Global Mineral Resource Assessment

Porphyry Copper Assessment of the Tibetan Plateau, China

Scientific Investigations Report 2010–5090–F

U.S. Department of the Interior

U.S. Geological Survey

Prepared in cooperation with the China Geological Survey and the Chinese Academy of Geological Sciences.
This page left intentionally blank.
Porphyry Copper Assessment of the 

Tibetan Plateau, China

By Steve Ludington, Jane M. Hammarstrom, Gilpin R. Robinson, Jr., John C. Mars, 

and Robert J. Miller, based on contributions of Yan Guangsheng, Peng Qiuming, 

Lian Changyun, Mao Jingwen, Li Jinyi, Xiao Keyan, Qiu Ruizhao, Shao Jianbao, 

Shai Gangyi, Du Yuliang, and Dennis Cox

Global Mineral Resource Assessment

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

and Frances W. Pierce, editors

U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2010–5090–F

Prepared in cooperation with the China Geological Survey and 

the Chinese Academy of Geological Sciences
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2012

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

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

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its natural and living resources, natural hazards, and the environment—

visit http://www.usgs.gov or call 1–888–ASK–USGS

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Although this report is in the public domain, permission must be secured from the

individual copyright owners to reproduce any copyrighted material contained within this report.

Suggested citation:

Ludington, Steve, Hammarstrom, J.M., Robinson, G.R., Jr., Mars, J.C., and Miller, R.J., 2012, 

Porphyry copper assessment of the Tibetan Plateau, China: U.S. Geological Survey Scientific 

Investigations Report 2010–5090–F, 63 p. and GIS data. 
iii

Acknowledgments

The assessment of porphyry copper deposits on the Tibetan Plateau has a long history, 

and many different people have been involved. Klaus J. Schulz and Joseph A. Briskey initiated 

the project and participated in the first workshop, in Kunming, Yunnan, in 2002. Drs. Stephen 

G. Peters and Warren Nokleberg coordinated and led the initial assessment activities, prepared 

preliminary reports, and represented the USGS to our Chinese counterparts at several meetings. 

Jack H. Medlin, as USGS international specialist for Asia and the Pacific, facilitated joint 

project activities. Kathleen M. Johnson, USGS Mineral Resources Program Coordinator 

provided spirited and constant support over the life of the project. Niki E. Wintzer, Heather L. 

Parks, Deborah A. Briggs, and Kathleen D. Gans provided technical support.

USGS colleagues Peter Vikre, David M. Sutphin, Michael L. Zientek, and Mark J. 

Mihalasky served on an assessment oversight committee to evaluate the assessment results 

prior to publication. Stephen G. Peters provided data, expertise, and reviews of preliminary 

drafts of some assessment tracts.

Technical reviews of the manuscript and GIS were provided by Edward A. du Bray, Robert 

A. Ayuso, and Connie Dicken.

Scientists from the China Geological Survey and the Chinese Academy of Geological 

Sciences generously participated in assessment meetings and provided data that would not have 

otherwise been available. We would especially like to thank Drs. Qiu Ruizhao, Tan Yonglie, 

and Chen Xiufa, who accompanied the senior author on a field trip in western North America 

and hosted him for visits to copper deposits in China.
iv

Contents

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

Introduction.....................................................................................................................................................1

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

Report Format........................................................................................................................................4

Political Boundaries .............................................................................................................................4

Considerations for Users of this Assessment..................................................................................4

Porphyry Copper Deposit Models...............................................................................................................5

Occurrence Models..............................................................................................................................6

Grade and Tonnage Models................................................................................................................6

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

Igneous Provinces................................................................................................................................8

Jinsa-Ailaoshan Shoshonitic to Alkaline Igneous Province .........................................................9

Yulong Porphyry Belt...................................................................................................................9

Ailaoshan Porphyry Belt...........................................................................................................10

Gangdese Shoshonitic Igneous Province ......................................................................................10

Tibetan Potassic/Ultrapotassic Igneous Province........................................................................11

The Adakite Issue ...............................................................................................................................11

Assessment Data.........................................................................................................................................11

Geologic Maps ....................................................................................................................................11

Mineral Occurrence Data .................................................................................................................11

Geochemical Data ..............................................................................................................................12

ASTER Data..........................................................................................................................................12

Other Data............................................................................................................................................13

Exploration History.......................................................................................................................................13

The Assessment Process...........................................................................................................................13

Three-Part Assessment.....................................................................................................................13

Tract Delineation.................................................................................................................................14

Permissive Tracts for Porphyry Copper Deposits on the Tibetan Plateau ................................14

Yulong Tract ................................................................................................................................14

Dali Tract .....................................................................................................................................14

Gangdese Tract..........................................................................................................................16

Estimating Numbers of Undiscovered Deposits............................................................................16

Probabilistic Assessment Results....................................................................................................16

Discussion.....................................................................................................................................................17

References Cited..........................................................................................................................................19

Appendix A. Porphyry Copper Assessment for Tract 142pCu8710, Yulong—China .........................24

Appendix B. Porphyry Copper Assessment for Tract 142pCu8711, Dali—China and Vietnam.......35

Appendix C. Porphyry Copper Assessment for Tract 142pCu8712, Gangdese—China....................46

Appendix D. Description of GIS files .......................................................................................................63

Appendix E. Assessment Team .................................................................................................................63
v

Figures

 1. Locations of porphyry copper deposits and prospects of the Tibetan Plateau.........................2

 2. Subduction and post-subduction models for porphyry copper generation....................................5

 3. Models for porphyry copper deposits in non-arc settings ................................................................................ 6

 4. Cumulative frequency plot showing tonnages of Tibetan Plateau porphyry copper deposits 

compared to worldwide deposits from the grade-tonnage model .................................................. 7

 5. Map showing terranes and bounding faults and sutures of the Tibetan Plateau .....................8

 6. Map showing igneous provinces of the Tibetan Plateau ..............................................................9

 7. Map showing grid generated from stream-sediment geochemical data 

for copper in western China, along with permissive tract boundaries .............................12

 8. Map showing hydrothermally altered areas identified by ASTER..............................................................13

 9. Map showing permissive tracts for porphyry copper deposits on the Tibetan Plateau ........15

10. Chart showing identified and undiscovered copper resources 

for permissive tracts on the Tibetan Plateau .........................................................................18

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

porphyry copper prospects for tract 142pCu8710, Yulong—China ....................................25

A2. Google EarthTM view of the Yulong porphyry copper deposit, Xizang (Tibet), China..............27

A3. Cumulative frequency plot showing the results of Monte Carlo computer 

simulation of undiscovered resources for tract 142pCu8710, Yulong—China .................31

B1. Map showing tract location, known porphyry copper deposits, and significant 

porphyry copper prospects for tract 142pCu8711, Dali—China and Vietnam..................36

B2. View of Habo prospect, showing exploration tunnels in middleground...................................39

B3. Cumulative frequency plot showing the results of Monte Carlo computer 

simulation of undiscovered resources for tract 142pCu8711, Dali—China ......................42

C1. Map showing tract location, known porphyry copper deposits, and significant 

porphyry copper prospects for tract 142pCu8712, Gangdese—China..............................47

C2. Photograph of the Xietongmen porphyry copper deposit, Xizang (Tibet), China ....................48

C3. Cumulative frequency plot showing results of Monte Carlo computer simulation 

of undiscovered resources for tract 142pCu8712, Gangdese—China...............................57

Tables

 1. Summary of identified resources in porphyry copper deposits of the Tibetan Plateau...........3

 2. Statistical test results, porphyry copper assessment of the Tibetan Plateau ...........................7

 3. Permissive tracts for porphyry copper deposits on the Tibetan Plateau .................................15

 4. Estimates of numbers of undiscovered porphyry copper deposits on the Tibetan Plateau ...........17

 5. 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 on the Tibetan Plateau............17

A1. Summary of selected resource assessment results for tract 142pCu8710, Yulong—China..........24

A2. Porphyry copper deposits in tract 142pCu8710, Yulong—China ...............................................27

A3. Significant prospects and occurrences in tract 142pCu8710, Yulong—China........................29

A4. Principal sources of information used for tract 142pCu8710, Yulong—China........................30
vi

Acronyms and Abbreviations Used in this report

ANOVA analysis of variance

CCOP Coordinating Committee for Geoscience Programmes 

 in East and Southeast Asia

CGS China Geological Survey

GIS Geographic Information System

GMRAP Global Mineral Resource Assessment Project

HREE heavy rare-earth elements

kt thousand metric tons

LREE light rare-earth elements

MASH melt, assimilation, storage, and homogenization

Ma million of years before the present

Mt million metric tons

REE rare-earth elements

SCLM subcontinental lithospheric mantle

SHRIMP sensitive high resolution ion microprobe

SSIB small-scale digital internal boundaries

USGS United States Geological Survey

A5. Statistical test results for tract 142pCu8710, Yulong, China .......................................................30

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

deposit density for tract 142pCu8710, Yulong—China..........................................................31

A7. Results of Monte Carlo simulations of undiscovered resources 

for tract 142pCu8710, Yulong—China. .......................................................................................................31

B1. Summary of selected resource assessment results for tract 142pCu8711, Dali—China ......35

B2. Porphyry copper deposits in tract 142pCu8711, Dali—China and Vietnam.............................38

B3. Significant prospects and occurrences in tract 142pCu8711, Dali—China and Vietnam .....39

B4. Principal sources of information used for tract 142pCu8711, Dali—China and Vietnam ......41

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

and deposit density for tract 142pCu8711, Dali—China. ......................................................41

B6. Results of Monte Carlo simulations of undiscovered resources 

for tract 142pCu8711, Dali—China and Vietnam....................................................................41

C1. Summary of selected resource assessment results 

for tract 142pCu8712, Gangdese—China................................................................................46

C2. Porphyry copper deposits in tract 142pCu8712, Gangdese—China...........................................49

C3. Significant prospects and occurrences tract 142pCu8712, Gangdese—China.....................51

C4. Principal sources of information used for tract 142pCu8712, Gangdese—China ...................55

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

for tract 142pCu8712, Gangdese—China...............................................................................56

C6. Results of Monte Carlo simulations of undiscovered resources 

for tract 142pCu8712, Gangdese—China................................................................................56
vii

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 4,047 square meter (m2)

acre 0.4047 hectare (ha)

acre 0.4047 square hectometer (hm2) 

acre 0.004047 square kilometer (km2)

square mile (mi2) 259.0 hectare (ha)

square mile (mi2) 2.590 square kilometer (km2) 

Mass

ounce, avoirdupois (oz) 28.35 gram (g) 

pound, avoirdupois (lb) 0.4536 kilogram (kg) 

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

ton, short (T) (2,000 lb.) 907.18474 kilogram (kg)

ton, short (T) (2,000 lb.) 0.90718474 metric ton (t)

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

square kilometer (km2

) 247.1 acre

square centimeter (cm2

) 0.001076 square foot (ft2)

square meter (m2

) 10.76 square foot (ft2) 

square centimeter (cm2

) 0.1550 square inch (ft2) 

hectare (ha) 0.003861 square mile (mi2

) 

square kilometer (km2

) 0.3861 square mile (mi2)

Mass

gram (g) 0.03527 ounce, avoirdupois (oz)

kilogram (kg) 2.205 pound avoirdupois (lb)

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

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

Chemical Symbols

Element Symbol Element Symbol Element Symbol

Actinium Ac Germanium Ge Potassium (Kalium) K

Aluminum Al Gold Au Praseodymium Pr

Americum Am Hafnium Hf Promethium Pm

Antimony 

(Stibium)

Sb Helium He Palladium Pa

Argon Ar Holmium Ho Radium Ra

Arsenic As Hydrogen H Radon Rn

Astatine At Indium In Rhenium Re

Barium Ba Iodine I Rhodium Rh

Berkelium Bk Iridium Ir Rubidium Rb

Beryllium Be Iron Fe Ruthenium Ru

Bismuth Bi Krypton Kr Samarium Sm

Boron B Lanthanum La Scandium Sc

Bromine Br Lawrencium Lr Selenium Se

Cadmium Cd Lead Pb Silicon Si

Cesium Cs Lithium Li Silver Ag

Calcium Ca Lutetium Lu Sodium (Natrium) Na

Californium Cf Magnesium Mg Strontium Sr

Carbon C Manganese Mn Sulfur S

Cerium Ce Mendelveium Md Tantalum Ta

Chlorine Cl Mercury Hg Technetium Tc

Chromium Cr Molybdenum Mo Tellurium Te

Cobalt Co Neodymium Nd Terbium Tb

Copper Cu Neon Ne Thallium Tl

Curium Cm Neptunium Np Tungsten (Wolfram) W

Dysprosium Dy Nickel Ni (Unnihexium) (Unh)

Eisteinium Es Niobium Nb (Unnilpentium) (Unp)

Erbium Er Nitrogen N (Unnilquadium) (Unq)

Europium Eu Nobelium No Uranium U

Fermium Fm Osmium Os Vanadium V

Fluorine Fm Oxygen Os Xenon Xe

Francium Fr Palladium Pd Ytterbium Yb

Gadolinium Gd Phosphorus P Yttrium Y

Gallium Ga Platinum Pt Zinc Zn

Zirconium Zr
Porphyry Copper Assessment of the Tibetan Plateau, China

By Steve Ludington1, Jane M. Hammarstrom2, Gilpin R. Robinson, Jr.2, John C. Mars2, and Robert J. Miller1, 

based on contributions of Yan Guangsheng3

, Peng Qiuming3, Lian Changyun3, Mao Jingwen4, Li Jinyi3, Xiao 

Keyan3

, Qiu Ruizhao3, Shao Jianbao3, Shai Gangyi3, Du Yuliang3, and Dennis Cox1

Abstract

The U.S. Geological Survey collaborated with the China 

Geological Survey to conduct a mineral-resource assessment of 

resources in porphyry copper deposits on the Tibetan Plateau in 

western China. This area hosts several very large porphyry deposits, 

exemplified by the Yulong and Qulong deposits, each containing 

at least 7,000,000 metric tons (t) of copper. However, large parts of 

the area are underexplored and are likely to contain undiscovered 

porphyry copper deposits.

Three tracts were delineated as permissive for porphyry 

copper deposits on the Tibetan Plateau—the Yulong (Eocene 

and Oligocene), Dali (Eocene through Miocene), and Gangdese 

(Oligocene and Miocene) tracts. The tracts were defined based on 

mapped and inferred subsurface distributions of igneous rocks of 

specific age ranges in which the occurrence of porphyry copper 

deposits is possible. These tracts range in area from about 95,000 to 

about 240,000 square kilometers. Although maps of different scales 

were used in the assessment, the final tract boundaries are intended 

for use at a scale of 1:1,000,000.

The deposits on the Tibetan Plateau all formed in a postsubduction environment, one newly recognized as permissive for 

the occurrence of porphyry copper deposits. Based on the grade, 

tonnage, and geologic characteristics of the known deposits, two 

tracts, Yulong and Gangdese, were evaluated using the general 

(Cu-Mo-Au) porphyry copper grade and tonnage model. The 

Dali tract was evaluated using the gold-rich (Cu-Au) submodel. 

Assessment participants estimated numbers of undiscovered 

deposits at different levels of confidence for each permissive 

tract. These estimates were then combined with the selected grade 

and tonnage models using Monte Carlo simulation to generate 

quantitative probabilistic estimates of undiscovered resources. 

Additional resources in extensions of deposits with identified 

resources were not specifically evaluated.

Assessment results, presented in tables and graphs, show 

mean expected amounts of metal and rock in undiscovered deposits 

at different quantile levels, as well as the arithmetic mean for 

each tract. This assessment estimated a mean of 39 undiscovered 

porphyry copper deposits within the assessed permissive tracts on 

 1U.S. Geological Survey, Menlo Park, California, United States.

 2U.S. Geological Survey, Reston, Virginia, United States.

 3China Geological Survey, Beijing, China.

4

Chinese Academy of Geological Sciences, Beijing, China.

the Tibetan Plateau. This represents nearly four times the number of 

known deposits (11) already discovered. Predicted mean (arithmetic) 

resources that could be associated with the undiscovered deposits are 

about 145,000,000 t of copper and about 4,900 t of gold, as well as 

byproduct molybdenum and silver. Reliable reports of the identified 

resources in the 11 known deposits total about 27,000,000 t of copper 

and about 800 t of gold. Therefore, based on the assessments of 

undiscovered Tibetan Plateau resources in this report, about six times 

as much copper may occur in undiscovered porphyry copper deposits 

as has been identified to date.

Introduction

Cenozoic deposits on the Tibetan Plateau of western China 

constitute one of the world’s important emerging copper provinces. 

This area hosts at least two world class deposits, Yulong and Qulong, 

at least nine other porphyry copper deposits (table 1), and numerous 

prospects and related deposits (fig. 1). Yulong, which contains at least 

7,000,000 metric tons (t) of copper, was discovered in the late 1960s 

(Gu and others, 2003); soon thereafter, many additional outcropping 

deposits were discovered in the Yulong belt. Qulong, which also 

contains more than 7,000,000 t of copper, was discovered during 

regional stream-sediment geochemical studies in the late 1980s (Yang 

and others, 2009), and additional discoveries continue. Most of the 

deposits in this area contain important amounts of molybdenum, gold, 

and silver, all of which will likely be important byproducts.

Copper production commenced at Yulong in late 2008 and 

at Jiama in July of 2010. Other deposits are in advanced stages 

of development. The high altitude, remote location, and lack of 

infrastructure in the region pose serious challenges to mineral 

exploitation in the region.

The U.S. Geological Survey (USGS) conducted a probabilistic 

mineral resource assessment of undiscovered resources in porphyry 

copper deposits on the Tibetan Plateau as part of a global mineral resource 

assessment project (GMRAP). The purpose of the assessment was to (1) 

compile a database of known porphyry copper deposits and significant 

prospects, (2) delineate permissive areas (tracts) for undiscovered 

porphyry copper deposits at a scale of 1:1,000,000, (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 those undiscovered 

deposits. The study was conducted in cooperation with the China 

Geological Survey (CGS) between 2002 and 2010. The part of the 
2 Porphyry Copper Assessment of the Tibetan Plateau, China

84°E 92°E 100°E

30°N

26°N

22°N

!

!

!

!

!

!

!

!

!

! !

!

!

!

!

!

! !

! !

!

!

!

!

Lhasa

Habo

Lurige

Liufang

Sin Quyen

Xifanping

Tongchang

Narigongma

Xiaolongtan

Machangqing

Changpingchong

Jiagangxuweshan

Wangdongshan-Hongnitang

Dhaka

Patna

Kohima

Aizawl

Imphal

Khulna

Kunming

Chengdu

Barisal

Agartala

Shillong

Calcutta

Rajshahi

Chongqing

Myitkyina

Kathmandu

Chittagong

Biratnagar

CHINA

INDIA

MYANMAR

NEPAL BHUTAN

BANGLADESH

VIETNAM

INDIA

XIZANG

SICHUAN

YUNNAN

QINGHAI

GUIZHOU

0 300 600 KILOMETERS

0 150 300 MILES

1B

1A

Seli

Jicuo

Yulong

Mamupu

Zhanaga

Xiariduo

Ridanguo

Mangzhong

Gegongnong

Malasongduo

Hengxingcuo

Duoxiasongduo

98°E

32°N

30°N

0 50 100 KILOMETERS

0 30 60 MILES

1B

!

Kelu

Jiru

Nanmu

Jiama

Mingze

Bangpu

Dubuqu

Zhunuo Qulong

Sharang

Chengba

Zongxun

Xiamari

Tangbai

Tangbula

Banongla

Tinggong

Lakang’e

Luobuzhen

Yuejingou Chongmuda

Chuibaizi

Zemoduola

Demingding

Xientongmen/Newtongmen

Gangjiang

Liebu (Nuri)

Lhasa

92°E

30°N

0 75 150 KILOMETERS

0 40 80 MILES

1A

EXPLANATION

Porphyry copper deposit

Porphyry copper prospect

Related prospect

Chinese provincial boundaries

Boundary of Tibetan Plateau

Figure 1. Locations of porphyry copper deposits 

and prospects of the Tibetan Plateau. Symbol 

colors: violet, Yulong tract; red, Dali tract; green, 

Gangdese tract.
Introduction 3

Table 1. Summary of identified resources in porphyry copper deposits of the Tibetan Plateau

[Ma,million years; Mt, million metric tons; %, percent; g/t, grams per metric ton; t, metric tons; n.d., no data. Contained Cu in metric tons is computed as tonnage (Mt × 1,000,000) × Cu grade (percent)]

Tract Tract

Name Name Age (Ma)

Tonnage 

(Mt)

Cu

(%)

Mo

(%)

Au

(g/t)

Ag

(g/t)

Contained

Cu (t)

Contained

Mo (t)

Contained

Au (t)

142pCu8710 Yulong

Yulong 40.7 850 0.84 0.022 0.35 n.d. 7,140,000 187,000 298

Zhanaga 38.5 99.5 0.32 0.03 0.03 n.d. 318,000 29,900 3

Mangzhong 37.5 135 0.43 0.03 0.02 n.d. 581,000 40,500 3

Duoxiasongduo 37.4 248 0.38 0.04 0.06 n.d. 942,000 99,200 15

Malasongduo 36.0 338 0.45 0.014 0.06 n.d. 1,520,000 47,300 20

Gegongnong 38.0 101 0.5 n.d. 0.37 2.65 505,000 n.d. 37

142pCu8711 Dali

Xifanping 32 64.3 0.28 n.d. 0.31 n.d. 180,000 n.d. 20

Machanqing 35 62 0.5 0.078 0.35 n.d. 310,000 48,400 22

142pCu8712 Gangdese

Qulong 16.2 1,778 0.45 0.045 n.d. 3.9 8,000,000 800,000 nd

Xietongmen/Newtongmen* 39# 1,085 0.30 n.d. 0.22 1.20 3,310,000 n.d. 241

Jiama* 15.2 1,006 0.39 0.046 0.095 5.6 3,920,000 463,000 96

total 26,700,000 1,720,000 755

*

 These two deposits are not completely explored, but they are included as deposits because their known resource is so large.

#

 Age is in dispute; may be Jurassic.

assessment reported in this document describes permissive areas for 

deposits of Cenozoic age within the Tibetan Plateau, a geographic region 

(fig. 1) that includes the Xizang (Tibet) Autonomous Region and parts of 

the Chinese provinces of Qinghai, Sichuan, and Yunnan.

This assessment report includes an overview of the results, 

and summary tables. Detailed descriptions of each tract are 

included in appendixes, which include 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 database 

and map prepared using a GIS (geographic information system) 

accompany the report, and include tract boundaries and a database 

of known porphyry copper deposits and significant prospects.

The assessment of undiscovered porphyry copper deposits 

on the Tibetan Plateau was conducted using the three-part form 

of mineral-resource assessment based on established mineral 

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

Singer and Menzie, 2010). In the three-part form of mineral 

resource assessment, geographic areas (permissive tracts) are 

delineated using geologic, geochemical, mineral occurrence, and 

geophysical data to identify areas with features typical of the type 

of deposit under consideration. In this study, three permissive tracts 

were defined: the Yulong permissive tract (142pCu8710) on the 

northeast margin of the Tibetan Plateau, the Dali permissive tract 

(142pCu8711) in the southeast corner, and the Gangdese permissive 

tract (142pCu8712) in south central part (fig. 1). Secondly, the 

amount of metal in undiscovered deposits is estimated using 

grade and tonnage models derived from information about known 

deposits. Probabilistic estimates of numbers of undiscovered 

deposits are consistent with the known deposits that define grade 

and tonnage models (Singer, 2007a). And thirdly, estimates 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 permissive tract. 

These estimates are measures of the favorability of the tract and of 

the estimator’s uncertainty about what may exist (Singer, 2007a).

The Tibetan Plateau is an area of active mineral exploration, 

both by Chinese and international companies. Several projects, 

previously under development by Canadian and Australian 

companies, have recently reverted to full Chinese ownership. This 

report reflects the status of porphyry copper exploration projects 

known to the authors as of August 2011. The supply of copper is 

important for Chinese industry. Therefore, continued exploration 

for, and development of, porphyry copper deposits on the Tibetan 

Plateau is likely. Exploration in China, as elsewhere in the world, 

is presently focused on precious-metal deposits, due to current 

elevated metal prices, but porphyry copper systems may be 

associated with some precious-metal deposits and may be present 

in other parts of large exploration concessions under study for 

precious metals.

Terminology

The terminology used in this report follows the definitions 

used in the 1998 USGS assessment of undiscovered resources in the 

United States (U.S. Geological Survey National Mineral Resource 

Assessment Team, 2000). This terminology is intended to represent 

standard definitions that reflect general usage by the minerals 

industry and the resource assessment community.
4 Porphyry Copper Assessment of the Tibetan Plateau, China

•Mineral deposit—An occurrence of a valuable commodity or 

mineral that is 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 that is believed 

to exist or an incompletely explored mineral occurrence or prospect 

that could have sufficient size and grade to be classified as a deposit.

•Mineral prospect—A mineral concentration that is being actively 

examined to determine whether a mineral deposit exists.

•Mineral occurrence—A locality where a useful mineral or material 

is found.

•Permissive tract—The surface projection of a volume of rock whose 

geologic characteristics permit the existence of a mineral deposit of a 

specified type. The probability that deposits of the type being studied 

occur outside the boundary of the tract is negligible. In this report, 

the term is commonly abbreviated to “tract.”

•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 those in the 

porphyry copper deposits included in the grade and tonnage models 

used in the assessment (which can include measured, indicated, and 

inferred mineral resources at the lowest available cut-off grade). In 

addition, deposits that are not included in the models used for the 

assessment are considered to contain identified resources if they 

are characterized well enough to meet commonly used reporting 

guidelines.

•S-type granite—Granite in which geochemical and isotopic characteristics are primarily inherited through partial melting of a crustal 

sedimentary source.

Report Format

This report begins with a discussion of porphyry copper 

deposit models, both descriptive and grade-and-tonnage 

models. This is followed by a discussion of the tectonic history 

of the Tibetan Plateau and how that history has influenced the 

emplacement of magmatic rocks and the formation of porphyry 

copper deposits. The next section consists of comments about the 

nature and quality of the data that was gathered for the assessment, 

followed by a brief description of the exploration history of the 

area. Next, the processes used to delineate permissive tracts are 

described, and a brief description of the three permissive tracts is 

presented. The last section of the report describes the assessment 

process, including a description of how estimates of numbers of 

undiscovered deposits are made and a discussion of the assessment 

results and their significance. More detailed descriptions and 

assessment results for the three permissive tracts (Yulong, Dali, and 

Gangdese) evaluated in this report are presented in a standardized 

format in appendixes A, B, and C of this report. Tract boundaries 

and point locations of significant deposits and prospects are 

included in a geographic information system (GIS) in appendix D 

and appendix E identifies the members of the assessment team.

Political Boundaries

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.

Considerations for Users of this Assessment

Ideally, assessments are done on a recurring basis, at a 

variety of scales, because available data change over time. This 

GMRAP product represents a synthesis of current, readily available 

information, as of August, 2011. The assessment is based on the 

descriptive and grade-tonnage data contained in published mineral 

deposit models. Data in the grade and tonnage models represent 

the most reliable average grades available for each commodity of 

possible economic interest; the tonnages are based on the total of 

production, reserves, and resources at the lowest cutoff grade for 

which data were available when the model was constructed.

The economic viability of any mineral deposit depends on 

a wide variety of factors, many of which vary with time. This 

caveat applies to the deposits used to construct the grade-tonnage 

models, as well as to undiscovered deposits, so care must be 

exercised when using the results of this assessment to answer 

economic questions. If discovered, deposits may not be developed 

immediately or ever. Furthermore, the estimates in this assessment 

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 

through further drilling and characterization. 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 undiscovered deposits. 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 both exposed 

deposits and concealed deposits within 1 kilometer (km) of the 

surface. Very high-grade deposits may be exploited at greater 

depths; however, it is not common. Exploration for, and possible 

exploitation of, these deeper deposits may be so expensive that 

they may not be discovered in the near term. If they are discovered, 

the cost to mine a deeply buried porphyry deposit may easily 

prohibit its development into a mine, given current or near-term 

metal prices and technology.

Permissive tracts are identified based on geology, irrespective 

of political boundaries. Therefore, tracts may cross country 

boundaries or include lands that already have either 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.
Porphyry Copper Deposit Models 5

Porphyry Copper Deposit Models

Porphyry copper deposits typically form in subduction-related, 

compressional tectonic settings, during active subduction of oceanic 

or continental crust (Sillitoe, 2010; John and others, 2010). These 

deposits are typically associated with shallowly emplaced calcalkaline plutons. The Andes Range of South America is the classic 

province for continental arc magmatism (Kay and others, 1999; 

Richards and others, 2001). Magma associated with these deposits 

is typically hydrous, oxidized, and rich in sulfur, and has likely 

undergone complex processes of differentiation and evolution at 

the crust-mantle boundary (Richards, 2003; John and others, 2010). 

Island arcs in the southwest Pacific Ocean are the archetypes of 

island arc magmatism (Garwin and others, 2005). Magma associated 

with island arc porphyry copper deposits is similar to that associated 

with continental arcs, but diorite, quartz diorite, and other more 

mafic rocks are somewhat more abundant (Kesler and others, 1975).

In recent years, evidence has accumulated for the 

existence of a family of porphyry copper deposits that formed 

in a significantly different tectonic setting: extensional or 

transpressional regimes that form within cratons after active 

subduction has ceased. The porphyry copper deposits on the 

Tibetan Plateau are the classic and original examples of this 

family, but similar deposits are found in comparable settings 

in Mesozoic rocks on the eastern margin of the Yangtze (South 

China) craton, in Iran and Pakistan (Hou and others, 2011), and 

in other parts of the world. The geology and mineralization style 

characteristic of these deposits are broadly similar to those of 

classic porphyry copper deposits, however, the magmas that 

form them originated from as-yet poorly understood processes.

Richards (2009) presents a model based on the remelting of 

previously-subducted arc lithosphere. Such previously subducted 

lithosphere would contain small amounts of chalcophile and 

siderophile element-rich sulfide minerals, and would be a fertile 

source for hydrous, oxidized, gold-rich (but comparatively 

sulfur-poor) magmas. In his view, the remelting is triggered by 

postsubduction lithospheric thickening, lithospheric extension, or 

mantle lithosphere delamination (fig. 2).

C. DELAMINATION

A. SUBDUCTION B. COLLISION

D. POSTSUBDUCTION EXTENSION

Postsubduction

porphyry Cu deposit

Postsubduction

porphyry Cu deposit

Upper crustal

batholith

Partial

melting

Partial

melting

1000 °C

SCLM

Asthenosphere

Asthenospheric

upwelling

Asthenospheric

upwelling

Delaminated

mantle lithosphere

1000 °C

SCLM

1000 °C

SCLM

1000 °C

SCLM

1000 °C

Oceanic mantle

lithosphere

Oceanic crust

Sea level

1000 °C

1000 °C

1000 °C

SCLM

1000 °C

SCLM

1000 °C

SCLM

Partial melting Continental

crust

Continental

crust

Not represented

in China

Classic Andean

arc

Yulong, Dali

tracts

Gangdese

tract

Continental

crust

Crustal

thickening

Asthenosphere

Asthenosphere Dehydration of oceanic crust

Asthenosphere

Basaltic

underplating

Lower crustal

MASH zone

Upper crustal

batholith

Upper crustal

batholith

Lithospheric

thickening

Partial melting of

hydrated mantle

wedge

Volcanic arc Arc porphyry

Cu deposit

EXPLANATION

Partial melting in lower crust

Partial melting in hydrous cumulates

Partial melting in metasomatized subcrustal lithospheric mantle (SCLM)

Asthenospheric melt invasion

Figure 2. Subduction and post-subduction models for porphyry copper

generation (after Richards, 2009). A, Normal arc magmatism, B, Collisional 

(compressive environment), C, Post-collisional mantle delamination (Yulong 

and Dali tracts), D, Post-subduction extension (Gangdese tract). MASH – 

melting, assimilation, storage, and homogenization. SCLM – subcontinental 

lithospheric mantle. In all cases, high Sr/Y magmas may be generated by 

residual or fractionating hornblende (±garnet, titanite).
6 Porphyry Copper Assessment of the Tibetan Plateau, China

Asthenospheric

Partial melting

Upwelling

Delaminated

Interacting

with mantle Mantle lithosphere

Crust

lithosphere

Chengmenshan

Yangtze River

metallogenic belt

(Mesozoic)

Asthenosphere

Partial

melting Moho

Juvenile lower crust

Mantle lithosphere

Mantle lithosphere

Leucogranite

IYS

Orogen-transverse fault

Qulong

Gangdese

tract

Partial melting Mantle lithosphere

Thickened crust

Asthenospheric

Asthenospheric

Upwelling

melts

Dexing

Eastern China

(Mesozoic)

Moho

Mantle lithosphere

Juvenile lower crust

Mantle lithosphere

Partial

melting

Yulong, Dali

tracts

Machanqing

Yulong

A B

C D

EXPLANATION

Porphyry Cu-Mo

Porphyry Cu-Au

Normal fault

Thrust fault

Strike-slip fault

Figure 3. Models for porphyry copper deposits in non-arc settings (after Hou and others, 2011). A, Melting of lower crust triggered by translithospheric 

strike-slip faults in a late-collision, transpressional setting, B, Melting of thickened crust triggered by upwelling of asthenosphere in a post-collision, 

extensional setting, C, Melting of thickened, mafic lower crust, triggered by delamination of lithospheric root and upwelling of asthenosphere in an 

intracontinental, extensional setting, D, Melting of a delaminated lithospheric root and upwelling of asthenosphere in an anorogenic, extensional setting. 

More recently, Hou and others (2011) have promulgated a 

model that involves partially melting thickened juvenile mafic lower 

crust or delaminated lower crust, including asthenospheric mantle 

components (fig. 3). The fertility of these magmas depends on the 

contribution of copper and gold from the mantle, thickened lower 

crust that has been metasomatized due to previous underplating, and 

the inclusion of crustal components (especially molybdenum) during 

crustal melting and magma ascent. They suggest that formation of 

these magmas is triggered by asthenospheric upwelling, lithospheric 

delamination, and/or large-scale translithospheric strike-slip faults or 

orogeny-transverse normal faults.

Both Richards (2009) and Hou and others (2011) stress that 

most magmas associated with post-subduction porphyry copper-gold 

deposits are mildly alkaline (shoshonitic), rather than calc-alkaline, 

and may form isolated complexes in contrast to volcanoplutonic 

arcs. At this time, there is no evidence that these deposits in postsubduction environments have different grade-tonnage relationships 

than other porphyry copper deposits and there is no basis to create a 

grade and tonnage model specific to these deposits.

Occurrence Models

Mineral deposit models used for this assessment include 

the porphyry copper models of Singer and others (2008), Cox 

(1986a,b), and John and others (2010). The recent review of 

salient features of porphyry copper deposits by Sillitoe (2010) 

is also pertinent. The global porphyry copper database of Singer 

and others (2008) contains tabulated descriptive information 

along with grade and tonnage data. Discussions of porphyry 

copper deposits related to the special post-subduction setting of 

the Tibetan deposits are given by Richards (2009) and Hou and 

others (2011).

Grade and Tonnage Models

The grade and tonnage models of Singer and others (2008) 

were used in this assessment of undiscovered resources in 

porphyry copper deposits on the Tibetan Plateau. In addition 

to the global porphyry copper-molybdenum-gold (Cu-Mo-Au) 
Tectonic Setting 7

Table 2. Statistical test results, porphyry copper assessment of the Tibetan Plateau. 

[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 from those in the model at the 1-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 test and the model is inappropriate for the assessment. Nknown, 

number of known deposits in the tract that are included in the grade and tonnage model; -, no data]

Coded_ID Tract 

name

Nknown Model p valuesModel selected Basis for 

Tons Cu Mo Ag Au selection

142pCu8710 Yulong

6 Cu-Au-Mo 0.87 0.71 0.09 0.74 0.22

Cu-Au-Mo (general 

worldwide model) Cu-Mo 0.31 0.84 0.83 0.54 0.0027 t-test results

Cu-Au 0.89 0.77 <0.001 0.88 <0.001

142pCu8711 Dali

2 Cu-Au-Mo 0.22 0.66 0.06 - 0.42

Cu-Au

t-test results 

and geologic 

context

Cu-Mo - - - - -

Cu-Au 0.24 0.63 0.002 - 0.64

model that is based on data from 422 deposits, they identified 

two subtypes of porphyry copper deposit, each with distinct 

grade and tonnage models.

For each tract, if sufficient grade and tonnage data were 

available, the known deposits in the tract were tested against 

the global models using statistical tests (t-test or analysis of 

variance [ANOVA]) (table 2). For the Yulong tract, which 

contains six known deposits, these tests led to selection of the 

general (Cu-Mo-Au) model as the most appropriate. The Dali 

tract contains two deposits, each of which qualifies as a porphyry 

copper-gold deposit, and high gold grades at other prospects in 

that tract led to use of the gold-rich model for assessment of that 

tract. The Gangdese tract contains three known deposits, but each 

of them lacks crucial information on molybdenum or gold grades, 

precluding meaningful statistical tests, and the general model was 

used to assess that tract. The size of the known Tibetan deposits is 

comparable (fig. 4) to those in the worldwide model of Singer and 

others (2008).

Tectonic Setting

The porphyry copper deposits on the Tibetan Plateau that are 

described here formed during the Cenozoic Era, after the collision 

of the Indian continental plate with Eurasia, in a post-subduction 

setting. The tectono-magmatic history of the Tibetan Plateau has 

been summarized by Hou and Cook (2009). The plateau, which 

formed as a result of the collision of the Indian plate with Eurasia, 

is composed of four terranes; from north to south, they are the 

Songpan-Ganze, Qiangtang, Lhasa, and Tethyan Himalaya (Indian 

Plate) (Chu and others, 2006). These terranes are separated by three 

sutures: the Jinsa, the Bagong-Nujiang, and the Yarlung-Tsangpo 

(fig. 5). The Jinsa suture was formed during the closure of the 

Paleotethyan ocean in the Permian. The Bagong-Nujiang suture 

was formed by the closure of the Bagong (Tethyan) ocean in middle 

Jurassic time. The Yarlung-Tsangpo suture is the interface along 

which the Neotethyan ocean achieved final closure, as the Indian 

plate collided with Eurasia during Paleocene through Eocene time.

Each of these ocean closures terminated a continental-margin 

volcanic arc. The Permian and Middle Jurassic arcs are described 

in other chapters of this assessment. The late Mesozoic arc rocks 

north of the Yarlung-Tsangpo suture are described below.

The collision of the Indian Plate with Eurasia began in 

the west, in modern India and Pakistan, at about 65 Ma. As 

convergence progressed, the suture closure moved progressively 

eastward, and near the end of the Eocene, the amalgamation was 

complete. Previously, the strain of Indo-Asian convergence 

was accommodated primarily by crustal thickening and uplift 

4 5 6 7 8 

0 

20 

40 

60 

80 

100 

Log contained copper, in tons 

Proportion of deposits, in percent 

Worldwide model 

Tibetan Plateau deposits 

Tibetan Plateau deposits

 under active development 

EXPLANATION

Qulong

Yulong

Jiama

Xietongmen/Newtongmen

Malasongduo

Duoxiasongduo

Mangzhong

Gegongnong

Zhanaga

Machanqing

Xifanping

Figure 4. Cumulative frequency plot showing tonnages of Tibetan 

Plateau porphyry copper deposits compared to worldwide deposits 

from the grade-tonnage model of Singer and others (2008).
8 Porphyry Copper Assessment of the Tibetan Plateau, China

D

D

D

D

D

84°E 96°E

30°N

24°N

0 100 200 300 400 500 600 KILOMETERS

0 100 200 300 MILES

EXPLANATION

Porphyry copper deposit

Porphyry copper prospect

Suture or other structure

Boundary of Tibetan Plateau

Projection: Asia North Albers Equal Area Conic

central meridian 90° E; latitude of origin 30° N

Source for shaded relief (accessed March 8th, 2011): 

http://services.arcgisonline.com/v92/

ESRI_ShadedRelief_World_2D

D Related prospect

Chinese provincial boundaries

XIZANG

SICHUAN

QINGHAI

YUNNAN

GANSU

XINJIANG

CHINA

INDIA

MYANMAR

VIETNAM

NEPAL

BANGLADESH

(INDIA CONTINENTAL PLATE)

TETHYAN HIMALAYA TERRANE

INDOCHINA TERRANE

LHASA

 TERRANE

QIANGTANG

TERRANE

SONGPAN-GANZE

TERRANE

Yarlung-Tsangpo suture

Jinsa suture

 Bagong-Nujiang suture

Sanjiang-Red River fault zone

of the Tibetan Plateau. Subsequently, the initiation of the left-lateral 

Sanjiang-Red River Fault Zone accommodated half or more of this 

strain by permitting the eastward extrusion of the Indochina terrane 

(Harrison and Yin, 2004). Most of the porphyry copper deposits in 

Tibet formed after the accretion of the Indian Plate to Eurasia.

Different authors have diverse opinions about the Cenozoic 

tectono-magmatic history of the region. Most of the controversy 

is about the chronologic details, which is not surprising as, in 

the last decade, dozens of new radiometric age determinations 

have been reported each year. For the purposes of this discussion, 

we subdivide the Cenozoic tectono-magmatic history into three 

periods (following Hou and Cook, 2009): 1) main-collisional 

(Paleocene and Eocene, about 65–41 Ma), 2) late-collisional 

(Eocene and Oligocene, about 41–26 Ma, and 3) post-collisional 

(Miocene and younger, about 26 Ma to the present).

Magmatic rocks associated with the main-collisional period 

range from I-type calc-alkaline rocks north of the YarlungTsangpo suture (Gangdese batholith; Ji and others, 2009) that 

constitute the end stages of arc magmatism associated with the 

subduction of Tethyan oceanic crust to collision-related S-type 

Figure 5. Map showing terranes and bounding 

faults and sutures of the Tibetan Plateau.

muscovite-bearing granites, mostly found south of the YarlungTsangpo suture where they intrude the Indian plate.

Late-collision stage (Eocene through Oligocene) magmatic 

rocks (primarily plutonic) are mostly high-K calc-alkaline and 

shoshonitic rocks emplaced between the Jinsa and BagongNujiang sutures. Further south, along and east of the Jinsa suture 

and the Red River Fault Zone, most late-collisional rocks are 

alkaline, and include lamprophyres and carbonatites.

In the post-collision stage (Miocene and younger), magmatic 

rocks range from high-K calc-alkaline and shoshonitic rocks 

of the Gangdese porphyry belt to ultrapotassic rocks that are 

widespread on the Tibetan Plateau to leucogranites along the 

Yarlung-Tsangpo suture.

Igneous Provinces

Four major igneous provinces have formed on the Tibetan 

Plateau since the final accretion of the Indian Plate and the 

end of subduction (fig. 6): the Jinsa-Ailaoshan shoshonitic to 

alkaline igneous province, the Gangdese shoshonitic igneous 
Tectonic Setting 9

province, the Tibetan potassic-ultrapotassic igneous province, and 

a peraluminous igneous province. The peraluminous province is 

located primarily south of the Yarlung-Tsangpo suture, within the 

Indian Plate. Since there are no porphyry or other copper-gold 

deposits associated with the peraluminous rocks, they are not 

discussed further.

Jinsa-Ailaoshan Shoshonitic to Alkaline Igneous 

Province

Cenozoic igneous rocks crop out along the entire length of the 

Jinsa suture and Sanjiang-Red River Fault Zone from northwestern 

Tibet into northern Vietnam (figs. 5, 6). Ages of the rocks range 

from Eocene (about 50 Ma) to recent. The rocks in the northwest 

part of the belt are commonly referred to as the Yulong belt, 

whereas those to the south are usually termed the Ailaoshan belt.

Eocene igneous rocks of the Yulong belt formed during 

continental-scale strike-slip faulting during the late-collision stage, 

primarily between about 46 and 35 Ma. They were emplaced into 

D

D

D

D

D

84°E 100°E

34°N

26°N

0 100 200 300 400 500 600 KILOMETERS

0 100 200 300 MILES

Potassic/Ultrapotassic

igneous province

Gangdese porphyry belt Gangdese porphyry belt

Yulong porphyry belt Yulong porphyry belt

Ailoshan porphyry belt

Gangdese shoshonitic

igneous province

Jinsa-Ailoshan

shoshonitic to alkaline

igneous province

Peraluminous

igneous province

XIZANG

SICHUAN

QINGHAI

YUNNAN

GANSU

XINJIANG

CHINA

INDIA

MYANMAR

VIETNAM

NEPAL

BANGLADESH

BHUTAN

Projection: Asia North Albers Equal Area Conic

central meridian 95° E; latitude of origin 30° N

Source for shaded relief (accessed March 8th, 2011): 

http://services.arcgisonline.com/v92/

ESRI_ShadedRelief_World_2D

EXPLANATION

Porphyry copper deposit

Porphyry copper prospect

D Related prospect

Boundary of Tibetan Plateau

Figure 6. Map showing igneous provinces of the Tibetan Plateau. Chinese provincial boundaries

the Qiangtang terrane, mostly between the Jinsa and Bagong-Nujiang 

sutures. The Qiangtang terrane is characterized by Precambrian 

crystalline rocks overlain by late Paleozoic shallow marine 

rocks and Mesozoic carbonate and clastic rocks. The crust in the 

Qiangtang terrane is 50 to 60 km in thickness—thinner than that 

of the Lhasa terrane to the south (70 to 80 km) (Hou and Cook, 

2009). The emplacement of many of the plutons in the belt may 

be controlled by stepover extensional faults that formed between 

the major strike-slip faults in a transpressional regime (Hou and 

others, 2011).

Yulong Porphyry Belt

Igneous rocks in the Yulong porphyry belt are mostly 

intrusive, though a few volcanic remnants remain. They are best 

characterized as high-K calc-alkaline, although they have also 

been termed shoshonitic and adakitic by various authors. The 

following petrologic description is based primarily on the work 

of Jiang and others (2008), who made a comprehensive study of 
10 Porphyry Copper Assessment of the Tibetan Plateau, China

igneous rocks from much of the Yulong porphyry belt. Most of the orebearing porphyries are monzogranites and have silica contents between 

67 and 72 percent. The Mamupu igneous center (fig. 1) in particular 

is more alkaline, and contains syenites with silica contents around 64 

percent. High total alkali contents in most analyses indicate shoshonitic 

compositions. Yttrium contents are low, generally less than 20 ppm, 

and strontium is relatively high (500–2,000 ppm). Niobium is very 

low, mostly less than 15 ppm. Total rare-earth element (REE) contents 

are high, but rare-earth patterns are relatively gentle, with samarium/

ytterbium (Sm/Yb) ratios of 5 to 8. Europium anomalies are generally 

absent. Isotopically, the analyses show moderate crustal contributions; 

87Sr/86Sr ranges from 0.7055 to 0.7073, and eNd values range from -2.0 

to -4.1.

The magmas were strongly oxidized. The rocks are uniformly 

magnetite-bearing and Liang and others (2009) report that sulfate 

is the dominant sulfur species in early-formed fluid inclusions in 

magnetite and quartz. Mg numbers of biotites in these rocks range 

from 0.53 to 0.64 and the Fe3+/Fe2+ ratios are mostly greater than 

one (Jiang and others, 2008). Additional evidence for oxidation 

is given by Liang and others (2006) who showed that ore-bearing 

porphyries in the Yulong porphyry belt have average Ce4+/Ce3+

ratios in zircon of 200 to 300, in contrast to barren porphyries 

(ratios < 120) in the region.

Based on geochemical and isotopic data, Jiang and others 

(2008) have suggested that the source rocks for the Yulong belt 

magmas were probably garnet- and phlogopite-bearing pyroxenites, 

and that the melting occurred at depths near 100 km. They suggest 

that the melting of this metasomatized mantle was initiated by 

asthenospheric upwelling beneath the large trans-crustal strike-slip 

faults that define the tract. Initial magmatic temperatures were very 

high (>1200° C) and the magmas must have ascended rapidly. 

Jiang and others (2008) and Hou and others (2003, 2005) stress that 

plutonism is a response to the transtensional environment along 

major sutures that bound the tract.

Ailaoshan Porphyry Belt

Further south, most Cenozoic igneous rocks are decidedly 

more alkaline and are related to strike-slip faulting during the 

late-collision stage. The rocks range in age from about 40 Ma to 

about 26 Ma (Deng and others, 1998), slightly younger than the 

rocks in the Yulong belt to the north. They are emplaced along the 

Ailaoshan-Red River Fault Zone (the southern extension of the 

Jinsa suture), which forms the boundary between the Indochina 

plate and the South China craton, and which marks the suture 

between them (Wang and others, 2001; Guo and others, 2005). The 

Ailaoshan-Red River structure is a strike-slip fault zone that has 

accommodated much of the strain of the Indo-Asian collision since 

the Paleocene, and there are numerous subparallel strands of this 

fault. The igneous rocks also extend several hundred kilometers 

eastward onto the South China craton. In addition to the silicate 

rocks, a group of REE-bearing carbonatite complexes, with ages 

between about 40 and 10 Ma is found along the eastern margin of 

the province (Hou and others, 2009).

As in the Yulong porphyry belt to the north, the igneous rocks 

are mostly porphyritic intrusions, though a few volcanic rocks 

are present. The majority of the plutons here are composed of 

syenite, with lesser numbers of granite and monzonite plutons, as 

well as numerous small bodies of mafic alkaline rock (Deng and 

others, 1998; Wu and others, 2005; Guo and others, 2005). Traceelement data for these rocks are scarce, but Deng and others (1998) 

summarize their data by reporting that the rocks are enriched in Rb, 

Sr, Ba, Zr, and Y. Analyses for a single unmineralized pluton (Wu 

and others, 2005) are consonant with this generalization. Chondritenormalized rare-earth patterns are relatively flat, with minor orno

Eu anomalies (see Peng and others, 1998, for patterns from the 

Machangqing (fig. 1) porphyry copper deposit). Isotopically, 

the rocks show moderate crustal contributions; most 87Sr/86Sr 

ratios range from about 0.705 to 0.708 and most eNd values range 

from -1 to -5 (Deng and others, 1998). At least at Machangqing 

(fig.1), magnetite is present in the early, high-temperature potassic 

alteration assemblages (Peng and others, 1998).

Based on trace-element and isotopic modeling, Guo and 

others (2005) present a compelling model for the origin of these 

alkaline rocks as products of the melting of metasomatized mantle 

at depths near 100 km. Hu and others (2004) studied He and Ar 

isotopes of samples from Machangqing and from some of the 

nearby alkaline-rock-related gold deposits and concluded that 

the plutons were mantle-derived. The trigger for the melting that 

formed alkaline rocks in the Ailaoshan belt was probably the 

movements on the large trans-crustal strike-slip faults that bound 

the area (Hou and others, 2005).

Gangdese Shoshonitic Igneous Province

Within the Lhasa terrane, in the southern part of the Tibetan 

Plateau, a suite of distinctive post-collisional plutons and small 

exposures of volcanic rock form a 1,500 km-long belt that is 

subparallel to the Yarlung-Tsangpo suture (fig. 5, 6). The report by 

Guo and others (2007) is the source of most of the petrologic data 

summarized here. The oldest rocks are Oligocene in age (about 

26 Ma) and the youngest are Miocene (about 10 Ma); most of the 

plutons have ages between 18 and 12 Ma. Individual intrusions are 

small, most with areas < 100 km2, and are located within northsouth-trending grabens that formed during east-west extension. 

There are several dozen igneous centers, although all have probably 

not been catalogued, especially in the western part of the belt.

The rocks are mildly alkaline, and are primarily composed of 

quartz monzonite and monzonite. They are about equally divided 

between high-K calc-alkaline and shoshonitic compositions. The 

large-ion lithophile elements (Rb, K, Sr, Pb), along with U and Th, 

are highly enriched whereas the high field strength elements (Nb, 

Ta, Ti, HREE, Y) are strongly depleted. Rare-earth patterns show 

moderate slopes (La/Yb ratios of 20 to 50) and have minor or no 

Eu anomalies. The rocks show moderate crustal contributions; most 

87Sr/86Sr ratios range from 0.7050 to 0.7075 and most eNd values 

range from -6 to +5 (Hou and others, 2009).

Trace-element and isotopic modeling show that both 

melting of previously subducted oceanic crust and melting 

of mafic to intermediate metaigneous lower crustal rocks 

are permissive sources for these rocks. There is an emerging 

consensus that these rocks were formed from mantle-derived 
Assessment Data 11

melts that have assimilated important amounts of lower crustal 

material, as well as some upper crustal material during ascent 

(Hou and others, 2009; Hou and others, 2011). This conclusion 

is based primarily on the position of these rocks in the 87Sr/86Sr 

vs. eNd diagram. The cause of the melting is ascribed to 

upwelling asthenosphere, with the trigger for emplacement being 

the uplift and extension of the upper crust of the Tibetan Plateau. 

Perhaps the contemporaneous alkaline mantle-sourced melts 

described in the next section also provided heat for the formation 

of the shoshonites in the Gangdese belt (Guo and others, 2007).

Tibetan Potassic/Ultrapotassic Igneous Province

Post-collisional potassic and ultrapotassic igneous rocks, many 

of them volcanic, are distributed throughout the northern part of 

the Tibetan Plateau, and are described in a comprehensive review 

by Guo and others (2006). These rocks formed between about 45 

Ma and the present, and are found in the Lhasa, Qiangtang, and 

Songpan-Ganze terranes, where they are closely associated with 

major thrust and strike-slip faults, and with pull-apart basins. They 

have relatively small volumes (mostly thin flows and less than 1,000 

km2

 in extent), but more than 25 localities have been catalogued.

These rocks are notably alkaline, ranging from mildly shoshonitic to ultrapotassic; rock types include trachyte, trachyandesite, 

trachybasalt, phonolite, tephriphonolite, phonotephrite, and tephrite. 

Guo and others (2006) postulate that they formed by partial melting 

of enriched asthenospheric mantle, and were modified only slightly 

by crustal contamination, as indicated by extensive strontium, lead, 

and neodymium isotopic data. The trigger for this melting is interpreted to be prolonged northward underthrusting of Indian continental lithosphere beneath the Tibetan Plateau, resulting in the upwelling of hot asthenosphere. Magma likely ascended to the surface via 

deep transcrustal faults. There is no known porphyry copper style 

mineralization associated with these rocks, which formed in ways 

somewhat distinct from the other two largely contemporaneous 

igneous provinces (Gangdese and Jinsa-Ailaoshan).

The Adakite Issue

Adakite is a term that is commonly used in the Chinese 

literature to mean igneous rocks with trace-element compositions 

that suggest an origin by melting of metabasaltic crust at pressures 

high enough to stabilize garnet, probably at depths of as much 

as 100 km (Xiao and Clemens, 2007). The most diagnostic 

parameters are high Sr/Y (> 20) and steep chondrite-normalized 

REE patterns (La/Yb >20). Although the original definition (Defant 

and Drummond, 1990) was closely linked to origin through 

direct melting of a subducting oceanic slab, the term has been 

subsequently applied to rocks from other petrotectonic settings. 

Indeed, in a comprehensive review that documents the evolution 

of the meaning of the term, Castillo (2006) pointed out that there 

is no single model for the origin of the rocks defined by these 

geochemical criteria.

Most of the rocks associated with the Tibetan porphyry 

copper deposits have been classified as adakites and a correlation 

between porphyry copper deposits and adakitic compositions has 

been noted in many parts of the world (Thiéblemont and others, 

1997; Mungall, 2002). Direct melting of the slab, however, has 

been shown to be unsatisfactory as a unique factor in the genesis of 

porphyry copper deposits (Richards and Kerrich, 2007). Although 

we embrace the idea that plutons that give rise to porphyry copper 

deposits commonly have high Sr/Y and La/Yb, we avoid the use of 

the term adakite whenever possible in this assessment.

Assessment Data

Geologic Maps

Geologic maps at a variety of scales were used during the 

assessment. The conceptual basis for the generalized versions of 

the tracts is the discussion by Hou and Cook (2009) outlining the 

magmatic history of the region. As a basis for tract delineation, we 

used unpublished digital versions of geological maps of the Chinese 

provinces published as part of a collection of Geologic Memoirs by 

the Chinese Ministry of Geology and Mineral Resources from 1984 

through 1993. The resulting digital geologic map does not always 

reflect the most recent radiometric age determinations or petrologic 

studies of the rocks in the tract; in many cases, ages of the igneous 

rocks are not accurately known. Many of the small plutons that host 

porphyry copper deposits in the region are too small to be depicted 

on that map and we digitized the location of additional plutons based 

on available small-scale schematic maps (Guo and others, 2006, 

2007; Qu and others, 2007; Hou and others, 2009).

In addition, we consulted the digital geologic map of China 

based on the 1:2,500,000 scale map by the China Geological 

Survey (2004a). Although this map is at a smaller scale than those 

in the geologic memoirs, it incorporates significant new petrologic 

and radiometric age data gathered in the 1990s for the new maps of 

the Tibetan Plateau (Wang and others, 2004; Zhai, 2004).

Mineral Occurrence Data

A global database of porphyry copper deposits and prospects 

published by Singer and others (2008) was supplemented 

with other global and regional mineral occurrence databases, 

including that of the Geological Survey of Canada (Natural 

Resources Canada, 2010; Kirkham and Dunne, 2000). In addition, 

commercially available databases (InfoMine, Intierra, Metals 

Economic Group), technical reports, company websites, and 

geologic literature were consulted. The U.S. Geological Survey 

Mineral Resources Data System (MRDS), an online searchable 

database, also includes information on mines, prospects, and 

mineral occurrences worldwide.

Sites were classified as deposits (grade and tonnage welldelineated) or prospects (incompletely characterized with respect 

to grade and tonnage) on the basis of recent published literature. 

The deposit-type classification of some sites is ambiguous due 

to insufficient information. Deposits and prospects that could be 

classified with certainty as porphyry copper or porphyry-copperrelated are included in the database for this report (appendix D). 
12 Porphyry Copper Assessment of the Tibetan Plateau, China

Distributions of gold placers, copper and copper-gold skarns, and 

epithermal precious-metal deposits, as well as unclassified copper and 

gold occurrences, were considered during the assessment but generally 

are not included in the database. Some skarns were included if it seemed 

likely that an associated porphyry system could be plausibly inferred.

Geochemical Data

Stream-sediment geochemistry has been very important 

for mineral exploration in China. Begun in 1978, the Regional 

Geochemistry-National Reconnaissance project has now covered 

more than 6 million km2 of the territory of China, and has been 

directly responsible for the discovery of hundreds of mineral 

deposits, including several porphyry copper deposits (Xie and 

others, 2008). Although the data themselves are not available to the 

general public, the China Geological Survey has made numerous 

national maps for specified elements available on the internet. 

D

D

D

D

D

84°E 92°E 100°E

30°N

24°N

0 100 200 300 400 500 600 KILOMETERS

0 100 200 300 MILES

Projection: Axia North Albers Equal Area Conic; 

central meridian 95° W; latitude of origin 30° N

Source for shaded relief (accessed March 8th, 2011): 

http://services.arcgisonline.com/v92/

ESRI_ShadedRelief_World_2D

EXPLANATION

Porphyry copper deposit

Porphyry copper prospect

D Related prospect

Tract outline

Figure 7. Map showing grid generated from stream-sediment geochemical data for copper in western China, along with permissive 

tract boundaries. After China Geological Survey (2010). Isolated copper anomalies may be related to porphyry deposits. Large 

continuous anomalies like those in the southeast quarter of the map area are likely to be related to bulk rock geochemistry (in this case, 

Cu-rich flood basalts). Values represented on the map range from 4 ppm (dark blue) through 30–35 ppm (yellow) to >150 ppm (dark red).

Maps (China Geological Survey, 2010) that show the distribution 

of copper (fig. 7) and bismuth were used to help refine the tracts 

defined in this study.

ASTER Data

Remote sensing data is also helpful in determining the extent of 

mineralized regions because hydrothermally altered areas associated 

with porphyry copper deposits can be identified. It is particularly 

useful in an arid region with only sparse vegetation like the Tibetan 

Plateau. A reconnaissance study of selected areas on the Tibetan 

Plateau was conducted using methods described by Mars and Rowan 

(2006). Preliminary results of this study indicate that large areas in 

the western part of the Gangdese tract exhibit abundant argillic and 

phyllic alteration, which increases the likelihood that the western part 

of the tract contains undiscovered porphyry copper deposits. Two 

illustrative examples of the ASTER data are shown in figure 8.
The Assessment Process 13

Figure 8. Map showing hydrothermally altered areas identified by ASTER. A, Nimu project area, eastern Gangdese belt; B, Poorly explored 

area in western part of Gangdese tract. Red pixels represent phyllic alteration, yellow pixels represent argillic alteration. Areas like those in B are 

common in southwestern Tibet.

Other Data

Global aeromagnetic data covers most of Southeast Asia 

(National Geophysical Data Center, 2009). However, the data 

are of limited use in tracing the subsurface extent of magmatic 

arcs as a result of coarse flight-line spacing relative to the 

complex geology of the region. The published 1:5,000,000-

scale aeromagnetic map of China (China Geological Survey, 

2004b) is similarly of limited use.

Exploration History

In many parts of the world, porphyry copper exploration has 

been cyclic in response to changing global economic trends and 

the evolution of local infrastructure development. Exploration for 

porphyry copper deposits on the Tibetan Plateau is in its initial 

cycle. The porphyry copper deposit model was not well-known 

in China until the 1960s, when scientific and industrial activity 

was renewed after a long period of warfare and internal turmoil. 

Access to the region was also severely limited, due to limited 

infrastructure. Subsequently, basic geologic mapping and detailed 

geochemical and geophysical surveys have been completed, 

resulting in the discovery of numerous porphyry copper deposits 

and prospects (Wang and others, 2004; Xie and others, 2008). A 

few international companies based outside of China have operated 

in the region since about 1990, but most of the exploration 

activity has been conducted by Chinese companies and is not well 

documented in the English language literature.

The Assessment Process

A preliminary workshop attended by USGS and CGS 

scientists was held in Kunming, China, in September of 2005. 

At this meeting, preliminary tracts were delineated using nondigital methods. The CGS published the outlines of these tracts 

along with an associated quantitative resource assessment 

based on them (Yan and others, 2007). Meanwhile, assessment 

technology continued to evolve, and in 2009, the USGS decided 

to apply the standardized procedures adopted by the GMRAP, and 

updated the assessment. Preliminary versions of this assessment 

were presented to the Coordinating Committee for Geoscience 

Programmes in East and Southeast Asia (CCOP) workshop in 

Busan, South Korea, in the spring of 2010. The assessment was 

further refined after internal USGS review.

Three-Part Assessment

This assessment was conducted using methods, procedures, 

and models that support what have come to be known as threepart assessments. The three parts that are integrated to create the 

assessment are (1) delineation of permissive tracts, according to 

the type of mineral deposits permitted by geology, (2) estimation 

of the amount of metal in typical deposits by using gradetonnage models, and (3) probabilistic estimation of the number 

of undiscovered deposits by subjective methods (Singer, 2007a; 

Singer and Menzie, 2010).

A permissive tract for porphyry copper deposits is delineated 

as a geographic area that includes intrusive and volcanic rocks 

EXPLANATION

Porphyry copper prospect

Argillically altered rocks

Phyllically altered rocks

Projection: Lambert Azimuthal Equal 

Area; Central meridian: 95° E; Latitude 

of origin: 30° N

Source for imagery (accessed 

March 8th, 2011): http://services.

arcgisonline.com/v92/ESRI_Imagery

_World_2D

10 KILOMETERS

2.5 5 MILES

0

0

52.5 7.5

79 45'E

33 N

33 15'N ° °

°

89°50'E 90°0'E 90°10'E

29°40'N

29°30'N

Gangjiang Gangjiang

Tinggong

Dubuqu

Zongxun

Tinggong

Dubuqu

Zongxun

0 2 4 6 8 KILOMETERS

0 2 4 MILES

A B
14 Porphyry Copper Assessment of the Tibetan Plateau, China

of specified ranges of composition and age that are part of a 

magmatic arc. These arcs have been traditionally related to 

convergent plate margins, but the Cenozoic magmatic arcs related 

to porphyry copper deposits on the Tibetan Plateau formed after 

subduction ceased. The tract generally is bounded by the outline 

of the magmatic arc as depicted at the scale of the maps available 

for tract delineation and may include areas covered by younger or 

structurally overlying materials that are less than 1 km thick. For 

these Cenozoic tracts on the Tibetan Plateau, many of the igneous 

rocks closely associated with porphyry copper formation are not 

depicted on available geologic maps. In a number of cases, we 

used conceptual (tectonic) features to subjectively define tract 

boundaries, rather than relying directly on digital geologic maps.

Frequency distributions of pre-mining tonnages and average 

grades of thoroughly explored deposits are used as models for 

grades and tonnages of undiscovered deposits (Singer, 1993). 

Models are constructed from average grades and tonnages 

(including both measured and inferred resources) based on the total 

production, reserves, and resources at the lowest possible cutoff 

grade, as described by Singer and others (2008). 

Numbers of undiscovered deposits at various quantiles 

(degrees of belief) are estimated by an assessment team of experts 

using a variety of strategies, such as counting the number and 

ranking the favorability of significant prospects, and comparing 

the spatial density of known deposits and expected undiscovered 

deposits to that of known deposits in similar, well-explored regions 

(Singer, 2007b). Probable amounts of undiscovered resources are 

then estimated by combining estimates of numbers of undiscovered 

deposits with grade and tonnage models, using a Monte Carlo 

simulation process (Root and others, 1992; Bawiec and Spanski, 

2012; Duval, 2012).

Tract Delineation

The geology-based strategy that is commonly used for 

porphyry copper tract delineation within GMRAP is described 

here. Digital geologic data were processed in a GIS using ArcMap 

software, as follows:

Regional-scale maps and geologic literature were used to 

identify the fundamental units for tract delineation—magmatic arcs 

or belts of igneous rocks of a given age range.

Digital geologic maps were then used to select map units to 

define preliminary tracts permissive for porphyry copper deposits. 

Igneous map units were subdivided by age groups and classified 

as permissive or non-permissive based on lithology. Permissive 

rocks include calc-alkaline and alkaline plutonic and volcanic 

rocks. Non-permissive rocks include, for example, ultramafic 

assemblages, ophiolites, highly evolved granites, peraluminous 

granites, and pillow basalts.

Typically, a 10-, 15-, or 20-km buffer was then 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 porphyry copper deposits and significant associated prospects. 

The buffer accounts for uncertainties in the cartographic position 

of mapped boundaries, as well as possible unexposed or unmapped 

permissive rocks.

After buffering, available data on mineral deposits and 

occurrences, locations of dated igneous rock samples, and 

geophysical and geochemical information were examined to 

identify previously unrecognized 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 in accord 

with post-mineral fault boundaries. In some cases, more detailed 

geologic maps were used to resolve tract boundary issues or 

available schematic map illustrations from the literature were 

incorporated to augment the existing digital maps.

Areas where post-mineral volcanic centers, depositional 

basins, and other forms of cover judged to exceed 1 km in thickness 

were excluded from the tracts. Intrusions younger than the 

designated tract age were also excluded.

Because many of the intrusions that define the tracts on the 

Tibetan Plateau are so small that they are not depicted on the 

available digital geologic maps, and because the igneous belts are 

believed to be controlled by deep trans-crustal faults, some of the 

major tract boundaries were subjectively delineated to include the 

entire area judged to be permissive.

Permissive Tracts for Porphyry Copper Deposits 

on the Tibetan Plateau

Based on the geologic data evaluated, three porphyry copper 

permissive tracts were delineated on the Tibetan Plateau (fig. 9). 

Table 3 contains comparative information about each of the tracts. 

Brief summaries of the tracts are included here, but the detailed 

rationale for tract delineation is in appendixes A, B, and C.

Yulong Tract

The Yulong tract (142pCu8710), with an area of about 

112,000 km2, is defined by a curvilinear belt of Eocene 

and early Oligocene (46–35 Ma) intrusions that are mostly 

shoshonitic and intermediate to felsic in composition and are 

part of the Jinsa-Ailaoshan igneous province. They formed in a 

transpressional environment closely related to the two sutures 

(Jinsa and Bagong-Nujiang) that bound the tract; they may be 

localized by stepover extensional faults that formed between 

the two sutures. The tract includes six known deposits (Yulong, 

Zhanaga, Mangzhong, Duoxiasongduo, Malasongduo, and 

Gegongnong; table 1) and at least six prospects (appendix A).

Dali Tract

The Dali tract (142pCu8711), with an area of about 

97,000km2, is defined by a group of late Eocene and Oligocene 

(40–26Ma) porphyritic, distinctly alkaline intrusions that are also

part of the Jinsa-Ailaoshan magmatic province. The intrusions are 

both felsic and mafic, and are accompanied by sparse volcanic 

rocks that were emplaced along and to the east of the AilaoshanRed River shear zone and strike-slip fault. The tract includes two 

known deposits, Xifanping (32 Ma; table 1) and Machanqing 
The Assessment Process 15

84°E 92°E 100°E

30°N

24°N

Lhasa

Kunming

Chengdu

Calcutta

Varanasi

Kathmandu

!

!

!

!

!

!

CHINA

INDIA

MYANMAR

NEPAL

BANGLADESH

BHUTAN

0 100 200 300 400 500 600 KILOMETERS

0 100 200 300 MILES

Projection: Asia North Albers Equal Area Conic

central meridian 95° E; latitude of origin 30° N

Source for political boundaries: Boundaries and 

Sovereignty Encyclopedia, U.S. Department of State, 

Office of the Geographer and Global Issues 

Source for shaded relief (accessed March 8th, 2011): 

http://services.arcgisonline.com/v92/ESRI_ShadedRelief_World_2D

EXPLANATION

Assessed porphyry copper tract

142pCu8712 - Gangdese

Assessed porphyry copper tract

142pCu8710 - Yulong

Assessed porphyry copper tract

142pCu8711 - Dali

Table 3. Permissive tracts for porphyry copper deposits on the Tibetan Plateau. 

Appendix Coded_Id Tract Name Countries Area (sq. km) Geologic feature assessed

A 142pCu8710 Yulong China 112,470

A curvilinear belt of Eocene igneous rocks formed in an 

extensional, post-subduction environment in southwest 

China during the collision between India and Asia

B 142pCu8711 Dali China and

Vietnam 96,670

An assemblage of Eocene and Oligocene igneous rocks 

formed in an extensional, post-subduction environment in 

southwest China during the collision between India and 

Asia

C 142pCu8712 Gangdese China 239,860

A belt of Miocene igneous rocks formed in an extensional, 

post-subduction environment in southwest China after the 

collision between India and Asia

Figure 9. Map showing permissive tracts for porphyry copper deposits on the Tibetan Plateau.
16 Porphyry Copper Assessment of the Tibetan Plateau, China

(34–35 Ma; table 1), and as many as seven prospects in various 

stages of exploration and development (appendix B).

Gangdese Tract

The Gangdese tract (142pCu8712), with an area of about 

240,000 km2, is defined by a narrow 1,500-km-long belt of Miocene 

(22–12 Ma) high-K calc-alkaline to shoshonitic porphyryitic 

intrusions that formed in an east-west extensional environment and 

that are part of the Gangdese igneous province. The tract includes 

three deposits (Qulong, Xietongmen/Newtongmen, and Jiama; 

table 1) and more than 20 additional prospects in various stages 

of exploration and development (appendix C). Several of these 

prospects have been at least partially explored by drilling. Most 

discoveries have been in the eastern part of the tract, but discoveries 

are likely in the western, poorly explored part.

Estimating Numbers of Undiscovered Deposits

The assessment team estimated numbers of undiscovered 

deposits in each tract at various probabilities (degrees of belief). 

Strategies for estimation included counting the number and ranking 

the favorability of significant prospects, and comparing the spatial 

density of known deposits and expected undiscovered deposits to that 

of known deposits in similar, well-explored regions (Singer, 2007b).

Assessment team members evaluated the available data 

and made individual, subjective estimates of the numbers of 

undiscovered porphyry copper deposits by 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 three specified levels of 

certainty (90 percent, 50 percent, and 10 percent). For example, on 

the basis of all available data, a team member might estimate that 

there was a 90-percent chance of 1 or more, a 50-percent chance 

of 5 or more, and a 10-percent chance of 10 or more undiscovered 

deposits in a permissive tract. The differences between individual 

estimates were discussed and evaluated before a single team 

estimate was agreed upon for each tract.

The estimates were converted to an expected (mean) number 

of deposits and standard deviation using an algorithm developed 

by Root and others (1992). This algorithm can be described by the 

following general equations (Singer and Menzie, 2005), which 

are used to calculate a mean expected number of deposits (λ) 

and a standard deviation (sx) based on estimates of numbers of 

undiscovered deposits predicted at specified quantile levels5

(N90 = 90 percent level, N50 = 50 percent level, etc.):

λ = 0.233 N90 + 0.4 N50 + 0.225 N10 + 0.045 N05 + 0.04 N01 (1)

sx = 0.121 – 0.237 N90 – 0.093 N50 + 0.183 N10 + 0.073 N05 + 0.123 N01 (2) 

For the example given above (N90 = 1; N50 = 5; N10 = 10), λ = 5.2 and sx = 3.2.

Another useful parameter for reporting uncertainty 

associated with an estimate is the coefficient of variation (Cν), 

defined as:

 Cν = sx / λ (3)

The coefficient of variation is often reported as percent 

relative variation (100 × Cν).

The final set of undiscovered deposit estimates reflects 

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 Spanski, 2012; Duval, 2012), based on the original Mark3 

computer program described by Root and others (1992), to 

provide a probabilistic estimate of amounts of resources that 

could be associated with undiscovered deposits.

The rationales for individual tract estimates are discussed 

in the appendixes. Recent literature, company websites, and 

technical reports for exploration projects were examined 

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. 

In some cases, the number of significant porphyry copper 

prospects within a tract were counted as an important factor in 

estimation. Particular weight was given to prospects described 

as porphyry copper-related in published literature and recent 

exploration reports.

In addition, we considered the distribution of reported copper 

and gold occurrences of unknown type and placer gold workings. 

The level of exploration was also a factor in making estimates. In 

less well-explored areas, and areas with poor documentation of 

mineral occurrences, we were unable to use such methods, and the 

spread in estimates and relatively high coefficients of variations 

associated reflect the uncertainty associated with the estimates. 

We also considered the fact that much of the Tibetan Plateau is 

extremely remote, and lacks infrastructure.

Final team estimates of undiscovered deposits are 

summarized in table 4, 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. The assessment predicts a mean total of about 

39 undiscovered porphyry copper deposits in all tracts, many 

more than the 11 that have already been discovered.

Probabilistic Assessment Results

Probable amounts of undiscovered resources are 

estimated by combining estimates of numbers of undiscovered 

deposits with grade and tonnage models by using a Monte 

Carlo simulation (Root and others, 1992; Bawiec and Spanski, 

2012; Duval, 2012). Frequency distributions of tonnages and 

average grades of thoroughly-explored deposits are used as 

models for grades and tonnages of undiscovered deposits 

(Singer, 1993). Data for the models include the average grade 

of each metal or commodity of possible economic interest and 

5

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) 

are estimated use the N05 value N01.
Discussion 17

Table 4. Estimates of numbers of undiscovered porphyry copper deposits on the Tibetan Plateau.

[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; -, no estimate made; 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)]

Appendix Coded_Id Tract 

Name

Consensus undiscovered

deposit estimates Summary statistics Tract

Area

(km2

)

Deposit 

density

(Ntotal/km2)

Deposit density 

(Ntotal/100k km2

) N90 N50 N10 N05 N01 Nund s Cv

% Nknown Ntotal

A 142pCu8710 Yulong 3 6 18 18 18 8.5 5.7 67 6 14.5 112,470 0.00013 12.9

B 142pCu8711 Dali 2 6 18 18 18 8.3 5.9 72 2 10.3 96,670 0.00011 10.6

C 142pCu8712 Gangdese 9 13 50 50 50 22.3 15.7 71 3 25.3 239,860 0.00011 10.5

Table 5. 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 on the Tibetan Plateau.

[t, metric tons; Mt, million metric tons, n.a., not applicable (only means are additive)]

Appendix Coded_Id Tract

Name

Known resources Mean

undiscovered 

copper 

resources (t)

Median 

undiscovered 

copper 

resources (t)

Mean 

undiscovered 

gold

resources (t)

Median 

undiscovered 

gold

resources (t)

Mean

copper

(t)

gold

(t)

Undiscovered 

molybdenum 

resources (t)

Undiscovered 

silver

resources (t)

Rock

(Mt)

A 142pCu8710 Yulong 11,000,000 376 32,000,000 20,000,000 820 470 910,000 11,000 6,600

B 142pCu8711 Dali 490,000 42 26,000,000 15,000,000 1,900 1,200 150,000 8,600 5,200

C 142pCu8712 Gangdese 15,200,000 337 87,000,000 61,000,000 2,200 1,500 2,400,000 28,000 18,000

Total 26,700,000 755 145,000,000 n.a. 4,920 n.a. 3,460,000 55,000 29,800

the associated tonnage based on the total production, reserves, 

and resources at the lowest possible cutoff grade, as described 

by Singer and others (2008).

The Monte Carlo simulation yields estimates for the 

mean and median copper and gold contained in undiscovered 

deposits (table 5). Identified resources in the table refer to 

metal contained in well-delineated porphyry copper deposits 

only; the resource data are based on total production, plus 

measured, indicated, and inferred reserves and resources at the 

lowest cutoff grade reported. Identified resources may include 

substantial amounts of metal that have already been produced.

All three permissive tracts contain identified resources, 

although those in the Dali tract are considerably less than in 

the Yulong or Gangdese tracts. All of the tracts also contain 

porphyry copper systems that have been partially explored, 

but for which no reliable grade and tonnage estimates are yet 

available. Resources in deposits like these that have not been 

comprehensively drilled out are not included in the data for 

identified resources. These deposits were considered to be 

significant prospects with a high probability of representing 

deposits like those in the grade and tonnage models. An 

example is the Gangjiang deposit, where a near-surface oxide 

resource of 47,000,000 t of ore has been identified, but deep 

drilling of the sulfide part of the deposit has just begun.

Simulation results are reported at selected quantile 

levels, along with the mean expected 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 estimates 

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 that can be 

compared between tracts.

Discussion

This probabilistic assessment of undiscovered resources in 

undiscovered porphyry copper deposits on the Tibetan Plateau 

indicates that significant amounts of additional resources may 

be present (table 5). The mean estimate of undiscovered copper 

resources in the study area (about 145,000,000 t) is nearly 6 times 

the amount of copper present in identified porphyry resources 

(about 27,000,000 t). This is entirely plausible for an area that is 

in the early stage of exploration. In 2006, China’s reserve base 

was reported to be 30,700,000 t of copper and the identified 

copper resources were 70,500,000 t, contained in more than

1,000 identified mines, many of them small (Li, 2008). At the 
18 Porphyry Copper Assessment of the Tibetan Plateau, China

same time, annual consumption was nearly 5,000,000 t and 

growing rapidly. Thus, the undiscovered resources on the 

Tibetan Plateau may play an important role in meeting China’s 

copper supply needs in the short and medium term.

However, a significant part of these resources, if they 

are present, may be inaccessible or uneconomic. Results 

0

10

20

30

40

50

60

70

80

90

100

Yulong Dali Gangdese

Copper, million metric tons

Tract name

Tibetan Plateau 

Known copper resources

Mean estimate of undiscovered copper resources

Median estimate of undiscovered copper resources

Figure 10. Chart showing identified and undiscovered copper resources for permissive tracts on the Tibetan Plateau.

should be interpreted with due caution, as no economic 

filters have been applied to these results to evaluate what 

portion of the estimated undiscovered resources might be 

economic under various conditions. For each tract, identified 

resources are compared with mean and median estimates of 

undiscovered copper resources in figure 10.
References Cited 19

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Appendixes A–E
24 Porphyry Copper Assessment of the Tibetan Plateau, China

Appendix A. Porphyry Copper Assessment for Tract 142pCu8710, Yulong—China

Table A1. Summary of selected resource assessment results for tract 142pCu8710, Yulong—China.

[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)

2010 1 112,470 11,000,000 32,000,000 20,000,000

1

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

2

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

3

China Geological Survey, Beijing, China.

By Steve Ludington1, Jane M. Hammarstrom2, Gilpin R. Robinson, Jr.2, and Robert J. Miller1, based on 

contributions of Yan Guangsheng3

, Peng Qiuming3, Lian Changyun3, and Dennis Cox1

Deposit Type Assessed: Porphyry Copper

Deposit type: Porphyry copper

Descriptive model: Porphyry copper (Cox, 1986; John and others, 2010)

Grade and tonnage model: General porphyry copper (Singer and others, 2008)

Table A1 summarizes selected assessment results.

Location

The tract extends for about 1,100 kilometers (km), from southern Qinghai Province in China, through easternmost Xizang 

(Tibet) and a few kilometers into northernmost Yunnan (fig. A1). Much of the tract is quite narrow, but parts are as much as 160 

km wide. The tract is entirely within the Tibetan Plateau, and most of it is at altitudes exceeding 4,000 meters (m). Much of the 

southern part of the tract is coincident with the Ningjing Shan range, between the Mekong and Yangtze Rivers.

Geologic Feature Assessed

A curvilinear belt of Eocene igneous rocks that formed in a transtensional, post-subduction environment in southwest China 

during the collision between India and Asia.
Figure A1. Map showing tract location, known porphyry copper deposits, and significant porphyry copper prospects for tract 142pCu8710, Yulon

!

Yangtze

Mekong

XIZANG

QINGHAI

SICHUAN

YUNNAN

Seli

Jicuo

Yulong

Mamupu

ZhanagaXiariduo

Ridanguo

Mangzhong

Narigongma

Gegongnong

Malasongduo

Hengxingcuo

Duoxiasongduo

Lhasa

CHINA

INDIA

BHUTAN

92°E 100°E

34°N30°N

INDIA

80°E 

30°N10°N

0 50 100 150 200 KILOMETERS0 50 100 MILES

Political boundary source U.S. Department of State (2009)Projection: Asia North Albers Equal Area Conic;Central meridian 95° E; latitude of origin 30° N

EX

Por

Other pAssessetract 14Porphyrassociain grayPorphyrassociain gray
26 Porphyry Copper Assessment of the Tibetan Plateau, China

Delineation of the Permissive Tract

Geologic Criteria

The igneous rocks that define the Yulong tract formed 

during continental-scale strike-slip faulting that accompanied 

the late-collision stage of the accretion of India to Asia. They 

are emplaced into the Qiangtang terrane, between the Jinsa and 

Bangong-Nujiang sutures (fig. 5). The faults that bound the 

magmatic belt (Chesuo and Tuoba) are strike-slip faults that 

have accommodated the strain associated with the Indo-Asian 

collision since the Paleocene and numerous other strike-slip 

faults parallel the two main faults (Jiang and others, 2006). 

Emplacement of many of the plutons in the belt may have been 

controlled by stepover extensional faults that formed between 

these strike-slip faults in a transpressional regime (Hou and 

others, 2007b, 2011). The six known porphyry copper deposits 

and seven prospects in the tract were formed between about 46 

and 35 million years (Ma) ago. They are concentrated in the 

southeastern, better-explored, part of the tract (fig. A1). 

The igneous rocks are mostly intrusive, though a few 

volcanic remnants crop out. Most of them are best characterized 

as high-K calc-alkaline (Jiang and others, 2008), although they 

have also been termed shoshonitic and adakitic by various authors. 

They are uniformly magnetite-bearing (Liang and others, 2009a). 

The source rocks that were melted at depths near 100 km were 

probably garnet- and phlogopite-bearing pyroxenite.

As a basis for tract delineation, we used unpublished digital 

versions of the geological maps of Qinghai and Yunnan Provinces 

and Xizang (Tibet) Autonomous Region that were published by the 

Chinese Ministry of Geology and Mineral Resources in the early 

1990s (Bureau of Geology and Mineral Deposits of the Qinghai 

Province, 1991; Bureau of Geology and Mineral Deposits of the 

Yunnan Province, 1990; Bureau of Geology and Mineral Deposits 

of the Xizang Autonomous Region, 1993). The resulting digital 

geologic map does not always reflect the most recent radiometric 

age determinations or petrologic studies on the rocks in the tract. At 

the same time, many of the rocks have not been dated precisely nor 

studied extensively petrologically. In addition, most of the plutons 

associated with known deposits and prospects in the tract are less 

than a square kilometer in outcrop area, and thus are not shown on 

any of the regional maps nor are they included in the digital map.

The tract was defined on the basis of the Qiangtang 

terrane, bounded in most places by the Jinsa and BagongNujiang sutures and specifically, by the Chesuo and Tuoba 

faults (Jiang and others, 2006). The tract is bounded on 

the northwest by the extent of exposed plutonic rocks; the 

volcanic rocks further west are mostly ultrapotassic lavas (see 

Guo and others, 2006); any porphyry deposits that might exist 

in the western part of the Qiangtang terrane are likely to be 

concealed at depths greater than a kilometer.

After initial delineation, the limited available geophysical 

and geochemical information were examined to be sure we 

included any other evidence of unmapped permissive rocks or 

hydrothermal systems at shallow depths. A smoothing routine 

was applied to the resulting polygons, and the tract was trimmed 

by any terrane-bounding faults. We also excluded areas where 

Tertiary basins were judged to be deeper than 1 km by buffering 

inward 1 km from the margins of outcrops of post-mineral 

sedimentary rock and sediment. The tract is shown in Figure A1.

Known Deposits

Information was found for six known porphyry copper 

deposits in the tract (table A2). There are no accurate published 

coordinates nor detailed maps of most of the deposits, so all 

locations (other than Yulong, which is plainly visible on satellite 

imagery) are approximate. They were derived by interpolation of 

page-size maps and inference from satellite imagery.

The known deposits in the tract define a 150 km-long belt 

in the southern part of the tract (fig. A1). All plutons associated 

with the deposits have small outcrop areas (< 1 km2), and take 

the form of small pipe-like bodies. Most are composed of 

monzogranite, syenogranite, and alkali-feldspar granite, and they 

characteristically contain biotite as a prominent phenocryst (Hou 

and others, 2003; Gu and others, 2003). A general description of 

the Yulong belt is provided by Tang and Luo (1995).

Yulong, the largest deposit, and the most northerly, 

was first discovered in 1966 (Chen and others, 2009). 

Singer and others (2008) provide a resource number of 

850,000,000 metric tons (t) at 0.84 percent copper, 0.022 

percent molybdenite, and 0.35 grams per metric ton (g/t) gold 

(7,140,000 t of contained copper), although Wang and others 

(2010), who did a 3-D modeling study of the deposit, report a 

slightly smaller initial reserve of 6,570,000 tons of copper. A 

2006 press release claimed a prospective resource of around 

10,000,000 t of copper (Anonymous, 2006) and Wang and 

others (2010) confirm that number, calling it a “long-term” 

reserve. The deposit crops out at the surface, and a substantial 

part of the orebody has been lost to erosion.

Two important types of ore are present—a pipe-like porphyry 

copper orebody within the stock that is made up of quartzchalcopyrite-molybdenite veinlets and a supergene-enriched 

chalcocite-malachite blanket that surrounds the stock near the 

surface (Hou and others, 2007a). This enrichment blanket, with 

grades as high as 10 percent copper, is primarily responsible for 

the overall high grade of the Yulong deposit. Wang and others 

(2010) show that oxidized ore constitutes nearly 20 percent of 

the total copper at Yulong. There are also small skarn ore bodies 

adjacent to the porphyry. Mine construction began in 2006 and 

production was expected to start in 2010 (Anonymous, 2006), an 

expectation that appears to have been realized. Figure A2, based 

on August 2010 imagery, shows the initial mining of dark red 

oxidized ore on the margin of the deposit.

The Yulong deposit is emplaced into Triassic clastic and 

carbonate rocks (Ge and others, 1990; Chen and others, 2009). 

The pluton associated with the deposit has an exposed surface 

area of less than 1 km2 and contains between 63 and 67 percent 

silica. Sulfur isotopic composition is enriched, indicating a mantle 

source, and the oxygen and hydrogen isotopic composition 

indicates derivation from magmatic water (Chen and others, 2009). 
Appendix A. Porphyry Copper Assessment for Tract 142pCu8710, Yulong—China 27

Table A2. Porphyry copper deposits in tract 142pCu8710, Yulong—China.

[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 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; %, percent. 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

Yulong 31.40 97.73 Cu-Au 40.7 850 0.84 0.022 0.35 n.d. 7,140,000 Singer and others (2008), Hou and 

others (2006, 2007)

Zhanaga 31.20 97.80 NA 38.5 99.5 0.32 0.03 0.03 n.d. 318,000 Hou and others (2003), Liang and 

others (2006), Yan and others (2007)

Mangzhong 31.17 97.89 NA 37.5 135 0.43 0.03 0.02 n.d. 581,000 Hou and others (2003), Liang and 

others (2006), Yan and others (2007)

Duoxiasongduo 31.04 97.97 NA 37.4 248 0.38 0.04 0.06 n.d. 942,000 Hou and others (2003), Liang and 

others (2006), Yan and others (2007)

Malasongduo 30.99 98.02 NA 36.0 338 0.45 0.014 0.06 n.d. 1,520,000 Singer and others (2008), Hou and 

others, (2006, 2007)

Gegongnong 30.44 98.56 Cu-Au 38.0 101 0.5 n.d. 0.37 2.65 505,000 Singer and others (2008), 

Anonymous (2003)

Figure A2. Google 

EarthTM view of the 

Yulong porphyry 

copper deposit, 

Xizang (Tibet), China. 

Note the initial 

open pit in dark red 

oxidized ore.
28 Porphyry Copper Assessment of the Tibetan Plateau, China

Hydrothermal alteration is typical for porphyry copper deposits, 

with a potassic core, surrounded by a phyllic envelope. Hightemperature assemblages include magnetite, indicating an oxidizing 

environment (Liang and others, 2009a). In addition, advanced 

argillic alteration has overprinted much of the deposit, and alunitebearing assemblages are present (Hou and others, 2007a). The 

pluton at Yulong has a zircon U-Pb age of about 41 Ma as reported 

by Hou and others (2006, 2007a) and between 44 and 43 Ma by 

Wang and others (2009). The Re-Os age of molybdenite is 40.7 Ma 

as reported by Hou and others (2006).

Zhanaga, about 18 km southeast of Yulong, is a much smaller 

and lower grade deposit that contains about 99,500,000 t of ore, 

with a copper grade of 0.32 percent, molybdenum of 0.03 percent, 

and gold of 0.03 g/t (Singer and others, 2008; Yan and others, 

2007). Rocks associated with this deposit display potassic, phyllic, 

argillic, and propylitic hydrothermal alteration zones, but few other 

details are available (Hou and others, 2003; Gu and others, 2003). 

Zircons from the host pluton have been dated by Liang and others 

(2005) at about 38.5 Ma.

Mangzhong is about 25 km southeast of Yulong. It is also 

small, and contains about 135,000,000 t of ore, with a copper 

grade of 0.43 percent, molybdenum of 0.03 percent, and gold 

of 0.02 g/t (Singer and others, 2008; Yan and others, 2007). 

Rocks at Mangzhong also display potassic, phyllic, argillic, 

and propylitic hydrothermal alteration zones. It is characterized 

by associated sphalerite and galena, but few other details are 

available (Hou and others, 2003; Gu and others, 2003). Zircons 

from the host pluton have been dated by Liang and others 

(2005) at about 37.5 Ma.

Duoxiasongduo, about 40 km southeast of Yulong, is 

somewhat larger; it contains about 248,000,000 t of ore, with a 

copper grade of 0.38 percent, molybdenum of 0.04 percent, and gold 

of 0.06 g/t (Singer and others, 2008; Yan and others, 2007). Rocks 

here display potassic, phyllic, argillic, and propylitic hydrothermal 

alteration zones, but few other details are available (Hou and others, 

2003; Gu and others, 2003). Zircons from the host pluton have been 

dated by Liang and others (2005) at about 37.4 Ma.

Malasongduo is about 50 km southeast of Yulong, and 

contains a resource of about 338,000,000 tons of ore, with a 

copper grade of 0.45 percent, molybdenum of 0.014 percent, 

and gold of 0.06 g/t (Singer and others, 2008; Yan and others, 

2007). A general study on the deposit by Liang and others 

(2009b) asserts that it is the second largest deposit in the 

Yulong belt. The associated igneous rocks include both quartz 

monzonite and more felsic K-feldspar porphyry, all dated at 

about 37 Ma by U-Pb methods on zircon, whereas the Re-Os 

age of molybdenite from the deposit is about 36 Ma (Liang 

and others, 2005). There is a zone of Ag-Pb-Zn enrichment 

on the outer margins of the porphyry, but few other details are 

available (Hou and others, 2003; Gu and others, 2003).

Gegongnong is further south, about 135 km southeast of 

Yulong. Singer and others (2008) list a resource of 101,000,000 

t with a copper grade of 0.5 percent, gold of 0.37 g/t, and 

silver of 2.65 g/t. Much of the ore is in breccia pipes within 

the quartz monzonite porphyry that hosts the ore and in skarns 

along the pluton margin (Ding and others, 2005). Gegongnong 

has an associated buried placer gold deposit, Maqu, which 

lies to the north of Gegongnong (Wang and others, 2000). 

Exploration here is apparently ongoing (Anonymous, 2003). 

A Rb-Sr age of about 40 Ma and a K-Ar age of about 38 Ma 

have been reported by Hou and others (2003).

Prospects, Mineral Occurrences, and Related 

Deposit Types

We have some information on seven porphyry copper 

prospects within the tract (table A3). There are no accurate 

published coordinates nor detailed maps of most of these 

prospects, so all locations were derived by interpolation of 

page-size maps and inference from satellite imagery and 

are approximate.

Narigongma, the northernmost prospect in the tract, is 

located about 360 km northwest of the Yulong deposit, in 

Qinghai province. Although no grade and tonnage data are 

available, it is a molybdenum-rich deposit, and is zoned from 

a molybdenum-rich core to a copper-rich outer zone (Hao 

and others, 2010a). A cross-section (fig. 7 in Guo and others 

(2010)) indicates that a substantial part of the mineralized 

body has been removed by erosion. Guo and others (2010) 

also provide a table of analyses that demonstrates that many 

of the intrusive rocks at Narigongma are more silicic than 

most of the other Yulong belt porphyries, although they are 

nevertheless best classified as high-K calc-alkaline.

The biotite granite stock at the deposit has an age of 

43.3 Ma (Yang and others, 2008), whereas the mineralization 

age obtained by Re-Os methods is 40.8 Ma (Wang and others, 

2008). There is a strong copper anomaly at Narigongma on 

the copper geochemical map of China (China Geological 

Survey, 2010b).

Ridanguo is about 120 km northwest of the Yulong 

deposit. Details about the geology are few, but both Hou and 

others (2003) and Gu and others (2003) list Ridanguo as an 

ore-bearing porphyry. Hou and others (2003) determined a K-Ar 

age on feldspar from the Ridanguo pluton of about 42 Ma.

Xiariduo and Hengxingcuo are further south, about 45 

and 15 km, respectively, northwest of the Yulong deposit. No 

specific descriptions of the deposits are available, but they 

are both listed as ore-bearing porphyries by Hou and others 

(2003) and Gu and others (2003). In addition, Jiang and 

others (2008) provide major- and trace-element analyses of 

the monzogranite porphyries associated with these prospects, 

and group them with their ore-bearing porphyries. Hou and 

others (2003) report K-Ar ages for Xiariduo of about 46 Ma 

and for Hengxingcuo of about 41 Ma.

Seli, Jucuo, and Mamupu (which includes the Zengxi 

area mentioned by Gu and others (2003)) are all south of 

the known deposits in the tract. Seli is about 30 km south, 

Jicuo is about 50 km south, and Mamupu about 60 km south 

of Gegongnong, the southernmost porphyry copper deposit 

in the tract. All these igneous centers are more alkaline and 

have lower silica contents than those that host the known 

deposits; they include syenites and are distinctly shoshonitic 
Appendix A. Porphyry Copper Assessment for Tract 142pCu8710, Yulong—China 29

(Jiang and others, 2008). Mamupu was discovered using 

stream-sediment geochemistry (Cheng and others, 2005). 

Seli is apparently undated, but the Mamupu complex has an 

age of about 38 Ma (Hou and others, 2003).

The Lurige prospect is described by Hao and others 

(2010b) as a newly discovered molybdenum (copper) 

porphyry deposit in Yushu County of Qinghai province, to 

the southeast of Narigongma. The location reported here 

is very uncertain, as is its classification, since no grade 

information is available. Lurige is not included in figure 

A1. Nevertheless its presence documents hydrothermal 

mineralization related to high-level intrusions. Hao and 

others (2010b) provide geochemical and isotopic data on the 

intrusions at Lurige and conclude that the rocks are calcalkaline and include both mantle and crustal contributions 

to their composition. No information about grades of the 

mineralized rock is available.

Exploration History

Exploration for porphyry copper deposits in this tract is 

at a relatively early stage, as the porphyry copper model was 

not well-known in China until the 1960s, when scientific and 

industrial activity was renewed after a long period of warfare 

and internal turmoil. Since that time, basic geologic mapping, 

as well as detailed geochemical and geophysical surveys 

have been completed, resulting in the discovery of numerous 

known deposits and prospects. Yulong was the first discovery 

in this area; it was recognized by outcropping malachite in 

1966. There has been extensive exploration for outcropping 

deposits in the central and southern parts of the tract, but 

the northwestern part is still remote and poorly known, as 

evidenced by the recent discovery of the Narigongma prospect. 

In addition, post-mineral sediment and sedimentary rocks 

cover large areas. There is little evidence that non-Chinese 

exploration companies are operating in this part of China.

Stream-sediment geochemical surveys conducted by 

the China Geological Survey have been instrumental in 

discovery of many of the deposits and prospects in this tract. 

A nationwide geochemical map for copper (China Geological 

Survey, 2010b) shows prominent anomalies coincident with 

the Narigongma, Xiariduo, Yulong, Zhanaga, Duoxiasongduo, 

Malasongduo, Gegongnong, and Mamupu areas. Numerous 

other anomalies, not associated with known deposits or 

prospects, are displayed on this map, both in the southeastern 

and northwestern part of the tract.

Sources of Information

Principal sources of information used by the assessment team 

for delineation of the tract are listed in table A4. No geophysical 

data at an appropriate scale were available for the assessment.

Grade and Tonnage Model Selection

There are six known deposits in the tract, and we 

compared their tonnage and grades statistically to the 

worldwide deposit models of Singer and others (2008). Some, 

but not all of the deposits in the tract are gold-rich, but the 

Yulong deposits have distinctly higher Mo grades than the 

deposits included in the Cu-Au model. On the other hand, 

the Yulong deposits have distinctly higher Au grades than the 

deposits included in the Cu-Mo model. The general porphyry 

copper grade and tonnage model was judged to be the most 

appropriate model, and it was used for the estimation of 

undiscovered resources in the Yulong tract. Results of the 

t-test analysis used are shown in table A5.

Table A3. Significant prospects and occurrences in tract 142pCu8710, Yulong—China.

[Ma, million years; Mt, million metric tons; %, percent; g/t, grams per metric ton]

Name Latitude Longitude Age (Ma) Comments 

(grade and tonnage data, if available) Reference

Narigongma 33.53 94.78 41 discovered after 2000; Mo-rich Wang and others (2008), Yang and others (2008)

Ridanguo 32.15 96.77 42 "ore-bearing" porphyry Hou and others (2003), Gu and others (2003), 

Jiang and others (2006), Singer and others (2008)

Xiariduo 31.68 97.45 46 "ore-bearing" porphyry Hou and others (2003), Gu and others (2003), 

Jiang and others (2006), Singer and others (2008)

Hengxingcuo 31.46 97.60 41 "ore-bearing" porphyry Hou and others (2003), Gu and others (2003), 

Jiang and others (2006), Singer and others (2008)

Seli 30.14 98.45 36 "ore-bearing" porphyry Hou and others (2003), Gu and others (2003), 

Jiang and others (2006), Singer and others (2008)

Mamupu 29.96 98.53 38 Cu 0.12–0.32%; Au 6.4–13.1 g/t; 

no tonnage; includes Zengxi and Jicuo

Hou and others (2003), Gu and others (2003), 

Jiang and others (2006), Singer and others (2008)

Lurige 33.42 95.00 Eocene? newly discovered porphyry Mo-Cu prospect Hao and others (2010)
30 Porphyry Copper Assessment of the Tibetan Plateau, China

Estimate of the Number of Undiscovered 

Deposits

Rationale for the Estimate

There are six known deposits and at least six porphyry 

copper prospects in the Yulong tract. However, Hou and others 

(2003) state that the Yulong belt contains “dozens of minor 

prospects and mineralized porphyry intrusions.” The density 

of deposits and prospects along the best-explored part of the 

trend (from Xiariduo to Mamupu) is quite remarkable—ten 

mineralized systems in 230 km. The area in the northwest 

part of the tract is probably underexplored, as it is remote and 

difficult to access due to the climate, the altitude, and a lack 

of infrastructure. Continued exploration in the Yulong belt is 

likely to result in additional discoveries.

Based in part on the presence of at least six prospects in a 

productive area, the team estimated that there was a 90 percent 

chance of 3 or more undiscovered deposits in the tract; we 

believe that several of the presently identified prospects will, 

upon thorough exploration and development, become deposits. 

At the same time, the relatively small size of the tract limits 

the total number of undiscovered deposits that might exist 

there, and the team estimated 18 undiscovered deposits at the 

10 percentile confidence level. The estimated mean number of 

undiscovered deposits is 8.5 (table A6).

Because of the subjective nature of the tract delineation, 

it could be misleading to place great credence in a calculated 

deposit density for this tract, but the team’s estimate is entirely 

consistent with worldwide deposit density estimates (Singer, 

2008; Singer and others, 2005).

A previous assessment (Yan and others, 2007) covered only 

the well-mineralized southeast part of the tract (their Tract XI-4a 

and part of tract XI). They estimated about 3 mean undiscovered 

deposits, compared with the present team’s estimate of 8.5 

deposits (table A6). The larger area designated permissive in this 

study is consistent with the larger estimate. Combined with the 6 

known deposits, this means that the tract probably contains 14 or 

15 porphyry copper deposits.

Table A4. Principal sources of information used for tract 142pCu8710, Yulong—China.

[NA, not applicable]

Theme Name or Title Scale Citation

Geology

Regional geology of Qinghai Province 1:1,000,000 Bureau of Geology and Mineral Resources 

of the Qinghai Province (1991)

Regional geology of Xizang (Tibet) Autonomous Region 1:500,000 Bureau of Geology and Mineral Resources 

of the Xizang Autonomous Region (1993)

Regional geology of Yunnan Province 1:1,000,000 Bureau of Geology and Mineral Resources 

of the Yunnan Province (1990)

Mineral 

occurrences

Porphyry copper deposits of the world: database, map, 

and grade and tonnage models

NA Singer and others (2008)

Metal Mining Agency of Japan mineral deposit database NA Metal Mining Agency of Japan (1998)

World Minerals Geoscience database NA Natural Resources Canada (2010); 

Kirkham and Dunne (2000)

Geological Survey of Japan mineral resources map of East Asia NA Kamitani and others (2007)

The Himalayan Yulong porphyry copper belt—Product of

large-scale strike-slip faulting in eastern Tibet

NA Hou and others (2003)

Himalayan magmatism and porphyry copper-molybdenum 

mineralization in the Yulong ore belt, East Tibet

NA Gu and others (2003)

Streamsediment 

geochemistry

Copper geochemical map 1: 12,000,000 China Geological Survey (2010b)

Bismuth geochemical map 1: 12,000,000 China Geological Survey (2010a)

Table A5. Statistical test results for tract 142pCu8710, Yulong, China. 

[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 from those in the model at the 1-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 test (*) and the model is inappropriate for the assessment. Nknown, number of known deposits in the tract. Note that silver is 

reported for only 1 of the 6 known deposits]

Coded_ID Tract 

name

Nknown Model p valuesModel selected Basis for 

selection Tons Cu Mo Ag Au

142pCu8710 Yulong 6 Cu-Au-Mo 0.87 0.71 0.09 0.74 0.22 Cu-Au-Mo t-test results

Cu-Mo 0.31 0.84 0.83 0.54 *0.0027

Cu-Au 0.89 0.77 *<0.001 0.88 *<0.001
Appendix A. Porphyry Copper Assessment for Tract 142pCu8710, Yulong—China 31

Table A7. Results of Monte Carlo simulations of undiscovered resources for tract 142pCu8710, Yulong—China.

[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 (t) 830,000 2,700,000 20,000,000 76,000,000 110,000,000 32,000,000 0.34 0.03

Mo (t) 0 14,000 380,000 2,300,000 3,600,000 910,000 0.28 0.07

Au (t) 0 30 470 2,000 2,700 820 0.33 0.06

Ag (t) 0 0 4,200 27,000 42,000 11,000 0.27 0.11

Rock (Mt) 210 610 4,200 16,000 22,000 6,600 0.35 0.03

Table A6. Undiscovered deposit estimates, deposit numbers, tract area, and deposit density for tract 142pCu8710, Yulong—China.

[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; density, 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/km2 N ) 90 N50 N10 N05 N01 Nund s Cv

% Nknown Ntotal

3 6 18 18 18 8.5 5.7 67 6 14 112,470 0.00013

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 1Tr

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 

Figure A3. Cumulative 

frequency plot showing 

the results of Monte Carlo 

computer simulation of 

undiscovered resources for 

tract 142pCu8710, Yulong—

China. k, thousand; M, million; 

B, billion; Tr, trillion.
32 Porphyry Copper Assessment of the Tibetan Plateau, China

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 A7. Results of the 

Monte Carlo simulation are presented as a cumulative frequency 

plot (fig. A3), which shows the estimated resource amounts 

associated with cumulative probabilities of occurrence, as well as 

the mean, for each commodity and for total mineralized rock.

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Appendix A. Porphyry Copper Assessment for Tract 142pCu8710, Yulong—China 33

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Appendix B. Porphyry Copper Assessment for Tract 142pCu8711, Dali—China and Vietnam 35

Table B1. Summary of selected resource assessment results for tract 142pCu8711, Dali—China.

[km, kilometers; km2, square kilometers; t, metric tons]

Date of

assessment

Assessment depth 

(km)

Tract area

(km2

)

Known

copper resource

 (t)

Mean estimate of 

undiscovered copper 

resources (t)

Median estimate of 

undiscovered copper 

resources (t)

2010 1 96,670 490,000 26,000,000 15,000,000

1

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

2

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

3

China Geological Survey, Beijing, China.

4

Chinese Academy of Geological Sciences, Beijing, China.

Appendix B. Porphyry Copper Assessment for Tract 142pCu8711, Dali—China 

and Vietnam

By Steve Ludington1, Jane M. Hammarstrom2, Gilpin R. Robinson, Jr.2, and Robert J. Miller1, based on 

contributions of Yan Guangsheng3

, Peng Qiuming3, Lian Changyun3, Mao Jingwen4, Li Jinyi3, Xiao Keyan3, Qiu 

Ruizhao3

, Shao Jianbao3, Shai Gangyi3, and Du Yuliang3

Deposit Type Assessed: Porphyry Copper

Deposit type: Porphyry copper

Descriptive model: Porphyry copper (Cox, 1986; John and others, 2010)

Grade and tonnage model: Gold-rich porphyry copper (Singer and others, 2008)

Table B1 summarizes selected assessment results.

Location

The Dali tract extends for nearly 1,000 kilometers (km), from northern to southern Yunnan Province in China and into Vietnam, 

along the Sanjiang-Red River transform fault zone, and includes an eastward extension about 300 km into southwestern Sichuan 

Province on the South China craton (fig. B1). The tract is exceedingly mountainous, with elevations ranging from nearly 6,000 meters 

(m) to less than 1,000 m.

Geologic Feature Assessed

An assemblage of Eocene and Oligocene igneous rocks that formed in a transtensional post-subduction environment in 

southwest China during the collision between India and Asia.
36 Porphyry Copper Assessment of the Tibetan Plateau, China

x

!

!

!

LAOS

CHINA

MYANMAR

VIETNAM

XIZANG

GUIZHOU

SICHUAN

YUNNAN

Kunming

Tongchang Habo

Machangqing

Xifanping

Liufang

Changpingchong

Sin Quyen

WangdongshanHongnitang

Xiaolongtan

99°E 102°E

26°N

22°N

CHINA

MYANMAR

INDIA

THAILAND

90°E 100°E 110°E

30°N

20°N

10°N

0 40 80 120 160 KILOMETERS

0 40 80 MILES

EXPLANATION

Other porphyry copper tracts

Assessed porphyry copper 

tract 142pCu8711

Porphyry copper deposit

Porphyry copper prospect

Porphyry-related prospect

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

Projection: Asia North Albers Equal Area Conic;

central meridian 102° E; latitude of origin 30° N

x

Figure B1. Map showing tract location, known porphyry copper deposits, and significant porphyry copper prospects for tract 

142pCu8711, Dali—China and Vietnam.
Appendix B. Porphyry Copper Assessment for Tract 142pCu8711, Dali—China and Vietnam 37

Delineation of the Permissive Tract

Geologic Criteria

Igneous rocks that define the Dali tract formed during 

continental-scale strike-slip faulting during the late-collision stage. 

These rocks range in age from about 40 million years (Ma) to 

about 26 Ma (see Deng and others, 1998), and are therefore slightly 

younger than the rocks in the Yulong porphyry belt to the north. 

They were emplaced along the Sanjiang-Red River fault zone, the 

southern extension of the Jinsa suture which forms the boundary 

between Indochina and the South China craton and constitutes the 

suture between them (Wang and others, 2001b; Guo and others, 

2005). The rocks also extend several hundred kilometers eastward 

onto the South China craton. In addition, REE-bearing carbonatite 

complexes with ages between about 40 and 10 Ma crop out along 

the eastern margin of the tract (Hou and others, 2009).

The Sanjiang-Red River structure is a strike-slip fault that has 

accommodated much of the strain associated with the Indo-Asian 

collision since the Paleocene; there are numerous strands of this fault. 

All but one (Xifanping) of the two porphyry copper deposits and 

eight prospects in the tract are within about 50 km of this structure.

Most of the igneous rocks form porphyritic intrusions, though 

a few volcanic remnants crop out. The majority of the plutons 

are syenite, but include some granite and monzonite, as well as 

numerous small bodies of mafic alkaline rock (Deng and others, 

1998; Wu and others, 2005; Guo and others, 2005). These rocks, 

emplaced between about 40 and 26 Ma, appear to have formed by 

melting metasomatized mantle at depths near 100 km (Guo and 

others, 2005). This melting was triggered by the large trans-crustal 

strike-slip faults that traverse and help define the tract (Hou and 

others, 2005, 2010).

As a basis for tract delineation, we used unpublished digital 

versions of the geological maps of Yunnan and Sichuan Province 

published by the Chinese Ministry of Geology and Mineral 

Resources in the early 1990s (Bureau of Geology and Mineral 

Deposits of the Yunnan Province, 1990; Bureau of Geology and 

Mineral Deposits of the Sichuan Province, 1991). The resulting 

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 

been studied extensively petrologically. In addition, many of 

the plutons associated with known deposits and prospects in the 

tract are less than a square kilometer in outcrop area, and are not 

included in the digital map.

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, i.e. calc-alkaline and alkaline 

volcanic and plutonic rocks of Tertiary age. The plutons 

that help define the tract are primarily syenite, but include 

lesser amounts of granite, monzonite, and diorite. Volcanic 

rocks in the tract are far less abundant than plutons; they are 

predominantly trachyte, but include minor dacite and rhyolite. 

In addition to these polygons from the digital geologic map, 

we digitized additional polygons to represent those bodies 

shown in figure 1 of Guo and others (2005) but not present on 

the digital map. These are all mafic alkaline rocks. We also 

compared the tract to the generalized map in figure 1 of Yang 

(2010) and to map 17 of Wagner (2003) to ensure the inclusion 

of all the alkaline plutons on those maps.

A 20-km buffer was applied to plutonic rock polygons 

and a 2-km buffer to volcanic rock polygons. Buffering 

expanded the area of the tract to include the prospects in the 

tract and account for uncertainties in the cartographic position 

of mapped boundaries, as well as possible unexposed or 

unmapped permissive rocks. A larger 20-km buffer was chosen 

for this tract because so many of the igneous bodies are small 

and often not portrayed on regional maps.

After initial delineation, the limited available geophysical 

and geochemical information was examined to be sure that any 

other evidence of unmapped permissive rocks or hydrothermal 

systems at shallow depths was included. A corridor along 

the Ailoshan suture was also included, which controlled the 

emplacement of the igneous rocks. A smoothing routine was 

applied to the resulting polygons, and the tract was trimmed 

to terrane-bounding faults. Areas where Tertiary basins were 

judged to be deeper than 1 km were excluded by buffering 

inward 1 km from the margins of outcrops of post-mineral 

sedimentary rock and sediment. The tract is shown in figure B1.

Chen and others (2007) conducted a mineral resource 

assessment in the region based on weights of evidence (BonhamCarter and others, 1989). Because their method relied heavily 

on geochemical information, it was problematic to separate 

copper anomalies due to basalt-related copper deposits in the area 

from those that might be due to porphyry-style mineralization. 

Nevertheless, they identified a number of prospective areas for 

polymetallic deposits that correspond closely to the southern arm 

of the geology-based tract we delineated. The tract corresponds 

generally to the Jinshajiang-Ailoshan Cu-Au metallogenic belt, as 

defined by Wang and others (2009).

Known Deposits

The tract contains two known porphyry copper deposits 

(table B2). These deposits are named Xifanping and Machangqing.

Xifanping (also known as Mofancun), the northernmost 

deposit in the tract, is in western Sichuan Province. It is briefly 

described by Hou and others (2006) as being related to a 

multistage quartz monzonite pluton, with an associated breccia 

pipe (Li and others, 2006). Xiao and others (1999) studied the 

intrusions in more detail and identified at least 130 individual 

bodies, many with outcrop areas less than 0.1 km2. Compositions 

of the intrusions range from quartz syenite to quartz monzonite; 

the rocks are commonly altered to assemblages that include 

sericite and chlorite. Ore is within and on the periphery of the 

stocks; molybdenum is concentrated in early-formed veins in 

the K-silicate alteration zone and gold is concentrated in later 

peripheral veins. The deposit is small, but the gold grade is 0.31 

grams per metric ton (g/t) (Singer and others, 2008). Xifanping 

also includes a supergene chalcocite-bearing enrichment blanket 

that is as much as 100 meters (m) thick and contains grades up 
38 Porphyry Copper Assessment of the Tibetan Plateau, China

to 0.8 percent copper (Wang and others, 2001a). Re-Os dating 

indicates a mineralization age of about 32 Ma (Hou and others, 

2006; Zeng and others, 2006).

Yanyuan is mentioned in a single paper (Chen and others, 

1996), and Kirkham and Dunne (2000) suggest a location just 

10 km south of Xifanping. However their location for Xifanping 

is 35 km east of its actual location. Because there is no post-1996 

mention of this deposit, and because Xifanping is in Yanyuan 

county, we think it likely that Yanyuan is another name for 

Xifanping and is thus not shown on figure B1.

Machangqing is located about 200 km south of Xifanping, 

in northern Yunnan, and is probably the most thoroughly studied 

deposit in the tract. The deposit is described by Peng and others 

(1998) as being related to an I-type granite porphyry stock, 

intruded by monzonite porphyry and lamprophyre dikes. Three 

types of ore are present in the district, porphyry Cu-Mo within 

the stock, skarn Cu-Mo-Au on the margins of the stock, and 

epithermal gold-polymetallic more distal in the Ordovician 

calcareous sedimentary wall rocks (Guo and others, 2009, 2010; 

Wang and others, 2010). A cross-section (fig. 5 of Peng and others, 

1998) implies that a large part of the deposit may have been 

removed by erosion, perhaps helping to explain its small size. The 

reported distribution of hydrothermal alteration assemblages is 

typical for porphyry copper deposits, and hydrothermal magnetite 

is abundant. The deposit is rich in both gold (0.35 g/t) and 

molybdenum (0.078 percent) (Singer and others, 2008).

In two separate studies (Hou and others, 2006; Wang and 

others, 2005), Machangqing was dated by the Re-Os method to 

be about 35–34 Ma, in good accordance with earlier Rb-Sr dates 

of 36–34 Ma and zircon Sensitive High Resolution Ion Micro 

Probe (SHRIMP) ages of 36–35 Ma for associated igneous 

rocks (Zeng and others, 2006). More recent Re-Os dates have 

been determined on molybdenite at 35.8 Ma by Zeng and others 

(2006) and 35.3 Ma by Xing and others (2009).

In a study focused on the distal gold deposits 

(Baoxinchang, Jinchangqing) to the northeast of Machangqing, 

Huang and others (1996) found a close spatial association of the 

gold deposits with mantle-derived lamprophyre dikes that are 

common in the area. Bi and others (2006) studied the mineral 

chemistry of the intrusive rocks at Machangqing and concluded 

that the stocks crystallized near 730° C at a pressure of 2.2 to 

2.8 kilobars (kbar) under relatively oxidizing conditions. 

Prospects, Mineral Occurrences, and Related 

Deposit Types

Information was collected on eight porphyry copper prospects 

within the tract. Some of the prospects are described without 

coordinates or detailed maps and these are very approximately 

located. In addition to these eight, there is another poorlydocumented mineral deposit in Vietnam that could possibly be a 

porphyry copper system.The prospects are listed in table B3.

The Beiya iron-gold district, about 160 km southwest 

of the Xifanping deposit, near the town of Dali, contains two 

poorly explored porphyry copper prospects associated with the 

Wangdongshan and Hongnitang stocks (Xu and others, 2007). These 

prospects are related to quartz-albite and quartz-K-feldspar porphyry 

stocks, and have typical grades of 0.1 to 5 percent copper and 0.03 

to 3.3 g/t gold. The K-feldspar porphyries have Ar-Ar ages of about 

33–25 Ma. Exploration in the district has so far focused on the 

gold deposits, which are being exploited, and the porphyry copper 

deposits remain relatively unexplored (Yang, 2010).

We found information about a porphyry copper prospect called 

Xiaolongtan, which is in Binchuan County, a few tens of km north 

of Machangqing, but few details are available and the deposit is not 

shown on figure B1 because it cannot be accurately located (Zhang 

and others, 2009; Wang and others, 2008).

Liufang is mentioned only by Yan and others (2007). They 

give few details, but describe it as small (14,000 t contained 

copper), and with a grade (1.57 percent Cu) that is more typical of 

skarn deposits.

Habo is a copper-gold-molybdenum porphyry prospect in 

the southern part of the tract that is being explored by Asia Now 

Resources Corporation (fig. B2). Progress there is documented on 

the company’s website (Asia Now Resources, 2010). The deposit 

is at least 2,300 m by 1,600 m, and is typified by extensive potassic 

alteration and a quartz-magnetite-sulfide stockwork. Sampling in 

adits driven into the mineralized body have revealed multi-element 

mineralization; for example Tunnel PD11, sampled over a 100 m 

length, showed: Cu, 0.07 to 1.33 percent; Mo, 0.01 to 0.32 percent; 

and gold, 0.04 to 0.15 g/t. As of February 2011, eleven drill holes 

have been completed, and exploration is ongoing.

The deposit at Habo is also described by White and others 

(2007) and Harris and others (2007). The source rocks are 

described as highly oxidized granitoid rocks that have been 

strongly potassically altered, including the development of 

Table B2. Porphyry copper deposits in tract 142pCu8711, Dali—China and Vietnam.

 [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 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

Xifanping 27.491 101.017 Cu-Au 32 64.3 0.28 n.d. 0.31 n.d. 180,000 Singer and others (2008), Hou and 

others (2006)

Machangqing 25.521 100.438 unk 35 62 0.5 0.078 0.35 n.d. 310,000 Singer and others (2008), Peng and 

others (1998), Hou and others (2006), 

Wang and others (2005)
Appendix B. Porphyry Copper Assessment for Tract 142pCu8711, Dali—China and Vietnam 39

abundant secondary K-feldspar and biotite. These rocks were 

previously described as syenites because their hydrothermal 

alteration was not recognized. Biotite-feldspar porphyry has SiO2

contents between 52 and 62 percent; quartz-feldspar porphyry is 67 

to 73 percent SiO2 (Zhu and others, 2009). Zircons from these rocks 

yield U-Pb ages of about 36 Ma; an unpublished Rb-Sr model age 

is 37.3 Ma. Molybdenite from the deposit is dated at about 35.5 Ma 

by the Re-Os method.

Tongchang was identified as a porphyry copper prospect by 

Wang and others (2005) and Hou and others (2006) (who referred 

to it as Chang’an). Wang and others (2005) determined a Re-Os age 

on molybdenite of 34.4 Ma, similar to earlier Rb-Sr ages that range 

from 36 to 34 Ma. No papers include a description of the deposit, 

but Hou and others (2006) suggest grades of 1.5 percent copper, 

0.12 percent molybdenum, and 6 g/t gold and report that it consists 

of veinlets disseminated in syenites and granite host rocks.

Changpingchong is mentioned only by Yan and others (2007). 

They give few details, but describe it as small (30,000 t contained 

copper), with a grade (1.48 percent Cu) that is more typical of skarn 

deposits. Changpingchong and Tongchang (Chang’an) may be 

different names for the same deposit.

About 75 km to the southeast, just across the border in 

Vietnam, the Sin Quyen deposit has been classified as a Fe 

oxide-Cu-Au-REE deposit (McLean, 2002), however very 

little has been published about the deposit and its classification 

is uncertain; it could be a copper-gold skarn. Although it is 

in production it is treated here as a prospect because of the 

uncertainty in classification and lack of tonnage and grade 

Figure B2. View of Habo prospect, showing exploration tunnels 

in middleground.

information. It is one of the larger copper deposits in southeast 

Asia, containing at least 500,000 t of copper (McLean, 2002).

Some information was found regarding three other deposits 

in southernmost Yunnan that are referred to as porphyry copper 

or copper-polymetallic deposits. They are Xionglumo (near 

Machangqing; He and others, 2004) Minle (west of Habo; Li, 

2000), and Puerdi (Yang, 2009). It was not possible to determine a 

location for these deposits.

Table B3. Significant prospects and occurrences in tract 142pCu8711, Dali—China and Vietnam.

[Ma, million years; Mt, million metric tons; n.d., no data; %, percent; FeOX, iron oxide-rich; Cu, copper; Mo, molybdenum; Au, gold; kt, thousand metric tons; 

t, metric tons; g/t, grams per metric ton]

Name Latitude Longitude Age (Ma) Comments (grade and tonnage data, if available) Reference

Wangdongshan/

Hongnitang

26.16 100.19 29 Appears to be Au-rich Xu and others (2007)

Xiaolongtan 25.6 100.5 Oligocene Location very approximate Zhang and others (2009), Wang and 

others (2008)

Liufang 23.38 102.39 Cenozoic Unsubstantiated resource estimate of 14,000 t Cu; 

may be a skarn deposit

Yan and others (2007)

Habo 22.88 102.54 37 Under active exploration; quartz-magnetite-sulfide 

stockwork

Asia Now Resources (2010), White and 

others (2007), Harris and others (2007)

Tongchang 22.80 103.04 34 Also called Chang'an; estimated grades of 1.5% Cu, 

0.12% Mo, and 6 g/t Au; may be a skarn deposit

Wang and others (2005), Hou and 

others (2006)

Changpingchong 22.77 103.01 Cenozoic Unsubstantiated resource estimate of 30,000 t Cu; 

may be a skarn deposit

Yan and others (2007)

Minle n.d. n.d. presumed 

Cenozoic

Exact location unknown; west of Habo Li (2000)

Xionglumo n.d. n.d. presumed 

Cenozoic

Exact location unknown; near Machanqing He and others (2004)

Sin Quyen 22.60 103.83 Tertiary May be FeOX-Cu-Au or Cu-Au skarn. Contains at 

least 500 Kt Cu.

McLean (2002)
40 Porphyry Copper Assessment of the Tibetan Plateau, China

In addition to these porphyry copper prospects, a number 

of recently discovered hydrothermal gold deposits related to 

alkaline intrusive rocks within the tract have been described as 

porphyry gold deposits (Bi and others, 2004). These deposits 

may be distal expressions of porphyry copper-gold systems. 

Many of the deposits and prospects in the tract, including 

Xifanping and Machangqing, are most closely related to 

late quartz-saturated rocks (granite and quartz monzonite) 

but alkaline rocks (syenite and alkaline lamprophyre) are 

important parts of the igneous assemblage. The alkaline rock 

association and widespread occurrence of porphyry gold 

deposits and gold- and iron-rich skarns in the tract (Xu and 

others, 2007) are reminiscent of the assemblage of igneous 

rocks and ore deposits in the southern Rocky Mountains, 

USA, described by Kelley and Ludington (2002) and termed 

Great Plains Margin deposits by McLemore (1996). In contrast 

to the Dali tract, the tectonic setting in the southern Rocky 

Mountains has been considered to be back-arc extensional and 

there are no prominent shear zones.

Exploration History

Exploration for porphyry copper deposits in this tract is 

at a relatively early stage, as the porphyry copper model was 

not well-known in China until the 1960s, when scientific and 

industrial activity was renewed after a long period of warfare 

and internal turmoil. Since that time, basic geologic mapping, as 

well as detailed geochemical and geophysical surveys have been 

completed, resulting in the discovery of several of the presently 

known prospects, including Xifanping and Machangqing. 

Nevertheless, the discovery of the Habo system in 2005, due 

to heavy rainfall that revealed previously hidden outcrops, 

demonstrates that discoveries based on modern understanding of 

porphyry systems are still likely (White and others, 2007). Most of 

the tract is variably populated, but terrain is steep, and vegetative 

cover hampers exploration. The current level of exploration 

activity in this tract is not well known, however, the presence of 

Asia Now Resources at the Habo project shows that non-Chinese 

exploration companies are exploring for porphyry copper deposits 

in this part of China.

Stream-sediment geochemical surveys conducted by the 

China Geological Survey have been instrumental in the discovery 

of many of the deposits and prospects in western China. A 

nationwide geochemical map for copper (China Geological 

Survey, 2010b) shows prominent anomalies near both Xifanping 

and Machangqing, but the widespread occurrence of copper-rich 

basalts of the Emeishan basalt province confounds the use of 

stream-sediment data for exploration for porphyry deposits in this 

part of China.

Sources of Information

Principal sources of information used by the assessment team 

for delineation of the tract are listed in table B4. No geophysical 

data at an appropriate scale were available for the assessment.

Grade and Tonnage Model Selection

Both known porphyry copper deposits in the tract have 

gold grades in excess of 0.3 g/t and qualify as porphyry 

Cu-Au deposits. In addition, there are numerous gold deposits 

in the tract that are related to the same suite of alkaline 

igneous rocks as the porphyry copper deposits. High gold 

grades have also been reported from several of the prospects 

in the tract. For all the reasons above, the gold-rich porphyry 

copper grade and tonnage model was judged to be the most 

appropriate model, and was used for the estimation of 

undiscovered resources in the Dali tract.

Estimate of the Number of Undiscovered 

Deposits

Rationale for the Estimate

Two known deposits and at least eight porphyry copper 

prospects have been identified in the Dali tract. Wang and others 

(2005) state that “a lot of Cu-Au deposits and occurrences related to 

syenite porphyry have been discovered recently” in the tract. Much 

of the area is extremely rugged and access is difficult. Continued 

exploration in this area is likely to result in the discovery of 

additional porphyry copper deposits.

Based in part on the presence of at least eight prospects in 

a productive area, the team estimated that there was a 90 percent 

chance of two or more undiscovered deposits in the tract; we 

believe that several of the presently identified prospects will, 

upon thorough exploration and development, become deposits. 

The relatively small size of the tract limits the total number of 

undiscovered deposits that might exist there, and the team estimated 

only 18 undiscovered deposits at the 10th percentile confidence 

level. The estimated mean number of undiscovered deposits is 8.3 

(table B5).

Because tract delineation is a subjective process, it could 

be misleading to place great credence in a calculated deposit 

density for this tract, but the assessment team’s estimate is entirely 

consistent with worldwide deposit density estimates (Singer, 2008; 

Singer and others, 2005).

A previous assessment (Yan and others, 2007) covered much of 

the tract (their Tract XI-4c and part of tract XI). They estimated about 

4 mean undiscovered deposits, compared with the present team’s 

estimate of 8.3 (table B5). The results of exploration conducted in the 

years since the earlier estimate was made can explain much of the 

difference. Combined with the 2 known deposits, the tract probably 

contains about 10 porphyry copper deposits.

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 
Appendix B. Porphyry Copper Assessment for Tract 142pCu8711, Dali—China and Vietnam 41

Table B4. Principal sources of information used for tract 142pCu8711, Dali—China and Vietnam.

[NA, not applicable]

Theme Name or Title Scale Citation

Geology

Regional geology of Sichuan Province 1:1,000,000 Bureau of Geology and Mineral Resources 

of the Sichuan Province (1991)

Regional geology of Yunnan Province 1:1,000,000 Bureau of Geology and Mineral Resources 

of the Yunnan Province (1990)

Potassic magmatism in Western Sichuan and Yunnan Provinces, 

SE Tibet, China—Constraints on petrogenesis

NA Guo and others (2005)

Porphyry Cu-Au and associated polymetallic Fe-Cu-Au deposits 

in the Beiya Area, western Yunnan Province, south China

NA Xu and others (2007)

Mineral

occurrences

Porphyry copper deposits of the world: database, map, and grade 

and tonnage models

NA Singer and others (2008)

Metal Mining Agency of Japan mineral deposit database NA Metal Mining Agency of Japan (1998)

World minerals geoscience database NA Natural Resources Canada (2010); Kirkham 

and Dunne (2000)

Geological Survey of Japan mineral resources map of East Asia NA Kamitani and others (2007)

Stream-sediment 

geochemistry

Copper geochemical map 1: 12,000,000 China Geological Survey (2010b)

Bismuth geochemical map 1: 12,000,000 China Geological Survey (2010a)

Table B5. Undiscovered deposit estimates, deposit numbers, tract area, and deposit density for tract 142pCu8711, Dali—China.

[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; density, 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/km2

) N90 N50 N10 N05 N01 Nund s Cv

% Nknown Ntotal

2 6 18 18 18 8.3 5.9 72 2 10 96,670 0.00011

Table B6. Results of Monte Carlo simulations of undiscovered resources for tract 142pCu8711, Dali—China 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 (t) 200,000 1,300,000 15,000,000 64,000,000 87,000,000 26,000,000 0.36 0.04

Mo (t) 0 0 54,000 470,000 670,000 150,000 0.28 0.16

Au (t) 24 130 1,200 4,600 5,900 1,900 0.38 0.04

Ag (t) 0 0 3,100 24,000 42,000 8,600 0.25 0.11

Rock (Mt) 56 320 3,300 13,000 16,000 5,200 0.37 0.04
42 Porphyry Copper Assessment of the Tibetan Plateau, China

(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), which shows the estimated 

resource amounts associated with cumulative probabilities of 

occurrence, as well as the mean, for each commodity and for 

total mineralized rock. 

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Yang, Zexiang, 2009, Geological features of the Puerdi 

porphyry copper deposit in Muli, Sichuan: Geology, 

v. 29, p. 132–135. [In Chinese, with English abstract.]

Zeng, Pusheng, Hou, Zengquian, Gao, Yongfeng, and Du, 

Andao, 2006, The Himalayan Cu-Mo-Au mineralization in 

the eastern Indo-Asian collision zone—Constraints from 

Re-Os dating of molybdenite: Geological Review, v. 52, p. 

72–84. [In Chinese, with English abstract.]

Zhang, Jinxue, Wang, Wenchao, Lei, Yangai, and Mei, 

Pulian, 2009, The prospecting idea of Xiaolongtan 

porphyry Cu deposit in Binchuan: Yunnan Geology, v. 

28, p. 409–414. [In Chinese, with English abstract.]

Zhu, Xiangping, Mo, Xuanxue, White, N.C., Zhang, Bo, Sun, 

Mingxiang, Wang, Shuxian, Zhao, Sili, and Yang, Yong, 2009, 

Geology and metallogenetic setting of the Habo porphyry Cu 

(Mo-Au) deposit, Yunnan: Acta Geologica Sinica, v. 83, p. 

1915–1928. [In Chinese, with English abstract.]
46 Porphyry Copper Assessment of the Tibetan Plateau, China

Table C1. Summary of selected resource assessment results for tract 142pCu8712, Gangdese—China.

[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)

2010 1 239,860 15,200,000 87,000,000 61,000,000

1

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

2

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

3

China Geological Survey, Beijing, China.

4

Chinese Academy of Geological Sciences, Beijing, China.

Appendix C. Porphyry Copper Assessment for Tract 142pCu8712, Gangdese—

China

By Steve Ludington1, Jane M. Hammarstrom2, Gilpin R. Robinson, Jr.2,, and Robert J. Miller1, based on 

contributions of Yan Guangsheng3

, Mao Jingwen4, Li Jinyi3, Xiao Keyan3, Qiu Ruizhao3, Shao Jianbao3, Shai 

Gangyi3

, and Du Yuliang3

Deposit Type Assessed: Porphyry Copper

Deposit type: Porphyry copper

Descriptive model: Porphyry copper (Cox, 1986; John and others, 2010)

Grade and tonnage model: General porphyry copper (Singer and others, 2008)

Table C1 summarizes selected assessment results.

Location

The Gangdese tract extends for about 1,600 kilometers (km), from far western to far eastern Xizang Autonomous Region (Tibet) 

in China, just north of the Yarlung-Tsampo suture zone, which marks the boundary between the Indian and Asian continental blocks 

(fig. C1). Most of the tract is quite narrow, about 100 km, and much of it is in exceedingly high mountains, with elevations ranging from 

about 4,000 to more than 7,000 meters (m).

Geologic Feature Assessed

A belt of Late Oligocene to Miocene igneous rocks that formed in an extensional, post-subduction environment in 

southwest China after the collision between India and Asia.
! x x x NEPAL INDIA

CHINA

Lhasa Jiama

Xiangbeishan

QINGHAI

XIZANG

Gangjiang

Jiagangxueshan

Sharang

Tang

Jiru

Lakang’e

Nanmu

Qulong

Tinggong

Xietongmen/ Newtongmen

Zhunuo Banongla

Zemoduola

Tangbai

Chuibaizi

Demingding

Dubuqu

Bangpu

Mingze

Chengba

Yuejingou Chongmuda

Luobuzhen

Xiamari

Liebu

Zongxun

Kelu

(Nuri)

84°E 92°E

33°N

30°N

INDIA

60°E 90

40°N30°N20°N

0 50 100 150 200 KILOMETERS0 50 100 MILES

Political boundary source U.S. Department of State (2009)Projection: Asia North Albers Equal Area Conic;central meridian 88° E; latitude of origin 30° N

EXPLANATION

Other porphyry copper tractsAssessed porphyry copper tract 142pCu8712Porphyry copper depositPorphyry copper prospect; prospectsassociated with other tracts shown in gray

x Porphyry-related prospect

Figure C1. Map showing tract location, known porphyry copper deposits, and significant porphyry copper prospects for tract 142pCu8712, Gangd
48 Porphyry Copper Assessment of the Tibetan Plateau, China

Delineation of the Permissive Tract

Geologic Criteria

Igneous rocks that define the Gangdese tract formed during 

continental-scale extension and uplift during the post-collision 

stage of the India-Asia collision. They range in age from about 

28 million years (Ma) to about 12 Ma (Qu and others, 2009), 

although a few may be older (Eocene). Their emplacement 

was guided by north-south normal faults related to rifting that 

accompanied rapid uplift of the Tibetan Plateau caused by 

continued underthrusting of the Indian continent (Qu and others, 

2009; Hou and Cook, 2009; Hou and others, 2011).

The igneous rocks are mostly porphyritic intrusive rocks, 

though a few volcanic remnants crop out. The majority of the 

plutons are granodiorite, quartz monzonite, and monzogranite 

(Qu and others, 2007). There is an emerging consensus that 

they are mantle-derived melts that have assimilated important 

amounts of lower crustal material, as well as some upper 

crustal material during ascent (Hou and others, 2009; Hou and 

others, 2011), and that the trigger for emplacement was the 

uplift and extension of the Tibetan Plateau.

As a basis for tract delineation, we used an unpublished 

digital version of the geological map of Tibet that was published by 

the Chinese Ministry of Geology and Mineral Resources (Bureau 

of Geology and Mineral Resources of the Xizang Autonomous 

Region, 1993). The resulting 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. However, many of the rocks have not 

been dated precisely nor been studied extensively petrologically. In 

addition, many of the plutons associated with known deposits and 

prospects are less than a square kilometer in outcrop area, and thus 

are not included in the digital map.

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, i.e. calc-alkaline and 

alkaline volcanic and plutonic rocks of Tertiary age. We then 

examined the more recent 1:2,500,000 scale geologic map 

of China (China Geological Survey, 2004) and designated 

units as permissive on that map as well. In addition to 

these polygons from the digital geologic map, we digitized 

additional polygons to represent those bodies shown in figure 

3 of Hou and others (2009) but not present on the digital map.

We applied a 15-km buffer to plutonic rock polygons and 

a 2-km buffer to volcanic rock polygons. Buffering expanded 

the area of the tract to include deposits and prospects in 

the tract and accounts for uncertainties in the cartographic 

position of mapped boundaries, as well as possible unexposed 

or unmapped permissive rocks.

After initial delineation, we examined the limited 

available geophysical and geochemical information to be 

sure we included any other evidence of unmapped permissive 

rocks or hydrothermal systems at shallow depths. Because of 

the strong structural control of deposits in this tract, we also 

filled any gaps in the resulting tract, to emphasize the eastwest nature of the belt of mineralized intrusions. A smoothing 

routine was applied to the resulting polygons, and the tract 

was trimmed to terrane-bounding faults.

The resource assessment reported by She and others 

(2009) includes a map of the prospective areas they identified 

using a method that combined weighted geological and 

geochemical evidence layers. We extended the Gangdese tract 

in a few areas to include these prospective areas. We also 

excluded areas where Tertiary basins were judged to be deeper 

than 1 km by buffering inward 1 km from the margins of 

outcrops of post-mineral sedimentary rock and sediment. The 

tract is shown in figure C1.

Known Deposits

The Gangdese tract contains three known porphyry copper 

deposits (table C2), although only one, Qulong, meets all the criteria 

of Singer and others (2008) to be termed a deposit. Although both 

Xietongmen/Newtongmen and Jiama are large deposits and Jiama 

is in production, active exploration in the vicinity of each continues 

and their resources continue to grow; they cannot be considered 

to be completely delineated. Nevertheless, for the purposes of 

this assessment and because of their size, we considered both 

Xietongmen/Newtongmen and Jiama to be known deposits. Qulong 

clearly contains unexplored resources at depth, but exploration has 

ceased, and the deposit is being readied for production.

Xietongmen/Newtongmen Area

Xietongmen is the first porphyry copper deposit in China 

to be drilled out and readied for production according to 

western standards. About 250 km west of Lhasa, the capital, 

the deposit (fig. C2) was discovered by the Tibet Geological 

Bureau in 2000, while following up on stream-sediment 

geochemical anomalies. Short adits were driven in 2001 and 

Figure C2. Photograph of the Xietongmen porphyry copper 

deposit, Xizang (Tibet), China. Photo looking south across YarlungTsangpo River, shows drill roads at an early stage of exploration.
Appendix C. Porphyry Copper Assessment for Tract 142pCu8712, Gangdese—China 49

2002 and the first drilling was conducted in 2003. Between 

2004 and 2011, the deposit was explored and developed by 

Continental Minerals Corporation of Vancouver, British 

Columbia. In late 2010, an agreement was announced wherein 

the deposit was to be purchased by Jinchuan Group Ltd. 

(Continental Minerals Corporation, 2010a); the arrangement 

was completed in the spring of 2011. Except where noted 

otherwise, the characterization of the deposit is derived from 

technical (43-101) reports concerning the property, one in 

2007 (Rebagliati and others, 2007) and another describing 

activities in 2007 and 2008 (Rebagliati and others, 2009).

Current data indicate that the Xietongmen deposit 

contains 219,800,000 metric tons (t) of ore at 0.43 percent 

copper, 0.61 grams per metric ton (g/t) gold, and 3.87 g/t 

silver. (Continental Minerals Corporation, 2010b), including 

both measured and indicated resources, calculated at a cutoff 

grade of 0.15 percent copper. About 10 percent of the ore 

consists of supergene-enriched oxide facies material.

The deposit is hosted in Jurassic volcanic and intrusive rocks 

and consists of a coherent pod-shaped body of disseminated and 

veinlet mineralization that measures about 600 m north-south, 

1,300 m east-west, and 320 m vertically. This body is elongate 

along a N60°W axis, parallel to several faults that appear have 

localized the mineralization (Xu and others, 2009). Hydrothermal 

alteration assemblages include potassic, phyllic (quartz-sericitepyrite), and several varieties of propylitic alteration that include 

actinolite, chlorite, and albite (Rebagliati and others, 2009).

Centered about 2.5 km to the northwest of Xietongmen, 

Newtongmen is another important mineralized zone in the area. 

It has been extensively drilled since 2006, and is much larger, 

though lower grade, than Xietongmen. Alteration zones associated 

with the two deposits overlap, and it is likely that both are part 

of the same mineralized system, although Newtongmen has not 

been dated independently. The current provisional indicated plus 

inferred resource for Newtongmen is 865,300,000 t at 0.27 percent 

copper, 0.13 g/t gold, and 0.51 g/t silver, calculated at a cutoff 

grade of 0.15 percent copper (Continental Minerals Corporation, 

2010b). This deposit contains nearly three times as much copper as 

Xietongmen, and exploration of this mineralized body is ongoing. 

Although the resource does not contain molybdenum, a table in 

Rebagliati and others (2009) suggests that molybdenum grades 

may range from 0.005 to 0.015 percent. The combined resource 

for Xietongmen/Newtongmen is 1,085,000,000 t at 0.30 percent 

copper, 0.22 g/t gold, and 1.20 g/t silver, representing more than 

3,000,000 t of copper.

The main orebody at Newtongmen is made up of quartzpyrite-chalcopyrite-molybdenite-biotite veins and veinlets that 

occur primarily in potassically altered rock (biotite-magnetitequartz-K-feldspar); mineralization is less well developed in 

the phyllically altered rock, which overprints some areas of 

potassic alteration. Propylitic alteration is only sporadically 

developed and may be related to post-mineralization faulting 

(Rebagliati and others, 2009).

The age of the Xietongmen/Newtongmen deposit is uncertain. 

Jurassic igneous rocks interpreted to be directly related to the 

deposit were dated at 174 to 171 Ma by Tafti and others (2009) 

using U-Pb methods on zircons. They also determined a Re-Os 

date on molybdenite from disseminated mineralization in drill core 

of 174 Ma. In contrast, two independent Ar-Ar age determinations 

on sericite from apparently ore-related hydrothermal alteration 

are late Eocene (38.1 Ma–Xu and others, 2009; 38.7 Ma–Rui and 

others, 2005). The situation is further complicated by an Eocene 

granodiorite pluton immediately to the northeast of the deposit that 

yielded a U-Pb zircon age of about 48 Ma (Tafti and others, 2009).

Although the deposits in the Xietongmen area may actually 

be Jurassic in age (145 to 200 Ma), we chose to include them in 

this assessment, primarily because of their location and because 

they are commonly referred to as part of the Gangdese porphyry 

belt in the Chinese literature. Other studies (see Wen and others, 

2008; Ji and others, 2009) have found only a few other Jurassic 

rocks in the southern Lhasa terrane.

Other prospects nearby include Zemoduola, Banongla, and 

Tangbai (see next section).

Qulong

Qulong, located about 40 km east of the capital, Lhasa, is 

the largest deposit in the tract. Unless otherwise referenced, all 

data in this description are derived from a comprehensive study 

of the deposit by Yang and others (2009). Mineralized rock at 

the site of Qulong was first noted as early as 1986, but it was not 

recognized as a porphyry copper deposit until 1994. Initial drilling 

was in 2002, when more than 400 m of >0.5 percent copper was 

encountered. The property has been explored since 2006 by the 

Table C2. Porphyry copper deposits in tract 142pCu8712, Gangdese—China.

[Ma, million years; Mt, million metric tons; t, metric ton; g/t, gram per metric ton; %, percent; 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, 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

Xietongmen/

Newtongmen

29.384 88.407 NA not 

resolved

1,085 0.30 n.d. 0.22 1.20 3,310,000 Rebagliati and others (2009)

Qulong 29.625 91.594 Cu-Mo 16 1,778 0.45 0.045 n.d. 3.9 8,000,000 Hou and Cook (2009), 

Yang and others (2009)

Jiama 29.703 91.765 NA 15.2 1,006 0.39 0.046 0.095 5.6 3,920,000 China Gold International 

(2010), Tang and others (2010)
50 Porphyry Copper Assessment of the Tibetan Plateau, China

Xizang Zhongsheng Mineral Resources Company, and more than 

80,000 m of drilling to depths of 850 m have been completed; the 

deposit is apparently being prepared for production.

Singer and others (2008) provide a resource number 

of 1,517,000,000 t at 0.52 percent copper, 0.03 percent 

molybdenum and 3.9 g/t silver. These data indicate a total 

copper resource of about 7,900,000 t, but unverified press 

reports indicate a total resource closer to 10,000,000 t of copper. 

Assay cross-sections published as figure 17 in Yang and others 

(2009) suggest the deposit is much larger, because the zone 

where copper is greater than 0.6 percent is about 400 m wide at 

the limit of drilling (about 800 m), and the zone where copper is 

greater than 0.3 percent is nearly 1.5 km wide at the same depth.

The deposit crops out on the surface, and is associated 

with a Miocene intrusion, termed the P porphyry, which has an 

outcrop area of about 0.2 km2. This 17.6 Ma porphyry intrudes 

an earlier intrusion, the 19.5 Ma Rongmucuola pluton. Country 

rocks also include several Jurassic granitoid bodies and 

Jurassic volcanic rocks. Molybdenite from the ore zone has 

been dated by the Re-Os method at 16.4 Ma (Meng and others, 

2003a) and 16.0 Ma (Rui and others, 2003).

Hydrothermal alteration assemblages displayed at Qulong 

are typical of those associated with other porphyry copper 

deposits. The core zone exhibits potassic alteration that includes 

K-feldspar, biotite, and anhydrite. A widespread surrounding 

zone of propylitic alteration includes chlorite and epidote. Both 

these alteration assemblages are overprinted by widespread 

feldspar-destructive alteration, both phyllic (quartz-sericite 

pyrite) and argillic (clay minerals). Daughter minerals in fluid 

inclusions from veinlet quartz at Qulong contain a complex 

assemblage including chalcopyrite and several unidentified 

copper-bearing minerals, in addition to the expected halite and 

sylvite (Yang and others, 2006).

Other deposits and prospects in the immediate area include 

Jiama, Lakang’e, and Xiangbeishan (see below and next section).

Jiama

Most of the ore at the Jiama deposit, about 15 km northeast 

of Qulong, is best termed skarn and hornfels. Information about 

Jiama, except when otherwise referenced, is derived from Deng 

and others (2009). There was small-scale lead mining at the 

site before the 1950s, and initial exploration by the Chinese 

government prior to 1990 delineated a 3.6-km-long mineralized 

zone. During 1991 through 1999, the Tibet Geological and Mineral 

Resource Bureau continued exploration, completing 31 diamond 

drill holes with a total drilled length of 10,091 m, and excavating 

several short adits and some surface trenches. Subsequently, 

four separate mining licenses were issued and four small-scale 

mining operations were active until 2007. At that time, the Tibetan 

government stopped mining and consolidated the mining and 

exploration licenses under a complex joint venture in which China 

Gold International Resources Corporation Ltd., a Hong Kong 

company, has the major interest. Since then, nearly 300 diamond 

drill holes with a total drilled length of more than 110 km have 

been completed. Mining commenced in July of 2010, with plans to 

expand capacity soon.

As of June 30, 2010, the combined resource (measured, 

indicated, and inferred) for the skarn ore body and the hornfels 

ore body was 1,006,000,000 t of ore at 0.39 percent copper, 0.046 

percent molybdenum, 0.095 g/t gold, and 5.6 g/t silver at a cutoff 

grade of 0.3 percent copper or 0.03 percent molybdenum. This 

indicates a total copper resource of about 3,900,000 t. Moreover, the 

most recent drilling has encountered a “grano-porphyry type coppermolybdenum” mineralized body that appears to underlie the skarn 

deposit (China Gold International, 2010), and Jiama will almost 

certainly expand. A sophisticated remote sensing study demonstrated 

that hydrothermal alteration extends well beyond the explored part of 

the district (Guo and others, 2010).

The skarn orebody forms a thin stratiform layer that 

approximately follows the contact between Jurassic marble and 

overlying Cretaceous clastic rocks. Thickness of this layer ranges 

from about 2 to 240 m, and it is at least 2,400 m long along the strike 

direction, and 190 to 1,900 m wide downdip. Skarn mineralization 

consists of variable amounts of chalcopyrite, bornite, molybdenite, 

galena, sphalerite, and pyrite in a silicate gangue of garnet, diopside, 

plagioclase, wollastonite, K-feldspar, and quartz. Less abundant 

minerals include chalcocite, enargite, tetrahedrite, covellite, electrum, 

malachite, silver, and cobaltite. A much larger volume of lower-grade 

hornfels in the Cretaceous clastic rocks above the skarn contain 

much the same sulfide mineral assemblage in fractures.

A sequence of dikes composed of diorite, quartz diorite, 

granodiorite porphyry monzogranite porphyry, and granite porphyry 

are found throughout the orebodies (Tang and others, 2010). These 

dikes have high-K calc-alkaline compositions, and their silica contents 

range from about 60 to 73 percent. The have compositions similar to 

other igneous rocks in the Gangdese belt, characterized by relatively 

low abundances of niobium, tantalum, and yttrium, and relatively high 

barium and strontium. Four zircon U-Pb ages from these dikes range 

from 16.3 to 14.8 Ma. A Re-Os date on molybdenite from the deposit 

suggests mineralization at about 15.2 Ma, which matches the age 

found by Ying and others (2010) with a 27-sample Re-Os isochron.

A study of fluid inclusions at Jiama found evidence for 

supercritical saline fluids at temperatures up to 500° C that 

have hydrogen and oxygen isotope signatures typical of fluids 

of magmatic origin (Li and others, 2011b). The inclusions also 

contained methane, ethane, and propane, suggesting that the deposit 

formed in a relatively reducing environment.

Prospects, Mineral Occurrences, and Related 

Deposit Types

The tract contains more than 20 porphyry copper prospects 

(table C3).

Zhunuo

Zhunuo was discovered in 2004 through the reprocessing of 

regional geochemical data (Zheng and others, 2006), and is the 

westernmost identified porphyry copper system in the Gangdese 

tract. Results from five drill holes and sampling in two tunnels 

in one of three mineralized areas indicate a resource of about 

1,000,000 t of copper grading 0.83 percent copper and 340 t of silver 
Appendix C. Porphyry Copper Assessment for Tract 142pCu8712, Gangdese—China 51

Table C3. Significant prospects and occurrences tract 142pCu8712, Gangdese—China.

[Ma, million years; Mt, million metric tons; t, metric ton; g/t, gram per metric ton; %, percent]

Name Latitude Longitude Age (Ma) Comments Reference

Zhunuo 29.66 87.47 13.7 Conceptual resource estimate of 120 Mt at 0.83% Cu,

0.3 g/t Au, 2.65 g/t Ag.

Zheng and others (2007a), 

Zheng and others (2007c)

Luobuzhen 29.50 88.00 Miocene? Location very approximate Chen and others (2008)

Zemoduola 29.38 88.35 unknown Xietongmen area; few details; location from Fig. 2 

of Xu and others (2009); may be Jurassic

Xu and others (2009)

Banongla 29.40 88.45 unknown Xietongmen area; few details; location from Fig. 2 

of Xu and others (2009); may be Jurassic

Xu and others (2009)

Tangbai 29.36 88.69 unknown Xietongmen area; few details; location from Fig. 2 

of Xu and others (2009); may be Jurassic

Xu and others (2009)

Jiru 29.69 88.78 Miocene? Drilling in 2007 Zheng and others (2007a), 

Zheng, Duo, Zhang, and others (2007b)

Gangjiang 29.60 89.95 14 Nimu area; provisional resource of 47 Mt at 1.1% Cu 

(oxide); also reported as 1.5 mt of Cu, at 0.45% Cu, 

0.12 g/t Au, 5 g/t Ag

Central China Goldfields (2008), 

Hou and Cook (2009)

Dubuqu 29.56 90.00 Miocene Nimu area; raw prospect Central China Goldfields (2008)

Tinggong 29.59 90.05 15.5 Nimu area; 5 drill holes through 2007; intercepts of 

0.34% Cu, 0.02% Mo; oxide copper being mined; a 

resource of >1 Mt of Cu at a grade of 0.5% also reported

Central China Goldfields (2008), 

Hou and others (2009)

Zongxun 29.49 90.05 Miocene Nimu area; raw prospect Central China Goldfields (2008)

Nanmu 29.47 90.82 14.8 Resource reported of >0.2 Mt of Cu, 

at a copper grade of >0.3%

Qu and others (2007), 

Hou and others (2004, 2009)

Yuejingou 29.33 91.16 Oligocene? Kelu-Chongmuda skarn belt; Cu skarn deposit Wang (2010)

Kelu 29.36 91.41 Oligocene? Kelu-Chongmuda skarn belt; Cu-Au skarn deposit Li and others (2005)

Lakang'e 29.58 91.48 13.6 Limited information Qu and others (2007), 

Hou and others (2004)

Xiangbeishan 29.58 91.78 Miocene? Porphyry and skarn-type mineralization Zheng and others (2007a), 

Rui and others (2005)

Liebu (Nuri) 29.32 91.80 23 Kelu-Chongmuda skarn belt; Porphyry-style 

mineralization below Cu-Ag skarn deposit; limited drilling

Li and others (2006)

Mingze 29.25 91.86 Oligocene to 

early Miocene?

Porphyry-style mineralization below Cu-Mo veins; 

limited drilling

Li and others (2006)

Chengba 29.25 91.87 Oligocene to 

early Miocene?

Kelu-Chongmuda skarn belt; Cu-Au skarn deposit Li and others (2006)

Chongmuda 29.27 91.91 21.4 Kelu-Chongmuda skarn belt; Skarn deposit, cross-cut by 

porphyry-style veins

Zheng and others (2007a), Li and others 

(2005), Beaudoin and others (2005)

Bangpu 29.91 91.97 15.3 Kelu-Chongmuda skarn belt; Polymetallic replacement 

deposit underlain by porphyry-style mineralization

Hou and others (2009), 

Meng and others (2003b)

Xiamari 29.86 92.29 Miocene? Limited information Rui and others (2005)

Demingding 29.61 92.58 Miocene? Three mineralized zones; Cu grade near 0.1% 

but Mo grades of 0.05–0.1%

Zheng and others (2007a)

Chuibaizi 29.68 92.68 Miocene? Five mineralized zones; limited information Zheng and others (2007a)

Jiagangxuweshan 30.74 88.64 21.4 W-Mo-Bi vein deposit Wang and others (2007)

Sharang 30.18 92.68 ca. 47 Large Mo porphyry related to granite Gao and others (2010), 

Qin and others (2008)

Tangbula 29.91 93.07 19.9 Porphyry deposit with both Mo- and Cu-rich zones Zhang and others (2008)
52 Porphyry Copper Assessment of the Tibetan Plateau, China

grading 2.65 g/t silver (Zheng and others, 2007a). These data 

indicate about 120,000,000 t of ore. The area was actively 

explored in 2006 and 2007 by South China Resources PLC, 

who made a similar resource estimate (termed conceptual) 

of 120,000,000 t of ore at 0.88 percent copper and 2.77 g/t 

silver (South China Resources, 2006). In December of 2007, 

South China Resources announced it was withdrawing from 

further negotiations on the Zhunuo Copper Project, and no 

more recent information is available. The property is presently 

controlled by Qinghai Province Geermu Zangge Kalium 

Fertiliser Company Limited.

Three Miocene porphyry stocks and three associated 

mineralized zones within those stocks and their wall rocks have 

been identified at Zhunuo. Ore minerals include malachite, 

azurite, cuprite, native copper, chalcopyrite, pyrite, and 

molybdenite. Alteration assemblages are zoned from a central 

potassic zone through phyllic and propylitic zones; most of 

the mineralized rock is in the phyllic zone (Zheng and others, 

2007c); South China Resources, 2006). The intrusions contain 

complexly zoned zircons (Zheng and others, 2007c). Their rims 

yielded an U-Pb age of about 13.3 Ma, which was interpreted 

to be the age of the plutons. Inherited ages of about 63, 50, 

and 16 Ma were determined deeper within the zircon crystals. 

A Re-Os isochron age of 13.7 Ma was also determined on 

molybdenite from the deposit (Zheng and others, 2007c).

Based on examination of unprocessed satellite imagery, 

there are several other centers of hydrothermal alteration 

between Zhunuo and the Xietongmen area.

Xietongmen/Newtongmen Area

A number of prospects and showings, including Banongla, 

Zemoduola, and Tangbai, have been identified in the region 

surrounding the Xietongmen and Newtongmen deposits.

Zemoduola is about 7 km west of Xietongmen. Exploration 

is limited, but soil and rock geochemical studies suggest that it is 

also a center for copper and gold mineralization (Lang and others, 

2007). Banongla and Tangbai are Cu-Au occurrences that are 

shown on a map in Xu and others (2009); they are described as 

similar to Xietongmen/Newtongmen, but no further details are 

known, as they were not actively explored by Continental Minerals.

Another copper-polymetallic deposit, Luobuzhen, is described 

as being near the Xietongmen area, but its location is 

not well established (Chen and others, 2008).

Southwest of the Newtongmen prospect, Dongga is 

described by Beaudoin and others (2005) as a gold- and silver-rich 

polymetallic vein that consists of meter-thick west-northwesttrending veins. Early in the exploration of Xietongmen, the name 

Dongga was erroneously applied to the porphyry copper deposit.

Jiru

Jiru was discovered in 2001, and a brief description is given by 

Zheng and others (2007b). The prospect is centered on a composite 

porphyritic granite and monzonitic granite stock. Silicification in 

the core grades outward to phyllic and propylitic hydrothermal 

alteration zones. Ore minerals include malachite, azurite, 

chalcopyrite, pyrite, molybdenite, galena, and bornite. Exploration 

was described as ongoing drilling. Zheng and others (2007b) states 

that the deposit was found by reprocessing of geochemical data 

to enhance minor geochemical anomalies. Re-Os data (Gong and 

others, 2008) indicate that Jiru is Eocene in age (51–48 Ma), similar 

to one possible age for the nearby Xietongmen deposit.

Nimu Area

Between May 2006 and June 2009, the Nimu area was 

explored by Central China Goldfields, a London-based company, 

under the terms of a joint venture agreement with the Sichuan 

Bureau of Metallurgy and Geological Exploration (SBGME). In 

2009, SBGME purchased Central China Goldfields’ interest and the 

prospect is now under their control. The project area includes the 

Gangjiang, Tinggong, Dubuqu, and Zongcun prospects (table C3).

Gangjiang (also known as Chongjiang) was listed as a 

deposit by Singer and others (2008), but the resource number 

provided was based on only seven drill holes. The system is being 

actively drilled, and its limits are undefined. For the entire project, 

a pre-2006 resource was estimated at 600,000 t of oxide copper 

at grades between 1.07 and 1.1 percent copper (corresponding to 

about 55,000,000 t of ore), along with 236,000 t of sulfide copper 

at grades between 0.29 and 0.34 percent copper (corresponding to 

about 70,000,000 to 80,000,000 t of ore), with molybdenum grades 

between 0.02 and 0.08 percent (Central China Goldfields, 2006). 

This area was discovered in 1990 by the use of stream-sediment 

geochemical studies (Central China Goldfields, 2006; Zheng, Duo, 

Cheng, and others, 2007; Kong and others, 2007). There is a small 

open-cut copper mine adjacent to Tinggong, operated by SBGME.

The area is about 100 km west of Lhasa, in Nimu county. 

Of the seven areas of interest, four (Gangjiang, Bairong, 

Ronggangmeng, and Xiaoing) are distributed around the margins 

of a “rhyodacite” porphyry intrusion; these are represented in the 

database (table C3) by Gangjiang. The other three (Tinggong, 

Dubuqu, and Zongcun) are distal (8 to 20 km southeast) to this 

system, but also related to small silicic intrusions (Central China 

Goldfields, 2007). Li and others (2007), using 40Ar/39Ar methods, 

obtained dates of about 17 Ma on hornblende from a pre-ore 

monzogranite, about 12.5 Ma from post-ore quartz diorite, and 

about 14.5 Ma from post-ore granodiorite, along with alteration 

ages on hydrothermal sericite of about 12 Ma. Leng and others 

(2010) obtained zircon U-Pb dates of 14.7 Ma on a biotite quartz 

monzonite and 12.0 Ma on the rhyodacite.

Exploration activity was principally focused on the Gangjiang 

prospect, where 21 diamond drill holes were completed, 18 of 

which encountered significant mineralized rock (Central China 

Goldfields, 2008). Numerous intercepts of tens of meters at 

grades of 0.1 to 0.3 percent copper and 0.01 to 0.03 percent Mo 

were encountered in these drill holes (Central China Goldfields, 

2007). Gold values as high as 0.7 g/t and silver values as high as 

12 g/t were found in the same intervals. Several areas at Ganjiang 

contain small amounts of enriched oxide-facies copper at or near 

the surface, and SBGME reported a resource of 47,000,000 t of 1.1 
Appendix C. Porphyry Copper Assessment for Tract 142pCu8712, Gangdese—China 53

percent copper (oxide facies). Fluid inclusion studies at Gangjiang 

show that the deposit exhibits a typical porphyry inclusion 

assemblage of early high-temperature supercritical fluids followed 

by lower-temperature brine coexisting with a low-salinity vapor 

(Xie and others, 2007). The lack of abundant propylitic alteration 

suggests that the deposits have been eroded to a depth of 2 to 3 km 

(Leng and others, 2010).

At Bairong, surface sampling found low copper contents, and 

no drilling was undertaken. However, a resource of 72,000,000 t 

at 0.29 percent copper was reported by SBGME. Initial channel 

sampling at Xiaqing and Ronggangmeng also encountered 

relatively low grade mineralization, less than 0.1 percent copper, 

and no drilling was undertaken (Central China Goldfields, 2008). 

In this assessment, these three prospects are considered to be part 

of the Gangjiang prospect because of proximity (table C3); the 

alteration envelopes of all four appear to overlap.

At Tinggong, at least 5 drill holes were completed by 

2007; these encountered numerous intercepts of tens of meters 

with copper grades up to 0.34 percent and Mo grades up to 

0.02 percent (Central China Goldfields, 2008). Yang and 

others (2005, 2006) studied the daughter minerals in fluid 

inclusions from phenocryst and veinlet quartz at Tinggong 

and found a complex assemblage including chalcopyrite and 

several unidentified copper-bearing minerals, in addition to the 

expected halite and sylvite. The inclusions also indicate boiling 

of the ore-forming fluid took place at about 360° C.

No detailed ground work was completed at the Dubuqu and 

Zongxun prospects, and no information is available about the 

exploration conducted by SBGME between 2000 and 2006.

Hydrothermal alteration is typical for porphyry copper 

deposits, with potassic alteration zoned outward through poorlydeveloped phyllic and propylitic zones. The copper-bearing rocks 

are found primarily in rocks that display potassic alteration (Zheng 

and others, 2007a).

Miocene intrusive rocks from the Nimu project area include 

granodiorite porphyry, monzogranite porphyry, and quartz 

monzonite porphyry, and silica contents range from about 65 to 

71 percent (Gao and others, 2003). Both niobium and yttrium 

abundances are very low (<10 ppm). Initial ratios of 87Sr/86Sr range 

from 0.7056 to 0.7064 and eNd values range from -2.3 to +0.9.

Qu and others (2007) determined Re-Os ages on five 

molybdenite samples from Gangjiang; the model ages range 

from 13.8 to 14.2 Ma, and an isochron age was reported as 

13.99 ± 0.16 Ma. An 40Ar/39Ar isochron age of 13.45 ± 0.26 Ma 

was also determined for biotite from Gangjiang. In addition, 

Hou and others (2004) determined a Re-Os isochron age for 

molybdenite from Gangjiang of 14.04 Ma, whereas Li and 

others (2004) determined a Re-Os model age for Gangjiang of 

13.88 Ma and for Tinggong of about 15 Ma.

Nanmu

Nanmu, also called Dabu, is located between the Nimu 

project and the Qulong-Jiama area, about 35 km southwest of 

the city of Lhasa. The following description is derived primarily from Qu and others (2007). The mineralized body is 

irregular in form, and is mostly in cataclastic granite that hosts 

the Miocene porphyries. The prospect is reported to contain 

more than 200,000 t of copper, at grades exceeding 0.3 percent, 

which corresponds to less than 67,000,000 t of ore. Ore minerals include chalcocite, covellite, malachite, chalcopyrite, pyrite, 

molybdenite, bornite, and sphalerite. Alteration assemblages are 

zoned from a central potassic zone through silicic, phyllic, and 

propylitic zones. Fluid inclusion studies revealed a typical porphyry inclusion assemblage of early high-temperature (>500 °C) 

supercritical fluids followed by lower-temperature brine coexisting with a low-salinity vapor (Zhang and others, 2003).

Gao and others (2003) provide major- and trace-element 

analyses, along with Sr-, Nd-, and Pb-isotope data for some 

of the porphyries at Nanmu. Silica contents range from about 

66 to 72 percent, and both Nb and Y are very low (<10 ppm). 

87Sr/86Sr initial ratios range from 0.7048 to 0.7051 and eNd

values range from -3.3 to +5.5.

SHRIMP U-Pb ages on zircons from Nanmu range 

from about 17 to 14 Ma (Qu and others, 2009), and the age of 

mineralization, determined by Re-Os dating of molybdenite, is 

about 14.8 Ma (Hou and others, 2004, 2009; Qu and others, 2007; 

Li and others, 2004).

Qulong-Jiama Area

Immediately to the east of Lhasa (20–60 km), this group 

includes the Xiangbeishan and Lakang’e prospects in addition to 

the large deposits at Qulong and Jiama. Xiangbeishan, discovered 

in 2005, is about 10 km east of Qulong. Both porphyry and skarntype mineralization is present and the skarn has copper grades as 

high as 2.3 percent (Zheng and others, 2007a). Lakang’e is about 

20 km southwest of Qulong. Chemical analyses, isotopic data, 

and Ar-Ar ages are reported in Qu and others (2007). A Re-Os 

isochron age of 13.6 Ma was determined by Hou and others (2004). 

However no description of the mineralized rock at Lakang’e 

was found. Another potential porphyry copper prospect, named 

Qiangdui, is briefly described by Jiang and others (2006). It is 

described as near Lakang’e, but coordinates are not available and 

we could not locate this prospect.

Kelu-Chongmuda Skarn Belt

A suite of copper-gold skarn deposits (some contain 

molybdenum) has recently been discovered in a belt about 

50 to100 km southeast of Lhasa (Li and others, 2006; Liand 

others, 2005). The deposits are related to high-K calc-alkaline 

rocks associated with the late collisional stage that are 

primarily of Oligocene and Miocene age. Many of these skarn 

deposits exhibit associated porphyry-style mineralization in the 

igneous rocks, and porphyry copper deposits may be present 

at deeper levels beneath these deposits (Li and others, 2011a; 

Li and others, 2006). Li and others (2006) provide a map with 

17 deposits and occurrences; the most notable are Yuejingou, 

Kelu, Liebu, Mingze, Chengba, and Chengmuda.

Yuejingou, the westernmost deposit in the skarn belt, 

is about 40 km due south of Lhasa. It is described by Wang 
54 Porphyry Copper Assessment of the Tibetan Plateau, China

(2010) and Han and others (2008) as a copper-polymetallic 

deposit and consists of several skarn layers. Fluid inclusion 

studies by Wang (2010) indicate filling temperatures as high as 

430° C, which is indicative of the porphyry environment.

Kelu is about 45 km southeast of Lhasa. It is described by Li 

and others (2005) as a medium-sized copper-gold skarn deposit.

Liebu, also known as Nuri, is located about 40 km east 

of Kelu. It was described in Li and others (2005) as a large 

copper-silver skarn deposit, with a copper resource of more 

than 500,000 t, based on limited drilling. A K-Ar age of about 

23 Ma was determined on quartz diorite porphyry. Li, Qin, 

and others (2011) provided a map that illustrates a number of 

layered skarn bodies interlayered with granitoid dikes. Jiang 

and Jiang (2006) described copper and copper-molybdenumtungsten skarn deposits with copper grades commonly between 

0.4 and 0.8 percent, and suggested that porphyry copper 

mineralization was found below the skarns.

Mingze is on the south bank of the Yarlung-Tsangpo 

River and is about 10 km southeast of Liebu and 50 km 

southeast of the Qulong deposit. The deposit consists of a 

number of discrete hydrothermal veins that contain copper 

and molybdenum, but has evidence of porphyry molybdenum 

mineralization in the deeper parts of the deposit. Limited 

drilling has been done and no resource has been delineated 

(Li, Qin, and others, 2011).

Chengba is a medium-sized copper-gold skarn deposit just 

1.5 km east of the Mingze deposit (Li and others, 2005).

Chongmuda is a medium-sized copper-gold skarn deposit 

crosscut by porphyry style quartz-chalcopyrite veins (Beaudoin and 

others, 2005). It is located about 45 km south of Qulong and 

5 km east of the Mingze deposit, on the south bank of the YarlungTsangpo River. A K-Ar age on hornblende from the associated 

pluton was reported to be 21.4 Ma by Li and others (2005), whereas 

a zircon U-Pb date on the pluton is 27.7 Ma (Mo and others, 2008). 

Li and others (2006) report Re-Os dates on molybdenite from the 

deposit that range from 41 to 37 Ma; it is implausible that this age 

can represent mineralization that cuts a pluton with a 28 Ma date, 

so the mineralization age remains in doubt.

Bangpu is variously described as a copper-polymetallic 

deposit (Meng and others, 2003b) and a molybdenum-copper 

porphyry deposit (Zhou and others, 2010). The deposit is 

somewhat north of most of the other porphyry deposits in the 

Gangdese belt, about 75 km northeast of Lhasa. Few details 

are available, and there is no measured resource, but Meng and 

others (2003b) dated molybdenite from the deposit at about 

15 Ma, similar to other porphyry deposits in the Gandese belt. 

Eastern Area

Located 60–100 km east of the Qulong-Jiama deposits, 

this group of relatively poorly-documented prospects 

includes Xiamari, Chuibaizi, and Demingding. Chubaizi and 

Demingding are well to the east of the Qulong-Jiama area, 

about 130 km east of Lhasa (Figure 1 of Zheng and others, 

2007a). Chuibaizi is also mentioned and shown on a map by 

Rui and others (2005).

Chuibaizi was discovered using stream-sediment 

geochemistry in 1991–1996 and is related to quartz porphyry 

and porphyritic biotite monzogranite that intrudes Middle 

Jurassic rocks. Five separate mineralized zones contain 

chalcocite, malachite, chalcopyrite, molybdenite, pyrrhotite, 

pyrite, and sphalerite. Hydrothermally altered rocks contain 

silicic, phyllic, argillic, and propylitic assemblages (Zheng and 

others, 2007a).

Demingding, discovered in 2003, consists of three 

separate mineralized zones. Its geology is similar to that at the 

Chuibaizi deposit (Zheng and others, 2007a). Copper grades 

are relatively low (near 0.1 percent), but the molybdenum 

grades range between 0.05 and 0.1 percent.

Xiamari is mentioned briefly in Rui and others (2005), 

but no details about the prospect are available and the location 

is only approximate. 

There are apparently more undocumented prospects 

in the area, because Zheng and others (2007a), after briefly 

describing these eastern prospects, state that “In addition, 

several tens of occurrences of porphyry Cu-(Au-Pb-Zn) have 

been recognized in the past years, indicating a great potential 

of mineralization in the Gangdese belt.”

Related Deposits

Jiagangxueshan, Tangbula, and Sharang are three other 

prospects that are not porphyry copper systems, but merit 

mention as they may cast some light on the metallogenic 

development of the tract.

Jiagangxueshan is the first major discovery in the 

far northern part of the tract, about 160 km north of the 

Xietongmen area. It is a tungsten-molybdenum-bismuth 

polymetallic vein deposit, and has a zircon U-Pb age of about 

22.2 Ma and a molybdenite Re-Os date of about 21.4 Ma 

(Wang and others, 2007).

Tangbula (Zhang and others, 2008) is the easternmost 

porphyry in the Gangdese belt and is nearly 200 km east of 

Lhasa. The deposit includes two distinct mineralized zones. The 

larger zone is composed primarily of molybdenite and quartzmolybdenite pyrite veins; surface sampling indicates grades 

of approximately 0.17 percent molybdenum and 0.05 percent 

copper. Surface sampling at the other zone indicates average 

grades of 0.16 percent molybdenum and 0.21 percent copper. 

A small copper-oxide body has reported grades of 0.01 percent 

molybdenum and 0.57 percent copper. U-Pb geochronology 

indicates that the granodiorite porphyry associated with the 

deposit was emplaced at about 19.9 Ma (Xia and others, 2010). 

The geochemical signature of the granodiorites is similar to that 

of the rocks associated with porphyry copper deposits in the 

Gangdese belt (Guo and others, 2007).

The Sharang prospect (Qin and others, 2008) appears 

to be a molybdenum (only) porphyry deposit, though 

no copper abundance data are available. The prospect 

is associated with a granite porphyry and hydrothermal 

alteration covers an area of nearly 10 km2

. The mineralized 

body is believed to extend to nearly 800 m depth, based 
Appendix C. Porphyry Copper Assessment for Tract 142pCu8712, Gangdese—China 55

Table C4. Principal sources of information used for tract 142pCu8712, Gangdese—China.

[NA, not applicable]

Theme Name or Title Scale Citation

Geology

Regional geology of Xizang (Tibet) Autonomous 

Region 1:500,000 Bureau of Geology and Mineral Resources 

of the Xizang Autonomous Region (1993)

Geological map of the People's Republic of China 1:2,500,000 China Geological Survey (2004)

Mineral 

occurrences

Porphyry copper deposits of the world: database, 

map, and grade and tonnage models NA Singer and others (2008)

Metal Mining Agency of Japan mineral deposit 

database NA Metal Mining Agency of Japan (1998)

World minerals geoscience database NA Natural Resources Canada (2010), 

Kirkham and Dunne (2000)

Geological Survey of Japan mineral resources 

map of East Asia NA Kamitani and others (2007)

Predicted target areas for Gangdese copper 

porphyry deposits (Figure 3) NA She and others (2009)

Stream-sediment 

geochemistry

Copper geochemical map 1: 12,000,000 China Geological Survey (2010b)

Bismuth geochemical map 1: 12,000,000 China Geological Survey (2010a)

on electrical methods. Originally suspected to be Eocene, 

the granite has been dated at about 47 Ma by zircon U-Pb 

methods (Gao and others, 2010).

Exploration History

Exploration for porphyry copper deposits in this tract is 

at a relatively early stage, as the porphyry copper model was 

not well-known in China until the 1960s, when scientific and 

industrial activity was renewed after a long period of warfare 

and internal turmoil. Subsequently, basic geologic mapping 

and detailed geochemical and geophysical surveys have been 

completed, resulting in the discovery of the numerous deposits and 

prospects described here. There has been extensive exploration 

for outcropping deposits in the eastern part of the tract, but the 

western part is still remote and poorly known. Most of the tract 

is extremely sparsely populated, and access is poor. Most of the 

tract is at altitudes exceeding 4,000 m and 6,000 m peaks are 

numerous.

The current level of exploration activity in this tract is not 

well known, however, with the recent buyouts of Continental 

Minerals and Central China Goldfields, we believe that only 

Chinese exploration companies are now exploring for porphyry 

copper deposits in this part of China.

Stream-sediment geochemical studies conducted by 

the China Geological Survey have been instrumental in the 

discovery of many of the deposits and prospects in this tract. 

A nationwide geochemical map for copper (China Geological 

Survey, 2010b) shows prominent anomalies coincident 

with the Xietongmen, Jiru, Nimu, Nanmu, Qulong-Jiama, 

Xiamari, and Chuibaizi areas. But numerous other anomalies 

are displayed on this map, including some in the western part 

of the tract. Sophisticated modeling techniques were used 

to combine geochemical data for copper, molybdenum, and 

gold, to produce a porphyry copper prospectivity map for the 

eastern part of the tract (Zuo, Cheng, and Agterberg, 2009; 

Zuo, Cheng, Agterberg, and Xia, 2009). Aspects of this map 

were used to refine the boundaries of the permissive tract.

Sources of Information

Principal sources of information used by the 

assessment team for delineation of the tract are listed in 

table C4. No geophysical data at an appropriate scale were 

available for the assessment. Geochemical maps were 

available only for copper and bismuth among porphyryrelated elements.

Grade and Tonnage Model Selection

The tract includes three known deposits, Xietongmen/

Newtongmen, Qulong, and Jiama. Xietongmen has a high 

gold grade (0.61 g/t), whereas Newtongmen’s gold grade 

is only 0.13 g/t. Qulong has been extensively explored, 

but there is no information about the abundance of gold. 

Qulong contains substantial molybdenum, with a grade of 

0.045 percent, but Xietongmen has no reported molybdenum 

grade. The Jiama skarn has relatively high grades for both 

gold and molybdenum, but nothing is known about the metal 

abundances in the underlying porphyry deposit. Until more 

grade information is known for these deposits, it is most 

appropriate to use the general porphyry copper model for the 

assessment of the Gangdese tract.
56 Porphyry Copper Assessment of the Tibetan Plateau, China

Table C5. Undiscovered deposit estimates, deposit numbers, tract area, and deposit density for tract 142pCu8712, Gangdese—China.

[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; density, 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/km2

) N90 N50 N10 N05 N01 Nund s Cv

% Nknown Ntotal

9 13 50 50 50 22.3 15.7 71 3 25 239,860 0.00010

Estimate of the Number of Undiscovered 

Deposits

Rationale for the Estimate

There are three known deposits and at least 23 porphyry 

copper prospects in the tract. Furthermore, the analysis by She and 

others (2009) identified 23 additional high-priority target areas in 

the eastern third of the tract, in addition to the prospects compiled 

for this study. Much of the area is extremely rugged and difficult 

of access, particularly the western part, where exploration has been 

limited. Continued exploration in this tract will likely result in 

numerous additional discoveries.

A nationwide geochemical map for copper (China 

Geological Survey, 2010b) shows prominent anomalies 

coincident with the Xietongmen, Jiru, Nimu, Nanmu, 

Qulong-Jiama, Xiamari, and Chuibaizi areas. Numerous other 

anomalies, not associated with known deposits or prospects, 

are displayed on this map, including some in the western, 

poorly explored part of the tract.

The presence of at least 23 prospects (and likely at least 

double that number) in a productive area, coupled with the 

poorly explored western part of the tract, led the assessment 

team to estimate a 90 percent chance of 9 or more undiscovered 

deposits in the tract. We believe that several of the 

presently-identified prospects will, upon thorough exploration 

and development, become deposits. Six of them (Zhunuo, 

Bairong, Gangjiang, Tinggong, Nanmu, and Demingding) 

already contain measured resources based on drill data. In 

contrast, the relatively small size of the tract limits the total 

number of undiscovered deposits that might exist there, so the 

team estimated 50 undiscovered deposits at the 10th percentile 

confidence level. The estimated mean number of undiscovered 

deposits is 22.3 (table C5).

Because of the subjective nature of the tract delineation, 

it could be misleading to place great credence in a calculated 

deposit density for this tract, but the team’s estimate is entirely 

consistent with worldwide deposit density estimates (Singer, 

2008; Singer and others, 2005).

A previous assessment (Yan and others, 2007) covered 

much of the tract (their Tract XI-2 and tract XI-3). They 

estimated about 13 mean undiscovered deposits, compared 

with our estimate of 22.3 (table C5). Continued exploration 

success in the years since their estimate was made can explain 

much of the difference between the two estimates. Also, She 

and others (2009) conducted an independent assessment of 

the Gangdese ore belt and estimated more than 100,000,000 t 

of copper reserves (including that already discovered), which 

is somewhat greater than the total predicted in this study. 

Combined with the three known deposits, this means that the 

tract probably contains 25 or more porphyry copper deposits.

Table C6. Results of Monte Carlo simulations of undiscovered resources for tract 142pCu8712, Gangdese—China.

[Cu, copper; Mo, molybdenum; Au, gold; Ag, silver; t, metric tons; Mt, 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 (t) 7,300,000 13,000,000 61,000,000 200,000,000 250,000,000 87,000,000 0.39 0.01

Mo (t) 71,000 180,000 1,400,000 5,900,000 8,200,000 2,400,000 0.34 0.02

Au (t) 130 260 1,500 4,900 6,500 2,200 0.38 0.02

Ag (t) 480 1,600 17,000 69,000 92,000 28,000 0.35 0.03

Rock (Mt) 1,700 2,900 13,000 40,000 49,000 18,000 0.41 0.01
Appendix C. Porphyry Copper Assessment for Tract 142pCu8712, Gangdese—China 57

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 1Tr

Material, metric tons 

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 

Figure C3. Cumulative frequency plot showing results of Monte Carlo computer simulation of undiscovered 

resources for tract 142pCu8712, Gangdese—China. k, thousand; M, million; B, billion; Tr, trillion.

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. C3), which shows the estimated resource amounts 

associated with cumulative probabilities of occurrence, 

as well as the mean, for each commodity and for total 

mineralized rock. 
58 Porphyry Copper Assessment of the Tibetan Plateau, China

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Appendix E. Assessment Team 63

Appendix D. Description of GIS files 

An ESRI geodatabase file (TIBET_pCu.gdb) containing 

three feature classes and an ESRI map document (TIBET_GIS.

mxd) are included with this report. These may be downloaded 

from the USGS website as zipped file GIS_SIR5090F_

appendix_D.zip, which also contains the data in shapefile format.

The feature classes (and shapefiles) are as follows:

TIBET_pCu_Tracts is a vector (polygon) feature class 

that represents the three 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 files.

TIBET _pCu_Deposits_prospects is a vector (point) 

feature class that represents the locations for known deposits 

(identified resources that have well-defined tonnage and 

copper grade) and prospects. The deposits and prospects 

are listed in tables in Appendix A, B, and C of this report. 

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 files.

TIBET _political_boundaries is a vector (polygon) feature 

class that represents the political boundaries in and adjacent to the 

study area. The data were extracted from the country and shoreline 

boundaries maintained by the U.S. Department of State (2009).

The files can be viewed with an included ESRI map 

document (version 9.3) named TIBET_GIS.mxd. 

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Appendix E. Assessment Team 

Steve Ludington is a research geologist with the 

USGS in Menlo Park, California. He received a B.A. in 

geology from Stanford University (1967) and a Ph.D. 

in geology from the University of Colorado (1974). He 

worked as an exploration geologist in Colorado, New 

Mexico, and Arizona before joining the USGS in 1974. 

His work with the USGS has included regional geologic 

studies, metallogenic and geochemical studies, wilderness 

studies, and mineral-resource assessments. He has done 

mineral-resource assessment work in the United States, 

Costa Rica, Bolivia, Mongolia, Afghanistan, and Mexico 

and was a coordinator for the 1998 USGS National Mineral 

Resource Assessment.

Jane M. Hammarstrom is a research geologist with 

the USGS in Reston, Virginia. She received a B.S. in 

geology from George Washington University in 1972 and 

an M.S. in geology from Virginia Polytechnic Institute 

and State University in 1981. She is Co-chief of the USGS 

Global Mineral Resource Assessment project and the task 

leader for the porphyry copper assessment. Jane has more 

than 30 years of research experience in igneous petrology, 

mineralogy, geochemistry, economic geology, and mineral 

resource assessment.

Gilpin R. Robinson, Jr. is a research geologist 

with the USGS in Reston, Virginia. He received a B.S. 

in geology from Tufts University (1973) and a Ph.D. in 

geology from Harvard University (1979). He 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.

Produced in the Menlo Park Publishing Service Center, California

Manuscript approved for publication, June 27, 2012

Edited by Jane Eggleston

Layout and design by Jeanne S. DiLeo
Ludington and others—Global Mineral Resource Assessment—Porphyry Copper Assessment of the Tibetan Plateau, China—Scientific Investigations Report 2010–5090–F