, 2003; Palmer 1991).

The tract was constructed in a GIS using 1:250,000-scale 

geologic maps of the Morotai, Ternate, and Bacan quadrangles, Indonesia; a 1:500,000-scale digital map of igneous 

rocks of Indonesia (Setiabudi, written commun., 2005); and 

geologic sketch maps included in Gemmell (2007). Map units 

were classified into generalized units by age and lithologic 

class (igneous volcanic, igneous plutonic). From this digital 

database of geologic lithology and age attributes, Tertiary and 

Neogene (Oligocene-Miocene and Miocene-Pliocene) igneous rocks were selected (fig. K2). A 5-km buffer was applied 

around mapped intrusive-rock contacts, with a 2-km buffer 

around volcanic-rock contacts of these permissive lithologies; 

areas around Quaternary volcanoes where volcanic cover is 

likely to exceed 1 km were excluded.

The tract is based on map units listed in table K2. The 

main geologic units in the tract are andesites, breccias, and 

tuffs; these are interbedded with, and overlain by clastic 

sedimentary rocks and limestone. Small intrusive bodies of 

granite and granodiorite are mapped on Bacan Island (Bacan 

1:250,000-scale geologic map), and small bodies of diorite 

and andesite are scattered through Tertiary and Quaternary 

andesitic volcanic units mapped in the Morotai and Ternate 

quadrangles. Locally, volcanic rocks are fractured and contain 

pyrite-bearing quartz veinlets (Apandi and Sudana, 1980). 

A database of isotopic ages of igneous rocks for Indonesia 

compiled by the Southeast Asia Research Group (SEARG) 

showed locations, ages, and lithologies for sample sites and 

provided additional controls on distributions of permissive 

rocks (Malaihollo and others, 2002). The age of the tonalite 

Table K2. Map units that define tract 142pCu7202, Halmahera Arc, North Molucca Islands—Indonesia. 

[Map unit, age range, and principal lithologies are based 1:250,000 scale geologic maps of North Maluku, Indonesia]

Map unit Map symbol Lithology Age range

Intrusive rocks

Intrusive rocks gd Granodiorite Late Oligocene

Volcanic rocks

Andesite An Andesite Holocene

Bacan Formation Tomb Andesite, volcanic breccia, lavas, tuffs, intercalations of conglomerate and 

sandstone

Late Oligocene

Obit Formation Tmpo Volcanic breccia and sandy tuff Pliocene
Appendix K—Tract 142pCu7202 177

associated with the Kaputusan porphyry copper deposit is 

unknown. Garwin and others (2005) described Kaputusan as 

a prospect associated with a Neogene quartz diorite intrusion 

in pre-Miocene volcanic host rocks. The SEARG database 

includes 28 isotopic age determinations on igneous rocks in 

the Bacan area of the Halmahera Arc; K-Ar ages (whole rock, 

biotite, hornblende) range from 21 to 1 Ma and include intermediate volcanic rocks (hornblende and pyroxene andesites) 

and intrusive rocks (quartz diorite, quartz monzodiorite). The 

age of the Gosowong intermediate-sulfidation epithermal system on Halmahera Island is 2.4–2.9 Ma (Olberg and others, 

1999). De Waele and others (2009) suggest that the known 

mineral deposits in the North Moluccas, the Gosowong (Kencana mine) epithermal gold-silver deposit, and the undated 

Kaputusan porphyry copper-gold deposit formed in response 

to the end of eastward subduction and beginning of westward 

subduction in the Halmahera Arc. Dated rock samples include 

late Oligocene to early Miocene (29–23 Ma) feldspar porphyry and andesite at the northern end of the arc on Halmahera and Morotoi. Cretaceous and Neogene rocks are exposed 

at the southern end of the arc on Obi Island between strands 

of the Sorong Fault; Cretaceous rocks are excluded from the 

tract.

A polygon aggregation and smoothing process was 

applied to the revised buffered permissive geologic map 

units to produce a preliminary permissive tract. The processing approximates manual delineation of a tract but is rapid 

and reproducible. The processing steps include (1) unioning all permissive unit buffers and other polygon features 

that comprise the framework of the tract, (2) aggregating 

unioned polygons using an aggregation distance of 50 km 

and a minimum hole size of 2,000 km2

, (3) simplifying the 

aggregated polygons using a bend-simplify algorithm with a 

simplification tolerance of 5 km, and (4) line-smoothing the 

simplified polygons using an algorithm (PAEK, polynomial 

approximation with exponential kernel)with a tolerance of 20 

km. Necking, thinning, and contraction of the polygons resulting from processing required a subsequent manual cleaning 

step (for example, to remove polygon necks). Resulting tract 

boundaries were compared to the permissive geologic features 

in source materials to ensure that original permissive boundaries were honored. Regional and local mineral occurrence, 

geochemical, and isotopic-age data were plotted and used 

to constrain or expand tract boundaries. All operations were 

carried out in ArcGIS 9.3 using standard tools available in the 

Arc Toolbox.

These revised preliminary-tract polygons were further 

modified by comparison with the scanned and rectified 

geologic maps to exclude areas where Quaternary volcanic 

rocks or sedimentary deposits are greater than 1 km in 

thickness. The final tract boundary was clipped to the 

shoreline to eliminate undersea areas (U.S. Department of 

State, 2009).

The Halmahera tract contains a nature reserve (Gunung 

Sibela) and production forests, which may present a potential 

for land-use conflicts for exploration and development.

Known Deposits

The Kaputusan porphyry copper-gold deposit on 

Bacan Island contains identified resources of 77 Mt at 0.33 

percent copper and 0.25 g/t gold (table K3). The deposit was 

discovered and drilled during a regional joint IndonesianGerman exploration program done from 1977 to 1979; 

additional trenching and drilling occurred in 1983 and 1984 

(Asia Gold, 2006, 2007). The best reported drill intercepts 

(<200 m depth in 10 vertical holes) are 48 m at 0.37 percent 

copper and 0.65 g/t gold and 153 m at 0.33 percent copper and 

0.28 g/t gold. Higher copper- and gold-grade intercepts were 

encountered in trenches.

Table K3. Identified porphyry copper resources in tract 142pCu7202, Halmahera Arc, North Molucca Islands—Indonesia. 

[Ma, million years; Mt, million metric tons; t, metric ton; %, percent; g/t, gram per metric ton; Cu-Mo subtype, deposits that have Au/Mo ratios <3 or average Mo 

grades >0.03%; Cu-Au subtype, deposits that have Au/Mo ratios >30 or average Au grades >0.2 g/t. Contained Cu in metric tons is computed as tonnage (Mt ×

1,000,000) × Cu grade (percent); n.d., no data]

Name Latitude Longitude Subtype Age 

(Ma)

Tonnage 

(Mt)

Cu

(%)

Mo

(%)

Au

(g/t)

Ag

(g/t)

Contained

Cu (t) Reference

Kaputusan -0.517 127.583 Cu-Au n.d. 77 0.33 n.d. 0.25 n.d. 254,100 Asia Gold (2006), 

Carlile and 

others (1998), 

Djaswadi (1993), 

Pudjowalujo and 

Bering (1982), van 

Leeuwen (1994) 
178 Porphyry Copper Assessment of Southeast Asia and Melanesia 

In 2006, the exploration lease was converted to exploration status and split into two blocks (13,641 ha and 133,770 

ha), and an additional lease area expanded the total area under 

exploration to 37,661 ha (South Gobi Energy Resources, 

2007). Six diamond drill holes (<200 m depth) all intersected 

porphyry copper-gold mineralization, but technical problems 

thwarted completion of drilling. North Zone exploration 

results showed a 152 m section of 0.20 percent copper and 

0.16 g/t gold; South Zone results included a 34 m section of 

0.14 percent copper and 0.15 g/t gold.

Three mineralized zones (North, West, and South) are 

associated with altered (potassic; sericite-clay-chlorite), magnetite-bearing, tonalite porphyry stocks and tonalite porphyry 

dikes that intrude andesitic volcanic rocks. The stocks extend 

over an area of approximately 1,300 by 500 m. Exploration in 

2006–2007 confirmed a 1.8 km-long-extent of mineralization 

along a north-south trend; the deposit is considered open along 

the trend (South Gobi Energy Resources, 2007).

Ore minerals include bornite, chalcopyrite, and gold. 

Supergene ore minerals include covellite, chrysocolla, malachite, and cuprite/tenorite (Pudjowalujo and Bering, 1982; van 

Leeuwen, 1994). A gold-rich (0.44 g/t gold) leached cap is 

present in the southern part of the deposit area. Biotite, sericite, chlorite, kaolinite, smectite, magnetite, gypsum, and hematite are present as alteration minerals. van Leeuwen (1994) 

reported a positive correlation between grade and intensity 

of quartz stockworks and noted that locally, fault-controlled 

quartz-sericite alteration overprints the deposit.

Prospects, Mineral Occurrences, and Related 

Deposit Types

Mineral occurrences west of the Kaputusan deposit include 

Masurung I and II, on Maluku, which are thought to be related 

to gold-copper porphyry systems. Five other copper occurrences 

also lie to the north and south of Kaputusan (Directorate of Mineral Resources and Inventory, 2004b; Garwin and others, 2005). 

Four low-grade porphyry copper-gold prospects are associated 

with the Pliocene (2.4–2.9 Ma) Gosowong quartz- adularia epithermal gold deposit in the northern part of the tract on Halmahera (Carlile and others, 1998; Gemmell, 2007). Seven partially 

explored prospects are included in the Indonesian database 

(Directorate of Mineral Resources and Inventory, 2004b); the 

deposit type for most of these is uncertain. Sites with reported 

copper are included in table K4 to illustrate the distribution of 

copper throughout the tract area. Note that these were considered uneconomic, reported grades are very low, and a number of 

prospects are closely spaced (within 2 km) which indicates that 

they may represent parts of the same system.

Exploration History

The Halmahera region initially was explored for porphyry copper deposits as part of an Indonesian-German 

program based on recognition of a possible link between 

the porphyry copper settings of Papua New Guinea and the 

Philippines (van Leeuwen, 1994). Stream-sediment and soil 

sampling identified the mineralization at Kaputusan. Exploration in the North Moluccas tract took place at the Kaputusan 

porphyry copper-gold deposit between 1981 and 1985 after the 

discovery of the deposit in 1979. The Indonesian Directorate 

of Mineral Resources did regional- and district- scale geochemical exploration for gold deposits. A project to characterize the Bora porphyry copper-gold prospect in the Gosowong 

district recently was announced (CODES, 2009).

Sources of Information

Principal sources of information used by the assessment 

team for tract 142pCu7202 are listed in table K5.

Grade and Tonnage Model Selection

The only known deposit in the tract, Kaputusan, is a 

porphyry copper-gold deposit (0.25 g/t gold). Molybdenum is 

reported (van Leeuwen, 1994), but no grade is available. Statistical tests (ANOVA) for Kaputusan against the global general and Cu-Au subtype models support use of either model 

(table 6). The team selected the porphyry copper-gold model, 

based on classification of Kaputusan and the description of 

low-grade copper-gold porphyries in the Gosowong district.

Estimate of the Number of Undiscovered Deposits

Rationale for the Estimate

The assessment team considered the distribution of permissive rocks within the tract; the presence of one confirmed porphyry copper-gold deposit at Kaputusan; additional occurrences 

of copper and gold; and the possibility that, if fully explored, 

the porphyry prospects in the Gosowong district could represent 

one or more deposits like those included in the grade and tonnage model. Molybdenite, bornite, chalcopyrite, and pyrite are 

reported in the map unit descriptions for intrusive rocks in the 

Bacan 1:250,000-scale quadrangle, some of which intrude the 

extensive Bacan Formation which is propylitized in some areas 

(Yasin, 1980). Blocks of silicified tuff in the Ternate quadrangle 

contain malachite and azurite (Apandi and Sudani, 1980). These 

observations suggest that additional porphyry systems may be 

concealed beneath volcanic cover rocks. On the basis of this 

information, the team estimated a 50-percent chance that the 

tract may contain one or more undiscovered deposits, a 10-percent chance of three or more deposits, and a 5-percent chance 

of six or more deposits (table K6). The high standard deviation (±1.5) and coefficient of variation (110 percent) reflect the 

team’s uncertainty about the potential of the tract.
Appendix K—Tract 142pCu7202 179

Table K4. Significant prospects and occurrences in tract 142pCu7202, Halmahera Arc, North Molucca Islands—Indonesia. 

[*,Tobobo, Matat, and Ngoali are located ~ 2, 6, and 9 kilometers (km) north of the Bora porphyry, respectively. These four areas may all represent one porphyry 

system. The other groups include prospects within 2 km of each other, which may represent parts of single systems. Rank 4=prospect in global database of 

Singer and others (2008) or <16,000 t contained copper; Rank 3=drilled, with >20 m of 0.2% or more Cu. Rank 2=drilled or trenched with <20 m of 0.2% Cu, or 

<0.2% Cu, or past or ongoing exploration. Rank 1=copper occurrence that may be related to porphyry-type mineralization based on stream-sediment or magnetic 

anomaly, or location along structural trend. n.d., no data; %, percent; t, metric tons; Mt, million metric tons]

Name Latitude Longitude Age (Ma) Comments Reference Rank

Payahe 0.332 127.751 n.d. Copper veinlets; 46,800 t (measurable); 

0.20% Cu.

Directorate of Mineral 

Resources and Inventory 

(2004b)

1

 Bora Group

Tobobo and Bora* 1.137 127.677 n.d. Low-grade porphyry Cu-Au center 

of mineralization associated with 

porphyritic quartz diorite 2.5 km WNW 

of the Gosowong epithermal deposit 

in the Gosowong district (reportedly 

subeconomic). Location for Toboba; Bora 

<0.5 km west of Toboba.

Carlile and others (1998), 

Gemmell (2007)

2

Matat and Ngoali* 1.188 127.690 n.d. Gosowong area. Porphyry stock within 

argillically-altered Miocene volcanics 

~2 km due north of the Gosowong vein 

(reportedly subeconomic). Matat porphyry 

is located ~6 km NE of the Bora-Tobobo 

area; Ngoali is ~ 3 km NW of Matat. 

Location plotted for Matat. 

Gemmell (2007) 2

 Masurung Group

Masurung I (Kaputusan 

Selatan I)

-0.463 127.403 n.d. Inactive Cu-Au porphyry prospect 

associated with tonalite. 

Directorate of Mineral 

Resources and Inventory 

(2004b)

1

Masurung II -0.458 127.403 n.d. Inactive Cu-Au porphyry prospect 

associated with tonalite. 

D.N. Sunuhadi (written 

commun., 2004)

1

Sugili (Kaputusan 

Utara)

-0.470 127.406 n.d. Inactive Cu-Au porphyry prospect 

associated with tonalite. Alteration: 

argillic, biotite, epidote, potassic, 

propylitic, phyllic.

D.N. Sunuhadi (written 

commun., 2004)

1

 Hulu Group

Hulu S -0.551 127.399 n.d. Hydrothermal, 100 Mt (measurable); 

0.3% Cu.

Directorate of Mineral 

Resources and Inventory 

(2004b)

4

 Kapatusan P. Bacan -0.554 127.394 n.d. Hydrothermal, 70 Mt, 0.3% Cu. Directorate of Mineral 

Resources and Inventory 

(2004b) 4
180 Porphyry Copper Assessment of Southeast Asia and Melanesia

Table K5. Principal sources of information used for tract 142pCu7202, Halmahera Arc, North Molucca Islands—Indonesia. 

[NA, not applicable]

Theme Name or title Scale Citation

Geology Digital geologic map of East and Southeast Asia 1:2,000,000 Geological Survey of Japan (1997)

Digital geologic map of Indonesia 1;100,000 Directorate of Mineral Resources and Inventory (2004a)

Geologic map of the Ternate Quadrangle, North Maluku 1:250,000 Apandi and Sudana (1980)

Geologic map of the Morotai Quadrangle, North 

Maluku

1:250,000 Supriatna (1980)

Geologic map of the Bacan Quadrangle, North Maluku 1:250,000 Yasin (1980)

SE Asia Radiometric Ages: GIS database NA Malaihollo and others (2002)

Mineral 

occurrences

Porphyry copper deposits of the world: database, map, 

and grade and tonnage models

NA Singer and others (2008)

Digital mineral occurrence data base NA Directorate of Mineral Resources and Inventory (2004b)

Exploration 25 Years of mineral exploration and discovery in 

Indonesia

NA van Leeuwen (1994)

Mining company Web sites NA Asia Gold (2006, 2007)

 Consensus undiscovered deposit estimates Summary statistics Tract area 

(km2

)

Deposit density 

(Ntotal/100k km2) N90 N50 N10 N05 N01 Nund s Cv% Nknown Ntotal

0 1 3 6 6 1.5 1.8 110 1 2.5 12,250 20

Table K7. Results of Monte Carlo simulations of undiscovered resources for tract 142pCu7202, Halmahera Arc, North Molucca 

Islands—Indonesia. 

[Cu, copper; Mo, molybdenum; Au, gold; and Ag, silver; in metric tons; Rock, in million metric tons]

Material

Probability of at least the indicated amount Probability of

0.95 0.9 0.5 0.1 0.05 Mean Mean or 

greater

None

Cu 0 0 870,000 12,000,000 24,000,000 4,800,000 0.22 0.31

Mo 0 0 0 58,000 140,000 29,000 0.16 0.63

Au 0 0 80 930 1,700 340 0.25 0.31

Ag 0 0 0 3,000 7,000 1,600 0.16 0.56

Rock 0 0 210 2,600 4,800 970 0.24 0.31

Table K6. Undiscovered deposit estimates, deposit numbers, tract area, and deposit density for tract 142pCu7202, Halmahera Arc, 

North Molucca Islands—Indonesia. 

[NXX, estimated number of deposits associated with the xxth percentile; Nund, expected number of undiscovered deposits; s, standard deviation; Cv%, coefficient 

of variance; Nknown, number of known deposits in the tract that are included in the grade and tonnage model; Ntotal, total of expected number of deposits plus 

known deposits; km2, area of permissive tract in square kilometers; Ntotal/100k km2, deposit density reported as the total number of deposits per 100,000 km2. 

Nund, s, and Cv% are calculated using a regression equation (Singer and Menzie, 2005)]
Appendix K—Tract 142pCu7202 181

Probabilistic Assessment Simulation 

Results

Undiscovered resources for the North Moluccas permissive tract 142pCu7202 were estimated by combining consensus estimates for numbers of undiscovered porphyry copper 

deposits with the porphyry copper-gold grade and tonnage 

model of Singer and others (2008) using the EMINERS 

program (Root and others, 1992; Bawiec and Spanski, 2012; 

Duval, 2012). Selected output parameters are reported in table 

K7. Results of the Monte Carlo simulation are presented as a 

cumulative frequency plot (fig. K3). The cumulative frequency 

plot shows the amounts of estimated resources associated with 

cumulative probabilities of occurrence, as well as the mean, 

for each commodity and for total mineralized rock. Median 

(870,000 t copper) and mean (4.8 Mt copper) copper resources 

that could be associated with undiscovered deposits in the tract 

greatly exceed the identified resource at Kaputusan (254,100 t 

copper).

References Cited

Apandi, T., and Sudana, D., 1980, Geologic map of the Ternate 

quadrangle, North Maluku, and accompanying pamphlet: 

Indonesia, Geological Research and Development Centre, 

scale 1:250,000.

Asia Gold, 2006, Asia Gold discovers a new zone of mineralization on the Kaputusan porphyry copper-gold prospect: Asia Gold News Release, December 13, 2006, 5 p., 

accessed May 15, 2010, at http://www.southgobi.com/i/

pdf/12_13_2006_NR.pdf.

Asia Gold, 2007, Trench results continue to expand the 

Kaputusan porphyry copper-gold prospect, Bacan Island, 

Maluku, Indonesia: Asia Gold New Release, January 

29, 2007, 3 p., accessed May 15, 2010, at http://www.

marketwire.com/press-release/Asia-Gold-Corp-TrenchResults-Continue-Expand-Kaputusan-Porphyry-CopperGold-Prospect-TSX-VENTURE-ASG-632832.htm.

Bawiec, W.J., and Spanski, G.T., 2012, Quick-start guide for 

version 3.0 of EMINERS—Economic Mineral Resource 

Simulator: U.S. Geological Survey Open-File Report 

2009–1057, 26 p., accessed June 30, 2012, at http://pubs.

usgs.gov/of/2009/1057. (This report supplements USGS 

OFR 2004–1344.)

Berger, B.R., Ayuso, R.A., Wynn, J.C., and Seal, R.R., 

2008, Preliminary model of porphyry copper deposits: 

U.S. Geological Survey Open-File Report 2008–1321, 

55 p., accessed May 15, 2010, at http://pubs.usgs.gov/

of/2008/1321.

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Rafferty, W.J., 1998, Discovery and exploration of the 

Gosowong epithermal gold deposit, Halmahera, Indonesia: 

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1, 2010, at http://www.codes.utas.edu.au/files/Ore%20

Sols%2024.pdf.

Cooke, D.R., Heithersay, P.S., Wolfe, R., and Calderon, A.L., 

1998, Australian and western Pacific porphyry Cu-Au 

deposits: Journal of Australian Geology and Geophysics, 

v. 17, no. 4, p. 97–104.

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(Model 20c), in Cox, D.P., and Singer, D.A., eds., 1986, 

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1693, p. 110. (Also available online at http://pubs.usgs.gov/

bul/b1693/.)

De Waele, Bert, Williams, P., and Chan. G., 2009, Tectonic 

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Garwin, S., Hall, R., and Watanabe, Y., 2005, Tectonic setting, 

geology, and gold and copper mineralization in Cenozoic 

magmatic arcs of southeast Asia and the west Pacific, in 

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with the Gosowong epithermal Au-Ag deposit, Halmahera, 

Indonesia—Mineralogy, geochemistry, and exploration 

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Indonesia, in Larter, R.D., and Leat, P.T., eds., Intra-oceanic 

subduction systems—Tectonic and magmatic processes: 

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of IAMG—The annual conference of the International 

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1028–1033.

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scale 1:250,000.

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international land boundaries (SSIB)—Lines, edition 10, 

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system: Reston, Virginia, U.S. Geological Survey, accessed 

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discovery in Indonesia, in van Leeuwen, T.M., Hedenquist, 

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deposits—Discoveries of the past 25 years: Journal of 

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203–222.

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1:250,000.
Appendix K—Tract 142pCu7202 183

128° E

2° N

Kaputusan Hulu S

Kaputusan, P.Bacan

Masurung II

Matat, Ngoali

Payahe

Sugili (Kaputusan Utara)

Tobobo, Bora

Masurung I (Kaputusan Selatan I)

INDONESIA

Halmahera Island

Bacan Island

Obi Island

Morotai Island

Molucca Sea

Halmahera Sea

Seram Sea

120°E 130°E 140°E

20°N

0°

20°S

INDIAN OCEAN

PACIFC OCEAN

AUSTRALIA

ID

PG

PH

CN

ID

MY

Political boundary source: U.S. Department of State (2009)

Projection: Asia South Albers Equal Area Conic;

Central meridian 128° E; latitude of origin 15° S

0 15 30 45 60 KILOMETERS

0 15 30 MILES

EXPLANATION

Assessed porphyry copper tract

142pCu7202

Other porphyry copper tracts

Porphyry copper deposit

Porphyry copper prospect

Area of Map

Figure K1. Map showing tract location, known deposits, and significant porphyry copper prospects for tract 

142pCu7202, Halmahera Arc, North Molucca Islands—Indonesia. CN, China; ID, Indonesia; MY, Malaysia; PH, Philippines; 

PG, Papua New Guinea.
184 Porphyry Copper Assessment of Southeast Asia and Melanesia

( ( (

(

(

( ( ( ( ( ( ( ( ( ( 

( ( ( ( ( ( ( ( (

Molucca Sea

Halmahera Sea

Seram Sea

INDONESIA

Kaputusan Hulu S

Kaputusan, P. Bacan

Masurung II

Matat, Ngoali

Payahe

Sugili (Kaputusan Utara)

Tobobo, Bora

Masurung I (Kaputusan Selatan I)

128° E

2° N

0°

Base from ESRI ArcGIS Online (2009)

World Shaded Relief

Political boundary source: U.S. Department of State (2009)

Projection: Asia South Albers Equal Area Conic;

Central meridian 128° E; latitude of origin 15° S

0 25 50 75 100 KILOMETERS

0 25 50 MILES

EXPLANATION

Assessed porphyry copper tract

 142pCu7202

Permissive intrusive rocks

Porphyry copper prospect

Permissive volcanic rocks

Australian continental Crust

(

Strike-slip fault

Thrust fault

Porphyry copper deposit

Figure K2. Map showing the distribution of permissive igneous rocks and porphyry copper deposits and prospects for 

tract 142pCu7202, Halmahera Arc, North Molucca Islands—Indonesia.
Appendix K—Tract 142pCu7202 185

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

Probability

Material, in metric tons

0.01 0.1 1 10 100 1k 10k 100k 1M 10M 100M 1B 10B 100B

Mean Cu

Mean Mo

Mean Au

Mean Ag

Mean Rock

Cu

Mo

Au

Ag

Rock

Mean Cu

Mean Mo

Mean Au

Mean Ag

Mean Rock

EXPLANATION

Figure K3. Cumulative frequency plot showing the results of Monte Carlo computer simulation of undiscovered resources in tract 

142pCu7202, Halmahera Arc, North Molucca Islands—Indonesia. k, thousands; M, millions; B, billions; Tr, trillions.
186 Porphyry Copper Assessment of Southeast Asia and Melanesia

Appendix L. Porphyry Copper Assessment for Tract 142pCu7205, 

Moon-Utawa-Ular Merah Areas—Indonesia

By Jane M. Hammarstrom1, Bambang Tjahjono Setiabudi2, Dwi Nugrono Sunuhadi2, Gilpin R. Robinson, Jr.1, 

Connie L. Dicken1

, Steve Ludington3, Arthur A. Bookstrom4, and Michael L. Zientek4, with contributions from 

Gwaibo Kopi5

 and Dennis P. Cox3

Deposit Type Assessed: Porphyry copper, copper-gold subtype

Descriptive model: Porphyry copper (Berger and others, 2008; John and others, 2010); Porphyry copper-gold 

(Cox, 1986; Cooke and others, 1998)

Grade and tonnage models: Porphyry copper, copper-gold subtype (Singer and others, 2008)

Table L1 summarizes selected assessment results.

Table L1. Summary of selected resource assessment results for tract 142pCu7205, Moon-Utawa-Ular Merah Areas—Indonesia.

[km, kilometers; km2, square kilometers; t, metric tons; n.d., no data] 

Date of assessment Assessment depth 

(km)

Tract area 

(km2)

Known copper 

resources (t)

Mean estimate of 

undiscovered copper 

resources (t)

Median estimate of

undiscovered copper

resources (t)

February 2010 1 13,580 n.d. 3,200,000 660,000

Location

The tract includes the Bird’s Head and Bird’s Neck areas of West Papua Province, as well as the Ular Merah area of the 

western Central Range of Papua Province (Irian Jaya), Indonesia (fig. L1).

Geologic Feature Assessed

Miocene Moon-Utawa Arc and coeval rocks in the Ular Merah area of Papua and West Papua Provinces, Indonesia.

Delineation of the Permissive Tract

Tectonic Setting

The tract delineates middle to late Miocene igneous rocks on western New Guinea Island (fig. L2). The tract includes three 

areas: A, the Moon Arc area in the northern part of the Bird’s Head region; B, the Utawa diorite in Bird’s Neck region; and C, 

1

U.S. Geological Survey, Reston, Virginia, United States.

2

Center for Geological Resources, Geological Agency of Indonesia, West Java, Indonesia.

3

U.S. Geological Survey, Menlo Park, California, United States.

4

U.S Geological Survey, Spokane, Washington, United States.

5

Mineral Resources Authority, Papua New Guinea.
Appendix L—Tract 142pCu7205 187

the Ular Merah area of the western Central Range of the Bird’s 

Body region (fig. L2). These rocks are age-equivalent to the 

Maramuni Arc in the Mobile Belt of Papua New Guinea (tract 

009pCu7205).

The name Moon-Utawa Arc (fig. L1, areas A and B) 

was proposed by Carlile and Mitchell (1994) for the middle 

Miocene Moon Volcanics of the northern part of the Bird’s 

Head and the mid-Miocene Utawa Diorite of the Bird’s Neck. 

Garwin and others (2005) noted that although there is igneous activity in this region, the relation of the arc to a subduction zone is not clear. The Miocene rocks may have formed 

in a north-facing arc along a passive continental margin prior 

south-directed thrusting in the late Miocene (Melanesian 

orogeny) that displaced the Utawa Diorite to the south along 

the Weyland thrust (fig. 7) (Carlile and Mitchell, 1994; Dow 

and Robinson, 1985). The Moon Volcanics may be linked 

to the Maramuni Arc, but as noted by Malaihollo and Hall 

(1996), the nature and distribution of the volcanism and its 

relation to the Maramuni rocks remains unclear. The Miocene 

igneous rocks in western New Guinea lie within allochthonous 

arc/forearc terranes and may have originated much farther 

(>500 km) northeast of their present location (Cloos and others, 2005). The Bird’s Head block, or microplate, represents 

a recent escape tectonic zone formed by convergence of the 

Australian Plate with volcanic arcs (Pubellier and Ego, 2002).

The Ular Merah area (fig. L1, area C) was not known to 

be of Miocene age prior to a recent study that established the 

age, chemistry, and isotopic signature (Jackson, 2010). The Ular 

Merah Miocene rocks may have formed due to partial remelting of mid-Cenozoic arc garnet-bearing plutons mixed with an 

asthenospheric mantle component (as indicated by the isotopic 

signature) and generated in a mid-Miocene spreading center in 

the Ayu Trough (see fig. 6). The Ayu Trough is an intraoceanic 

rift system that marked the southeastern boundary between the 

Philippine and Pacific Plates, prior to left-lateral fault displacement of the Ayu Trough during the last 4 million years (Jackson, 

2010). The relationship to the Moon-Utawa Arc is unknown.

Geologic Criteria

The tract was constructed in a GIS using 1:250,000-scale 

geologic maps of Indonesia, a 1:500,000-scale digital map of 

igneous rocks of Indonesia (Directorate of Mineral Resources 

and Inventory, 2004a) and the 1:1,000,000-scale geologic map 

of Irian Jaya (Dow and others, 1986). Maps and figures showing the major faults, lineaments, and tectonic divisions of New 

Guinea by Garwin and others (2005), Hill and others (2002), 

and Quarles van Ufford and Cloos (2005) also were used. 

Map units were classified into generalized units by age and 

lithologic class (igneous volcanic, igneous plutonic). From this 

digital database of geologic lithology and age attributes, all 

igneous rocks of Miocene age (>7 Ma and exclusive of rocks 

mapped as late Miocene or younger) were selected. Ophiolites, 

ultramafic rocks, and basaltic units were deemed non-permissive and are omitted from the tract. Map units included in the 

tract are listed in table L2.

The final tract boundaries were established by GIS 

processing and editing. The processing approximates manual 

delineation of tracts but is rapid and reproducible. The processing steps included (1) unioning of buffered permissive 

map units and other polygon features that comprise the framework of the tract; (2) aggregating unioned polygons using an 

aggregation distance of 15 km and a minimum hole size of 

1,000 km2 (this step was done to group closely spaced permissive areas); (3) manually aggregating and adjusting of tract 

areas; and (4) smoothing polygons using an algorithm (PAEK, 

polynomial approximation with exponential kernal) with a 

tolerance of 1 km. Preliminary tracts were cleaned to remove 

necking and thinning introduced by processing; tracts were 

compared with source maps to ensure that original permissive 

boundaries and buffer distances were honored. Regional and 

local mineral occurrence, geochemical, and isotopic-age data 

were plotted and used to constrain or expand tract boundaries; 

in particular, a database of isotopic ages of igneous rocks for 

Indonesia compiled by the Southeast Asia Research Group 

provided additional controls on distributions of permissive 

rocks (Malaihollo and others, 2002). Tract boundaries were 

clipped at shorelines (U.S. Department of State, 2009).

The three tract areas are (fig. L1):

A. Moon Arc, Northern Bird’s Head.—This area outlines 

the middle Miocene Lembia diorite, Moon Volcanics, Mandi 

Volcanics, and Dore Volcanics along the northern margins 

of the Bird’s Head, north of the Sorong Fault. Carlile and 

Mitchell (1994) noted extensive hydrothermal alteration in 

the andesitic Moon Volcanics. An area that extends north of 

the Sorong Fault to the coast includes the historical Alpha 

prospect in the Moon Volcanics of the Bird’s Head. The area 

is the focus of Hillgrove Resources (2009a,b,c; 2010) recent 

advanced exploration projects (Delta West, Delta, Golf, Bravo, 

Alpha, and Foxtrot prospects). Carlile and Mitchell considered 

the Moon-Utawa Arc to be underexplored in 1994. No deposits are known in this part of the tract.

B. Utawa Arc, Bird’s Neck.—Area B outlines the Utawa 

Diorite in the Weyland overthrust in the Bird’s Neck area. 

These rocks were emplaced (either intruded or by faulting) 

in the Melanesian Arc, translated westward as much as 500 

km or more (Cloos and others, 2005), and displaced southwards from the late Miocene to the present. This part of the 

tract lacks known deposits and volcanic rocks; it contains 

more than 10 sites where anomalous gold has been detected 

by exploration, mainly in stream sediments. No deposits are 

known in this part of the tract.

C. Ular Merah, western Central Range.—The Ular 

Merah area is centered on a Miocene (17.4–16.6 Ma) porphyry 

system that intruded the allochthonous Central Ophiolite Belt 

in Irian Jaya, approximately 150 km northwest of the Erstberg 

mining district (Jackson, 2010). In the Ular Merah area, Jackson (2010) described 11 mid-Miocene intrusions as high-K 

calc-alkaline porphyritic diorites and monzodiorites characterized by low initial 87Sr/86Sr isotopic ratios (~0.704) and 

radiogenic εNd (~3.9). She demonstrated that the Ular Merah 

rocks are chemically distinct from coeval rocks in Papua New 
188 Porphyry Copper Assessment of Southeast Asia and Melanesia

Guinea (Maramuni Arc), from Pliocene rocks in the Medial 

New Guinea magmatic belt, and from older intrusions in the 

Ophiolite Belt.

Area C was delineated based on mapped exposures of 

Auwewa Formation (Eocene to early Miocene volcanic, subvolcanic diorite and microdiorite intrusions) in the Ular Merah 

area and was extended to include dated samples described by 

Jackson (2010, table 1-1 and fig. 1-4).

Known Deposits

None.

Prospects, Mineral Occurrences, and Related 

Deposit Types

The Moon Arc area includes more than 10 discrete historical stream-sediment anomaly localities, as well as copper 

and gold soil anomalies. Channel sampling at the West Delta 

prospect identified copper (0.6–3.1 percent), gold (<0.001–1. 

98 ppm) and molybdenum (1–512 ppm) in potassic and phyllic alteration zones associated with a breccia target and aeromagnetic highs (table L3) (Hillgrove Resources, 2010).

The Utawa area includes about 15 sites reported as anomalous in gold (Directorate of Mineral Resources and Inventory, 

2004b), including stream-sediment sites and exploration sites.

Exploration History

The Indonesian Directorate of Mineral Resources explored 

throughout Papua and West Papua in 2004.

The Bird’s Head area is under exploration for porphyry 

copper and epithermal gold deposits (Hillgrove Resources, 

2009a,b,c; 2010).

The Utawa area was included in the Directorate of Mineral 

Resources Inventory, and parts of the area were covered by PT 

Nabire Bakti Mining’s contract of work (COW). The team is 

unaware of any current exploration activity in the Utawa area.

The Ular Merah tract area covers Block 2 of Eastern Minerals COW exploration area. PT Freeport Indonesia explored the 

Ular Merah area in 2007; five cores drilled in areas of anomalous copper and gold in soil samples showed little evidence of 

copper mineralization (Jackson, 2010).

Sources of Information

Principal sources of information used by the assessment 

are listed in table L4.

Grade and Tonnage Model Selection

No porphyry copper deposits with identified resources 

are known within the tract. The team considered both the 

Table L2. Map units that define tract 142pCu7205, Moon-Utawa-Ular Merah Areas—Indonesia.

[Map unit, age range, and principal lithologies are based on a digital compilation of geologic maps of Indonesia (Directorate of Mineral Resources and Inventory, 

2004a) and scanned and rectified 1:250,000-scale quadrangle maps of Irian Jaya. Map symbols, lithology, and age ranges are based on 1:250,000-scale geologic 

maps. *, intrusions in this area recently dated as mid-Miocene (Jackson, 2010). See table L4 for references] 

Map unit Map symbol Lithology Age range

Moon Arc area

Moon Volcanics Tmm Andesite; comagmatic diorite intrusions Middle Miocene

Dore Volcanics Tmdo Andesitic lava; include small bodies of diorite Miocene

Mandi Volcanics Temm Basalt to andesite; includes small bodies of gabbro, diorite, 

granodiorite, porphyritic andesite

Oligocene to middle Miocene

Utawa Arc area

Utawa Diorite Tmu Diorite, quartz diorite Middle Miocene

Ular Merah area

Auwewa Formation Tema Island-arc volcanic rocks, subvolcanic diorite and microdiorite 

intrusions

Eocene to early Miocene*
Appendix L—Tract 142pCu7205 189

Table L3. Significant prospects and occurrences tract 142pCu7205, Moon-Utawa-Ular Merah Areas—Indonesia.

[Ages all assumed to be Miocene based on associated map units or dated igneous rocks. Rank 3=drilled, with >20 m of 0.2% or more Cu. Rank 2=drilled or 

trenched with <20 m of 0.2% Cu, or <0.2% Cu, or past or ongoing exploration. Rank 1=copper occurrence that may be related to porphyry-type mineralization 

based on stream sediment or magnetic anomaly or location along structural trend. %, percent; g/t, grams per metric ton; km, kilometers; m, meters; ppb, parts per 

billion] 

Name Latitude Longitude Comments Reference Rank

Moon Arc area

Alpha prospect 

(Bird’s Head 

project)

-0.628 132.604 Alpha prospect area; discovered by stream-sediment sampling, 

intermediate to felsic volcanics, volcaniclastics, and hypabyssal intrusions 

(Moon Volcanics); epithermal Au, Pb-Zn-Ag, and Au-Cu phase. Soil 

sampling, trenching; recon drilling (5 holes on Au soil anomaly); drill 

intercepts 17.45 m at 0.29% Cu, 2.16 g/t Au, 18.36 g/t Ag, 2.08% Pb, and 

5.31% Zn.

Hillgrove Resources 

(2009a,b,c; 2010)

2

Delta prospect 

(Bird’s Head 

project)

-0.415 132.636 Low-grade copper intersected in drilling (102.4 m at 0.21% Cu) associated 

with a granodiorite/diorite intrusion; 6 by 1.5 km copper soil anomaly 

zone; possible epithermal Au-Ag. Zoned hydrothermal alteration mapped 

around a breccia at the West Delta prospect. Circular features and clusters 

of aeromagnetic highs may represent shallow buried intrusions. 

Hillgrove Resources 

(2009a,b,c; 2010)

3

Utawa Arc area

Sungai DepaSungai Waria

-3.648 135.802 100 to 200 ppb Au associated with Utawa Diorite; chalcopyrite, pyrite, 

pyrrhotite.

Directorate of 

Mineral Resources 

and Inventory 

(2004b)

1

Table L4. Principal sources of information used for tract 142pCu7205, Moon-Utawa-Ular Merah Areas—Indonesia.

[CCOP, Coordinating Committee for Coastal and Offshore Geoscience Programmes in East and Southeast Asia; NA, not applicable]

Theme Map or title Scale Citation

Geology Digital geologic map of East and Southeast Asia 1:2,000,000 CCOP and Geological Survey of Japan (1997)

Digital geologic map of Indonesia 1;1,000,000 Directorate of Mineral Resources and Inventory (2004a)

Geologic quadrangle maps (Enaratoli, Sorong, 

Kasim, West Waigeo and Misool quadrangles)

1:250,000 Harahap and others (1990); Sanyoto and others (1985) 

SE Asia Radiometric Ages: GIS Database NA Malaihollo and others (2002)

Geologic map of Irian Jaya, Indonesia 1:1,000,000 Dow and others (1986)

Mineral

occurrences

Porphyry copper deposits of the world: database, 

map, and grade and tonnage models

NA Singer and others (2008)

Digital mineral occurrence database NA Directorate of Mineral Resources and Inventory (2004b)

Exploration Company Web sites NA Hillgrove Resources (2009a,b,c; 2010), van Leeuwan (1994)
190 Porphyry Copper Assessment of Southeast Asia and Melanesia

general global porphyry copper and the global copper-gold 

subtype models of Singer and others (2008). Based on selection of the copper-gold model for the age-equivalent Miocene 

Maramuni Arc of Papua New Guinea, recent exploration 

targets for copper-gold systems, and the likelihood that further 

characterization may establish that a copper-gold model is 

more appropriate for assessing undiscovered resources in this 

part of Indonesia, the copper-gold subtype model was used. 

The general model was tested for comparison. Note that statistical test for the Maramuni tract, based on ANOVA tests for 

the Frieda River deposit, also supports either model.

Estimate of the Number of Undiscovered Deposits

Rationale for the Estimate

The three areas differ in level of exposure: Moon Arc 

area (A), mainly volcanic; Utawa Arc area (B), entirely intrusive; Ular Merah area (C), volcanic with very small, subvolcanic intrusions. In the age-equivalent Miocene Maramuni Arc 

in Papua New Guinea, the volume of intrusive rocks is greater 

than the volume of preserved volcanic rocks, and volcanic 

rocks are more abundant on the southern margin of the tract. 

The 12–14 Ma Frieda River deposit (1,060 Mt, 0.52 percent 

copper, 0.004 percent molybdenum, 0.31 g/t gold) in Papua 

New Guinea is within the Maramuni tract (009pCu7205). The 

team considered the likelihood that continued exploration in 

the Bird’s Head area could lead to a discovery. Aeromagnetic 

data noted in recent exploration in the Bird’s Head over an 

area of more than 900 km2 along with geochemical data from 

exploration trenching, copper and gold soil anomalies, and 

mapped alteration indicate that porphyry copper deposits may 

be present in the subsurface (Hillgrove Resources, 2010). 

Further drilling is required to document the extent and quality 

of any potential deposits.

The Utawa area is not well-explored, but does include 

some indications of copper mineralization associated with the 

Utawa diorite. The Ular Merah area has been drilled, with no 

promising results reported. On the basis of this information, 

the team made estimates for the entire tract area: a 50-percent 

chance of one or more deposits and a 10-percent chance of 

two or more deposits (table L5), which results in a mean of 

1± 0.8 deposits.

Probabilistic Assessment Simulation Results

Undiscovered resources for the tract were estimated by 

combining consensus estimates for numbers of undiscovered 

porphyry copper deposits with the copper-gold subtype model 

of Singer and others (2008) using the EMINERS program 

(Root and others, 1992; Bawiec and Spanski, 2012; Duval, 

2012). The simulation also was run using the general global 

porphyry copper model for comparison. Selected simulation 

results are reported in table L6. Results of the Monte Carlo 

simulations are presented as a cumulative frequency plots 

(fig. L3). The cumulative frequency plots show the estimated 

resource amounts associated with cumulative probabilities of 

occurrence, as well as the mean, for each commodity and for 

total mineralized rock. The simulation based on the general 

model predicts a mean amount of 3.8 Mt copper, 110,000 t 

molybdenum, 93 t gold, and 1,200 t silver (table L6). Note that 

the probabilities of zero (none) are 0.5 or more for molybdenum, gold, and silver using the general model. Based on the 

simulation using the copper-gold subtype model, the mean 

amount of copper is 3.2 Mt and the simulation predicts a 

50-percent chance of 64 or more tons of gold. For both models, the mean copper exceeds the median (0.5 probability) by 

an order of magnitude.

Table L5. Undiscovered deposit estimates, deposit numbers, tract area, and deposit density for tract 142pCu7205, Moon-Utawa-Ular 

Merah Areas—Indonesia.

[NXX, estimated number of deposits associated with the xxth percentile; Nund, expected number of undiscovered deposits; s, standard deviation; Cv%, coefficient of 

variance; Nknown, number of known deposits in the tract that are included in the grade and tonnage model; Ntotal, total of expected number of deposits plus known 

deposits; km2, area of permissive tract in square kilometers; Ntotal/100k km2, deposit density reported as the total number of deposits per 100,000 km2. Nund, s, and 

Cv% are calculated using a regression equation (Singer and Menzie, 2005)]

 Consensus undiscovered 

 deposit estimates Summary statistics Tract area 

(km2

)

Deposit density 

(Ntotal/100k km2)

N90 N50 N10 N05 N01 Nund s Cv% Nknown Ntotal

0 1 2 2 2 1 0.79 79 0 1 13,580 7
Appendix L—Tract 142pCu7205 191

References Cited

Bawiec, W.J., and Spanski, G.T., 2012, Quick-start guide for 

version 3.0 of EMINERS—Economic Mineral Resource 

Simulator: U.S. Geological Survey Open-File Report 

2009–1057, 26 p., accessed June 30, 2012, at http://pubs.

usgs.gov/of/2009/1057. (This report supplements USGS 

OFR 2004–1344.)

Berger, B.R., Ayuso, R.A., Wynn, J.C., and Seal, R.R., 

2008, Preliminary model of porphyry copper deposits: 

U.S. Geological Survey Open-File Report 2008–1321, 

55 p., accessed May 15, 2010, at http://pubs.usgs.gov/

of/2008/1321.

Carlile, J.C., and Mitchell, A.H.G., 1994, Magmatic arcs and 

associated gold and copper mineralization in Indonesia: 

Journal of Geochemical Exploration v. 50, p. 91–142.

Cloos, Mark, Sapiie, B., Quarles van Ufford, A., Weiland, 

R.J., Warren, P.Q., and McMahon, T.P., 2005, Collisional 

delamination in New Guinea—The geotectonics of 

subducting slab breakoff: Geological Society of America 

Special Paper 400, 51 p.

Cooke, D.R., Heithersay, P.S., Wolfe, R., and Calderon, A.L., 

1998, Australian and western Pacific porphyry Cu-Au 

deposits: Journal of Australian Geology and Geophysics, 

v. 17, no. 4, p. 97–104.

Coordinating Committee for Coastal and Offshore Geoscience 

Programmes in East and Southeast Asia (CCOP) and 

Geological Survey of Japan, 1997, Digital geologic map 

of East and Southeast Asia: Geological Survey of Japan, 

Digital Geoscience Map G-2 scale 1:2,000,000, CD-ROM.

Cox, D.P., 1986, Descriptive model of porphyry Cu-Au 

(Model 20c), in Cox, D.P., and Singer, D.A., eds., 1986, 

Mineral deposit models: U.S. Geological Survey Bulletin 

1693, p. 110. (Also available at http://pubs.usgs.gov/bul/

b1693/.)

Directorate of Mineral Resources and Inventory, 2004a, 

Digital geologic map: Jakarta, Indonesia, Indonesian 

Ministry of Energy and Mineral Resources, scale 

1:1,000,000. [Proprietary data.]

Directorate of Mineral Resources and Inventory, 2004b, 

Digital mineral occurrence database: Jakarta, Indonesia, 

Table L6. Results of Monte Carlo simulations of undiscovered resources for tract 142pCu7205, Moon-Utawa-Ular Merah Areas—Indonesia.

[Cu, copper; Mo, molybdenum; Au, gold; and Ag, silver; in metric tons; Rock, in million metric tons]

Material

A. Probability of at least the indicated amount Probability of

0.95 0.9 0.5 0.1 0.05 Mean Mean or 

greater None

Cu 0 0 810,000 8,100,000 15,000,000 3,800,000 0.22 0.29

Mo 0 0 0 200,000 440,000 110,000 0.15 0.55

Au 0 0 0 230 420 93 0.20 0.51

Ag 0 0 0 2,300 5,100 1,200 0.16 0.64

Rock 0 0 190 1,700 3,000 760 0.24 0.29

Material

B. Probability of at least the indicated amount Probability of

0.95 0.9 0.5 0.1 0.05 Mean Mean or 

greater None

Cu 0 0 660,000 7,200,000 15,000,000 3,200,000 0.21 0.3

Mo 0 0 0 30,000 73,000 18,000 0.14 0.68

Au 0 0 64 560 1,000 230 0.23 0.3

Ag 0 0 0 2,000 4,400 1,100 0.15 0.59

Rock 0 0 150 1,500 3,100 640 0.22 0.3
192 Porphyry Copper Assessment of Southeast Asia and Melanesia

Indonesian Ministry of Energy and Mineral Resources. 

[Proprietary data.]

Dow, D.B., 1977, A geological synthesis of Papua New 

Guinea: Australian Bureau of Mineral Resources Bulletin 

201, Geology and Geophysics, 41 p.

Dow, D.B., Robinson, G.P., Hartono, U., and Ratman, N., 

1986, Geologic map of Irian Jaya, Indonesia: Bandung, 

Geological Research and Development Centre, 1 map on 2 

sheets, scale 1:1,000,000. [In English and Indonesian.]

Dow, D.B., and Robinson, G.P., 1985 A new hypothesis for the 

formation of the Lengguru Fold Belt, Irian Jaya, Indonesia: 

Republic of Indonesia, Bulletin of the Geological Research 

and Development Centre, no. 11, p. 14–28. 

Duval, J.S., 2012, Version 3.0 of EMINERS—Economic 

Mineral Resource Simulator: U.S. Geological Survey Open 

File Report 2004–1344, accessed July 5, 2012, at http://

pubs.usgs.gov/of/2004/1344.

Garwin, S., Hall, R., and Watanabe, Y., 2005, Tectonic setting, 

geology, and gold and copper mineralization in Cenozoic 

magmatic arcs of southeast Asia and the west Pacific, in

Hedenquist, T.W., Thompson, J.F.H., Goldfarb, R.J., and 

Richards, J.P., eds., One hundredth anniversary volume 

1905–2005: Littleton, Colorado, Society of Economic 

Geologists, p. 891–930.

Harahap, B.H., Sufni Hakim, A., and Dow, D.B., 1990, 

Geological map of the Enarotali sheet, Irian Jaya: Bandung, 

Geological Research and Development Centre, sheet no. 

3112, scale 1:250,000.

Hill, K.C., Kendrick, R.D., Crowhurst, P.V., and Gow, P.A., 

2002, Copper-gold mineralisation in New Guinea—

Tectonics, lineaments, thermochronology and structure, in

Korsch, R.J., ed., Geodynamics of Australia and its mineral 

systems: Technologies, syntheses and regional studies: 

Melbourne, Australia, Blackwell Scientific Publications for 

the Geological Society of Australia, p. 737–752.

Hillgrove Resources, 2009a, Alpha prospect shapes up as a 

major gold target, January 29, 2009: accessed February 10, 

2010, at http://www.hillgroveresources.com.au/downloads/

asx/090129%20Alpha%20Prospect%20Shapes%20up%20

as%20Major%20Gold%20Target.pdf.

Hillgrove Resources, 2009b, Hillgrove Resources 2009 

Annual General Meeting, Adelaide, 24 June 2009: accessed 

February 10, 2010, at http://www.hillgroveresources.com.

au/downloads/presentations/090624%20Managing%20

Directors%20AGM%20Presentation.pdf.

Hillgrove Resources, 2009c, Hillgrove Resources Annual 

Report 31 January 2009: acessed June15, 2009, at http://

www.docviewserve.com.au/docviewserve/docviewserve.

dll/EXEC.

Hillgrove Resources, 2010, Bird’s Head exploration 

target—Update: accessed March 13, 2010, at http://www.

hillgroveresources.com.au/downloads/asx/101116%20

Birds%20Head%20Exploration%20Target%20Update.pdf.

Jackson, J.E., 2010, Neogene intrusions in the western Central 

Range, Papua, Indonesia—Petrologic, geochemical, and 

isotopic comparison of the Miocene Ular Merah and 

Pliocene Komopa magmatic districts: The University of 

Texas at Austin, M.S. thesis, 360 p.

John, D.A., Ayuso, R.A., Barton, M.D., Blakely, R.J., Bodnar, 

R.J., Dilles, J.H., Gray, Floyd, Graybeal, F.T., Mars, J.C., 

McPhee, D.K., Seal, R.R., Taylor, R.D., and Vikre, P.G., 

2010, Porphyry copper deposit model, chap. B of Mineral 

deposit models for resource assessment: U.S. Geological 

Survey Scientific Investigations Report 2010–5070–B, 

169 p., accessed September 8, 2010, at http://pubs.usgs.gov/

sir/2010/5070/b/.

Kamitani, M., and Naito, K., eds., 1998, Mineral resource 

map of Asia: Metal Mining Agency of Japan, 1 sheet, scale 

1:35,000,000. (Also available at www.mmaj.go.jp/mric_

web/deposit/index.htm.)

Malaihollo, J.F.A., and Hall, R., 1996, The geology and 

tectonic evolution of the Bacan region, east Indonesia, 

in Hall, R., and Blundell, D., eds., Tectonic evolution of 

Southeast Asia: Geological Society of London, Special 

Publication No. 106, p. 483–497.

Malaihollo, J.F.A., Hall, R., and Macpherson, C.G., 2002, SE 

Asia radiometric ages—GIS database: accessed January 15, 

2010, at http://searg.rhul.ac.uk/current_research/isotopic_

ages/SEAsia_GIS.pdf.

Pubellier, M., and Ego, F., 2002, Anatomy of an escape 

tectonic zone—Western Irian Jaya (Indonesia): Tectonics, 

v. 21, no. 4, p. 1–16.

Quarles van Ufford, Andrew, and Cloos, Mark, 2005, Cenozoic 

tectonics of New Guinea: Bulletin of the American Association 

of Petroleum Geologists, v. 89, no. 1, p. 119–140.

Root, D.H., Menzie, W.D., and Scott, W.A., 1992, Computer 

Monte Carlo simulation in quantitative resource estimation: 

Natural Resources Research, v. 1, no. 2, p. 125–138.

Sanyoto, P., Pieters, P.E., Amri, C.H., Simandjutak, W., and 

Supriatna, S., 1985, Preliminary geological map of parts of 

the Sorong, Kasim, West Waigeo and Misool quadrangles, 

Irian Jaya: Geological Research and Development Centre 

Ministry of Mines and Energy Republic of Indonesia, sheet 

nos. 2815, 2814, 2715 and 2714, scale 1:250,000.

Sillitoe, R.H., 1995, Exploration and discovery of base- and 

precious-metal deposits in the Circum-Pacific region during 

the last 25 years: Tokyo, Society of Resource Geology, 

Resource Geology Special Issue no. 19, 119 p.
Appendix L—Tract 142pCu7205 193

Singer, D.A., and Menzie, W.D., 2005, Statistical guides to 

estimating the number of undiscovered mineral deposits—An 

example with porphyry copper deposits, in Cheng, Qiuming, 

and Bonham-Carter, Graeme, eds., Proceedings of IAMG—

The annual conference of the International Association for 

Mathematical Geology: Toronto, Canada, York University, 

Geomatics Research Laboratory, p. 1028–1033.

Singer, D.A., Berger, V.I., and Moring, B.C., 2008, Porphyry copper 

deposits of the world—Database and grade and tonnage models, 

2008: U.S. Geological Survey Open-File Report 2008–1155, 

accessed June 1, 2011, at http://pubs.usgs.gov/of/2008/1155/.

U.S. Department of State, 2009, Small-scale digital 

international land boundaries (SSIB)—Lines, edition 

10, and polygons, beta edition 1, in Boundaries and 

sovereignty encyclopedia (B.A.S.E.): U.S. Department of 

State, Office of the Geographer and Global Issues.

van Leeuwen, T.M., 1994, 25 Years of mineral exploration 

and discovery in Indonesia, in van Leeuwen, T.M., 

Hedenquist, J.W., James, L.P., and Dow, J.A.S., eds., 

Indonesian mineral deposits—Discoveries of the past 25 

years: Journal of Geochemical Exploration, v. 50, p.13–90.
132° E 136° E 0° 4° S Sungai Depa - Sungai Waria Delta prospect (Bird’s Head project) Alpha prospect (Bird’s Head project) INDONESIA PACIFIC OCEAN Cenderawasih Bay Seram Sea Arafura Sea 120°E 

20°N0° 20°S A

PH 

A, Moon arc area B, Utawa arc area C, Ular Merah area Political boundary source: U.S. Department of State (2009) Projection: Asia South Albers Equal Area Conic; Central meridian 134° E; latitude of origin 15° S 0 50 100 150 200 KILOMETERS 0 50 100 MILES EX

OtheAsse142pPorpdepotrac

Porpprostrac

Figure L1. Map showing tract location and significant porphyry copper prospects for tract 142pCu7205, Moon-Utawa-Ular Merah Areas—Indon

Philippines; PG, Papua New Guinea.
( ( (

(

( ( ( (

(

( ( ( ( ( ( ( ( ( 

( ( ( ( ( ( ( ( ( ( ( ( ( ( ( (

( ( (

( ( ( ( ( ( ( ( ( ( (

( (

( ( ( ( ( ( ( ( ( ( ( 

( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( 

INDONESIA

PACIFIC OCEAN

Cenderawasih Bay

Arafura Sea

Ceram Sea

Sungai Depa - Sungai Waria

Delta prospect (Bird’s Head project)Alpha prospect (Bird’s Head project)

132° E 134° E 136° E

0°

2° S4° S

Base from ESRI ArcGIS Online (2009)World Shaded ReliefPolitical boundary source: U.S. Department of State (2009)Projection: Asia South Albers Equal Area Conic;Central meridian 134° E; latitude of origin 15° S

0 50 100 150 200 KILOMETERS

0 50 100 MILES

E

Ass 14PorPerPerAus

( ( Sub

Stri

A, Moon Arc area

B, Utawa Arc area

C, Ular Merah area

Figure L2. Map showing the distribution of permissive igneous rocks for tract 142pCu7205, Moon-Utawa-Ular Merah Areas—Indonesia.
196 Porphyry Copper Assessment of Southeast Asia and Melanesia

0.01 0.1 1 10 100 1k 10k 100k 1M 10M 100M 1B 10B 100B

Material, in metric tons

1.00

0.90

0.80

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

Probability

Mean Cu

Mean Mo

Mean Au

Mean Ag

Mean Rock

Cu

Mo

Au

Ag

Rock

Mean Cu

Mean Mo

Mean Au

Mean Ag

Mean Rock

EXPLANATION B

1.00

0.90

0.80

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

Probability

0.01 0.1 1 10 100 1k 10k 100k 1M 10M 100M 1B 10B 100B

Material, in metric tons

Mean Cu

Mean Mo

Mean Au

Mean Ag

Mean Rock

Cu

Mo

Au

Ag

Rock

Mean Cu

Mean Mo

Mean Au

Mean Ag

Mean Rock

EXPLANATION

A

Figure L3. Cumulative frequency plot showing the results of Monte Carlo computer simulation of undiscovered 

resources in tract 142pCu7205, Moon-Utawa-Ular Merah Areas—Indonesia. A, Based on general porphyry copper 

grade and tonnage model. B, Based on porphyry copper, copper-gold subtype grade and tonnage models. k, thousands; 

M, millions; B, billions; Tr, trillions.
Appendix M—Tract 142pCu7203 197

Appendix M. Porphyry Copper Assessment for Tract 142pCu7203, 

Western Medial New Guinea Magmatic Belt—Indonesia

By Jane M. Hammarstrom1, Bambang Tjahjono Setiabudi2, Dwi Nugrono Sunuhadi2, Gilpin R. Robinson, Jr.1, 

Connie L. Dicken1

, Steve Ludington3, Arthur A. Bookstrom4, and Michael L. Zientek4, with contributions from 

Gwaibo Kopi5

 and Dennis P. Cox3

Deposit Type Assessed: Porphyry copper, copper-gold subtype

Descriptive model: Porphyry copper (Berger and others, 2008; John and others, 2010); Porphyry copper-gold 

(Cox, 1986; Cooke and others, 1998)

Grade and tonnage model: Porphyry copper, copper-gold subtype (Singer and others, 2008)

Table M1 summarizes selected assessment results.

Table M1. Summary of selected resource assessment results for tract 142pCu7203, Western Medial New Guinea Magmatic Belt—

Indonesia.

[km, kilometers; km2, square kilometers; t, metric tons] 

Date of assessment Assessment 

depth (km)

Tract area 

(km2)

Known copper 

resources (t)

Mean estimate of 

undiscovered copper 

resources (t)

Median estimate of

undiscovered copper 

resources (t)

February 2010 1 13,270 24,000,000 14,000,000 6,500,000

1

U.S. Geological Survey, Reston, Virginia, United States.

2

Center for Geological Resources, Geological Agency of Indonesia, West Java, Indonesia.

3

U.S. Geological Survey, Menlo Park, California, United States.

4

U.S. Geological Survey, Spokane, Washington, United States.

5

Mineral Resources Authority, Papua New Guinea.

Location

The tract includes the Central Highlands of New Guinea Island and the Indonesian provinces of West Papua and Papua, 

formerly known as Irian Jaya (fig. M1).

The tract represents the western part of the Medial New Guinea magmatic belt, an 1,800-km-long, east-west belt of discontinuous exposures of late Miocene to Pliocene igneous rocks that spans the fold belt of central New Guinea Island (fig. 3, no. 13; 

fig. 7). The eastern part of the belt is represented by tract 009pCu7203.

Geologic Feature Assessed

The late Miocene to Pliocene-Pleistocene Medial New Guinea magmatic belt.
198 Porphyry Copper Assessment of Southeast Asia and Melanesia

Delineation of the Permissive Tract

Tectonic Setting

Tract 142pCu7203 outlines exposed segments of the late 

Miocene and Pliocene to Pleistocene Medial New Guinea 

magmatic belt in the Indonesian provinces of Papua and West 

Papua. The magmatic belt formed from convergence of the 

Indo-Australian and Pacific Plates during the Cenozoic (fig. 

6). The tract lies within the western Papuan fold belt (fig. 7). 

No well-defined subduction zone is associated with the belt, 

although seismic tomography suggests the existence of old 

subduction slabs within the mantle under New Guinea (Hall 

and Sparkman, 2002; Garwin and others, 2005). South-dipping 

subduction following a reversal in subduction polarity, postcollision uplift, and transitions to extensional tectonism all 

have been postulated to explain the lower volume, more alkaline, post-Maramuni Arc (Miocene) magmatic activity (Housh 

and McMahon, 2000). As noted by Garwin and others (2005), 

the tectonic trigger for the high-K, calc-alkaline to alkaline 

magmatic event is not well understood, but it is likely related 

to the southward progressing compressional deformation that 

formed and uplifted the fold belt as a result of convergence of 

New Guinea and the Caroline Plate to the north (fig. 6). Local 

dilational zones formed at intersections of strike-parallel (generally east-west) frontal thrust faults and strike-perpendicular 

long-lived crustal transfer structures, expressed as lineaments, 

facilitated emplacement of magmas and associated porphyry 

copper-gold mineralization in central New Guinea (Hill and 

others, 2002). Cloos and Housh (2008) described the coincidence of magmatic-hydrothermal and structural conditions that 

led to the formation of the giant Grasberg orebody at about 3 

Ma. Namely, the deposit was emplaced in a pull-apart zone 

along an active strike-slip fault. They attribute the elevated 

Au/Mo ratio to magma formed in a collisional delamination 

(rather than a subduction) tectonic setting, where the local 

structural environment and rate of solidification facilitated 

concentration of a metal-rich cupola to form the deposit. Cloos 

and others (2005) concluded that rocks formed from the shortlived (7–2.5 Ma) magmatic event are localized at the highest 

elevation in the Central Highlands because they formed above 

the zone of maximum asthenospheric upwelling as a result of 

collisional delamination. The structural style that characterized

the Grasberg area has not been documented for Pliocene calcalkaline intrusions farther to the west, such as at the Aisasjur 

porphyry copper prospect in the Bird’s Head (Garwin and 

others, 2005).

The nature of the basement in the western and eastern 

parts of Medial New Guinea magmatic belt differs from west 

to east. Tract 142pCu7203 delineates parts of the belt that lie 

west of the Tasman Line. The Tasman Line is interpreted as 

extending roughly north-south to northwest through an area 

approximately 100 km west of the modern Indonesian (Irian 

Jaya)-Papua New Guinea border (fig. 6 of main report). The 

Tasman Line defines two crustal provinces in northern Australia and is projected north into New Guinea Island: Paleozoic 

basement of the accreted terranes of the Tasman orogen lie to 

the east of the line; the stable craton with Precambrian basement lies to the west (Hill and Hall, 2003). These differences 

in basement affect the crustal response to deformation, and 

may influence the character of porphyry-related magmas.

Geologic Criteria

The tract was constructed in a GIS using a 1:1,000,000-

scale digital map of igneous rocks of Indonesia (Directorate 

of Mineral Resources and Inventory, 2004a), along with the 

1:1,000,000-scale geologic map of Irian Jaya (Dow and others, 

1986), and 1:250,000-scale maps of Indonesia (Geological 

Research and Development Centre, 1987–2000). Maps and 

figures showing the major faults, lineaments, and tectonic 

divisions of New Guinea by Garwin and others (2005), Hill 

and others (2002), and Quarles van Ufford and Cloos (2005) 

also were used.

Map units were classified into generalized units by age 

and lithologic class (igneous volcanic, igneous plutonic) based 

on map legend attributes (table M2). From this digital database 

of map units grouped by age and lithology, all igneous rocks 

of late Miocene to Pliocene age were selected. Examination 

of cross sections on 1:250,000-scale geologic maps showed 

that most intrusive rocks of this age range are shown as steepsided, cylindrical or finger-like intrusive bodies with a subsurface horizontal extent of <2–5 km; vertical extents can exceed 

1 km. On Indonesian maps, predominantly volcanic units may 

include small intrusive bodies of diorite or microdiorite.

Using GIS tools, a 5-km buffer was applied around 

mapped igneous contacts of permissive lithologies to account 

for spatial uncertainty in digitized geology and for the possibility of greater extent of permissive rocks within a kilometer 

of the surface. Ophiolites and ultramafic rocks, basaltic units, 

and units that are predominantly ash flows, tuffs, and agglomerates were deemed nonpermissive and are omitted from the 

tract.

The buffered map units were aggregated using GIS 

processing tools with a 15 km distance to group closely spaced 

permissive areas, which were then edited to honor fault boundaries and include other areas of known igneous rocks of appropriate age and lithology. Databases of isotopic ages of igneous 

rocks for Indonesia and for Papua New Guinea compiled by 

the Southeast Asia Research Group provided additional information on locations, ages, and lithologies of permissive rocks 

(Malaihollo and others, 2002).

Late Miocene to Pliocene intrusions associated with porphyry copper mineralization crop out as hypabyssal intrusive 

bodies and small dikes and plugs; many are too small to show 

on 1:250,000-scale maps.

No regional-scale aeromagnetic data were available to the 

assessment team. However, the geophysical signature of the 

Grasberg deposit was modeled by Hoschke (2008): the deposit 

produces a strong discrete magnetic anomaly of less than 

2,000nT (helicopter magnetic surveys), which is attributed to 

the high (7 percent) magnetite content of quartz stockworks 
Appendix M—Tract 142pCu7203 199

in the approximately 600-m-diameter orebody; the Grasberg 

intrusions have a vertical extent of more than 1 km.

The final tract boundaries were established by GIS 

processing and editing. The processing approximates manual 

delineation of tracts but is rapid and reproducible. The processing steps included (1) unioning of buffered permissive 

map units and other polygon features that comprise the framework of the tract; (2) aggregating unioned polygons using 

an aggregation distance of 15 km and a minimum hole size 

of 1,000 km2; (3) manually aggregating and adjusting tract 

areas; and (4) smoothing polygons using an algorithm (PAEK, 

polynomial approximation with exponential kernel) with a 

tolerance of 1 km. Preliminary tracts were cleaned to remove 

necking and thinning introduced by processing and were 

compared with source maps to ensure that original permissive 

boundaries and buffer distances were honored. Regional and 

local mineral occurrence, geochemical, and isotopic age data 

were plotted and used to constrain or expand tract boundaries. 

Tract boundaries were clipped at shorelines (U.S. Department 

of State, 2009).

The tract consists of three discrete areas of permissive 

igneous rocks of late Miocene to Pliocene age (fig. M1). Areas 

between the map-based parts of the tract, as indicated by the 

highlands areas shown in shaded relief on figure M2, may 

conceal unmapped permissive rocks. Access to aeromagnetic 

data for the entire study area would help identify potential 

shallow intrusions that could host porphyry copper deposits. 

In adjacent areas of the magmatic belt in Papua New Guinea 

(tract 009pCu7203), magnetic data show that the intrusions 

tend to be small and isolated.

A. Bird’s Head.—Although no late-Miocene-Pliocene 

igneous rocks are shown on the 1:250,000-scale geologic 

maps of the Bird’s Head, the team included a permissive area 

in the Aisasjur River region as part of the tract based on (1) 

locations of andesite porphyry dikes dated at 2.23 and 2.92 Ma 

(K-Ar on biotite) reported in Malaihollo and others (2002), 

based on data in Bladon (1988) and (2) the approximate extent 

of the Arc Exploration, Ltd., Aisasjur exploration area. The 

original exploration area covered about 61,000 hectares and 

targeted blind porphyry copper-gold deposits underlying epithermal gold occurrences, where drilling documented diorite 

porphyry within 1 km of the surface (Arc Exploration, Ltd., 

2009). As of July 2010, an alliance between Arc Exploration, 

Ltd., and Anglo America held exploration tenements covering 

about 1,000 km2

. Epithermal gold mineralization overprints 

low-grade porphyry copper mineralization encountered at 

depth. Deeper parts of the system host bornite in porphyryrelated pyrite-pyrrhotite-chalcopyrite veins (Arc Exploration, 

Ltd., 2010).

The permissive area lies south of the Sorong Fault and 

west of the Ransiki Fault, within Paleozoic sedimentary rocks, 

as shown on the 1:1,000,000-scale geologic map of Dow and 

others (1986). The permissive area may be much larger than 

shown, but the team had no basis for further delineation.

B. Nabire.—The Nabire area outlines the Nabire Volcanics on the southeastern edge of Cenderawasih Bay. The 

Nabire Volcanics are described as alkali basalt, andesite, and 

microdiorite intrusions. Bladon (1988) reported a K-Ar age of 

5.62± 0.25 Ma on hornblende from slightly altered andesite 

in the tract area. A sample of Nabire Volcanics from an area 

165 km northwest of the Minjauh volcanic field (area C) has 

an extreme isotopic Nd signature (εNd=–3.4) relative to other 

igneous rocks in the western part of the Central Ranges of 

central Irian Jaya (εNd<–10). The Nabire sample lies along 

the trend of lead isotopic signatures for the Minjauh volcanic 

field and Gunung Bijih (Grasberg area) of area C and has an 

intermediate isotopic initial Sr signature (87Sr/86Sri=0.70739) 

relative to those two areas (Housh and McMahon, 2000).

Table M2. Map units that define tract 142pCu7203, Western Medial New Guinea Magmatic Belt—Indonesia.

[Map unit, age range, and principal lighologies are based on a digital compilation of geologic maps of Indonesia (Directorate of Mineral Resources and Inventory, 

2004a) and on scanned and rectified 1:250,000-scale quadrangle maps of Irian Jaya. Map symbols, lithology, and age ranges for Indonesia are based on 1:250,000-

scale geologic maps]

Map unit Map symbol Lithology Age range

Intrusive rocks

Pariri Diorite Tmpp Diorite, quartz diorite Miocene-Pliocene?

Timepa Monzonite Tmpt Quartz diorite, monzonite, andesite Miocene-Pliocene

Ilaga intrusions Tpi Diorite, monzonite, quartz monzonite stock, dikes, sill Pliocene

Volcanic rocks

Nabire Volcanics Tmpn Alkali basalt, microdiorite intrusions Miocene-Pliocene

Volcanics Tpv Lamprophyres Pliocene
200 Porphyry Copper Assessment of Southeast Asia and Melanesia

C. Grasberg area, southeastern West Papua and western 

Papua provinces, Indonesia.—The Grasberg area includes late 

Miocene and Pliocene intrusive rocks (<7 Ma) south of the 

Weyland thrust and extending eastwards across the western 

parts of the Central Highlands. The southern boundary of 

the tract area follows the approximate trace of a thrust fault 

along the southern margin of the Papuan Fold Belt, along the 

northern edge of the stable platform of southern New Guinea 

Island (fig. 7 of main report). The eastern boundary of the tract 

is placed along a buffer around the easternmost exposures of 

Ilaga intrusions and andesites, and is partly coincident with 

northeast-trending fault corridors. This area is coincident 

with the western limit of a 300-km-wide “gap” in Neogene 

intrusions that extends to the Papua New Guinea border; the 

gap area is lower in elevation (generally <2,000 m) than the 

Grasberg area (Cloos and others 2005).

The Grasberg area of the tract includes the mapped extent 

of the Pariri Diorite, Timepa Monzonite, diorite, and quartz 

diorite (Ilaga intrusions), as well as calc-alkaline, shoshonitic, 

and ultrapotassic lamprophyric rocks of the Minjauh volcanic field and hypabyssal intrusive bodies associated with 

the Gunung Bijih mining district (Grasberg, Ertsberg) based 

on localities reported by Housh and McMahon (2000) and 

McDowell and others (1996). The 5–7 Ma Minjauh volcanic 

field, northwest of Grasberg, includes shallow intrusive complexes. These rocks were emplaced after the collision of the 

older Miocene Maramuni Arc, which lies to the north. Genesis 

of these rocks may be related to jamming of a north-dipping 

subduction zone at about 7–8 Ma that resulted in partial 

delamination of lithospheric mantle below the continental 

margin of Australia, and resulted in asthenospheric upwelling (Housh and McMahon, 2000; Cloos and others, 2005). 

The collision-related rocks of the western Central Ranges are 

isotopically distinct from other Neogene igneous suites in 

the region (Banda Arc, New Britain, Porgera area, southeastern Papua New Guinea) by virtue of their unradiogenic Nd 

(εNd=−3.4 to −22.0), radiogenic initial Sr (87Sr/86Sri=0.7058 to 

0.71355) and variable Pb isotopic signatures, which led Housh 

and McMahon (2000) to propose that the source magmas represented mixtures of depleted mantle melts, ancient enriched 

mantle, and Proterozoic or Archean lower crust. The 3.0–2.9 

Ma Komopa intrusions, west of the Minjauh volcanic field, 

include hypabyssal quartz monzodiorites, granodiorites, and 

monzogranites characterized by shoshonitic chemistry with 

high LILE and LREE contents, low concentrations of Nb, Ta, 

and Ti, 87Sr/86Sri=0.7077, and unradiogenic Nd (εNd ~−8.3); 

geochemical similarities with igneous rocks in the Minjauh 

and Ertsberg area suggest that all are related to collisional 

delamination processes at the northern edge of Australian 

continental lithosphere (Jackson, 2010).

Approximately 16 small (a few to several hundred m2) 

hypabyssal Pliocene intrusions have been identified in the 

Gunung Bijih mining district; the largest intrusions (a few km2

in outcrop area) are the Erstberg Diorite (3.00± 0.08 Ma) and 

the Grasberg Igneous Complex (2.6–4.4 Ma), which is located 

about 3 km north-northwest of Erstberg (Porter Geoconsultancy, 2001). According to Porter Geoconsultancy’s 2001 

report, no volcanic deposits extend beyond the mapped limits 

of the Grasberg Intrusive Complex. Corbett (2009) noted that 

quality porphyry copper deposits, including Grasberg, do not 

always occur in association with related volcanic rocks, and 

that volatiles may concentrate in apophyses localized along 

major structures or adjacent dilatant arc-parallel or arc-normal 

structures. The Erstberg mining district experienced two stages 

of deformation: (1) kilometer-scale folds with thrust faults 

and strike slip tear faults between about 12 and 4 Ma and (2) 

development of a left-lateral strike-slip fault system starting 

about 4 Ma that generated northwest-trending fault zones that 

facilitated emplacement of the Grasberg Igneous Complex in a 

2-km-wide pull-apart zone (Sapile and Cloos, 2004).

Known Deposits

The Grasberg supergiant deposit (4,000 Mt at 0.6 percent 

copper, 0.64 g/t gold; table M3) is the largest copper-gold 

Table M3. Identified porphyry copper resources in tract 142pCu7203, Western Medial New Guinea Magmatic Belt—Indonesia.

[Ma, million years; Mt, million metric tons; t, metric ton; %, percent; g/t, gram per metric ton; Cu-Au subtype, deposits that have Au/Mo ratios >30 or average Au 

grades >0.2 g/t. Contained Cu in metric tons is computed as tonnage (Mt × 1,000,000) × Cu grade (%); n.d., no data]

Name Latitude Longitude Subtype Age 

(Ma)

Tonnage 

(Mt)

Cu 

(%)

Mo 

(%)

Au 

(g/t)

Ag 

(g/t)

Contained 

Cu (t) Reference

Grasberg -4.046 137.114 Cu-Au 3 4,000 0.60 n.d. 0.64 2 24,000,000 Anonymous (2004), Cloos (1997), 

Cloos and Housh (2008), EconomouEliopoulos and others (2001), FreeportMcMoRanCopper and Gold, Inc. (1999, 

2006, 2009, 2010), MacDonald and 

Arnold (1994), MacDonald and Arnold 

(1995), McDowell and others (1996), 

Meinert and others (1997), Mertig 

and others (1994), Paterson and Cloos 

(2005a,b), Pollard and Taylor, (2002), 

Potter (1996), Singer and others (2008)
Appendix M—Tract 142pCu7203 201

porphyry deposit in the world and the largest porphyry deposit 

in southeast Asia. The Grasberg area includes the Ertsberg, 

Gunung Bijih, and Kusing Liar deposits and prospects. Mineralization proximal to Grasberg is copper-gold skarn. In 2009, 

mine operations included an open pit which is expected to 

be mined until 2015 or 2016; underground mining, expected 

to last until 2027 or later; and a mill complex. The mine is 

located on a 10,000 hectare block of land (Block A). Gold 

and copper production declined in 2008 because of lower ore 

grades (Kuo, 2010).

The Grasberg orebody is composed of multistage, nested 

orebodies: the Dalam Diatreme at 800 m depth; the Main 

Grasberg Stock; and the late-stage, weakly mineralized South 

Kali dikes. Pollard and Taylor (2005) showed that the Grasberg Igneous Complex represents several cycles of intrusion 

and hydrothermal alteration, based on 40Ar/39Ar studies on 

magmatic and hydrothermal micas that document a main stage 

of intrusion and alteration at 3.33± 0.12 Ma, intrusion of the 

Kali quartz monzonite porphyry dikes at 3.03± 0.03 and 3.01± 

0.06 Ma, and post-Kali intrusions and alteration as young as 

3.01± 0.06. They concluded that each cycle lasted 0.1 million 

years or less, and that the huge size of the deposit could not 

be explained by a prolonged period of mineralization. Igneous rocks associated with the Grasberg porphyry copper-gold 

deposit include Pliocene andesite breccia, breccia, diorite, 

diorite porphyry, monzodiorite porphyry, and monzonite 

porphyry. Country rocks are Paleozoic and Mesozoic black 

shale, dolomite, limestone, quartzite, sandstone, and siltstone. 

Porphyry copper-gold mineralization and associated skarn is 

Pliocene (~3 Ma) (McDowell and others 1996; Paterson and 

Cloos, 2005a,b). Grasberg is an unusually high-grade copper- and gold-rich porphyry copper deposit, with a consistent 

Cu:Au=10,000:1; gold is associated with chalcopyrite, which 

may replace bornite, and likely exsolved from copper sulfides 

(Kyle and others, 2008).

Mineralized zones extend from the surface (4,200 m elevation) to 2,700 m. Recent development activity at Grasberg 

is focused on transitioning from open pit to block-cave mining 

in 2016 (Freeport-McMoRan Copper and Gold, Inc., 2010) to 

exploit deeper skarn orebodies (Grasberg block cave, Big Gossan, Deep MLZ, and Kucing Liar). Reserves and resources for 

the deposits (porphyry and skarn) in Grasberg block A are as 

follows (March, 2010 data): total measured and indicated and 

inferred resources of 2,863,000,000 metric tons averaging 0.56 

percent copper, 0.51 g/t gold, and 3.30 g/t silver; proven and 

probable open pit and underground reserves of 2,590,000,000 

metric tons averaging 1.00 percent copper, 0.86 g/t gold, and 

4.18 g/t silver (Freeport-McMoRan Copper and Gold, Inc., 

2010). Most of the remaining ore is in skarn.

Prospects, Mineral Occurrences, and Related 

Deposit Types

Porphyry copper prospects and epithermal deposits or 

prospect areas that may be associated with porphyry copper 

deposits at depth are listed in table M4. The main prospect 

areas are discussed from west to east across the magmatic belt 

that defines the tract.

At Arc Exploration’s Aisasjur project in the Bird’s Head 

(area A), quartz-magnetite-chalcopyrite stockworks were identified in drill-hole intercepts (5 holes to approximately 700 m 

depth) in potassically altered diorite porphyry intrusions and 

intrusive breccias. Mineralized intercepts containing copper 

(0.17, 0.26 percent) and gold (0.4–1.25 g/t) are reported. Other 

copper and gold occurrences, prospects, and stream-sediment 

anomalies are shown on the 1:250,000-scale geologic maps 

of southwestern Papua province, Indonesia within the tract, 

including sites that were drilled with reported gold, copper, and molybdenum (Indonesian Directorate of Mineral 

Resources and Inventory, proprietary data, 2004b).

The Komopa-Dawagu area was drilled (301 holes) by 

the Nabire Bakti Joint Venture in the 1990s (Freeport McMoRan, 1999). The Komopa prospect (area C) has an in-place 

estimated geologic resource of approximately 363 Mt at 0.5 

percent copper equivalent, with a cutoff grade of 0.3 percent 

copper equivalent. The Dawagu prospect estimated resource is 

372 Mt at 0.5 percent copper equivalent, with a cutoff grade of 

0.3 percent copper equivalent.

A number of porphyry copper-gold occurrences and associated deposits, such as the copper-gold skarns and epithermal 

deposits, are proximal to the main Grasberg porphyry orebody 

(John and others, 2010). Proximal deposits are mined from the 

same facilities as the main deposit and are considered part of 

the Grasberg ore system (Kamitani and Naito,1988).

Area C includes Nickelore Limited’s (2009) Papua Gold/

Copper exploration project, located 45 km northwest of Grasberg, as well as 13 prospects for gold, copper, and magnetite 

skarn; some of these have been partially explored by drilling 

(<100 m Winkie drilling; at least 1 prospect to 600 m depth). 

Assay results report copper, typically in the range of about 

0.1–1 percent copper, ppb to ppm concentrations of gold plus 

molybdenum or lead.

Exploration History

The Ertsberg (Gunung Bijih) mining district was discovered by an expedition in 1936, and “rediscovered” by mineral 

exploration in 1960. Mining of the skarn deposits started in the 

1970s, and the Ertsberg skarn body is mined out. The Erstberg 

skarn orebodies (Ertsberg, Ertsberg East, and Dom) formed 

within and at limestone contacts of the 3.2 Ma Erstberg diorite. Exploration drilling in 2000 identified porphyry coppergold mineralization within the 3.2 Ma Ertsberg diorite, with 

potential resources on the order of 100 to 200 million metric 

tons that could be mined by open-pit or block-caving methods.

The Grasberg porphyry copper-gold deposit, located 

about 3 km north of Ertsberg, was discovered by exploratory 

drilling in 1988, and open-pit mining started in 1990. There 

has been extensive modern exploration since the 1960s around 

Grasberg-Ertsberg and, to a lesser extent, in and around the 

surrounding skarn and epithermal occurrences in the western 

parts of the tract. This exploration has included helicopter 
202 Porphyry Copper Assessment of Southeast Asia and Melanesia

Table M4. Significant prospects and occurrences in tract 142pCu7203, Western Medial New Guinea Magmatic Belt—Indonesia.

[Ages all assumed to be late Miocene to Pliocene based on associated map units. Rank 4=prospect in global database of Singer and others (2008) or >16,000 

t contained copper; Rank 3=drilled, with >20 m of 0.2% or more Cu. Rank 2=drilled or trenched with <20 m of 0.2% Cu or <0.2% Cu, or past or ongoing exploration. Rank 1=copper occurrence that may be related to porphyry-type mineralization based on stream sediment or magnetic anomaly or location along structural 

trend. %, percent; g/t, grams per metric ton; km, kilometers; m, meters; ppm, parts per million; Mt, million metric tons]

Name Latitude Longitude Comments Reference Rank

A, Bird’s Head Area

Aisasjur Gold/

Copper Project

-1.226 132.854 Blind porphyry copper-gold target; drilling (13 holes) 

intersected low-grade epithermal Au-As-Sb and at depth 

(from 712 m downhole), potasically altered diorite porphyry 

with quartz-magnetite-chalcopyrite stockwork and breccia; 

disseminated chalcopyrite and bornite; also magnetitedestructive argillic alteration. Drill targets based on magnetic 

anomalies. Drilled intercepts: 13 m at 0.21% Cu, 0.51 g/t 

Au from 561 m downhole; 192.8 m at 0.13% Cu, 0.19 g/t 

Au from 698.2 m downhole. Age based on reported ages for 

associated igneous rock (SEARG database). Location based 

on exploration maps. 

Arc Exploration (2009, 2010) 3

C, Grasberg Area

Komopa 

prospect

-3.799 136.474 In place estimated geologic resource ~ 363 Mt at 0.5% 

copper equivalent with a cutoff grade of 0.3% copper 

equivalent. Komopa Porphyry is described as a subvolcanic 

intrusion with a well-defined,circular, hydrothermal alteration 

system. Explored as part of Block II of the Nabire Bakti Joint 

Venture west of Grasberg. Copper-gold mineralized zone 

1.5 by 0.5 km in area. Partial drill results reported in 1999 

included 10 holes with >10 m intercepts (12–384 m) of 0.39 

to 1.16 % Cu, 0.10 to 0.718 g/t Au. Age 2.9 to 3.9 Ma.

Gold Fields Limited (2004), 

Directorate of Mineral 

Resources and Inventory 

(2004b)

4

Dawagu 

prospect

-3.771 136.551 In place estimated geologic resource ~ 372 Mt at 0.5% 

copper equivalent with a cutoff grade of 0.3% copper 

equivalent. The Dawagu prospect includes several 

exploration targets (Gold Fields Limited, 2004): a central 

porphyry stockwork, skarns (open to the east in New Guinea 

Limestone), and epithermal -style mineralization in overlying 

clastics. 

Directorate of Mineral 

Resources and Inventory 

(2004b)

4

Ikerar prospect -3.978 136.119 Winkie drilling 39–41m (Au), 35–50m (Cu, Mo); contents: 

110 ppb Au max, 637.5 ppm Cu, 59.6 ppm Mo.

Directorate of Mineral 

Resources and Inventory 

(2004b)

2

Wabu skarn -3.671 137.047 Major Au-Cu skarn prospect ~33 km N of Grasberg. Upper 

Miocene skarn and porphyry in the footwall of the Derewo 

fault. Skarn developed in New Guinea limestone along a 

6-km strike length along a contact with a monzonite-diorite 

intrusive complex. 

Allen and others (1998) 2

Papua Gold 

and Copper 

project

-3.671 136.500 Raw prospect area (91 km2) located 45 km NW of Grasberg; 

target is porphyry copper-gold and skarn based on ringstructure targets on satellite imagery and photointerpretation 

of geology; previously unexplored area.

Nickelore Limited (2009) 1
Appendix M—Tract 142pCu7203 203

Table M4. Significant prospects and occurrences in tract 142pCu7203, Western Medial New Guinea Magmatic Belt—Indonesia.—

Continued

Name Latitude Longitude Comments Reference Rank

C, Grasberg Area

Pogatadi “C” and 

“D” prospects

-3.932 136.121 Rock sample 0.35–1.2% Cu; stream sediments 

700–959 ppm Cu.

Directorate of Mineral Resources 

and Inventory (2004b)

1

Pogatadi “B” 

prospect

-3.903 136.145 Minor prospect, soil sample: 500–1,260 ppm Cu. Directorate of Mineral Resources 

and Inventory (2004b)

1

Mogo-mogo 

prospect

-3.873 136.183 Minor prospect; rock sample vein magnetite skarn: 

0.25 ppm Au; 16.6 ppm Au; 5,500 ppm Cu.

Directorate of Mineral Resources 

and Inventory (2004b), Nickelore 

Limited (2009)

1

Obano prospect -3.889 136.178 Minor prospect; soil 2.97 ppm Au; rock sample, 

1.11% Cu, 2.33 ppm Au.

Directorate of Mineral Resources 

and Inventory (2004b)

1

Pogatadi “E” 

prospect

-3.906 136.120 Stream sediment: 0.24 ppm Au, 49 ppm Cu; rock 

sample: 0.07 ppm Au.

Directorate of Mineral Resources 

and Inventory (2004b)

1

Tango One 

prospect

-4.085 137.039 Stream sediment and rock sample with Au and Cu. Directorate of Mineral Resources 

and Inventory (2004b)

1
204 Porphyry Copper Assessment of Southeast Asia and Melanesia

and foot regional geochemical exploration including streamsediment sampling and local airborne and ground-geophysical 

surveys. Some of the more prominent prospects were trenched 

and drilled. Freeport-McMoRan Copper and Gold, Inc., 

continued exploration in their original 24,700-acre concession 

area (Block A) and adjacent 1.6 million-acre area (Block B) 

in the 1990s. Security issues and regulatory issues associated 

with mining in forest preservation areas curtailed exploration 

activities outside of Block A in 2006 (Freeport-McMoRan 

Copper and Gold, Inc., 2006). In 2008, Rio Tinto reported 

that exploration was being done on about 200,000 hectares 

in Block B and in an additional 690,000 hectares outside of 

Blocks A and B in joint ventures.

Exploration drilling also occurred within a 1-million-acre 

concession area by P.T. Nabire Bakti Mining, which includes 

the Komopa porphyry copper-gold prospect located 75 km 

west of Grasberg (Business Wire, 1999). Nickleore Limited 

(2009) is exploring for large gold-copper porphyry and skarn 

systems based on observations of circular structures observed 

on satellite imagery at the Papua Project, an approximately 91 

km2

 area located about 45 km northwest of Grasberg.

As of 2008, areas around Grasberg and the Aisasjur area 

of the Bird’s Head were being explored. Exploration focus 

is on circular, topographic high, historically partly explored 

prospects that indicated copper and gold, alluvial gold, streamsediment geochemical anomalies, geophysical anomalies, and 

northeast-structural trends and lineaments, especially in areas 

between known mineralized centers along the same structural 

corridors. Most areas within the tract are remote, mountainous, 

highly vegetated, and in places of recent political and social 

unrest. Therefore, all parts of the tract may not be thoroughly 

evaluated (see van Leeuwen, 1994; Cloos, 1997).

Sources of Information

Principal sources of information used by the assessment 

team for delineation of tract 142pCu7203 are listed in table 

M5.

Grade and Tonnage Model Selection

Grasberg, the only deposit with identified resources 

within the tract, is a porphyry copper-gold deposit. Preliminary data on prospects and regional characteristics indicate 

that a copper-gold porphyry model is appropriate for the 

tract. ANOVA tests comparing the grade and tonnage data for 

Grasberg with general porphyry copper and copper-gold subtype models support either model (table 6 of main report). In 

terms of tonnage and contained copper, Grasberg is the largest 

porphyry copper deposit in Southeast Asia. Smaller deposits 

occur in the eastern part of the same magmatic belt (tract 

009pCu7203). Therefore, the team concluded that the global 

copper-gold model, with a median deposit size of 200 million 

metric tons of ore, was appropriate for simulation undiscovered resources associated with the tract.

Table M5. Principal sources of information used for tract 142pCu7203, Western Medial New Guinea Magmatic Belt—Indonesia. 

[CCOP, Coordinating Committee for Coastal and Offshore Geoscience Programmes in East and Southeast Asia; NA, not applicable]

Theme Name or title Scale Citation

Geology Digital geologic map of East and Southeast Asia 1:2,000,000 CCOP and Geological Survey of Japan (1997)

Digital geologic map of Indonesia 1;1,000,000 Directorate of Mineral Resources and Inventory (2004a)

Systematic geologic map, Indonesia, map nos. 

2914, 3111, 3112, 3211, 3212

1:250,000 Geological Research and Development Centre (1987–2000) 

Geologic map of Irian Jaya, Indonesia 1:1,000,000 Dow and others (1986)

Mineral

occurrences

Porphyry copper deposits of the world: database, 

map, and grade and tonnage models

NA Singer and others (2008)

Digital mineral occurrence database NA Directorate of Mineral Resources and Inventory (2004b)

MRDS database NA U.S. Geological Survey (2005)

Exploration USGS Minerals Yearbooks, Company Web sites NA Kuo (2010), Various (see references in table M3)
Appendix M—Tract 142pCu7203 205

Estimate of the Number of Undiscovered Deposits

Rationale for the Estimate

Grasberg is the only deposit in production within the 

tract. The tract includes five partly explored porphyry copper 

prospects and seven minor prospects and occurrences that may 

be related to porphyry copper systems (table M4). In addition, 

copper is noted in most of the gold occurrences (11) within the 

tract. The team estimated a 90-percent chance of one or more 

undiscovered porphyry deposits in the tract (table M6) based 

on the identification of porphyry-style alteration and geochemical anomalies associated with permissive, Pliocene-age igneous rocks in the underexplored Bird’s Head area, partly drilled 

prospects with indications of porphyry characteristics near 

Grasberg, exploration at the Komopa prospect, and increasing 

recognition of geochemical similarities between the rocks at 

Grasberg and elsewhere within the tract. The team estimated 

a 50-percent chance of three or more deposits, based on the 

possibility that further exploration could establish resources 

at half of the known, or future, prospect areas. Much of the 

Grasberg-Ertsberg area is held by major mining companies 

in joint ventures who are focused on extensions of identified 

resources. Exploration outside of their work area has been 

hampered by political, social, and environmental concerns in 

recent years. There may be proprietary data documenting the 

likelihood of additional deposits, or the lack thereof, in the 

tract area. Based on the available data, the team estimated a 

10-percent chance of 10 or more deposits in the tract. Magnetic data for adjacent areas within the same magmatic belt 

in Papua New Guinea show discrete, small, circular magnetic 

highs similar to those described for the world-class Grasberg 

deposit and the exploration target at the Papua project northwest of Grasberg.

Probabilistic Assessment Simulation 

Results

Undiscovered resources for the tract were estimated by 

combining consensus estimates for numbers of undiscovered 

porphyry copper deposits with the porphyry copper-gold 

model of Singer and others (2008) using the EMINERS 

program (Root and others, 1992; Bawiec and Spanski, 2012; 

Duval, 2012). Selected simulation results are reported in table 

Table M6. Undiscovered deposit estimates, deposit numbers, tract area, and deposit density for tract 142pCu7203, Western Medial 

New Guinea Magmatic Belt—Indonesia.

[NXX, estimated number of deposits associated with the xxth percentile; Nund, expected number of undiscovered deposits; s, standard deviation; Cv%, coefficient of 

variance; Nknown, number of known deposits in the tract that are included in the grade and tonnage model; Ntotal, total of expected number of deposits plus known 

deposits; km2, area of permissive tract in square kilometers; Ntotal/100k km2, deposit density reported as the total number of deposits per km2. Nund, s, and Cv% are 

calculated using a regression equation (Singer and Menzie, 2005)]

 Consensus undiscovered deposit estimates Summary statistics Tract area 

(km2

)

Deposit density 

(Ntotal/100k km2) N90 N50 N10 N05 N01 Nund s Cv% Nknown Ntotal

1 3 10 10 10 4.4 3.4 77 1 5.4 13,270 41

Table M7. Results of Monte Carlo simulations of undiscovered resources for tract 142pCu7203, Western Medial New Guinea 

Magmatic Belt—Indonesia.

[Cu, copper; Mo, molybdenum; Au, gold; and Ag, silver; in metric tons; Rock, in million metric tons]

Material

Probability of at least the indicated amount Probability of

0.95 0.9 0.5 0.1 0.05 Mean Mean or 

greater

None

Cu 0 310,000 6,500,000 36,000,000 54,000,000 14,000,000 0.31 0.06

Mo 0 0 15,000 230,000 420,000 80,000 0.24 0.3

Au 0 32 560 2,700 3,700 1,000 0.34 0.06

Ag 0 0 1,200 11,000 21,000 4,500 0.22 0.22

Rock 0 74 1,400 7,600 11,000 2,800 0.33 0.06
206 Porphyry Copper Assessment of Southeast Asia and Melanesia

M7. Results of the Monte Carlo simulation are presented as a 

cumulative frequency plot (fig. M3). The cumulative frequency 

plot shows the estimated resource amounts associated with 

cumulative probabilities of occurrence, as well as the mean, 

for each commodity and for total mineralized rock. The mean 

amount of copper contained in undiscovered porphyry copper 

deposits within the tract (14 Mt) is less than the identified 

resources at Grasberg (24 Mt). Note that in terms of contained 

copper, Grasberg is the largest known porphyry copper deposit 

in Southeast Asia. Estimated resources in undiscovered 

deposits are modeled using a global grade-tonnage model with 

the assumption that undiscovered deposits will be like those in 

the model (some large, some small).

References Cited

Allen, J.M., Aslund, T., Sunyoto, W., and Soebari, L., 1998, The 

Wabu gold skarn, Irian Jaya, Indonesia: Geological Association 

of Canada, Abstracts with Programs, v. 23, p. A3–4.

Anonymous, 2004, Freeport drills more copper and gold at 

Grasberg: Mining Journal, v. May 7, p. 9.

Arc Exploration, 2009, March 2009 quarter activities 

report: accessed February 10, 2010, at http://www.

arcexploration,com.au/March2009Quarterly.html.

Arc Exploration, 2010, ARX=Anglo America, strategic alliance 

extended: ASX announcement dated July 29, 2010.

Bawiec, W.J., and Spanski, G.T., 2012, Quick-start guide for 

version 3.0 of EMINERS—Economic Mineral Resource 

Simulator: U.S. Geological Survey Open-File Report 

2009–1057, 26 p., accessed June 30, 2012, at http://pubs.

usgs.gov/of/2009/1057. (This report supplements USGS 

OFR 2004–1344.)

Berger, B.R., Ayuso, R.A., Wynn, J.C., and Seal, R.R., 

2008, Preliminary model of porphyry copper deposits: 

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134° E 136° E 138° E

2° S4° S Grasberg

Wabu skarn

Obano prospect

Ikerar prospect

Dawagu prospect

Tango One prospect

Mogo-mogo prospect

Papua Gold and Copper project

Aisasjur Gold/Copper Project

Pogatadi "C" and "D" prospects

Pogatadi “E” prospect

Pogatadi “B” prospect

Komopa prospect Cenderawasih Bay

 Arafura Sea PACIFIC OCEAN INDONESIA

120°E 

20°N

0°

20°S

AU

PH

Political boundary source: U.S. Department of State (2009)Projection: Asia South Albers Equal Area Conic;Central meridian 134° E; latitude of origin 15° S

0 50 100 150 200 KILOMETERS

0 50 100 MILES

EX

OtheAsse142pPorp

Porpprostrac

A, Bird’s Head area

B, Nabire area

C, Grasberg area

Figure M1. Map showing tract location, known deposits, and significant porphyry copper prospects for tract 142pCu7203, Western Medial New GIndonesia. ID, Indonesia; PH, Philippines; PG, Papua New Guinea.
( ( (

(

( ( ( (

(

( ( ( ( ( ( 

( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( (

( (

( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( 

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INDONESIA Grasberg Wabu skarn Tango One prospect Papua Gold and Copper project Aisasjur Gold/Copper Project Komopa prospect Dawagu prospect Obano prospect Ikerar prospect Mogo-mogo prospect Pogatadi "C" and "D" prospects Pogatadi “E” prospect Pogatadi “B” prospect Cenderawasih Bay Arafura Sea PACIFIC OCEAN Seram Sea 134° E 138° E 0° 2° S 4° S Base from ESRI ArcGIS Online (2009) World Shaded Relief Political boundary source: U.S. Department of State (2009) Projection: Asia South Albers Equal Area Conic; Central meridian 134° E; latitude of origin 15° S 0 50 100 150 200 KILOMETERS 0 50 100 MILES E

Ass 1

Por

PerPer

( ( Sub

Por

Str

SORONG FAULT RANSIKI FAULT A, Bird’s Head area B, Nabire areaC, Grasberg area Figure M2. Map showing the distribution of permissive igneous rocks for tract 142pCu7203, Western Medial New Guinea Magmatic Belt—Indon
Appendix M—Tract 142pCu7203 211

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

Probability

0.01 0.1 1 10 100 1K 10K 100K 1M 10M 100M 1B 10B 100B

Material, metric tons

Mean Cu

Mean Mo

Mean Au

Mean Ag

Mean Rock

Cu

Mo

Au

Ag

Rock

Mean Cu

Mean Mo

Mean Au

Mean Ag

Mean Rock

EXPLANATION

Figure M3. Cumulative frequency plot showing the results of Monte Carlo computer simulation of undiscovered resources in tract 

142pCu7203, Western Medial New Guinea Magmatic Belt—Indonesia. k, thousands; M, millions; B, billions; Tr, trillions.
212 Porphyry Copper Assessment of Southeast Asia and Melanesia

Appendix N. Porphyry Copper Assessment for Tract 142pCu7204, 

Rotanburg-Taritatua Area—Indonesia

By Jane M. Hammarstrom1, Bambang Tjahjono Setiabudi2, Dwi Nugrono Sunuhadi2, Gilpin R. Robinson, Jr.1, 

Connie L. Dicken1

, Steve Ludington3, Arthur A. Bookstrom4, and Michael L. Zientek4, with contributions from 

Gwaibo Kopi5

 and Dennis P. Cox3

Deposit Type Assessed: Porphyry copper

Descriptive model: Porphyry copper (Berger and others, 2008; John and others, 2010)

A permissive tract is delineated based on permissive rock types depicted on 1:250,000-scale geologic maps. Insufficient 

information was available for a probabilistic assessment of the tract area. Summary information is listed in table N1.

Table N1. Summary of selected information for tract 142pCu7204, Rotanburg-Taritatua Area—Indonesia. 

[km, kilometers; km2, square kilometers; t, metric tons; n.d., no data] 

Date of assessment Assessment depth (km) Tract area (km2) Known copper resources (t)

February 2010 1 9,370 n.d.

Location

The tract includes the Central Highlands of New Guinea Island and parts of the Indonesian provinces of West Papua and 

Papua, formerly known as Irian Jaya (fig. N1).

Geologic Feature Assessed

Late Miocene to Pliocene-Pleistocene intrusive rocks.

Delineation of the Permissive Tract

Tectonic Setting

Tract 142pCu7204 outlines exposed segments of the late Miocene and Pliocene to Pleistocene intrusive rocks in the Indonesian provinces of western New Guinea Island in an area north of the Direwo Fault, the boundary between the fold belt and 

1

U.S. Geological Survey, Reston, Virginia, United States.

2

Center for Geological Resources, Geological Agency of Indonesia, West Java, Indonesia.

3

U.S. Geological Survey, Menlo Park, California, United States.

4

U.S. Geological Survey, Spokane, Washington, United States.

5

Mineral Resources Authority, Papua New Guinea.
Appendix N—Tract 142pCu7204 213

the mobile belt, and east of the Central Ophiolite Belt (COB 

on fig. 7). The relationship of these rocks to the Medial New 

Guinea magmatic belt is unclear, although 1:250,000-scale 

geologic maps of the area ascribe them to some of the same 

map units that characterize tract 142pCu7203 near Grasberg, 

such as the Timepa diorite (table N2).

This area is questionable as a permissive area for 

undiscovered porphyry copper deposits. The assessment team 

included it because an east-west-trending belt of rocks of 

apparently appropriate age and lithology extends from an area 

about 50 km north of the Grasberg mine area to the Papua 

New Guinea border.

on photointerpretation in assignment of geologic map units 

indicate that additional data are needed to assess this part of 

the Central Highlands. The western and eastern boundaries 

of this section of the tract approximately align with orogentransverse lineaments.

The tract was constructed in a GIS using a 1:500,000-

scale digital map of igneous rocks of Indonesia (Directorate 

of Mineral Resources, 2004a), 1:250,000-scale geologic 

maps of Indonesia, and the 1:1,000,000-scale geologic map 

of Irian Jaya (Dow and others, 1986). In addition, maps 

and figures showing major faults, lineaments, and tectonic 

divisions of New Guinea Island by Garwin and others 

(2005), Hill and others (2002), and Quarles van Ufford and 

Cloos (2005) were used.

Using GIS tools, a 5-km buffer was applied around 

mapped igneous contacts of permissive lithologies to 

account for spatial uncertainty in digitized geology and for 

the possibility of greater extent of permissive rocks within 

a kilometer of the surface. The buffered map units were 

aggregated using GIS processing tools with a 15 km distance 

to group closely spaced permissive areas, which were then 

edited to honor fault boundaries, merge and include other 

areas of known igneous rocks of appropriate age and lithology. 

The final tract boundaries were established by GIS processing 

and editing. The processing approximates manual delineation 

of tracts but is rapid and reproducible. The processing steps 

included (1) unioning of buffered permissive map units and 

other polygon features that comprise the framework of the 

tract; (2) aggregating unioned polygons using an aggregation 

distance of 15 km and a minimum hole size of 1,000 km2

; 

(3) manually aggregating and adjusting tract areas; and (4) 

smoothing polygons with a tolerance of 1 km. Preliminary 

tracts were cleaned to remove necking and thinning introduced 

Table N2. Map units that define tract 142pCu7204, Rotanburg-Taritatua Area—Indonesia. 

[Map unit, age range, and principal lithologies are based on a digital compilation of geologic maps of Indonesia (Directorate of Mineral 

Resources and Inventory, 2004a), and scanned and rectified 1:250,000-scale quadrangle maps of Irian Jaya. Map symbols, lithology, 

and age ranges are based on 1:250,000-scale geologic maps. See table N3 for references] 

Map unit Map symbol Lithology Age range

Intrusive rocks 

Timepa Intrusion rocks Tmpt Quartz diorite, monzonite, andesite Miocene-Pliocene

Diorite Tpdi Diorite Pliocene

Intrusive rocks Tpd Diorite, granodiorite Pliocene

Volcanic rocks 

Andesite TpAn Andesite Pliocene

Volcanics Tpb Basalt Pliocene

Geologic Criteria

As depicted on the 1:250,000-scale geologic maps 

for the Rotanburg quadrangle (Harahap and Noya, 1995), 

the western parts of the tract area are mapped as Timepa 

intrusions, whereas the eastern parts are mapped as Pliocene 

diorite, andesite, and granodiorite on the Taritatua (Sidarto 

and Hartono, 1995) and Jiyawijaya (Koswara, 1995) maps. 

However, no igneous rocks of this age are mapped in the 

immediately adjacent areas in Papua New Guinea (Bain and 

others, 1972). No mines, known prospects, or known copper 

or gold occurrences are associated with this segment of the 

magmatic belt; there are two small alluvial gold workings near 

the tract in Papua New Guinea. This area has been referred 

to as a 300-km-wide “gap” where no Tertiary igneous rocks 

have been found by exploration geologists; the area also is 

lower in elevation (<2,000) than areas of Tertiary igneous 

rocks to the west (Cloos and others, 2005). The remoteness of 

the area, the lack of dated igneous rocks, lack of geophysical 

data available to the assessment team, and some dependence 
214 Porphyry Copper Assessment of Southeast Asia and Melanesia

by processing and were compared with source maps to ensure 

that original permissive boundaries and buffer distances were 

honored. The western part of the geology-based tract partly 

overlaps Eastern Minerals contract of work (COW) Block B 

(Freeport McMoRan Copper and Gold, Inc., 2006). The final 

tract boundary was edited by hand to include the COW area.

Known Deposits

None.

Prospects, Mineral Occurrences, and Related 

Deposit Types

No prospects or occurrences were reported within the 

tract area in the mineral occurrences databases examined for 

this study (table N3).

Exploration History

Other than anecdotal reports that exploration geologists found 

no evidence for porphyry copper-style mineralization, we are 

unaware of exploration results in the tract area. The western part 

of the tract overlaps parts of a COW (Block 3) that was held by 

Eastern Minerals Corporation (Freeport McMoRan Copper and 

Gold, Inc., 2006). The area is remote, and, in recent years, political 

and social unrest have been a detriment to exploration in the area. 

Given the proximity of the tract area to the Grasberg mine, it is 

likely that some proprietary data exist.

Sources of Information

Principal sources of information used by the assessment team 

for delineation of tract 142pCu7204 are listed in table N3. No mineral 

occurrence, geochemical, geophysical, isotopic-age data, or exploration results were available to the assessment team for this area.

Table N3. Principal sources of information used for tract 142pCu7204, Rotanburg-Taritatua Area—Indonesia. 

[CCOP, Coordinating Committee for Coastal and Offshore Geoscience Programmes in East and Southeast Asia; NA, not applicable]

Theme Map or title Scale Citation

Geology Digital geologic map of East and Southeast 

Asia

1:2,000,000 CCOP and Geological Survey of Japan (1997)

Digital geologic map of Indonesia 1;1,000,000 Directorate of Mineral Resources and Inventory (2004a)

Geologic quadrangle maps (Rotanburg, 

Taritatua, Jayawijaya )

1:250,000 Harahap and Noya (1995), Sidarto and Hartono (1995), Koswara 

(1995)

SE Asia Radiometric Ages: GIS Database NA Malaihollo and others (2002)

Geologic map of Irian Jaya, Indonesia 1:1,000,000 Dow and others (1986)

Mineral

occurrences

Porphyry copper deposits of the world: 

database, map, and grade and tonnage 

models

NA Singer and others (2008)

Mineral Resources Data System (MRDS) NA U.S. Geological Survey (2005)

World distribution of porphyry, porphyryrelated skarn, and bulk-mineable epithermal 

deposits

NA Dunne and Kirkham (2003)

Selected world mineral deposits database NA Kirkham and Rafer (2003)

Digital mineral occurrence database NA Directorate of Mineral Resources and Inventory (2004b)
Appendix N—Tract 142pCu7204 215

Qualitative Assessment

Notes on the 1:250,000-scale geologic maps that cover the 

tract area (table N3) infer that the igneous rocks may be related 

to those in the Grasberg-Ertsberg area. However, the age of 

the igneous rocks is unknown and no deposits or prospects are 

recorded in available databases. The mapped extent of intrusions is greater than that of coeval volcanic rocks, and compared to the small, circular intrusions that characterize the New 

Guinea magmatic belt, the intrusions are larger and more similar 

to the Miocene and older igneous rocks. The tract area may be 

too deeply eroded to preserve porphyry copper deposits.

On the basis of a lack of additional information and anecdotal reports of lack of mineralization reported by explorationists, the team included the area as permissive, but made no 

estimate of numbers of undiscovered deposits. Further work in 

the tract area may change the outlook for undiscovered deposits in the tract area.

References Cited

Bain, J.H.C., Davies, H.L., Hohnen, P.D., Ryburn, R.J., Smith, 

I.E., Grainger, R., Tingey, R.J. and Moffar, M.R., compilers, 

1972, Geology of Papua New Guinea, Canberra: Bureau of 

Mineral Resources, Geology and Geophysics, 1 map on

4 sheets, scale 1:1,000,000.

Berger, B.R., Ayuso, R.A., Wynn, J.C., and Seal, R.R., 

2008, Preliminary model of porphyry copper deposits: 

U.S. Geological Survey Open-File Report 2008–1321, 

55 p., accessed May 15, 2010, at http://pubs.usgs.gov/

of/2008/1321.

Coordinating Committee for Coastal and Offshore Geoscience 

Programmes in East and Southeast Asia (CCOP) and 

Geological Survey of Japan, 1997, Digital geologic map 

of East and Southeast Asia: Geological Survey of Japan, 

Digital Geoscience Map G-2 scale 1:2,000,000, CD-ROM.

Cloos, Mark, Sapiie, B., Quarles van Ufford, A., Weiland, 

R.J., Warren, P.Q., and McMahon, T.P., 2005, Collisional 

delamination in New Guinea—The geotectonics of 

subducting slab breakoff: Geological Society of America 

Special Paper 400, 51 p.

Directorate of Mineral Resources and Inventory, 2004a, 

Digital geologic map: Jakarta, Indonesia, Indonesian 

Ministry of Energy and Mineral Resources, 

scale 1:1,000,000. [Proprietary data.]

Directorate of Mineral Resources and Inventory, 2004b, 

Digital mineral occurrence database: Jakarta, Indonesia, 

Indonesian Ministry of Energy and Mineral Resources. 

[Proprietary data.]

Dow, D.B., Robinson, G.P., Hartono, U., and Ratman, N., 

1986, Geologic map of Irian Jaya, Indonesia: Bandung, 

Geological Research and Development Centre, 1 map, 

2 sheets, scale 1:1,000,000. [In English and Indonesian.]

Dunne, K.P.E, and Kirkham, R.V., compilers, 2003, World 

distribution of porphyry, porphyry-related skarn, and 

bulk-mineable epithermal deposits: Geological Survey of 

Canada, unpublished, accessed October 29, 2010, at 

http://gdr.nrcan.gc.ca/minres/index_e.php.

Freeport-McMoRan Copper and Gold, Inc., 2006, Annual 

report to the U.S. Securities and Exchange Commission 

Form 10-K for the fiscal year ending December 31, 2006: 

accessed March 10, 2011, at http://www.fcx.com/ir/

downloads/FCX200610K.pdf.

Garwin, S., Hall, R., and Watanabe, Y., 2005, Tectonic 

setting, geology, and gold and copper mineralization in 

Cenozoic magmatic arcs of southeast Asia and the west 

Pacific, in Hedenquist, T.W., Thompson, J.F.H., Goldfarb, 

R.J., and Richards, J.P., eds., One hundredth anniversary 

volume 1905–2005: Littleton, Colorado, Society of 

Economic Geologists, p. 891–930.

Harahap, B.H., and Noya, Y., 1995, Geological map of 

the Rotanburg (Idenburg Barat) Quadrangle, Irian 

Jaya: Bandung, Indonesia, Geological Research and 

Development Center, sheet 3312, scale 1:250,000. [In 

Indonesian and English.]

Hill, K.C., Kendrick, R.D., Crowhurst, P.V., and Gow, P.A., 

2002, Copper-gold mineralisation in New Guinea—

Tectonics, lineaments, thermochronology and structure, 

in Korsch, R.J., ed., Geodynamics of Australia and its 

mineral systems—Technologies, syntheses and regional 

studies: Melbourne, Australia, Blackwell Scientific 

Publications for the Geological Society of Australia, 

p. 737–752.

John, D.A., Ayuso, R.A., Barton, M.D., Blakely, R.J., 

Bodnar, R.J., Dilles, J.H., Gray, Floyd, Graybeal, F.T., 

Mars, J.C., McPhee, D.K., Seal, R.R., Taylor, R.D., and 

Vikre, P.G., 2010, Porphyry copper deposit model, chap. 

B of Mineral deposit models for resource assessment: 

U.S. Geological Survey Scientific Investigations Report 

2010–5070–B, 169 p., accessed September 8, 2010, at 

http://pubs.usgs.gov/sir/2010/5070/b/.

Kamitani, M., and Naito, K., eds., 1998, Mineral resource 

map of Asia: Metal Mining Agency of Japan, 1 sheet, scale, 

1:35,000,000, accessed February 10, 2010, at www.mmaj.

go.jp/mric_web/deposit/index.htm.

Kirkham, R.V., and Rafer, A.B., 2003, Selected world mineral 

deposits database: Geological Survey of Canada, Open File 

1801, 1 CD-ROM.
216 Porphyry Copper Assessment of Southeast Asia and Melanesia

Koswara, Achnan, 1995, Geological map of the Taritatu 

(Kerom) quadrangle, Irian Jaya: Bandung, Indonesia, 

Geological Research and Development Centre, sheet 

no. 3412, scale 1:250,000.

Malaihollo, J.F.A., Hall, R., and Macpherson, C.G., 2002, SE 

Asia radiometric ages—GIS database: accessed January 15, 

2010, at http://searg.rhul.ac.uk/current_research/isotopic_

ages/SEAsia_GIS.pdf.

McDowell, F.W., McMahon, T.P., Warren, P.Q., and Cloos, 

M., 1996, Pliocene Cu-Au bearing igneous intrusions 

of the Gunung Bijih (Ertsberg) district, Irian Jaya, 

Indonesia—K-Ar geochronology: Journal of Geology, 

v. 104, p. 327–340.

Quarles van Ufford, Andrew, and Cloos, Mark, 2005, 

Cenozoic tectonics of New Guinea: Bulletin of the 

American Association of Petroleum Geologists, v. 89, no. 

1, p. 119–140.

Sidarto, and Hartono, U., 1995, Geological map of the 

Jayawijaya quadrangle, Irian Jaya: Bandung, Indonesia, 

Geological Research and Development Centre, Bandung, 

sheet no. 3411, scale 1:250,000.

Singer, D.A., Berger, V.I., and Moring, B.C., 2008, Porphyry 

copper deposits of the world—Database and grade and 

tonnage models, 2008: U.S. Geological Survey Open-File 

Report 2008–1155, accessed June 1, 2011, at http://pubs.

usgs.gov/of/2008/1155/.

U.S. Geological Survey, 2005, Mineral resources data 

system: Reston, Virginia, U.S. Geological Survey, accessed 

December 30, 2010, at http://tin.er.usgs.gov/mrds/.

van Leeuwen, T.M., 1994, 25 years of mineral exploration 

and discovery in Indonesia: Journal of Geochemical 

Exploration, v. 50, p. 13–90.
138° E 140° E 

4° S

!

INDONESIA PAPUA N

Jayapura

B

120°E 140°

10°N

0°

10°S

PACIFI

INDIAN OCEAN 

AU

ID

ID

PH

Political boundary source: U.S. Department of State (2009)Projection: Asia South Albers Equal Area Conic;Central meridian 140° E; latitude of origin 15° S

0 25 50 75 100 KILOMETERS0 25 50 MILES

EXPLANATION

Other porphyry copper tractsAssessed porphyry copper tract 142pCu7204Porphyry copper deposits associated with other tractsPorphyry copper prospects associated with other tracts

Figure N1. Map showing tract location for tract 142pCu7204, Rotanburg-Taritatua Area—Indonesia. AU, Australia; ID, Indonesia; PH, Philippines

Guinea; SB, Solomon Islands.
( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( 

( ( ( ( ( ( ( ( ( ( ( ( ( ( ( (

(

( ( ( ( (

(

( ( ( ( ( ( ( ( ( 

( ( ( ( ( ( ( ( ( ( (

(

( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( 

( ( ( ( ( ( (

(

( ( ( ( (

(

Bismark Sea

Arafura Sea

INDONESIA PAPUA NEW GUINEA

138° E 140° E 142° E

2° S4° S6° S

Base from ESRI ArcGIS Online (2009)World Shaded ReliefPolitical boundary source: U.S. Department of State (2009)Projection: Asia South Albers Equal Area Conic;Central meridian 134° E; latitude of origin 15° S

0 50 100 150 200 KILOMETERS

0 50 100 MILES

E

Ass 1PerPer

( ( Sub

Figure N2. Map showing the distribution of permissive igneous rocks for tract 142pCu7204, Rotanburg-Taritatua Area—Indonesia.
Appendix O—Tract 009pCu7203 219

Appendix O. Porphyry Copper Assessment for Tract 009pCu7203, 

Eastern Medial New Guinea Magmatic Belt—Papua New 

Guinea and Indonesia

By Jane M. Hammarstrom1, Dulcie Saroa2, Bambang Tjahjono Setiabudi3, Dwi Nugrono Sunuhadi3, 

Gilpin R. Robinson, Jr.1

, Connie L. Dicken1, Benjamin J. Drenth4, Steve Ludington5, Arthur A. Bookstrom6, 

and Michael L. Zientek6

, with contributions from Gwaibo Kopi2 and Dennis P. Cox5

Deposit Type Assessed: Porphyry copper, copper-gold subtype

Descriptive model: Porphyry copper (Berger and others, 2008; John and others, 2010); Porphyry copper-gold 

(Cox, 1986; Cooke and others, 1998)

Grade and tonnage model: Porphyry copper, copper-gold subtype (Singer and others, 2008)

Table O1 summarizes selected assessment results.

Table O1. Summary of selected resource assessment results for tract 009pCu7203, Eastern Medial New Guinea Magmatic Belt—

Papua New Guinea and Indonesia.

[km, kilometers; km2, square kilometers; t, metric tons; preliminary assessment in 2005, revised in 2010] 

Date of 

assessment

Assessment 

depth (km) Sub-tract Tract area (km2)

Known copper 

resources (t)

Mean estimate of 

undiscovered copper 

resources (t)

Median estimate of

undiscovered copper 

resources (t)

February 2010 1 009pCu7203a 14,230 6,116,600 5,100,000 1,200,000

009pCu7203b 53,220 11,368,926 20,000,000 10,000,000

1

U.S. Geological Survey, Reston, Virginia, United States.

2

Mineral Resources Authority, Papua New Guinea.

3

Center for Geological Resources, Geological Agency of Indonesia, West Java, Indonesia.

4

U.S. Geological Survey, Denver, Colorado, United States.

5

U.S. Geological Survey, Menlo Park, California, United States.

6

U.S. Geological Survey, Spokane, Washington, United States.

Location

The tract includes the Central Highlands of Papua New Guinea and easternmost Papua province, Indonesia (fig. O1).

Geologic Feature Assessed

Eastern part of the late Miocene to Pliocene-Pleistocene Medial New Guinea magmatic belt.
220 Porphyry Copper Assessment of Southeast Asia and Melanesia

Delineation of the Permissive Tract

Tectonic Setting

Tract 009pCu7203 outlines exposed segments of the late 

Miocene and Pliocene to Pleistocene Medial New Guinea 

magmatic belt (fig. 3, no. 13). The tract represents the eastern 

part of the 1,800-km-long Medial New Guinea magmatic belt 

that formed from convergence of the Indo-Australian and 

Pacific Plates during the Cenozoic. The western part of the 

Belt is delineated as tract 142pCu7203 in Indonesia. These 

two coeval tracts span two United Nations (UN) regions 

and are separated by a gap in mapped igneous rocks of late 

Miocene to Pliocene age. Region codes are used to designate 

tracts in the global assessment. UN region 142 represents Asia, 

including Indonesia; region 009 represents Oceania, including Papua New Guinea. In order to preserve this distinction, 

we used tract identifier 7203 for both regions, preceded by the 

appropriate UN region code.

Most of the tract is within the Fly-Highlands province 

along the eastern part of the Central Range (FHP on fig. 7). 

The western part of the magmatic belt (tract 142pCu7203) is 

late Miocene to Pliocene, whereas the eastern part of the belt 

(tract 009pCu7203) predominantly is Pliocene to Pleistocene 

in age (Cloos and others, 2005). A well-defined subduction 

zone is not associated with the belt, although seismic tomography suggests the existence of old subduction slabs within 

the mantle under New Guinea (Hall and Sparkman, 2002; 

Garwin and others, 2005). A number of explanations for the 

lower volume, more alkaline, post-Maramuni Arc (Miocene) 

magmatic activity have been suggested, including south-dipping subduction following a reversal in subduction polarity, 

post-collision uplift, and transitions to extensional tectonism 

(Housh and McMahon, 2000). As noted by Garwin and others 

(2005), the tectonic trigger for the high-K, calc-alkaline to 

alkaline magmatic event is not well understood, but it is likely 

related to the southward progressing compressional deformation that formed and uplifted the fold belt as a result of convergence of New Guinea and the Pacific-Caroline Plate to the 

north (fig. 6). Local dilational zones formed at intersections 

of strike-parallel (generally east-west) frontal thrust faults 

and strike-perpendicular long-lived crustal transfer structures, 

which are expressed as lineaments. These dilational zones 

facilitated emplacement of magmas and porphyry copper-gold 

mineralization in central New Guinea (Hill and others, 2002). 

Cloos and others (2005) suggested that the late Neogene 

volcanism in the eastern parts of the Medial New Guinea 

Belt appears more widespread than in the western parts of 

the Central Range and represents a younger, less eroded part 

of the belt; at 3 Ma, the western part of the belt may have 

looked like the present-day eastern part of the belt. Based on 

differences in the relative amounts of intrusive and volcanic 

rocks and, therefore, differences in the depth of exposure and 

likelihood of undiscovered porphyry copper deposits within 

the eastern part of the belt, the tract was subdivided into two 

sub-tracts (009pCu7203a and 009pCu7203b) for assessment.

The nature of the basement of the Medial New Guinea 

magmatic belt differs from west (tract 142pCu7203) to 

east (tract 009pCu7203). The Tasman Line is interpreted as 

extending roughly north-south to northwest through an area 

approximately 100 km west of the modern Indonesian (Irian 

Jaya)-Papua New Guinea border (fig. 6). The Tasman Line 

defines two crustal provinces in northern Australia: Paleozoic 

basement of the accreted terranes of the Tasman orogen lie to 

the east of the line; the stable craton with Precambrian basement lies to the west (Hill and Hall, 2003). These differences 

in basement affect the crustal response to deformation, and 

may influence the character of porphyry-related magmas.

Geologic Criteria

The tract was constructed in a GIS using a digital compilation of 1:250,000-scale geologic maps of Papua New Guinea 

and a 1:1,000,000-scale geologic map of Papua New Guinea 

(Bain and others, 1972). In addition, maps and figures showing the major faults, lineaments, and tectonic divisions of New 

Guinea by Garwin and others (2005), Hill and others (2002), 

Cloos and others (2005), and Quarles van Ufford and Cloos 

(2005) were used.

Map units were classified into generalized units by age 

and lithologic class (igneous volcanic, igneous plutonic) based 

on map-legend attributes. From this digital database of map 

units grouped by age and lithology, all igneous rocks of late 

Miocene to Pliocene-Pleistocene age were selected. Examination of cross sections on 1:250,000-scale geologic maps 

showed that most intrusive rocks of this age range are shown 

as steep-sided, cylindrical or finger-like intrusive bodies with 

a subsurface horizontal extent of less than 2–5 km; vertical 

extents can exceed 1 km.

Using GIS tools, a 5-km buffer was applied around 

mapped igneous contacts of permissive lithologies to account 

for spatial uncertainty in digitized geology and for the possibility of greater extent of permissive rocks within a kilometer 

of the surface. Ophiolites and ultramafic rocks, basaltic units, 

and units that are predominantly ash flows, tuffs, and agglomerates were deemed nonpermissive and are omitted from the 

tract. Pliocene to Pleistocene andesitic volcanic centers (for 

example, Kerewa Volcanics, Crater Mountain Volcanics) are 

included; these may cover buried intrusions that host porphyry copper deposits, although the volcanic cover may be 

>1 km thick in some places. Diatremes around the periphery 

of these centers are current exploration targets. The occurrence of the diatreme at Grasberg in the western part of the 

magmatic belt, small cylindrical steep-sided stocks associated 

with known porphyry copper deposits, and the recognition 

of telescoped epithermal systems overlying young porphyry 

systems in this tectonically active region (such as at Lihir 

Island) suggest that the volcanic centers should be included 

within the tract.

The buffered map units were aggregated using GIS 

processing tools with a 15 km distance to group closely spaced 

permissive areas, which were then edited to honor fault bound-
Appendix O—Tract 009pCu7203 221

aries and include other areas of known igneous rocks of appropriate age and lithology. Databases of isotopic ages of igneous 

rocks for Papua New Guinea compiled by the Southeast Asia 

Research Group provided additional controls on distributions 

of permissive rocks (Malaihollo and others, 2002) by providing locations and lithologic descriptions of dated samples.

Late Miocene to Pliocene intrusions associated with porphyry copper mineralization crop out as hypabyssal intrusive 

bodies and small dikes and plugs; many are too small to show 

on 1:250,000-scale maps. Aeromagnetic data for the Central 

Highlands area of Papua New Guinea (109.5 to 145.5oW) 

from the Mineral Resources Authority of Papua New Guinea 

were processed by Benjamin J. Drenth (USGS, Denver, Colorado). The data were transformed by a reduction to pole and 

compared with mapped geology to identify areas of possible 

shallow buried intrusions for inclusion in tracts, and areas of 

magnetic quiescence that correlate with thick sedimentary 

basins for exclusion from tracts.

The initial tract boundaries were established by GIS 

processing. Final editing was accomplished by hand. The 

processing steps included (1) unioning buffered permissive 

map units and other polygon features that comprise the framework of the tract; (2) aggregating unioned polygons using an 

aggregation distance of 15 km and a minimum hole size of 

1,000 km2

; (3) manually aggregating and adjusting tract areas; 

and (4) smoothing polygons. Preliminary tracts were cleaned 

to remove necking and thinning introduced by processing 

and were compared with source maps to ensure that original 

permissive boundaries and buffer distances were honored. 

Regional and local mineral occurrence, geochemical, and 

isotopic-age data were plotted and used to constrain or expand 

tract boundaries; magnetic data also were used where available 

(Central Highlands of Papua New Guinea). Tract boundaries 

were clipped at shorelines using a Global GIS dataset (U.S. 

Department of State, 2009).

The southern boundary of the tract area follows the 

approximate trace of a thrust fault between the southern 

margin of the Papuan Fold Belt and the northern edge of the 

stable platform of southern New Guinea Island (fig. 6). The 

team delineated the tract as a series of geologic map-based, 

GIS-derived polygons, as described above. However, areas 

between the map-based parts of the tract, as indicated by the 

highlands areas shown in shaded relief on figure O2, may conceal unmapped permissive rocks. Access to aeromagnetic data 

for the entire study area would help identify potential shallow 

intrusions that could host porphyry copper deposits. In areas 

where such data are available, the magnetic data suggest that 

the intrusions tend to be small and isolated, and therefore, the 

team chose to portray the tract in map-based segments. Subtract a represents the border area; sub-tract b represents all 

areas east of the diagonal line shown in figure O1. The dividing line approximately corresponds to the Porgera lineament 

(Garwin and others, 2005) and separates an area of dominantly 

intrusive rocks (A) from an area of mainly volcanic rocks (B). 

The dividing line also correlates with a change in texture of 

aeromagnetic data.

Sub-tract 009pCu7203a

Sub-tract a includes a small area in Indonesia just west of 

the Papua New Guinea border (fig. O1).

Border area (Fold Belt area, South of the Direwo Fault, 

at the Indonesia-Papua New Guinea border).—Diorite and 

granodiorite intrusions mapped in Indonesia are contiguous with 

rocks mapped as late Miocene to Pliocene Antares Complex in 

Papua New Guinea (quartz monzodiorite, quartz monzonite, 

diorite and microdiorite, granodiorite, granite, some porphyry, 

some volcanic rocks) and porphyritic rocks of the Star Mountain Intrusives associated with the Ok Tedi, Star Mount Futik, 

and Star Mount Nong River porphyry copper-gold deposits. 

Page (1975) reported biotite, hornblende, plagioclase, and 

whole-rock K-Ar ages on mineralized porphyries in the Star 

Mountains Intrusives (3.4–4.6 Ma and Antares Monzonite 

(2.4–3.1 Ma). The eastern boundary of sub-tract 009pCu7203a 

marks a transition from areas where intrusive rocks are more 

abundant than volcanic rocks to areas to the east where volcanic 

rocks are more abundant than intrusive rocks (fig. O2).

Sub-tract 009pCu7203b

Sub-tract b, entirely within the country of Papua New Guinea 

(fig. O1), includes several areas of late Miocene and younger 

permissive igneous rocks. In sub-tract b, permissive rocks tend 

to be younger than in sub-tract a, the extent of mapped volcanic rocks tends to be much greater than the extent of mapped 

intrusive rocks, and the large amount of volcanic cover may 

conceal buried deposits. The tract is based on the intrusive 

and volcanic rocks shown in figure O2 and listed in table O2. 

Extensive Quaternary volcanic cover is present in the western 

parts of sub-tract 009pCu7203b.

Central Highlands of Papua New Guinea.—This area 

outlines small micromonzonite and microdiorite intrusions 

in the Fold Belt of western Papua New Guinea. The tract 

includes late Miocene intrusions associated with the Porgera 

mine, late Miocene intrusive rocks at the Yandera porphyry 

copper deposit, the late Miocene Michael Diorite, and areas 

that may represent shallowly buried intrusions and volcanic 

centers based on aeromagnetic data. Exposed volcanic centers 

(Sisa Volcanics, Kerewa Volcanics, and Crater Mountain 

Volcanics) lie along northeast-trending orogen-transverse 

structural corridors. Magnetic data suggest that an unexposed 

intrusion is located along a northeast-trending corridor and 

about 80 km from exposed volcanic centers that lie to the 

west and east. The magnetic data also were used to delineate 

permissive areas around isolated, shallow magnetic anomalies 

that may represent shallow buried intrusions or diatremes. The 

Nevera Intrusive Complex, the locus of the Crater Mountain 

Project (New Guinea Gold Corp., 2009; Gold Anomaly, Ltd., 

2011) is in a diatreme along the northern edge of the Crater 

Mountain Volcanic field (fig. O3). Volcanic cover may be more 

than 1 km thick in some areas; however, the Crater Mountain 

volcano is deeply eroded (Global Volcanism Program, 2010). 
222 Porphyry Copper Assessment of Southeast Asia and Melanesia

Table O2. Map units that define tract 009pCu7203, Eastern Medial New Guinea Magmatic Belt—Papua New Guinea and Indonesia.

[Map unit, age range, and principal lithologies are based on a digital compilation of 1:250,000 scale geologic maps of Papua New Guinea (Papua New Guinea 

Geological Survey, 2002), a digital compilation of igeous rocks of Southeast Asia (Directorate of Mineral Resources and Inventory, 2004a), and scanned and rectified 1:250,000-scale quadrangle maps of Irian Jaya. Map symbols, lithology, and age ranges for Indonesia are based on 1:250,000-scale geologic maps; Papua New 

Guinea 1:250,000 map numbers and publication dates are listed. *, Indonesia. Major volcanic units and representative map sources are listed; variants of these 

units occur within the tract area on other maps. - -, no map unit] 

Map unit Map 

symbol Lithology Age range Map number

Map 

year

009pCu7203a, Intrusive rocks

Antares Monzonite Tpa Monzonite, granodiorite, adamellite, fine-grained 

equivalents; minor tuff, agglomerate, lava, skarn

Late Miocene to Pleistocene B5407 1972

Antares Complex (Ban 

Quartz Monzodiorite)

Tpb Quartz monzodiorite, granodiorite, quartz monzonite Late Miocene to Pliocene B5403 1979

Fubilan Stock Tpf Quartz monzonite porphyry, quartz monzonite: 

mineralized

Late Miocene to Pleistocene B5407 1972

Mount Ian gabbro Tpg Gabbro Late Miocene to Pleistocene B5407 1972

- - Tpi Diorite and microdiorite porphyry, some biotite, much 

altered (Porgera); altered microdiorite porphyry (Baia); 

coarse hornblende granite and diorite (Lai-Tsak)

Pliocene? B5408 1980

Nong River Diorite Tpn Diorite, quartz diorite, monzodiorite, quartz monzodiorite Late Miocene to Pliocene B5403 1979

Stolka Quartz Diorite Tpo Quartz diorite, quartz monzodiorite, minor porphyry Late Miocene to Pliocene B5403 1979

Star Mountains 

Intrusives

Tps Porphyritic micromonzonite, microdiorite, 

microgranodiorite; minor medium-grained equivalents; 

Sulphide, magnetite and epidote-garnet skarn

Late Miocene to Pleistocene B5407 1972

Tumfakama Microdiorite Tpt Microdiorite, diorite, microgranodiorite Late Miocene to Pliocene B5403 1979

Antares Complex Tpv Andesitic and dacitic volcanic agglomerate, volcaniclastic 

sandstone and mudstone, crystal tuff

Late Miocene to Pliocene B5403 1979

Intrusive rocks* Tpt Diorite, granodiorite; intrudes Miocene rocks; may be 

skarns where intrude carbonates

Pliocene Jiyawijaya

250K

009pCu7203a, Volcanic rocks

Kendupwa Volcanics Tpk Andesitic agglomerate, tuff, and volcanic sandstone, 

minor marl

Pliocene B5408 1980

Antares Complex Tpp Andesitic and dacitic porphyry; phenocrysts are 

hornblende, plagioclase, minor pyroxene, rare biotite

Late Miocene to Pliocene B5403 1979

009pCu7203b, Intrusive rocks

Elandora Porphyry Tme Hornblende andesite porphyry, microdiorite Late Miocene B5510 1972

- - Tmi Diorite, monzonite, minor granodiorite, gabbro; dykes, 

small plutons and stocks

Miocene to Pliocene C5502 1973
Appendix O—Tract 009pCu7203 223

Table O2. Map units that define tract 009pCu7203, Eastern Medial New Guinea Magmatic Belt—Papua New Guinea and Indonesia.—

Continued

Map unit Map 

symbol Lithology Age range Map number

Map 

year

 009pCu7203b, Intrusive rocks

Suckling Granite Tmk Medium and coarse granite Late Miocene C5508 1972

Oveia Diorite Tmo Diorite, monzonite Early Miocene? C5507 1978

Benembi Diorite Tmub Porphyritic microdiorite Late Miocene? B5505 1971

Michael Diorite Tmum Porphyritic hornblende microdiorite Late Miocene B5509 1971

 - - Tmuy Monzonite, porphyritic microdiorite, porphyry Late Miocene B5505 1971

Mai’iu Monzonite Tpx Xenolithic granodiorite, biotite monzonite, biotite hornblendite Late Miocene to 

early Pliocene

C5508 1972

Bonua Porphyry Tpb Microdiorite and micromonzonite porphyry stocks, lamprophyric dykes Pliocene C5508 1972

Edie Porphyry Tpe, Tpp Biotite and hornblende dacite and andesite porphyry stocks and dykes Pliocene B5510, 

B5514

1972

 - - Tpg Granodiorite, minor tonalite, adamellite, and granite Pliocene C5605 1969

Gidogidora 

Granodiorite

Tpgg Granodiorite Pliocene C5605 1969

Observation Island 

Granodiorite

Tpgb Granodiorite Pliocene C5605 1969

Luboda Granodiorite Tpgl Granodiorite stock with marginal xenoliths of altered gabbro Pliocene C5605 1969

Omara Granodiorite Tpgo Granodiorite, some granite, some amphibolite xenoliths Pliocene C5605 1969

 - - Tpi Dolerite, microdiorite, microtonalite, diorite, granodiorite, tonalite Late Pliocene B5501 1974

009pCu7203b, Volcanic rocks

Aifunka Volcanics Tmf Andesitic lava, tuff, agglomerate Middle Miocene B5510 1972

Astrolabe 

Agglomerate

Tpa Basalt and minor andesite agglomerate and tuff, partly reworked Pliocene C5507 1978

Amphlett Volcanics Tpm Trachyte, andesite and basaltic andesite lava and agglomerate Pliocene C5605 1969

Cloudy Bay 

Volcanics

Tpc, 

Tpt

Basaltic and andesitic agglomerate and lava: shoshonitic affinities; 

volcanic plugs; tuff

Pliocene C5512, 

C5507

1970, 

1978
224 Porphyry Copper Assessment of Southeast Asia and Melanesia

Table O2. Map units that define tract 009pCu7203, Eastern Medial New Guinea Magmatic Belt—Papua New Guinea and Indonesia.—

Continued

Map unit Map 

symbol Lithology Age range Map

number

Map

year

 009pCu7203b, Volcanic rocks

Crater Mountain 

Volcanics

TQvc Andesitic and basaltic lava; minor tuff, agglomerate, derived sediments Pliocene to 

Holocene

B5509 1971

Kerewa Volcanics TQk Fine grained trachyandesite lava and lava breccia, some andesitic 

agglomerate and tuff

Pliocene to early 

Pleistocene

B5408 1980

Kukuia Volcanics TpQk Rhyolite, rhyolitic obsidian, andesite ashflow tuff, and some basalt Pliocene to 

Pleistocene

C5605 1969

Mount Cameron 

Volcanic Complex

Tpia Basalt and andesitic agglomerate, minor tuff; tuffaceous sandstone and 

volcanic conglomerate at base (Kwikila Agglomerate)

Pliocene C5507 1978

Mount Davidson 

Volcanics

Tpd Basaltic and minor andesitic agglomerate, tuff, lava, lava breccia; 

massive to vesicular olivine and augite-phyric basalt

Latest Miocene 

to early Pliocene

C5503 1998

Bulolo Agglomerate Tpg Dacite and andesite agglomerate; minor crystal tuff Pliocene B5514 1972

Musa Volcanic 

Member

Tpz Basaltic agglomerate: shoshonitic affinities Pliocene C5508 1972

Namie Breccia Tpv Volcanic breccia Pliocene B5514 1972

Ne Volcanics TQn Andesite lava Pliocene to early 

Pleistocene

B5408 1980

Normanby Volcanics Tpn Andesite lava with some rhyolite, dacite, trachyte, trachyandesite and olivine 

basalt; basaltic agglomerate

Pliocene C5609 1972

Sesara Volcanics Tps Basalt agglomerate, lava, tuff, minor volcanic sandstone; shoshonitic 

affinities; minor sediments; volcanic plugs

Late Miocene to 

early Pliocene

C5508 1972

Sisa Volcanics TQs Andesitic and basaltic agglomerate, tuff, lava: old cone Pliocene to early 

Pleistocene

B5408 1980

Talama Volcanics Tmt Andesitic to basaltic agglomerate, tuff, lava breccia, lava; intercalated 

volcanically derived conglomerate, sandstone, minor mudstone

Middle to late 

Miocene

C5502 1973

Uvo Volcanics Tpu Andesite agglomerate, lapilli tuff, tuff including ash-flow tuff Late Pliocene B5501 1974

- - TQp Probably pyroclastics, jointed and faulted (airphoto interpretation) Pliocene to early 

Pleistocene

B5408 1980

- - Tp Basic volcanics; mainly horizontal basalt flows Pliocene B5511 1972
Appendix O—Tract 009pCu7203 225

Parts of the tract overlap with the older Maramuni Arc; margins 

of older rocks localize some younger intrusions.

Peninsular Papua New Guinea.—Small stocks of 

diorite, porphyritic microdiorite, monzonite, and granodiorite 

associated with coeval volcanic rocks (Mount Davidson 

Volcanics, Cloudy Bay Volcanics) delineate the tract on the 

main island of New Guinea. On offshore islands, the tract is 

delineated based on outcrops of Pliocene andesitic Normanby 

Volcanics, Gigogidorra Granodiorite, Omara Granodiorite, 

and other late Miocene-Pliocene rocks. The Kodu (Mount 

Bini) porphyry copper deposit and a number of prospects 

occur within this segment of the tract. The tract also includes 

Pliocene granodiorites and andesites in the D’Entrecasteaux 

Islands of Milne Bay Province.

Finisterre Range-northeastern Papua New Guinea 

coastal area.—Small stocks of Pliocene gabbro, diorite, 

clinopyroxene diorite, hypersthene gabbro, dolerite, 

microdiorite, quartz gabbro, tonalite, microtonalite, 

granophyric differentiates, diorite, and late Pliocene volcanic 

rocks (partly andesitic), crop out within 20–50 km of the coast 

in northeastern Papua New Guinea. This area is considered 

to be underexplored and currently is under exploration for 

porphyry copper-gold and skarn targets (Chrome Corp., 2009; 

Pacific Niugini, 2010).

Known Deposits

Porphyry copper deposits within the tract are listed in 

table O3 and plotted on figure O1. Only deposits with reliable identified resources and reserves are included. Partially 

explored deposits that lack reliable resource estimates are 

discussed below as prospects and are included in table O4.

Sub-tract 009pCu7203a

Ok Tedi (also known as Mount Fuliban), with 5.5 Mt 

contained copper, is the largest of three porphyry copper 

deposits in the Star Mountains of Papua New Guinea and the 

only copper-producing mine in the country in 2007 (Wacaster, 

2010). Ok Tedi is an open-pit mine (~22,000-hectare 

lease area) that was discovered in 1968 by reconnaissance 

exploration by Kennecott; production started in 1985 

with mining of the gold-rich supergene oxide cap. Copper 

production started in 1987 (Hendry and others, 2005). Ok 

Tedi produced 159,650 t of copper and 16,032 kg of gold in 

2008 (Wacaster, 2010). As of December 31, 2009, proven and 

probable reserves were reported as 113 Mt of 0.80 percent 

copper and 1.10 g/t gold (Inmet Mining Corp., 2009). Expected 

mine life is projected to 2013, although the managers are 

exploring options for extending mine life to 2022.

At Ok Tedi, chalcopyrite, chalcocite, and minor bornite 

are present in quartz veins and stockworks in a porphyritic 

monzonite intrusion; copper and gold occur in magnetite and 

sulfide skarns in country rocks (van Dongen and others, 2007). 

Intrusive rocks are alkaline in character. Sulfur isotopic values 

(δ34S= −0.8 to 5.1) are slightly elevated relative to typical 

porphyry copper sulfide isotopic signatures (δ34S= -5 to 1). 

Low rare-earth element concentrations may reflect destruction 

of monazite, xenotime, and apatite during hydrothermal 

alteration (van Dongen and others, 2007).

Two smaller porphyry copper deposits, Star Mount 

Nong River and Star Mount Futik (300,000 and 350,000 Mt 

contained copper, respectively), lie about 25 km to the north of 

Ok Tedi along a northeast-trending structural corridor.

Sub-tract 009pCu7203b

Central Highlands of Papua New Guinea.—Geochemical 

exploration in the 1970s led to identification of the Yandera 

porphyry copper deposit. Anomalous copper concentrations 

in stream sediments sampled at a density of one sample per 1 

to 2 km2 delineated the porphyry copper system (Fleming and 

Neale, 1979). In 2009, Marengo Mining, Ltd., was developing 

an open-pit mine at the Yandera porphyry copper deposit to 

produce copper and molybdenum, with byproduct gold, iron 

ore, silver, and rhenium starting in 2010 (Wacaster, 2010). 

Indicated and inferred resources announced in 2011 (Marengo 

Mining, Ltd., 2011b), listed in table O2, include estimates of 

byproduct rhenium that could be recovered from molybdenum. 

Note that the JORC-compliant data (Marengo Mining, Ltd., 

2011a,b) reported in table O2 are for the lowest reported cut-off 

graded (0.2 percent CuEq, where CuEq is calculated as Cu+(10 

× Mo). At this cut-off grade, the Yandera deposit contains 5.7 

million metric tons of copper. At the more commonly cited 

higher cut-off grade of 0.3 percent CuEq, the deposit contains 

2.9 million metric tons of copper. The 7 by 2 km mineralized 

system extends beyond the area included in resource estimates.

Peninsular Papua New Guinea.—The Golpu porphyry 

copper-gold deposit is part of the Wafi-Golpu mineralized 

intrusive system, which includes a high-grade core of stockwork 

veining in altered diorite porphyry (174 Mt at 1.57 percent copper 

and 0.88 g/t gold), a halo of stockwork in metasedimentary 

host rocks (314 Mt at 0.59 percent copper and 0.6 g/t gold), and 

the Wafi high-sulfidation epithermal gold deposit (Harmony 

Gold Mining Co., 2011). The porphyry deposit is centered on 

a diatreme associated with the Miocene Golpu diorite to dacite 

porphyry plug and late-stage breccias (Porter Geoconsultancy, 

2004). Harmony expanded the footprint of their Wafi-Golpu 

project area to include the Nambonga porphyry copper-gold 

prospect, located 2 km northwest of Golpu (Harmony Gold 

Mining Co., 2009). The project is part of the 50:50 Morobe 

Mining Joint Venture between Harmony Gold Mining Company 

and Newcrest Mining Limited. Total resources for the Golpu and 

Nambonga porphyry deposits are listed in table O3 (Harmony 

Gold Mining Co., 2010; Newcrest Mining Limited, 2010). Both 

deposits are open and continue to be explored; prefeasibility 

studies were underway in 2011 to confirm resource classifications 

and acquire geotechnical and metallurgical data (Hannah, 2011).

The Kodu deposit (formerly called Mount Bini) was located 

by stream-sediment and rock-float sampling (Dugmore and others, 

1996, 1998). The deposit, situated along a NNE-trending lineament defining a 15–20 km wide structural zone, is hosted in the 
226 Porphyry Copper Assessment of Southeast Asia and Melanesia

Table O3. Porphyry copper deposits in tract 009pCu7203, Eastern Medial New Guinea Magmatic Belt—Papua New Guinea and 

Indonesia.

[Ma, million years; Mt, million metric tons; t, metric ton; %, percent; g/t, gram per metric ton; Cu-Au subtype, deposits that have Au/Mo ratios >30 or average 

Au grades >0.2 g/t. Contained Cu in metric tons is computed as tonnage (Mt × 1,000,000) × Cu grade (%); NA, not applicable; n.d., no data; *, data for Yandera 

reported at cutoff grade of 0.2% CuEq, average rhenium grade 0.05 ppm; **, data for Wafi-Golpu based on 2010 data for Golpu and Nambonga porphyry deposits, excludes the Wafi epithermal gold deposit]

Name Latitude Longitude Subtype Age 

(Ma)

Tonnage 

(Mt) Cu (%) Mo (%) Au (g/t)

Ag 

(g/t)

Contained 

Cu (t) Reference

Sub-tract 009pCu7203a

Ok Tedi -5.200 141.133 Cu-Au 1 854 0.64 0.011 0.78 n.d. 5,465,600 Andrew (1995), Bamford (1972), Davies 

and others (1978), Page (1975), Rush 

and Seegers (1990), Sillitoe (1995), 

Stapleton (1993), Tarkian and Stribrny 

(1999), van Dongen and others (2007) 

Star Mount 

Nong River

-5.017 141.217 NA 4 60 0.50 n.d. n.d. n.d. 300,000 Arnold and Griffin (1978), Page (1975)

Star Mount 

Futik

-5.067 141.333 NA 4 65 0.54 n.d. 0.10 n.d. 351,000 Arnold and Griffin (1978), Page (1975)

Sub-tract 009pCu7203b

Yandera* -5.750 145.167 NA 7 1,639 0.35 0.010 0.07 1.5 5,749,926 Lole (2005), Marengo Mining Limited 

(2009, 2011a,b), Titley and others 

(1978), Watmuff (1978) 

WafiGolpu**

-6.883 146.450 Cu-Au 9 540 0.90 0.01 0.56 n.d. 4,860,000 Andrew (1995), Corbett and Leach 

(1998), Freebrey (1998), Funnel (1990), 

Gillman (2004), Harmony Gold Mining 

Co. ( 2010), Newcrest Mining Limited 

(2010), Leach (1999), Lole (2005), Ryan 

and Vigar (1999), Tau-Loi and Andrew 

(1998)

Kodu (Ofi 

Creek, 

Mount 

Bini)

-9.300 147.583 Cu-Au 4 276 0.28 0.008 0.30 1.75 759,000 Anonymous (1996), Dugmore and 

others (1998), Dugmore and others 

(1996), Leaman (1996) , Frontier 

Resources, Ltd. (2007a), Keele and 

Lindley (2004)
Appendix O—Tract 009pCu7203 227

Table O4. Significant prospects and occurrences in tract 009pCu7203, Eastern Medial New Guinea Magmatic Belt—Papua New 

Guinea and Indonesia.

[Ages all assumed to be Late Miocene to Pliocene based on associated map units. Rank 4=Prospect listed in global database of Singer and others (2008) or 

<16,000 t of ore established by drilling. Rank 3=drilled, with >20 m of 0.2% or more Cu. Rank 2=drilled or trenched with <20 m of 0.2% Cu or <0.2% Cu, or 

past or ongoing exploration. Rank 1= copper occurrence that may be related to porphyry-type mineralization based on stream sediment or magnetic anomaly or 

location along structural trend. %, percent; g/t, grams per metric ton; km, kilometers; m, meters; ppm, parts per million; Mt, million metric tons]

Name Latitude Longitude Comments Reference Rank

Sub-tract 009pCu7203a

Porgera -5.468 143.086 Epithermal gold deposit with some porphyry characteristics; 

potential for deep porphyry? Deep exploration (1,000 

m below epithermal gold deposit workings identified 

hydrothermal magnetite, secondary biotite, chalcopyrite, and 

pyrrhotite. No economic copper mineralization. 

Richards and Kerrich (1993), 

Richards (1997)

2

Sub-tract 009pCu7203b

Wamum

(Wau-Morobe)

-6.750 146.283 Average for 5 drill holes: 0.37% Cu, 0.24 g/t Au and 1.1 g/t 

Ag. Drill-defined resource for Mount Wamum of 45 Mt at 

0.30 % Cu and 0.12 g/t Au. 

Shedden (1990); Singer and 

others (2008); Triple Plate 

Junction PLC (2010)

4

Tifalmin -5.046 141.208 Grass roots exploration project for copper-gold targets on 

old prospects in the Tifalmin-Nong River area; aeromagnetic 

surveys and and drilling underway in 2010. Exploration 

areas may include Star Mount Futik and Star Nong River 

deposits. Drilling (2010) at Olgal prospect intercepted 474 m 

at 0.42% Cu and 0.24 g/t Au. 

Highlands Pacific (2009a, 2011) 3

Ipi River -8.250 146.713 Petromin (2008) high priority exploration area for shallow 

epithermal Au to porphyry Cu-Au deposits based on 2007 

rock sample assays.

Petromin PNG Holdings 

Limited (2008)

1

Oram -9.869 148.291 Exploration license area (1,286 km2

) in Central and Oro 

Provinces, SE of Port Moresby. Explored for copper in the 

1970s (BHP) and 1980s (CRA); old targets warrant further 

exploration.

Triple Plate Junction PLC 

(2004)

2

Elo -9.374 147.518 Elo porphyry copper-gold-molybdenum system ~ 18 km 

NW of the Kodu Deposit. Elo exploration target based on 2 

km by 3 km elliptical topographic high, soil anomalies (max, 

0.12% Cu, 90 ppm Mo, 0.54 g/t Au), and trench results (212 

m of 0.08% Cu, 0.10 g.t Au). One drill hole intercepted 46 

m of 0.18% Cu, 0.17 g/t Au, 133 ppm Mo, and 0.6 g/t Ag. 

Frontier Resources, Ltd. (2007b, 

2008b)

2

Gusap -5.796 146.230 Finisterre Range: chalcopyrite float and gossan outcrop 

associated with Pliocene diorite; magnetic anomalies. 

Pacific Niugini (2010) 2

Zenag goldcopper project

-6.990 146.527 Porphyry copper-gold exploration target area mapped as 

Morobe Granodiorite; magnetic anomaly; surface Au and 

Cu 

Harmony Gold Mining Co. 

(2009), Pacific Niugini ( 2010)

1

Crater Mountain 

project

-6.356 145.086 Exploration license area for Porgera-type epithermal gold 

deposit; widespread argillic alteration at surface. Andesites, 

dacite, diorite with porphyry-style alteration; gold and 

elevated copper hosted in quartz-pyrite veins associated 

with diatreme-dome complex. Several undrilled prospects; 

reccent drilling focus on gold system. 

Christopher and Smith (2002); 

Gold Anomaly, Ltd. (2011) 

2

Mount Hagen -5.670 144.162 Exploration license area along Bismarck fault zone; 

Au,Cu, Mo associated with diorite and dacite along fault 

zone (NW-trending). Disseminated supergene chalcocite 

and covellite; hypogene chalcopyrite, bornite in quartz 

stockwork veinlets. Not drilled. 

Harmony Gold Mining Co. 

(2009), Pacific Niugini ( 2010)

2
228 Porphyry Copper Assessment of Southeast Asia and Melanesia

Bini porphyry, a dike-like K-rich calc-alkaline composite stock 

that has a circular topographic expression (Dugmore and others, 

1996), on the southeast side of the 10 by 4 km Pliocene Bavu 

Igneous Complex. Historical inferred resources of 85 Mt of 0.40 

percent copper and 0.60 g/t gold were reported on the basis of 

7 shallow diamond drill holes, open at depth and along strike. 

Revised resources (0.2 percent copper equivalent cut-off) based on 

additional drilling are reported as: indicated resources of 105 Mt 

grading 0.30 percent copper, 0.35 g/t gold, 68 ppm molybdenum, 

and 2.0 g/t silver; inferred resources of 171 Mt grading 0.26 percent copper, 0.27 g/t gold, 82 ppm molybdenum, and 1.6 g/t silver 

(Frontier Resources, Ltd., 2007a). A conceptual mining study 

suggested that a 10-year, 200 million-metric ton operation could 

potentially be economic. In 2008, a decision on land use (ecotourism and environmental concerns) led to cessation of further 

exploration and development at the Kodu deposit.

Prospects, Mineral Occurrences, and Related 

Deposit Types

Porphyry copper prospects and epithermal deposits or prospect areas that may be associated with porphyry copper deposits at 

depth are listed in table O4. The main prospect areas are discussed 

from west to east across the magmatic belt that defines the tract.

Sub-tract 009pCu7203a

Arnold and Griffin (1978) described characteristics 

of Mount Fubilan (Ok Tedi) and ten other prospects in the 

Tifalmin and Nong River areas of the Star Mountains (table 

O3, fig. O1). Resource estimates were deemed not practical 

or negligible for most of the prospects at the time; citing 

McGee (1976), Arnold and Griffin (1978) reported orderof-magnitude estimates for some of the prospects in the Star 

Mountains. Some of the prospects in the Star Mountains north 

of the Ok Tedi deposits are undergoing exploration (drilling, 

high-resolution airborne geophysical surveys) by Highlands 

Pacific, Ltd. (Highlands Pacific, Ltd., 2011). Drilling on the 

Olgal prospect in the Tifalmin area, which may be part of the 

undeveloped and perhaps incompletely delineated Star Mount 

Futik deposit of Singer and others (2008), intercepted 210 m 

of 0.50 percent copper and 0.37 g/t gold (Highlands Pacific, 

Ltd., 2011).

Sub-tract 009pCu7203b

Crater Mountain is a stratovolcano with a Pliocene-early 

Pleistocene andesitic phase and a Holocene basaltic phase. Mineralization at several prospects within the Crater Mountain explorationproject license areas is associated with the older phase andesite, 

dacite, and diorite plugs, and localized along north to northnortheast structures. Hydrothermally altered felsic to intermediate 

intrusive rocks with copper minerals are present; porphyry copper 

deposits may be associated with the epithermal gold systems at 

depth, but have not been drilled (Gold Anomaly, Ltd., 2011).

The Wamum prospect (Shedden, 1990) in the Edie porphyry 

has a reported noncompliant resource estimate of 45 Mt of 0.3 

percent copper, 0.12 g/t gold (Triple Plate Junction PLC, 2006).

Exploration in the Mount Bini area of the Central Province 

of Papua New Guinea identified several areas of porphyry CuAu-Mo mineralization in addition to the Kodu (Ofi Creek, Mount 

Bini) deposit. These include prospects and occurrences at Kodu 

Northwest (separated from Kodu by a ridge), Elo, and Oomargi 

(7 km northwest of Kodu), Tamala, and Ua-Ule. The Elo prospect, 18 km northwest of Kodu (Mount Bini), is an exploration 

target based on a 2 by 3 km elliptical topographic high along a 

northeast-trending lineament; drilling in 2007 indicated that Elo 

is molybdenum-rich compared with average grades observed at 

Kodu (Frontier Resources, Ltd., 2007b).

Gusap (table O4) is the only porphyry copper prospect that 

the team was aware of in the Finisterre Range-northeastern Papua 

New Guinea coastal area. However, much of the area is under 

exploration license.

Related Deposit Types

The Medial New Guinea magmatic belt includes at least 

nine significant intermediate-sulfidation, Pliocene to Pleistocene 

epithermal gold deposits (Garwin and others, 2005). The Porgera 

epithermal gold deposit is associated with a 6 Ma, epizonal, mafic, 

alkaline intrusive complex, coincident with a roughly circular 

aeromagnetic anomaly (Richards and Kerrich, 1993). Early stage 

(I) mineralization at Porgera is similar to porphyry, but higher 

in Au/Cu ratio and lacking in a potassic alteration zone (Richards and Kerrich, 1993). Porgera represents a gold-rich type of 

porphyry/epithermal gold deposit associated with mafic, alkaline 

magmatism; precursor magmatic-hydrothermal stages activity at 

such deposits rarely is economic (Richards, 1997). Similar alkaline rocks are present at the Mount Kare epithermal gold prospect, 

18 km southwest of Porgera (Richards and Kerrick, 1993).

The tract also includes exploration projects targeting epithermal gold (Kamitani and Naito, 1998; Porter Geoconsultancy, 2003; 

Papua New Guinea Mineral Resources Authority, 2008). Artisanal 

alluvial gold workings are present in many parts of the tract.

Exploration History

Exploration in the Star Mountains in the 1960s led to the 

discovery of Ok Tedi and other porphyry and skarn prospects. The 

Tifalmin prospects were drilled in the 1970s; the Geological Survey of Papua New Guinea continued geochemical and geophysical exploration in the area, which led to the discovery of the Nong 

River deposit (Arnold and Griffin, 1978). Abandoned prospects 

from 1970s-era exploration are currently being re-evaluated with 

aeromagnetic surveys and drilling (Highlands Pacific, 2009a).

Since the 1970s, there has been a long history of exploration using geochemistry, mapping, and geophysics (airborne 

and ground), mostly around or near known occurrences. The 

Wamum deposit was found by CRA Exploration in 1977 by 

using geochemical prospecting. The Wamum Idzan Creek 

gold-copper porphyry prospect in the Edie porphyry was 
Appendix O—Tract 009pCu7203 229

abandoned in the late 1990s; drilling returned 43.3 m grading 2.09 g/t gold and 0.68 percent copper and 36 m grading 

1.79 g/t gold and 0.45 percent copper at Idzan Creek. Recent 

exploration on a 2,500 km2 license area held by Triple Plate 

Junction PLC focuses on circular features, stream-sediment 

gold anomalies, and geophysical targets. Previous drill-defined 

resources for one of the prospect areas, Mt. Wamum, are 45 

Mt at 0.30 percent copper and 0.12 g/t gold.

Exploration at Crater Mountain in the 1970s focused on porphyry copper targets (Christopher and Smith, 2002). The focus then 

shifted to delineation of a Porgera-type epithermal gold deposit.

Many areas within the tract are remote, highly vegetated, 

and may not have been thoroughly explored. As of 2008, however, almost all of the areas covered by the permissive tracts 

in Papua New Guinea were under exploration license. The 

Yandera district, last explored in the 1960s, currently is being 

explored by Marengo Mining Limited (2009). The exploration focus is on circular, topographic highs, and historically 

partly explored prospects that have indications of copper and 

gold, alluvial gold, stream-sediment geochemical anomalies, 

geophysical anomalies, and northeasterly structural trends and 

lineaments, especially in areas between known mineralized 

centers along the same structural corridors.

Sources of Information

Principal sources of information used by the assessment 

team for delineation of tract 009pCu7203 are listed in table O5.

Grade and Tonnage Model Selection

Three of the six known deposits in the tract are classified 

as porphyry copper-gold deposits based on gold grades 

>0.2 g/t. Statistical tests (t-tests) comparing the deposits 

within each sub-tract with the global general and porphyry 

copper-gold subtype models indicate that either model is 

appropriate for the assessment (table6). Because half of the 

known deposits are copper-gold subtype, and that deposit 

type is representative of the New Guinea magmatic belt and 

other post-collisional porphyry systems, the assessment team 

selected the copper-gold subtype grade-tonnage model for the 

simulation of undiscovered resources.

Estimate of the Number of Undiscovered Deposits

Rationale for the Estimate

The tract contains six porphyry copper deposits that 

have identified resources; only Ok Tedi (sub-tract a) is in 

production. At least nine porphyry copper prospects are under 

evaluation (table O4); many of the historical prospects and 

abandoned mine areas were under exploration license in 2008 

(Papua New Guinea Mineral Resources Authority, 2008). The 

tract includes 46 copper occurrences (27 abandoned prospects 

and mines; 19 minor mineral occurrences) and 51 gold occurrences (nine abandoned or unworked mines or prospects, the 

rest are minor or alluvial gold workings).

Sub-tract a is partly well explored due to the presence of 

an active mine. The team concluded that there is a 50-percent 

chance that at least one additional deposit may be present 

in sub-tract a. Magnetic data suggest that additional shallow intrusions may be present between the cluster of known 

deposits and Porgera (fig. O1), which led to the estimate of a 

10-percent chance of four or more undiscovered deposits.

Sub-tract b has more volcanic cover than sub-tract a, is less 

thoroughly explored, and has a number of widespread exploration targets. The team considered that further exploration could 

reveal porphyry systems below, or proximal to, known epithermal gold deposits, such as Porgera. Sub-tract b contains three 

known deposits and 9 significant prospect areas. The 90-percent 

estimate of at least one deposit is based on the likelihood that 

the partially-drilled Wamum (Wau-Morobe) prospect or one of 

the other recent exploration projects could represent a deposit 

once fully delineated (rank 4, table O4). The team reasoned that 

about half (4) of the prospects could represent undiscovered 

deposits as the basis for the 50-percent estimate. Exploration 

in areas that have not previously received much exploration for 

porphyry copper deposits, such as the Finisterre Range, could 

yield new discoveries. Sub-tract b is three times the size of 

sub-tract a (table O6); prospects are widely dispersed. Given 

that some areas are poorly explored, and that modern geophysical exploration and drilling are increasingly targeting historical prospects and mineral occurrences, the team estimated a 

10-percent chance of 16 or more deposits, which is about twice 

the number of known prospects in the tract.

Probabilistic Assessment Simulation 

Results

Undiscovered resources for the tract were estimated by 

combining consensus estimates for numbers of undiscovered 

porphyry copper deposits with the porphyry copper-gold 

model of Singer and others (2008) using the EMINERS 

program (Root and others, 1992; Bawiec and Spanski, 2012; 

Duval, 2012). Selected simulation results are reported in table 

O7. Results of the Monte Carlo simulation are presented as a 

cumulative frequency plot (fig. O3). The cumulative frequency plot shows the estimated resource amounts associated 

with cumulative probabilities of occurrence, as well as the 

mean, for each commodity and for total mineralized rock. The 

mean amount of copper contained in undiscovered porphyry 

copper deposits within sub-tract a, 5.1 Mt of copper, is slightly 

less than the amount of identified copper resources (6.1 Mt). 

For sub-tract b, the mean amount of copper, 20 Mt, is almost 

double the 11.4 Mt of identified copper resources.
230 Porphyry Copper Assessment of Southeast Asia and Melanesia

Table O5. Principal sources of information used for tract 009pCu7203—Eastern Medial New Guinea Magmatic Belt, Papua New 

Guinea and Indonesia. 

[CCOP, Coordinating Committee for Coastal and Offshore Geoscience Programmes in East and Southeast Asia; NA, not applicable]

Theme Name or title Scale Citation

Geology Digital geologic map of East and Southeast Asia 1:2,000,000 CCOP and Geological Survey of Japan (1997)

Geology of Papua New Guinea 1;1,000,000 Bain (1972)

Digital geological map of Papua New Guinea 1:250,000 Papua New Guinea Geological Survey (2002)

Mineral 

occurrences

Porphyry copper deposits of the world: database, map, 

and grade and tonnage models

NA Singer and others (2008)

Digital geological map of Papua New Guinea 1:250,000 Papua New Guinea Geological Survey (2002)

Digital mineral occurrence database NA Directorate of Mineral Resources and Inventory (2004b)

MRDS database NA U.S. Geological Survey (2008)

Exploration USGS Minerals Yearbooks NA Wacaster (2010), Various (see references in table O4)

Company Web sites NA

Geophysics Central Highlands of Papua New Guinea magnetic data NA Mineral Resources Authority

Table O6. Undiscovered deposit estimates, deposit numbers, tract area, and deposit density for tract 009pCu7203, Eastern Medial 

New Guinea Magmatic Belt—Papua New Guinea and Indonesia.

[NXX, estimated number of deposits associated with the xxth percentile; Nund, expected number of undiscovered deposits; s, standard deviation; Cv%, coefficient of 

variance; Nknown, number of known deposits in the tract that are included in the grade and tonnage model; Ntotal, total of expected number of deposits plus known 

deposits; km2, area of permissive tract in square kilometers; Ntotal/100k km2, deposit density reported as the total number of deposits per 100,000 km2. Nund, s, and 

Cv% are calculated using a regression equation (Singer and Menzie, 2005)]

Consensus undiscovered deposit estimates Summary statistics Tract Area 

(km2

)

Deposit density 

(Ntotal/100k km2) N90 N50 N10 N05 N01 Nund s Cv% Nknown Ntotal

Sub-tract 009pCu7203a

0 1 4 4 4 1.60 1.54 97 3 4.6 14,230 32

Sub-tract 009pCu7203b

1 4 16 16 16 6.6 5.58 84 3 9.6 53,220 18

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Appendix O—Tract 009pCu7203 231

Table O7. Results of Monte Carlo simulations of undiscovered resources for tract 009pCu7203, Eastern Medial New Guinea Magmatic 

Belt—Papua New Guinea and Indonesia.

[Cu, copper; Mo, molybdenum; Au, gold; and Ag, silver; in metric tons; Rock, in million metric tons]

Material

Probability of at least the indicated amount Probability of

0.95 0.9 0.5 0.1 0.05 Mean Mean or 

greater

None

Sub-tract 009pCu7203a

Cu 0 0 1,200,000 12,000,000 24,000,000 5,100,000 0.23 0.29

Mo 0 0 0 63,000 150,000 29,000 0.17 0.59

Au 0 0 110 930 1,600 360 0.27 0.29

Ag 0 0 0 3,200 6,900 1,700 0.17 0.51

Rock 0 0 300 2,600 4,900 1,000 0.25 0.29

Sub-tract 009pCu7203b

Cu 0 390,000 10,000,000 55,000,000 76,000,000 20,000,000 0.34 0.07

Mo 0 0 28,000 360,000 580,000 120,000 0.26 0.25

Au 0 39 830 3,900 5,100 1,500 0.36 0.07

Ag 0 0 1,900 18,000 34,000 6,700 0.25 0.19

Rock 0 99 2,200 11,000 14,000 4,100 0.36 0.07

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Figure O1. Map showing the location, known deposits, and significant prospects and occurrences for permissive tract 009pCu7203, Medial New 

Papua New Guinea and Indonesia. ID, Indonesia; PG, Papua New Guinea; SB, Solomon Islands.

140° E 145° E 150° E

5° S

10° S

INDONESIA PAPUA NEW GUINEA

PAPUA NEW GUINEA

AUSTRALIA

Elo

Oram

Gusap

Yandera Porgera

Ok Tedi

Tifalmin

Mt. Hagen

Ipi River

Wamum (Wau-Morobe) Wafi-Golpu

Star Mt. Nong River

Crater Mountain Project

Zenag gold-copper project

Kodu (Ofi Creek,Mount Bini)

Star Mt. Futik 

Sub-tract aSub-tract b

Coral Sea Bismarck Sea Solomon Sea

130°E 

10°N

10°S

AUSTR

ID

PACIF

Political boundary source: U.S. Department of State (2009)Projection: Asia South Albers Equal Area Conic;Central meridian 145° E; latitude of origin 15° S

0 50 100 150 200 KILOMETERS

0 50 100 MILES

EX

OtheAsse142pPorpdepotract

Porpprostrac
( ( ( ( ( ( ( ( ( ( ( ( 

( ( ( ( ( ( ( ( ( ( (

( (

(

( ( ( ( ( ( ( (

(

( ( ( (

( ( Central Highlands

Peninsular Papua New Guinea

Finisterre Range

RAMU-MARKHAM FAULT

PAPUA NEW GUINEA

INDONESIA

PAPUA NEW GUINEA

AUSTRALIA

Coral Sea Bismarck Sea Solomon Sea Elo Oram Gusap Yandera Porgera Ok Tedi Tifalmin Mt. Hagen Ipi River Wafi-Golpu Wamum (Wau-Morobe) Star Mt. Nong River Crater Mountain Project Zenag gold-copper project Kodu (Ofi Creek,Mount Bini) Star Mt. Futik Sub-tract a Sub-tract b

140° E 144° E 148° E

4° S8° S

Base from ESRI ArcGIS Online (2009)World Shaded ReliefPolitical boundary source: U.S. Department of State (2009)Projection: Asia South Albers Equal Area Conic;Central meridian 146° E; latitude of origin 15° S

0 50 100 150 200 KILOMETERS

0 50 100 MILES

E

Ass 0PePe

( ( Su

PoPo

Figure O2. Sub-tracts of 009pCu7203, Medial New Guinea Magmatic Belt—Papua New Guinea and Indonesia, shown on a shaded relief map of 

illustrate the extent of the highlands areas, with mapped areas of surface exposures of late Miocene-Pliocene igneous rocks permissive for the ocopper deposits. Sub-tract a is the Indonesia-Papua New Guinea border area. Sub-tract b includes permissive rocks in the Central Highlands of PFinisterre Range, the Peninsular area of southeastern Papua New Guinea, and the D’Entrecasteaux Islands.
238 Porphyry Copper Assessment of Southeast Asia and Melanesia

1.00

0.90

0.80

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

Probability

0.01 0.1 1 10 100 1k 10k 100k 1M 10M 100M 1B 10B 100B

Material, in metric tons

Mean Cu

Mean Mo

Mean Au

Mean Ag

Mean Rock

B Cu

Mo

Au

Ag

Rock

Mean Cu

Mean Mo

Mean Au

Mean Ag

Mean Rock

EXPLANATION

1.00

0.90

0.80

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

Probability

0.01 0.1 1 10 100 1k 10k 100k 1M 10M 100M 1B 10B 100B

Material, in metric tons

Mean Cu

Mean Mo

Mean Au

Mean Ag

Mean Rock

Cu

Mo

Au

Ag

Rock

Mean Cu

Mean Mo

Mean Au

Mean Ag

Mean Rock

EXPLANATION

A

Figure O3. Cumulative frequency plots showing the results of Monte Carlo computer simulation of undiscovered 

resources in 009pCu7203, Medial New Guinea Magmatic Belt—Papua New Guinea and Indonesia. A, Sub-tract 

009pCu7203a. B, Sub-tract 009pCu7203b. k, thousands; M, millions; B, billions; Tr, trillions.
Appendix P—Tract 009pCu7205 239

Appendix P. Porphyry Copper Assessment for Tract 009pCu7205, 

Maramuni Arc—Papua New Guinea

By Jane M. Hammarstrom1, Dulcie Saroa2, Bambang Tjahjono Setiabudi3, Dwi Nugrono Sunuhadi3, 

Gilpin R. Robinson, Jr.1

, Connie L. Dicken1, Steve Ludington4, Arthur A. Bookstrom5, and Michael L. Zientek5, 

with contributions from Gwaibo Kopi2

 and Dennis P. Cox4

Deposit Type Assessed: Porphyry copper, copper-gold subtype

Descriptive models: Porphyry copper (Berger and others, 2008; John and others, 2010); Porphyry copper-gold 

(Cox, 1986; Cooke and others,1998)

Grade and tonnage model: Porphyry copper, copper-gold subtype (Singer and others, 2008)

Table P1 summarizes selected assessment results.

Table P1. Summary of selected resource assessment results for tract 009pCu7205, Maramuni Arc—Papua New Guinea.

[km, kilometers; km2, square kilometers; t, metric tons] 

Date of 

assessment

Assessment

depth (km)

Tract area 

(km2)

Known copper 

resources (t)

Mean estimate of undiscovered copper resources 

(t)

Median estimate of 

undiscovered copper 

resources (t)

February 2010 1 38,970 8,550,000 9,900,000 3,300,000

Location

The tract is in the central part of New Guinea Island, Papua New Guinea (fig. P1).

Geologic Feature Assessed

Miocene Maramuni magmatic arc.

Delineation of the Permissive Tract

Tectonic Setting

The tract delineates igneous rocks associated with the Miocene Maramuni Arc in Papua New Guinea. The Maramuni Arc 

probably formed in middle Miocene time as a result of southwest-dipping subduction of the Solomon Sea Plate beneath eastern 

1

U.S. Geological Survey, Reston, Virginia, United States.

2

Mineral Resources Authority, Papua New Guinea.

3

Center for Geological Resources, Geological Agency of Indonesia, West Java, Indonesia.

4

U.S. Geological Survey, Menlo Park, California, United States.

5

U.S. Geological Survey, Spokane, Washington, United States.
240 Porphyry Copper Assessment of Southeast Asia and Melanesia

New Guinea. Most authors contend that the Maramuni Arc 

does not extend west of the Papua New Guinea-Irian Jaya 

border (as shown on figures by Garwin and others, 2005). The 

Maramuni Arc lies south of the Melanesian Arc terrane and 

north of the Medial New Guinea magmatic belt, although there 

are some areas of overlap (fig. 7). The northern border of the 

tract lies south of the Ramu-Markham Fault Zone in eastern 

Papua New Guinea. Margins of Maramuni Arc intrusions are 

the locus of many of the late Miocene to Pliocene intrusions 

of the Central Highlands Belt. The assessment team followed 

the general arc classification of Garwin and others (2005). 

Maramuni magmatism was volumetrically more extensive, 

formed large plutons and batholithic complexes, and the rocks 

are more deeply eroded than the hypabyssal diatremes, dikes, 

and small stocks that characterized the late Miocene to Pliocene magmatic event. Findley (2003) noted that the concept of 

a Maramuni Arc was postulated in the 1970s to explain 18–12 

Ma middle Miocene calc-alkaline magmatism in Papua New 

Guinea; he attributed the younger late Miocene-Pliocene magmatism in the area (tract 009pCu7203) to the same process 

and, therefore, questioned separating the two events.

Equivalent-age igneous rocks in the Moon-Utawa Arc 

of Indonesia are delineated as tract 142pCu7205. The Moon 

Volcanics may be linked to the Maramuni Arc, but as noted 

by Malaihollo and Hall (1996), the nature and distribution of 

the volcanism and its relation to the Maramuni rocks remains 

unclear.

Geologic Criteria

The tract was constructed in a GIS using a digital 

compilation of 1:250,000-scale geologic maps of Papua New 

Guinea. Maps and figures showing the major faults, lineaments, and tectonic divisions of New Guinea by Garwin and 

others (2005), Hill and others (2002), Quarles van Ufford and 

Cloos (2005), and Cloos and others (2005) also were used. 

Map units were classified into generalized units by age and 

lithologic class (igneous volcanic, igneous plutonic). From this 

digital database of geologic lithology and age attributes, all 

igneous rocks of Miocene age (>7 Ma and exclusive of rocks 

mapped as late Miocene or younger) were selected. Using 

GIS tools, a 5-km buffer was applied around mapped igneous 

contacts of permissive lithologies to account for spatial uncertainty in digitized geology and for the possibility of greater 

extent of permissive rocks within a kilometer of the surface. 

Ophiolites, ultramafic rocks, and basaltic units were deemed 

nonpermissive and are omitted from the tract.

The final tract boundaries were established by GIS 

processing and editing. The processing approximates manual 

delineation of tracts but is rapid and reproducible. The 

processing steps included (1) unioning all buffered permissive map units and other polygon features that comprise the 

framework of the tract; (2) aggregating unioned polygons 

using an aggregation distance of 15 km and a minimum hole 

size of 1,000 m2

, a step done to group closely spaced permissive areas; (3) manually aggregation and adjustment of tract 

areas; and (4) smoothing of polygons. Preliminary tracts 

were cleaned to remove necking and thinning introduced by 

processing and compared with source maps to ensure that 

original permissive boundaries and buffer distances were 

honored. Regional and local mineral occurrence, geochemical, 

and isotopic-age data were plotted and used to constrain or 

expand tract boundaries; in particular, a database of isotopic 

ages of igneous rocks for Papua New Guinea compiled by the 

Southeast Asia Research Group provided additional controls 

on distributions of permissive rocks by providing locations of 

dated samples and lithologic information (Malaihollo and others, 2002). Tract boundaries were clipped at shorelines (U.S. 

Department of State, 2009).

The resulting tract outlines early to middle Miocene and 

middle to late Miocene intrusive and volcanic rocks of the 

1,000-km-long Maramuni Arc. Igneous rocks designated as 

late Miocene to Pliocene are excluded (see tract 009pCu7203). 

Miocene rocks crop out within the mobile belt along the northern margin of the Central Highlands of Papua New Guinea 

(fig. P2). The tract primarily is based on the mapped extent of 

the rocks listed in table P2. Intrusive rocks are exposed along 

the northern part of the east-west-trending arc; volcanic rocks 

are confined to the southern part of the arc (fig. P2). Late Miocene to Pliocene rocks generally are present to the south of the 

Maramuni Arc; however, some of the younger rocks intrude 

along the margins of the intrusive rocks of the Maramuni Arc, 

and along arc-transverse northeast-trending structures. Part of 

the tract was extended north and west of the Salumei prospect 

(fig. P2) based on aeromagnetic data and topography.

Known Deposits

The Frieda River, Yandera, and Wafi-Golpu porphyry 

copper deposits lie within the Maramuni Arc according to 

Garwin and others (2005). Both Wafi-Golpu and Yandera are 

proximal to younger (<7 Ma) late Miocene-Pliocene intrusions 

that were emplaced into, or along the margins of older Maramuni-age rocks. The team arbitrarily assigned Wafi (possibly 

as young as 9 Ma) and Yandera (7 Ma) to the late MiocenePliocene Eastern Medial New Guinea magmatic belt (tract 

009pCu7203B). Therefore, the 12 Ma Frieda River project is 

the only deposit with identified resources that we included as 

belonging to the Maramuni tract (table 3).

The Frieda River Intrusive Complex initially was 

explored in the 1960s. Continued exploration led to discovery 

of the Nena copper-gold high-sulfidation deposit in 1977 by 

regional reconnaissance (Bainbridge and others, 1998); the 

discovery was made by following the source of copper float. 

At Nena, weathering has leached copper from an oxidized, 

gold-rich supergene cap; chalcocite and covellite form a 

supergene blanket below the gold zone (Lole, 2005). Drilling 

to 780 m below the covellite zone at Nena intercepted weaklyaltered porphyry-copper style mineralization characterized as 

biotite-quartz alteration of porphyry containing chalcopyrite 

and bornite (Bainbridge and others, 1998; Onglo and others, 

2008). Horse/Ivaal and Koki are porphyry copper deposits 
Appendix P—Tract 009pCu7205 241

Table P2. Map units that define tract 009pCu7205, Maramuni Arc—Papua New Guinea.

[Map unit, age range, and principal lithologies are based on a attributes in a digital compilation of geologic maps of Papua New Guinea Indonesia (Papua New 

Guinea Geological Survey, 2002). Numbers and publication dates of 1:250,000-scale maps avaiable from the Papua New Guinea Geological Survey are listed for 

reference – –, no map unit] 

Map unit Map 

symbol Lithology Age range Map number

Map 

date

Intrusive rocks 

 – – Ti Diorite, porphyritic microdiorite Part Eocene, 

Oligocene to 

middle Miocene

B5403 1979

Ananadi Diorite Tma Hornblende and quartz monzonite; gabbro, granophyre Early Miocene B5403 1979

Akuna Intrusive Complex Tmak Gabbro, porphyritic dolerite, diorite; minor granodiorite Early Miocene B5510 1972

Bismarck Intrusive 

Complex

Tmb Gabbro, diorite; minor tonalite, granodiorite, mangerite, granite, 

aplite, pegmatite, hornblendite, dunite, peridotite, anorthosite

Middle Miocene B5505 1971

Frieda Complex (Older 

intrusives)

Tmf Biotite-hornblende-quartz microdiorite and porphyry, hornblendequartz diorite and andesitic porphyry; propylitic, silicic and 

potassic alteration; disseminated Cu, Au mineralization

Middle Miocene B5403 1979

Hunstein and Chambri 

stocks

Tmh Monzonite, granodiorite, diorite: Hunstein and Chambri stocks Early Miocene B5404 1979

Nekiei batholith Tmi Granodiorite, diorite, some porphyry Miocene B5404 1979

Oipo Intrusives Tmi? Gabbro, granodiorite, tonalite, diorite, pyroxenite, lamprophyre Middle Miocene B5505 1971

Tarua stock Tmit Granodiorite, diorite Middle Miocene B5408 1980

Wale batholith Tmiw Grandodiorite, diorite; plagioclase-pyroxene porphyry with much 

opaques (Timun area)

Middle Miocene B5408 1980

Kimil Diorite Tmk Diorite, gabbro, tonalite, granodiorite; andesite porphyry, dolerite 

and basalt dykes; minor trachyandesite

Middle Miocene B5505 1971

Frieda Complex (Younger 

intrusives)

Tmk (Biotite-) hornblende-quartz diorite, diorite and andesitic porphyry, 

unaltered, acicular hornblende typical

Middle Miocene B5403 1979

Kenangi Gabbro Tmke Gabbro, mangerite, granodiorite Middle Miocene B5509 1971
242 Porphyry Copper Assessment of Southeast Asia and Melanesia

Table P2. Map units that define tract 009pCu7205, Maramuni Arc—Papua New Guinea.—Continued

Map unit Map 

symbol Lithology Age range Map number

Map 

date

Intrusive rocks 

Morobe Granodiorite Tmm Granodiorite, adamellite; minor monzonite, diorite, 

pegmatite

Middle Miocene B5510 1972

Maramuni Diorite Tmm Diorite, microdiorite, granodiorite; minor gabbro, 

rhyodacite, porphyry, monzonite; andesite and dolerite 

dykes

Middle Miocene B5505 1971

Nena Diorite Tmn Medium to fine quartz diorite Middle Miocene B5403 1979

Yuat North batholith and stocks Tmny Diorite, granodiorite, some porphyry Early to middle Miocene B5404 1979

Karawari batholith Tmr Diorite, granodiorite, some porphyry: Karawari batholith Middle to late Miocene B5404 1979

Yuat South batholith Tmsy Granodiorite, minor diorite, some gabbro Middle to late Miocene B5408 1980

Manawai Diorite Tom Diorite, some gabbro, inliers of hornfels and chert Middle Oligocene B5403 1979

Paupe Granodiorite Top Hornblende granodiorite, slightly altered Late Oligocene B5403 1979

 – – Ts Gabbro, andesitic porphyry, diorite Early Miocene? B5510 1972

Maumiavi Diorite Tv Diorite, some tonalite, monzonite, adamellite, 

rare porphyry

Part Eocene, 

early Miocene

B5403 1979

Yaveufa Formation Tma, 

Tmay1

Volcanolithic conglomerate, greywacke, tuff Middle Miocene B5510 1972

Volcanic rocks 

Frieda Complex - Debom 

Volcanics

Tmd Porphyritic hornblende andesite lava, pyroclastics, 

sediments

Middle Miocene B5403 1979

Tarua Volcanics Tmt Andesitic and basaltic lava, agglomerate, tuff, 

minor pillow lava

Middle Miocene B5408 1980
Appendix P—Tract 009pCu7205 243

within a 3 km2 zone in the southeastern part of the intrusive 

complex. The deposits are associated with multiphase intrusions. Chalcopyrite and bornite are the main ore minerals, with 

some development of supergene chalcocite (Lole, 2005).

The Frieda River Intrusive Complex contains at least 

seven centers of porphyry copper mineralization, including the Horse-Ivaal-Trukai deposit, and is considered one of 

the world’s largest undeveloped porphyry copper and gold 

deposits with estimated resources of more than 7 Mt of copper 

and 14.3 million ounces of gold (D. Saroa, written commun., 

2010). Recent updates put the estimated copper resource at 8.5 

Mt (Xstrata Copper, 2011).

Table P3. Identified porphyry copper resources in tract 009pCu7205, Maramuni Arc—Papua New Guinea. 

[Ma, million years; Mt, million metric tons; t, metric ton; %, percent; g/t, gram per metric ton; Cu-Mo subtype, deposits that have Au/Mo ratios <3 or average Mo 

grades >0.03%; Cu-Au subtype, deposits that have Au/Mo ratios >30 or average Au grades >0.2 g/t; NA, not applicable. Contained Cu in metric tons is computed 

as tonnage (Mt × 1,000,000) × Cu grade (%). *, includes Horse-Ivaal-Trukai total resources at 0.2% copper cutoff grade from Xstrata Copper (2011); (Mo) from 

Singer and others (2008)]

Name Latitude Longitude Subtype Age 

(Ma) Tonnage

Grade Contained 

Cu (t) Reference

Cu (%) Mo (%) Au (g/t) Ag (g/t)

Frieda River* -4.7 141.783 Cu-Au 12 1,900 0.45 (0.004) 0.22 0.7 8,550,000 Andrew (1995), 

Highlands Pacific 

(2009a,b), Singer 

and others (2008), 

Xstrata Copper 

(2011)

Table P4. Significant prospects and occurrences tract 009pCu7205, Maramuni Arc—Papua New Guinea. 

[Rank 2=drilled or trenched with <20 m of 0.2% Cu or <0.2% Cu, or past or ongoing exploration. Rank 1=copper occurrence that may be related to porphyry-type 

mineralization based on stream sediment or magnetic anomaly or location along structural trend] 

Name Latitude Longitude Comments Reference Rank

Salumei -4.477 142.692 Grass roots exploration project. Exploration focus (Sierra Mining): 

gold target and secondary copper enrichment over copper prospects

Sierra Mining, Limited 

(2008)

1

Bismarck -5.225 144.008 Exploration project areas focused on gold; includes some prospect 

areas with features compatible with porphyry copper mineralization: 

Cu and Au anomalies in stream sediments, soils and bedrock associated 

with potassically-altered granodiorite, disseminated pyrite and minor 

chalcopyrite, bornite, chalcocite, molybdenite. Associated with midMiocene Yuat South batholith. 

Stagg and Swriridiuk (2007) 1

Wasi -4.724 142.371 Porphyry Cu-Au-Mo prospect; limited previous drilling. Mapping 

and soil sampling in 2010; Au,Cu, Mo soil anomalies (peak values 

0.11% Cu, 3.2 g/t Au). Outcrop assayed 0.21% Cu, 872 ppm Mo. 

Location based on company map; appears to be on W flank of a small 

stock mapped as Oligocene to middle Miocene diorite, porphyritic 

microdiorite. 

Frontier Resources (2010) 2
244 Porphyry Copper Assessment of Southeast Asia and Melanesia

Prospects, Mineral Occurrences, and Related 

Deposit Types

The tract includes three porphyry copper prospects (table 

P4), none of which are proven by drilling to date. In addition, the tract includes 59 copper occurrences where copper is reported as the primary commodity (15 prospects and 

unworked or abandoned mines and prospects; the remainder 

are reported as minor mineral occurrences). Gold is reported 

as the main commodity at 64 sites, including 18 minor mineral 

occurrences, 7 unworked or abandoned mines and prospects, 

and 39 alluvial gold workings (Papua New Guinea Mineral 

Resource Authority, 2002).

Exploration History

The entire tract area was under exploration lease, or 

application for exploration lease, in 2008 (Papua New Guinea 

Mineral Resources Authority, 2008).

Sources of Information

Principal sources of information used by the assessment 

team are listed in table P5.

Grade and Tonnage Model Selection

Frieda River is classified as a porphyry copper-gold 

deposit based on reported gold grades and Au/Mo ratio >30. 

The grade and tonnage data fit either the global general or 

copper-gold subtype models based on analysis of variance 

(ANOVA) (see table 6 of main report). The copper-gold 

subtype model was selected based on the classification of the 

deposit and the likelihood that other deposits in the tract will 

be gold-rich.

Estimate of the Number of Undiscovered Deposits

Rationale for the Estimate

Based on geologic maps, the apparent volume of exposed 

intrusive rocks exceeds the volume of preserved volcanic 

rocks; volcanic rocks are more abundant in the southern part 

of the tract. The tract contains one known deposit, and three 

exploration projects targeting porphyry copper deposits, as 

well as numerous copper and gold occurrences. Based on 

Table P5. Principal sources of information used for tract 009pCu7205, Maramuni Arc—Papua New Guinea. 

[NA, not applicable; CCOP, Coordinating Committee for Geoscience Programmes in East and Southeast Asia]

Theme Map or title Scale Citation

Geology Geology of Papua New Guinea 1;1,000,000 Bain and others (1972)

Digital geology of Papua New Guinea 1:250,000 Papua New Guinea Geological Survey (2002)

Page size maps in published papers NA Garwin and others (2005), Hill and others (2002), Quarles 

van Ufford and Cloos (2005), and Cloos and others (2005) 

SE Asia Radiometric Ages: GIS Database NA Malaihollo and others (2002)

Mineral 

occurrences

Porphyry copper deposits of the world: 

database, map, and grade and tonnage models

NA Singer and others (2008)

Digital geology of Papua New Guinea 1:250,000 Papua New Guinea Geological Survey ( 2002)

Exploration Company Web sites NA Sierra Mining Limited (2008), Xstrata Copper (2010, 2011)

Quarterly report Papua New Guinea Mineral Resources Authority (2008a) 

Papua New Guinea Mineral Resources 

Authority tenement maps

Papua New Guinea Mineral Resources Authority (2008b) 

CCOP country report Dulcie Saroa (oral commun., 2010)
Appendix P—Tract 009pCu7205 245

this information, the team reasoned that at least two of the 

three known prospect areas might, if fully explored, represent 

deposits like those in the grade and tonnage model. The recent 

(2007 to present) upswing in exploration activity prompted by 

high gold prices and the large number of exploration concessions that cover the area suggest that modern exploration 

drilling and use of geophysics, especially along prospective 

structural corridors may lead to additional deposit discoveries. This consideration led the team to consider the possibility 

that more deposits might be found within the tract area. The 

team estimated a 50-percent chance of two or more deposits 

and a 10-percent chance of eight or more deposits (P6), which 

results in a mean of 3.2± 3.0 deposits (table P6).

Probabilistic Assessment Simulation 

Results

Undiscovered resources for the tract were estimated by 

combining consensus estimates for numbers of undiscovered 

porphyry copper deposits with the porphyry copper-gold 

model of Singer and others (2008) using the EMINERS 

program (Root and others, 1992; Bawiec and Spanski, 2012; 

Duval, 2012). Selected simulation results are reported in table 

P7. Results of the Monte Carlo simulation are presented as a 

cumulative frequency plot (fig. P3). The cumulative frequency 

plot shows the estimated resource amounts associated with 

cumulative probabilities of occurrence, as well as the mean, 

for each commodity and for total mineralized rock. The mean 

amount of copper (9.9 Mt) represents 1.8 times the identified 

resources (5.5 Mt). The median expected value (3.3 Mt) is less 

than the identified resources at the Frieda River deposit. The 

simulation predicts a mean of 710 t, or about twice as much 

gold as identified at Frieda River (418 t), and a median of 290 

t of gold for the tract. See table 7 in the main report for comparisons with identified resources and with other tracts.

References Cited

Andrew, R.L., 1995, Porphyry copper-gold deposits of the 

southwest Pacific: Mining Engineering, v. 47, no. 1, 

p. 33–38.

Table P6. Undiscovered deposit estimates, deposit numbers, tract area, and deposit density for tract 009pCu7205, Maramuni Arc—

Papua New Guinea. 

[NXX, estimated number of deposits associated with the xxth percentile; Nund, expected number of undiscovered deposits; s, standard deviation; Cv%, coefficient of 

variance; Nknown, number of known deposits in the tract that are included in the grade and tonnage model; Ntotal, total of expected number of deposits plus known 

deposits; km2, area of permissive tract in square kilometers; Ntotal/100k km2, deposit density reported as the total number of deposits per 100,000 km2. Nund, s, and 

Cv% are calculated using a regression equation (Singer and Menzie, 2005)]

 Consensus undiscovered deposit estimates Summary statistics Tract area 

(km2

)

Deposit density 

(Ntotal/100k km2) N90 N50 N10 N05 N01 Nund s Cv% Nknown Ntotal

0 2 8 8 8 3.2 3 93 1 4.2 38,970 11

Table P7. Results of Monte Carlo simulations of undiscovered resources for tract 009pCu7205, Maramuni Arc—Papua New Guinea. 

[Cu, copper; Mo, molybdenum; Au, gold; and Ag, silver; in metric tons; Rock, in million metric tons]

Material

Probability of at least the indicated amount based on the Cu-Au subtype model Probability of

0.95 0.9 0.5 0.1 0.05 Mean Mean or 

greater

 None

Cu 0 0 3,300,000 27,000,000 44,000,000 9,900,000 0.28 0.20

Mo 0 0 4,300 140,000 320,000 56,000 0.21 0.43

Au 0 0 290 2,000 2,900 710 0.32 0.20

Ag 0 0 530 7,400 15,000 3,200 0.21 0.37

Rock 0 0 720 5,700 8,900 2,000 0.30 0.20
246 Porphyry Copper Assessment of Southeast Asia and Melanesia

Bain, J.H.C., Davies, H.L., Hohnen, P.D., Ryburn, R.J., Smith, 

I.E., Grainger, R., Tingey, R.J. and Moffar, M.R., compilers, 

1972, Geology of Papua New Guinea, Canberra: Bureau of 

Mineral Resources, Geology and Geophysics, 1 map, 

4 sheets, scale 1:1,000,000.

Bainbridge, A.L., Hitchman, S.P., and De Ross, G.J., 

1998, Nena copper-gold deposit, in Berkman, D.A., and 

Mackenzie, D.H., eds., Geology of Australian and Papua 

New Guinea mineral deposits: Melbourne, Australasian 

Institute of Mining and Metallurgy Monograph 22, 

p. 855–861.

Bawiec, W.J., and Spanski, G.T., 2012, Quick-start guide for 

version 3.0 of EMINERS—Economic Mineral Resource 

Simulator: U.S. Geological Survey Open-File Report 

2009–1057, 26 p., accessed June 30, 2012, at http://pubs.

usgs.gov/of/2009/1057. (This report supplements USGS 

OFR 2004–1344.)

Cloos, Mark, Sapiie, B., Quarles van Ufford, A., Weiland, 

R.J., Warren, P.Q., and McMahon, T.P., 2005, Collisional 

delamination in New Guinea—The geotectonics of 

subducting slab breakoff: Geological Society of America 

Special Paper 400, 51 p.

Cooke, D.R., Heithersay, P.S., Wolfe, R., and Calderon, A.L., 

1998, Australian and western Pacific porphyry Cu-Au 

deposits: Journal of Australian Geology and Geophysics, 

v. 17, no. 4, p. 97–104.

Coordinating Committee for Coastal and Offshore Geoscience 

Programmes in East and Southeast Asia (CCOP) and 

Geological Survey of Japan, 1997, Digital geologic map 

of East and Southeast Asia: Geological Survey of Japan, 

Digital Geoscience Map G-2 scale 1:2,000,000, CD-ROM.

Cox, D.P., 1986, Descriptive model of porphyry Cu-Au, in

Cox, D.P., and Singer, D.A., eds., Mineral deposit models: 

U.S. Geological Survey Bulletin 1693, p. 110.

Cox, D.P., Williamson, A., Rogerson, R., and Finlayson, E.J., 

1986, Mineral deposit models applicable to Papua New Guinea: 

Geological Survey of Papua New Guinea, Report 86/5.

Duval, J.S., 2012, Version 3.0 of EMINERS—Economic 

Mineral Resource Simulator: U.S. Geological Survey Open 

File Report 2004–1344, accessed July 5, 2012, at http://

pubs.usgs.gov/of/2004/1344.

Findley, R.H., 2003, Collision tectonics of northern Papua 

New Guinea—Key field relationships demand a new 

model, in Hillis, R.R., and Müller, R.D., eds., Evolution 

and dynamics of the Australian Plate: Geological Society of 

America Special Paper 372, p. 291–307.

Frontier Resources, 2010, Frontier Resources discovers major 

gold anomaly at Wasi prospect: accessed July 15, 

2010, at http://www.proactiveinvestors.co.uk/companies/

news/16885/frontier-resources-discovers-major-goldanomoly-at-wasi-prospect-16885.html.

Garwin, S., Hall, R., and Watanabe, Y., 2005, Tectonic setting, 

geology, and gold and copper mineralization in Cenozoic 

magmatic arcs of southeast Asia and the west Pacific, in 

Hedenquist, T.W., Thompson, J.F.H., Goldfarb, R.J., and 

Richards, J.P., eds., One hundredth anniversary volume 

1905–2005: Littleton, Colorado, Society of Economic 

Geologists, p. 891–930.

Highlands Pacific, 2009a, December 2009 Quarterly report: 

accessed January 15, 2010, at www.highlandspacific.com/

pdf/Dec_Quarterly_2009.pdf.

Highlands Pacific, 2009b, Update, Frieda Copper project, 

PNG: accessed January 15, 2010, at http://www.pomsox.

com.pg/publications/02112009__deep_drill_hole_frieda.

pdf.

Hill, K.C., Kendrick, R.D., Crowhurst, P.V., and Gow, P.A., 

2002, Copper-gold mineralisation in New Guinea—

Tectonics, lineaments, thermochronology and structure, in 

Korsch, R.J., ed., Geodynamics of Australia and its mineral 

systems—Technologies, syntheses and regional studies: 

Melbourne, Australia, Blackwell Scientific Publications for 

the Geological Society of Australia, p. 737–752.

John, D.A., Ayuso, R.A., Barton, M.D., Blakely, R.J., Bodnar, 

R.J., Dilles, J.H., Gray, Floyd, Graybeal, F.T., Mars, J.C., 

McPhee, D.K., Seal, R.R., Taylor, R.D., and Vikre, P.G., 

2010, Porphyry copper deposit model, chap. B of Mineral 

deposit models for resource assessment: U.S. Geological 

Survey Scientific Investigations Report 2010–5070–B, 

169 p., accessed September 8, 2010, at http://pubs.usgs.gov/

sir/2010/5070/b/.

Lole, H., 2005, The exploration of potential mineral resources 

in Papua New Guinea, 3rd PECC mineral network meeting 

(mining economy and development, and environmental 

protection), 26 p.: accessed July 15, 2010, at http://www.

pecc.org/resources/doc_view/1295-the-exploration-ofpotential-mineral-resources-in-papua-new-guinea-paper.

Malaihollo, J.F.A., Hall, R., and Macpherson, C.G., 2002, SE 

Asia radiometric ages—GIS database: accessed January 15, 

2010, at http://searg.rhul.ac.uk/current_research/isotopic_

ages/SEAsia_GIS.pdf.

Onglo, Joseph, Kajiwara, Y., Hawkins, M.A., and Bainbridge, 

T., 2008, Hydrothermal alteration and Cu-Au mineralization 

at Nena high sulfidation-type deposit, Frieda River, Papua 

New Guinea: Resource Geology, v. 52, p. 301–313.

Papua New Guinea Geological Survey, 2002, Digital 

geological map of Papua New Guinea: Australia, Australian 

Geosciences, scale 1:250,000.
Appendix P—Tract 009pCu7205 247

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Quarterly bulletin: accessed July 10, 2009, at http://www.

mra.gov.pg/Portals/0/Publications/bulletin/julysep08/

current%20el%20map.pdf.

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New Guinea mines and potential projects map updated to 

2008: accessed July 10, 2009, at http://www.mra.gov.pg/

Portals/0/Mining%20Infor/projects%20map.pdf.

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tectonics of New Guinea: Bulletin of the American 

Association of Petroleum Geologists, v. 89, no. 1, 

p. 119–140.

Rogerson, R., and McKee, C., 1990, Geology, volcanism and 

mineral deposits of Papua New Guinea, in Hughes, F.E., ed., 

Geology of the mineral deposits of Australia and Papua New 

Guinea: The Australasian Institute of Mining and Metallurgy, 

Monograph 14, p. 1699–1701.

Rogerson, R., Williamson, A., and Francis, G., 1986, Recent 

advances in the knowledge of geology, energy resources and 

metallogenesis of Papua New Guinea since 1981: GEOSEA 

V Proceedings, v. 2, Geological Society Malaysia Bulletin 

20, p. 23–37.

Root, D.H., Menzie, W.D., and Scott, W.A., 1992, Computer 

Monte Carlo simulation in quantitative resource estimation: 

Natural Resources Research, v. 1, no. 2, p. 125–138.

Sierra Mining Limited, 2008, Papua New Guinea: accessed 

January 15, 2010, at http://sierramining.com.au/?id=321.

Sillitoe, R.H., 1995, Exploration and discovery of base- and 

precious-metal deposits in the Circum-Pacific region during 

the last 25 years: Tokyo, Society of Resource Geology, 

Resource Geology Special Issue no. 19, 119 p.

Singer, D.A., and Menzie, W.D., 2005, Statistical guides 

to estimating the number of undiscovered mineral 

deposits—An example with porphyry copper deposits, 

in Cheng, Qiuming, and Bonham-Carter, Graeme, eds., 

Proceedings of IAMG—The annual conference of the 

International Association for Mathematical Geology: 

Toronto, Canada, York University, Geomatics Research 

Laboratory, p. 1028–1033.

Singer, D.A., Berger, V.I., and Moring, B.C., 2008, 

Porphyry copper deposits of the world—Database and 

grade and tonnage models, 2008: U.S. Geological Survey 

Open-File Report 2008–1155, accessed June 1, 2011, at 

http://pubs.usgs.gov/of/2008/1155/.

Stagg, R.N., and Swiridiuk, Peter, 2007, Technical report 

on the Bismarck property, Enga Province, Papua New 

Guinea: Technical report, 27 p.

U.S. Department of State, 2009, Small-scale digital 

international land boundaries (SSIB)—Lines, edition 

10, and polygons, beta edition 1, in Boundaries and 

sovereignty encyclopedia (B.A.S.E.): U.S. Department of 

State, Office of the Geographer and Global Issues.

Xstrata Copper, 2010, Xstrata Copper announces mineral 

resource update for the Frieda River copper-gold project 

in Papua New Guinea: Xstrata Copper news release, 

accessed March 15, 2010, at http://www.xstrata.com/

media/news/2010/01/21/2321CET/pdf.

Xstrata Copper, 2011, Xstrata Copper announces mineral 

resource increase for the Frieda River copper-gold project 

in Papua New Guinea: Xstrata Copper news release dated 

February 8, 2011, accessed March 1, 2011, at http://www.

xstrata.com/media/news/2011/02/08/0730CET/pdf.
142° E 144° E 146° E 4° S 6° S

8° S

INDONESIA

PAPUA NEW GUINEA

Wasi

Salumei

Bismarck

Frieda River Bismarck Sea

 Coral Sea

130°E 

0°

20°S

AUSTRAL

I

Political boundary source: U.S. Department of State (2009)Projection: Asia South Albers Equal Area Conic;Central meridian 144° E; latitude of origin 15° S

0 50 100 150 200 KILOMETERS

0 50 100 MILES

EX

OtheAsse009pPorpdepotrac

Porpprostrac

Figure P1. Map showing the location, known deposits, and significant prospects and occurrences for permissive tract 009pCu7205, Maramuni A

ID, Indonesia; PG, Papua New Guinea; SB, Solomon Islands.
INDONESIA

( ( ( ( ( ( ( ( ( 

( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( (

(

( ( ( ( ( ( (

(

( ( ( ( ( ( ( ( (

( (

INDONESIA PAPUA NEW GUINEA

Wasi

Salumei

Bismarck

Frieda River Bismarck Sea

 Coral Sea

142° E 144° E 146° E

4° S6° S8° S

Base from ESRI ArcGIS Online (2009)World Shaded ReliefPolitical boundary source: U.S. Department of State (2009)Projection: Asia South Albers Equal Area Conic;Central meridian 146° E; latitude of origin 15° S

0 50 100 150 200 KILOMETERS

0 50 100 MILES

E

Ass 0PerPer

( ( Sut

PorPor

Figure P2. Map showing igneous rocks used to delineate 009pCu7205, Maramuni Arc—Papua New Guinea.
250 Porphyry Copper Assessment of Southeast Asia and Melanesia

1.00

0.90

0.80

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

Probability

0.01 0.1 1 10 100 1k 10k 100k 1M 10M 100M 1B 10B 100B

Material, in metric tons

Mean Cu

Mean Mo

Mean Au

Mean Ag

Mean Rock

Cu

Mo

Au

Ag

Rock

Mean Cu

Mean Mo

Mean Au

Mean Ag

Mean Rock

EXPLANATION

Figure P3. Cumulative frequency plot showing the results of Monte Carlo computer simulation of undiscovered resources in 

tract 009pCu7205, Maramuni Arc—Papua New Guinea. k, thousands; M, millions; B, billions; Tr, trillions.
Appendix Q—Tract 009pCu7206 251

Appendix Q. Porphyry Copper Assessment for Tract 009pCu7206, 

Miocene Alkaline Rocks—Southeastern Papua New Guinea

By Jane M. Hammarstrom1, Dulcie Saroa2, Bambang Tjahjono Setiabudi3, Dwi Nugrono Sunuhadi3, 

Gilpin R. Robinson, Jr.1

, Connie L. Dicken1, Benjamin J. Drenth4, Steve Ludington5, Arthur A. Bookstrom6, 

and Michael L. Zientek6

, with contributions from Gwaibo Kopi2 and Dennis P. Cox5

Deposit Type Assessed: Porphyry copper, copper-gold subtype

Descriptive model: Porphyry copper (Berger and others, 2008; John and others, 2010); Porphyry copper-gold 

(Cox, 1986; Cooke and others, 1998)

Grade and tonnage model: Porphyry copper, copper-gold subtype (Singer and others, 2008)

Table Q1 summarizes selected assessment results.

Table Q1. Summary of selected resource assessment results for tract 009pCu7206, Miocene Alkaline Rocks of Southeastern New 

Guinea Island—Papua New Guinea.

[km, kilometers; km2, square kilometers; t, metric tons; n.d., no data] 

Date of 

assessment

Assessment depth 

(km)

Tract area 

(km2)

Known copper 

resources 

(t)

Mean estimate of

undiscovered copper 

resources (t)

Median estimate of

undiscovered copper

resources (t)

February 2010 1 1,640 n.d. 1,200,000 0

Location

The tract includes the Central and Milne Bay provinces of southeastern Papua New Guinea (fig. Q1).

Geologic Feature Assessed

Miocene alkaline island arc intrusive rocks.

1

U.S. Geological Survey, Reston, Virginia, United States.

2

Mineral Resources Authority, Papua New Guinea.

3

Center for Geological Resources, Geological Agency of Indonesia, West Java, Indonesia.

4

U.S. Geological Survey, Denver, Colorado, United States.

5

U.S. Geological Survey, Menlo Park, California, United States.

6

U.S. Geological Survey, Spokane, Washington, United States.
252 Porphyry Copper Assessment of Southeast Asia and Melanesia

Delineation of the Permissive Tract

Tectonic Setting

The tract outlines four areas of middle Miocene alkaline 

intrusions of probable island-arc affinity in southeastern Papua 

New Guinea. These rocks were described by Smith (1972) as 

a suite of high-potassium (shoshonitic) intrusions that may 

represent small magma chambers intruded into a subvolcanic 

environment at the beginning of a period of Late Cenozoic 

uplift. Smith and Milsom (1984) described two phases of 

extension in eastern Papua: (1) a middle to late Miocene subduction-related phase and (2) a middle Pliocene to Holocene 

phase of calc-alkaline and shoshonitic rocks interpreted as 

reactivation of subduction-modified mantle under the sea-floor 

spreading occurring in the Woodlark Basin (fig. 6).

Geologic Criteria

The tract was created by selecting late Oligocene to middle 

Miocene alkaline intrusive rocks described by Smith (1972) 

from the 1:250,000-scale digital geologic map of Papua New 

Guinea (table Q2, fig. Q2). These rocks intrude Eocene basalt 

(Kutu Volcanics). Basalt and andesite lavas, agglomerate and 

tuff, pillow lava, minor tuffaceous sedimentary rocks, and dikes 

of the Fyfe Bay Volcanics are present in the area of the Magavara prospect (fig. Q1). These volcanic rocks are mapped as 

Pliocene. However, Smith and Milsom (1984) noted that Fyfe 

Bay Volcanics are dated at 12.6 Ma south of Mullins Harbor and 

included them in the discussion of Miocene high-K, shoshonitic 

rocks of the Papuan Peninsula. The late Oligocene to middle 

Miocene Watuti Gabbro is adjacent to the tract but is excluded 

because of its composition (gabbro, pyroxenite). All of the preTable Q2. Map units that define tract 009pCu7206, Miocene Alkaline Rocks of Southeastern New Guinea Island—Papua New Guinea.

[Map unit, age range, and principal lithologies are based on a attributes in a digital compilation of geologic maps of Papua New Guinea Indonesia (Papua New 

Guinea Geological Survey, 2002). Numbers and publication dates of 1:250,000-scale maps available from the Papua New Guinea Geological Survey are listed for 

reference. *, within tract area and part of alkaline complex, but likley too mafic for porphyry association] 

Map unit Map 

symbol Lithology Age range Map 

number

Map 

date

Intrusive rocks

Sige Lele Gabbro Tmb Gabbro Late Oligocene? to middle Miocene C5609 1972

Gabahusuhusu 

Syenite

Tmg, 

Tmgd

Syenite, monzonite, diorite, minor gabbro, dunite Late Oligocene? to middle Miocene C5609 1972

Imudat Monzonite Tmi Monzonite, minor trachyandesite Late Oligocene? to middle Miocene C5512 1970

Magavara Syenite Tmm Syenite, monzonite, minor gabbro; trachybasalt, latite, 

sanidine melanite porphyry dykes

Late Oligocene? to middle Miocene C5512 1970

Ulo Ulo Gabbro Tmo Gabbro, monzonite Late Oligocene? to middle Miocene C5609 1972

Watuti Gabbro* Tmw Gabbro Late Oligocene? to middle Miocene C5609 1972

Volcanic rocks

Fyfe Bay Volcanics Tpf Basaltic and andesitic lava, agglomerate and tuff, some 

pillow lava, minor tuffaceous sedimentary rocks, many 

dykes

Pliocene C5609 1972

Fyfe Bay Volcanics, 

Mount Suat member 

Tpfs Welded basaltic agglomerate Pliocene C5609 1972
Appendix Q—Tract 009pCu7206 253

late Miocene igneous rocks shown on the 1:250,000-scale maps 

in this part of Papua New Guinea are alkaline, associated with 

monzonite, syenite, and gabbro. Smith (1972) reported K-Ar 

ages for some of the rocks in the area as follows:

• Imudat River area monzonite 12.5± 2 Ma 

(biotite)

• Gabahusuhusu River area diorite 11.1± 0.3Ma 

(biotite)

• Gabahusuhusu River area syenite 16.0±0.8 Ma 

(hornblende)

• Magavara River area latite 16.5± 0.2 Ma 

(hornblende)

• Magavara River area porphyry 27.5±3.5 Ma 

(hornblende)

These ages are all Miocene, except for the porphyry age, 

which is Oligocene. The alkaline rocks are separated geographically from the calc-alkaline Miocene Maramuni Arc (tract 

009pCu7205) rocks southeast of Port Moresby by a distance of 

150 km and are older than the late Miocene to Pliocene rocks of 

the Medial New Guinea magmatic belt (tract 009pCu7203). The 

alkaline rocks (gabbro, monzonite, diorite, syenite) form small 

stocks with outcrop areas ranging from less than 4 to 36 km2. 

The tract was constructed in a GIS using a digital compilation 

of 1:250,000-scale geologic maps of Papua New Guinea. Map 

units were classified into generalized units by age and lithologic 

class (igneous volcanic, igneous plutonic). From this digital 

database of geologic lithology and age attributes, Miocene 

alkaline map units in southeasternmost Papua New Guinea were 

selected. Ophiolites, ultramafic rocks, and basaltic units were 

deemed nonpermissive and are omitted from the tract. Using 

GIS tools, tract boundaries were extended out from mapped 

contacts using a 5-km buffer to include possible extensions 

under shallow cover. The final tract boundaries were established 

by GIS processing and editing. The processing approximates 

manual delineation of tracts but is rapid and reproducible. 

Regional and local mineral occurrence, geochemical, and 

isotopic-age data were plotted and used to constrain or expand 

tract boundaries. Tract boundaries were clipped at shorelines 

(U.S. Department of State, 2009).

Known Deposits

None.

Prospects, Mineral Occurrences, and Related 

Deposit Types

The tract covers the areas of the Poi and Magavara 

prospects (table Q3). These prospects are associated with 

the Imudat and Magavara intrusive rocks, respectively. 

Alluvial gold occurrences are associated with all parts of 

the tracts. The Ulo Ulo abandoned gold mine in the Ulo 

Ulo Gabbro is under exploration (drilling) along northwesttrending, high-grade, quartz-limonite gold veins (Vangold 

Resources, Ltd., 2009). The Milne Bay Goldfield in the 

southeasternmost part of the tract produced less than 10,000 

ounces of alluvial gold between 1899 and 1926 (Swiridiuk 

and Lindley, 2004).

Exploration History

The recent boom in gold prices renewed exploration 

interest in areas that were identified previously as anomalous 

in gold based on stream-sediment surveys done in the 1980s 

and on historical alluvial-gold mining. Several current exploration projects focus on such areas associated with the alkaline 

rocks that delineate the permissive tract. Regional geochemical sampling identified a 16 km2

 area of anomalous gold in 

stream sediments (0.12–3.30 g/t gold) at the Poi porphyry 

copper-gold prospect. The area was explored in reconnaissance fashion in 1971, 1984, 1994, and 2007. Ongoing (2009) 

exploration is following up on a geophysical anomaly that 

coincides with a ridge of syenite (Imudat intrusive complex) 

and areas of anomalous gold in stream sediments. Activities 

include mapping, trenching, rock-chip and sediment sampling and geophysical modeling to define drill targets at the 

Poi (Kebei Ridge) prospects (MIL Resources, 2009a,b). The 

Magavara area, which was explored in the 1970s, and again 

starting in 2008, is targeted for high-grade epithermal gold 

and copper-gold porphyry (Sierra Mining Limited, 2008). The 

UloUlo prospect area was explored as part of the 243 km2

Allemata property for mesothermal gold in intrusion-related 

quartz veins and gold-copper skarn in limestone at gabbro 

contacts (Swiridiuk and Lindley, 2004). Surface exploration 

of the Ulo Ulo area for porphyry gold-copper in the 1960s and 

early 1970s included mapping, stream-sediment sampling, and 

detailed grid sampling but proved unsuccessful. Recent (2009) 

trenching and drilling at Allemata identified an east-west trend 

of high-grade gold lodes with up to 1-percent copper (Vangold 

Resources, Ltd., 2009). No porphyry-style mineralization has 

been substantiated to date.

Sources of Information

Principal sources of information used by the assessment 

team are listed in table Q4.

Grade and Tonnage Model Selection

The grade and tonnage model used in this assessment 

was the porphyry copper-gold subtype described by Singer 

and others (2008). The use of this subtype is not based on 

the nature of known deposits within the tract as there are 

none (table 6). The rationale is based on the observation that 

porphyry copper deposits associated with alkaline source rocks 

tend to be enriched in gold (Mutschler and others, 1985, 1991; 

Sillitoe, 2004; Solomon, 1990). Singer and others (2008) do 
254 Porphyry Copper Assessment of Southeast Asia and Melanesia

Table Q3. Significant prospects and occurrences for tract 009pCu7206, Miocene Alkaline Rocks of Southeastern New Guinea 

Island—Papua New Guinea.

[Rank 1=copper occurrence that may be related to porphyry-type mineralization based on stream sediment or magnetic anomaly or location along structural trend.; 

%, percent; g/t, grams per metric ton; km, kilometers, m, meters. Ages based on ages for associated igneous rocks. Ma, million years]

Name Latitude Longitude Age (Ma) Comments Reference Rank

Poi -10.236 149.466 Miocene Undrilled porphyry copper-gold target based on a 1-km strike length 

radiometric and magnetic anomaly associated with the Imudat alkaline 

intrusive complex. Regional rock-chip and stream-sediment sampling in 

1982; trenching on Aladdin skarn prospect (20 m at 0.50% Cu, 7.17 g/t 

Au, 9.6 g/t Ag); drilling planned for 2011. 

MIL 

Resources 

(2009a,b; 

2010)

1

Magavara

-10.537 150.124 OligoceneMioceneCopper and gold identified in 1970s; artisanal gold mining. Reconnaissance exploration 2008 on 627 km2

 area covering the Magavara syenite 

complex identified chalcopyrite and pyrite+arsenopyrite and copper oxide 

minerals in 50-m-wide zone in propylitically altered, sheared, and brecciated syenite and monzonite porphyries; Cu, Au, Ag in grab samples and 

anomalous Au in stream sediments. Likely abandoned by past exploration 

due to lack of inferred tonnage.

Sierra 

Mining 

Limited 

(2008)

1

Table Q4. Principal sources of information used for tract 009pCu7206, Miocene Alkaline Rocks of Southeastern New Guinea Island—

Papua New Guinea.

[NA, not applicable]

Theme Map or title Scale Citation

Geology Digital geologic map of East and 

Southeast Asia

1:2,000,000 CCOP and Geological Survey of Japan (1997)

Geology of Papua New Guinea 1;1,000,000 Bain and others (1972)

Digital geology of Papua New Guinea 1:250,000 Papua New Guinea Geological Survey (2002)

Page size maps in published papers. NA Garwin and others (2005), Hill and others (2002), Quarles van 

Ufford and Cloos (2005), Cloos and others (2005) 

SE Asia Radiometric Ages: GIS Database NA Malaihollo and others (2002)

Mineral 

occurrences

Porphyry copper deposits of the world: 

database, map, and grade and tonnage 

models

NA Singer and others (2008)

Mineral deposits of Papua New Guinea 1:250, 000 Granger (1973)

Mineral Resources Authority of Papua New Guinea (2002)

Exploration Company Web sites NA MIL Resources (2009ba,b; 2010), Sierra Mining Limited (2008), 

Vangold Resources Ltd. (2009)

Papua New Guinea Mineral Resources 

Authority tenement maps

Mineral Resources Authority of Papua New Guinea (2008) 

not specifically classify deposits as alkaline or not, but the 

inclusion of associated rock types within their compilation 

allows the examination of the data for those deposits with 

alkaline rock names. Those data, along with the grade and 

tonnage information from Schroeter and others (1989), seem 

to confirm that whereas not all gold-rich porphyry copper 

deposits are alkaline, nearly all alkaline porphyry copper 

deposits are gold-rich. The association of the prospects in 

the area with alluvial gold, and the gold-rich character of 

porphyry copper mineralization in the region suggest that 

any porphyry copper deposits in the permissive tract will be 

enriched in gold.
Appendix Q—Tract 009pCu7206 255

Estimate of the Number of Undiscovered Deposits

Rationale for the Estimate

The tract delineates four areas of exposed Miocene 

alkaline rocks. Three of the four areas are targets of recent, as 

well as historical exploration, and one area hosts an abandoned 

gold mine. Three areas are spatially associated with artisanal 

alluvial gold mining. None of the areas have been thoroughly 

explored by drilling. Magnetic and radiometric data, as well 

as anomalous gold, copper, and base-metal concentrations in 

stream-sediment and rock-chip geochemical surveys are the 

basis for the current round of exploration activities. At least 

some of the intrusions display alteration characteristics compatible with porphyry copper-style mineralization. Lack of coeval 

volcanic rocks in some parts of the tract area suggests that these 

rocks may be deeply eroded and, therefore, would not preserve 

porphyry copper deposits. However, coeval high-K Fyfe Bay 

volcanic rocks are present in the Magavara prospect area.

The assessment team estimates that there is a 10-percent 

chance for at least one undiscovered porphyry deposit compatible in grade-tonnage characteristics with the porphyry Cu-Au 

model, and a 1-percent chance of three or more deposits. The 

estimate was carried out to five levels to provide three nonzero numbers to constrain the estimate. The high coefficient 

of variation (207 percent) reflects a high degree of uncertainty 

about the tract. Another consideration is that the small area 

of the tract (1,640 km2

) limits the number of discrete deposits 

that could be present. The mean number of deposits is less 

than one (table Q5).

Probabilistic Assessment Simulation 

Results

Undiscovered resources were estimated by combining consensus estimates for numbers of undiscovered porphyry coppergold deposits with the porphyry copper-gold model using the 

EMINERS program (Root and others, 1992; Bawiec and Spanski, 

2012; Duval, 2012). Selected output parameters are reported in 

Table Q6. Results of Monte Carlo simulations of undiscovered resources for tract 009pCu7206, Miocene Alkaline Rocks of Southeastern New Guinea Island—Papua New Guinea.

[Cu, copper; Mo, molybdenum; Au, gold; and Ag, silver; in metric tons; Rock, in million metric tons]

Material Probability of at least the indicated amount Probability of

0.95 0.9 0.5 0.1 0.05 Mean Mean or greater None

Cu 0 0 0 2,000,000 4,700,000 1,200,000 0.14 0.71

Mo 0 0 0 1,500 17,000 7,000 0.07 0.89

Au 0 0 0 170 380 82 0.16 0.71

Ag 0 0 0 330 990 340 0.10 0.86

Rock 0 0 0 430 930 230 0.15 0.71

Table Q5. Undiscovered deposit estimates, deposit numbers, tract area, and deposit density for tract 009pCu7206, Miocene Alkaline 

Rocks of Southeastern New Guinea Island—Papua New Guinea.

[NXX, estimated number of deposits associated with the xxth percentile; Nund, expected number of undiscovered deposits; s, standard deviation; Cv%, coefficient 

of variance; Nknown, number of known deposits in the tract that are included in the grade and tonnage model; Ntotal, total of expected number of deposits plus 

known deposits; km2, area of permissive tract in square kilometers; Ntotal/100k km2, deposit density reported as the total number of deposits per 100,000 km2. 

Nund, s, and Cv% are calculated using a regression equation (Singer and Menzie, 2005)]

Consensus undiscovered deposit 

estimates Summary statistics Tract area 

(km2

)

Deposit density

(Ntotal/100k km2)

N90 N50 N10 N05 N01 Nund s Cv% Nknown Ntotal

0 0 1 1 3 0.36 0.75 210 0 0.36 1,640 22
256 Porphyry Copper Assessment of Southeast Asia and Melanesia

table Q6. Results of the Monte Carlo simulation are presented as a 

cumulative frequency plot (fig. Q3). The cumulative frequency plot 

shows the estimated resource amounts associated with cumulative 

probabilities of occurrence, as well as the mean, for each commodity and for total mineralized rock. The mean amount of copper is 

1.2 Mt; median expected value is none.

References Cited

Bain, J.H.C., Davies, H.L., Hohnen, P.D., Ryburn, R.J., Smith, 

I.E., Grainger, R., Tingey, R.J. and Moffar, M.R., compilers, 

1972, Geology of Papua New Guinea, Canberra: Bureau 

of Mineral Resources, Geology and Geophysics, 4 sheets, 

scale 1:1,000,000.

Bawiec, W.J., and Spanski, G.T., 2012, Quick-start guide for 

version 3.0 of EMINERS—Economic Mineral Resource 

Simulator: U.S. Geological Survey Open-File Report 

2009–1057, 26 p., accessed June 30, 2012, at http://pubs.

usgs.gov/of/2009/1057. (This report supplements USGS 

OFR 2004–1344.)

Berger, B.R., Ayuso, R.A., Wynn, J.C., and Seal, R.R., 

2008, Preliminary model of porphyry copper deposits: 

U.S. Geological Survey Open-File Report 2008–1321, 

55 p., accessed May 15, 2009, at http://pubs.usgs.gov/

of/2008/1321.

Cloos, Mark, Sapiie, B., Quarles van Ufford, A., Weiland, 

R.J., Warren, P.Q., and McMahon, T.P., 2005, Collisional 

delamination in New Guinea—The geotectonics of subducting slab breakoff: Geological Society of America Special 

Paper 400, 51 p.

Cooke, D.R., Heithersay, P.S., Wolfe, R., and Calderon, A.L., 

1998, Australian and western Pacific porphyry Cu-Au 

deposits: Journal of Australian Geology and Geophysics, 

v. 17, no. 4, p. 97–104.

Coordinating Committee for Coastal and Offshore Geoscience Programmes in East and Southeast Asia (CCOP) 

and Geological Survey of Japan, 1997, Digital geologic 

map of East and Southeast Asia: Geological Survey of 

Japan, Digital Geoscience Map G-2 scale 1:2,000,000, 

CD-ROM.

Cox, D.P., 1986, Descriptive model of porphyry Cu-Au, in

Cox, D.P., and Singer, D.A., eds., Mineral deposit models: 

U.S. Geological Survey Bulletin 1693, p. 110.

Cox, D.P., Williamson, A., Rogerson, R., and Finlayson, E.J., 

1986, Mineral deposit models applicable to Papua New 

Guinea: Geological Survey of Papua New Guinea, Report 

86/5. 

Duval, J.S., 2012, Version 3.0 of EMINERS—Economic Mineral Resource Simulator: U.S. Geological Survey Open-File 

Report 2004–1344, accessed July 5, 2012, at http://pubs.

usgs.gov/of/2004/1344.

Garwin, S., Hall, R., and Watanabe, Y., 2005, Tectonic setting, 

geology, and gold and copper mineralization in Cenozoic 

magmatic arcs of southeast Asia and the west Pacific, in 

Hedenquist, T.W., Thompson, J.F.H., Goldfarb, R.J., and 

Richards, J.P., eds., One hundredth anniversary volume 

1905–2005: Littleton, Colorado, Society of Economic 

Geologists, p. 891–930.

Granger, D.J., compiler, 1973, Mineral deposits of Papua New 

Guinea: Canberra, Bureau of Mineral Resources, Geology 

and Geophysics, 1 sheet, scale 1:2,500,000.

Hill, K.C., Kendrick, R.D., Crowhurst, P.V., and Gow, P.A., 

2002, Copper-gold mineralisation in New Guinea—Tectonics, lineaments, thermochronology and structure, in 

Korsch, R.J., ed., Geodynamics of Australia and its mineral 

systems—Technologies, syntheses and regional studies: 

Melbourne, Australia, Blackwell Scientific Publications for 

the Geological Society of Australia, p. 737–752.

John, D.A., Ayuso, R.A., Barton, M.D., Blakely, R.J., Bodnar, 

R.J., Dilles, J.H., Gray, Floyd, Graybeal, F.T., Mars, J.C., 

McPhee, D.K., Seal, R.R., Taylor, R.D., and Vikre, P.G., 

2010, Porphyry copper deposit model, chap. B of Mineral 

deposit models for resource assessment: U.S. Geological 

Survey Scientific Investigations Report 2010–5070–B, 

169 p., accessed September 8, 2010, at http://pubs.usgs.gov/

sir/2010/5070/b/.

MIL Resources, 2009a, MIL Resources finds gold nugget at 

Poi in PNG: accessed February 10, 2010, at http://www.

proactiveinvestors.com.au/companies/news/1687.

MIL Resources, 2009b, High grade gold assays extends 

anomaly and defined two new gold zones at Poi, PNG: MIL 

Resource ASX Announcement- Media Release, September 

10, 2009.

MIL Resources, 2010, Trenching at Poi extends zone to 20 m 

@7.17 g/t Au, 0.50% Cu and 9.60 g/t Ag: MIL Resource 

ASX Announcement- Media Release, November 26, 2010.

Milsom, John, and Smith, I.E., 1975, Southeastern Papua—

Generation of thick crust in a tensional environment: Geology, v. 3, no. 3, p. 117–120.

Mineral Resources Authority of Papua New Guinea, 2002, 

Digital coverage of Papua New Guinea—Digital coverage 

of PNG mainland and New Guinea Islands, produced by 

Australian Geoscience for PNG Geological Survey in July 

01, 2002 (with explanatory notes), scale 1:250,000.

Mineral Resources Authority of Papua New Guinea, 2008, 

Papua New Guinea mines and potential projects map 

updated to 2008: accessed January 15, 2010, at http://www.

mra.gov.pg/Portals/0/Mining%20Infor/projects%20map.pdf.
Appendix Q—Tract 009pCu7206 257

Mutschler, F.E., Griffen, M.E., Stevens, D.S., and Shannon, 

S.S., Jr., 1985, Precious metal deposits related to alkaline 

rocks in the North American Cordillera; an interpretive 

review: Transactions of the Geological Society of South 

Africa, v. 88, p. 355–377.

Mutschler, F.E., Mooney, T.C., and Johnson, D.C., 1991, Precious metal deposits related to alkaline igneous rocks—A 

space-time trip through the Cordillera: Mining Engineering, 

v. 43, no. 3, p. 304–309.

Mutschler, F.E., and Mooney, T.C., 1995, Precious metal 

deposits related to alkaline igneous rocks—Provisional 

classification, grade-tonnage data, and exploration frontiers: 

Geological Association of Canada Special Paper—IAGOD 

1990 Symposium on ore deposit models, 22 p.

Müller, D., 2002, Gold-copper mineralization in alkaline 

rocks: Mineralium Deposita, v. 37, p. 1–3.

Papua New Guinea Geological Survey, 2002, Digital 

geological map of Papua New Guinea: Australia, Australian 

Geosciences, scale 1:250,000.

Quarles van Ufford, Andrew, and Cloos, Mark, 2005, 

Cenozoic tectonics of New Guinea: Bulletin of the 

American Association of Petroleum Geologists, v. 89, no. 1, 

p. 119–140.

Rogerson, R., and McKee, C., 1990, Geology, volcanism and 

mineral deposits of Papua New Guinea: Australian Institute 

of Mining and Metallurgy, Monograph 14, p. 1689–1701.

Root, D.H., Menzie, W.D., and Scott, W.A., 1992, Computer 

Monte Carlo simulation in quantitative resource estimation: 

Natural Resources Research, v. 1, no. 2, p. 125–138.

Schroeter, T.G., Lund, C., and Carter, G., 1989, Gold 

production and reserves in British Columbia: British 

Columbia Geological Survey Open-file report 1989–22, 

86 p.

Sierra Mining Limited, 2008, Magavara project: Sierra 

Mining Limited Web site, accessed June 15, 2010, at http://

sierramining.com.au/?id=321.

Sillitoe, R.H., 2002, Some metallogenic features of gold and 

copper deposits related to alkaline rocks and consequences 

for exploration: Mineralium Deposita, v. 37, p. 4–13.

Singer, D.A., and Menzie, W.D., 2005, Statistical guides to 

estimating the number of undiscovered mineral deposits—

An example with porphyry copper deposits, in Cheng, 

Qiuming, and Bonham-Carter, Graeme, eds., Proceedings 

of IAMG—The annual conference of the International 

Association for Mathematical Geology: Toronto, Canada, 

York University, Geomatics Research Laboratory, 

p. 1028–1033.

Singer, D.A., Berger, V.I., and Moring, B.C., 2008, Porphyry 

copper deposits of the world—Database and grade and 

tonnage models, 2008: U.S. Geological Survey Open-File 

Report 2008–1155, accessed June 1, 2011, at http://pubs.

usgs.gov/of/2008/1155/.

Singer, D.A., Berger, V.I., Menzie, W.D., and Berger, B.R., 

2005, Porphyry copper density: Economic Geology, v. 100, 

no. 3, p. 491–514.

Smith, I.E., 1972, High-potassium intrusives from 

southeastern Papua: Contributions to Mineralogy and 

Petrology, v. 34, p. 167–176.

Smith, I.E., and Milsom, J.S., 1984, Late Cenozoic volcanism 

and extension in Eastern Papua: Geological Society of 

London, Special Publication, v. 16, p. 163–171.

Solomon, M., 1990, Subduction, arc reversal, and the origin 

of porphyry copper-gold deposits in island arcs: Geology, 

v. 18, p. 630–633.

Swiridiuk, Peter, and Lindley, I.D., 2004, Technical report on 

the Allemata property, Milne Bay Province, Papua New 

Guinea, prepared for New Guinea Gold Corporation and 

Vangold Resources, Ltd.: accessed September 10, 2010, at 

http://www.newguineagold.ca/projects/allemata/reports/

AllemataTechnical0805.pdf.

U.S. Department of State, 2009, Small-scale digital 

international land boundaries (SSIB)–Lines, edition 10, and 

polygons, beta edition 1, in Boundaries and sovereignty 

encyclopedia (B.A.S.E.): U.S. Department of State, Office 

of the Geographer and Global Issues.

Vangold Resources, Ltd., 2009, New release November 

19, 2009: accessed February 10, 2010, at http://www.

theaureport.com/cs/user/download/co_file/1490/

Vangold_11-4_C6FC80DEd01-1.pdf.
150° E 10° S Poi Magavara PAPUA NEW GUINEA

Coral Sea

Goodenough Bay

Milne Bay

140°E 

0°

10°S20°S

AUSTR

PGID 

Political boundary source: U.S. Department of State (2009)Projection: Asia South Albers Equal Area Conic;Central meridian 150° E; latitude of origin 15° S

0 10 20 30 40 KILOMETERS

0 10 20 MILES

E

OthAss009p

Por

A

M

Figure Q1. Map showing the location, known deposits, and significant prospects and occurrences for permissive tract 009pCu7206, Miocene Alk

eastern New Guinea Island—Papua New Guinea. ID, Indonesia; PG, Papua New Guinea; SB, Solomon Islands.
Poi

Magavara

Coral Sea

Goodenough Bay

Milne Bay

PAPUA NEW GUINEA

149.5° E 150° E 150.5° E

10° S

10.5° S

Base from ESRI ArcGIS Online (2009)World Shaded ReliefPolitical boundary source: U.S. Department of State (2009)Projection: Asia South Albers Equal Area Conic;Central meridian 150° E; latitude of origin 15° S

0 10 20 30 40 KILOMETERS

0 10 20 MILES

As PePePo

Figure Q2. Map showing igneous rocks used to delineate tract 009pCu7206, Miocene Alkaline Rocks of Southeastern New Guinea Island—Papu
260 Porphyry Copper Assessment of Southeast Asia and Melanesia

1.00

0.90

0.80

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

Probability

0.01 0.1 1 10 100 1k 10k 100k 1M 10M 100M 1B 10B 100B

Material, in metric tons

Cu

Mo

Au

Ag

Rock

Mean Cu

Mean Mo

Mean Au

Mean Ag

Mean Rock

EXPLANATION

Mean Cu

Mean Mo

Mean Au

Mean Ag

Mean Rock

Figure Q3. Cumulative frequency plot showing the results of Monte Carlo computer simulation of undiscovered 

resources in 009pCu7206, Miocene Alkaline Rocks of Southeastern New Guinea Island—Papua New Guinea. k, thousands; M, millions; B, billions; Tr, trillions.
Appendix R—Tract 142pCu7208 261

Appendix R. Porphyry Copper Assessment for Tract 142pCu7208, 

Inner Melanesian Arc Terranes I—Indonesia

By Jane M. Hammarstrom1, Bambang Tjahjono Setiabudi2, Dwi Nugrono Sunuhadi2, Gilpin R. Robinson, Jr.1, 

Connie L. Dicken1

, Steve Ludington3, Arthur A. Bookstrom4, and Michael L. Zientek4, with contributions from 

Dennis P. Cox3

Deposit Type Assessed: Porphyry copper

Descriptive model: Porphyry copper (Berger and others, 2008; John and others, 2010)

 

A permissive tract is delineated based on permissive rock types depicted on 1:250,000-scale geologic maps. Insufficient information was available to the assessment team members for them to complete a probabilistic assessment of the tract area. Summary information is listed in table R1.

Table R1. Summary information for tract 142pCu7208, Inner Melanesian Arc Terranes I—Papua and West Papua, Indonesia (fig. R1). 

[km, kilometers; km2, square kilometers; t, metric tons; n.d., no data] 

Date of assessment Assessment depth (km) Tract area (km2) Known copper resources (t)

February 2010 1 10,130 n.d.

Location

The tract includes the northern margin of the island of New Guinea in Papua and West Papua provinces, Indonesia.

Geologic Feature Assessed

Eocene-Oligocene to early Miocene accreted Inner Melanesian magmatic arc terranes of western New Guinea Island.

Delineation of the Permissive Tract

Tectonic Setting

The Inner Melanesian tract outlines parts of the Inner Melanesian Arc, a 1,000–km-long calc-alkaline arc that developed in the 

Eocene to early Oligocene from southwestward subduction of the Pacific Plate. The tract is delineated on the extent of permissive Paleo1

U.S. Geological Survey, Reston, Virginia, United States.

2

Center for Geological Resources, Geological Agency of Indonesia, West Java, Indonesia.

3

U.S. Geological Survey, Menlo Park, California, United States.

4

U.S. Geological Survey, Spokane, Washington, United States.
262 Porphyry Copper Assessment of Southeast Asia and Melanesia

gene to early Miocene igneous rocks shown on 1:250,000-scale 

geologic maps along the northern margins of the island of New 

Guinea in the Indonesian provinces of Papua and West Papua. 

The tract segments represent arcs of uncertain origin accreted 

to the northern edge of Australian continental crust (fig. 4). The 

accreted terranes are not well-understood; however, they all 

include Paleogene volcanic rocks and may represent remnants 

of the Philippine Sea Plate that were fragmented by strikeslip faulting since 25 Ma (Ali and Hall, 1995; Hall, 2001). 

Accreted terranes in Papua New Guinea are described as tract 

009pCu7208.

The tract corresponds with the Melanesian Arc terrane as 

defined by Cloos and others (2005). The tract area in Indonesia 

correlates with the region along the coast of the Bird’s Head 

referred to as the Coastal Irian Jaya Arc (age unknown, inferred 

Neogene) by Carlile and Mitchell (1994).

These rocks are age-equivalent to accreted terranes 

in the Adelbert-Finisterre area of Papua New Guinea (tract 

009pCu7208) and to rocks that host porphyry copper deposits 

on New Britain Island (tract 009pCu7205) but are more poorly 

characterized and less explored, and therefore, they were delineated as a separate tract.

Geologic Criteria

The tract was constructed in a GIS using 1:250,000-

scale geologic maps of Indonesia, a 1:500,000-scale digital 

map of igneous rocks of Indonesia (Directorate of Mineral 

Resources and Inventory, 2004a), and a 1:1,000,000-scale 

geologic map of Irian Jaya (Dow and others, 1986). Map 

units were classified into generalized units by age and lithologic class (igneous volcanic, igneous plutonic). From this 

digital database of geologic lithology and age attributes, all 

igneous rocks of Miocene age (>7 Ma) and rocks mapped as 

Eocene to early Miocene were selected (fig. R2). Ophiolites, 

ultramafic rocks, and basaltic units were deemed nonpermissive and are omitted from the tract. Map units included in the 

tract are listed in table R2.

The final tract boundaries were established by GIS 

processing and editing. The processing steps included (1) 

buffering permissive map units with a 5-km concentric buffer; 

(2) unioning buffered permissive map units and other polygon 

features that comprise the framework of the tract; (3) aggregating unioned polygons using an aggregation distance of 15 km 

and a minimum hole size of 1,000 km2

, a step done to group 

closely spaced permissive areas; (4) manually aggregating and 

adjusting tract areas; and (5) smoothing polygons. Preliminary 

tracts were cleaned to remove necking and thinning introduced 

by processing; tracts were compared with source maps to 

ensure that original permissive boundaries and buffer distances were honored. Regional and local mineral-occurrence, 

geochemical, and isotopic-age data were plotted and used to 

constrain or expand tract boundaries; in particular, a database 

of isotopic ages of igneous rocks for Indonesia compiled 

by the Southeast Asia Research Group provided additional 

controls on distributions of permissive rocks (Malaihollo and 

others, 2002). Tract boundaries were clipped at shorelines 

(U.S. Department of State, 2009).

Known Deposits

None.

Prospects, Mineral Occurrences, and Related 

Deposit Types

None.

Exploration History

No information.

Sources of Information

Principal sources of information used by the assessment 

team are listed in table R3.

Table R2. Map units that define tract 142pCu7208, Inner Melanesian Arc Terranes I—Papua and West Papua, Indonesia.

[Map unit, age range, and principal lithologies are based on a attributes in a digital compilation of igneous rocks of Southeast Asia (Directorate of Mineral 

Resources and Inventory, 2004a) and 1:250,000-scale geologic quadrangle maps for Indonesia (Geological Research and Development Centre, 1987–2000). 

Ma, million years]

Map unit Map symbol Lithology Age range

Lembia Diorite Tmle Diorite Miocene (15.8 Ma hornblende age)

Auwewa Formation Tema, Teoa Island arc volcanics, subvolcanic diorite 

and microdiorite intrusions

Eocene to early Miocene (radiometric ages 10.6

Batanta Volcanics Temb Basaltic to andesitic lavas; small diorite 

bodies, gabbro

Eocene to early Miocene

Volcanic Rock member 

of Rumai Fm

Temv Basalt to andesite Eocene to early Miocene

Yapen Volcanics Temya Breccia, tuff, basalt-andesite, comagmatic 

microdiorite and andesite porphyry dikes

Eocene to early Miocene
Appendix R—Tract 142pCu7208 263

Qualitative Assessment

Permissive tract 142pCu7208 was delineated to recognize 

that Eocene-Oligocene to Miocene permissive igneous rocks 

for porphyry copper deposits are present in the accreted terranes along northern New Guinea Island and offshore islands. 

The presence of coeval volcanic and plutonic rocks suggest that 

at least in some areas, the erosion levels may be appropriate for 

preservation of deposits. However, the team members had too 

little information available to them to make resource estimates. 

More information about the exploration history, ages, and 

lithologies of permissive igneous rocks would be helpful to 

assess the porphyry potential of the tract area.

 References Cited

Ali, J.R., and Hall, Robert, 1995, Evolution of the boundary 

between the Philippine Sea Plate and Australia—Paleomagnetic evidence from eastern Indonesia: Tectonophysics 

v. 251, p. 251–275.

Berger, B.R., Ayuso, R.A., Wynn, J.C., and Seal, R.R., 

2008, Preliminary model of porphyry copper deposits: 

U.S. Geological Survey Open-File Report 2008–1321, 

55 p., accessed May 15, 2009, at http://pubs.usgs.gov/

of/2008/1321.

Table R3. Principal sources of information used for tract 142pCu7208, Inner Melanesian Arc Terranes I—Papua and West Papua, Indonesia.

[NA, not applicable]

Theme Map or title Scale Citation

Geology Digital geologic map of East and Southeast 

Asia

1:2,000,000 CCOP and Geological Survey of Japan (1997)

Geologic map of Irian Jaya 1:1,000,000 Dow and others (1986)

Geologic quadrangle maps 1:250,000 Directorate of Mineral Resources and Inventory (2004a)

Page size maps in published papers. NA Garwin and others (2005), Hill and others (2002), Quarles 

van Ufford and Cloos (2005), and Cloos and others (2005) 

SE Asia Radiometric Ages: GIS Database NA Malaihollo and others (2002)

Mineral

occurrences

Porphyry copper deposits of the world: database, map, and grade and tonnage modelsNA Singer and others (2008)

Digital mineral occurrence database for 

Indonesia

NA Directorate of Mineral Resources and Inventory (2004b)

Carlile, J.C., and Mitchell, A.H.C., 1994, Magmatic arcs and 

associated gold and copper mineralization in Indonesia: 

Journal of Geochemical Exploration, v. 50, p. 91–142.

Cloos, Mark, Sapiie, B., Quarles van Ufford, A., Weiland, 

R.J., Warren, P.Q., and McMahon, T.P., 2005, Collisional 

delamination in New Guinea—The geotectonics of subducting slab breakoff: Geological Society of America Special 

Paper 400, 51 p.

Coordinating Committee for Coastal and Offshore Geoscience 

Programmes in East and Southeast Asia (CCOP) and Geological Survey of Japan, 1997, Digital geologic map of East 

and Southeast Asia: Geological Survey of Japan, Digital 

Geoscience Map G-2 scale 1:2,000,000, CD-ROM.

Directorate of Mineral Resources and Inventory, 2004a, 

Digital geologic map: Jakarta, Indonesia, Indonesian 

Ministry of Energy and Mineral Resources, scale 

1:1,000,000. [Proprietary data.]

Directorate of Mineral Resources and Inventory, 2004b, 

Digital mineral occurrence database: Jakarta, Indonesia, 

Indonesian Ministry of Energy and Mineral Resources. 

[Proprietary data.]

Dow, D.B., Robinson, G.P., Hartono, U., and Ratman, N., 

1986, Geologic map of Irian Jaya, Indonesia: Bandung, 

Geological Research and Development Centre, 1 map on 

2 sheets, scale 1:1,000,000. [In English and Indonesian.]
264 Porphyry Copper Assessment of Southeast Asia and Melanesia

Garwin, S., Hall, R., and Watanabe, Y., 2005, Tectonic setting, 

geology, and gold and copper mineralization in Cenozoic 

magmatic arcs of southeast Asia and the west Pacific, in

Hedenquist, T.W., Thompson, J.F.H., Goldfarb, R.J., and Richards, 

J.P., eds., One hundredth anniversary volume 1905–2005: 

Littleton, Colorado, Society of Economic Geologists, p. 891–930.

Geological Research and Development Centre, 1987–2000, 

Systematic geologic map, Indonesia, scale 1:250,000: 

Bandung, Geological Survey of Indonesia, Indonesia.

Hall, R., 2001, Extension during late Neogene collision in 

east Indonesia and New Guinea, in Aillères, Laurent, and 

Rawling, Tim, eds., Animations in geology: Journal of the 

Virtual Explorer, Electronic Edition, ISSN 1441–8142, v. 4, 

paper 4, doi:10.3809/jvirtex.2001.00031.

Hill, K.C., Kendrick, R.D., Crowhurst, P.V., and Gow, P.A., 

2002, Copper-gold mineralisation in New Guinea—

Tectonics, lineaments, thermochronology and structure, in 

Korsch, R.J., ed., Geodynamics of Australia and its mineral 

systems—Technologies, syntheses and regional studies: 

Melbourne, Australia, Blackwell Scientific Publications for 

the Geological Society of Australia, p. 737–752.

John, D.A., Ayuso, R.A., Barton, M.D., Blakely, R.J., Bodnar, 

R.J., Dilles, J.H., Gray, Floyd, Graybeal, F.T., Mars, J.C., 

McPhee, D.K., Seal, R.R., Taylor, R.D., and Vikre, P.G., 2010, 

Porphyry copper deposit model, chap. B of Mineral deposit 

models for resource assessment: U.S. Geological Survey 

Scientific Investigations Report 2010–5070–B, 169 p., accessed 

September 8, 2010, at http://pubs.usgs.gov/sir/2010/5070/b/.

McPhee, D.K., Seal, R.R., Taylor, R.D., and Vikre, P.G., 

2010, Porphyry copper deposit model, chap. B of Mineral 

deposit models for resource assessment: U.S. Geological 

Survey Scientific Investigations Report 2010–5070–B, 

169 p., accessed September 8, 2010, at http://pubs.usgs.

gov/sir/2010/5070/b/.

Malaihollo, J.F.A., Hall, R., and Macpherson, C.G., 2002, 

SE Asia radiometric ages—GIS database: accessed 

January 15, 2010, at http://searg.rhul.ac.uk/current_

research/isotopic_ages/SEAsia_GIS.pdf.

Quarles van Ufford, Andrew, and Cloos, Mark, 2005, 

Cenozoic tectonics of New Guinea: Bulletin of the 

American Association of Petroleum Geologists, v. 89, 

no. 1, p. 119–140.

Singer, D.A., Berger, V.I., and Moring, B.C., 2008, 

Porphyry copper deposits of the world—Database and 

grade and tonnage models, 2008: U.S. Geological Survey 

Open-File Report 2008–1155, accessed June 1, 2011, at 

http://pubs.usgs.gov/of/2008/1155/.

U.S. Department of State, 2009, Small-scale digital 

international land boundaries (SSIB)—Lines, edition 

10, and polygons, beta edition 1, in Boundaries 

and sovereignty encyclopedia (B.A.S.E.): U.S. 

Department of State, Office of the Geographer and 

Global Issues.
130° E 135° E 

0°

INDONESIA 

 PACIFIC OCEAN Ceram Sea

130°E 

10°N

10°S

ID

AU

MY

PH

PACI

INDIAN OCEAN

Banda Sea

Political boundary source: U.S. Department of State (2009)Projection: Asia South Albers Equal Area Conic;Central meridian 135° E; latitude of origin 15° S

0 50 100 150 200 KILOMETERS

0 50 100 MILES EXPLANATION

Other porphyry copper tractsAssessed porphyry copper tract 142pCu7208

Porphyry copper prospects associated with other tracts

A

Figure R1. Map showing the location of permissive tract 142pCu7208, Inner Melanesian Arc Terranes I—Papua and West Papua, Indonesia. AU

sia; PG, Papua New Guinea; PH, Philippines; MY, Malaysia.
266 Porphyry Copper Assessment of Southeast Asia and Melanesia

Figure R2. Map showing igneous rocks used to delineate tract 142pCu7208, Inner Melanesian Arc Terranes I—

Papua and West Papua, Indonesia.

( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( 

( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( 

Ceram Sea

Halnahera Sea

130° E 135° E 

0°

Base from ESRI ArcGIS Online (2009)

World Shaded Relief

Political boundary source: U.S. Department of State (2009)

Projection: Asia South Albers Equal Area Conic;

Central meridian 135° E; latitude of origin 15° S

0 50 100 150 200 KILOMETERS

0 50 100 MILES
Appendix R—Tract 142pCu7208 267

(

( (

( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( 

( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( (

( ( ( ( ( ( ( (

!

INDONESIA

Jayapura

PACIFIC OCEAN

140° E

EXPLANATION

Permissive intrusive rock

Permissive volcanic rock

( ( Subduction and suture zone

Spreading center

Strike-slip fault

Assessed porphyry copper tract

 142pCu7208
268 Porphyry Copper Assessment of Southeast Asia and Melanesia 

Appendix S. Porphyry Copper Assessment for Tract 009pCu7208, 

Inner Melanesian Arc Terranes II—Northern New Guinea 

Island, Papua New Guinea

By Jane M. Hammarstrom1, Dulcie Saroa2, Bambang Tjahjono Setiabudi3, Dwi Nugrono Sunuhadi3, Gilpin R. 

Robinson, Jr.1

, Connie L. Dicken1, Steve Ludington4, Arthur A. Bookstrom5, and Michael L. Zientek5, with contributions from Gwaibo Kopi2 and Dennis P. Cox4

Deposit Type Assessed: Porphyry copper

Descriptive model: Porphyry copper (Berger and others, 2008; John and others, 2010)

A permissive tract is delineated based on permissive rock types depicted on 1:250,000-scale geologic maps. Insufficient 

information was available to the assessment team members for them to complete a probabilistic assessment of the tract area. 

Summary information is listed in table S1.

Location

The tract includes the northern margin of the island of New Guinea, Papua New Guinea (fig. S1).

Geologic Feature Assessed

Eocene-Oligocene to early Miocene accreted Inner Melanesian magmatic arc terranes of New Guinea Island.

1

U.S. Geological Survey, Reston, Virginia, United States.

2

Mineral Resources Authority, Papua New Guinea.

3

Center for Geological Resources, Geological Agency of Indonesia, West Java, Indonesia.

4

U.S. Geological Survey, Menlo Park, California, United States.

5

U.S. Geological Survey, Spokane, Washington, United States.

Table S1. Summary of selected resourceassesment results for tract 009pCu7208, Inner Melanesian Arc Terranes II—Northern New 

Guinea Island, Papua New Guinea.

[km, kilometers; km2, square kilometers; t, metric tons; n.d., no data] 

Date of assessment Assessment depth 

(km)

Tract area 

(km2)

Known copper resources 

(t)

February 2010 1 29,140 n.d.
Appendix S—Tract 009pCu7208 269

Delineation of the Permissive Tract

Tectonic Setting

The Inner Melanesian Arc tract outlines parts of the 

Inner Melanesian Arc, a 1,000-km-long calc-alkaline arc that 

developed in the Eocene to early Oligocene from southwestward subduction of the Pacific Plate. The tract segments 

represent accreted Paleogene arcs preserved in the BewaniTorricelli Mountains, Adelbert, and Finisterre Ranges (fig. 7). 

The accreted terranes are not well-understood; however, 

they all include Paleogene volcanic rocks and may represent 

remnants of the Philippine Sea Plate that were fragmented by 

strike-slip faulting since 25 Ma (Ali and Hall, 1995).

The tract corresponds with the Melanesian Arc terrane as 

defined by Cloos and others (2005). The region of northeastern New Guinea north of the Ramu-Markham Fault and New 

Britain Island are considered to be part of a single volcanic 

arc (Bain, 1973). No porphyry copper deposits have been 

reported on the New Guinea island-arc segment (Singer and 

others, 2008; Titley and Heidrick, 1978) although the rocks 

are age-equivalent to tract 009pCu7209 on New Britain Island. 

The fragmented, accreted arc segments on New Guinea Island 

are more poorly characterized and less well-explored, and 

therefore, they were delineated as a separate tract.

Geologic Criteria

The tract is delineated on the extent of permissive Paleogene to early Miocene igneous rocks shown on 1:250,000-scale 

geologic maps along the northern margins of the island of New 

Guinea in Papua New Guinea (fig. S2, table S2). The westernmost 

tract segments primarily are based on exposures of about subequal 

amounts of intrusions and volcanic rocks (fig. S2). The eastern 

tract segments include accreted parts of the Finisterre-Adelbert Arc 

along the northern margin of Papua New Guinea, where the tract 

is based primarily on the distribution of the Oligocene to early 

Miocene Finisterre Volcanics, which were described as a thick 

(perhaps as much as 4,500 m) sequence of Oligocene to early 

Miocene island-arc rocks dominated by volcaniclastic potassic 

basalt and low-silica andesites that fall into two groups: shoshonite 

and high-K, high-Al basalt (Jaques, 1976).

The tract was constructed in a GIS. Map units were classified into generalized units by age and lithologic class (igneous volcanic, igneous plutonic). From this digital database 

of geologic lithology and age attributes, all igneous rocks of 

Eocene to early Miocene were selected. Ophiolites, ultramafic 

rocks, and basaltic units were deemed nonpermissive and are 

omitted from the tract. Map units included in the tract are 

listed in table S2.

The final tract boundaries were established by a GIS 

processing and editing. The processing steps included (1) 

buffering permissive map units with a 5-km concentric buffer; 

(2) unioning buffered permissive map units and other polygon 

features that comprise the framework of the tract; (3) aggregating unioned polygons using an aggregation distance of 15 km 

and a minimum hole size of 1,000 km2

, a step done to group 

closely spaced permissive areas; (4) manually aggregating and 

adjusting tract areas; and (5) smoothing polygons. Preliminary 

tracts were cleaned to remove necking and thinning introduced 

by processing; tracts were compared with source maps to 

ensure that original permissive boundaries and buffer distances were honored. Regional and local mineral-occurrence, 

geochemical, and isotopic-age data were plotted and used to 

constrain or expand tract boundaries; in particular, a database 

of isotopic ages of igneous rocks for Indonesia compiled 

by the Southeast Asia Research Group provided additional 

controls on distributions of permissive rocks (Malaihollo and 

others, 2002). Tract boundaries were clipped at shorelines 

(U.S. Department of State, 2009).

Known Deposits

None.

Prospects, Mineral Occurrences, and Related 

Deposit Types

Alluvial gold workings are present in the eastern parts 

of the Toricelli Intrusive Complex in northern Papua New 

Guinea. Map unit Tlv (table S2) includes skarn.

Exploration History

Parts of the tracts, especially the westernmost tract segment in the Toricelli Mountains, overlap exploration tenement 

areas. The assessment team is unaware of any porphyry copper 

exploration targets within the tract area.

Sources of Information

Principal sources of information used by the assessment 

team are listed in table S3.

Qualitative Assessment

Permissive tract 009pCu7208 was delineated to recognize that Paleogene to early Miocene igneous rocks that are 

permissive for the occurrence of porphyry copper deposits 

occur in northern New Guinea Island, Papua New Guinea. The 

presence of coeval volcanic and plutonic rocks suggest that, at 

least in some areas, the erosion levels may be appropriate for 

preservation of deposits. However, the team members had too 

little information available to make resource estimates. The 

Finisterre Volcanics may be too thick to preserve any associated porphyry systems; they were included based on similarities to coeval rocks on New Britain within the same arc to the 

east, where porphyry copper deposits are known.
270 Porphyry Copper Assessment of Southeast Asia and Melanesia 

Table S2. Map units that define tract 009pCu7208, Inner Melanesian Arc Terranes II—Northern New Guinea Island, Papua New 

Guinea. 

[Map unit, age range, and principal lithologies are based on a attributes in a digital compilation of geologic maps of Papua New Guinea (Papua New Guinea Geological Survey, 2002). --, no map unit] 

Map unit Map 

symbol Lithology Age range

Intrusive rocks 

Kui Tonalite Tek, Tet, 

KITet

Tonalite (quartz diorite): quartz-oligoclase/andesine-hornblende rock Late Paleocene to Eocene

Prince Alexander 

Complex

KTp Crushed and mylonitized granodiorite, diorite, dolerite, amphibolite; 

orthogneiss; some schist, adamellite, porphyry dykes

Early Cretaceous to earliest Miocene 

(Some middle Jurassic

Torricelli 

Intrusive 

Complex

KTt Medium-grained gabbro, dolerite, diorite, monzonite; some granodiorite, 

adamellite; minor pegmatitic and porphyritic equivalents, serpentinite; 

commonly sheared

Late Cretaceous to earliest Miocene

Imo Tonalite Tei Tonalite; some granophyric diorite Eocene

Volcanic rocks 

Bliri Volcanics Tb Basic, intermediate and minor acid volcanics and volcanically derived 

sediments; dolerite; minor limestone lenses; commonly sheared and altered

Paleocene? to earliest Miocene

Eia Beds Tee Andesitic and dacitic glassy tuff, breccia, lava, minor calcilutite, planktonic 

foraminifera

Eocene

 -- Tl Andesitic and dacitic porphyries, some granodiorite, gabbro Early Eocene to Late Oligocene?

Okiduse 

Volcanics

Tlo Andesite and basaltic andesite flows and tuffs, typically porphyritic; 

andesitic agglomerate; intrusive breccia

Early Tertiary

Lower Volcanics Tlv Basalt and basaltic andesite flows and tuffs, typically fine grained; pillow 

lavas, agglomerate, volcanic conglomerate, medium-grained mafic 

intrusions; shale, chert, limestone; monzonite porphyry intrusions; garnet 

and magnetite skarns

Early Tertiary

Finisterre 

Volcanics

Tof Basalt and andesite flow breccia, indurated tuffaceous lithic greywacke, 

lithic and crystal tuff, paraconglomerate, peperite and peperitic breccia, 

palagonite breccia, lava, pillow lava, pillow breccia, agglomerate, argillite, 

minor limestone. Also includes shoshonites.

Early Oligocene to early Miocene

Kwama Volcanic 

Member

Tofk Basaltic lava Late Oligocene

Iauga Formation Tomv Augite-phyric basalt conglomerate, breccia and tuff, calcareous matrix; 

green tuff, agglomerate, siltstone; younger? poorly consolidated 

conglomerate and sandstone

Late Oligocene to early Miocene

 -- Ts Gabbro, andesitic porphyry, diorite Early Miocene?
Appendix S—Tract 009pCu7208 271

Table S3. Principal sources of information used for tract 009pCu7208, Inner Melanesian Arc Terranes II—Northern New Guinea 

Island, Papua New Guinea. 

[NA, not applicable; CCOP, Coordinating Committee for Geoscience Programmes in East and Southeast Asia]

 Theme Map or title Scale Citation

Geology Digital geologic map of East and Southeast 

Asia

1:2,000,000 CCOP and Geological Survey of Japan (1997)

Digital geologic map of Papua New Guinea 1:250,000 Papua New Guinea Geological Survey (2002)

Geology of Papua New Guinea 1,1,000,000 Bain and others (1972)

Page size maps in published papers. NA Garwin and others (2005), Hill and others (2002), 

Quarles van Ufford and Cloos (2005), and Cloos and 

others (2005) 

SE Asia Radiometric Ages: GIS Database NA Malaihollo and others (2002)

Mineral

occurrences

Porphyry copper deposits of the world: 

database, map, and grade and tonnage 

models

NA Singer and others (2008)

Digital mineral occurrence database for 

Papua New Guinea

1:250,000 Papua New Guinea Geological Survey (2002)

Mineral deposits of Papua New Guinea 1:2,500,000 Granger (1973)

Exploration Tenement maps, reports NA Papua New Guinea Mineral Resources Authority 

(2008a,b), Lole (2005)
272 Porphyry Copper Assessment of Southeast Asia and Melanesia 

References Cited

Ali, J.R., and Hall, Robert, 1995, Evolution of the boundary 

between the Philippine Sea Plate and Australia—

Paleomagnetic evidence from eastern Indonesia: 

Tectonophysics, v. 251, p. 251–275.

Bain, J.H.C., 1973, A summary of the main structural elements 

of Papua New Guinea, in Coleman, P.J., ed., The western 

Pacific—Island arcs, marginal seas, geochemistry: Perth, 

University of Western Australia Press, p. 147–161.

Bain, J.H.C., Davies, H.L., Hohnen, P.D., Ryburn, R.J., Smith, 

I.E., Grainger, R., Tingey, R.J. and Moffar, M.R., compilers, 

1972, Geology of Papua New Guinea, Canberra: Bureau of 

Mineral Resources, Geology and Geophysics, 1 map, 

4 sheets, scale 1:1,000,000.

Cloos, Mark, Sapiie, B., Quarles van Ufford, A., Weiland, 

R.J., Warren, P.Q., and McMahon, T.P., 2005, Collisional 

delamination in New Guinea—The geotectonics of 

subducting slab breakoff: Geological Society of America 

Special Paper 400, 51 p.

Coordinating Committee for Coastal and Offshore Geoscience 

Programmes in East and Southeast Asia (CCOP) and 

Geological Survey of Japan, 1997, Digital geologic map 

of East and Southeast Asia: Geological Survey of Japan, 

Digital Geoscience Map G-2 scale 1:2,000,000, CD-ROM.

Garwin, S., Hall, R., and Watanabe, Y., 2005, Tectonic setting, 

geology, and gold and copper mineralization in Cenozoic 

magmatic arcs of southeast Asia and the west Pacific, in 

Hedenquist, T.W., Thompson, J.F.H., Goldfarb, R.J., and 

Richards, J.P., eds., One hundredth anniversary volume 

1905–2005: Littleton, Colorado, Society of Economic 

Geologists, p. 891–930.

Granger, D.J., compiler, 1973, Mineral deposits of Papua 

New Guinea: Bureau of Mineral Resources, Geology and 

Geophysics, Canberra, 1 sheet, scale 1:2,500,000.

Hill, K.C., Kendrick, R.D., Crowhurst, P.V., and Gow, P.A., 

2002, Copper-gold mineralisation in New Guinea—

Tectonics, lineaments, thermochronology and structure, in 

Korsch, R.J., ed., Geodynamics of Australia and its mineral 

systems—Technologies, syntheses and regional studies: 

Melbourne, Australia, Blackwell Scientific Publications for 

the Geological Society of Australia, p. 737–752.

Jacques, A.L., 1976, High K2

O island-arc volcanic rocks from 

the Finisterre and Adelbert Ranges, northern Papua New 

Guinea: Geological Society of America Bulletin, v. 87, 

p. 861–867.

John, D.A., Ayuso, R.A., Barton, M.D., Blakely, R.J., Bodnar, 

R.J., Dilles, J.H., Gray, Floyd, Graybeal, F.T., Mars, J.C., 

McPhee, D.K., Seal, R.R., Taylor, R.D., and Vikre, P.G., 

2010, Porphyry copper deposit model, chap. B of Mineral 

deposit models for resource assessment: U.S. Geological 

Survey Scientific Investigations Report 2010–5070–B, 169 

p., accessed September 8, 2010, at http://pubs.usgs.gov/

sir/2010/5070/b/.

Lole, H., 2005, The exploration of potential mineral resources 

in Papua New Guinea, 3rd PECC Mineral Network Meeting 

(mining economy and development, and environmental 

protection), 26 p.: accessed January 10, 2010, at www.

pecc.org/community/minerals-shanxi-2005/papers/howardlole(paper).pdf.

Malaihollo, J.F.A., Hall, R., and Macpherson, C.G., 2002, SE 

Asia radiometric ages—GIS database, accessed January 15, 

2010, at http://searg.rhul.ac.uk/current_research/isotopic_

ages/SEAsia_GIS.pdf.

Papua New Guinea Geological Survey, 2002, Digital 

geological map of Papua New Guinea: Australia, Australian 

Geosciences, scale 1:250,000.

Papua New Guinea Mineral Resources Authority, 2008a, 

Quarterly bulletin: accessed July 10, 2009, at http://www.

mra.gov.pg/Portals/0/Publications/bulletin/julysep08/

current%20el%20map.pdf.

Papua New Guinea Mineral Resources Authority, 2008b, 

Papua New Guinea mines and potential projects map 

updated to 2008: accessed July 10, 2009, at http://www.mra.

gov.pg/Portals/0/Mining%20Infor/projects%20map.pdf.

Quarles van Ufford, Andrew, and Cloos, Mark, 2005, 

Cenozoic tectonics of New Guinea: Bulletin of the 

American Association of Petroleum Geologists, v. 89, no. 1, 

p. 119–140.

Singer, D.A., Berger, V.I., and Moring, B.C., 2008, Porphyry 

copper deposits of the world—Database and grade and 

tonnage models, 2008: U.S. Geological Survey Open-File 

Report 2008–1155, accessed June 1, 2011, at http://pubs.

usgs.gov/of/2008/1155/.

Titley, S.R., and Heidrick, T.L. 1978, Intrusion and fracture 

styles of some mineralized porphyry systems of the 

southwestern Pacific and their relationship to plate 

interactions: Economic Geology, v. 73, p. 891–903.

U.S. Department of State, 2009, Small-scale digital 

international land boundaries (SSIB)—Lines, edition 10, 

and polygons, beta edition 1, in Boundaries and sovereignty 

encyclopedia (B.A.S.E.): U.S. Department of State, Office 

of the Geographer and Global Issues.
Figure S1. Map showing the location of permissive tract 009pCu7208, Inner Melanesian Arc Terranes II— Northern New Guinea Island, Papua Ne

sia; PG, Papua New Guinea.

140° E 146° E 152° E

4° S8° S

12°S

PACIFIC OCEAN

Bismarck Sea

Solomon Sea

Coral Sea

PAPUA NEW GUINEA

AUSTRALIA

INDONESIA

140°E 

0°

10°S20°S

AUSTRALI

ID

PG

PAC

Political boundary source: U.S. Department of State (2009)Projection: Asia South Albers Equal Area Conic;Central meridian 147° E; latitude of origin 15° S

0 100 200 300 400 KILOMETERS

0 100 200 MILES

EX

Other Asse009pC

Porpdepotracts Porpprosptracts 
( ( ( ( ( ( ( ( ( ( ( ( 

( ( ( ( ( ( ( ( ( ( ( ( 

( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( RAMU MARKHAM FAULT SOUTHERN BORDER FOLD AND THRUST BELT 140° E 145° E 150° E 5° S 10° S Base from ESRI ArcGIS Online (2009) World Shaded Relief Political boundary source: U.S. Department of State (2009) Projection: Asia South Albers Equal Area Conic; Central meridian 147° E; latitude of origin 15° S 0 200 400 KILOMETERS 0 100 200 MILES 100 300 E

Ass 0

( ( Su

Pe

New Britain Island Pe

PACIFIC OCEAN Bismarck Sea Solomon Sea Coral Sea

INDONESIA PAPUA NEW GUINEA

AUSTRALIA

Figure S2. Map showing igneous rocks used to delineate tract 009pCu7208, Inner Melanesian Arc Terranes II— Northern New Guinea Island, Pa
Appendix T—Tract 009pCu7209 275

Appendix T. Porphyry Copper Assessment for Tract 009pCu7209, 

Inner Melanesian Arc—New Britain, Papua New Guinea

By Jane M. Hammarstrom1, Dulcie Saroa2, Bambang Tjahjono Setiabudi3, Dwi Nugrono Sunuhadi3, Gilpin R. 

Robinson, Jr.1

, Connie L. Dicken1, Steve Ludington4, Arthur A. Bookstrom5, and Michael L. Zientek5, with contributions from Gwaibo Kopi2

 and Dennis P. Cox4

Deposit Type Assessed: Porphyry copper

Descriptive model: Porphyry copper (Berger and others, 2008; Cox, 1986; Cox and others, 1986; John and others, 2010;)

Grade and tonnage model: Porphyry copper, general model (Singer and others, 2008)

Table T1 summarizes selected assessment results.

Table T1. Summary of selected resource assessment results for tract 009pCu7209, Inner Melanesian Arc—New Britain, Papua New 

Guinea.

[km, kilometers; km2, square kilometers; t, metric tons] 

Date of 

assessment

Assessment

depth (km)

Tract area 

(km2)

Known copper 

resources (t)

Mean estimate of 

undiscovered copper 

resources (t)

Median estimate of

undiscovered copper

resources (t)

February 2010 1 17,990 720,000 8,500,000 3,200,000

1

U.S. Geological Survey, Reston, Virginia, United States.

2

Mineral Resources Authority, Papua New Guinea.

3

Center for Geological Resources, Geological Agency of Indonesia, West Java, Indonesia.

4

U.S. Geological Survey, Menlo Park, California, United States.

5

U.S. Geological Survey, Spokane, Washington, United States.

Location

The tract is located on New Britain Island, Papua New Guinea.

Geologic Feature Assessed

Eocene to early Miocene Inner Melanesian Arc on New Britain Island.

Delineation of the Permissive Tract

Tectonic Setting

The New Britain tract represents part of the 1,000-km-long calc-alkaline Inner Melanesian Arc that developed in the 

Eocene to early Oligocene from southwestward subduction of the Pacific Plate along the New Britain Trench (fig. T2). Porphyry 

and high-sulfidation epithermal systems formed during plate reorganization at about 25 Ma, when New Britain was situated at 

the intersection of the South Caroline and Melanesian Arcs (Garwin and others, 2005).
276 Porphyry Copper Assessment of Southeast Asia and Melanesia 

Geologic Criteria

The tract is delineated on the extent of permissive late 

Eocene to early Miocene igneous rocks shown on 1:250,000-

scale geologic maps of New Britain Island. The tract was constructed in a GIS. Map units were classified into generalized 

units by age and lithologic class (igneous volcanic, igneous 

plutonic). From this digital database of geologic lithology and 

age attributes, all Eocene to early Miocene igneous rocks were 

selected. Map units included in the tract are listed in table T2.

The final tract boundaries were established by a GIS 

processing and editing. The processing steps included (1) 

buffering permissive map units with a 5-km concentric buffer; 

(2) unioning buffered permissive map units and other polygon 

features that comprise the framework of the tract; (3) aggregating unioned polygons using an aggregation distance of 15 km 

and a minimum hole size of 1,000 km2

, a step done to group 

closely spaced permissive areas; (4) manually aggregating and 

adjusting tract areas; and (5) smoothing polygons. Preliminary 

tracts were cleaned to remove necking and thinning introduced 

by processing; tracts were compared with source maps to 

ensure that original permissive boundaries and buffer distances were honored. Regional and local mineral-occurrence, 

geochemical, and isotopic-age data were plotted and used to 

constrain or expand tract boundaries; in particular, a database 

of isotopic ages of igneous rocks for Indonesia compiled 

by the Southeast Asia Research Group provided additional 

controls on distributions of permissive rocks (Malaihollo and 

others, 2002). Tract boundaries were clipped at shorelines 

(U.S. Department of State, 2009).

The tract terminates at the Bismarck Sea on the north and 

the Solomon Sea on the south. Parts of the island in the west, 

north, and northeast were not included in the tract because 

they contain Quaternary sediment estimated to be thicker 

than 1 km, based on examination of cross-sections shown on 

1:250,000-scale geologic maps. Other data used to construct 

the tract includes the 1:2,000,000-scale regional geologic map 

(Coordinating Committee for Coastal and Offshore Geoscience 

Programmes in East and Southeast Asia (CCOP) and Geological 

Survey of Japan, 1997), the 1:1,000,000-scale geologic map of 

Papua New Guinea, and local and regional mineral-occurrence 

databases (Bain and others, 1972; Granger, 1973; Hughes, 1990).

Table T2. Map units that define tract 009pCu7209, Inner Melanesian Arc—New Britain, Papua New Guinea.

[Map unit, age range, and principal lithologies are based on attributes in a digital compilation of geologic maps of Papua New Guinea Indonesia (Papua New 

Guinea Geological Survey, 2002). Numbers and publication dates of 1:250,000-scale maps available from the Papua New Guinea Geological Survey are listed for 

reference. --, no map unit] 

Map unit Map 

symbol Lithology Age range Map number

Map 

date

Intrusive rocks 

 - - Ti Leucogabbro, basic diorite, diorite, microdiorite, tonalite, granodiorite, 

monzonite and adamellite

Late Eocene to 

Miocene

B5602 1970

 - - Toi Tonalite, gabbro, diorite, granodiorite, adamellite, monzonite, mangerite; 

related porphyries and microplutonic rocks

Late 

Oligocene

B5605 1971

 - - Toip Intrusive-extrusive complex of rhyolite, dacite, andesite and tuff, 

rhyodacite porphyry

Late 

Oligocene

B5605 1971

Volcanic rocks 

Kapuluk 

Volcanics

Tok Zeolitic volcanic breccia, lapilli tuff and tuff, commonly maroon or green, 

basaltic and andesitic lavas, non-indurated marine sandstone and siltstone

Late 

Oligocene

B5508 1973

Baining 

Volcanics

Teb Massive indurated highly jointed basaltic or andesitic lava, agglomerate, 

conglomerate, volcanic breccia, arenite, minor lutite, tuff, hypabyssal 

rocks, basic to intermediate lavas metamorphosed in some areas, minor 

recrystallized limestone

Late Eocene B5602 1970

Andewa Volcanic 

Complex

Qs Anedsitic, basaltic, and dacitic lavas and pyroclastics, andesite porphyry, 

microdiorite

Pleistocene to 

Holocene

B5508 1973

Mungu Volcanics Tpm Dacite, rhyodacite, andesite, pumiceous tuff Pliocene B5605 1971
Appendix T—Tract 009pCu7209 277

The geology of New Britain consists of Neogene sedimentary rocks and Paleogene felsic volcanic and sedimentary 

rocks, which are intruded locally by Eocene and Oligocene 

felsic plugs (fig. T2). The lowlands on the north and west and 

east ends of the island are composed of Quaternary mafic 

volcanic rocks. Mineralized areas contain intrusive bodies of 

aplite, diorite porphyry, granodiorite, quartz porphyry, gabbro, 

tonalite, dacite porphyry, granodiorite porphyry, and quartz 

diorite porphyry. Volcanic equivalents of these rocks are breccia, andesite, agglomerate, basalt, and rhyolite tuff. Country 

rocks consist of hornfels, limestone, and limestone breccia 

(Hine and Mason, 1978). Late Miocene and Pliocene volcanic 

rocks represent cover in some parts of the tract.

Porphyry prospects on New Britain have been dated at 

24–25 Ma (Whalen and McDougall, 1980; Page and Ryburn, 

1977). Three major intrusive episodes accompanied development of the of the Uasilau-Yau Yau intrusive complex in the 

central part of the island: Group 1 rocks (gabbro and quartz 

diorite) are at least 30 million years old, Group 2 intrusions 

(quartz diorite, tonalite, and granodiorite) formed at about 28.4 

Ma, and Group 3 tonalite formed at about 23.5 Ma (Whalen 

and McDougall, 1980). These intrusive events were followed 

by hydrothermal alteration, copper mineralization, and quartzfeldspar porphyry emplacement. Copper prospects associated 

with this intrusive complex include Uasilau and Yau Yau (fig. 

T1). K-Ar ages for Pleysumi (24.5 Ma), Kulu (22.6 Ma), 

and Esis (<25 Ma) were reported by Titley (1978), Page and 

Ryburn (1977), and Hine and others (1978). Based on their 

study of the Uasilau-Yau Yau area, as well as age determinations on other prospects, Whalen and McDougall (1980) 

suggested that all of the New Britain porphyry copper deposits 

formed in the late Oligocene-early Miocene.

Known Deposits

Simuku is the only porphyry copper deposit on New 

Britain Island that has reported tonnage and grade information 

(table T3), with inferred resources of 200 Mt at 0.36 percent 

copper, 0.07 g/t gold, 0.0076 percent molybdenum, and 2 g/t 

silver (Coppermoly, Ltd., 2009). Drilling in 2010 identified 

broad zones of copper mineralization south of the area delineated for inferred resources, as well as mineralized skarn along 

the western margins of the deposit (Coppermoly, Ltd., 2011).

Prospects, Mineral Occurrences, and Related 

Deposit Types

Several porphyry copper systems are present in the 

mountain ranges of central New Britain Island (Garwin and 

others, 2005; Singer and others, 2008). These include partially 

explored deposits at Esis, Mount Nakru, and Plesyumi (fig. 

T1); no resource estimates are available for these deposits 

(table T4). Ore minerals include bornite, chalcopyrite, galena, 

molybdenite, and sphalerite. Pyrite, stannite, and cassiterite 

also have been reported. Supergene minerals include chalcocite, copper, covellite, cuprite, gold, goethite, and jarosite (Hine 

and others, 1978; Titley, 1978).

The geology of the Esis prospect was first described 

by Hine and others (1978). Copper mineralization is hosted 

in quartz diorite and magnetite breccias exposed on a westnorthwest-trending ridge on the western side of a granitoid 

complex. Esis is within the Likuruanga exploration license 

area (Frontier Resources, Ltd., 2008, 2011), where recent drilling intercepted copper (>0.2 weight percent) over the entire 

length of six shallow drill holes; previous drilling established 

a supergene copper zone (152.6 m of 0.39 percent copper, 24 

ppm molybdenum). Surface-rock sampling, magnetic data, 

and radiometric potassium data outline the Esis porphyry 

target area, as well as a gold-zinc-lead-copper epithermal-vein 

prospect and a gold-zinc skarn exploration target to the north 

of Esis (Frontier Resources, Ltd., 2011).

The Kulu prospect, located about 4 km southeast of 

Simuku, is in early Miocene dacite porphyry, porphyritic 

andesite, and microdiorite near a contact with the late Oligocene Kulu batholith (Hutchison and Swiridiuk, 2006). 

Kulu lies within the exploration license areas for the Simuku 

property.

The Pleysumi porphyry copper-gold prospect in central 

New Britain is associated with a large, multiphase igneous 

complex. Post-mineral ash and sediments cover parts of the 

area; erosion at Pleysumi exposes the prospect. Mount Nakru, 

also located in the central New Britain exploration area, is 

a caldera structure with copper-gold-molybdenum breccias 

(New Guinea Gold Corporation, 2009, 2011).

The Sinivit gold mine (quartz-alunite epithermal system) 

in East New Britain Province in the northeastern part of the 

island exploits an oxide cap which contains gold, and telluride 

and copper minerals. The deposit is localized along a 1 by 10 

km structural zone (Lindley, 1990; New Guinea Gold Corporation, 2009; Stagg, 2006). Porphyry-style alteration (potassic, 

argillic, sericitic, propylitic) is associated with the composite 

Magiabe Valley porphyry intrusion, west of the Mount Sinivit 

gold deposit. The porphyry intrudes coeval volcanic rocks 

(late Oligocene to early Miocene) (Lindley, 1998). Disseminated chalcopyrite and bornite occur in potassic alteration 

zones in micromonzodiorite and monzonite and in a propylitic 

halo characterized by chlorite, calcite, epidote, and pyrite 

(Stagg, 2006). Alluvial gold probably is derived from a sericitized pebble breccia. Surface exposures are depleted in copper 

and silver because of tropical weathering, which formed a 

25-m-thick oxide zone, with a possible copper-enrichment 

zone (chalcocite) below. The Magiabe intrusion was interpreted by Stagg (2006) as having potential for a porphyrystyle copper-gold deposit, albeit one in the early stages of 

unroofing.

The Andewa gold-copper prospect in western New 

Britain has indications of early porphyry mineralization overprinted by a telescoped epithermal gold system in the caldera of 

the extinct calc-alkaline Mount Andewa stratovolcano. Phyllic 

alteration is associated with andesite and diorite dikes. Anomalous copper (400–600 ppm to 0.3–0.4 percent) encountered in 
278 Porphyry Copper Assessment of Southeast Asia and Melanesia 

drilling the Komsen epithermal gold target, mineralized porphyry float, and an IP anomaly consistent with a possible large 

sulfide-bearing systems in the subsurface are the only indications of a possible porphyry system to date (Frontier Resources, 

Ltd., 2010). The prospect appears to be associated with the 

Pleistocene to Holocene Andewa Volcanic Complex, unlike the 

other porphyry systems on New Britain, which all appear to 

have formed in the late Oligocene to early Miocene.

Exploration History

Exploration has taken place around the Plesyumi, Esis, 

and Kulu (~3.5 km from Simuku) porphyry copper systems 

and a nearby epithermal gold occurrence. Plesyumi was 

discovered in 1968. The Esis porphyry copper prospect was 

discovered in 1971 based on anomalous copper in stream 

sediments and identification of sulfide minerals in float 

(Hine and others, 1978); 1970s exploration ceased when 

copper prices dropped. Frontier Resources, Ltd., started to 

re-evaluate Esis in 2008 (trench, rock-chip, soil sampling) 

for a hypothetical exploration target on the order of >150 Mt 

grading 0.4 percent copper or more, based on historical data. 

Previous exploration included 4 diamond drill holes (150 m 

each) and 15 shallow holes; the best drill intercepts included 

152.6 m grading 0.39 percent copper and 24 ppm molybdenum. No resource estimates are available for Esis; preliminary 

work by Frontier reportedly confirmed previous copper and 

gold assays (Frontier Resources, Ltd., 2010). Exploration by 

Esso Minerals and CRA on New Britain in the 1980s identified gold and copper anomalies in rock chips; these exploration areas are included in MIL Resources’ New Britain Project. 

MIL Resources 5,000-m drilling program was slated to begin 

in April of 2011 at the Esis porphyry copper-gold prospects 

within the Likuruanga Exploration Licenses area; drill targets 

are based on magnetic data and surface-rock sampling (Frontier Resources, Ltd., 2011).

Sources of Information

Principal sources of information used by the assessment 

team for delineation of 009pCu7209 are listed in table T5.

Grade and Tonnage Model Selection

Simuku, with a gold/molybdenum ratio of 10, meets 

the criteria of Singer and others (2008) for the general 

type of porphyry copper deposit (Cu-Au-Mo) rather than a 

copper-gold (Cu-Au) subtype. ANOVA tests of the reported 

tonnage and grade for Simuku do not reject the general or 

Cu-Au subtype models for tonnage, copper, or molybdenum; 

however, gold is significantly different from both models at 

the 1-percent test level (table 6). Partial exploration data for 

the Esis and Plesyumi porphyry copper prospects suggest 

that both gold and molybdenum may be present; anomalous 

gold and copper values in stream sediments near Esis contribute to its current status as an exploration target (Frontier 

Resources, Ltd., 2011). Garwin and others (2005) described 

the deposit style in the Inner Melanesian Arc as porphyry 

copper-gold, associated with oceanic crust. Model selection 

for this tract is problematic based on available information. 

The general global Cu-Au-Mo model of Singer and others 

(2008) was chosen based on the reported grades for Simuku 

and as a default model.

Estimate of the Number of Undiscovered Deposits

Rationale for the Estimate

The tract contains one deposit with reported inferred 

resources. Three other potential deposits have been known 

since the 1960s. The extensive volcanic cover (fig. T3), 

remoteness, heavy vegetation, and incomplete exploration 

are factors that lead to the conclusion that additional undiscovered porphyry copper deposits may be present in the 

tract. The proportions of permissive volcanic rocks versus 

intrusions suggest that the level of erosion is appropriate 

and that additional intrusions may be present under shallow 

cover. Porphyry systems are known in the vicinity of the 

Sinivit gold deposit (Lindley, 1998). The Uasilau-Yau Yau 

Table T3. Known porphyry copper deposits in tract 009pCu7209, Inner Melanesian Arc—New Britain, Papua New Guinea.

[Ma, million years; Mt, million metric tons; t, metric ton; %, percent; g/t, gram per metric ton; Cu-Mo subtype, deposits that have Au/Mo ratios <3 or average 

Mo grades >0.03%; Cu-Au subtype, deposits that have Au/Mo ratios >30 or average Au grades >0.2 g/t; NA, not applicable. Contained Cu in metric tons is 

computed as tonnage (Mt × 1,000,000) × Cu grade (percent). *, Inferred resources based on drilling; open (Coppermoly, 2009; Singer and others, 2008)]

Name Latitude Longitude Subtype Age

(Ma) Tonnage

Grade Contained 

Cu (t) Reference

Cu (%) Mo (%) Au (g/t) Ag (g/t)

Simuku* −5.733 150.033 NA 24 200 0.36 0.008 0.07 2 720,000 Coppermoly, Ltd. (2009), 

Hutchison, and Swiridiuk 

(2006), Singer and others 

(2008)
Appendix T—Tract 009pCu7209 279

Table T4. Significant prospects and occurrences, tract 009pCu7209, Inner Melanesian Arc—New Britain, Papua New Guinea.

[Rank 4=Prospect listed in global database of Singer and others (2008) or <16,000 t of ore established by drilling. Rank 3=drilled, with >20 m of 0.2% 

or more Cu. Rank 2=drilled or trenched with <20 m of 0.2% Cu or <0.2% Cu, or past or ongoing exploration. Rank 1=copper occurrence that may be 

related to porphyry-type mineralization based on stream sediment or magnetic anomaly or location along structural trend. n.d., no data; %, percent; g/t, 

grams per metric ton; km, kilometers; m, meters]

Name Latitude Longitude Age Comments Reference Rank

Plesyumi −5.967 150.383 24 Intersections 44 m at 0.85% Cu; 110 m at 

0.31% Cu; and 101 m at 0.2% Cu.

Singer and others (2008), Christopher 

(2002), Hine and Mason (1978), 

Mason and McDonald (1978), Titley 

(1975,1978), Vangold Resources, Ltd. 

(2006)

4

Esis −5.176 151.709 25 Breccia-related porphyry copper prospect 

associated with Uasilau-YauYau intrusive 

complex. Mineralization in quartz diorite 

and magnetite-bearing breccias. Primary 

mineralization: 6 shallow drill holes with 

weighted copper average >0.2%; 1,400 m by 400–

1,000 m zone of copper mineralization; open. 

Hine and Mason (1978), Hine and 

others (1978), Singer and others 

(2008), Frontier Resources, Ltd. 

(2008, 2011)

4

Mount 

Nakru

−5.983 150.467 24 Intersections: 94 m at 0.43% Cu, 0.46 g/t Au; 

205 m at 0.4% Cu; 54 m at 0.18 g/t Au.

Christopher (2002), Lole (2005), 

Vangold Resources Ltd. (2006), 

Singer and others (2008)

4

Uasilau −5.611 150.942 24 NW end of a 9 km by 2 km long, 1–2 km 

wide zone of low-grade porphyry copper-type 

mineralization (<0.3% Cu) associated with 

quartz diorite and tonalite in an area of 

anomalous stream-sediment copper.

Whalen and McDougall (1980) 2

Yau Yau −5.616 150.955 24 SE end of a 9 km by 2 km long, 1–2 km-wide 

zone of low-grade porphyry copper-type 

mineralization (<0.3% Cu)

Whalen and McDougall (1980) 2

Andewa −5.547 148.964 n.d. Indication of porphyry copper-gold system 

overprinted by a telescoped epithermal gold 

system in a Pleistocene-Holocene calc-alkaline 

caldera complex. 

Frontier Resources, Ltd. (2010) 2

Sinivit 

(Magiabe 

Valley)

−4.623 152.047 n.d. Disseminated chalcopyrite and bornite in 

potasically-altered composite intrusion 

(micromonzodiorite and monzonite); phyllic 

altered pebble breccia; explored based on 

magnetic anomaly. 

Lindley (1998), New Guinea Gold 

Corporation (2009), Stagg (2006)

1

Pelapuna −5.709 150.963 n.d. Copper prospect Papua New Guinea Geological Survey 

(2002)

1

Unnamed 

Cu prospect

−5.613 150.918 n.d. Copper prospect Papua New Guinea Geological Survey 

(2002)

1

Kulu −5.743 150.065 23 Porphyry copper prospect associated with 

Uasilau-YauYau intrusive complex.

Whalen and McDougall (1980) 1
280 Porphyry Copper Assessment of Southeast Asia and Melanesia 

trend has not been fully explored. The tract includes about 

20 reported copper prospects or occurrences (Papua New 

Guinea Geological Survey, 2002). Most of the tract area was 

under exploration license in 2008. On the basis of this information, the team estimated a 90-percent chance of one or 

more deposits, a 50-percent chance or two or more deposits, 

and a 10-percent chance of four or more deposits (table T6). 

Although the tract area is small (~16,000 km2

), the presence 

of significant prospect areas within the tract and the gap of 

approximately 20 years in exploration suggest that a 10-percent chance of four or more deposits is not an unreasonable 

estimate. This distribution results in a mean of 2.2 deposits 

with a low coefficient of variation (Cv%=54).

Probabilistic Assessment Simulation 

Results

Undiscovered resources for tract 009pCu7209 were 

estimated by combining consensus estimates for numbers of 

undiscovered porphyry copper-gold deposits with the porphyry copper-gold model using the EMINERS program (Root 

and others, 1992; Bawiec and Spanski, 2012; Duval, 2012). 

Selected output parameters are reported in table T7. Results 

of the Monte Carlo simulation are presented as a cumulative 

frequency plot (fig. T3). The simulation predicts a mean of 

8.5 Mt of copper and a median of 3.2 Mt of copper. Identified 

resources within the tract are 720,000 tons of copper.

Table T5. Principal sources of information used for tract 009pCu7209, Inner Melanesian Arc—New Britain, Papua New Guinea.

[NA, not applicable; CCOP, Coordinating Committee for Geoscience Programmes in East and Southeast Asia]

Theme Map or title Scale Citation

Geology Digital geologic map of East and Southeast Asia 1:2,000,000 CCOP and Geological Survey of Japan (1997)

Geology of Papua New Guinea 1;1,000,000 Bain (1972)

Digital geology of Papua New Guinea 1:250,000 Papua New Guinea Geological Survey (2002)

Geologic quadrangle maps 1:250,000 Bureau of Mineral Resources, Geology and Geophysics, 

and Geological Survey of Papua New Guinea (1970, 1973, 

1974)

SE Asia Radiometric Ages: GIS Database NA Malaihollo and others (2002)

Mineral

occurrences

Porphyry copper deposits of the world: database, 

map, and grade and tonnage models

NA Singer and others (2008)

Geology of the Mineral Deposits of Australia and 

Papua New Guinea

1;35,000,000 Hughes (1990)

Mineral deposits of Papua New Guinea 1:2,500,000 Granger (1973)

Digital geology of Papua New Guinea (mineral 

occurrence point file)

 1:250,000 Papua New Guinea Geological Survey, 2002

Exploration Company Web sites NA Frontier Resources, Ltd. (2008, 2010), New Guinea Gold 

Corporation (2011), Coppermoly, Ltd. (2009, 2011), MIL 

Resources Limited (2010)

Papua New Guinea Mineral Resources Authority 

reports and tenement map, exploration reviews

NA Mineral Resources Authority of Papua New Guinea (2008), 

Legge (1999) , Lole (2005)

CCOP country report NA Dulcie Saroa (oral commun., 2010)
Appendix T—Tract 009pCu7209 281

Table T6. Undiscovered deposit estimates, deposit numbers, tract area, and deposit density for tract 009pCu7209, Inner Melanesian 

Arc—New Britain, Papua New Guinea.

[NXX, estimated number of deposits associated with the xxth percentile; Nund, expected number of undiscovered deposits; s, standard deviation; Cv%, coefficient of 

variance; Nknown, number of known deposits in the tract that are included in the grade and tonnage model; Ntotal, total of expected number of deposits plus known 

deposits; km2, area of permissive tract in square kilometers; Ntotal/100k km2, deposit density reported as the total number of deposits per 100,000 km2. Nund, s, and 

Cv% are calculated using a regression equation (Singer and Menzie, 2005)]

 Consensus undiscovered deposit estimates Summary statistics Tract area 

(km2

)

Deposit density 

(Ntotal/100k km2) N90 N50 N10 N05 N01 Nund s Cv% Nknown Ntotal

1 2 4 4 4 2.2 1.2 54 1 3.2 17,990 18

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Papua New Guinea.

[Cu, copper; Mo, molybdenum; Au, gold; and Ag, silver; in metric tons; Rock, in million metric tons]

Material

Probability of at least the indicated amount Probability of

0.95 0.9 0.5 0.1 0.05 Mean Mean or 

greater None

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Mo 0 0 38,000 500,000 1,000,000 230,000 0.20 0.27

Au 0 0 62 520 820 210 0.26 0.23

Ag 0 0 350 5,800 11,000 2,700 0.20 0.37

Rock 0 45 730 3,700 6,400 1,700 0.26 0.07
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Appendix T—Tract 009pCu7209 283

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150° E 152° E 4° S 6° S Kulu Esis Simuku Yau Yau Uasilau Plesyumi Pelapuna Mt. Nakru Unnamed Copper prospect Sinivit (Magiabe Valley) Andewa gold-copper project Bismarck Sea Solomon Sea 140°E 

0° 10°S AUSTRAL

PG PA

Political boundary source: U.S. Department of State (2009) Projection: Asia South Albers Equal Area Conic; Central meridian 151° E; latitude of origin 15° S 0 25 50 75 100 KILOMETERS 0 25 50 MILES EX

OtheAsse009p

PorpPorp

Figure T1. Map showing the location, known deposits, and significant prospects and occurrences for permissive tract 009pCu7209, Inner MelanPapua New Guinea. PG, Papua New Guinea; SB, Solomon Islands.
( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( (

(

(

(

(

( (

(

( ( ( ( ( ( ( 

Kulu

Esis

Simuku

Yau YauUasilau

Plesyumi

Pelapuna

Mt. Nakru

Unnamed Copper prospect

Sinivit (Magiabe Valley)

Andewa gold-copper project

5° S

150° E

Base from ESRI ArcGIS Online (2009)World Shaded ReliefPolitical boundary source: U.S. Department of State (2009)Projection: Asia South Albers Equal Area Conic;Central meridian 150° E; latitude of origin 15° S

0 25 50 75 100 KILOMETERS

0 25 50 MILES

E

Ass 0PePePoPo

( ( Su

PACIFIC PLATE

Bismarck Sea

NEW BRITAIN TRENCH Solomon Sea

Figure T2. Map showing igneous rocks used to delineate tract 009pCu7209, Inner Melanesian Arc—New Britain, Papua New Guinea.
286 Porphyry Copper Assessment of Southeast Asia and Melanesia 

1.00

0.90

0.80

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

Probability

0.01 0.1 1 10 100 1k 10k 100k 1M 10M 100M 1B 10B 100B

Material, in metric tons

Cu

Mo

Au

Ag

Rock

Mean Cu

Mean Mo

Mean Au

Mean Ag

Mean Rock

EXPLANATION

Mean Cu

Mean Mo

Mean Au

Mean Ag

Mean Rock

Figure T3. Cumulative frequency plot showing the results of Monte Carlo computer simulation of undiscovered 

resources in tract 009pCu7209, Inner Melanesian Arc—New Britain, Papua New Guinea. k, thousands; M, millions; B, 

billions.
Appendix U—Tract 009pCu7207 287

Appendix U. Porphyry Copper Assessment for Tract 009pCu7207, 

Outer Melanesian Arc I—Papua New Guinea

By Jane M. Hammarstrom1, Dulcie Saroa2, Bambang Tjahjono Setiabudi3, Dwi Nugrono Sunuhadi3, Gilpin R. 

Robinson, Jr.1

, Connie L. Dicken1, Steve Ludington4, Arthur A. Bookstrom5, and Michael L. Zientek5, with contributions from Gwaibo Kopi2 and Dennis P. Cox4

Deposit Type Assessed: Porphyry copper, copper-gold subtype

Descriptive model: Porphyry copper (Berger and others, 2008; John and others, 2010); Porphyry copper-gold 

(Cox, 1986; Cooke and others, 1998)

Grade and tonnage model: Porphyry copper, copper-gold subtype (Singer and others, 2008)

Table U1 summarizes selected assessment results.

Table U1. Summary of selected resource assessment results for tract 009pCu7207, Outer Melanesian Arc I—Papua New Guinea.

[km, kilometers; km2, square kilometers; t, metric tons] 

Date of

assessment

Assessment depth 

(km)

Tract area 

(km2)

Known

copper 

resources (t)

Mean estimate of 

undiscovered copper 

resources (t)

Median estimate of

undiscovered copper

resources (t)

February 2010 1 16,830 7,131,000 17,000,000 9,800,000

1

U.S. Geological Survey, Reston, Virginia, United States.

2

Mineral Resources Authority, Papua New Guinea.

3

Center for Geological Resources, Geological Agency of Indonesia, West Java, Indonesia.

4

U.S. Geological Survey, Menlo Park, California, United States.

5

U.S. Geological Survey, Spokane, Washington, United States.

Location

The tract includes the following islands of Papua New Guinea: Manus, New Ireland, Bougainville, and the Bismarck 

archipelago (Tabar-Lihir-Feni Islands) (fig. U1).

Geologic Feature Assessed

Eocene to Holocene Outer Melanesian magmatic arc, Papua New Guinea.

Delineation of the Permissive Tract

Tectonic Setting

The tract outlines exposed segments of the >800 km Outer Melanesian Arc in Papua New Guinea. The oceanic Outer 

Melanesian Arc (fig. 2 of main report, no. 15) is the northern extension of the Solomon Arc that formed starting in the Eocene-
288 Porphyry Copper Assessment of Southeast Asia and Melanesia 

Oligocene as a consequence of southwesterly subduction of 

the Pacific Plate (Garwin and others, 2005). The term “Outer 

Melanesian Arc” is used in this report to refer to the system of 

arcs that extends from Papua New Guinea to Tonga, following 

the use of the term by Hill and Hall (2003). The arc system 

south of Papua New Guinea (Solomon Islands, Vanuatu and 

Fiji) is described in tract 009pCu7210.

The northernmost islands of the Outer Melanesian Arc, 

Manus and New Ireland, host Miocene porphyry copper 

prospects. In the early Pliocene, there was a reversal in subduction polarity caused by establishment of northeasterly directed 

subduction of the New Britain slab beneath the Inner and Outer 

Melanesian Arcs. The strike and dip of the subducting New 

Britain slab varies throughout the Melanesian Arcs, as does 

the age and character of the magmatism. Bougainville hosts 

Pliocene porphyry copper deposits associated with calc-alkaline 

diorite to granodiorite stocks. The Tabar-Feni-Lihir Islands 

(New Ireland offshore islands), which lie about 400 km above 

the subducting New Britain slab, represent a series of uplifted 

and eroding Pliocene to Holocene stratovolcanoes that have 

a shoshonitic K-alkaline geochemical signature interpreted as 

reflecting a contribution from subducted mantle material (Garwin and others, 2005). Lindley (2006) noted that major, generally northerly, structural corridors localized the emplacement 

of mineralized Tertiary intrusions in New Britain, New Ireland, 

and Manus Island. These structural corridors are oblique to 

major morphotectonic features, such as the New Britain Trench. 

High-angle structures predominate in the region, resulting in 

vertical uplift of crustal blocks, such as the north-trending horst 

blocks that comprise the basement in the New Ireland offshore 

island chain (Lindley, 2006; Garwin and others, 2005).

Geologic Criteria

The tract was delineated in a GIS by selecting Eocene to 

Pliocene or Quaternary (depending on subarea) igneous rocks 

from the digital 1:250,000-scale geologic map of Papua New 

Guinea (Mineral Resources Authority of Papua New Guinea, 

2002). Igneous rocks used for the basis of the tract are shown 

in figure U2. A 5-km buffer area was created around the 

permissive units to extend the permissive area under younger 

cover. The final tract boundaries were established by a GIS 

processing and editing. The processing steps included (1) 

buffering permissive map units with a 5-km concentric buffer; 

(2) unioning buffered permissive map units and other polygon 

features that comprise the framework of the tract; (3) aggregating unioned polygons using an aggregation distance of 15 km 

and a minimum hole size of 1,000 km2

, a step done to group 

closely spaced permissive areas; (4) manually aggregating and 

adjusting tract areas; and (5) smoothing polygons. Preliminary 

tracts were cleaned to remove necking and thinning introduced 

by processing; tracts were compared with source maps to 

ensure that original permissive boundaries and buffer distances were honored. Regional and local mineral-occurrence, 

geochemical, and isotopic-age data were plotted and used to 

constrain or expand tract boundaries; in particular, a database 

of isotopic ages of igneous rocks for Indonesia compiled 

by the Southeast Asia Research Group provided additional 

controls on distributions of permissive rocks (Malaihollo and 

others, 2002). Tract boundaries were clipped at shorelines 

(U.S. Department of State, 2009).

The area of permissive rocks on individual islands and 

the size of some entire islands can be quite small; however, the 

Outer Melanesian Arc represents a geologic feature that hosts 

important porphyry copper deposits. We assessed the arc in 

Papua New Guinea as a whole, but we describe the permissive 

rocks (table U2), known deposits (table U3), and prospects 

(table U4) within each arc segment. Much of the arc may be 

submerged; however, the assessment is limited to island areas.

A. Manus Island.—On Manus Island the tract was delineated on igneous rocks that are exposed in the central highlands of Manus Island, the largest of the Admiralty Islands. 

The porphyry copper prospects on Manus Island are associated 

with middle Miocene calc-alkaline intrusive rocks. Solomon 

(1990) noted that development of these porphyry systems, as 

well as those on New Britain Island, preceded post-Miocene 

subduction related to the New Britain Trench.

The tract extends to the island’s south margin at the 

Bismarck Sea and northern coast on the South Pacific Ocean. 

Western Manus Island is dominated by Quaternary mafic 

volcanic rocks (Pleistocene basalts) and Pliocene agglomerates. Neogene rocks spatially associated with porphyry copper 

mineralization are andesite agglomerate, basalt, basaltic pyroclastics, conglomerate, limestone, tuffaceous sandstone, and 

tuffaceous siltstone (Mason and McDonald, 1978). The known 

porphyry copper occurrences are Miocene in age (Jaques and 

Webb, 1975). Eastern parts of the island are dominated by 

sedimentary rocks, middle Miocene to Pliocene basalts, and 

Pleistocene to Holocene gravels, sands, and silts.

B. New Ireland Island.—The tract includes early or middle 

Oligocene and middle Miocene intrusive rocks of the Lemau 

Intrusive Complex and younger diorite and quartz diorite, 

including porphyry. The Legusulum porphyry copper prospect 

is associated with diorite, diorite porphyry, gabbro, granodiorite 

and associated agglomerate and pyroclastic rocks (Mason and 

McDonald, 1978). Host rocks include volcanic and sedimentary 

rocks. The southern part of New Ireland Island is dominated by 

Paleogene volcanic rocks, the central part by Neogene sedimentary rocks, and the northern part by Quaternary sediments.

C. Bismarck Archipelago (Tabar, Lihir, Tanga, and 

Feni Islands).—Tabar, Lihir, Tanga, and Feni are four volcanic island groups (listed from north to south) that form a 

chain parallel to the east coast of New Ireland Island. The 

tract includes rocks mapped as Quaternary volcanic rocks 

of predominantly andesitic composition, cut by hypabyssal intrusions. Five stratovolcanoes of high-K igneous rocks 

are described on Lihir Island; compositions range from 

porphyritic trachybasalt through trachyandesite to latite cut 

by monzodiorite stocks (Müller and others, 2001). The Feni 

Islands also represent eroded calderas with epithermal systems 

overprinting porphyry copper-gold systems. Active hydrothermal systems are present on some islands, including Lihir.
Appendix U—Tract 009pCu7207 289

Table U2. Map units that define tract 009pCu7207, Outer Melanesian Arc I—Papua New Guinea.

[Map unit, age range, and principal lithologies are based on a attributes in a digital compilation of geologic maps of Papua New Guinea Indonesia (Papua New 

Guinea Geological Survey, 2002). Numbers and publication dates of 1:250,000-scale maps available from the Papua New Guinea Geological Survey are listed 

for reference. - -, no map unit] 

Map unit Map 

symbol Lithology Age range Map number

Map 

date

Intrusive rocks on Manus Island

Yirri Intrusive 

Complex

Tmy Quartz monzodiorite, quartz diorite, quartz 

monzonite, tonalite with porphyry phases 

of microdiorite, microtrondhjemite, quartz 

micromonzodiorite, quartz microdiorite, dacite, 

and andesite

Late early to middle Miocene A5510 1975

Yirri Intrusive 

Complex (alunitic 

phase)

Tmyd Pyritic quartz-alunite-zeolite breccia; altered and 

brecciated porphyritic quartz micromonzonite, 

micromonzodiorite, and andesite pyroclastics and 

lava

Late early to middle Miocene A5510 1975

Yirri Intrusive 

Complex (Dremsel 

alunitic phase)

Tmyp Porphyritic quartz micromonzonite, 

micromonzodiorite, microdiorite, andesite

Late early to middle Miocene A5510 1975

Volcanic rocks on Manus Island

Tinniwi Volcanics Tot Indurated, veined, andesite and basalt agglomerate, 

and lapilli tuff, lava breccia and lava; indurated 

tuffaceous lithic greywacke; some limestone lenses 

near top

Late Eocene to early Miocene A5510 1975

Intrusive rocks on New Ireland Island

Lemau Intrusive 

Complex

Tomb Gabbro, norite, diorite (mostly leucocratic), 

rhyodacite plugs

Early or middle Oligocene and 

middle Miocene

A5614, 

B5603

1973

Lemau Intrusive 

Complex

Toma Granodiorite, tonalite, trondhjemite Early or middle Oligocene and 

middle Miocene

A5614, 

B5603

1973

- - Tmi Diorite, quartz diorite, porphyritic microdiorite Late? Miocene to early Pliocene A5609 1973

Volcanic rocks on New Ireland Island

Jaulu Volcanics Toj Porphyritic andesitic and minor basaltic lapilli 

tuff, agglomerate; minor welded ash-flow tuff, 

amygdaloidal and pillow lava, lava breccia; 

tuffaceous limestone

Early to middle (or early late) 

Oligocene

A5609, 

A5614, 

B5603

1973

Lavongai Volcanics Tmv, 

Tmvb

Porphyritic basaltic andesite, dacite, agglomerate, 

lapilli tuff, lava, lava breccia, bentonite; minor 

intercalated volcanic conglomerate and sandstone; 

minor porphyritic micromonzonite, microdiorite, 

andesite and dacite dykes, pebble dykes and stocks

Late? Miocene to early Pliocene A5609 1973
290 Porphyry Copper Assessment of Southeast Asia and Melanesia 

Table U2. Map units that define tract 009pCu7207, Outer Melanesian Arc I—Papua New Guinea.—Continued

Map unit Map 

symbol Lithology Age range Map number

Map 

date

Intrusive rocks on New Ireland Island

Rataman Formation Tmr Andesitic and dacitic crystal-lithic tuff, volcanolithic 

arenite and lutite, foraminiferaI marl and limestone

Late Miocene A5614, 

B5603

1973

Intrusive rocks on Bougainville

- - Czd Microdiorite, diorite, monzonite, granodiorite, syenite, 

granophyre

Oligocene? to 

Pleistocene?

B5608, 

B5612

1966

Volcanic rocks on Bougainville

Balbi Volcanics Czb Andesite, tuff, agglomerate, derived fan deposits Pliocene? to Holocene B5608, 

B5612

 1966

Emperor Range 

Volcanic Beds

Cze Andesite, basalt, agglomerate, tuff, derived fan deposits Pliocene? to Holocene B5608 1966

Bagana Volcanics Czg Andesite; Undifferentiated pyroclastics and derived fan 

deposits

Pliocene? to Holocene B5612 1966

Bakanovi Volcanics Czk Andesite, tuff, agglomerate Pliocene? to Holocene B5612 1966

Taroka Volcanics Czl Andesite; Undifferentiated agglomerate, tuff, andesite (?), 

derived fan deposits

Pliocene? to Holocene B5612 1966

Billy Mitchell 

Volcanics

Czm Tuff, agglomerate, andesite (?), derived fan deposits Pliocene? to Holocene B5608, 

B5612

1966

Numa Numa Volcanics Czn Tuff, agglomerate, andesite (?) Pliocene? to Holocene B5608, 

B5612

1966

Tore Volcanics Czo Undifferentiated andesite, pyroclastics, derived fan deposits Pliocene? to Holocene B5608 1966

Reini Volcanics Czr Andesite, pyroclastics, derived fan deposits Pliocene? to Holocene B5612 1966

Takuan Volcanics Czt Undifferentiated tuff, agglomerate, andesite, derived fan 

deposits

Pliocene? to Holocene B5612 1966

Bougainville Group Czt>v Andesite and dacite Pliocene? to Holocene B5612 1966

- - Czu Andesite, basalt, dacite, agglomerate, tuff Miocene? to Pliocene? B5608, 

B5612

1966

Kieta Volcanics Tk Agglomerate, tuff; sandstone, siltstone and conglomerate 

composed of volcanic material; andesite, basalt, pillow lava

Oligocene? to early 

Miocene?

B5612 1966

Volcanic rocks on Tabar-Lihir-Tanga-Feni Islands 

- - Czv Undifferentiated volcanics Pliocene to Pleistocene A5610 1973

Quaternary volcanics Qv8, 

Qv7

Mainly volcanics. Predominantly andesitic pyroclastic rocks 

and lavas; dacites, basalts, and rhyolites

Quaternary 1:1M scale 

map 

1971
Appendix U—Tract 009pCu7207 291

Table U3. Known porphyry copper deposits in tract 009pCu7207, Outer Melanesian Arc I—Papua New Guinea.

[Ma, million years; Mt, million metric tons; t, metric ton; g/t, gram per metric ton; Cu-Mo subtype, deposits that have Au/Mo ratios <3 or average Mo grades 

>0.03%; Cu-Au subtype, deposits that have Au/Mo ratios >30 or average Au grades >0.2 g/t; NA, not applicable; n.d., no data. Contained Cu in metric tons is 

computed as tonnage (Mt × 1,000,000) × Cu grade (%)]

Name Latitude Longitude Subtype Age 

(Ma)

Tonnage 

(Mt)

Grade 

Contained 

Cu (t) Cu Reference

(%)

Mo 

(%)

Au

(g/t)

Ag

(g/t)

A. Manus Island

Arie -2.047 146.870 NA 15 165 0.32 n.d. 0.10 1.70 528,000 ACA Howe International Limited (2010), 

Anonymous (1978), Jaques and Webb 

(1975), Mason and McDonald (1978), 

Rogerson and McKee (1990), Rogerson 

and others (1986)

D. Bougainville

Panguna

-6.318 155.493 Cu-Au 3 1,420 0.47 0.005 0.57 1.1 6,603,000 Andrew (1995), Baldwin and others 

(1978), Clark (1987, 1990), Eastoe (1978), 

Ford (1978), Fountain (1972), Mining 

Journal (2009), Page and McDougall 

(1972), Tarkian and Stribrny (1999) 
292 Porphyry Copper Assessment of Southeast Asia and Melanesia 

Table U4. Significant prospects and occurrences, tract 009pCu7207, Outer Melanesian Arc I—Papua New Guinea.

[Ma, million years. Rank 4=Prospect listed in global database of Singer and others (2008) or <16,000 t of ore established by drilling. Rank 3=drilled, with >20 

m of 0.2% or more Cu. Rank 2=drilled or trenched with < 20 m of 0.2% Cu or <0.2% Cu, or past or ongoing exploration. Rank 1=copper occurrence that may 

be related to porphyry-type mineralization based on stream sediment or magnetic anomaly or location along structural trend. n.d., no data; %, percent; g/t, grams 

per metric ton; km, kilometers, m, meters. Names listed in italics are known epithermal gold deposits that are included because they have indications of associated porphyry-style mineralization]

Name Latitude Longitude Ag

 (Ma) Comments Reference Rank

A. Manus Island

Mount Kren -2.116 146.95 13.5 Trench samples:120 m at 0.12% Cu 

including 25 m at 0.3%; rock chip assay 

≤0.6 g/t Au and ≤2.5% Cu. 

Jaques and Webb (1975), Mason 

and McDonald (1978), Rogerson 

and McKee (1990), Rogerson and 

others (1986), Triple Plate Junction 

Plc. (2006), Singer and others 

(2008)

4

Aniwea -2.091 146.873 n.d. Cu prospect. Mineral Resources Authority of 

Papua New Guinea (2002)

1

Wytar -2.102 146.926 n.d. Cu prospect. Mineral Resources Authority of 

Papua New Guinea (2002)

1

Njekel -2.156 146.997 n.d. Cu prospect, epithermal Au prospect; 

defined by multi-element drainage 

anomalies.

Mineral Resources Authority of 

Papua New Guinea (2002), Triple 

Plate Junction Plc. (2006)

1

Wamatja -2.161 147.03 n.d. Cu prospect. Mineral Resources Authority of 

Papua New Guinea (2002)

1

Manus Island gold/

copper project

-2.16 146.969 n.d. Exploration project along 12 km belt of 

prospects targeting a porphyry copperepithermal gold system defined by Mt. 

Kren Kren(Cu)-Njekel-Kisi (Au) -and 

East Worei prospects.

Pacrim Energy Limited (2009) 2

B. New Ireland Island

Legusulum (West Lihir 

copper-gold project)

-3.184 151.654 24 Oligocene-Miocene Lemau dioritic 

intrusive complex.

MIL Resources, Ltd. (2008); 

Singer and others (2008)

4

New Hanover -2.622 150.142 n.d. Reconnaissance exploration identified 

Cu-bearing breccias associated with 

epithermal gold target areas. Feldspar 

porphyry intrusion with quartz-sulfidecarbonate stockwork at core of 19 

km2

 area of argillic alteration. Cu in 

brecciated quartz veins and in narrow 

intercepts in drillcore in oxide zone 

epithermal Au target. 

Papuan Precious Metals (2011) 1

Palabong copper/gold 

project

-3.98 152.599 n.d. Porphyry copper-gold and epithermal 

gold exploration target area. 

MIL Resources, Ltd. (2008), Titan 

Metals Limited (2008)

2
Appendix U—Tract 009pCu7207 293

Table U4. Significant prospects and occurrences, tract 009pCu7207, Outer Melanesian Arc I—Papua New Guinea.—Continued

Name Latitude Longitude Age

(Ma) Comments Reference Rank

B. New Ireland Island

Weitin River copper/

gold project

-4.397 152.9 n.d. Weitin River Caldera is a large circular structure 

approximately 5 km in diameter; anomalous 

stream sediment copper geochemistry with 

samples assaying 35 to 200 ppm copper.

MIL Resources, Ltd. (2008), 

Titan Metals Limited (2008)

2

New Ireland - 

unworked deposit 1

-3.388 151.977 n.d. Unworked copper deposit~ 30 km SE of 

Legusulum, as noted in MRA database.

Mineral Resources Authority 

of Papua New Guinea (2002)

1

New Ireland - 

unworked deposit 2

-3.341 151.888 n.d. Unworked copper deposit~ 40 km SE of 

Legusulum, as noted in MRA database.

Mineral Resources Authority 

of Papua New Guinea (2002)

1

C. Tabar-Lihir-Tanga-Feni-Islands

Feni (Kabang) -4.067 153.633 n.d. Epithermal Au prospect may be overprinting 

porphyry copper-gold.

PACCOM Ventures (2003) 1

Ladolam (Lihir 

Island)

-3.313 152.633 n.d. Epithermal gold deposit in an inactive volcanic 

crater (active mine). Early stage porphyry 

possibly related to very low-grade porphyry 

copper style mineralization. 

LGL Gold (2009), Corbett 

and Leach (1998), Müller 

and others (2003)

1

Tatua gold/copper 

project

-2.82 151.94 n.d. Gold and copper exploration within collapsed 

calderas.

Allied Gold Limited (2009) 1

Simberi (Tabar 

Island)

-2.631 152.002 n.d. Epithermal gold deposits; gold produced 

starting in 2008 from an open pit mine in oxide 

zone ores; ongoing exploration includes drilling 

at the Pigibo and Pigiput prospects.

Allied Gold Limited (2009) 1

Tabar Island -2.817 151.967 n.d. Gold and copper exploration within collapsed 

calderas.

Allied Gold Limited (2009) 1
294 Porphyry Copper Assessment of Southeast Asia and Melanesia 

D. Bougainville Island.—Bougainville consists of a 

northwest-trending zone of Neogene and Paleogene sedimentary rocks intruded by Neogene and Quaternary felsic to 

intermediate plugs. Mafic volcanic rocks on the northern and 

southern parts of the island locally are covered by Quaternary sediments. The area around the Bougainville porphyry 

copper mineralized zone contains breccia, diorite, feldspar 

porphyry, granodiorite, quartz diorite, and volcanic rocks 

consisting of basalt, dacite, and andesite. Late Cenozoic sediments are grits and limestones (Fountain, 1972; Baldwin and 

others, 1978). Age of mineralization is Pliocene (Page and 

McDougall, 1972).

Known Deposits

A. Manus Island.—The 15 Ma Arie porphyry copper deposit (165 Mt at 0.32 wt. percent copper) is hosted in 

breccia and porphyritic diorite (Singer and others, 2008). 

Resources are based on drilling by Kennecott in the 1980s and 

are not compliant with modern NI43-101 reporting criteria. 

The 13.5 Ma Mount Kren prospect, located about 12 km 

southeast of Arie (fig. U1), has a noncompliant estimated 

resource of 20 Mt at 0.3 percent copper, based on drilling in 

the 1970s. The team includes Arie as a known deposit because 

it was included in the porphyry copper grade and tonnage 

model used for the assessment (Singer and others, 2008). The 

historical data should be considered preliminary pending outcomes of current exploration on Manus Island.

D. Bougainville.—The Panguna (Bougainville) mine 

produced 2 percent of world copper supply at one time. The 

mine operated from 1972 until 1989 when political unrest 

caused a shutdown. Panguna is interpreted as part of a stratovolcano, where the Panguna Andesite was intruded by the 

Kaverong Quartz Diorite and related differentiates (granodiorite, breccias). The 3.4 Ma Panguna (Bougainville) porphyry 

copper-gold deposit lies in the south central part of Bougainville Island. Ore minerals are present in quartz veinlets and as 

disseminations of bornite, chalcopyrite, galena, gold, molybdenite, and sphalerite; stannite and tetrahedrite/tennantite also 

are reported. Supergene ore minerals include chalcocite and 

covellite, along with iron-oxide minerals (Baldwin and others, 

1978; Clark, 1990; Tarkian and Stribrny, 1999). Mill concentrate from the mine contained up to 8 ppb platinum and 40–52 

ppb palladium. Grade and tonnage for the deposit in the database of Singer and others (2008) are cited as 1,420 Mt at 0.465 

percent copper, 0.005 percent molybdenum, and 0.57 g/t gold. 

The mine produced 3 Mt of copper and 9.3 million ounces of 

gold from 675 Mt of milled ore during the 18 years of mine 

operation. At closure, ore reserves were cited as 497 Mt at 0.42 

percent copper and 0.55 g/t gold, with additional material that 

could be upgraded to 691 Mt of mill feed at 0.40 percent copper and 0.47 g/t gold (Bougainville Copper Limited, 2009). In 

preparation for reopening the mine, an updated total resource 

(indicated and inferred) was estimated based on historical data: 

1,064 Mt at 0.33 percent copper and 0.37 g/t gold (Bougainville Copper Limited, 2009). In 2010, efforts were underway 

between the Boungainville government, the government of 

Papua New Guinea, and landowners to resolve issues related to 

the future of the mine, including lifting a moratorium on new 

exploration and mining (Bougainville Copper Limited, 2011).

Prospects, Mineral Occurrences, and Related 

Deposit Types

A. Manus Island.—Pacrim’s Manus Island project targeted 

a 12-km-long belt of prospects that include the Mount Kren 

copper prospect, as well as epithermal gold targets (Njekel, Kisi 

and East Worei). Soil copper anomalies at Mount Kren overlie 

rock where rock-chip sampling confirmed a 600-m-long shallow dipping zone of anomalous copper (0.12–0.3 percent and 

up to 0.22 g/t gold). Ore minerals are veinlets and disseminations of bornite, chalcopyrite, molybdenite, and gold, accompanied by pyrite, gold, zeolite and sulfur. Minor gold, silver, 

and molybdenum values are reported in the ores. Supergene 

assemblages contain alunite and kaolinite. Alteration minerals 

associated with the Arie and Mount Kren porphyry systems 

include biotite, sericite, chlorite, carbonate minerals, epidote, 

magnetite, and kaolinite. The entire tract area in central Manus 

is under exploration for high-sulfidation epithermal deposits, 

deeper-seated porphyry systems, and low-sulfidation epithermal 

veins and limestone replacements (ACA Howe International 

Limited, 2010).

B. New Ireland Island.—The West Lihir exploration target 

is the Legusulum porphyry copper prospect, a prominent diorite 

ridge covering an area of more than 1 km2

, with reported chalcopyrite, bornite, chalcocite and molybdenite and a 70-m-thick 

leached cap overlying the deposit (Titan Metals Limited, 2008). 

Other prospect areas under exploration for porphyry copper-gold 

and epithermal gold deposits on New Ireland include Palabong 

and Weitin River, a caldera structure with geochemical anomalies for copper (MIL Resources, Ltd., 2010).

C. Tabar-Lihir-Tanga-Feni Islands.—Alluvial gold was 

worked by artisanal mining, mainly before World War II. The 

area was explored for porphyry copper deposits in the 1970s and 

1980s, which led to the discovery of the world-class Ladolam 

deposit on Lihir Island. Ladolam is an epithermal gold deposit 

with total ore reserves of 330.8 Mt at 2.71 g/t gold (LGL Gold, 

2009). The Ladolam gold deposit on Lihir Island is developed 

in the floor of the alkaline Luise Caldera, where sector collapse 

at 0.3 Ma resulted in telescoping of the hydrothermal system 

and superposition of an epithermal gold system on early stage, 

weak porphyry gold-copper mineralization (Müller and others, 

2003). Ladolam has been described as an atypical gold deposit 

related to alkaline rocks formed in a postsubduction extensional 

setting (Sillitoe, 2002). Ladolam is the youngest (<1 Ma) known 

intrusion-related gold deposit and the first documented example 

of a low-sulfidation epithermal system triggered by sector collapse of a volcano that overprints a pre-collapse porphyry 

system (Sillitoe, 2002). Gold is mined from an epithermal 

deposit on Simberi in the northernmost Tabar Islands.
 Appendix U—Tract 009pCu7207 295

Exploration History

Prospecting on Manus Island led to the discovery and 

development of Arie and Mount Kren. A digital compilation of 

historical exploration data for Manus Island was compiled as 

part of a World Bank project for the Papua New Guinea Department of Mining and released in 2003 (Beams and Jenkins, 2003). 

The data set includes more than 30,000 records of stream-sediment, rock-chip, soil, and drill data and provides an inventory of 

tenements held and related exploration activities. As of 2008, the 

permissive-tract area was under active exploration license (Mineral Resources Authority of Papua New Guinea, 2008). Pacrim/

Triple Plate PLC remapped the central Manus region, reinterpreted geophysical data, identified structural controls on mineralization, identified epithermal mineralization associated with 

porphyry copper mineralization, and performed detailed studies 

at the Kisi epithermal gold prospect, and at the Kren, Njekei, and 

East Worei prospects in the southern part of the island (Pacrim 

Energy Limited, 2009; ACA Howe International Limited, 2010). 

In 2010, Manus Island exploration was in progress through a 

joint venture between Triple Plate Junction PLC and Newcrest 

Mining Limited, subject to approval by the Papua New Guinea 

government (Newcrest Mining Limited, 2010).

Swiss Aluminium Mining Australia explored the New 

Ireland area in the 1970s, using shallow drilling into the limonite 

cap at Legusulum. ESSO flew airborne magnetics in the early 

1980s and determined that Legusulum may contain significant 

copper mineralization. Exploration targets include breccia pipes 

and porphyry deposits under recent volcanic cover and limestone 

(Titan Metals, 2008).

Exploration for porphyry copper deposits in the TabarLihir-Tanga-Feni island chain in the 1970s and 1980s led to the 

discovery of the world-class Ladolam deposit. That 1982 discovery sparked exploration for epithermal gold and related deposit 

types associated with the eroded calderas that comprise the 

chain. Ongoing drilling to characterize epithermal gold mineralization at the prospects on Simberi Island, the northernmost of 

the Tabar Islands, identified copper (~170 ppm) associated with 

gold and arsenian pyrite; host rocks are tuffs and a porphyritic 

intermediate intrusive. No exploration or mining has occurred on 

Bougainville since 1989 because of limitations on site access.

Sources of Information

Principal sources of information used by the assessment 

team for delineation of 009pCu7207 are listed in table U5.

Grade and Tonnage Model Selection

Panguna is a copper-gold porphyry (Au/Mo ratio >30). 

Gold and molybdenum grades are not reported for the Arie 

deposit. T-tests for tonnage and copper for both deposits are 

compatible with either a general or Cu-Au subtype (table 6). 

Exploration activities are targeting copper-gold porphyry deposits and epithermal gold systems. On the basis of Panguna, the 

island-arc setting, and the regional characteristics of porphyry 

deposits, the copper-gold subtype grade and tonnage model was 

selected for this assessment.

Estimate of the Number of Undiscovered Deposits

Rationale for the Estimate

The team concluded that data for the Mount Kren 

prospect and additional exploration areas on Manus Island 

supported an estimate for at least one undiscovered deposit 

on the island, in addition to the Arie deposit. On New 

Ireland, the Legusulum porphyry copper-gold prospect and 

the association of copper with epithermal gold systems 

indicates porphyry copper potential, perhaps at depth below 

associated epithermal systems. Similarly, porphyry systems 

may be associated with collapsed calderas that host epithermal gold in the islands of the Bismarck Archipelago. 

Although Bougainville has not been explored for many 

years, the presence of permissive rocks and its location 

between prospective areas in New Ireland to the north, and 

in the Solomon Islands to the south, suggest that undiscovered deposits may be present. Recognition of porphyritic 

intrusions within the predominantly volcanic terrane suggests that levels of erosion may be appropriate to preserve 

porphyry copper deposits.

The team estimated a 90-percent chance of at least two 

undiscovered deposits, a 50-percent chance of five or more 

deposits, and a 10-percent chance of 10 or more based on 

the data in table U4 and the recent resurgence in exploration 

activity. The mean number of deposits based on these estimates is 5.5, with a coefficient of variation of 54 percent (table 

U6). That is, about a third of the 16 prospect areas listed in 

table U4, as well as areas that are yet to be identified through 

exploration, might represent undiscovered deposits. The team 

considered the fact that the area was underexplored for many 

years, and that new drilling to confirm previously identified 

geochemical anomalies and geophysical targets is likely to 

document new resources comparable to those in the grade and 

tonnage model, although the shallow, gold-rich epithermal 

parts of any porphyry systems are most likely to be developed 

in the foreseeable future.

Probabilistic Assessment Simulation 

Results

Undiscovered resources for the tract were estimated by 

combining consensus estimates for numbers of undiscovered 
296 Porphyry Copper Assessment of Southeast Asia and Melanesia 

Table U6. Undiscovered deposit estimates, deposit numbers, tract area, and deposit density for tract 009pCu7207, Outer Melanesian 

Arc I—Papua New Guinea.

[NXX, estimated number of deposits associated with the xxth percentile; Nund, expected number of undiscovered deposits; s, standard deviation; Cv%, coefficient of 

variance; Nknown, number of known deposits in the tract that are included in the grade and tonnage model; Ntotal, total of expected number of deposits plus known 

deposits; km2, area of permissive tract in square kilometers; Ntotal/100k km2, deposit density reported as the total number of deposits per 100,000 km2. Nund, s, and 

Cv% are calculated using a regression equation (Singer and Menzie, 2005)]

Consensus undiscovered deposit estimates Summary statistics Tract

area

(km2

)

Deposit density 

(Ntotal/100k km2

)

N90 N50 N10 N05 N01 Nund s Cv% Nknown Ntotal

2 5 10 10 10 5.5 3 54 2 7.5 16,830 45

Table U5. Principal sources of information used for tract 009pCu7207, Outer Melanesian Arc I—Papua New Guinea.

[NA, not applicable; CCOP, Coordinating Committee for Geoscience Programmes in East and Southeast Asia]

Theme Map or title Scale Citation

Geology Digital geologic map of East and Southeast 

Asia

1:2,000,000 CCOP and Geological Survey of Japan (1997)

Geology of Papua New Guinea 1:1,000,000 Bain and others (1972)

Digital geology of Papua New Guinea 1:250,000 Mineral Resources Authority of Papua New Guinea (2002)

SE Asia Radiometric Ages: GIS Database NA Malaihollo and others (2002)

Mineral 

occurrences

Porphyry copper deposits of the world: 

database, map, and grade and tonnage models

NA Singer and others (2008)

Geology of the mineral deposits of Australia 

and Papua New Guinea

1;35,000,000 Hughes (1990)

Mineral deposits of Papua New Guinea 1:2,500,000 Granger (1973)

Mineral resources on-line spatial data NA U.S. Geological Survey (2010)

Digital geology of Papua New Guinea (mineral 

occurrence point file)

1:250,000 Mineral Resources Authority of Papua New Guinea (2002)

Exploration Company Web sites NA Various (see table U4)

Papua New Guinea Mineral Resources 

Authority reports and tenement map, 

exploration reviews

Mineral Resources Authorityof Papua New Guinea (2008), 

Legge (1999) 

CCOP country report Dulcie Saroa (oral commun., 2010)

porphyry copper deposits with the global porphyry coppergold subtype model of Singer and others (2008) using the 

EMINERS program (Root and others, 1992; Bawiec and 

Spanski, 2012; Duval, 2012). Selected output parameters 

are reported in table U7. Results of the Monte Carlo 

simulation are presented as a cumulative frequency plot 

(fig. U3). The cumulative frequency plot shows the 

estimated resource amounts associated with cumulative 

probabilities of occurrence, as well as the mean, for each 

commodity and for total mineralized rock. The mean amount 

of copper contained in undiscovered porphyry copper 

deposits within the tract (17 Mt) represents about 2.4 times 

the amount of copper reported in identified resources within 

the tract (~7 Mt).
Appendix U—Tract 009pCu7207 297

Baldwin, J.T., Swain, H.D., and Clark, G.H., 1978, Geology 

and grade distribution of the Panguna porphyry copper 

deposit, Bougainville, Papua New Guinea: Economic 

Geology, v. 73, p. 690–702.

Beams, S.D., and Jenkins, D.R., 2003, Open file data from 

Manus Island, Papua New Guinea: Data release prepared 

by Terra Search Pty, Ltd., for PNG Department of Mining, 

March 2003, 53 p.

Berger, B.R., Ayuso, R.A., Wynn, J.C., and Seal, R.R., 

2008, Preliminary model of porphyry copper deposits: 

U.S. Geological Survey Open-File Report 2008–1321, 

55 p., accessed May 15, 2010, at http://pubs.usgs.gov/

of/2008/1321.

Bougainville Copper Limited, 2009, Boungainville 

Copper Limited announces a mineral resource of over 1 

billion tones at Panguna: Bougainville Copper Limited 

press release, accessed March 1, 2011, at http://www.

bougainvillecopper.com.pg/Mineral%20Resource%20

Press%20Release%2002-09.pdf.

Bougainville Copper Limited, 2011, Company Web site: 

accessed March 1, 2011, at http://www.bougainvillecopper.

com.pg/index.htm.

Clark, G.H., 1987, Geology and resource estimation at the 

Panguna porphyry copper/gold mine, Papua New Guinea: 

Proceedings of Pacific Rim Congress 87, Australasian 

Institute of Mining and Metallurgy, p. 549–556.

Clark, G.H., 1990, Panguna copper-gold deposit, in Hughes, 

F.E., ed., Geology of the mineral deposits of Australia and 

Papua New Guinea: Melbourne, Australasian Institute of 

Mining and Metallurgy Monograph 14, p. 1807–1816.

Table U7. Results of Monte Carlo simulations of undiscovered resources for tract 009pCu7207, Outer Melanesian Arc I—Papua New 

Guinea.

[Cu, copper; Mo, molybdenum; Au, gold; and Ag, silver; in metric tons; Rock, in million metric tons]

Material

Probability of at least the indicated amount based on the Cu-Au subtype model Probability of

0.95 0.9 0.5 0.1 0.05 Mean Mean or greater None

Cu 260,000 1,200,000 9,800,000 42,000,000 61,000,000 17,000,000 0.32 0.04

Mo 0 0 27,000 260,000 470,000 95,000 0.25 0.19

Au 26 110 830 3,000 3,900 1,200 0.35 0.04

Ag 0 0 2,000 13,000 27,000 5,400 0.23 0.12

Rock 59 290 2,100 8,800 12,000 3,400 0.34 0.04

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porphyry copper deposit, Bougainville, Papua New Guinea: 

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copper intrusives from Manus Island, Papua New Guinea: 

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McPhee, D.K., Seal, R.R., Taylor, R.D., and Vikre, P.G., 

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Appendix U—Tract 009pCu7207 299

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current%20el%20map.pdf.

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usgs.gov/.
148° E 152° E 156° E 2° S 6° S PAPUA NEW GUINEA Arie Wytar Njekel Aniwea Wamatja Panguna Tabar Island Feni (Kabang) Simberi (Tabar Island) Ladolam Tatua gold/copper project Palabong copper/gold project Weitin River copper/gold project New Ireland - unworked deposit 2 New Ireland - unworked deposit 1 Legusulum (West Lihir copper-gold project) Mount Kren Manus Island gold/copper project New Hanover PACIFIC OCEAN Solomon Sea Bismarck Sea New Guinea Island Manus Island New Ireland New Britain Bougainville AUSTRA

140°E 

0° 10°S PAC

PG 

Political boundary source: U.S. Department of State (2009) Projection: Asia South Albers Equal Area Conic; Central meridian 151° E; latitude of origin 15° S 0 100 200 KILOMETERS 0 50 100 MILES 50 150 EX

OtheAsse009p

PorpdepotractPorpprostract

Figure U1. Map showing the location, known deposits, and significant prospects and occurrences for of permissive tract 009pCu7207, Outer MeNew Guinea. PG, Papua New Guinea; SB, Solomon Islands.
Panguna

Tabar Island

Feni (Kabang)

Simberi (Tabar Island)

Ladolam (Lihir Island)

Tatua gold/copper project

Palabong copper/gold project

Weitin River copper/gold project

New Ireland - unworked deposit 2New Ireland - unworked deposit 1

Legusulum (West Lihir copper-gold project)

ArieWytar

Njekel

Aniwea

Wamatja

Mount Kren

Manus Island gold/copper project 

PAPUA NEW GUINEA PACIFIC OCEAN

 Solomon Sea Bismarck Sea

150° E 155° E

5° S

Base from ESRI ArcGIS Online (2009)World Shaded ReliefPolitical boundary source: U.S. Department of State (2009)Projection: Asia South Albers Equal Area Conic;Central meridian 150° E; latitude of origin 15° S

0 100 200 KILOMETERS

0 50 100 MILES

50 150

E

Ass 0PerPerPor

Por

New Guinea Island

Manus Island

New Ireland

New Britain

Bougainville

New Hanover

Figure U2. Map showing igneous rocks used to delineate tract 009pCu7207, Outer Melanesian Arc I— Papua New Guinea.
302 Porphyry Copper Assessment of Southeast Asia and Melanesia 

1.00

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

Probability

Mean Cu

Mean Mo

Mean Au

Mean Ag

Mean Rock

Cu

Mo

Au

Ag

Rock

Mean Cu

Mean Mo 

Mean Au

Mean Ag

Mean Rock

EXPLANATION

0.01 0.1 1 10 100 1k 10k 100k 1M 10M 100M 1B 10B 100B

Material, in metric tons

Figure U3. Cumulative frequency plot showing the results of Monte Carlo computer simulation of undiscovered 

resources in tract 009pCu7207, Outer Melanesian Arc I—Papua New Guinea. k, thousands; M, millions; B, billions; 

Tr, trillions.
Appendix V—Tract 009pCu7210 303

Appendix V. Porphyry Copper Assessment for Tract 009pCu7210, 

Outer Melanesian Arc II—Melanesia (Solomon Islands, Vanuatu, and Fiji)

By Jane M. Hammarstrom1, Connie L. Dicken1, Gilpin R. Robinson, Jr.1, and Arthur A. Bookstrom2

Deposit Type Assessed: Porphyry copper, copper-gold subtype

Descriptive model: Porphyry copper (Berger and others, 2008; John and others, 2010); Porphyry copper-gold 

(Cox, 1986; Cooke and others, 1998)

Grade and tonnage model: Porphyry copper, copper-gold subtype (Singer and others, 2008)

Table V1 summarizes selected assessment results.

Table V1. Summary of selected resource assessment results for tract 009pCu7210, Outer Melanesian Arc II—Melanesia (Solomon 

Islands, Vanuatu, and Fiji).

[km, kilometers; km2, square kilometers; t, metric tons] 

Date of 

assessment

Assessment

depth (km)

Tract area 

(km2)

Known copper 

resources (t)

Mean estimate of 

undiscovered copper 

resources (t)

Median estimate of

undiscovered copper 

resources (t)

January 2011 1 38,180 6,887,900 16,000,000 9,100,000

1

U.S. Geological Survey, Reston, Virginia, United States.

2

U.S. Geological Survey, Spokane, Washington, United States.

Location

The tract covers the central and southern portions of Melanesia, including the archipelago countries of Solomon Islands, 

Vanuatu (formerly New Hebrides), and Fiji (fig. V1). The northernmost parts of the Outer Melanesian Arc are described in tract 

009pCu7207, Outer Melanesian Arc I—Papua New Guinea, which covers the islands north of the Solomon Islands (Bougainville, New Ireland, the Bismarck archipelago, and Manus Island).

Geologic Feature Assessed

Eocene-Oligocene to late Miocene-Pliocene-Pleistocene Outer Melanesian magmatic arc and Melanesian borderlands in the 

Solomon Islands, Vanuatu, and Fiji.

Delineation of the Permissive Tract

Tectonic Setting

The Outer Melanesian Arc has a protracted history of arc development, starting with southwest-dipping subduction of the 

Pacific Plate beneath the Indo-Australian Plate along the Vitiaz-Tonga Trench system (fig. 6) by Eocene time (Schellart and 
304 Porphyry Copper Assessment of Southeast Asia and Melanesia 

others, 2006). A single semicontinuous arc system, known as 

the Vitiaz Arc, included New Ireland and Bougainville in Papua 

New Guinea, the Solomon Islands, Vanuatu, and Fiji. The Vitiaz 

Arc persisted as the Pacific Plate subducted beneath a passive 

Indo-Australian Plate margin until the Miocene. Early to middle 

Miocene collision of the Ontong Java Plateau (fig. 9) with the 

Solomon Arc segment of the Vitiaz Arc system led to a reversal in subduction polarity, initiation of eastward subduction of 

the Indo-Australian Plate along the New Britain-Cristobel and 

Vanuatu (New Hebrides) Trench systems (west of the Vitiaz Arc 

system), and subsequent fragmentation of the Vitiaz Arc. The 

1,900,000 km2 Ontong Java Plateau is an anomalously thick 

(>30 km), probably plume-related, Cretaceous oceanic plateau 

on the Pacific Plate that continues to interact with an active subduction zone as its southwestern margin subducts at the North 

Solomon Trench (fig. 6; Mann and Taira, 2004). Extensive 

offshore drilling of the Ontong Java Plateau and sampling of 

obducted plateau material in the eastern Solomon Islands along 

the southern margin of the Plateau demonstrated that plateau 

lavas are low-K tholeiitic basalts with limited compositional 

variability (Tejada and others, 2004). The plateau basalts are 

geochemically distinct from both ocean island basalts (OIB) and 

normal mid-ocean-ridge basalt (Pacific N-MORB), as indicated 

by their flat normalized incompatible element- and rare-earth 

patterns (Tejada and others, 2004). The collision of the Ontong 

Java Plateau disrupted the Vitiaz Arc system and had a profound 

effect on the tectonic setting of the region because it triggered 

reversals in subduction polarity. Such reversals may be a factor 

that controls development of some porphyry Cu-Au systems 

(Solomon, 1990).

Between 8 and 5 Ma, the Vanuatu Arc rotated clockwise 

as the North Fiji back-arc basin opened and the Fiji Platform 

rotated in a counterclockwise direction. The modern Fiji 

Platform, bordered by the Fiji Fracture Zone and the North Fiji 

Basin to the north, and the Hunter Fracture Zone to the south, 

is situated between the eastward-subduction zone that defines 

the modern eastward subducting Vanuatu Arc and the westward 

subduction zone of the Tonga-Kermadec Arc system. The modern southern part of the Melanesian Arc system is a collage of 

microplates (North Fiji, Solomon Sea, Bismarck, and Woodlark 

Basins) and trenches (San Cristobal-Vanuatu, Vitiaz, Tonga) 

along the boundary zone between the Australian and Pacific 

Plates (fig. 6).

Tract Segments

On the basis of the vast extent of the now-segmented Outer 

Melanesian Arc, the assessment team subdivided the tract into 

three segments to facilitate discussion: Solomon Islands, Vanuatu, 

and Fiji. The probabilistic assessment applies to the whole tract.

Solomon Islands

About 1,000 islands comprise the independent nation of 

Solomon Islands and have a land mass of approximately 

28,400 km2

. The islands trend northwest-southeast from the 

Shortland Islands and the island of Choiseul, just south of 

Bougainville, Papua New Guinea, to the island of Makira (fig. 

V2A). The Solomon Islands represent a collage of “terrains”3

formed in an intra-oceanic arc setting since the Cretaceous 

(Petterson and others, 1999). Building on the framework for the 

Solomon Arc developed by Coleman (1962, 1980) and Coleman 

and Kroenke (1981), Petterson and others (1999) constructed a 

terrain map of the Solomon Islands which defined five crustal 

units based on lithology, age, geochemistry of basement, and 

presence or absence of arcs (fig. V2A). Permissive terrains for 

porphyry copper deposits preserve Paleocene/Eocene to early 

Miocene (stage 1) arc volcanism related to southwest-directed 

subduction of the Pacific Plate along the Vitiaz Trench and (or) 

late Miocene to Holocene (stage 2) volcanism and plutonism. 

Stage 2 magmatism is related to northeast-directed subduction 

of the Australian Plate beneath the Solomon block. During stage 

2, the San Cristobel Trench developed following the polarity 

reversal initiated by docking of the Ontong Java plateau. Both 

arc stages are preserved in the South Solomon MORB Terrain 

on Guadalcanal and Choiseul; stage 2 arc magmatism formed 

the New Georgia Terrain, and stage 2 rocks also occur in the 

Shortland Islands, Choiseul, Guadalcanal, and in some of the 

smaller islands of the archipelago (fig. V2A). Stage 1 arc activity formed the basement of the Central Solomon terrain, which 

has variable development of stage 2 arc (Petterson and others, 

1999). Stage 1 arc assemblages include ultramafic rocks, basic 

to ultrabasic island-arc basalts, back-arc basalts, and alkali 

basalts, as well as calc-alkaline andesites and dacites. Stage 

2 arc assemblages include late Miocene calc-alkaline basaltrhyolite rocks, sodic basalt-dacite, shoshonitic rocks, high-Mg 

basalt-andesite, picrites, diorite, and microgranites related to 

northeast-directed subduction of the Australian Plate. These 

rocks form the New Georgia Group and also occur in the Shortland Islands, on Choiseul, and on Guadalcanal.

Vanuatu (New Hebrides)

The Republic of Vanuatu, known as the New Hebrides 

prior to independence in 1980, is a y-shaped archipelago composed of 83 island groups that trend north-south for a distance 

of 1,300 km, with a total land area of about 12,500 km2 (fig. 

V2B). Vanuatu lies 800 km west-southwest of Fiji and 500 

km northeast of New Caledonia. The main islands are Espiritu 

Santo, Malekula, Efate, and Erromango.

Vanuatu is described as an island-arc ridge composed of 

three parallel belts (Macfarlane and others, 1988). The western 

belt is composed of late Oligocene to middle Miocene volcanic 

rocks that formed part of the relict Vitiaz Arc prior to subduction reversal (fig. 9). The volcanic rocks, up to 7,000 m thick, 

were uplifted, deformed, and intruded by calc-alkaline mafic to 

intermediate intrusions associated with northeast-striking faults 

(Vanuatu Department of Geology, Mines, and Water Resources, 

3

Petterson and others (1999) proposed the term “terrain” to describe the geodynamic framework of the Solomon Islands. Terrains are distinguished from one 

another based on geology, tectonic history, and age. The term “terrane” sensu 

stricto refers to fault-bounded areas that have unique geological histories.
Appendix V—Tract 009pCu7210 305

1995). The deep trenches that characterize the North and South 

Vanuatu (New Hebrides) Trench are absent in the parts of the 

arc adjacent to the western belt, where Pliocene onset of collision of the d’Entrecasteaux ridge (on the Indo-Australian 

Plate) with the Vanuatu Arc caused rapid uplift and tilting on 

Espiritu Santo and Malekula (Collot and Fisher, 1991). This 

uplift may have exposed the upper parts of porphyry systems.

The central belt of Vanuatu, active since the late Miocene 

subduction reversal, hosts 11 major volcanoes. Volcanic-rock 

compositions are mafic and highly variable, ranging from 

low-K tholeiites to high-K alkaline rocks, including high-K picrites and ankaramites (Vanuatu Department of Geology, Mines, 

and Water Resources, 1995). The late Miocene to early Pliocene 

eastern belt of Vanuatu is composed of submarine basaltic to 

andesitic volcanic and volcaniclastic rocks, unconformably 

deposited on tilted, block-faulted Miocene volcanic rocks. 

Obduction of ophiolite complexes accompanied late Pliocene 

uplift and erosion; rapid (2.7 mm/yr) Pleistocene uplift led to 

development of coral reef terraces (Vanuatu Department of 

Geology, Mines, and Water Resources, 1995). Permissive rocks 

and known prospects for porphyry copper deposits are confined 

to the western belt of Vanuatu.

Fiji

The island nation of Fiji, about 2,000 km northeast of 

the North Island of New Zealand, is an archipelago of more 

than 300 islands with a total land area of 18,300 km2. Fiji is 

situated on the Lau Ridge between the opposing Vanuatu and 

Tonga-Kermadec convergence zones and is bordered by the 

extensional Lau and North Fiji back-arc basins (figs. 6, 8). The 

geology of the Fiji islands preserves a record of the growth, 

evolution, and fragmentation of an island-arc system (Fiji 

Ministry of Lands and Mineral Resources, 2010). The evolution of Fiji is characterized by 4 stages: (1) early arc stage 

(35–12 Ma) characterized by primitive, low-K thloeiites with 

pre-Miocene volcanism associated with subduction along the 

Vitiaz Trench; (2) mature arc stage (12–7 Ma) represented by 

the Colo Plutonic Suite, which is referred to as the Tholo Suite 

in some references; (3) early arc rifting stage (7–3 Ma) associated with tholeiitic to calc-alkalic rocks; and (4) late arc rifting 

stage (3 Ma to Holocene), associated with ocean-island basalts 

and on some islands, high-K andesites. Porphyry systems are 

associated with the mature arc and early extensional (rifting) 

stages (Colley and Greenbaum, 1980; Fiji Ministry of Lands 

and Mineral Resources, 2010). Epithermal gold-telluride systems, such as the Emperor deposit, are associated with calderas 

of the early rifting stage (Fiji Ministry of Lands and Mineral 

Resources, 2010).

Calc-alkaline rocks permissive for porphyry copper deposits occur on the two main islands: Viti Levu and Vanua Levu 

(fig. V2C). Ages range from 12.5 Ma to about 7 Ma. The main 

plutons of the Colo (Tholo) Suite are tonalite and gabbro, with 

marginal facies, including trondhjemite, diorite, and hornblende 

andesite-microdiorite; coeval volcanic rocks are absent. Colley 

and Greenbaum (1980) noted 7 porphyry-type copper ±molybdenum prospects associated with plutons of the Colo (Tholo) 

orogeny, as well as copper skarns; no economic deposits are 

associated with these rocks. The Yavuna stock in western Viti 

Levu, dated at 33 Ma, and the Mbotenaulu stock in central Viti 

Levu are mapped as first phase, pre-Miocene, synorogenic 

intrusions of the Colo (Tholo) plutonic suite, whereas the other 

plutons of the Colo (Tholo) suite are mapped as second-phase, 

late Miocene (7–11 Ma) synorogenic intrusions.

Major porphyry copper and epithermal gold deposits are 

associated with mature arc (12–7 Ma) and early rifting stage 

(~7–3 Ma) tholeiitic to calc-alkaline rocks on Viti Levu and 

Vanua Levu. The early rifting stage produced the Namosi 

Andesite, which covers much of southeastern Viti Levu; these 

rocks are associated with the porphyry copper, skarn, and 

epithermal-vein systems in the Namosi district.

Geologic Criteria

Permissive rocks for porphyry copper deposits include 

late Eocene-early Miocene island-arc volcanic rocks and 

intrusions related to the Vitiaz Arc, as well as late MiocenePliocene-Pleistocene rocks associated with post-collision 

arc magmatism and subduction reversal (stage 1 and 2 arcs 

of Petterson and others, 1999). Igneous rock ages are not 

well-constrained throughout the Melanesian islands. Calcalkaline to alkaline intrusive and extrusive igneous rocks that 

are permissive for porphyry copper deposits are associated 

with both early and late phases of arc evolution. On Guadalcanal in the Solomon Islands, the Poha and Mbetilonga 

porphyry copper prospects are associated with Oligocene 

diorite-tonalite-andesite complexes; the Koloula porphyry 

copper deposit and epithermal gold prospects are associated with the Pliocene-Pleistocene Koloula Igneous Complex (mainly quartz diorite, tonalite, andesite) and eroded 

calderas. Permissive rocks on Vanuatu are confined to the 

western belt of the archipelago, where late Miocene diorite, 

microdiorite, and andesite stocks intrude Miocene volcanic 

rocks. In Fiji, porphyry-type prospects are associated with 

orogenic and post-orogenic magmatism on Viti Levu and 

with post-orogenic magmatism on Vanua Levu (Colley and 

Greenbaum, 1980).

The 2,700-km-long southeast-trending archipelagos that 

comprise the fragmented, Paleogene-Neogene Outer Melanesian Arc system south of Papua New Guinea are delineated 

as a single permissive tract for several reasons: (1) both early 

and late stages of arc evolution are preserved in close spatial 

proximity on some islands, (2) insufficient age information 

is available to subdivide the tract by age, (3) dioritic intrusions and andesitic volcanic rocks permissive for porphyry 

copper deposits occur throughout the evolution of the arc, 

(4) the likelihood of occurrence of undiscovered porphyry 

copper deposits is uniform throughout the tract area, and (5) 

the availability and quality of geologic mapping and mineral occurrence data is consistent throughout the study area. 

Because of the large extent of the tract, the arc is discussed 

in three segments: Solomon Islands, Vanuatu, and Fiji.
306 Porphyry Copper Assessment of Southeast Asia and Melanesia

A preliminary permissive tract was delineated by compiling a master digital geology file of igneous rocks in a GIS. 

Source data included digital geologic data at 1:1,000,000 for 

the Solomon Islands and 1:250,000-scale data for the two 

main islands of Fiji, Viti Levu and Vanua Levu. Selected map 

units were digitized from georectified paper maps of islands 

within the Solomon and Vanuatu (New Hebrides) Archipelagos at scales ranging from 1:250,000 to 1:100,000. Detailed 

geologic map coverage is not available for all islands; where 

available, the more detailed maps were consulted and the units 

represented on those maps are listed in table V2. Each map 

unit was attributed by source, age, and lithology and coded as 

“permissive_extrusive” or “permissive_intrusive.”

Permissive igneous rocks are present on islands that host 

Eocene-early Miocene stage 1 and (or) late Miocene-Pleistocene stage 2 island-arc rocks in the Solomon Islands (Petterson and others,1999) and in the late Oligocene to middle 

Miocene volcanic complexes of the western belt of Vanuatu 

(Mitchell and Warden, 1971).

In the Shortland Islands in the northernmost Solomon 

Islands, an older late Oligocene to early Miocene tholeiitic 

basement sequence is intruded by younger (probably pre-Pliocene) small calc-alkaline intrusions. These include the Tuana 

Microdiorite, Fauro Dacite, and Hisiai Complex (Turner and 

Ridgway, 1982).

In Vanuatu, igneous ages are not well-constrained; however, the igneous rocks of the western belt islands are mainly 

Miocene in age (Macfarlane and others, 1988). The oldest 

igneous rocks (possibly as old as 37–39 Ma) are reportedly 

the andesites on the Torres Islands; three early to early middle 

Miocene intrusive episodes are recognized on Espiritu Santo; 

and quartz diorite and microdiorite intrusions in northern 

Malekula have been dated at 20–14 Ma.

Permissive rocks in Fiji include 35–7 Ma pre- and synColo (Tholo) orogeny tholeiitic and calc-alkaline rocks and 

7–3 Ma post-orogenic rift-related alkaline and shoshonitic 

rocks. Synorogenic, elongate, tonalite-trondhjemite intrusions 

core anticlines formed during the late Miocene Tholo orogeny. 

Post-orogenic calc-alkaline volcanic rocks include the Namosi 

Andesite, Vatia Andesite, and Navosa Group, as well as alkaline/shoshonitic Plio-Pleistocene volcanic centers.

The tract excludes map units designated as nonpermissive 

for porphyry copper deposits [oceanic basement rocks, pillow 

basalts, ophiolite complexes, and oceanic basalts, such as 

occur on the easternmost Solomon Islands and in the central, 

active volcanic, and eastern block-faulted volcanic (>1,000 

m thick) and ophiolite complexes of Vanuatu]. Many of the 

islands include sequences of mixed volcaniclastic-sandstonelimestone units that exceed 1,000 m in thickness. These cover 

rocks are excluded from the permissive tract because porphyry 

copper deposits are unlikely to be preserved within 1 km of 

the surface. Map units included as permissive rocks are listed 

in table V2.

Modern, reduced-to-pole aeromagnetic data are available 

for parts of western Vanuatu. Preliminary results were interpreted by the Vanuatu Mineral Exploration Initiative (Vanuatu Department of Geology, Mines, and Water Resources, 

1995) as indicating the following: (1) high magnetic intensity 

associated with shallow (<500 m) and deep (>500 m) features 

correlates with mafic to intermediate complexes; (2) magnetic 

highs are associated with basalt flows, mafic dikes, and small, 

probably mafic, intrusive bodies and many of these areas are 

concealed; and (3) magmatic complexes are associated with 

northwest-trending (Malekula) to north-northwest-trending 

(Espiritu Santo) fracture and fault zones. A 1:1,000,000 pagesize map of total magnetic intensity of south Espiritu Santo 

and Malekula was georectified and brought into a GIS for 

comparison with the geologic map. Most of mapped small 

intrusive bodies and prospect areas appear to coincide with 

magnetic low areas rather than magnetic highs. The texture 

of the aeromagnetic data suggests the presence of numerous 

small, circular, magnetic bodies in the shallow subsurface. 

The map-based tract boundaries were expanded to encompass 

these areas on western Espiritu Santo and Malekula.

Most of the intrusive units exposed throughout the 

Melanesian islands crop out as very small stocks, plugs, and 

dikes within andesites; some geologic maps simply indicate 

areas within volcaniclastic breccia-sedimentary units that 

contain abundant andesitic intrusions. Cross sections show the 

form of the many stocks as steep-sided, vertically extensive, 

pencil-shaped bodies. Intrusions in Malekula and western 

Espiritu Santo in Vanuatu are porphyritic. The final permissive tract was defined by using GIS tools to add a 2-km buffer 

around permissive extrusive map unit boundaries to account 

for uncertainty in mapping extensions beneath overlapping 

cover rocks or alluvium. The buffered tract boundaries were 

smoothed, edited, and clipped to a world shoreline data set 

(U.S. Department of State, 2009).

Known Deposits

The study area contains three Pliocene porphyry copper 

deposits (table V3): the 50 Mt Koloula deposit on Guadalcanal in the Solomon Islands and the 1.8 Gt Namosi and 23 Mt 

Waivaki deposits on Viti Levu, Fiji. No deposits are known in 

Vanuatu. The northern part of the Outer Melanesian in Papua 

New Guinea (tract 009pCu7207) contains the 1.4 Gt Pliocene 

Panguna deposit on Bougainville and the 165 Mt Miocene 

Arie deposit on Manus Island.

Solomon Islands

The 50 Mt Koloula deposit is associated with the multiphase Koloula Igneous Complex on Guadalcanal (fig. V2A). 

Koloula was discovered in 1967 by geophysical exploration 

and was characterized by 3 diamond drill holes by Utah International; the best drill intercept reported 114 m of 0.35 percent 

copper. The property was abandoned in 2002 and subsequently 

explored as part of Solomon Gold’s Guadalcanal Joint Venture 

(Solomon Gold, 2010). The resource data cited by Singer and 

others (2008) dates from the 1970s and should be considered 
Appendix V—Tract 009pCu7210 307

Table V2. Map units that define tract 009pCu7210, Outer Melanesian Arc II—Melanesia (Solomon Islands, Vanuatu, and Fiji).

[Map unit, age range, and principal lithologies are based on attributes in source maps cited; NA, not applicable; ?, no age indicated on map. Note ages are reported as listed on source maps. Ma, million years] 

Map unit Lithology Age range Source map Source map scale

Intrusive rocks

 Solomon Islands

 NA Intrusives & Plutonic Rocks Eocene and 

Oligocene

Geological Survey Division 

of the Ministry of Natural 

Resources (1969)

1:1,000,000

Alpha Minor basaltic and andesitic intrusives Age unknown—

Oligocene to Pliocene

Turner (1978) 1:100,000

D, Dh Diorite (undifferentiated), hornblende diorite ? Abraham and others (1987) 1:250,000

Delta Hisiai complex (diorite) Age unknown—

Oligocene to Pliocene

Turner (1978) 1:100,000

Delta Guadalcanal gabbro Upper Mesozoic and 

Eocene

Institute of Geological 

Sciences, London (1978)

1:150,000

Delta 2 Tauna microdiorite Age unknown—

Oligocene to Pliocene

Turner (1978) 1:100,000

Delta 2 Delta 2 Delta 2 Institute of Geological 

Sciences, London (1978)

1:150,000

Delta 4 Koloula diorite Plio-Pleistocene Institute of Geological 

Sciences, London (1978)

1:150,000

Delta prime Tiaro Bay Porphyrites Plio-Pleistocene Institute of Geological 

Sciences, London (1978)

1:150,000

Gm Micro gabbro, olivine bearing ? Abraham and others (1987) 1:250,000

Phi Fauro dacite Age unknown—

Oligocene to Pliocene

Turner (1978) 1:100,000

T Hornblende biotite tonalite ? Abraham and others (1987) 1:250,000

Vanuatu

Alpha1 Ora-Navaka Complex Lower Miocene New Hebrides Geological 

Survey (1977) 

1:100,000

Alpha2 Apuna Complex Lower Miocene New Hebrides Geological 

Survey (1977) 

1:100,000

Alpha3 Woke Complex Lower Miocene New Hebrides Geological 

Survey (1977) 

1:100,000

 NA Zones with numerous intrusion of various 

andesites; isolated dikes and other minor 

intrusions of andesite and basalt

Lower and middle 

Miocene

New Hebrides Geological 

Survey (1977) 

1:100,000

TM1 Matanui Group containing abundant 

leucocratic hornblende andesite and 

microdiorite, mesocratic andesites and basalts 

as dikes, sills, and irrgegular intrusions

Tertiary New Hebrides Geological 

Survey (1972) 

1:100,000
308 Porphyry Copper Assessment of Southeast Asia and Melanesia 

Table V2. Map units that define tract 009pCu7210, Outer Melanesian Arc II—Melanesia (Solomon Islands, Vanuatu, and Fiji).

—Continued

Map unit Lithology Age range Source map Source

map scale

Intrusive rocks 

Solomon Islands

NA Nakvaka Gabbro Lower Miocene New Hebrides Geological Survey 

(1977) 

1:100,000

Fiji

SoA1 Yavuna Stock: Syn-Orogenic Intrusive Rocks, Tholo 

Plutonic suite, (predominantly tholeitic), First 

phase-Pre Miocene (>30 Ma) 

33 Ma approximate 

K-Ar

Metallogenic map of Viti Levu 

(Mineral Resource Division, Fiji, 

1978) 

1:250,000

SoB2 Singatoka Stock: Syn-Orogenic Intrusive Rocks, 

Tholo Plutonic suite, (predominantly tholeitic), 

Second phase-late Miocene

 (~7-11Ma) 

8 Ma approximate 

K-Ar

Metallogenic map of Viti Levu 

(Mineral Resource Division, Fiji, 

1978) 

1:250,000

NA Hornblende andesite plugs and breccias Early to mid-Pliocene Geological Survey Department, Fiji 

(1965)

1:500,000

Volcanic rocks 

Solomon Islands

NA Volcanics mainly andesitic Oligocene and Eocene 

(in part Mesozoic)

Geological Survey Division of the 

Ministry of Natural Resources (1969)

1:1,000,000

NA Volcanics mainly andesitic Pliocene Geological Survey Division of the 

Ministry of Natural Resources (1969)

1:1,000,000

NA Volcanics mainly basaltic Pliocene Geological Survey Division of the 

Ministry of Natural Resources (1969)

1:1,000,000

NA Gallego Type Volcanics. Andesitic Pleistocene Geological Survey Division of the 

Ministry of Natural Resources (1969)

1:1,000,000

Ah Hornblende andesite Pleistocene Abraham and others (1987) 1:250,000

Ahi Gallego Type Volcanics. Hornblende andesite Pleistocene Abraham and others (1987) 1:250,000

Ahx-Box, 

Box-Ahx

Polymictic breccia with clasts of hornblende 

andesite

Plio-Pleistocene Institute of Geological Sciences, 

London (1978); Dunkley and Philip 

(1986)

1:250,000

Ahy, Ahyx Hypersthene andesite lava, breccia ? Abraham and others (1987) 1:250,000

Alpha Kamaleai pyroxene andesite Age unknown—

Oligocene to Pliocene

Turner (1978) 1:100,000
Appendix V—Tract 009pCu7210 309

Table V2. Map units that define tract 009pCu7210, Outer Melanesian Arc II—Melanesia (Solomon Islands, Vanuatu, and Fiji).

—Continued

Map unit Lithology Age range Source map Source 

map scale

Volcanic rocks 

Solomon Islands

Alpha Suta volcanics Miocene-Oligocene Institute of Geological 

Sciences, London (1978)

1:150,000

Alpha h Hypersthene-augite high silica andesite Pliocene Abraham and others (1982) 1:100,000

Alpha hx Andesitic tuff-breccia Pliocene Smith and others (1982) 1:100,000

Alpha i Beta x Polymictic volcanic breccia; with andesite, basaltic 

andesite and basalt clasts

Pliocene Smith and others (1982) 1:100,000

Alpha t Andesite tuff; hornblende bearing Pliocene Smith and others (1982) 1:100,000

Alpha x Andesitic volcanic breccia Pliocene Smith and others (1982) 1:100,000

BAhy-Ahy Hypersthene basaltic and hypersthene andesite 

lava

Pleistocene and Pliocene Booth and Strange (1987) 1:100,000

Beta Mbiro volcanics Upper Mesozoic Institute of Geological 

Sciences, London (1978)

1:150,000

Beta Alpha x Basaltic volcanic breccias with some andesitic 

volcanic breccias and tuffs

Pliocene Abraham and others (1982) 1:100,000

i Alpha Basaltic andesite and andesite lava, hornblendephyric, brecciated in partPliocene Smith and others (1982) 1:100,000

i Beta x Basaltic andesite and basaltic volcanic breccia Pliocene Smith and others (1982) 1:100,000

Vanuatu

Tm Volcaniclastic breccias and minor sandstones Lower Miocene New Hebrides Geological 

Survey (1977) 

1:100,000

Tom Torres Volcanics Early Oligocene and 

early Miocene 

New Hebrides Geological 

Survey (1975) 

1:100,000

Fiji

NA Natewa Volcanics: basic andesite to basalt brecia, 

flows, grits, tuffs

Late Miocene to early 

Pliocene (late or postorogenic)

Geological Survey 

Department, Fiji (1965)

1:500,000
310 Porphyry Copper Assessment of Southeast Asia and Melanesia 

Table V3. Porphyry copper deposits in tract 009pCu7210, Outer Melanesian Arc II—Melanesia (Solomon Islands, Vanuatu, and Fiji).

[Ma, million years; Mt, million metric tons; t, metric ton; %, percent; g/t, gram per metric ton; n.d., no data. Cu-Au subtype, deposits that have Au/Mo ratios 

>30 or average Au grades >0.2 g/t; NA, not applicable. Contained Cu in metric tons is computed as tonnage (Mt × 1,000,000) × Cu grade (%)]

Name Latitude Longitude Subtype Age

(Ma)

Tonnage 

(Mt)

Grade 

Contained

Cu (t) Cu Reference

(%)

Mo

(%)

Au

(g/t)

Ag

(g/t)

 Solomon Islands

Koloula 

(Guadalcanal 

Joint Venture)

 -9.797 160.022 NA 2.0 50 0.170 n.d. n.d. n.d. 85,000 Chivas (1978), Chivas 

and McDougall (1978), 

Chivas and Wilkins 

(1977), Lum and Calicutt 

(1989), United Nations 

(1985), Solomon Gold 

plc (2011)

Fiji

Namosi -18.002 178.165 NA 5.6 1,792 0.370 0.014 0.120 n.d. 6,630,400 Andrew (1995), Colley 

and Flint (1995), Colley 

and Greenbaum (1980), 

Ellis and others (1997), 

Imai and others (2007), 

Legge (1998), Leggo 

(1977), Lum and Calicutt 

(1989), Spry (2007), 

Newcrest Mining Limited 

(2010) 

Waivaka -18.056 178.187 Cu-Au n.d. 23 0.750 n.d. 0.250 n.d. 172,500 Colley and Flint (1995), 

Colley and Greenbaum 

(1980), Leggo (1977), 

Lum and Calicutt (1989)
Appendix V—Tract 009pCu7210 311

preliminary; recent exploration indicates that the deposit is 

probably larger and gold-rich.

The Koloula Igneous Complex includes an older cycle of 

>2.5 Ma pyroxene andesite dikes, granodiorite, quartz diorite, 

and gabbro and a younger (1.7–2.4 Ma) cycle of quartz diorite, 

tonalite and pyroxene-hornblende andesite dikes (Chivas and 

McDougall, 1978). Hydrothermal alteration occurred from 

4.5–1.4 Ma, making the Plio-Pleistocene deposit one of the 

youngest known island-arc porphyry systems (Chivas, 1978). 

The complex is exposed over a distance of 38 km2.Copper 

is associated with two stages of hydrothermal alteration (A, 

potassic-propylitic and B, composite early potassic alteration overprinted by sericitic and chloritic) associated with 

late tonalite phases of the Imamumu Zoned Pluton. Disseminated and veinlet chalcopyrite and bornite occur with pyrite 

and magnetite in a quartz core in the mineralized intrusions. 

Molybdenite is present in molybdenite-pyrite-quartz veins 

centered on trondhjemite dikes that may post-date copper-gold 

mineralization (Chivas, 1978). Although no molybdenum 

or gold grades were available, gold is more important than 

molybdenum in the Koloula system, based on a range of metal 

ratios from drill core. The silver to gold ratio is about 14 

(Chivas, 1978). The deposit formed at a depth of about 3 km; 

the depth of oxidation ranges from 10 to 50 m, and supergene 

enrichment is limited (Chivas, 1978; Chivas and Wilkins, 

1977).

The Koloula deposit lies along a northeast-trending corridor that includes the Chikora porphyry, Koloula, the Sutakiki 

and Central prospect areas, and extends for 25 km from 

Koloula to the Gold Ridge epithermal gold deposit (fig. V2A). 

Drilling at the Chikora prospect in 2009 intersected disseminated copper and gold in potassically-altered porphyry.

Fiji

The Namosi district of Viti Levu includes the Waisoi 

area and the Waivaka Corridor (fig. V2C), where more than 

15 major porphyry copper and gold prospects have been 

explored since the early 20th century (Imai and others, 

2007). Porphyry copper prospects are associated with diorite 

and quartz diorite intrusions into late Oligocene to middle 

Miocene metamorphosed basaltic and andesitic rocks of the 

Wanimala Group and middle Miocene to Pliocene andesites 

and pyroclastic rocks of the Medrausucu Group (Namosi 

andesite). The main deposit in the Namosi district is at 

Waisoi, where two zones of bornite-chalcopyrite are recognized, Waisoi West and Waisoi East. Namosi is an advanced 

porphyry copper-gold exploration project on a 72,000 ha 

mining tenement on southern Viti Levu (Newcrest Mining 

Limited, 2010). The Namosi project includes Waisoi, where 

Newcrest Mining Limited holds probable reserves of 570 Mt 

at 0.43 percent copper and 0.14 g/t gold, and total resources 

(indicated and inferred) of 1,253 Mt at 0.37 percent copper 

and 0.12 g/t gold. These figures represent 70 percent of the 

ore reserves and resources of the deposit held by Newcrest 

(Newcrest Mining Limited, 2010).

The 6.7–5.8 Ma diorite porphyry intrusion associated 

with bornite-chalcopyrite zones in the Waivaka corridor is 

slightly younger than the 11.9–7.4 Ma K-Ar ages for diorite 

porphyry at Waisoi (Tanaka and others, 2010). Porphyry copper mineralization has not been identified at three other quartz 

diorite intrusions in the Namosi district. The 23 Mt Waivaka 

deposit is located about 7 km southeast of Waisoi. Geochemical studies comparing Waisoi and the Waivaka corridor intrusions suggest that crustal contamination and higher oxidation 

states in the Waivaka corridor magmas led to gold-poor porphyry systems in the Waivaka area (Tanaka and others, 2010).

Prospects, Mineral Occurrences, and Related 

Deposit Types

Porphyry copper prospects and mineral occurrences that 

may be associated with porphyry systems are listed in table 

V4.

Solomon Islands

Active exploration projects are targeting porphyry copper 

systems in the Solomon Islands on Fauro Island, in the New 

Georgia Islands, and on Guadalcanal (fig. V2A) The Ballyorlo 

prospect on Fauro Island is associated with the Pliocene (?) 

Fauro dacite. The porphyry target was identified by geochemical anomalies and an aeromagnetic high. The porphyry target 

is situated between epithermal gold targets that have been the 

focus of drilling to date (table V4). The Mase, Tirua, and Kele 

exploration targets on New Georgia Island are associated with 

Plio-Pleistocene multiphase porphyry intrusions and eroded 

andesitic stratovolcanoes. Drill intercepts with anomalous 

copper and gold grades are compatible with porphyry copper 

systems. The Poha and Mbetilonga prospects on Guadalcanal 

are associated with Oligocene intrusions. The Poha prospect 

was explored in 1997; 11 copper and (or) gold prospects 

were identified in association with altered diorite-tonalite. 

The Mbetilponga prospect, situated in a nested caldera, was 

explored in the 1970s and is currently within the Guadalcanal Joint Venture project targeting a low-grade, high tonnage 

porphyry copper deposit with a supergene-enriched cap (table 

V4).

Vanuatu

Copper- and iron sulfide-bearing porphyritic andesite and 

diorite intrusions (fig. V2B) up to 2 km across are present on 

Espiritu Santo (~25 Ma), Malekula, and in the Torres Islands 

(39 Ma) (Mitchell and Warden, 1971). Some of the composite 

fault-controlled high-level late Miocene intrusions in western Espiritu Santo and central and northern Malekula may 

represent upper parts of porphyry copper systems (Vanuatu 

Department of Geology, Mines, and Water Resources, 1995). 

Indications of porphyry mineralization include proximity of 

intrusions to major faults; association with oxidized, magne-
Table V4. Significant prospects and occurrences in tract 009pCu7210, Outer Melanesian Arc II—Melanesia (Solomon Islands, Vanuatu, and Fiji). [Rank 4=prospect in global database of Singer and others (2008) or >16,000 t contained copper; Rank 3=drilled, with >20 m of 0.2% or more Cu. Rank 2=drilled or trenched wCu, or past or ongoing exploration. Rank 1=copper occurrence that may be related to porphyry-type mineralization based on stream sediment or magnetic anomaly or location data; %, percent; g/t, grams per metric ton; km, kilometers; m, meters; ppm, parts per million; Ma, million years] Name Latitude Longitude Age Comments Reference 

 Solomon Islands Ballyorlo -6.869 156.066 Pliocene? Fauro Island. Porphyry copper exploration target of Solomon Gold plc (2010). Trench results: 16 m at 450 ppm Cu. Aeromag high. Cu, Mo, Au, Se signature. Gold slightly anomalous in rock chips; high in BLEG samples. Solomon Gold p

Meriguna -6.834 156.043 Pliocene? Solomon Gold exploration target. Epithermal signature (Au- Ag-Cu-Te-As-Hg-Sb-Pb-Zn). Location = drill hole FDDH001 - drilled 2010, 9,900 m diamond drilling program; expected to intersect argillic-altered brecciated dacite porphyry, Gold- bearing quartz sulfide veins at surface. Trenching over 400 by 250 m area; up to 20 m at 4.3 g/t Au. Solomon Gold p

Kiovokase -6.863 156.052 Pliocene? Solomon Gold exploration target ~2 km W of Ballyorlo porphyry copper target on Fauro Island. Epithermal signature (Au-Ag-Cu-Te-As-Hg-Sb-Pb-Zn). Solomon Gold p

Fauro -6.871 156.087 Pliocene? Minor disseminations of sphalerite (?) and chalcopyrite in microdiorite on east central coast of Fauro Island. Minor occur- rence in internediate intrusive rocks—possibly porphyry-type. Geological Surv

the Ministry of Nsources (1980), (1985), Turner (

Mase -8.083 157.517 3.6 Ma XDM Resources (2011): Porphyry Cu-Au system with over- printed epithermal Au within the Mase Caldera on northern New Georgia Island. Mineralized area >5 km2. Along intersec- tion of major arc normal and arc parallel structures. Initial drilling reported broad intersections of anomalous Au and Cu associated with reactivated intrusion margin structures. Assays up to 0.5 m of 4.02 g/t Au and 0.42% Cu. Gold in trench and float samples. Adjacent Pudakona crater may be a similar set- ting. United Nations 

Resources (2011

Tirua -8.474 157.793 Plio-Pleistocene XDM Resources (2011): Porphyry Cu-Au and epithermal sys- tem centered on a 15-km-wide caldera of a basaltic stratovol- cano on southern New Georgia Island; 8 km of sector collapse; airborne magnetics and sampling indi- cate alteration zones up to 5 km2. Previous drilling by Newmont indicated 62 m at 0.45% Cu; 3 m at 2.52 g/t Au. Anomalous Au in trenches and rock chip XDM Resources 
Table V4. Significant prospects and occurrences in tract 009pCu7210, Outer Melanesian Arc II—Melanesia (Solomon Islands, Vanuatu, and Fiji).—

Name Latitude Longitude Age Comments Reference 

samples; 1 km long silica-pyrite ridge; Cu-Au-Mo soil anomalies correlate with magnetic high anomalies; Cu-Au porphyry type mineralization in a 10 km2 hydrothermally altered area associated with magnetic lows. 

Kele −8.753 158.074 Plio-Pleistocene XDM Resources (2011): Porphyry Cu-Au and epithermal system 

within deeply eroded andesitic to balsaltic Kele stratovolcano assocated with muliphase porphyry intrusions (granodiorite, porphyry diorite, microdiorite) along long-lived arc normal and arc parallel fault intersections. Drill intercepts: 25 m of 0.15% Cu, 1.84 g/t Au and 53 m of 0.20% Cu and 0.80 g/t Au. Cu and Au in trench sampling.

XDM Resources 

Hidden Valley −9.367 159.733 2.6 Ma Veins, shears, disseminations United Nations Poha −9.433 159.833 24.4 Ma Diorite-tonalite 24.4 Ma age. Explored by Leigh Resources Corp. 

1997: 11 Cu and/or Au prospects identified; heavy vegetation; altered diorite and volcaniclastic rocks; massive magnetite-pyritechalcopyrite skarn; 

Chivas and McDLum and CalicuUnited Nations Resources Corp

Mbetilonga (Guadalcanal Joint Venture)

−9.612 160.164 31.3 Ma Exploration license area targeting low grade, high tonnage 

porphyry copper with a copper-rich oxide cap. Soil copper >0.1% Cu over an area of 3 km2 outlines and trenched; 155 m at 1.33% 

Cu (2005). Prospect is within a large nested caldera structure 15 km S of Honiara, Guadalcanal. Exploration by Utah in 1970s showed widespread high Cu in soils; rock chip float samples with >1% Cu. 

United Nations 

Vanuatu

Espiritu Santo skarn prospect area 2

−15.442 166.818 n.d. Fe-Cu skarn in andesite near gabbro; location digitized from S 

Santo 1:100K geologic map 

New Hebrides GSurvey (1977)

Espiritu Santo skarn prospect area 1

−15.467 166.827 n.d. Fe-Cu skarn in andesite near gabbro; location digitized from S 

Santo 1:100K geologic map 

New Hebrides GSurvey (1977)

Espiritu Santo skarn prospect area 3

−15.386 166.803 n.d. Fe-Cu skarn in andesite near gabbro; location digitized from S 

Santo 1:100K geologic map 

New Hebrides GSurvey (1977)
Name Latitude Longitude Age Comments Reference N Malakula pros- pect area? -15.999 167.254 n.d. Porphyry copper-gold prospect :Island Arc Resources (Business Wire, 1997). Diorite intrusion with anomalous gold; up to 0.44 g/t gold in grab samples occurs two kilometers to the south. This trend lies four kilometers east of the Mt. Wingtar copper-gold porphyry prospect. New Hebrides G

Survey (1977), B(1997) 

 Fiji Savundrondro Creek -16.749 179.392 n.d. Pyritic disseminated deposit, copper, porphyry-type Mineral Resour

(1978b), Colley baum (1980) 

Vunda -17.681 177.496 n.d. Porphyry copper type; epigenetic, irregular or unknown form. Mineral Resour

(1978a) 

Tuvatu (Kingston Mine) -17.696 177.599 Pliocene Porphyry copper type; epigenetic, irregular or unknown form. Tuvatu : Low-sulfidation epithermal gold deposit on Viti Levu overprinting low-grade porphyry copper system. Mineral Resour

Fiji (1978a), Lio(2011) 

Tawaravi Creek -17.702 177.530 n.d. Porphyry copper type; epigenetic, irregular or unknown form. Mineral Resour

(1978a) 

Nuku -17.798 178.207 n.d. Porphyry type (orogenic); pyritic disseminated deposit. Colley and Gree

Mineral Resour(1978a)

Wainivau -17.877 177.941 n.d. Major disseminated mineral occurrence; porphyry type (orogenic). Colley and Gree

Mineral Resour(1978a)

Nathilenga -17.995 177.366 n.d. Porphyry type (orogenic); pyritic disseminated deposit. Colley and Gree

Mineral Resour(1978a)

Kule -18.023 177.367 n.d. Porphyry type (orogenic). Colley and Gree

Mineral Resour(1978a)

Rama Creek -18.023 177.832 n.d. Porphyry type (orogenic); disseminated. Colley and Gree

Mineral Resour(1978a)

Emperor -17.509 177.855 Pliocene Low-sulfidation epithermal gold deposit on Viti Levu overprinting low-grade porphyry copper system. Mineral Resour

(1978a) 

Table V4. Significant prospects and occurrences in tract 009pCu7210, Outer Melanesian Arc II—Melanesia (Solomon Islands, Vanuatu, and Fiji).—
 

tite-bearing intrusions; alteration types (propylitic, sericitic, 

locally potassic); placer gold occurrences; anomalous copper, 

gold, and other base metals in stream sediments and soils; 

disseminations, stockworks and veins of pyrite±chalcopyrite 

pyrrhotite associated with intrusions; and gold-bearing skarns 

in limestone adjacent to intrusions. The western belt also is 

prospective for epithermal gold (prospects on Espiritu Santo, 

Malekula, and northern Efate) and for “Porgera-style” gold, 

described as gold in brecciated diorite porphyry without 

copper or porphyry-type alteration, in northwestern Espiritu 

Santo (Vanuatu Department of Geology, Mines, and Water 

Resources, 1995).

Fiji

In their study of mineral deposits of the Fiji platform, 

Colley and Greenbaum (1980) described 11 prospect areas 

as porphyry-type [10 on Viti Levu including the Waivaka 

and Namosi (Waisoi) deposits, and one prospect on Vanua 

Levu] in addition to a number of copper skarn and epigenetic 

vein occurrences. Low-sulfidation epithermal gold deposits 

overprint low-grade porphyry copper systems at the Emperor 

and Tuvatu deposits on Viti Levu (fig. V2C). These systems 

lie along the Viti Levu lineament, a prominent east-northeasttrending structure formed by extension related to onset of 

Vanuatu Trench subduction that extends to Vanua Levu and 

localizes 7 Pliocene shoshonitic and high-K calc-alkaline 

volcanic centers (Spry and others, 2003). The three major 

epithermal gold deposits of Fiji lie along the lineament. The 

low-sulfidation epithermal gold deposits at Emperor and 

Tuvatu on Viti Levu are related to monzonite intrusions that 

host low-grade porphyry copper systems; the high-sulfidation 

epithermal Mount Kasi deposit on Vanua Levu is not known 

to be associated with a porphyry system (Scherbarth and Spry, 

2006).

Exploration History

The Solomon Islands were mapped and explored by 

the British Geological Survey prior to independence of the 

nation in 1980. Guadalcanal was prospected for alluvial 

gold in the 1930s. Geochemical reconnaissance surveys of 

beach sands and stream sediments were done as part of the 

1965–68 United Nations Development Program, which also 

produced a 1:2,000,000-scale atlas of prospects and mineral 

occurrences (United Nations, 1985). Utah Development 

Company explored Guadalcanal from 1969 to 1974 (Chivas, 

1978). Exploration throughout the 1990s led to development 

of an epithermal gold deposit that went into production as 

the Gold Ridge Mine on Guadalcanal in 1998. Political and 

ethnic violence in 2000 led to mine closure and cessation of 

exploration activities (Lyday, 2001); Gold Ridge was scheduled to reopen in 2011. Since 2005, exploration for epithermal gold and porphyry copper-gold targets in the Solomon 

Islands has increased, and some areas identified in the 1990s 

are being revisited, such as the Mbetilonga and Koloula 

intrusive complexes on Guadalcanal and Fauro Island in the 

Shortland Islands.

Decline in copper prices in the 1960s, followed by 

periods of political change (independence for the Solomon 

Islands and Vanuatu in 1980), subsequent periods of political 

and social unrest, and disruptions caused by earthquakes and 

tsunamis have had a negative impact on mineral exploration and development. However, since approximately 2005, 

exploration activity in the Solomon Islands has increased, 

and drilling operations were initiated at a number of prospects in 2010.

Placer Pacific explored the Waisoi area of Fiji from 1991 

to 1995, completed a feasibility study, and delineated a total 

resource of 900 Mt at 0.43 percent copper and 0.14 g/t gold as 

amenable to open-pit mine development. Subsequent exploration in the district in the 2000s identified an 8 by 1.5 km 

corridor of porphyry copper-gold mineralization at Waivaka, 

about 7 km south of Waisoi.

Sources of Information

Most of the data used for the assessment was derived 

from published geologic maps, journal articles, and Web 

searches for recent information on exploration activities.

The British Geological Survey (BGS) participated in 

United Nations Development Programs in the Solomon 

Islands in the 1960s and completed mapping and geochemical sampling projects from 1976 to 1983, which produced 

1:100,000-scale maps of some islands and identified epithermal gold exploration targets. Bibliographic references to Solomon Islands project results, including references to unpublished reports that were not readily available for this study, are 

cited at http://www.bgs.ac.uk/geochemcd/solomon/sol6.htm.

Information on mining and geology in Fiji, including 

mining tenement and mineral prospect locations maps is available on-line from the Mineral Resources Department Web site 

(http://www.mrd.gov.fj/gfiji/).

Data sources used in this assessment are listed in 

table V5.

Grade and Tonnage Model Selection

The three known deposits in the permissive tract area 

(table V3) fit either a general model or a copper-gold subtype 

model based on t-tests of reported tonnages and grades (table 

6). Waivaka is classified as a copper-gold porphyry deposit 

based on an average gold grade of 0.25 g/t gold. Namosi, 

with an average reported grade of 0.14 g/t gold and 0.014 

percent molybdenum, falls within the Au/Mo ratio range 

that Singer and others (2008) defined as the grade range 

for the general type of porphyry copper deposit. No gold 

or molybdenum grades are reported for Koloula. Porphyry 

copper deposits in island-arc settings tend to be gold-rich 

(Kesler, 1973). Based on the geologic setting, available gold 

Appendix V—Tract 009pCu7210 315
316 Porphyry Copper Assessment of Southeast Asia and Melanesia

Table V5. Principal sources of information used for tract 009pCu7210, Outer Melanesian Arc II—Melanesia (Solomon Islands, Vanuatu, and Fiji).

[NA, not applicable]

Theme Map or title Scale Citation

Geology Geology of the British Solomon Islands 1:1,000,000 Geological Survey Division of the Ministry of Natural Resources (1969)

Geological map of Guadalcanal 1:150,000 Institute of Geological Sciences, London (1978)

Geology of New Georgia Group, 1:250,000 Abraham and others (1987)

New Georgia Geological Map Sheet 

NG 6

1:100,000 Dunkley and Philip (1986)

New Georgia Geological Map Sheet 

NG 7

1:100,000 Booth and Strange (1987)

New Georgia Geological Map Sheet 

NG 1

1:100,000 Smith and others (1982)

Shortland Islands Geological Map Sheet 

SH 1A

1:100,000 Turner (1978) 

 Geology of Ranongga, Simbo, and 

Ghizo Islands

1:100,000 Abraham and others (1982)

Geology of Malekula 1:100,000 New Hebrides Geological Survey (1972)

Geology of South Santo 1:100,000 New Hebrides Geological Survey (1977)

Geology of the Torres Islands 1:100,000 New Hebrides Geological Survey (1975)

Geological map of the New Hebrides 

Condominium

1:1,000,000 British Directorate of Overseas Surveys (Mallick, 1975)

Geological map of Fiji 1:500,000 Geological Survey Department, Fiji (1965)

Reconnaissance geology of Vanua Levu 1:200,000 Geological Survey Department ,Fiji (1963)

Metallogenic map of Viti Levu and 

Vanua Levu 

1:250,000 Mineral Resource Division, Fiji (1978a,b)

Geophysics Aeromagnetic map of southern Espiritu 

Santo and Malekula, Vanuatu

1:1,000,000 Vanuatu Department of Geology, Mines, and Water Resources (1995)

Mineral 

occurrences

Porphyry copper deposits of the world: 

database, map, and grade and tonnage 

models

 NA Singer and others (2008)

Mineral occurrences map of the 

British Solomon Islands

1:1,000,000 Geological Survey Division of the Ministry of Natural Resources (1980)

Metallic mineral deposits of Fiji NA Colley and Greenbaum (1980)

Solomon Islands Atlas of Mineral 

Resources

1:2,000,000 United Nations (1985)

Fiji mineral occurrences 1:250,000 Mineral Resource Division, Fiji (1978a,b) 

Exploration Solomon Islands exploration NA Solomon Gold (2010)

Vanuatu exploration NA Vanuatu Department of Geology, Mines, and Water Resources (1995)

Fiji exploration NA Lion One Metals (2011), Newcrest Mining Limited (2010)
Appendix V—Tract 009pCu7210 317

grades, proximity of many prospects to epithermal gold 

systems, statistical tests, and consistency with the model 

used for the Outer Melanesian Arc—Papua New Guinea tract 

(009pCu7207), the copper-gold subtype grade and tonnage 

model was selected as the appropriate model for the simulation of undiscovered resources.

Estimate of the Number of Undiscovered Deposits

Rationale for the Estimate

The permissive tract contains three known porphyry 

copper deposits, 23 prospects (10 in the Solomon Islands, four 

in Vanuatu, nine in Fiji), four epithermal gold deposits, and 

additional epithermal gold prospects that may be associated 

with porphyry copper deposits at depth. Based on the prospect 

rankings listed in table V4, two prospects have drill-indicated 

intercepts of reasonable copper grades (rank 3); nine prospects 

have active or past exploration (rank 2), and more than 10 copper occurrences may be porphyry-related (rank 1).

The area is well-mapped and was explored in reconnaissance fashion in the 1960s. Exploration continues to expand 

the identified resources in the Namosi district, Fiji. Namosi, 

at the southern end of the permissive tract, and Panguna, in 

the adjoining tract to the north, are major porphyry copper 

deposits; the presence of these two deposits is an indication 

of resource potential within the overall arc system. Andesitic 

volcanic rocks are the dominant lithology exposed throughout 

the tract; intrusions mainly are small, steep-sided, stocks and 

dikes that intrude the volcanic rocks indicating that most of the 

tract area is at an appropriate level of depth of erosion where 

exposed intrusions may represent tops of porphyry systems. 

In addition, deposits may be preserved under shallow volcanic cover. Some prospects are associated with deeply eroded 

stratovolcanoes. The geologic setting of the tract, an area of 

protracted magmatism, arc reversal, and large-scale faulting 

and extension, is similar to other areas of the southwestern 

Pacific where numerous porphyry copper deposits have been 

found. The tract area and aspects of the geologic setting are 

similar to the Luzon Arc of the Philippines, which hosts 14 

porphyry copper deposits.

On the basis of the available data, the team estimated 

a 90-percent chance of one or more undiscovered deposits, 

a 50-percent chance of five or more undiscovered deposits, 

and a 10-percent chance of 10 or more undiscovered deposits 

within the tract area (table V6). Preliminary drilling results 

for the Triua, Kele, and Mbetilonga prospects in the SoloTable V7. Results of Monte Carlo simulations of undiscovered resources for tract 009pCu7210,Outer Melanesian Arc II—Melanesia 

(Solomon Islands, Vanuatu, and Fiji).

[Cu, copper; Mo, molybdenum; Au, gold; and Ag, silver; in metric tons; Rock, in million metric tons]

Material

 Probability of at least the indicated amount Probability of

 0.95 0.9 0.5 0.1 0.05 Mean Mean or 

greater

None

Cu 0 480,000 9,100,000 40,000,000 60,000,000 16,000,000 0.32 0.07

Mo 0 0 21,000 270,000 470,000 92,000 0.24 0.23

Au 0 47 760 2,900 3,800 1,200 0.35 0.07

Ag 0 0 1,700 12,000 24,000 5,100 0.23 0.17

Rock 0 120 1,900 8,400 11,000 3,200 0.33 0.07

Table V6. Undiscovered deposit estimates, deposit numbers, tract area, and deposit density for tract 009pCu7210, Outer Melanesian 

Arc II—Melanesia (Solomon Islands, Vanuatu, and Fiji).

[NXX, estimated number of deposits associated with the xxth percentile; Nund, expected number of undiscovered deposits; s, standard deviation; Cv%, coefficient 

of variance; Nknown, number of known deposits in the tract that are included in the grade and tonnage model; Ntotal, total of expected number of deposits plus 

known deposits; km2, area of permissive tract in square kilometers; Ntotal/100k km2, deposit density reported as the total number of deposits per 100,000 km2. 

Nund, s, and Cv% are calculated using a regression equation (Singer and Menzie, 2005)]

Consensus undiscovered deposit estimates Summary statistics

Tract area (km2

) Deposit density 

(Ntotal/100k km2

) N90 N50 N10 N05 N01 Nund s Cv% Nknown Ntotal

 1 5 10 10 10 5.2 3.2 61 3 8.2 38,180 21
318 Porphyry Copper Assessment of Southeast Asia and Melanesia

mon Islands (table V4) indicate that further characterization 

may lead to delineation of deposits. In addition, several other 

exploration target areas have favorable geochemical signatures. The abundance of small intrusions, hydrothermal alteration, and copper skarns in southern Espiritu Santo, Vanuatu, 

indicates a potential for a porphyry system. A porphyry prospect was explored on Malekula prior to 1997, but the location 

and results are not available. The presence of nine geographically dispersed porphyry-type prospects as well as the two 

porphyry systems associated with epithermal gold deposits 

at Emperor and Tuvatu are favorable factors for discovery of 

additional deposits.

The mean number of undiscovered deposits in the tract is 

5.2, with a low coefficient of variation of 61 percent (table V6).

Probabilistic Assessment Simulation 

Results

Undiscovered resources for the tract were estimated by 

combining consensus estimates for numbers of undiscovered 

porphyry copper deposits with the global porphyry coppergold model of Singer and others (2008) using the EMINERS 

program (Root and others, 1992; Bawiec and Spanski, 2012; 

Duval, 2012). Selected output parameters are reported in table 

V7. Results of the Monte Carlo simulation are presented as a 

cumulative frequency plot (fig. V3). The cumulative frequency 

plot shows the estimated resource amounts associated with 

cumulative probabilities of occurrence, as well as the mean, 

for each commodity and for total mineralized rock. Note that 

the estimates and simulation results apply to the entire tract, 

including all three sub-tract areas.

The mean amount of copper associated with undiscovered deposits in the tract is 16,000,000 metric tons; the median 

is 9,100,000 metric tons. The median value represents about 

twice the amount of identified copper resources (4,450,000 

metric tons) in the three known deposits. The undiscovered 

estimate does not include extensions to identified resources; 

given that all three known deposits are undergoing additional 

exploration in 2011, the identified resources at known deposits 

are likely to increase in the near future.

References Cited

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Division, Ministry of Natural Resources, New Georgia 

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This page left intentionally blank.
160° E 170° E 180°

5° S

15° S

Nuku

Kule

Poha

Mase

Kele

Vunda

Tirua

Fauro

Namosi

Waivaka

Wainivau

MerigunaBallyorlo

Hidden Valley

N Malakula prospect area? Savundrondro Creek

Koloula (Guadalcanal Joint Venture)

Espiritu Santo skarn prospect area 3Espiritu Santo skarn prospect area 2Espiritu Santo skarn prospect area 1

Kiovokase

Mbetilonga (Guadalcanal Joint Venture)

Rama Creek

Nathilenga

Tawaravi Creek

Kingston Mine (Tuvatu)

Emperor

FIJI

VANUATU

SOLOMON ISLANDS

PAPUA

NEW GUINEA SOUTH PACIFIC OCEAN Coral Sea PG

150°E 

10°N

10°S30°S

AUSTRALIA

NEW CALEDONIA (FRANCE)

Political boundary source: U.S. Department of State (2009)Projection: Asia South Albers Equal Area Conic;Central meridian 168° E; latitude of origin 15° S

0 100 200 300 400 KILOMETERS

0 100 200 MILES

EX

OtheAsse009pC

Porpdepotract

Porp

Figure V1. Map showing the location, known deposits, and significant prospects and occurrences for of permissive tract 009pCu7210, Outer Mela

(Solomon Islands, Vanuatu, and Fiji). FJ, Fiji; PG, Papua New Guinea
324 Porphyry Copper Assessment of Southeast Asia and Melanesia

( ( ( ( ( ( ( ( ( ( ( ( ( ( ( (

( ( ( ( ( ( ( (

(

( ( ( ( (

(

( ( (

(

(

(

SAN CRISTOBAL TRENCH

Poha

Mase

Kele

Tirua

Fauro Meriguna

Kiovokase

Ballyorlo

Hidden Valley 

Bougainville

Choiseul Island

Santa Isabel Island

Shortland Islands

New Georgia Islands

Russell Islands

SOLOMAN ISLANDS

PAPUA 

NEW GUINEA

Coral Sea

156° E 158° E 

6° S

8° S

10° S

Base from ESRI ArcGIS Online (2009)

World Shaded Relief

Political boundary source: U.S. Department of State (2009)

Projection: Asia South Albers Equal Area Conic;

Central meridian 168° E; latitude of origin 15° S

0 50 100 150 200 KILOMETERS

0 50 100 MILES
( ( ( ( ( ( ( ( ( ( ( ( ( ( (

(

( ( ( ( ( ( ( 

( (

(

( ( ( ( ( ( ( ( ( ( ( ( (

( (

Mbetilonga (Guadalcanal Joint Venture)

Makira Island

Malaita

Florida Islands

Guadalcanal

Savo

SOUTH PACIFIC OCEAN

160° E 162° E

EXPLANATION

Permissive intrusive rock

Assessed porphyry copper tract

 009pCu7210

Porphyry copper deposit

Porphyry copper prospect

Permissive volcanic rock

South Solomon MORB Terrain

 (Cretaceous basement with

 stage 1+2 arcs)

Ontong Java Plateau Terrain

 (no arcs)

Makira Terrain (Cretaceous - 

 Oligocene basement + stage 2 arc)

Central Solomon Terrain (stage 1

 arc basement + stage 2 arc)

New Georgia Terrain (Unknown

 basement, Late Miocene to 

 Holocene stage 2 arc)

(( Subduction zone

Koloula (Guadalcanal 

Joint Venture)

Appendix V—Tract 009pCu7210 325

Figure V2. Maps showing subareas 

and igneous rocks used to delineate 

tract 009pCu7210, Outer Melanesian 

Arc II—Melanesia. A, Solomon Islands, 

showing different basement “terrains” 

and extent of arc development (after 

Petterson and others, 1999). Petterson 

and others (1999) proposed the term 

“terrain” to describe the geodynamic 

framework of the Solomon Islands. 

Terrains are distinguished from one 

another based on geology, tectonic 

history, and age. The term “terrane” 

sensu stricto refers to fault-bounded 

areas that have unique geological 

histories. B, Vanuatu. C, Fiji.
326 Porphyry Copper Assessment of Southeast Asia and Melanesia 

Figure V2.—Continued

Coral Sea

16°S 

(

(

(

( ( ( (

(

( (

(

(

(

(

(

( ( ( (

(

(

( ( ( ( ( ( ( (

N Malakula prospect area?

d'Entrecasteauz South Zone

Malakula Island

VANUATU

NEW HEBRIDES TRENCH

NEW HEBRIDES TRENCH

d'Entrecasteauz North Zone

Base from ESRI ArcGIS Online (2009)

World Shaded Relief

Political boundary source: U.S. Department of State (2009)

Projection: Asia South Albers Equal Area Conic;

Central meridian 168° E; latitude of origin 15° S

0 50 100 KILOMETERS

0 25 50 MILES

25 75

B

Espiritu Santo skarn prospect area 3

Espiritu Santo skarn prospect area 2

Espiritu Santo skarn prospect area 1
Appendix V—Tract 009pCu7210 327

Espiritu

Santo

Island

SOUTH PACIFIC OCEAN

168° E

166° E

14°S

( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( (

( ( (

( ( 

Torres Islands

NEW HEBRIDES TRENCH

EXPLANATION

Permissive intrusive rock

Assessed porphyry copper tract

009pCu7210

Porphyry copper prospect

Permissive volcanic rock
Nuku

Kule

Vunda

Namosi

Emperor

Waivaka

Wainivau

Rama Creek

Nathilenga

Tawaravi Creek

Savundrondro Creek

Kingston Mine (Tuvatu)

Vitilevo Island

Vanua Levo 

Island

FIJI

SOUTH PACIFC OCEAN

Base from ESRI ArcGIS Online (2009)World Shaded ReliefPolitical boundary source U.S. Department of State (2009)Projection: Asia South Albers Equal Area Conic;Central meridian 168° E; latitude of origin 15° S

0 50 100 KILOMETERS0 25 50 MILES

25 75

18°S16°S

C 178°E 180°

Figure V2.—Continued
Appendix V—Tract 009pCu7210 329

0.01 0.1 1 10 100 1k 10k 100k 1M 10M 100M 1B 10B 100B

Material, in metric tons

1.00

0.90

0.80

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

Probability

Mean Cu Mean Rock

Mean Ag

Mean Mo

Mean Au

Cu

Mo

Au

Ag

Rock

Mean Cu

Mean Mo

Mean Au

Mean Ag

Mean Rock

EXPLANATION

Figure V3. Cumulative frequency plot showing the results of Monte Carlo computer simulation of undiscovered 

resources in tract 009pCu7210, Outer Melanesian Arc II—Melanesia (Solomon Islands, Vanuatu, and Fiji). 

k, thousands; M, millions; B, billions; Tr, trillions.
330 Porphyry Copper Assessment of Southeast Asia and Melanesia

Appendix W. Description of GIS Files

Three ESRI shapefiles (.shp) and an ESRI map document (.mxd) are included with this report. These may be downloaded 

from the USGS Web site as zipped file GIS_SIR5090-D.zip.

The shapefiles are as follows:

SE_Asia_pCu_Tracts.shp is a shapefile of the permissive tracts. Attributes include the tract identifiers, tract name, a brief 

description of the basis for tract delineation, and assessment results. Attributes are defined in the metadata that accompanies the 

shapefile.

Probabilistic assessment results are included in two tables in the GIS project. Results table 1 shows quantiles for each tract. 

Results table 2 shows the mean amount for each commodity by tract. Note that separate results are included for sub-tracts of 

the Eastern Medial New Guinea magmatic belt (009pCu7203a and 009pCu7203b) and for sub-tracts of the Sunda-Banda Arc 

(142pCu7205a, 142pCu7205b, and 142pCu7205c). For the Outer Melanesian Arc II, a single assessment was made (reported as 

009pCu7210) in the tables; the assessment applies to the three geographically separate areas that comprise the tract.

SE_Asia_pCu_Deposits_prospects.shp is a shapefile of point locations for known deposits (identified resources that 

have well-defined tonnage and copper grade) and prospects. Shapefile attributes include the assigned tract, alternate site names, 

information on grades and tonnages, age, mineralogy, associated igneous rocks, site status, comments fields, data sources and 

references. Attributes are defined in the metadata that accompanies the shapefile. Note that tonnage and grade information are 

numeric fields; entries of -9999 in these fields mean that no data are available. Entries of 0 in the Age_Ma field mean that no 

data are available.

SE_Asia _political_boundaries.shp is a shapefile showing the outline of the study area and the countries within and adjacent to the study area. The shapefile is extracted from the country and shoreline boundaries maintained by the U.S. Department 

of State (2009).

These three shapefiles are included in an ESRI map document (version 9.3): GIS_SIR5090-D.mxd.

Reference Cited

U.S. Department of State, 2009, Small-scale digital international land boundaries (SSIB)—Lines, edition 10, and polygons, beta 

edition 1, in Boundaries and sovereignty encyclopedia (B.A.S.E.): U.S. Department of State, Office of the Geographer and 

Global Issues.
Appendix X. Assessment Team

Arthur A. Bookstrom, USGS Western Mineral and Environmental Resources Science Center, Spokane, Wash., United States. 

Economic geologist with expertise on porphyry copper and mineral resource assessment.

Dennis P. Cox, USGS Emeritus Scientist. Economic geologist with expertise on porphyry copper and mineral resource assessment.

Connie L. Dicken, USGS Eastern Mineral and Environmental Resources Science Center, Reston, Va., United States. GIS task 

leader for the USGS Global Mineral Resource Assessment Project.

Benjamin J. Drenth, USGS Central Mineral and Environmental Resources Science Center, Denver, Colo., United States. Geophysicist, USGS Global Mineral Resource Assessment Project.

Jane M. Hammarstrom, USGS Eastern Mineral and Environmental Resources Science Center, Reston, Va., United States. Cochief, USGS Global Mineral Resource Assessment Project since 2007. Task leader, porphyry copper assessment.

Pairatt Jarnyaharn, CCOP representative for Thailand at the 2005 project workshop, is a geologist with the Royal Thai Government Department of Mineral Resources, Bangkok, Thailand.

Gwaibo Kopi, CCOP1 representative for Papua New Guinea.

Steve Ludington, USGS Western Mineral and Environmental Resources Science Center, Menlo Park, Calif., United States. Economic geologist with expertise on porphyry copper and mineral resource assessment.

Gilpin R. Robinson, Jr., USGS Eastern Mineral and Environmental Resources Science Center, Reston, Va., United States. Dr. 

Robinson is a geologist, geochemist, and mineral-resources specialist working on mineral resource assessment and 

other projects, including geologic mapping, studies of the origin and genesis of metal and industrial-mineral deposits, 

and geochemical modeling.

Nguyen Thi Minh Ngoc, CCOP1 representative for Vietnam at the 2010 Pusan workshop, serves as Officer of International Cooperation Division of the Department of Geology and Minerals of Vietnam in Hanoi, Vietnam.

Pichai Otarawanna, CCOP1 representative for Thailand at the 2005 project workshop, geologist with the Thai Department of 

Mineral Resources, Bangkok, Thailand.

Chen Shick Pei, Director of the CCOP1 Technical Secretariat in 2006. Former Director General of the Geological Survey of 

Malaysia.

Ung Phany, CCOP1 representative for Cambodia at the 2010 Pusan workshop, Director, Cambodian National Petroleum Authority, Phnom Penh, Cambodia.

Nguyen Vay Quy, CCOP1 representative for Vietnam, Department of Geology and Minerals, Hanoi, Vietnam.

Takehiro Sakimoto, CCOP1 representative for Thailand, Senior Geologist at the Royal Thai Government Department of Mineral 

Resources, Bangkok, Thailand.

Dulcie Saroa, CCOP1 representative for Papua New Guinea at the 2010 Pusan workshop. Acting Manager, Geological Mapping 

and Mineral Exploration Branch, Geological Survey Division, Mineral Resources of Papua New Guinea, Port Moresby, 

Papua New Guinea.

Norberta Soares da Costa, CCOP1 representative for Timor-Leste, Director of Geology and Mineral Resources, Secretary of 

State for Natural Resources, Dili, Timor-Leste.

Bambang Tjahjono Setiabudi, CCOP1 representative for Indonesia, former Head of the Technical Support Division, Center for 

Geological Resources, Geological Agency of Indonesia, West Java, Indonesia. Dr. Setiabudi has authored numerous 

papers on the geology and mineral deposits of Indonesia.

I.M. Sim, CCOP1 representative for Cambodia, Department of Geology and Mines, Phnom Penh, Cambodia.

Sieng Sotham, CCOP1 representative for Cambodia, Department of Geology and Mines, Phnom Penh, Cambodia.

Wudhikarn Sukserm, CCOP1 representative for Thailand, is the Senior Geologist at the Royal Thai Government Department of 

Mineral Resources, Bangkok, Thailand.

Dwi Nugroho Sunuhadi, CCOP1 representative for Indonesia is the Senior Geologist at the Center for Geological Resources, 

Geological Agency of Indonesia, West Java, Indonesia.

Alexander Yan Sze Wah, CCOP1 representative for Malaysia, is Director of the Minerals and Geoscience Department of Malaysia, Sabah, Malaysia. He participated in all of the project workshops.

Nguyen Nhu Trung, CCOP1 Technical Secretariat, Geo-Resources Sector Coordinator, Bangkok, Thailand.

Appendix X—Assessment Team 331

1

Coordinating Committee for Geoscience Programmes in East and Southeast Asia.
332 Porphyry Copper Assessment of Southeast Asia and Melanesia

Somob Wongsomasak, CCOP1 representative for Thailand at the 2005 project workshop, geologist with the Royal Thai Government Department of Mineral Resources, Bangkok, Thailand.

Sewit Yenie, USGS Eastern Mineral and Environmental Resources Science Center, Reston, Va., United States. GIS and drafting 

assistant.

Boonsong Yokartt, CCOP1 representative for Thailand at the 2005 project workshop, geologist with the Royal Thai Government 

Department of Mineral Resources, Bangkok, Thailand.

Khin Zaw, Professor, ARC Centre of Excellence in Ore Deposits, University of Tasmania. Khin Zaw is the author of numerous 

reports, including AMIRA projects reports on the geology, tectonics and metallogeny of Southeast Asia.

Michael L. Zientek, USGS Western Mineral and Environmental Resources Science Center, Spokane, Wash., United States. Cochief, USGS Global Mineral Resource Assessment Project since 2007.
Menlo Park Publishing Service Center, California

Manuscript approved for publication, March 26, 2012

Text edited by Tracey Suzuki and James W. Hendley II

Layout and design by Stephen L. Scott
Hammarstrom and others—Global Mineral Resource Assessment—Porphyry Copper Assessment of Southeast Asia and Melanesia—Scientific Investigations Report 2010–5090–D