M A R C H 3, 18 4 9

U.S. DEPARTMENT OF THE INTERIOR

Geochemical Studies of Rare Earth Elements in the 

Portuguese Pyrite Belt, and Geologic and 

Geochemical Controls on Gold Distribution

Edited by David J. Grimes and S.J. Kropschot

A. Rare Earth Element Distribution in the Volcanic 

Lithostratigraphic Units of the Portuguese Pyrite Belt

By David J. Grimes, Robert L. Earhart, and Delfim de Carvalho

B. Geologic Setting and Geochemical Controls on the Distribution of 

Gold in the Portuguese Pyrite Belt

By Robert L. Earhart, Delfim de Carvalho, Vitor Oliveira, Jose T. Oliveira, and

Paulo Castro

U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1596–A–B

Prepared in cooperation with the 

Luso American Development Foundation, the 

Serviços Geológicos de Portugal, and the Serviço 

de Fomento Mineiro

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1998
For sale by U.S. Geological Survey, Information Services

Box 25286, Federal Center

Denver, CO 80225

Any use of trade, product, or firm names in this publication is for descriptive purposes only and

does not imply endorsement by the U.S. Government

Library of Congress Cataloging-in-Publication Data

U.S. DEPARTMENT OF THE INTERIOR

BRUCE BABBITT, Secretary

U.S. GEOLOGICAL SURVEY

Thomas J. Casadevall, Acting Director

Geochemical studies of rare earth elements in the Portuguese Pyrite Belt, and geologic

and geochemical controls on gold distribution / edited by David J. Grimes and 

S. J. Kropschot.

p. cm.—(U.S. Geoloigcal Survey professional paper ; 1596)

“Prepared with the support and cooperation of the Luso American Development 

Foundation, the Serviços Geológicos de Portugal, and the Serviços de Fomento 

Mineiro.”

Includes bibliographical references.

Contents: Rare earth element distribution in the volcanic lithostratigraphic units of 

the Portuguese Pyrite Belt / by David J. Grimes, Robert L. Earhart, and Delfim de 

Carvalho — Geologic setting and geochemical controls on the distribution of gold in 

the Portuguese Pyrite Belt / by Robert L. Earhart . . . [et al.].

1. Geochemistry—Portugal. 2. Rare earth metals—Portugal. 3. Gold ores—

Portugal. I. Grimes, D. J. (David J.), 1943–. II. Kropschot, S. J. (Susan J.) 

III. Luso-American Development Foundation. IV. Serviços Geológicos de Portugal.

V. Portugal, Serviços de Fomento Mineiro. VI. Series.

QE516.R2G435 1998

[553.4′94′09469—dc21 98—10121

CIP
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III

CONTENTS

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

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

Investigative Methods and Considerations ............................................................. 2 

Geologic Setting...................................................................................................... 2

Acknowledgments........................................................................................................... 5

A. Rare Earth Element Distribution in the Volcanic Lithostratigraphic 

Units of the Portuguese Pyrite Belt

By David J. Grimes, Robert L. Earhart, and Delfim de Carvalho

Introduction..................................................................................................................... 6

Geologic Considerations ................................................................................................. 6

Rare Earth Element Geochemistry.................................................................................. 9

Altered Rhyolites, Cercal Area ............................................................................... 9

Sub-belt Rhyolites................................................................................................... 9

Neves-Corvo Rhyolites ........................................................................................... 12

Sub-belt Basalts....................................................................................................... 12

Rare Earth Element Averages, Basalts and Rhyolites ............................................ 12

Conclusions and Recommendations ............................................................................... 13

B. Geologic Setting and Geochemical Controls on the Distribution of Gold 

in the Portuguese Pyrite Belt

By Robert L. Earhart, Delfim de Carvalho, Vitor Oliveira, Jose T. Oliveira, 

and Paulo Castro

Introduction..................................................................................................................... 14

Gold in Massive and Disseminated Sulfide Deposits ..................................................... 17

Gold in Massive Sulfide Deposits........................................................................... 17

Gold in Disseminated Sulfide Deposits .................................................................. 17

Chança Area.................................................................................................... 17

Salgadinho Area.............................................................................................. 18

São Domingos Area ........................................................................................ 21

Gold Distribution in Chert, Bedded Barite, and Other Rocks of Exhalative Origin....... 22

Gold Distribution in Ultramafic and Associated Rocks of the Mobile Belt ................... 25

Gold Distribution in Other Areas.................................................................................... 27

Conclusions..................................................................................................................... 27

References Cited ............................................................................................................. 28

Appendix A. Analytical Results for Selected Elements in Rocks from the Portuguese 

Pyrite Belt ....................................................................................................................... 31

PLATES

[Plates are in pocket]

1. Drill hole data, Salgadinho area

2. Geologic maps of the São Domingos and Serra Branca areas
IV CONTENTS

FIGURES

1. Generalized geologic map of the Iberian Pyrite Belt ....................................................................................................... 3

2. Generalized geologic map of the Portuguese Pyrite Belt showing general trends of volcanic sub-belts ........................ 4

3. Chondrite normalized distributions of rare earth elements in volcanic rocks in the Portuguese Pyrite Belt ................... 8

4. Tectonic setting of possible gold occurrences in the South Portuguese Zone.................................................................. 18

5. Geologic map of the Chança area showing drill hole and rock sample localities............................................................ 19

6. Index map of the São Luis-Salgadinho area..................................................................................................................... 20

7. Distribution trends of selected elements in proximal and distal settings of exhalative chert and 

baritic rocks, Aljustrel ...................................................................................................................................................... 23

8. Interpretative geologic cross section across Neves-Corvo anticline from Ferragudo manganese mine to Serpa 

manganese prospects and analytical results of selected elements from samples of proximal and distal exhalative

rocks collected on or near the line of cross section.......................................................................................................... 24

9. Geology of an area southeast of Ferreira do Alentejo, South Portugal............................................................................ 26

TABLES

1. Descriptions and locations of samples analyzed for rare earth elements......................................................................... 7

2. Rare earth element concentrations in volcanic rocks, Portuguese Pyrite Belt ................................................................. 10

3. Rare earth element concentrations in sub-belt rhyolites, Portuguese Pyrite Belt ............................................................ 11 

4. Hafnium, tantalum, and zirconium concentrations in sub-belt rhyolites, Portuguese Pyrite Belt ................................... 12

5. Correlation coefficients, rock samples in Portuguese Pyrite Belt .................................................................................... 15
1

GEOCHEMICAL STUDIES OF RARE EARTH ELEMENTS IN 

THE PORTUGUESE PYRITE BELT, AND GEOLOGIC AND 

GEOCHEMICAL CONTROLS ON GOLD DISTRIBUTION

ABSTRACT

Geochemical and geologic studies were conducted by

the U.S. Geological Survey and the Serviços Geológicos de

Portugal in the Portuguese Pyrite Belt in southern Portugal

during 1987 and 1988. Under a cooperative agreement, the

Serviços Geológicos de Portugal provided logistical support

and background information needed to carry out the investigations as well as technical assistance in one of the study

areas. Principal funding was provided by the Luso American

Development Foundation, supplemented by the U.S. Geological Survey and the Serviços Geológicos de Portugal.

The studies included (1) rare earth element distributions, (2) testing and development of geochemical methods,

and (3) identification of geologic and geochemical controls

on the distribution of gold. Reconnaissance and detailed

geologic studies were conducted and rock, soil, plant, and

water samples were collected for chemical analyses as part

of the geochemical surveys.

The Portuguese Pyrite Belt is the part of the Iberian

Pyrite Belt that trends eastward from near Seville in southern

Spain across southern Portugal. The Iberian Pyrite Belt is

about 230 km long and 30 km wide and the geology is structurally complex, consisting of Late Paleozoic volcanic and

sedimentary rocks. The Iberian Pyrite Belt is host to numerous copper-, zinc-, and lead-bearing massive sulfide deposits

and contains the largest reserve of metals in Western Europe.

The massive sulfide deposits are hosted in Late Devonian to

Early Carboniferous felsic volcanic and sedimentary rocks.

Rare earth element distributions were determined in

representative samples of volcanic rocks from five westtrending sub-belts of the Portuguese Pyrite Belt to test the

usefulness of rare earth element distributions to correlate

volcanic events, and to examine if their mobility has any

application as hydrothermal tracers. Rare earth element distributions in felsic volcanic rocks show decreases in the relative abundances of heavy rare earth elements and an

increase in La/Yb ratios from south to north in the Portuguese Pyrite Belt. Basalt in one of the sub-belts shows relative enrichment in light rare earth elements with respect to

the other sub-belts. More rare earth element analyses are

needed to provide definitive data that may be used in the correlation of volcanic events. Variations in the distribution of

rare earth elements in felsic volcanic rocks in the NevesCorvo area reflect type and intensity of alteration. Altered

felsic volcanic rocks that host massive sulfide deposits contain pronounced negative europium anomalies. These data

may be useful geochemical indicators in the selection of targets for buried massive sulfide deposits.

Anomalous amounts of gold are distributed in and near

massive and disseminated sulfide deposits in the Portuguese

Pyrite Belt. Gold is closely associated with copper in the

middle and lower parts of the deposits. In the exhalative sedimentary rocks that are stratigraphically above massive sulfide deposits, weakly anomalous concentrations of gold were

detected in a distal manganiferous facies and anomalously

low concentrations of gold were detected in the barite-rich,

proximal-facies exhalites. In contrast, two samples collected

from the proximal facies pyritiferous cherts at São Domingos in the northeastern part of the Portuguese Pyrite Belt,

contained high concentrations of gold; here, Ag, As, Bi, Mo,

Pb, and Sb, are associated with gold.

Altered and pyritic felsic volcanic rocks locally contain

highly anomalous concentrations of gold, suggesting that the

potential for gold in disseminated sulfide deposits and the

nonore-bearing parts of massive sulfide deposits should be

evaluated. The São Domingos, Chança, and Salgadinho sulfide deposits, and adjacent rocks are particularly favorable

areas for gold exploration; arsenic and molybdenum are

commonly associated with the gold. Additional pathfinder

elements include silver, copper, antimony, and lead. The felsic volcanic rocks of the Portuguese Pyrite Belt are hydrothermally altered. Sericite occurs as an alteration product

over large areas and is locally associated with gold. Most

samples, however, contain very low concentrations of gold.

Anomalous gold was detected primarily in highly silicified

and pyritized rock samples. Silicified and pyritized rocks

should routinely be tested for gold, particularly where they

are highly fractured and where they overlie or are lateral to

disseminated or massive sulfide deposits.

Serpentinite and altered serpentinite (listwaenite) rock

samples from the Ossa-Morena zone adjacent to the Iberian

Pyrite Belt were tested for gold and were found to contain

below average abundances; extensive quartz veins that are

characteristic of gold deposits in some ultramafic rock terranes appear to be lacking.
2 RARE EARTH ELEMENTS AND GOLD DISTRIBUTIONS IN THE PORTUGESE PYRITE BELT

INTRODUCTION

Geologic and geochemical studies in the Portuguese

part of the Iberian Pyrite Belt were conducted during a cooperative program funded by the Luso American Development

Foundation (LADF). Supplemental funding was provided

by the Serviços Geológicos de Portugal and by the U.S. Geological Survey. The project was initiated in November 1986

and field work was conducted in the summers of 1987 and

1988. Samples were analyzed in the laboratories of the

USGS in Denver, Colorado.

The Iberian Pyrite Belt (IPB) covers an area about 230

km long and 30 km wide (fig. 1). The IPB is the largest metallogenic province in Western Europe and a major producer

of iron pyrite, copper, and zinc. Approximately half of the

IPB is in southern Portugal and in this paper is referred to as

the Portuguese Pyrite Belt (PPB) (fig. 2). The Neves-Corvo

deposit in Portugal contains large reserves of tin and is the

largest source of tin in Western Europe. All of the deposits

in the PPB are classified as volcanogenic massive sulfide

deposits and are hosted by submarine felsic volcanic rocks of

Late Paleozoic age.

The purpose of the present cooperative studies are to

develop of methods applicable to the exploration for additional metallic mineral deposits in the metallogenic province. The objectives of the program, as stated in 1987, are as

follows: (1) Through the study of the rare earth element

(REE) distributions in volcanic and volcanic-sedimentary

lithostratigraphic units of the Portuguese Pyrite Belt, contribute to a better understanding of ore-forming processes

and of post-mineral modifications in the massive sulfide

environment. Results of the current study are reported in

chapter A. (2) Using the above information, the results of

detailed stratigraphic studies of the volcanic and volcanicsedimentary rocks, and the results of geochemical exploration investigations, develop effective exploration methods

applicable to the PPB and similar geologic terranes. Results

are reported in Grimes and Carvalho (1995). (3) Determine

the lithostratigraphic and geochemical controls on the distribution of gold in the PPB. Results of the current study are

reported in chapter B.

INVESTIGATIVE METHODS AND 

CONSIDERATIONS

Geologic and geochemical investigations were conducted over widely scattered localities in the PPB. Previous

studies in the PPB provided the background for the current

studies. Those that were particularly applicable include

investigations by Carvalho, (1974, 1976, 1979, 1991), Leca

and others (1983), Munhá (1983), Oliveira (1983), Plimer

and Carvalho (1982), and Schermerhorn (1970, 1971).

Samples of felsic and mafic volcanic rocks were collected from the five volcanic sub-belts (A-E) shown in figure

2 as part of the REE study. Particular emphasis was placed

on the felsic rocks. In areas where more than one felsic volcanic unit could be identified, samples were collected from

each unit. Samples were also collected from three felsic units

exposed in the underground workings at Neves-Corvo near

the massive sulfide deposits to compare the REE chemistry

of samples from mineralized and altered localities with those

from unmineralized and unaltered localities. These comparisons are useful in determining REE mobility associated with

hydrothermal events in the PPB. As part of the development

of new exploration techniques, samples of rocks, soils,

plants, and ground water were collected at various localities

in the PPB. The results of this study are reported by Grimes

and Carvalho (1995) and will not be discussed here.

In order to determine the lithostratigraphic and

geochemical controls on the distribution of gold, geologic

and geochemical baseline data were collected in the PPB and

in similar geologic environments. Gold in massive sulfide

deposits in other parts of the world is well documented (Huston and Large, 1989). In the IPB, gold has been recovered

from some pyrite and base metal mines and from the nearsurface oxidized parts of massive sulfide deposits.

Attention is primarily focused on geologic subenvironments other than the massive sulfide deposits in this study.

Prior to the present investigations, gold and associated element distributions beyond the limits of the massive sulfide

deposits were poorly known and not recognized as potential

environments for gold. An interim project report on the distribution of gold and associated elements in cherts

(exhalites) was submitted to Luso American Development

Foundation (Serviços Geológicos de Portugal and U.S.Geological Survey, 1988).

Identification of favorable subenvironments for gold

deposits, other than massive sulfide deposits, in the PPB and

in the South Portuguese Zone (the tectonic province that

hosts the PPB) is made on the basis on modern studies of

gold deposits. The geologic subenvironments in the PPB can

be compared with similar geologic terranes or lithostratigraphic provinces in other parts of the world where gold

deposits are found. In the PPB these subenvironments

include chert terranes (exhalites), hangingwall rocks of massive sulfide deposits (São Domingos), and siliceous and tuffaceous volcanic-sedimentary rocks with disseminated

sulfides (Salgadinho).

GEOLOGIC SETTING

The PPB is a part of the IPB that trends westward to

northwestward through southern Portugal. The IPB extends

into Spain and is about 230 km long and ranges from 30 to

50 km wide (fig. 1). The IPB contains numerous volcanogenic massive sulfide deposits and is the largest mining belt

with the largest reserves of metals in Western Europe. Ore

reserves in the IPB are about equally divided between Portugal and Spain.
INTRODUCTION 3

Allustrel

Castro Verde



































 



 

































  



 

   













  





















 

 









 



 





 



S.Domingos

Aracena

S P A I N P O R T U G A L

Colonas

La Zarza

Rio Tinto

Sotre

San Telmo

SEVILLA

Tharsis

O S S A M O R E N A

ZONE

38°00'

8°00'

37°00'

7°00'

NevesCorvo

Almodovar

Castro Marin

HUELVA

FARO

 Monchique

Ourique

Cercal

Grandola

Lousal



Ficaho

Faixa

Sediments (Cenozoic and Mesozoic)

EXPLANATION

Flysch Group

Brejeira Formation (Lower Westphalian to Namurian)

Mira Formation (Namurian)

Mertola Formation (Visean)

Monchique Massif (76 m.y.)

Hercynian granitic rocks

Carrapateira Group (Lower Navurian to Upper Devonian)

Volcanic siliceous complex (Lower Visean to Upper Devonian)

Ferreira-Ficalho Group (mainly Upper Devonian)

Phyllite-Quartzite Group, including Pulo Do Lobo (Upper Devonian and older)

Normal fault

Thrust fault

Mine or prospect

0 30 60 KILOMETERS

Merlola

Pomordo

The IPB forms the main part of the South Portuguese

Zone (SPZ), a major tectonostratigraphic province in the

Iberian segment of the Hercynian Fold Belt (Lotze, 1945;

Ribeiro and others, 1979). Upper Paleozoic rocks of the SPZ

correlate with those in the Rhenohercynian Zone of the Hercynian Orogeny in southwestern Ireland and southern

England. The SPZ is separated from the Ossa-Morena Zone

(OMZ) to the north by an accretionary margin that is characterized in part by dismembered ophiolite terranes. The OMZ

is composed of polymetamorphic Precambrian basement

and overlying Cambrian to Permian rocks.

The rocks in the PPB are divided into three major

lithostratigraphic units which, from oldest to youngest are as

follows: (1) Phyllite-Quartzite Group (PQ), (2) VolcanicFigure 1. Generalized geologic map of the Iberian Pyrite Belt. Modified from Carvalho (1991).
4 RARE EARTH ELEMENTS AND GOLD DISTRIBUTIONS IN THE PORTUGESE PYRITE BELT

















































 

 

        





  



   

   



        

  

          

 

















Á

Á POMARAO

ALCOUTIM

?

?

?

ÁCHANÇA

Á

Á

S. DOMINGOS

Á

Á

BEJA

PORTUGAL

SPAIN

Á

Á

Á

Á

NEVES

MONCHIQUE

FARO

ODEMIRA

CERCAL

ALJUSTREL

GRANDOLA

B

A

C D

E

Á

OSSA

MORENA

ZONE

Á

EST.

QURIQUE

LOUSAL

CORTE GAFO

ALBERNOA

0 40 80 KILOMETERS 

Post-Hercynian Cover 

Monchique Massif (76 M.Y.) 

Flysch Group

Ferreira-Ficalho Group

Volcanic-siliceous complex and 

 Phyllite-Quartzite Group

EXPLANATION





 

 



Pulo Do Lobo Group

VOLCANIC SUB-BELTS

A Cercal–Odemira

~ Aljustrel (Norte)–Pomarao 

 Albernoa–S. Domingos

E Corte Gafo–Chanca

C

D

?

?

~ B Estacao de Ourique-Neves 

Figure 2. Generalized geologic map of the Portuguese Pyrite Belt showing general trends of 5 volcanic sub-belts. Modified from Carvalho (1991).
ACKNOWLEDGMENTS 5

siliceous Complex (VS), and (3) Culm or Flysch Group. The

oldest unit (PQ) is composed of Devonian shallow marine

phyllite and quartzite rocks that crop out along anticlinal

axes. This unit is overlain by a mafic to felsic bimodal

sequence of volcanic rocks and associated sedimentary rocks

(VS) that were deposited primarily in a submarine setting;

felsic volcanic rocks are dominant and range in composition

from rhyolite to quartz keratophyre. About 20 percent of the

volcanic rocks consist of spilitic pillow basalt. Dacite and

andesite constitute only a minor part of the volcanic

sequence. In addition to the volcanic rocks, the VS unit contains sedimentary rocks primarily at or near the top of the

volcanic sequence; these include chemical sedimentary

rocks (exhalites) composed of green, red, and gray chert, and

bedded barite deposits. The exhalites are commonly intercalated with siliceous tuffaceous beds and vitric tuff. Thin

sequences and lenses of epiclastic rocks are interbedded or

overlie the exhalites. An Early Visean and Namuro-Westphalian diachronous flysch sequence (Flysch Group) overlies the volcanic rocks; this unit was derived from rocks in

the Ossa-Morena Zone and represents the youngest rocks in

the PPB. The stratigraphy of this flysch sequence varies

from one sub-belt to another and the rock types include

shale, graywacke, siltstone, phyllite, and locally conglomerate. A large percentage of the PPB is covered by this thick

and monotonous sedimentary sequence.

The dominantly explosive nature of the volcanism that

formed many of the rocks in the PPB followed by the development of thick overlying flysch sequences indicate largescale subsidence. A southwest to northeast migration of the

main volcanism has been postulated (Carvalho, 1976;

Ribeiro and others, 1979). 

The principal tectonic features of the PPB are imbricate

thrust faults that displace Paleozoic rocks, and tight to open

folds that formed during the Hercynian Orogeny. The earliest deformation resulted from basin subsidence and consisted of synsedimentary faults and slump folds that

represent the beginning of the Hercynian Orogeny in the

SPZ. Synsedimentary deformation evolved into a compressive tectonic regime of intense folding and thrust faulting

resulting in penetrative S1 and, in some cases, S2 cleavages.

The intensity of deformation decreased from northeast to

southwest; folds in the northeast that are tight to isoclinal are

progressively more open to the southwest (Ribeiro and others, 1979; Ribeiro and Silva, 1983). Deformation was

accompanied by low-grade regional metamorphism that

ranges from zeolite facies in the south to lower greenschist

facies in the northeast (Schermerhorn, 1975; Munhá, 1979);

much of the PPB is in the prehnite-pumpellyite (lower greenschist) metamorphic facies.

The general lithologic, stratigraphic, and tectonic features of the SPZ suggest that it represents an active convergent margin along which bimodal volcanic rocks were

erupted during intermittent extensional regimes in a volcanic

arc setting. 

Small to very large polymetallic sulfide ore bodies

throughout the PPB are hosted by felsic volcanic rocks of

largely pyroclastic origin that were deposited during Late

Devonian time. Original sulfide ore deposition is estimated

at more than 1.5 billion tons (Carvalho, 1991). Of this

amount, 20 percent has been mined, and 10 to 15 percent

may have been lost as a result of erosion. Current resources

and reserves of more than 900 million tons are about equally

divided between the Portuguese and Spanish parts of the

IPB.

Mining for copper and precious metals in the IPB began

more than 3,000 years ago, and copper, zinc, tin, iron, sulfur,

and associated gold and silver presently are mined. The largest and highest grade polymetallic deposits are those at

Neves-Corvo (Carvalho, 1991). In addition to the polymetallic sulfides, the PPB contains minable manganese and barite. 

ACKNOWLEDGMENTS

This project was funded principally by the Luso American Development Foundation which we gratefully acknowledge. Other financial support, as well as technical and

logistical assistance, was provided by the U.S. Geological

Survey, the Direcção Geral de Geologia e Minas, and its

agencies, the Serviços Geológicos de Portugal (SGP), and

the Serviço de Fomento Mineiro (SFM).

Delfim de Carvalho, Director of the SGP, was the

project coordinator and provided guidance in the field to the

USGS scientists assigned to the project. Jose Oliveira of the

SGP and Vitor Oliveira of the SFM also provided invaluable

support. We wish to thank the many staff members in the

offices of the SGP in Lisbon and the SFM in Beja for logistical assistance, hospitality, technical advice, and access to

numerous reports. Drafting support was provided by the

offices of the SGP in Lisbon. Paulo Castro, SGP, conducted

field investigations in the Mombeja area as part of this

project.

The cooperation of the companies, Somincor and Pirites Alentejanas greatly contributed to the success of the

project. We particularly acknowledge the contributions by

David Richards and Pedro Carvalho, of Somincor, and Jose

Leitão, of Pirites Alentejanas.
6 RARE EARTH ELEMENTS AND GOLD DISTRIBUTIONS IN THE PORTUGESE PYRITE BELT

INTRODUCTION

Rare earth elements (REE) were determined for samples of volcanic rocks collected in the Portuguese Pyrite Belt

during the present studies in order to (1) evaluate REE as a

tool for correlating volcanic events, and (2) determine the

mobility of REE and assess their use as hydrothermal tracers.

The host rocks of the massive sulfide deposits in the PPB are

felsic volcanic rocks. Because these rocks are widespread in

the PPB, knowledge of the geochemical signatures of the

most favorable massive sulfide deposit hosts may directly

and indirectly help in the process of selecting or prioritizing

exploration targets.

Distribution of mobile REE elements in volcanic rocks

can be correlated with the degree of alteration in geologic

terranes favorable for massive sulfide deposits (Campbell

and others, 1984; Graf, 1977). According to Graf (1977), the

coherent and somewhat predictable geochemical properties

of REE can be used as tracers to identify alteration reactions

in massive sulfide systems. Studies of REE in massive sulfide terranes in eastern Canada have determined a specific

reaction sequence (Graf, 1977); these studies provide a better understanding of the genesis of massive sulfide deposits

in volcanic rocks of the region. Campbell and others (1984)

suggest that the degree of REE mobility may increase with

the size of a deposit. If this proves to be true, it would impact

the exploration efforts for massive sulfide deposits in the

Portuguese Pyrite Belt.

Forty samples were collected from five sub-belts in the

PPB and were analyzed for REE (table 1). Each sample was

analyzed for elements using an instrumental neutron activation analysis (INAA) method described by Baedecker and

McKown (1987) at the U.S. Geological Survey in Denver,

Colo. Results of 4 basalt and 19 rhyolite samples were plotted to determine possible REE mobilization trends that might

serve as geochemical tracers in the exploration for massive

sulfide deposits.

 1U.S. Geological Survey 2Serviços Geológicos de Portugal

CHAPTER A

RARE EARTH ELEMENT DISTRIBUTION IN THE VOLCANIC 

LITHOSTRATIGRAPHIC UNITS OF THE PORTUGUESE 

PYRITE BELT

By David J. Grimes1, Robert L. Earhart1, and Delfim de Carvalho2

A geochemical method to distinguish among volcanic events (lithologic units representative of particular volcanic events) may be a useful exploration tool in the

common cases where the more important ore deposits are

the products of particular volcanic events. The felsic volcanic rocks in the PPB were originally deposited on the

sea floor. The resulting REE pattern is a mixture of REE

from magmatic sources and REE from the sea water. In

multiple volcanic events, such as those represented in the

PPB, the degree of variation from one event to another

may be reflected in physical or chemical differences; theoretically, each sequence of rocks may have a unique REE

signature.

To test this hypothesis, samples of altered and unaltered volcanic rocks from all of the sub-belts of the PPB

were collected and analyzed for REE. Sample descriptions

are given in table 1 and the locations of the sub-belts are

shown on figure 2. 

GEOLOGIC CONSIDERATIONS

According to Carvalho (1972, 1976), the sub-belts of

the PPB represent a migration of volcanism associated with

collisional processes from south to north during the Hercynian Orogeny, near the end of Paleozoic time. Oliveira

(1990), on the other hand, has argued that the volcanic subbelts developed from north to south. Another interpretation

is that some sub-belts may be equivalent in age and the

present configuration is the result of structural separation.

In each of the sub-belts, quartz keratophyre is the dominant volcanic rock, and minor amounts of andesite and

spilitic basalt are present. Data collected as part of the

present study suggest that REE contents show a pattern of

depletion from south to north that may be related to the

development of the sub-belts. For example, chondrite-normalized data for both light rare earth elements (LREE) and

heavy rare earth elements (HREE) in quartz keratophyre

show a pattern of depletion from south to north NevesCorvo to São Domingos (fig. 3B); the trend of LREE in

8 RARE EARTH ELEMENTS AND GOLD DISTRIBUTIONS IN THE PORTUGESE PYRITE BELT

Á Á Á Á Á Á

Á Á Á

Á

1000

100

10

1

La Ce Nd Sm Eu Gd Tb Dy Yb Lu

REE/CHONDRITE

ALTERED RHYOLITES, CERCAL AREA

Á A P7SL13 P7CE1

1000

100

10

1

La Ce Nd Sm Eu Gd Tb Dy Yb Lu

REE/CHONDRITE

SUB-BELT BASALTS

Á

Á Á

Á Á

Á Á

Á Á

Á Á

Á Á ÁÁ

Á

Á Á Á

Á

Á Á

B

C

D

C B, C, D, and E refer to sub-belts shown on figure 2

£

Á

1000

100

10

1

La Ce Nd Sm Eu Gd Tb Dy Yb Lu

REE/CHONDRITE

NEVES-CORVO RHYOLITES

Á

£

£

Á £

Á Á

£Á

Á £ £ £

Á Á Á £ £

D Á P7NC3 P7NC4 £P7NC5

Á Á Á

1000

100

10

1

La Ce Nd Sm Eu Gd Tb Dy Yb Lu

REE/CHONDRITE

SUB-BELT RHYOLITES

Á Á

Á

Á Á

Á

ÁÁ

Á

Á Á

Á

Á

Á

Á

Á Á

Á ÁÁ Á Á Á

Á Á Á Á Á

B

D

C

E

B B, C, D, and E refer to sub-belts shown on figure 2

Figure 3 (above and facing page). Chondrite normalized distributions of rare earth elements in volcanic rocks in the Portuguese 

Pyrite Belt. A, altered Cercal rhyolites; B, rhyolites from sub-belts B, C, D, and E shown on fig. 2; C, basalts from sub-belts B, C, 

and D shown on fig. 2; D, Neves-Corvo rhyolites, and E, basalts and rhyolites.
RARE EARTH ELEMENT GEOCHEMISTRY 9

Á Á

1000

100

10

1

La Ce Nd Sm Eu Gd Tb Dy Yb Lu

REE/CHONDRITE

 BASALTS AND RHYOLITES

Á Á

Á

Á Á

Á Á Á

E ÁBasalts Phyolites

spilitic basalt is the same (fig. 3C). Quartz keratophyres collected from Juliana near Aljustrel in the north to Casavel

near Est. Ourique in the south also show a depletion trend

from south to north in both LREE and HREE (figs. 2, 3B).

Volcanogenic sulfide occurrences were identified in all

five sub-belts; the composition and character of the occurrences, however, varies from deposit to deposit and from

sub-belt to sub-belt. The deposits with the highest grade ore

occur in the Albernoa-São Domingos sub-belt and the Estaço

de Ourique-Neves sub-belt. The deposits with the richest

massive sulfide ore are the Neves-Corvo deposits in the

southern Estação de Ourique-Neves sub-belt (Carvalho,

1991). 

RARE EARTH ELEMENT 

GEOCHEMISTRY

ALTERED RHYOLITES, CERCAL AREA

For the purpose of this discussion the term “rhyolite” is

used to describe siliceous volcanic rocks whose probable

average composition approximates that of quartz keratophyre. Two samples of altered rhyolite (nos. P7SL13,

P7CE1) from the Cercal area in the western part of the PPB

were analyzed for REE and the chondrite-normalized plots

are shown in figure 3A. Both samples have a high percentage of silica (77.7 percent) quartz keratophyres and are from

the upper part of the silicic volcanic sequence near the contact with overlying volcanic-sedimentary rocks of the upper

part of the Volcanic-Siliceous Complex. The stratigraphic

relationship of the two samples is uncertain; however, they

may represent a single volcanic event. Sample no. P7SL13,

from the São Luis quarry, is potassically altered, whereas

sample P7CE1, from a road cut near the quarry, is intensely

sericitically altered. Generally rocks classified as potassically altered are characterized by abundant veinlets of

coarse, pink potassium feldspar and those sericitically

altered contain abundant sericite throughout the rock. The

distribution of REE in the two samples is significantly

different; if the two samples represent a single volcanic

event, the difference the REE plots suggests that the mobility

of REE is related to alteration. 

The REE pattern of the sericitically altered sample no.

P7CE1 is similar to the average chondrite-normalized REE

pattern for PPB rhyolites; the LREE are enriched, europium

is depleted, and the La/Yb ratio is 5.93 (table 2, fig. 3A).

However, the overall REE abundances are lower than the

average rhyolite in the PPB and the Eu/Sm ratio is 0.06,

lower than the average 0.11. In sample no. P7SL13, LREE

are depleted and HREE are relatively enriched as compared

to REE in sample no. P7CE1. In contrast, sample no.

P7SL13 has a La/Yb ratio of 0.75 and Eu/Sm ratio of 0.05.

Similar REE trends in alteration zones associated with a

Canadian massive sulfide deposit were identified by Campbell and others (1984); there was an overall depletion of

REE, a marked increase in the europium negative anomaly,

and the HREE were enriched.

SUB-BELT RHYOLITES

Chondrite-normalized REE determinations of 12 relatively unaltered rhyolite samples from sub-belts B, C, D, and

E were plotted using the data shown in table 3 and the distribution patterns indicate high REE abundances (fig. 3B). In

addition, the LREE are relatively enriched as compared with

the HREE, and europium shows a negative anomaly. The

enrichment of REE is relatively greater in sub-belt B suggesting that these rhyolites are the “most evolved” of any

sub-belt, and the relative depletion of REE in sub-belt E suggests that these rhyolites are the most primitive. Additional

evidence suggesting sub-belt B rhyolites are a later stage of

magmatic evolvement include the existence of elements



RARE EARTH ELEMENT GEOCHEMISTRY 13

throughout the PPB need to be analyzed before such a conclusion could be confirmed.

CONCLUSIONS AND RECOMMENDATIONS

Rare earth element distributions in sub-belt rhyolite

and basalt samples show relative enrichment from north to

south in the PPB which may be the result of fractional crystallization of the parent magma or the result of contamination by partial melting of upper crustal rocks. If the REE

enrichment is related to fractional crystallization, and the

development of sub-belt volcanic rocks can be proven to

have progressed from north to south, the usefulness of REE

distributions as a tool for correlating and distinguishing volcanic events will be demonstrated. However, additional

REE data are needed to confirm this hypothesis of development in the PPB.

Variations in the distribution of REE in altered felsic

volcanic rocks in the Cercal and Neves-Corvo areas seem to

reflect the degree of rock alteration. A sample of potassically

altered rhyolite from a quarry near Cercal contained REE

abundances that were significantly different from lessaltered rhyolite samples collected nearby. In addition, the

REE chondrite-normalized plot of an intense sericitically

altered rhyolite sample collected from the top of the volcanic

pile and closely associated with the massive sulfide deposits

at Neves-Corvo, had depleted REE abundances as compared

to plots of similar samples collected from a lower part of the

volcanic pile from different localities. If these differences

prove to be related to an increase in the mobility of REE as a

result of hydrothermal alteration, REE will be shown as useful hydrothermal tracers or as geochemical indicators of

favorable host rocks for massive sulfide deposits. Additional

work is needed to confirm these findings.
14 RARE EARTH ELEMENTS AND GOLD DISTRIBUTIONS IN THE PORTUGESE PYRITE BELT

deposits are spatially or genetically associated with rocks in

massive sulfide terranes include the Timmins district, Canada, the Kuroko deposits, Japan (Sato, 1966), and the Tasmanian deposits in Australia (Huston and Large, 1989). 

Gold deposits that occur in ultramafic rocks are not necessarily genetically associated with massive sulfide deposition, but are frequently associated with the tectonic belts

along continental margins that contain massive sulfides in

rocks of magmatic arc derivation. Some well known examples of ultramafic rocks forming in extensional structures

along the accreted margin of colliding oceanic and continental plates include the Larder Lake Break in eastern Canada

and the Melones Fault, California.

In tectonic belts along accreted margins resulting from

the collision of oceanic and continental plates, such as the

margin between the South Portuguese Zone and the OssaMorena, a tripartite spatial association of gold deposits, massive sulfides, and ultramafic rocks may be present. A well

documented example is where the gold deposits and ultramafic rocks of the California mother lode are generally adjacent

(landward) to the California zinc-copper massive sulfide belt

in the foothills of the Sierra Nevada.

Exhalite deposits which are related to the waning stages

of volcanism are deposited in island arc (and possibly fore

arc) settings. Rocks of exhalative origin are important hosts

of gold deposits. Some examples of very large exhalitehosted gold deposits include algoma-type iron formations,

including the Homestake deposit, South Dakota; baritic and

siliceous exhalites, including the Hemlo deposit, Canada;

and baritic and siliceous exhalites of Tasmania, Australia.

The occurrence of gold and silver in the massive sulfide

ores of the IPB is well documented (Strauss and Beck, 1990).

Precious metals were recovered by ancient miners from oxidized parts of massive sulfide bodies, and are common

byproducts of both oxidized and unoxidized ores in modern

mining operations. The current studies are not directed primarily towards the collection of additional geologic and

geochemical data related to the distribution of gold in the

massive sulfide bodies, but are designed to investigate other

subenvironments closely related spatially and, in most cases,

genetically to the massive sulfide deposits. The following

CHAPTER B

GEOLOGIC SETTING AND GEOCHEMICAL CONTROLS ON 

THE DISTRIBUTION OF GOLD IN THE PORTUGUESE PYRITE 

BELT

By Robert L. Earhart1, Delfim de Carvalho2, Vitor Oliveira3, Jose T. Oliveira2, and Paulo Castro2

INTRODUCTION

The geologic setting and distribution of gold and associated elements in the Portuguese Pyrite Belt (PPB) were

studied in order to (1) identify terranes in the PPB that may

be favorable for gold occurrences, and (2) develop a

geochemical deposit type that will be useful in future gold

exploration programs not only in the PPB but in similar geologic terranes worldwide. Exploration for gold deposits in

the PPB was not an objective in these studies.

The development of a deposit model for gold in the PPB

involved geologic reconnaissance mapping using existing

geologic maps and reports. Additional geologic data were

collected during the summers of 1987 and 1988; core from

drill holes were examined and sampled in areas that had been

explored for massive sulfide deposits. Rock outcrop and drill

core samples were collected from areas identified as permissive for gold and associated elements. Lists of analytical data

are included in Appendix A. Samples were analyzed using an

atomic absorption-graphite furnace method in which the

lower limit of detection for gold is 2 parts per billion (ppb)

(Meier, 1980). Other elements commonly associated with

gold were analyzed using an inductively coupled plasma

emission spectrographic method (Motooka and Sutley,

1982). Correlation coefficients of selected elements were

obtained using the computer program Minitab (table 5). For

statistical compilations, analytical results of samples with

qualified values, that is, not detected at the lower limit of

determination (N), and detected, but below limit of determination (L), are assigned a value at the lower limit of detection. 

In many parts of the world, geologic environments similar to those in and near the PPB contain gold in massive sulfide deposits and spatially associated volcanic, chemical

sedimentary (exhalites), and in ultramafic rocks that range

from Archean to Tertiary in age. Mining areas where gold

 1U.S. Geological Survey 2Serviços Geológicos de Portugal

3Serviços de Formento Mineiro
INTRODUCTION 15

Au

Au

Ag

Ag

As

As

Cu

Cu

Pb

Pb

Zn

Zn

Ba

Ba

-------

-

-

-

-

-

-

0.322 0.307 0.623 0.602 -0.084

0.357 0.585 0.389 0.618

0.201 0.254 0.120

-0.040

0.630 0.145

Proximal exhalites

Au

Au

Ag

Ag

As

As

Cu

Cu

Pb

Pb

Zn

Zn

Ba

Ba

Sb

Sb

Mn

Mn

-

- --

-

-

-

-

-

-

-

0.364

0.010 -0.292

-0.186

-0.256 0.662

-0.032 -0.111 -0.190 -0.186

0.187 0.514 -0.081 -0.100 0.459 -0.193

-0.183 0.196 0.783 -0.078 0.010

-0.045 0.313 -0.292

0.512 -0.090 -0.125 -0.256

-0.142 0.290

0.662

Distal exhalites

Au

Au

Ag

Ag

As

As

Cu

Cu

Pb

Pb

Zn

Zn

Mo

Mo

Bi

Bi

Sb

Sb

-

-

-

-

-

-

-

-

-

0.568

0.126 0.609 0.005

0.387

0.645 0.665 0.382

-0.188 -0.044 0.515 0.301

0.459 -0.039 0.484 -0.020 0.418

-0.057 0.791

0.168

-0.026

0.199 -0.037 0.467 0.249 0.116

0.166 0.359 -0.035

0.472 0.213 0.693 0.069

0.213 -0.099

0.315

All rocks, Chança area

Au

Au

Ag

Ag

As

As

Cu

Cu

Pb

Pb

Zn

Zn

Mo

Mo

Bi

Bi

Sb

Sb

-

-

-

-

-

-

-

-

-

0.780 0.095 0.713

0.107 0.208 -0.037 0.868 -0.219

-0.027

0.024 -0.055

-0.097 -0.161 -0.055 -0.061

0.211 0.458 -0.004 -0.269 -0.039 -0.080

-0.036 0.242 -0.279 -0.068 -0.084

-0.135 -0.059 0.101

0.140 0.435 -0.038 0.923

0.300 0.563

0.067

Felsic volcanic rocks, Salgadinho area

Au

Au

Ag

Ag

As

As

Cu

Cu

Pb

Pb

Zn

Zn

Bi

Bi

Sb

Sb

-

-

-

-

-

-

-

-

0.036 0.041

0.956 0.983 0.044

-0.028 -0.043

-0.010 0.932 0.293

0.028 -0.036 -0.092

-0.00 0.009 -0.159 -0.039 0.004

0.305 0.094 0.936 0.884

-0.048 -0.137

0.826 0.232 0.148

0.925

Veins and breccias, Salgadinho area

Au

Au

Ag

Ag

As

As

Cu

Cu

Pb

Pb

Zn

Zn

Bi

Bi

-

-

-

-

-

-

-

0.020 0.393 0.386 0.159 0.896

0.436 0.092 0.169 0.318 0.197 0.446

0.052 0.537 0.064 -0.003

0.214 0.079 0.564

 0.267

0.755 0.587

Sedimentary rocks, Salgadinho area

Table 5. —Correlation coefficients, rock samples in Portuguese Pyrite Belt.
16 RARE EARTH ELEMENTS AND GOLD DISTRIBUTIONS IN THE PORTUGESE PYRITE BELT

Au

Au

Ag

Ag

As

As

Cu

Cu

Pb

Pb

Zn

Zn

Mo

Mo

Bi

Bi

Sb

Sb

-

-

-

-

-

-

-

-

-

-0.002

0.574 -0.145 -0.053

0.039

0.306 -0.053 0.989 0.568

0.039 0.409 -0.114 0.153 -0.063 0.974

0.799 -0.285 0.348 0.065 -0.020 0.407

-0.608 -0.172 0.253 0.011 -0.042

-0.075 -0.188 0.101

-0.168 0.562 -0.054 -0.050

-0.068 -0.068

-0.048

Felsic volcanic rocks, Mina de Sao Domingos

Au

Au

Ag

Ag

As

As

Cu

Cu

Pb

Pb

Zn

Zn

Bi

Bi

Ba

Ba

Sb

Sb

Mo

Mo

Mn

Mn

- 0.992

-

-

-

-

-

-

-

-

-

-

0.556 -0.082

-0.074 -0.120

0.794

0.710 0.998 0.979 0.780 0.386

-0.133 0.998 0.997 0.854 -0.152

-0.133

0.402 0.243 0.709 0.528 0.588 0.694 0.410 -0.250

-0.070 0.689 -0.078 -0.087 -0.104 -0.147 0.481

-0.127 -0.139 -0.161 0.415 0.235

-0.140 0.754 0.840 0.994 -0.213 0.582

0.990 0.819 -0.143 0.411

-0.163 0.462

-0.202 0.559

-0.178

0.892

0.435

Exhalites, Mina de Sao Domingos

Au

Au

Ag

Ag

As

As

Cu

Cu

Pb

Pb

Zn

Zn

Ba

Ba

Bi

Bi

Mo

Mo

-

-

-

-

-

-

-

-

-

-0.093

0.515 -0.147 -0.063

0.102

-0.056 0.059 0.063 0.882

-0.078 -0.056 0.132 -0.093 -0.052 0.075

0.452 -0.050 0.119 -0.071 -0.060 0.053

-0.114 0.158 0.508 -0.020 -0.235

-0.165 -0.150 -0.141

-0.108 -0.076 -0.024 0.901

-0.071 -0.103

-0.098

Epiclastic rocks, Mina de Sao Domingos

Au

Au

Ag

Ag

As

As

Cu

Cu

Pb

Pb

Zn

Zn

Sb

Sb

- -

- -----

-

-

-

-

-

0.324 -0.066 0.016 -0.160 0.377

-0.033 -0.178 0.206 0.945

-0.061 -0.109 -0.038

-0.130

0.009 0.221

Mafic volcanic rocks, Mina de Sao Domingos

Au

Au

Ag

Ag

As

As

Cu

Cu

Pb

Pb

Zn

Zn

Mo

Mo

-

-

-

-

-

-

-

-0.058

0.033 0.205 0.173 0.065

-0.032 0.079 -0.045 0.062

0.872 0.222 0.001

-0.249

0.402 -0.089

All rocks, Serra Branca

-0.075 -0.073 -0.088 -0.199

-0.099 -0.058

Cr

Cr

Ni

Ni

Co

Co

Cu

Cu

Zn

Zn

-

-

-

-

-

0.211 0.202 0.417 -0.007

-0.010 0.696

0.087

Serpentinites, Mombeja

0.866 -0.173 0.087

Cr

Cr

Ni

Ni

Co

Co

Cu

Cu

Zn

Zn

-

-

-

-

-

0.503 0.386 -0.159 -0.001

0.145 -0.153

0.013

Listwaenites, Mombeja

0.888 -0.059 -0.312

Table 5. —Correlation coefficients, rock samples in Portuguese Pyrite Belt—Continued.

~ ~

~ ~
GOLD IN MASSIVE AND DISSEMINATED SULFIDE DEPOSITS 17

summary of recent research on the occurrence of gold in

massive sulfide deposits presents the possible genetic and

spatial interrelationships of gold ores in volcanogenic

settings.

GOLD IN MASSIVE AND 

DISSEMINATED SULFIDE DEPOSITS

GOLD IN MASSIVE SULFIDE DEPOSITS

Gold is commonly recovered as a byproduct in massive

sulfide mining operations throughout the world. Gold is the

principal ore mined from massive sulfide deposits in some

localities; one example is the Mt. Morgan deposit, a late

Paleozoic massive sulfide deposit in Queensland, Australia.

Mt. Morgan, the largest known gold deposit in Australia,

contained 67 million tons of massive sulfide ore, averaging

4.87 g/t gold and 0.7 percent copper (Frets and Balde, 1975)

is now mined out. The Horne and Quemont deposits in the

Noranda district of Quebec, Canada, also contain large

reserves of gold averaging 4.5 g/t (Franklin and others,

1981).

Two distinct types of gold occurrences were recognized

by Huston and Large (1989) in massive sulfide deposits in

Australia and eastern Canada: (1) gold-zinc-lead-silver

association in the zinc-rich upper parts of massive sulfide

deposits, and (2) gold-copper association in the lower parts

of massive sulfide bodies and in the upper part of the underlying stringer ore. In any single deposit, the gold commonly

occurs in one of the settings to the exclusion of the other. In

the upper zinc-rich zone, gold is transported in bi-sulfide

complexes and gold precipitation is promoted by near neutral, oxidized and low temperature fluids (150°C-275°C);

barite-carbonate gangue is present. In the lower zone, gold

is transported as chloride complexes at temperatures ranging

from 275°C to 350°C. Both the type of gold occurrence and

the grade of the ore are controlled by temperature, pH, and

the oxygen fugacity of the ore-forming fluids. Empirical data

suggest that if gold is present in anomalous concentrations in

the copper-rich lower part of a deposit, it will likely be deficient in both the barite-bearing, zinc-rich upper part of the

deposit and in the massive to richly disseminated exhalative

barite deposits that commonly overlie the massive sulfide

deposit. Conversely, if anomalous concentrations of gold

are present in the overlying barite-bearing rocks, the lower

copper-rich rocks are relatively deficient in gold.

A simplistic diagrammatic model showing gold associations in massive sulfide deposits and adjacent subenvironments of the PPB is shown in figure 4. In and adjacent to the

SPZ, the following types of deposits are representative of the

subenvironments that may be favorable for the discovery of

gold: (1) massive sulfide deposits, (2) disseminated sulfide

deposits (referred to locally as “safrão” deposits), (3)

chemical sedimentary rocks (exhalites), (4) silicic- and sericitic-altered felsic volcanic rocks, and (5) altered ultramafic

rocks (fig. 4). Analytical results of rock samples in or

closely related to the massive and disseminated sulfide

deposits in the PPB that were investigated during the present

studies indicate that gold is more closely associated with the

copper-rich rather than with the zinc-rich ores (table 5).

Gold in the barite-rich rocks of the IPB is rarely, if ever,

present above the lower limit of detection (2 ppb). In contrast, gold ore in the Rosebery deposit, Tasmania, Australia,

occurs in both the zinc-rich upper part of the massive sulfide

body and in the overlying exhalative massive barite (Huston

and Large, 1989); an area near the Black Sea in Turkey is

currently being studied by the Geological Survey of Turkey

and the gold distribution is similar to that in Tasmania. The

occurrence and distribution of gold in exhalite-facies rocks

are discussed in greater detail in a following section of this

chapter.

GOLD IN DISSEMINATED SULFIDE 

DEPOSITS

The following two types of disseminated sulfide deposits were investigated in the Portuguese Pyrite Belt: (1) disseminated sulfide deposits in a proximal volcanic setting,

such as the sulfide occurrence at Chança on the border

between Portugal and Spain (figs. 2, 5), and (2) disseminated

sulfides in a distal volcanic setting, such as the sulfide occurrence at Salgadinho in the western part of the PPB (figs. 2,

6). The two settings have distinctly different volcanic and

sedimentary stratigraphy, as well as, different positions relative to known volcanic centers.

CHANÇA AREA

The disseminated sulfide occurrence at Chança is characterized by a relatively thick sequence of felsic pyroclastic

rocks including abundant coarse fragments that represent

proximal deposits of highly explosive volcanism (fig. 5).

The felsic volcanic sequence includes pyritic rhyolitic or

quartz keratophyric breccia. Epiclastic rocks are rare in the

volcanic sequence, but locally tuffite and black shale overlie

the volcanic rocks in the upper part of the Volcanic-Siliceous

(VS) Complex. These rocks are, in turn, overlain by

graywacke and shale that comprise the Flysch Group (fig. 5).

Volcanic rocks of the VS Complex are locally present in

folded and faulted rocks in the upper plate of a northwesttrending thrust fault. The area also contains subvolcanic rhyolitic intrusive rocks and diabase dikes. Felsic volcanic

rocks near the leading edge of the thrust commonly contain

richly disseminated sulfide minerals and form a large gossan

both in Portugal and Spain in the vicinity of the Chança

River. The disseminated sulfides, which consist mostly of
18 RARE EARTH ELEMENTS AND GOLD DISTRIBUTIONS IN THE PORTUGESE PYRITE BELT

















 























Ocean

Oceanic crust

Portugese Pyrite Belt

Rift with bi-modal 

volcanism

Back arc basin

Back arc 

thrust belt

Continental crust

Oceanic crust

Distal Au

deposit Exhalite

 Zn-rich 

rocks + Au 

Proximal

Au deposit Exhalite

Distal Au

deposit

 Cu-rich 

rocks + Au 

 Massive sulfide

deposit Epiclastic rocks

 Cu + Au in disseminated

sulfide deposit 

Silicic- and sericitically altered

Felsic volcanic rocks

Mafic volcanic rocks

Listwaenite

Listwaenite

Serpentinite

A B

Ultramafic Rocks



Felsic

magma



pyrite with minor amounts of chalcopyrite, sphalerite, and

galena, occur in highly siliceous felsic volcanic rocks in

which quartz phenocrysts are commonly preserved. Commonly, the disseminated zone consists of less than 10 percent

sulfide minerals; rarely it is known to be as much as 70 percent of the rocks over narrow intervals. The effects of

sericitic and chloritic alteration are common in the

disseminated sulfide zones. Locally, quartz-sulfide stringer

zones are preserved in the more highly chloritic and agglomeratic footwall rocks.

During 1987 and 1988, a total of 62 samples, 31 drill

core and 31 outcrop, were collected from the Chança area.

The sample localities are shown on figure 5. The samples

were primarily silicified, sericitized, and chloritized felsic

volcanic rocks.

Anomalous concentrations of gold, as high as 200 ppb,

were found in samples of pyrite-rich (as much as 70 percent)

and highly siliceous felsic tuff that contained minor amounts

of chalcopyrite. Samples with the highest concentrations of

gold were collected from the stratigraphically lower part of

the stratabound disseminated sulfides and from the upper

part of the underlying stringer zone in the footwall. Samples

from the Chança area are similar to samples collected from

similar deposit types worldwide in that the gold is associated

with arsenic, antimony, and copper and there is very little or

no zinc (table 5). 

Early precipitation of copper during fluid mixing in the

plume above the sea floor at high temperatures was explained

by Sato (1973) who developed a thermodynamic model

based on metal chloride solubilities. In this model, zinc and

lead precipitate at lower temperatures. The presence of

anomalously high gold in the copper-rich lower parts of the

disseminated sulfide body and in the footwall stringer zone

at Chança suggests that the gold was precipitated from a

chloride complex at temperatures between 275°C and 350°C

(Huston and Large, 1989). The geochemical data from the

Chança area samples suggest that gold precipitation temperatures were toward the low end of this range. Precipitation

of gold in the Chança area was probably triggered by a combination of increasing pH, decreasing oxygen fugacity, and

decreasing temperature during the formation of the disseminated sulfides. Geochemical indicators of zones most favorable for gold deposits include Ag, As, Bi, Cu, Mo, Pb, and Sb

(table 5) and our studies suggest that the most prospective

parts of disseminated sulfide occurrences are copper-rich

lower parts.

SALGADINHO AREA

The disseminated sulfide occurrence at Salgadinho (fig.

6) in the western part of the PPB and in the southernmost volcanic sub-belt was deposited in a distal volcanic setting. This

Figure 4. Schematic cross section across the South Portuguese Zone showing tectonic setting and theoretical gold occurrences. Enlarged

sections of schematic cross sections of A, Portuguese Pyrite Belt and B, Mobile Belt. Back arc rocks in South Portuguese Zone preserved

only in back arc thrust (Mobile Belt).
GOLD IN MASSIVE AND DISSEMINATED SULFIDE DEPOSITS 19

?

?

?

?

?

? ?

?

?

50

15

35

50

40

45

35

35

40 40

40

30

30

40

40

25

40

50

45

45

25

25

40 40

40

40

50

35 55

40

50

45

10

40

?

P7CH12

P7CH11a

P7CH13

P7CH14

P7CH14a

P8CH06

P8CH08

P8CH17

P8CH16

P8CH03

P8CH04

P8CH10 P8CH09

P8CH05

P8CH07

P7CH2

P7CH3

P7CH1

P7CH1

P7CH5 P7CH6

P7CH9

P8CH4

P8CH14

P8CH20

P8CH11

BH301–BH318

BH3

P8CH19 P8CH18

P8CH12

P8CH13

P7CH8 P8CH15

P8CH02

P8CH01

d

r

c

c

d

c c

c c

r

ft1 ft1

ft1

ft1

ft2

ft2

ft3

tag

ft1

ft1

ft1

c

c

P O R T U G A L

S P A I N

82,500 N

260,500 E 261,500 E

82,000 N

81,500 N

Diabase dike

Intrusive rocks

Culm Group

Volcanic-siliceous complex

Turbidites consisting of shale, siltstone, and quartzite, 

 intercalated felsic pyroclastic rocks 

Felsic tuff, unit 1—Intense to moderate sericitic alteration, 

 weak to moderate iron hydroxide and iron sulfate minerals, 

 interbedded tuffite, shale, and minor chert

Felsic tuff, unit 2—Locally agglomeratic, abundant iron 

 hydroxide and iron sulfate minerals, commonly silicified, 

 forms gossan 

Rhyolite-rhyodacite

EXPLANATION

c

ft1

Extrusive and sedimentary rocks

ft2

0 250 500 METERS

Felsic tuff unit 3—Locally agglomeratic, commonly chloritic, 

 quartz veinlets locally, highly deformed. Limonite and 

 copper carbonate minerals in fractures 

ft3

50

CH101–CH113

CH 1

CH101–CH113

CH 1

Contact—Inferred. Queried where uncertain

Strike and dip of beds

Normal fault—Inferred, bar and ball on 

 downthrown block

Thrust fault—Inferred, bar and ball on 

 downthrown block. Queried where uncertain

Drill hole—Showing number, direction, and 

 sample numbers

Rock sample locality—Showing number

Shaft

Adit

International boundary

Shear zone

Felsic agglomerate and tuff—Highly 

 chloritic, highly deformed, quartz and 

 calcite veinlets with oxidized sulfide 

 minerals, by purple shale of the 

 Borra do Vinho Formation

tag

r

Figure 5. Geologic map of the Chança area showing drill hole and rock sample localities. Modified from Billiton Portuguesa and

Serviços Geológicos de Portugal.
20 RARE EARTH ELEMENTS AND GOLD DISTRIBUTIONS IN THE PORTUGESE PYRITE BELT

0 2 KILOMETERS

P8SL02

P7SL04–P7SL11 P8SL01

84,000 N

86,000 N

88,000 N

90,000 N

152,000 E 154,000 E

Salgadinho 

area

Salgadinho 

Achadinha 

Coxo do Cao 

Areas of 

intensely

altered 

rhyolite

Sao Luis

EXPLANATION

Sao Luis

quarry 

Geodetic point

Paved road

Unpaved road

Town site

P8SL01 Rock sample locality and 

 number

~

deposit is hosted by felsic volcanic rocks largely of pyroclastic origin with abundant interbeds of fine-grained sedimentary rocks. In contrast to the coarse-textured felsic tuff at

Chança, the dominant rock type at Salgadinho is fine-grained

pyroclastic beds. Interbedded with the pyroclastic rocks are

fine-grained and thinly laminated sedimentary phyllite and

tuffite rocks. The felsic volcanic rocks are overlain by the

São Luis Shale, forming the top of the VS Complex in this

area. The São Luis Shale consists of graphitic shale, tuffite,

siliceous shale with local lenses of exhalative cherts in the

lower part (Carvalho, 1976; Plimer and Carvalho, 1982). The

lithologic and textural characteristics of volcanic and

associated rocks confirm the interpretation of a distal setting

of the sulfide deposition. The sulfide deposit and the highly

deformed host rocks are faulted by both high-angle and lowangle faults and three phases of deformation, F1, F2, and F3

are identified in the region (Plimer and Carvalho, 1982). The

most intense phase of deformation is F1, characterized by

tight isoclinal folds.

Plimer and Carvalho (1982) determined four alteration

types and distributions in the Salgadinho area. In order of

decreasing intensity they are (1) green sericite, pyrite, chalcopyrite, quartz, ankerite, and chlorite; (2) green sericite,

pyrite, quartz, and chlorite; (3) green sericite and quartz; and

(4) green sericite. Plimer and Carvalho identified the green

sericite as celadonitic fluoro-muscovite and noted a dramatic

increase in fluorine in the more intensely altered zones. An

additional alteration type, intense silicification, key to understanding the distribution of gold, was recognized during the

present studies.

The Serviço de Fomento Mineiro completed studies in

the Salgadinho area in 1982 but the results have not been

published. The Salgadinho deposit was drilled to determine

the potential for base metals; gold values in individual core

samples of disseminated sulfides were as high as 16 g/t.

Anomalous gold values were widely scattered and occurred

over narrow intervals generally less than 1 m thick. No

attempt was made during the earlier studies to determine

alteration, lithologic, or geochemical controls with respect to

gold distribution.

The present studies, designed to evaluate the distribution of gold with respect to lithologic type, alteration type,

and geochemical associations, re-examined drill cores from

8 holes. A total of 135 samples of altered rock were collected

from the drill core (pl. 1). The 135 samples which consist of

(1) felsic volcanic rocks (46 samples), (2) sedimentary rocks

(63 samples), and (3) veins and breccias (26 samples) were

analyzed for 34 elements. Analytical results of selected elements in these three sample populations are shown in Appendix A and correlation coefficients are given in table 5.

Anomalously high concentrations of gold (as much as 4.8 g/

t) were detected in all three of the lithologic categories (App.

A). Lithologic and alteration data along with drill hole intersections with significant gold and silver enrichment are

shown on plate 1. The samples that contain gold in concentrations of 200 ppb or more occur in the middle and lower

parts of the disseminated sulfide body, with the notable

exception of sample SL0704, collected from sedimentary

rocks in the upper part. Two samples that contain anomalously high gold (SL2609, SL2610), were collected from

quartz-sulfide veins in chlorite-rich footwall rocks. In similar deposits in other parts of the world, arsenopyrite is rarely

associated with sulfide; however, when it is identified, it is

associated with anomalously high concentration of gold

(sample SL2809; App. A). Although most gold-bearing

zones in the IPB contain ankerite and green sericite in the

Figure 6. Sketch map showing location of the São LuisSalgadinho area.
GOLD IN MASSIVE AND DISSEMINATED SULFIDE DEPOSITS 21

alteration mineral assemblages, both minerals are common

in alteration zones that do not contain anomalous gold. Consequently, ankerite and green sericite are not considered to

be indications of potential gold targets in this geologic environment.

Plate 1 shows that gold enrichment in the Salgadinho

deposit is widespread and is most common in strongly

silicified rocks. There are two types of silicification in the

gold-bearing zones: (1) silica flooding, and (2) quartz

veins. Silica flooding is most common in the felsic volcanic unit that makes up a major part of the disseminated sulfide host rocks and it consisted of almost total replacement

of the rock-forming minerals by SiO2. In addition, laminated siliceous tuff, chloritic tuff, lapilli tuff, and phyllite

and tuffite that are interbedded in the volcanic rocks are

locally silica flooded and pyritic, and contain anomalously

high gold. Locally anomalous concentrations of gold in

quartz veins occur as fracture fillings in both the footwall

stringer zone and in fault zones in the disseminated sulfides that are closely associated with fault breccias.

Alteration mineral assemblages and indicator elements

that occur with gold are similar in the various lithologic

types. The elements, however, that occur with gold in veins

and breccias in fault zones in the disseminated sulfides are

distinctly different from those in the other rocks (App. A).

We believe that gold, originally deposited with disseminated

sulfides in the volcanic and sedimentary rocks, may have

been preferentially remobilized during deformation into

veins and breccias in the disseminated sulfide body. Veins

in the footwall stringer zone differ from those in the disseminated sulfide body in that they contain silver-to-gold ratios

of less than 1 as opposed to veins in the disseminated sulfide

fault zones that contain silver-to-gold ratios of greater than

5. The two vein types are of different ages and origins; those

in the footwall are related to disseminated sulfide deposition

while those in the disseminated sulfide zone are related to

post-mineralization faults. There is no consistent pattern in

the fault zone veins between gold and associated elements as

determined by chemical analysis. In the Salgadinho area,

slump and other gravity slide features indicate that the disseminated sulfide body has, in part, been transported by

gravity down the paleoslope. In most places it is detached

from the footwall, and consequently underlain only locally

by feeder or stringer veins.

In the felsic volcanic rocks, gold has a strong positive

geochemical correlation with silver and copper (table 5) and

very low or negative correlation coefficients with antimony

and zinc. Antimony and zinc are commonly found in the

lower temperature minerals formed in upper parts of disseminated or massive sulfide deposits (table 5). 

The geologic and geochemical data collected in the Salgadinho area suggest that gold was introduced during the

earlier, higher temperature phase of disseminated sulfide

deposition and so, by inference, was precipitated from a

chloride complex. When precipitated under these conditions, gold occurs primarily in the lattice of the copper sulfide minerals, to a lesser degree in pyrite or as free gold in

pyrite, and rarely, such as at the Mt. Morgan, Australia, in

telluride minerals (Huston and Large, 1989). Geochemical

associations at Salgadinho, similar to those at Chança, have

anomalously high concentrations of gold occurring in a

greater variety of lithologies. Some gold may have been

remobilized preferentially into dilatant structures such as

fault zones, during post-mineralization tectonic events.

The distribution of gold in a variety of lithologic types

of both volcanic and sedimentary origin suggests an epigenetic origin. Plimer and Carvalho (1982) noted that the disseminated sulfides in the Salgadinho area are hosted by

porphyritic felsic volcanic rocks and, although stratabound,

they are not of exhalative origin. Gold distribution and

geochemical associations determined in our studies would

seem to confirm a pore-filling or replacement origin for the

gold. An epigenetic origin for the sulfides seems probable;

sulfides and gold were deposited very close in time at or near

the sea floor. The copper- and gold-bearing hydrothermal

solutions were probably associated with sea floor hot spring

activity; the solutions permeated the porous underlying felsic tuffaceous volcanic rocks. Sedimentary rocks intercalated in the volcanic rocks commonly have sedimentary flow

structures, indicating a steep paleoslope and penecontemporaneous faulting at the time of their formation. Movement of

the hydrothermal solutions or their precipitates down the

paleoslope could facilitate the concentration of heavy mineral precipitates as suggested by gold concentrations in some

turbidite sequences that are synchronous with nearby sulfide

deposits of volcanogenic origin.

SÃO DOMINGOS AREA

Gold in the São Domingos area occurs in felsic volcanic

rocks in the vicinity of and peripheral to a massive sulfide

deposit as well as in exhalite deposits that overlie the

deposit. The exhalite deposits are discussed in a later section.

Twenty-two felsic volcanic rock samples from the São Domingos area were analyzed for gold and associated elements

(App. A). Of these, three (14 percent) contained anomalous

concentrations of gold that ranged from 100 to 950 ppb Au.

In contrast, 30 andesite and basalt samples contained a maximum concentration of 6 ppb gold and 37 epiclastic rock

samples contained less than 6 ppb gold, although several

showed the effects of weak sericitic alteration (App. A). All

of the anomalous samples were collected within 200 m of the

now mined out massive sulfide deposit. Samples from drill

hole number MP3, located about 2.5 km west of the massive

sulfide body, contain 2 ppb or less gold. The geology and

sample localities are shown on plate 2, map A. 
22 RARE EARTH ELEMENTS AND GOLD DISTRIBUTIONS IN THE PORTUGESE PYRITE BELT

GOLD DISTRIBUTION IN CHERT, 

BEDDED BARITE, AND OTHER ROCKS 

OF EXHALATIVE ORIGIN

The distribution of gold in rocks of exhalative origin,

exclusive of massive sulfides, was the subject of an previous

report by the SGP and USGS to the Luso American

Development Foundation (Serviços Geológicos de Portugal

and U.S. Geological Survey, 1988). The report discusses the

distribution of gold in chert and bedded barite samples collected near massive sulfide deposits at Aljustrel in the Portuguese Pyrite Belt. Samples from exhalite massive sulfide

deposits exhibited change from barite facies in the proximal

setting above the massive sulfide deposits to manganiferous

chert facies rocks 1 km or more from the massive sulfides.

The distribution of selected elements, including gold, in the

barite and chert facies are shown on figure 7.

Rock samples containing barite and chert were collected as part of the study in 1988 in the following areas in

the PPB: (1) the southernmost volcanic sub-belt, including

the Rosário-Neves-Corvo anticline, near Castro Verde in the

area between the Ferragudo manganese mine and the Serpe

manganese prospects, and (2) the São Domingos mine area

(pl. 2, map A). Additional exhalite samples were collected

from the PPB during the present reconnaissance work. 

Exhalite deposits of the PPB include chert, jasperoidal

chert, quartz-sericite-chlorite-barite rock, massive-bedded

barite, and very minor oxide and sulfide facies iron formation. Composition of the exhalites varies with respect to depositional setting relative to volcanic centers. In the following

discussion, proximal exhalites are represented by layered

sequences that include barite-rich and manganese-poor

chemical sediments. Distal exhalites include manganeserich cherts and related chemical sediments. The proximal to

distal facies changes occur over distances of 1 to 7 km. The

proximal and distal relationships reflect rapid changes in the

depositional environments and are discussed in the previous

report (Serviços Geológicos de Portugal and U.S. Geological

Survey, 1988).

To further test the distribution of gold in exhalites, a

zone across the Rosário-Neves-Corvo anticline was sampled.

The area was chosen because (1) it is distant from known

massive sulfide occurrences (11 km northwest of deposits at

Neves-Corvo) and (2) barite-rich proximal facies rocks are

exposed near the core of the anticline and manganese occurs

in exhalative cherts on the flanks (fig. 8). Most samples in

both proximal and distal settings do not have detectable

amounts of gold at the limit of determination (2 ppb) (App.

A). In the proximal setting of the Rosário-Neves-Corvo anticline, a maximum concentration of 2 ppb Au was detected in

the rock samples (fig. 8). In the distal setting, most samples

were found to contain 2 ppb or less gold, although in the

northwestern distal facies one sample contains 50 ppb and

two samples in the southeastern distal facies contain

anomalous gold (29 and 100 ppb). These weakly anomalous

amounts of gold in the distal facies are inconclusive, but they

support the conclusion at Aljustrel that gold is most highly

concentrated in the distal facies (fig. 7). 

In the São Domingos area, numerous rock types were

sampled for their gold content. The gold distribution in felsic

volcanic rocks was previously discussed in the section “Gold

in disseminated sulfide deposits, São Domingos area.”

Twenty representative samples of exhalites, stratigraphically

above the massive sulfide deposit and the felsic volcanic

rocks, were collected (App. A). Two of the 20 samples (10

percent) contained ore-grade values of gold (5.5 ppm and 30

ppm) and are located on plate. 2, map A. In contrast to other

exhalite localities, the two samples with highly anomalous

gold at São Domingos occur in exhalites with anomalously

high barite and anomalously low or normal concentrations of

manganese; the abundances of these elements are relatively

low at São Domingos as compared to exhalites in other parts

of the PPB. The rocks that overlie the exhalites at São Domingos consist of epiclastic rocks that commonly have been

weakly sericitized. The epiclastic rocks contain a maximum

of 6 ppb Au (App. A), which suggests that the gold in the

underlying exhalites may have formed at or about the time of

deposition of the exhalites or before deposition of the overlying rocks. The exhalative rocks in the São Domingos area

consist primarily of green to maroon chert with varying

amounts of pyrite. Sample no. P8SD14 contained 30 ppm

Au and is green chert with layers or bands of pyrite and

minor galena. Analytical results indicate that the anomalous

elements associated with gold mineralization include silver,

arsenic, antimony, and lead (table 5). The two samples with

highly anomalous Au contained abundant pyrite.

Studies of the exhalative rocks in the PPB lead to the

following observations related to the distribution of gold: (1)

Gold values in proximal or distal exhalite deposits are higher

when located in the vicinity of massive sulfide deposits than

when more distant from massive sulfides. (2) Where massive

sulfide deposits are overlain by barite-rich exhalites (Aljustrel), gold values increase distally toward the manganiferous

facies. São Domingos is an exception to this generality. (3)

Where massive sulfide deposits are overlain by cherty pyritic

exhalites (low barite), highly anomalous amounts of gold

may be present in the proximal facies. 

Independent studies by Rahder (1990) conducted in the

Spanish Pyrite Belt produced results similar to those in Portugal. He has noted that samples with anomalous gold as

well as arsenic and antimony are from manganiferous-facies

exhalite. He observed that sulfide-bearing jasper-facies contain only normal or background amounts of gold. This observation is consistent with our findings in all of the areas

sampled, except São Domingos where sulfide-bearing jasper-facies exhalites contain ore-grade values of gold. 

Results from our studies suggest that exhalative rocks

should be systematically analyzed for gold and associated

elements. The occurrence of highly anomalous gold values
GOLD DISTRIBUTION IN CHERT, BEDDED BARITE, AND OTHER ROCKS OF EXHALATIVE ORIGIN 23

Á

Á

Á

Á

Á Á

Á

Á

HORIZONTAL DISTANCE, IN KILOMETERS

0

0.5 1.0 1.5

Fe

Au

Mn

(10) (11)

(14)

(14)

(9)

(3)

(9)

(10 )

Proximal

Facies

Parts per

million

B

A

50,000

100,000

125,000

Ba

Distal

Facies

Manganiferous

chert



–100

–50

50

100

150

200

250

300

Sea level

Siliceous shale

and tuffite

Meters

Barite-bearing

exhalite

Feitaos Estacao

massive sulfide

deposit

Stockwork

Chert

Felsic volcanic rocks

Coarse-grained

facies

Fine-grained

facies

in the vicinity of massive sulfide deposits and an absence of

highly anomalous gold values in nonmineralized areas suggests that a study of the gold distribution in exhalites may

have limited application in the search for buried massive sulfide deposits. Although highly anomalous gold may indicate

the presence of a buried massive sulfide deposit, the presence of only background concentrations would not necessarily rule out the presence of massive sulfides; thus, caution

should be exercised applying this tool. In the vicinity of a

deposit, 90 percent or possibly more of the exhalite samples

may contain only background gold concentrations. In the

interpretation of the geochemical data, it is important to

determine which exhalite facies is present in the area.

The distribution of gold in a massive sulfide deposit

may provide clues to the distribution of gold in the overlying

exhalite deposits. As discussed in the section “Gold in massive sulfide deposits”, two modes of gold occurrence were

recognized in Australia and eastern Canada: (1) gold in the

upper zinc-rich parts of massive sulfide deposits and (2) gold

in the lower copper-rich parts of massive sulfide bodies and

Figure 7. Proximal and distal settings of exhalative chert and baritic rocks at Aljustrel, in the Portuguese

Pyrite Belt. A, Simplified geologic cross section using a vertical exaggeration ×2. B, Distribution trends of

selected elements. Values in parts per million: Fe, actual value; Mn, ×10; Ba, ×10; and Au, ×1,000. Numbers

in parentheses indicate number of quantified values used in determinations. Note, trends do not necessarily

extend beyond parameters of diagram.
24 RARE EARTH ELEMENTS AND GOLD DISTRIBUTIONS IN THE PORTUGESE PYRITE BELT

Turbidites

Ferragudo

Manganese Mine Barite-Lead Prospects

Serpa

Manganese Prospect

Felsic volcanic rocks

Distal facies

Volcanic 

Center

Felsic volcanic rocks

Proximal facies mostly coarse- to very

coarse grained pyroclastics Felsic volcanic rocks

Distal facies

S

E

E E E S

A A'

METERS

300

200

100

0

SAMP. 

No.

P7N20

P7N21

P7N22

P8N1

P8N3

P8N4

P8N5

P8N6

P8N7

P8N8

P8N9

P8N10

P8N11

P8N12

P8N13

N

N

N

N

N

<.002

N

N

N

N

N

N

N

N

.002

70 700

500

200

900

850

500

1000

>1300

>1300

200

1200

>1300

>1300

>1300

>1300

>1300

170

890

N

N

N

N

N

N

N

N

N

N

N

N

4.8

720

150

51

20

31

190

210

170

94

1.5

200

100

15

26

1

16

66

11

22

10

17

7

41

450

30

150

100

180

89

140

650

1900

64

260

220

220

2600

170

Au Ba Mn Ag Cu Pb As

N

N

N

16

34

4

16

N

N

7

17

16

5

75

DESCRIPTION

Chert-pyritic

Chert

Altered felsic tuff

Jasper w/Mag

Chert-pyritic

Chert exhalite

Bedded barite

Siliceous exhalite

Altered felsic tuff

Coarse barite

Siliceous exhalite

Siliceous exhalite

Siliceous exhalite

Coarse barite

Chert-pyritic

ANALYTICAL RESULTS

PROXIMAL FACIES

1000

1000

81

16

31

11

20

50

>5000

>24,000

1,100

>5000

700

7,900

4,000

1000

150 N

10

100

300

N

N

.002

.002

.050

N

N

N

N

<.002

P7N16

P7N17

P7N18

P7N19

P8N29

P8N30

P8N31

P8N32

SAMP. 

No. Au Ba Mn

N

N

N

N

N

N

N

<.5

Ag Cu Pb As

310

110

180

140

300

10

150

N

N

190

820

20

200

580

220

300

180

DESCRIPTION

Chert w/Mn

Chert-jasper

Chert-pyritic

Chert-pyritic

Chert w/Mn

Chert-pyritic

Vitric tuff

Siliceous exhalite

NW DISTAL FACIES

SAMP. 

No.

P7N1

P7N2

P7N3

P7N5

Au

.029

.10

N

N

Ba

30

1500 >5000

30

200

Mn

700

70

500

Ag

N

N

N

N

Cu

30

300

7

10

Ag

N

200

N

N

DESCRIPTION

Chert

Chert

Chert

Chert

Pb

15

N

10

<10

DISTAL FACIES SE

0 1 2 KILOMETERS

NORTHWEST SOUTHEAST

in the upper part of underlying stringer ore. Gold occurs in

most massive sulfide deposits in one of these settings to the

exclusion of the other (Huston and Large, 1989); the reason

for this difference is poorly understood. Commonly where

the exhalites consist of a barite-bearing proximal facies and

a manganese-chert distal-facies, anomalously high concentrations of gold are present in the barite facies if gold in the

underlying massive sulfide deposit shows a preferential partitioning in the zinc-rich part. As discussed previously, gold

in the PPB occurs primarily in the copper-rich parts of the

massive and disseminated sulfide deposits. Gold is generally

absent in the overlying barite-bearing exhalites, but is locally

present in anomalous amounts in the distal exhalite facies

which is characterized by high concentrations of manganese.

Figure 8. Interpretative cross section across Neves-Corvo anticline from the Ferragudo manganese mine to the Serpa manganese prospects; S, shale, siltstone, graywacke, and tuffite; E, chert, barite exhalites, felsic tuff, and black and purple shales. Analytical results of

selected elements in parts per million from samples of proximal and distal exhalative rocks collected on or near the line of cross section;

N, not detected at lower limit of determination; Mn, manganese; Mag, magnetite.
GOLD DISTRIBUTION IN ULTRAMAFIC AND ASSOCIATED ROCKS OF THE MOBILE BELT 25

GOLD DISTRIBUTION IN 

ULTRAMAFIC AND ASSOCIATED 

ROCKS OF THE MOBILE BELT

The Mobile Belt is a narrow structurally complex terrane that separates the SPZ to the south from the OssaMorena geologic province to the north (figs. 2, 4). The Belt

is composed largely of ultramafic rocks and associated rocks

of ophiolitic affinity. This sequence of rocks, called the

Beja-Acebuches Ophiolite by Munhá and others (1986),

crops out at the northern boundary of the Pulo do Lobo Antiform, which is a regional structure in the extreme north of the

SPZ at the boundary with the Ossa-Morena Zone. The ophiolite belt, about 1.5 km wide and more than 100 km long

along strike, contains rocks characteristic of ophiolite assemblages ranging from serpentinite, gabbro, metagabbro

(including granulite), flaser gabbro, and amphibolite at the

base to sheeted dike complex and basalt at the top. The ophiolite belt is interpreted to have formed in a back-arc basin as

shown in figure 4. It has a steep metamorphic gradient and

tectonic inversion as a result of the metamorphic terrane

overthrusting rocks of the Ossa-Morena Zone (Castro and

others, 1987). The south boundary is displaced by left lateral

faults and the ophiolite was locally dismembered by faults

during the Hercynian Orogeny. These structural relationships along with age dates from underlying rocks suggest

that the Beja-Acebuches ophiolite formed prior to the formation of the Volcanic-Siliceous Complex, the host formation

of the volcanogenic sulfide deposits of the SPZ.

The Mobile Belt in an area to the southeast of Ferreira

do Alentejo was studied by Paulo Castro of the Serviços

Geológicos de Portugal (fig. 9). His studies consisted of supplementary mapping and outcrop sampling in the ultramafic

rock terrane with the purpose of establishing the geologic

and geochemical relationship of the carbonate- and chrome

mica-altered rocks with the serpentinized ultramafic rocks in

the area. These rocks were chosen for study because similar

rocks, called listwaenites (Buisson and Leblanc, 1986), are

host to gold deposits in several different parts of the world

including the gold-bearing quartz veins of the Mother Lode

in California, USA; the Mother Lode veins are hosted in or

near quartz-carbonate-mariposite (chromium muscovite)

altered serpentinite. Listwaenites and, associated gold

deposits are located along the edges of ultramafic massifs, in

high magnesium basalts and in other ultramafic settings

where the rocks are serpentinized (Buisson and Leblanc,

1986). The occurrence of relict chromite and the abundance

of chromium, nickel, and cobalt in listwaenite is unique to

carbonate-altered rocks; these features suggest replacement

of the ultramafic rocks as a result of serpentinization. 

The rocks in the Mobile Belt are described by Castro in

the following way: (1) Layered gabbro consists of alternating layers of olivine-hypersthene gabbro, gabbro, and

anorthosite, locally ductily sheared and assumed to be Late

Devonian. Pegmatoid differentiations of similar composition are interlayered in the gabbro. Quartz-carbonate rocks

occur in the shear zones. (2) Amphibolite, interpreted to be

metamorphosed basalt, is foliated, green, fine-grained

amphibole-rich rock occurring along the Ferreira-Ficalho

Thrust. Petrographic studies suggest that the rock was subjected to lower grade metamorphism (Batista and others,

1976). (3) Granophyre (plagiogranite?) is fine-grained granite that is locally amphibolitic. Results of studies by Fonseca

and Ribeiro, (oral commun., 1988) conducted in a contiguous area suggest that the granophyre either was a product of

Precambrian magmatism or developed during Late Paleozoic ophiolite formation. (4) Metagabbro, a coarse-grained,

gabbroic rock of amphibolite to granulite metamorphic

facies, is the equivalent of the basalt in the ophiolite

sequence. (5) Serpentinite consists of undifferentiated serpentinized harzburgite, dunite, and troctolite. In most places

the serpentinite contains abundant magnetite and is locally

talcose. (6) Quartz-carbonate rock (listwaenite) occurs as

elongate bodies interpreted to be fracture controlled in contact with serpentinite and in strike-slip fault zones of left lateral movement. The rock is dominantly quartz-ankerite with

mariposite nodules in the carbonate, but contains minor latestage quartz, calcite veinlets, and minor iron sulfide. Compositional variation results in different colored rocks including

tan, light green, dark green, red, and various shades of gray.

In gabbro and metagabbro shear zones, mariposite or green

mica is lacking. Locally white mica, chlorite, and relict

chrome spinel occur. Buisson and Leblanc (1986) describe a

similar rock as a product of serpentinization. (7) Devonian

metasedimentary rocks of the Horta da Torre Formation

(Oliveira and others, 1986) consist of siltite, graywacke, and

quartzite. They occur south and north of the Ferreira-Ficalho

Thrust; to the north, they are strongly sheared and closely

associated with serpentinite and quartz-carbonate-altered

rocks.

Geochemical studies of the rocks in the Mobile Belt

consisted of the collection and analysis of representative

samples of serpentinite and the quartz-carbonate altered rock

(fig. 9). Twenty-three samples of serpentinite and 31 samples of quartz-carbonate-altered rock were collected and

analyzed to determine whether or not they are related, and to

evaluate the distribution of gold in the potentially favorable

quartz-carbonate (listwaenite) host rock. Analytical results

are included in Appendix A. 

The range of values of the ultramafic-associated elements chromium, nickel, and cobalt are very similar in the

serpentinite and the quartz-carbonate rock, suggesting that

the quartz-carbonate rock was formed as a replacement of

the ultramafic rock. In addition, the correlation coefficients

of nickel with cobalt are almost identical in the two rock

types (table 5). The gold and silver contents are extremely

low in both rock types. Precious metal values are not shown
26 RARE EARTH ELEMENTS AND GOLD DISTRIBUTIONS IN THE PORTUGESE PYRITE BELT

18

19

S

D

Á

17

21

23

20 22

Á

25

33

32

QC

Mte Novo

34 35 41 42

QC 36

37

S

40

38

39

QC

49

QC

45

46

44

43

4

S

S 5

QC

2 1

3

31 30 29

28 27

16

15

14

QC

QC

13

QC

QC

S

12

7

8 9 10 11

52

51

50 S

QC

D

47 48

D

τ

mτ

mτ

γ 

mτ

γ 

A

mτ

mτ

γ 

γ γ 

γ γ 

γ 

γ 

6 S

mτ

τ

τ

Paco Mte. do Pereiro QC

QC

QC

24

mτ D

Cabeca Alta

120°

118°

116°

204° 206° 208°

Post-Paleozoic cover

EXPLANATION

D Devonian metasediments

 quartzitic intercalations

A Amphibolite

Granophyre

Metagabbro

Contact

Photo-interpreted fault

Inferred fault

Thrust

Inferred thrust

Sample locality—Sample nos. all have 

 prefix MJB and data shown in App. A

4

γ 

mτ

τ

S Serpentinite

QC Quartz-Carbonates locally 

 with mariposite

Gabbro

0 1 2 KILOMETERS

26

Figure 9. Geology of an area southeast of Ferreira do Alentejo, south Portugal. Modified from Batista and others (1976).
CONCLUSIONS 27

in Appendix A because all samples contained less than the

lower limit of detection for gold (2 ppb) and silver (50 ppb).

The estimated average crustal abundance of gold in ultramafic rocks is 5 ppb gold (Levinson, 1974); none of the samples

analyzed contained as much as 5 ppb gold. The low precious-metal values in the serpentinite might indicate depletion in the serpentinite and enrichment in a nearby

environment in which case gold enrichment in the listwaenite would be expected; none of the listwaenite samples, however, contained detectable concentrations of gold and silver.

Characteristic features of ultramafic gold host rocks such as

development of “late-stage” quartz veins with minor sulfide

minerals are lacking in the part of the mobile belt that was

studied.

Additional studies of the Beja-Acebuches ophiolite,

and particularly the altered serpentinite, are needed to clarify

the geology of the area. Geochemical studies of arsenic, barium, boron, antimony, and bismuth may help to delimit

zones favorable for precious metals deposits.

GOLD DISTRIBUTION IN OTHER 

AREAS

Numerous localities in the volcanic sub-belts shown in

figure 2 were sampled during general reconnaissance studies. Weakly anomalous gold was found in samples from a

few localities characterized by fractured, altered, and mineralized felsic volcanic rocks. Silicification and pyritization

are the alteration effects most commonly associated with

samples containing anomalous gold.

Samples were collected from the massive sulfide mine

areas at Lousal in the eastern part of the PPB, Aljustrel and

Juliana in the central part of the PPB, and previously discussed areas at São Domingos and Neves-Corvo. Chemical

sediments (exhalites) and altered volcanic rocks are considered to be favorable host rocks for gold deposits in areas with

massive sulfide deposits. Epiclastic rocks in the PPB do not

appear to be favorable host rocks for gold deposits with the

exception of the previously deposit at Salgadinho.

The geology of the Serra Branca area near Corto Gafo

(fig. 2) was studied and extensively sampled. In this area,

rocks of the VS Complex crop out in the lower plate of a

thrust fault that places older rocks of the Phyllite-Quartzite

Group (Devonian basement) over the younger Mértola Formation Flysch and VS Complex rocks (pl. 2, map B). A

small disseminated sulfide occurrence was mapped in the

central part of the area (samples P8SB32-P8SB38); weakly

altered to relatively unaltered volcanic rocks occur throughout most of the remaining area. The weakly altered rocks,

shown as green alteration zone on cross section B-B' (pl. 2)

are bleached felsic pyroclastic rocks that commonly contain

a greenish mica, particularly along fracture surfaces. Most of

the rock samples were collected from the eastern part of the

area (pl. 2, map B) and core samples were collected in the

western part of the area (cross section A-A', pl. 2). The core

samples are primarily varied felsic volcanic and related

sedimentary rocks, and were collected to test precious metal

contents for a variety of rock and alteration types.

The volcanic sequence consists of several distinctive

tuff, agglomerate, and flow units. At the top of the volcanic

sequence, chemical sediments and maroon and green shale

underlie turbiditic sedimentary rocks of the Mértola Formation. Alteration effects in the eastern part of the area are

restricted to the felsic volcanic rocks and are mostly weakly

argillized rock with accompanying green mica (sericite?).

Rocks are more intensely sericitized or chloritized locally,

particularly near fault and shear zones. Silicification alteration is highly localized and rare. 

The 48 samples collected from a shear zone that contained vein quartz, calcite, and minor pyrite in the Serra

Branca area contained 4 ppb or less gold which is not considered to be significant (App. A). Two core samples collected

near the 200-m depth in a drill hole in the western part of the

area (A-A' on pl. 2, no. SB07) contained 10 ppb and 20 ppb

gold, respectively.

Ten samples were collected from intensely altered rhyolitic rocks southwest of the Salgadinho area. The distribution of the altered rocks and sample localities near Sao Luis

are shown on figure 6. The altered rhyolite is mostly coarse

textured and porphyritic, and is interpreted to be of subvolcanic origin. Argillic, propylitic, potassic, and intense silicic

alteration affected the rocks. Propylitic zones contain

quartz, epidote, chlorite, and pyrite. Potassic zones are characterized by veins of very coarse pink orthoclase. Narrow

quartz veins occupy high-angle fractures in the Sao Luis

quarry. An intensely silicified zone, near sample site

P8SL01 northeast of the quarry, contained highly anomalous

copper (870 ppm), lead (840 ppm), and zinc (greater than

5000 ppm). None of the samples collected in this area of

altered rhyolite contained detectable gold.

CONCLUSIONS

Areas in the PPB that contain, or are near, massive sulfide deposits are considered to be most favorable for the discovery of gold deposits. Gold in massive sulfide deposits is

most highly concentrated in the copper-rich middle and

lower parts of the sulfide deposits and, to a lesser degree, in

the underlying footwall rocks. Disseminated sulfide deposits
28 RARE EARTH ELEMENTS AND GOLD DISTRIBUTIONS IN THE PORTUGESE PYRITE BELT

that are hosted by felsic volcanic rocks may also contain

highly anomalous gold. Chemical sedimentary rocks that are

stratigraphically above several of the massive and disseminated sulfide deposits may also contain anomalous gold; gold

appears to be most highly concentrated in distal facies cherts

such as at Aljustrel, or in baritic proximal facies cherts such

as at São Domingos. Additional areas with potential for gold

in the PPB were investigated but do not appear to be promising. These include altered felsic volcanic and subvolcanic

rocks that are far removed from massive or disseminated sulfide bodies, and altered ultramafic rocks. 

The type of alteration most commonly associated with

gold enrichment is silicification which may consist of complete replacement by quartz in the rock-forming minerals or

of intrusions of closely spaced quartz veins and stringers. In

the PPB, alteration is characterized by carbonate minerals

and by sericite, but because these alteration types are widespread they are reliable indicators of gold deposits only

where they formed near or in conjunction with intense silicification.

Certain geochemical associations are also useful in the

exploration for gold deposits. In the Chança area gold is associated with arsenic, antimony, and copper and in the Salgadinho area, silver and copper appear to be the best gold

indicator elements. In exhalative rocks, copper appears to be

associated with gold in distal settings and although two samples with highly anomalous gold in proximal exhalite deposits contained highly anomalous silver, arsenic, antimony, and

lead, and moderately anomalous bismuth and barium at São

Domingos, data are insufficient to assess the potential for

gold in exhalite deposits at other proximal settings.

REFERENCES CITED

Baedecker, P.A., and McKown, D.M., 1987, Instrumental neutron

activation analysis of geochemical samples, Chapt. H, in

Baedeker, P.A., ed., Methods for geochemical analysis: U.S.

Geological Survey Bulletin 1770, p. H1–H14.

Batista, J.A., Munhá, J., Oliveira, V., and Ribeiro, L., 1976, Alguns

aspectos geologico-petrograficos da bordadura sul do Complexo Eruptivo de Beja: Lisbon, Comunicações Serviços

Geológicos de Portugal, Tomo LX, p. 203–214.

Buisson, G., and Leblanc, M. 1986, Gold-bearing listwaenites (carbonitized ultramafic rocks) in ophiolite complexes, in Gallagher, J.M. Iscer, R.A., Neary, C.R., and Prichard, H.M., eds.,

Metallogeny of basic and ultrabasic rocks: London, Institute of

Mining and Metallurgy, p. 121–132.

Campbell, L.H., Lesher, C.M., Coad, P., Franklin, J.M., Gorton,

M.P., and Thurston, P.C., 1984, Rare earth element mobility in

alteration pipes below Cu-Zn sulfide deposits: Amsterdam,

Elsevier, p. 181–202.

Carvalho, D., 1972, The metallogenic consequences of plate tectonics and the upper Paleozoic evolution of southern Portugal:

Estudos Notas Trabalhos Serviço Fomento Mineiro, v. 20, p.

297–320.

———1974, Lineament patterns and hypogene mineralization in

Portugal: 4th Symposium, International Association on Genesis of Ore Deposits, Varna, 1974, Problems of ore deposition,

v. 2, p. 444–453.

———1976, Considerações sobre do volcanismo da região de Cercal-Odemira, suas relações com a Faixa Piritosa: Lisbon,

Comunicações Serviços Geológicos Portugal, Tomo LXII, p

271–315.

———1979, Geologia, Metalogenia e Metodologia da Investigação de Sulfretos Polimetálicos do Sul de Portugal: Lisbon,

Comunicações Serviços Geológicos Portugal, no. 65, p.

169–191.

———1991, Case history of the Neves-Corvo massive sulfide

deposit, Portugal, and implications for future discoveries, in

Grauch, R.I., and Hutchinson, R.W., eds., Mineral Deposit

Research, Monograph 8 of Economic Geology, Society of Economic Geolologists, Symposium at the Geological Society of

America Centennial Meeting, Case Histories of World Class

Mineral Discoveries and Historical Perspectives p. 314–334.

Castro, P., Quesada, C., and Munhá, J., 1987, Metamorphic regime

in the Beja Acebuches Variscan ophiolite, SW Iberia, Project

233 Report, 1987 Annual Meeting, Mauritania.

Cullers, R. L., and Graf, J. L., 1984a, Rare earth elements in igneous

rocks of the continental crust—predominantly basic and ultrabasic rocks, Chapt. 7, in Henderson, P., ed., Rare Earth Element

Geochemistry: Amsterdam, Elsevier, p. 237–275.

———1984b, Rare earth elements in igneous rocks of the continental crust—intermediate and silicic rocks, ore petrogenesis,

Chapt. 8, in Henderson, P., ed., Rare Earth Element Geochemistry: Amsterdam, Elsevier, p. 275–317.

Franklin, J.M., Lydon, J.W., and Sangster, D.F., 1981, Volcanic

associated massive sulfide deposits, in Skinner, B.J., ed., Society of Economic Geology 75th Anniversary Volume: p.

485–627.

Frets, D.C., and Balde, R., 1975, Mount Morgan copper-gold

deposit, in Knight, C.L. ed., Economic geology of Australia

and Papua New Guinea; I, Metals: Australian Institute Mining

Metallurgy, Monograph 5, p. 779–785.

Graf, J.L. Jr., 1977, Rare earth elements as hydrothermal tracers

during the formation of massive sulfide deposits in volcanic

rocks: Economic Geology, v. 72, no. 4, p. 527–548.

Grimes, D.J., and Carvalho, D., 1995, Geochemical exploration

studies in the Portuguese Pyrite Belt: U.S. Geological Survey

Bulletin 2081–G, p. 53–77.

Grimes, D.J., and Marranzino, A.P., 1968, Direct current arc and

alternating-current spark emission spectrographic field methods for the semiquantitative analysis of geologic materials:

U.S. Geological Survey Circular 591, 6 p.

Huston, D.L., and Large, R.R., 1989, A chemical model for the concentration of gold in volcanogenic massive sulfide deposits:

Amsterdam, Elsevier, Ore Geology Reviews 4, p. 171–200.

Leca, X., Ribiero, A., Oliviera, J.T., Silva, J.B., Albouy,L., Carvalho, P., and Merino, H., 1983, Cadre Geologique des mineralisations de Neves-Corvo, Baixo Alentejo, Portugal: Bureau de

Recherches Geologiques et Minieres Memoir 121, 80 p.

Levinson, A.A., 1974, Introduction to exploration geochemistry:

Maywood, Ill., Applied Publishing Ltd., p. 43–44.

Lotze, F., 1945, Zur Gleiderung der Varisziden der Iberischen

Meseta: Berlin, Geotetonische Forschungen 6, p. 78–92.
REFERENCES CITED 29

Meier, A.L., 1980, Flameless atomic absorption determination of

gold in geological materials: Journal of Geochemical Exploration, v. 13, p. 77–85.

Munhá, J., 1979, Blue amphiboles, metamorphic regime and plate

tectonic modeling in the Iberian Pyrite Belt: Berlin, Contributions Mineralogy Petrology, v. 69, p. 279–289.

———1983, Hercynian magmatism in the Iberian Pyrite Belt, in

Lemos De Sousa, M.J., and Oliviera, J.T., eds., The Carboniferous of Portugal: Lisbon, Memorias Serviços Geológicos Portugal 29, p. 39–81.

Munhá, J., Oliviera, J.T., Ribiero, A., Quesada, C., and Kerrick, R.,

1986, Beja-Acebuches Ophiolite—Characterization and Geodynamic Significance [abs.]: Maleo, Sociedade Geológica de

Portugal, v. 13, no. 2, p. 31.

Motooka, J.M., and Sutley, S.J., 1982, Analysis of oxalic leachates

of geologic materials by inductively coupled plasma-atomicemission spectroscopy: Applied Spectroscopy, v. 36, p.

524–533.

Oliveira, J.T., 1983, The marine Carboniferous of South Portugal—A stratigraphic and sedimentological approach, in Lemos

de Sousa, M.J., and Oliviera, J.T., eds., The Carboniferous of

Portugal: Memórias Serviços Geológicos Portugal 29, p. 3–33.

———1990, Stratigraphy and synsedimentary tectonism, in Dottmeyer, R.D., and Martinez Garcia, E., eds., The Mesozoic

geology of Iberia: Berlin, Springer-Verlag, p. 335–347.

Oliveira, J.T., Cunha, T.A., Streel, M., and Vanguestaine, M., 1986,

Dating the Horta da Torre Formation, a new lithostratigraphic

unit of the Ferreira-Ficalho Group, South Portuguese Zone,

geological consequences: Communicações Serviços Geológicos Portugal, v. 72, nos. 1–2, p. 129–135.

Plimer, I.R., and Carvalho, D., 1982, The geochemistry of hydrothermal alteration at the Salgadinho copper deposit, Portugal:

Berlin, Mineralium Deposita, v. 17, no. 2, p. 193–211.

Rahders, E., 1990, Primary and secondary distribution of gold and

silver in host-rocks of volcanogenic massive sulfide deposits in

the pyrite belt of Southern Spain [abs.]: 8th International

Association on Genesis of Ore Deposits Symposium, Ottawa,

p. A280.

Ribeiro, A., Antunes, M.T., Ferreira, M.P., Rocha, R.B., Soares,

A.F., Zbyszewski, G., Almeida, F.M., Carvalho, D., and Monteiro, J.H., 1979, Introduction a la Geologia generale du Portugal: Lisbon, Serviços Geológicos de Portugal, Congress

International Geology 26E, Paris 1980.

Ribeiro, A., and Silva, J.B., 1983, Structure of the South Portuguese

Zone, in Lemos de Sousa, M.J., and Oliviera, J.T., eds., The

Carboniferous of Portugal: Memórias Serviços Geológicos

Portugal 29, p. 83–89.

Sato, J., 1966, On gold bearing ores found in the Shakanai Mine:

Hokkaido, Journal Mining Institute, v. 22, p. 1–6.

———1973, A chloride complex model for Kuroko mineralization: Geochemical Journal, v. 7, p. 245–270.

Serviços Geológicos de Portugal and U.S. Geological Survey,

1988, Geologic setting and composition of chert and related

rocks in the Portuguese Pyrite Belt—A Preliminary Report:

Serviços Geológicos Portugal, Progress Report 1988, 22 p.

Schermerhorn, L.J.G., 1970, The deposition of volcanics and pyritite in the Iberian Pyrite Belt: Berlin, Mineralium Deposita, v.

5, no. 3, p. 273–279.

———1971, An outline stratigraphy of the Iberian Pyrite Belt:

Madrid, Boletin Geologico y Minero, v. 82, nos. 3–4, p.

239–268.

———1975, Spilites, regional metamorphism and subduction in

the Iberian Pyrite Belt—some comments: Hague, Geologische

Bureau voor Het Mijngebied, v. 54, no. 1, p. 23-35.

Strauss, G.K., and Beck, J.S., 1990, Gold mineralization in the

southwestern Iberian Pyrite Belt: Berlin, Mineralium Deposita,

v. 25, p. 237–245.

Published in the Central Region, Denver, Colorado

Manuscript approved for publication December 17, 1997

Graphics prepared by Norma J. Maes and Mike Kirtley

Photocomposition by Norma J. Maes
APPENDIX
32 RARE EARTH ELEMENTS AND GOLD DISTRIBUTIONS IN THE PORTUGESE PYRITE BELT

Appendix A. Analytical results for selected elements in rocks from the Portuguese Pyrite Belt.

[L, less than limit of determination; N, not detected at the lower limit of determination]

1. CHANÇA AREA—ALL ROCK TYPES

Sample No. Ag As Au Bi Cu Mo Pb Sb Zn

BH301 N0.025 44.0 N0.002 N1.0 2.7 1.0 N1.0 N1.0 23

BH302 N0.025 5.3 N0.002 N1.0 40.0 1.0 N1.0 N1.0 36

BH303 N0.025 N1.0 N0.002 N1.0 24.0 1.0 6.4 N1.0 74

BH304 N0.025 33.0 N0.002 N1.0 15.0 1.0 N1.0 N1.0 10

BH305 N0.025 23.0 0.008 9.9 12.0 1.0 14.0 N1.0 12

BH306 N0.025 29.0 L0.002 6.9 11.0 1.0 13.0 N1.0 28

BH307 N0.025 52.0 0.004 N1.0 20.0 1.0 26.0 N1.0 200

BH308 N0.025 52.0 N0.002 N1.0 6.3 1.0 17.0 N1.0 140

BH309 N0.025 52.0 0.014 N1.0 21.0 1.0 39.0 N1.0 23

BH310 0.047 35.0 0.006 7.3 17.0 1.0 19.0 N1.0 19

BH311 N0.025 24.0 0.006 N1.0 12.0 1.0 25.0 N1.0 86

BH312 N0.025 140.0 0.002 N1.0 9.2 1.0 91.0 N1.0 64

BH313 N0.025 23.0 N0.002 10.0 39.0 1.0 51.0 N1.0 86

BH314 7.800 160.0 0.004 12.0 320.0 1.9 150.0 64.0 290

BH315 1.200 43.0 0.002 11.0 12.0 1.0 20.0 7.9 15

BH316 0.570 31.0 L0.002 7.9 23.0 1.0 16.0 N1.0 23

BH317 N0.025 38.0 N0.002 N1.0 3.5 1.0 10.0 N1.0 30

BH318 N0.025 31.0 N0.002 N1.0 31.0 8.7 18.0 N1.0 11

CH101 N0.025 36.0 N0.002 N1.0 17.0 N1.0 N1.0 1.0 23

CH102 N0.025 N1.0 L0.002 N1.0 7.7 N1.0 N1.0 1.0 36

CH103 N0.025 N1.0 0.004 N1.0 2.7 N1.0 6.9 1.0 32

CH104 N0.025 39.0 L0.002 N1.0 12.0 N1.0 15.0 1.0 54

CH105 N0.025 57.0 L0.002 6.2 9.9 N1.0 13.0 1.0 30

CH106 N0.025 26.0 N0.002 7.7 12.0 N1.0 23.0 1.0 37

CH107 N0.025 32.0 0.004 6.8 17.0 N1.0 16.0 1.0 23

CH108 N0.025 95.0 L0.002 N1.0 35.0 N1.0 49.0 1.0 140

CH109 N0.025 500.0 0.150 N1.0 2000.0 N1.0 54.0 1.0 N1

CH110 N0.025 100.0 0.044 18.0 5000.0 N1.0 20.0 1.0 57

CH111 N0.025 350.0 0.200 N1.0 2000.0 27.0 90.0 67.0 N1

CH112 N0.025 37.0 0.048 N1.0 88.0 N1.0 68.0 1.0 73

CH113 N0.025 N1.0 L0.002 N1.0 6.8 N1.0 9.3 1.0 66

P8CH01 N0.025 15.0 L0.002 N1.0 17.0 N1.0 7.4 N1.0 7

P8CH02 N0.025 20.0 N0.002 N1.0 4.1 N1.0 N1.0 N1.0 11

P8CH03 N0.025 30.0 L0.002 N1.0 8.9 50.0 N1.0 N1.0 63

P8CH04 N0.025 19.0 N0.002 N1.0 9.2 N1.0 6.6 N1.0 49

P8CH05 N0.025 220.0 0.050 N1.0 160.0 L1.0 23.0 N1.0 41

P8CH06 1.500 34.0 0.006 N1.0 4.9 1.3 46.0 N1.0 8

P8CH07 N0.025 34.0 L0.002 N1.0 33.0 N1.0 24.0 N1.0 77

P8CH08 N0.025 5.3 N0.002 N1.0 12.0 N1.0 11.0 N1.0 85

P8CH09 N0.025 89.0 0.046 N1.0 75.0 N1.0 N1.0 N1.0 41

P8CH10 N0.025 110.0 0.012 N1.0 160.0 N1.0 N1.0 N1.0 61

P8CH11 N0.025 8.6 N0.002 N1.0 4.4 N1.0 N1.0 N1.0 24

P8CH12 N0.025 N1.0 N0.002 N1.0 29.0 N1.0 N1.0 N1.0 89

P8CH13 N0.025 N1.0 0.016 N1.0 1.0 N1.0 N1.0 N1.0 5

P8CH14 N0.025 41.0 0.002 N1.0 74.0 N1.0 5.4 N1.0 18

P8CH15 N0.025 300.0 0.010 N1.0 110.0 3.1 15.0 N1.0 13

P8CH16 N0.025 89.0 0.020 N1.0 2.1 N1.0 48.0 N1.0 15
REFERENCES CITED 33

P8CH17 N0.025 94.0 0.006 N1.0 97.0 N1.0 43.0 N1.0 13

P8CH18 N0.025 8.8 N0.002 N1.0 5.2 N1.0 18.0 N1.0 40

P8CH19 N0.025 28.0 N0.002 N1.0 21.0 N1.0 10.0 N1.0 53

P8CH20 N0.025 20.0 N0.002 N1.0 17.0 N1.0 5.4 N1.0 31

2. SALGADINHO AREA—EPICLASTIC ROCKS

Sample No. Ag As Au Bi Cu Pb Zn

SL0502 N0.025 17.0 L0.002 N1.0 28.0 32.0 75

SL0503 N0.025 15.0 L0.002 N1.0 12.0 11.0 77

SL0513 N0.025 15.0 N0.002 N1.0 4.7 13.0 26

SL0516 N0.025 7.6 0.004 7.0 29.0 12.0 77

SL0518 N0.025 13.0 0.050 N1.0 410.0 16.0 71

SL0521 1.800 26.0 4.800 N1.0 1200.0 38.0 97

SL0523 23.000 92.0 0.150 110.0 8300.0 570.0 440

SL0524 11.000 42.0 0.018 68.0 8600.0 57.0 66

SL0702 N0.025 23.0 L0.002 N1.0 37.0 7.4 46

SL0713 N0.025 25.0 N0.002 N1.0 15.0 13.0 55

SL0704 55.000 69.0 2.700 210.0 2000.0 1700.0 1800

SL0706 N0.025 24.0 0.002 6.9 20.0 27.0 98

SL0707 N0.025 16.0 N0.002 N1.0 20.0 16.0 62

SL1501 N0.025 10.0 0.002 N1.0 5.2 160.0 73

SL1502 N0.025 29.0 0.010 11.0 5.1 10.0 64

SL1503 N0.025 25.0 N0.002 N1.0 2.3 N1.0 55

SL1504 1.500 22.0 0.008 8.1 2600.0 6.0 190

SL1505 N0.025 9.9 0.004 6.0 2.5 1.0 35

SL1513 N0.025 20.0 L0.002 6.3 15.0 93.0 420

SL1514 5.800 16.0 0.150 21.0 230.0 260.0 69

SL1901 N0.025 23.0 0.002 N1.0 26.0 N1.0 65

SL1902 N0.025 9.5 N0.002 N1.0 12.0 N1.0 41

SL1903 N0.025 11.0 N0.002 N1.0 31.0 36.0 68

SL1904 N0.025 18.0 L0.002 N1.0 37.0 110.0 110

SL1905 N0.025 18.0 L0.002 N1.0 16.0 20.0 76

SL1906 1.200 54.0 0.022 N1.0 34.0 1300.0 2400

SL1907 N0.025 47.0 0.012 N1.0 48.0 200.0 130

SL1908 N0.025 25.0 0.006 N1.0 39.0 51.0 130

SL1913 N0.025 5.5 0.004 N1.0 4.8 1.0 36

SL1914 N0.025 23.0 0.040 N1.0 4.5 10.0 59

SL1916 N0.025 45.0 0.008 N1.0 21.0 40.0 59

SL1917 N0.025 30.0 0.004 7.2 3.4 440.0 1300

SL1918 N0.025 16.0 L0.002 8.6 8.0 56.0 30

SL2101 N0.025 7.0 0.002 8.6 6.9 7.6 95

SL2104 N0.025 14.0 L0.002 N1.0 4.5 5.2 60

SL2105 N0.025 38.0 0.008 N1.0 48.0 23.0 73

SL2401 1.200 44.0 0.006 N1.0 13.0 430.0 370

SL2402 N0.025 35.0 0.002 N1.0 16.0 320.0 1600

SL2411 N0.025 59.0 0.002 N1.0 35.0 16.0 19

SL2412 N0.025 63.0 0.014 N1.0 13.0 17.0 65

SL2413 N0.025 21.0 N0.002 N1.0 2.9 6.2 50

SL2414 N0.025 35.0 0.150 N1.0 36.0 73.0 89

SL2415 N0.025 36.0 0.008 N1.0 34.0 19.0 58

SL2601 N0.025 33.0 0.004 N1.0 22.0 9.1 76

SL2608 N0.025 20.0 N0.002 N1.0 38.0 7.3 76

SL2611 N0.025 67.0 0.004 N1.0 9.1 300.0 64

SL2612 N0.025 23.0 N0.002 N1.0 64.0 76.0 88

APPENDIX
34 RARE EARTH ELEMENTS AND GOLD DISTRIBUTIONS IN THE PORTUGESE PYRITE BELT

SL2802 N0.025 N1.0 N0.002 N1.0 6.1 14.0 74

SL2803 N0.025 27.0 N0.002 N1.0 17.0 9.6 79

SL2804 N0.025 23.0 N0.002 N1.0 23.0 24.0 85

SL2805 N0.025 14.0 N0.002 N1.0 5.2 18.0 320

SL2806 N0.025 N1.0 N0.002 N1.0 0.9 N1.0 36

SL2807 N0.025 19.0 L0.002 N1.0 59.0 N1.0 49

SL2808 N0.025 21.0 L0.002 N1.0 31.0 51.0 100

SL2809 N0.025 14000.0 0.600 N1.0 970.0 250.0 2400

SL2810 N0.025 N1.0 L0.002 N1.0 12.0 N1.0 55

SL2811 N0.025 60.0 L0.002 N1.0 4.7 10.0 80

SL2813 N0.025 41.0 L0.002 N1.0 28.0 33.0 100

SL2815 N0.025 88.0 N0.002 N1.0 6.6 N1.0 31

SL2817 11.000 130.0 0.250 N1.0 2000.0 83.0 N1

SL2818 0.570 14.0 0.150 N1.0 1100.0 11.0 39

SL2819 N0.025 41.0 0.002 N1.0 36.0 N1.0 95

SL2821 88.000 830.0 1.400 150.0 2000.0 5.7 N1

3. SALGADINHO AREA—FELSIC VOLCANIC ROCKS

Sample No. Ag As Au Bi Cu Mo Pb Zn

P8SA1 N0.025 370.0 0.028 N1.0 80.0 N1.0 N1.0 1500

P8SA2 0.560 21.0 0.002 15.0 84.0 14.0 60.0 580

P8SA3 N0.025 36.0 L0.002 N1.0 55.0 N1.0 N1.0 510

SL0506 N0.025 N1.0 0.002 N1.0 2.6 N1.0 9.9 17

SL0510 N0.025 17.0 L0.002 N1.0 8.0 N1.0 11.0 48

SL0511 N0.025 41.0 0.006 N1.0 16.0 N1.0 35.0 69

SL0512 N0.025 25.0 L0.002 N1.0 17.0 N1.0 27.0 92

SL0519 4.500 36.0 0.038 N1.0 2000.0 1.3 110.0 2400

SL0520 N0.025 24.0 0.018 7.4 220.0 2.5 11.0 24

SL0710 N0.025 19.0 N0.002 6.9 20.0 1.6 21.0 84

SL0711 N0.025 6.2 N0.002 8.0 5.7 N1.0 7.6 52

SL0712 N0.025 N1.0 N0.002 N1.0 11.0 N1.0 N1.0 67

SL0713 N0.025 N1.0 N0.002 11.0 12.0 1.1 34.0 27

SL0714 N0.025 28.0 N0.002 11.0 11.0 2.3 27.0 60

SL1506 N0.025 16.0 0.002 8.6 11.0 2.2 8.4 130

SL1509 N0.025 32.0 0.200 6.2 29.0 N1.0 7.8 69

SL1516 N0.025 23.0 N0.002 6.0 17.0 N1.0 400.0 200

SL1518 N0.025 15.0 N0.002 N1.0 6.5 N1.0 130.0 110

SL1519 N0.025 15.0 N0.002 6.9 36.0 N1.0 14.0 72

SL1919 N0.025 23.0 0.002 7.1 24.0 N1.0 36.0 68

SL1919A N0.025 48.0 0.004 N1.0 11.0 N1.0 35.0 59

SL2102 N0.025 28.0 0.018 9.9 51.0 3.0 41.0 160

SL2103 N0.025 4.6 0.002 9.6 46.0 N1.0 11.0 49

SL2405 N0.025 160.0 0.012 N1.0 130.0 N1.0 560.0 530

SL2406 11.000 19.0 1.600 N1.0 4000.0 N1.0 150.0 N1

SL2407 4.600 53.0 0.100 N1.0 4000.0 N1.0 68.0 620

SL2408 2.300 54.0 0.250 N1.0 2300.0 N1.0 150.0 75

SL2409 0.920 88.0 0.032 N1.0 2300.0 N1.0 23.0 29

SL2605 N0.025 15.0 0.002 N1.0 170.0 N1.0 21.0 29

SL2606 N0.025 100.0 0.034 N1.0 330.0 N1.0 75.0 25

SL2607 3.400 170.0 0.300 N1.0 1200.0 N1.0 200.0 46

SL2812 N0.025 41.0 0.025 N1.0 180.0 N1.0 39.0 40

SL2822 N0.025 18.0 N0.002 N1.0 20.0 N1.0 5.7 82

SL1517 N0.025 8.7 N0.002 6.8 14.0 N1.0 380.0 110

SL0522 N0.025 23.0 0.004 N1.0 22.0 N1.0 13.0 41
REFERENCES CITED 35

SL0701 N0.025 36.0 L0.002 6.9 66.0 N1.0 110.0 110

SL0705 N0.025 11.0 N0.002 N1.0 19.0 N1.0 17.0 76

SL0707 N0.025 16.0 N0.002 N1.0 20.0 N1.0 16.0 62

SL1909 N0.025 10.0 L0.002 N1.0 10.0 N1.0 14.0 900

SL1910 N0.025 28.0 0.002 N1.0 9.2 N1.0 1.0 87

SL1911 N0.025 59.0 0.004 N1.0 16.0 N1.0 28.0 91

SL1912 1.900 160.0 0.100 N1.0 2600.0 N1.0 44.0 1400

SL2410 5.000 85.0 2.000 N1.0 4000.0 N1.0 24.0 N1

SL2602 N0.025 23.0 0.004 N1.0 41.0 N1.0 19.0 160

SL2603 N0.025 20.0 L0.002 N1.0 43.0 N1.0 55.0 39

SL2604 N0.025 15.0 N0.002 N1.0 19.0 N1.0 1.0 52

4. SALGADINHO AREA—VEINS AND BRECCIAS

Sample No. Ag As Au Bi Cu Pb Sb Zn

SL0301 7.000 33.0 0.016 51.0 8300.0 50.0 20 62

SL0501 N0.025 55.0 0.008 N1.0 21.0 20.0 N1 31

SL0504 N0.025 15.0 N0.002 N1.0 15.0 66.0 N1 76

SL0505 N0.025 3.5 N0.002 N1.0 27.0 62.0 N1 150

SL0508 N0.025 36.0 0.006 N1.0 51.0 5.2 N1 58

SL0509 N0.025 16.0 0.004 6.1 3.7 17.0 N1 30

SL0514 N0.025 56.0 0.032 N1.0 150.0 90.0 N1 410

SL0515 2.900 65.0 0.250 15.0 3300.0 87.0 N1 370

SL0517 1.200 47.0 1.300 9.5 1300.0 47.0 N1 130

SL0524 11.000 42.0 0.018 68.0 8600.0 57.0 40 66

SL0709 0.500 27.0 0.002 11.0 19.0 21.0 N1 66

SL1507 N0.025 35.0 0.030 N1.0 33.0 N1.0 N1 94

SL1508 N0.025 49.0 L0.002 N1.0 8.1 N1.0 N1 42

SL1509 N0.025 32.0 0.200 6.2 29.0 7.8 N1 69

SL1510 N0.025 21.0 L0.002 N1.0 23.0 12.0 N1 71

SL1511 N0.025 25.0 L0.002 N1.0 39.0 18.0 N1 55

SL1512 2.900 18.0 0.020 14.0 2800.0 98.0 N1 490

SL1515 N0.025 13.0 L0.002 6.0 46.0 14.0 N1 90

SL1915 2.400 17.0 0.044 21.0 18.0 38.0 N1 69

SL2404 N0.025 21.0 0.002 N1.0 180.0 140.0 N1 420

SL2609 N0.025 22.0 0.100 N1.0 58.0 N1.0 N1 44

SL2610 N0.025 15.0 0.900 N1.0 1000.0 N1.0 N1 110

SL2801 N0.025 27.0 N0.002 N1.0 10.0 36.0 N1 130

SL2814 N0.025 230.0 0.100 N1.0 N1.0 N1.0 N1 110

SL2816 N0.025 73.0 L0.002 N1.0 41.0 7.4 N1 43

SL2823 N0.025 5.9 N0.002 N1.0 21.0 12.0 N1 94

5. SÃO DOMINGOS AREA—FELSIC VOLCANIC ROCKS

Sample No. Ag As Au Bi Cu Mo Pb Sb Zn

MP303 N0.025 N1.0 N0.002 N1.0 0.9 N1 5.9 N1.0 4

MP304 N0.025 N1.0 N0.002 N1.0 0.8 N1 5.5 N1.0 N1

MP316 N0.025 19.0 N0.002 N1.0 9.3 N1 12.0 N1.0 41

MP317 N0.025 N1.0 N0.002 N1.0 3.4 N1 26.0 N1.0 6

MP318 N0.025 N1.0 N0.002 N1.0 1.4 N1 N1.0 N1.0 2

MP319 N0.025 3.5 N0.002 N1.0 3.3 N1 23.0 N1.0 6

MP320 N0.025 3.4 N0.002 N1.0 4.3 N1 19.0 N1.0 19

MP321 N0.025 12.0 N0.002 N1.0 26.0 N1 18.0 N1.0 71

MP322 N0.025 N1.0 N0.002 N1.0 1.4 N1 N1.0 N1.0 29

MP323 N0.025 N1.0 N0.002 N1.0 2.8 N1 N1.0 N1.0 23

MP324 N0.025 N1.0 N0.002 N1.0 1.6 N1 13.0 N1.0 25

APPENDIX
36 RARE EARTH ELEMENTS AND GOLD DISTRIBUTIONS IN THE PORTUGESE PYRITE BELT

MP325 N0.025 6.4 N0.002 N1.0 2.1 N1 9.7 N1.0 35

MP326 N0.025 N1.0 N0.002 N1.0 8.0 N1 N1.0 N1.0 100

MP327 N0.025 N1.0 N0.002 N1.0 14.0 N1 N1.0 N1.0 69

P8SD10 4.300 120.0 0.100 6.7 140.0 N1 920.0 N1.0 8

P8SD11 N0.025 34.0 L0.002 N1.0 29.0 N1 12.0 5.6 2

P8SD12 0.470 140.0 0.012 N1.0 81.0 N1 24.0 N1.0 14

P8SD13 N0.025 170.0 L0.002 N1.0 57.0 N1 87.0 N1.0 5

P8SD15 N0.025 190.0 0.004 N1.0 170.0 N1 67.0 N1.0 13

P8SD45 N0.025 5.6 0.006 N1.0 5.6 N1 23.0 N1.0 13

P8SD46A N0.025 160.0 0.950 N1.0 18.0 50 15.0 N1.0 12

P8SD47 N0.025 3.3 0.200 8.6 5.7 N1 7.3 N1.0 25

6. SÃO DOMINGOS AREA—INTERMEDIATE TO BASIC VOLCANIC ROCKS

Sample No. Ag As Au Cu Pb Sb Zn

MSD103 N0.025 N1.0 L0.002 16.0 N1.0 N1.0 1500

MSD104 N0.025 N1.0 L0.002 5.6 N1.0 N1.0 1200

MSD105 N0.025 N1.0 N0.002 5.6 N1.0 N1.0 1100

MSD106 N0.025 11.0 N0.002 1.5 7.4 N1.0 2400

MSD107 N0.025 N1.0 N0.002 1.0 N1.0 N1.0 2400

MSD108 N0.025 5.5 N0.002 2.0 N1.0 N1.0 160

MSD109 N0.025 N1.0 N0.002 300.0 N1.0 N1.0 62

MSD110 N0.025 4.2 0.006 23.0 N1.0 N1.0 120

MSD111 N0.025 N1.0 0.004 29.0 N1.0 N1.0 110

MSD112 N0.025 3.0 N0.002 26.0 N1.0 N1.0 75

MSD113 N0.025 25.0 L0.002 40.0 N1.0 N1.0 150

MSD114 N0.025 N1.0 N0.002 33.0 N1.0 N1.0 120

MSD115 N0.025 N1.0 N0.002 17.0 N1.0 N1.0 89

MSD116 N0.025 N1.0 N0.002 11.0 N1.0 N1.0 110

MSD117 N0.025 N1.0 N0.002 54.0 N1.0 N1.0 140

MSD118 N0.025 N1.0 N0.002 7.3 N1.0 N1.0 120

MSD119 N0.025 N1.0 N0.002 9.7 N1.0 N1.0 87

MSD120 N0.025 N1.0 L0.002 9.4 5.1 N1.0 110

MSD121 N0.025 N1.0 N0.002 26.0 N1.0 N1.0 100

MSD122 N0.025 N1.0 N0.002 15.0 N1.0 N1.0 110

MSD123 N0.025 17.0 0.002 2600.0 N1.0 N1.0 75

MSD124 N0.025 66.0 N0.002 24.0 N1.0 N1.0 54

P8SD16 N0.025 22.0 N0.002 38.0 130.0 N1.0 280

P8SD17 N0.025 41.0 L0.002 64.0 58.0 N1.0 240

P8SD18 N0.025 N1.0 N0.002 26.0 600.0 N1.0 670

P8SD29 N0.025 N1.0 L0.002 28.0 26.0 N1.0 2400

P8SD30 N0.025 35.0 L0.002 210.0 53.0 N1.0 200

P8SD34 N0.025 160.0 L0.002 61.0 34.0 N1.0 30

P8SD35 N0.025 120.0 0.002 30.0 28.0 N1.0 21

P8SD36 N0.025 600.0 0.004 30.0 170.0 9.8 43

7. SÃO DOMINGOS AREA—EPICLASTIC ROCKS

Sample No. Ag As Au Ba Bi Cu Mo Pb Zn

P8SD19 N0.025 10.0 0.004 31 N1.0 98.0 N1.0 21.0 470

P8SD20 N0.025 N1.0 L0.002 38 N1.0 70.0 N1.0 6.4 410

P8SD21 N0.025 61.0 0.002 19 N1.0 180.0 N1.0 34.0 85

P8SD22 N0.025 16.0 0.002 34 N1.0 58.0 N1.0 15.0 930

P8SD23 N0.025 17.0 N0.002 24 N1.0 100.0 N1.0 8.9 810

P8SD24 N0.025 18.0 N0.002 19 N1.0 83.0 N1.0 N1.0 77
REFERENCES CITED 37

P8SD25 N0.025 900.0 N0.002 10 N1.0 160.0 N1.0 N1.0 640

P8SD26 N0.025 14.0 L0.002 15 N1.0 85.0 N1.0 7.8 35

P8SD27 N0.025 150.0 L0.002 10 N1.0 360.0 N1.0 24.0 280

P8SD28 N0.025 38.0 L0.002 17 N1.0 70.0 N1.0 10.0 22

P8SD31 N0.025 N1.0 N0.002 9 N1.0 1100.0 N1.0 N1.0 2400

P8SD32 N0.025 45.0 0.002 10 N1.0 470.0 9.1 25.0 22

P8SD33 N0.025 600.0 N0.002 170 N1.0 29.0 N1.0 260.0 15

P8SD37 N0.025 210.0 0.004 18 N1.0 72.0 N1.0 8.7 1200

P8SD38 N0.025 40.0 N0.002 6 N1.0 88.0 2.1 13.0 140

P8SD39 N0.025 5.6 N0.002 25 N1.0 19.6 N1.0 32.0 320

P8SD40 N0.025 6.6 L0.002 34 N1.0 13.0 N1.0 23.0 380

P8SD41 N0.025 4.6 N0.002 23 N1.0 5.6 N1.0 27.0 950

P8SD42 N0.025 4.0 L0.002 15 N1.0 6.1 N1.0 24.0 930

P8SD43 N0.025 15.0 N0.002 17 N1.0 15.0 N1.0 13.0 300

P8SD06 0.640 45.0 L0.002 12 12.0 1900.0 N1.0 8.3 30

P8SD07 N0.025 140.0 N0.002 11 N1.0 510.0 N1.0 7.3 32

P8SD08 N0.025 2400.0 N0.002 9 N1.0 1400.0 N1.0 N1.0 97

P8SD09 N0.025 9.8 N0.002 13 7.1 40.0 N1.0 8.7 91

MP301 N0.025 N1.0 L0.002 15 N1.0 15.0 N1.0 N1.0 11

MP302 N0.025 7.0 N0.002 21 N1.0 35.0 N1.0 9.1 32

MSD101 N0.025 15.0 0.006 36 N1.0 56.0 N1.0 7.8 510

MSD102 N0.025 65.0 0.006 36 N1.0 120.0 1.7 78.0 180

MSD125 N0.025 6.9 L0.002 34 N1.0 31.0 N1.0 N1.0 61

MSD126 N0.025 N1.0 L0.002 29 N1.0 3.0 N1.0 N1.0 32

MSD127 N0.025 3.2 N0.002 24 N1.0 5.7 N1.0 N1.0 40

MSD128 N0.025 3.1 0.002 26 N1.0 2.4 N1.0 N1.0 23

MSD129 N0.025 25.0 N0.002 19 N1.0 5.3 15.0 8.1 23

MSD130 N0.025 7.1 L0.002 61 N1.0 33.0 N1.0 38.0 45

MSD131 N0.025 11.0 L0.002 32 N1.0 11.0 N1.0 7.1 35

P8SD04 0.530 24.0 N0.002 28 7.3 78.0 N1.0 9.9 16

P8SD05 N0.025 33.0 N0.002 18 N1.0 150.0 N1.0 5.5 80

8. SÃO DOMINGOS AREA—CHEMICAL SEDIMENTS (EXHALITES)

S. No. Ag As Au Ba Bi Cu Mn Mo Pb SbZn

MP305 N0.025 N1.0 N0.002 21 N1 2.1 57 N1.0 18.0 N12

MP305a N0.025 3.9 N0.002 21 N1 3.2 670 N1.0 11.0 N12

MP306 N0.025 3.3 N0.002 25 N1 2.4 140 N1.0 8.5 N12

MP307 N0.025 N1.0 N0.002 23 N1 2.9 62 N1.0 12.0 N14

MP308 N0.025 8.7 N0.002 25 N1 1.4 34 N1.0 17.0 N19

MP309 N0.025 29.0 N0.002 18 N1 28.0 280 N1.0 66.0 N139

MP310 N0.025 N1.0 N0.002 15 N1 5.9 46 N1.0 7.4 N15

MP311 N0.025 N1.0 N0.002 23 N1 2.8 30 N1.0 23.0 N15

MP312 N0.025 N1.0 N0.002 16 N1 1.8 46 N1.0 N1.0 N12

MP313 N0.025 N1.0 N0.002 18 N1 1.6 110 N1.0 24.0 N16

MP314 N0.025 3.5 N0.002 11 N1 3.8 35 N1.0 6.6 N15

MP315 N0.025 N1.0 N0.002 17 N1 2.0 73 N1.0 16.0 N16

MP328 N0.025 N1.0 N0.002 25 N1 7.3 690 N1.0 N1.0 N1120

MP329 N0.025 N1.0 N0.002 10 N1 3.6 190 N1.0 N1.0 N125

MP330 N0.025 N1.0 N0.002 13 N1 11.0 600 N1.0 N1.0 N167

P8SD1 N0.025 110.0 0.006 190 N1 820.0 120 N1.0 82.0 N189

P8SD2 N0.025 340.0 0.010 44 N1 790.0 95 N1.0 110.0 N197

P8SD3 N0.025 1200.0 N0.002 16 N1 680.0 76 N1.0 46.0 N193

P8SD14 73.000 940.0 30.000 110 43 40.0 57 2.4 2300.0 8811

P8SD44 4.000 970.0 5.500 120 6 35.0 28 2.2 2400.0 2412

APPENDIX
38 RARE EARTH ELEMENTS AND GOLD DISTRIBUTIONS IN THE PORTUGESE PYRITE BELT

9. CHEMICAL SEDIMENTS (EXHALITES)—DISTAL SETTING

S. No. Ag As Au Ba Bi Cu Mn Pb Sb Zn

P8N24 N0.025 73 0.002 1100 N1 16 29000 N1.0 N1 56

P8N26 N0.025 10 L0.002 42 N1 39 5800 1100.0 N1 710

P8N27 N0.025 53 N0.002 98 N1 31 240 9.2 N1 51

P8N28 N0.025 49 N0.002 56 N1 34 770 20.0 N1 130

P8N29 N0.025 580 N0.002 81 N1 310 24000 N1.0 N1 800

P8N30 N0.025 220 N0.002 11 N1 110 1100 190.0 N1 90

P8N31 N0.025 300 L0.002 16 N1 180 7900 820.0 N1 370

P8N32 N0.025 180 N0.002 31 N1 140 4000 20.0 N1 130

P8AL1 N0.025 110 L0.002 480 N1 660 3800 130.0 98 250

P8AL2 N0.025 23 0.050 8 N1 410 2400 23.0 N1 260

10. CHEMICAL SEDIMENTS (EXHALITES)—PROXIMAL SETTING

S. No. Ag As Au Ba Bi Cu Mn Pb Sb Zn

P8N01 N0.025 16.0 N0.002 1300 7.5 26.0 900 180.0 N1.0 81.0

P8N03 N0.025 34.0 N0.002 1300 N1.0 0.5 850 89.0 N1.0 15.0

P8N04 N0.025 4.4 N0.002 200 N1.0 16.0 720 140.0 N1.0 27.0

P8N05 N0.025 16.0 N0.002 1200 8.6 66.0 150 650.0 N1.0 120.0

P8N06 N0.025 N1.0 N0.002 1300 N1.0 11.0 51 1900.0 N1.0 17.0

P8N07 N0.025 N1.0 0.002 1300 N1.0 22.0 20 64.0 N1.0 11.0

P8N08 N0.025 7.3 N0.002 1300 N1.0 10.0 31 260.0 N1.0 24.0

P8N09 N0.025 17.0 N0.002 170 N1.0 17.0 190 220.0 N1.0 680.0

P8N10 N0.025 16.0 N0.002 1300 8.3 7.4 210 170.0 N1.0 6.6

P8N11 N0.025 5.3 N0.002 1300 7.4 41.0 170 220.0 N1.0 100.0

P8N12 4.800 75.0 N0.002 890 8.4 450.0 94 2600.0 64.0 1100.0

P8N13 1.300 9.9 0.002 920 9.0 130.0 37 32.0 37.0 13.0

P8N14 0.630 5.0 N0.002 400 8.7 430.0 92 17.0 N1.0 42.0

P8N15 0.870 13.0 N0.002 1300 12.0 180.0 12 150.0 10.0 34.0

P8N17 1.100 4.7 N0.002 990 13.0 31.0 32 29.0 6.0 11.0

P8N18 1.400 8.6 N0.002 230 12.0 260.0 66 170.0 7.6 41.0

P8N19 1.400 11.0 N0.002 350 12.0 100.0 45 96.0 74.0 30.0

P8N20 1.300 10.0 N0.002 1300 15.0 170.0 80 290.0 7.7 54.0

P8N21 N0.025 7.0 N0.002 320 12.0 4.1 94 29.0 N1.0 15.0

P8N22 N0.025 120.0 N0.002 4000 19.0 500.0 23 420.0 N1.0 270.0

P8N23 N0.025 1.0 N0.002 960 N1.0 6.1 96 19.0 N1.0 28.0

P8N33 N0.025 8.9 N0.002 250 N1.0 10.0 79 16.0 N1.0 17.0

P8N34 N0.025 7.7 N0.002 1200 N1.0 7.0 67 59.0 N1.0 17.0

P8N35 N0.025 6.0 N0.002 85 N1.0 2.0 35 6.7 N1.0 11.0

P8N36 N0.025 41.0 N0.002 120 N1.0 43.0 230 190.0 N1.0 500.0

P8N37 N0.025 5.1 N0.002 380 N1.0 1000.0 87 150.0 N1.0 88.0

P8N38 N0.025 5.3 N0.002 1300 N1.0 4.5 100 7.8 N1.0 7.9

11. MOMBEJA AREA—SERPENTINITE

Sample No.Co Cr Cu Ni Zn

MBJ02B 11 14 59 29 27

MBJ03 60 110 65 670 27

MBJ04 85 260 65 1500 44

MBJ06 58 150 97 600 32

MBJ12 57 120 30 720 31
REFERENCES CITED 39

MBJ17 56 99 26 820 27

MBJ18 84 110 20 1700 31

MBJ20 85 190 35 1700 32

MBJ21 16 180 18 240 7

MBJ23 69 140 11 1300 31

MBJ29 42 210 41 830 10

MBJ33 62 140 21 1100 26

MBJ34B 21 210 73 300 6

MBJ38 63 410 150 880 25

MBJ40 46 230 55 1200 23

MBJ42 52 210 20 940 20

MBJ44 54 85 57 600 22

MBJ46 57 18 41 790 19

MBJ48 69 190 77 1000 31

MBJ49 68 310 40 1000 24

MBJ50 48 240 25 370 31

MBJ51 49 180 55 610 24

MBJ52 58 190 25 930 20

12. MOMBEJA AREA—LISTWAENITES

Sample No. Co Cr Cu Ni Zn

MJB01 37.0 380 44.0 880 9

MJB02A 35.0 220 17.0 620 6

MJB05 12.0 120 16.0 160 14

MJB07 13.0 1 53.0 32 27

MJB08 5.9 26 83.0 18 9

MJB09 7.6 32 29.0 31 18

MJB10 6.3 35 5.6 29 14

MJB11 13.0 19 1.1 49 28

MJB13 29.0 320 26.0 400 52

MJB14 24.0 340 6.6 440 18

MJB15 37.0 410 6.9 830 10

MJB16 12.0 330 14.0 160 21

MJB19 28.0 210 15.0 310 11

MJB22 48.0 81 130.0 530 9

MJB24 35.0 240 18.0 750 10

MJB25 43.0 210 40.0 660 20

MBJ26 52.0 180 18.0 1200 10

MJB27 18.0 42 45.0 55 21

MJB28 11.0 58 14.0 36 23

MJB30 26.0 190 1.0 780 8

MJB31 43.0 180 18.0 590 10

MJB32 4.2 81 4.9 47 1

MJB34 16.0 240 18.0 240 7

MJB35 10.0 180 19.0 130 11

MJB36 24.0 42 2.1 43 24

MJB37 15.0 58 2.4 31 14

MJB39 30.0 130 3.8 570 9

MJB41 29.0 45 1.4 680 5

MJB43 27.0 180 25.0 550 15

MJB45 44.0 270 3.7 940 11

MJB47 45.0 19 16.0 920 13

APPENDIX
40 RARE EARTH ELEMENTS AND GOLD DISTRIBUTIONS IN THE PORTUGESE PYRITE BELT

13. SERRA BRANCA AREA—OUTCROPS AND DRILL CORE SAMPLES

Sample No. Ag As Au Cu Mo Pb Zn

P8SB01 N0.025 11.0 N0.002 2.4 N1.0 6.6 43

P8SB02 N0.025 30.0 N0.002 N1.0 N1.0 17.0 40

P8SB03 N0.025 8.2 N0.002 2.2 N1.0 15.0 91

P8SB04 N0.025 N1.0 N0.002 380.0 N1.0 190.0 71

P8SB05 N0.025 4.1 N0.002 2.3 N1.0 35.0 71

P8SB06 N0.025 8.1 N0.002 1.3 N1.0 6.6 64

P8SB07 N0.025 9.9 N0.002 N1.0 N1.0 6.3 36

P8SB09 N0.025 220.0 N0.002 3.6 N1.0 5.9 54

P8SB10 N0.025 4.3 N0.002 1.9 N1.0 7.1 26

P8SB11 N0.025 N1.0 N0.002 4.2 N1.0 11.0 9

P8SB12 N0.025 N1.0 N0.002 2.5 N1.0 11.0 5

P8SB13 N0.025 N1.0 N0.002 2.0 N1.0 N1.0 1

P8SB14 N0.025 N1.0 N0.002 2.3 N1.0 6.2 18

P8SB15 N0.025 3.2 N0.002 2.6 N1.0 7.4 8

P8SB16 N0.025 3.4 N0.002 2.7 N1.0 11.0 25

P8SB17 N0.025 4.2 0.004 2.5 N1.0 8.3 20

P8SB18 0.520 N1.0 N0.002 2.2 N1.0 N1.0 5

P8SB19 0.490 N1.0 N0.002 1.3 N1.0 N1.0 7

P8SB20 N0.025 3.2 N0.002 1.5 N1.0 7.2 12

P8SB20 N0.025 4.4 N0.002 5.0 N1.0 14.0 23

P8SB21 N0.025 3.7 N0.002 91.0 N1.0 11.0 10

P8SB22 N0.025 3.3 N0.002 1.6 N1.0 5.7 37

P8SB23 N0.025 4.6 N0.002 18.0 N1.0 11.0 36

P8SB24 N0.025 N1.0 N0.002 5.6 N1.0 11.0 66

P8SB25 N0.025 N1.0 N0.002 130.0 4.0 N1.0 15

P8SB26 N0.025 27.0 N0.002 29.0 N1.0 24.0 30

P8SB27 N0.025 6.1 N0.002 2.8 N1.0 5.1 12

P8SB28 N0.025 N1.0 N0.002 2.8 N1.0 N1.0 3

P8SB29 N0.025 N1.0 N0.002 1.6 N1.0 N1.0 5

P8SB30 N0.025 N1.0 N0.002 2.8 N1.0 N1.0 4

P8SB32 N0.025 34.0 N0.002 1.0 4.8 N1.0 6

P8SB33 N0.025 37.0 N0.002 14.0 4.1 N1.0 10

P8SB34 N0.025 14.0 L0.002 9.5 13.0 6.8 6

P8SB35 N0.025 33.0 N0.002 3.4 3.5 N1.0 5

P8SB36 N0.025 8.4 N0.002 2.6 N1.0 N1.0 3

P8SB37 N0.025 9.1 N0.002 2.7 1.7 N1.0 3

P8SB38 N0.025 N1.0 N0.002 3.0 N1.0 N1.0 16

SB0701 N0.025 N1.0 N0.002 29.0 N1.0 9.2 63

SB0702 N0.025 N1.0 N0.002 15.0 N1.0 N1.0 18

SB0703 N0.025 N1.0 N0.002 17.0 N1.0 8.2 62

SB0704 N0.025 N1.0 N0.002 11.0 N1.0 12.0 37

SB0705 N0.025 N1.0 N0.002 11.0 N1.0 20.0 48

SB0706 N0.025 N1.0 N0.002 12.0 N1.0 11.0 51

SB0707 N0.025 N1.0 L0.002 57.0 N1.0 6.6 60

SB0708 N0.025 51.0 0.020 80.0 N1.0 28.0 19

SB0708A N0.025 42.0 0.010 66.0 N1.0 10.0 17

SB0709 N0.025 N1.0 L0.002 2.6 N1.0 8.1 40

SB0710 N0.025 3.0 N0.002 15.0 N1.0 33.0 66
2

OB

QV

BX

 Quartz veins, locally contains carbonate minerals, 

pyrite and locally other sulfide minerals

 Breccia formed primarily in or near fault zones, 

commonly contains quartz and ankerite in matrix

 Shear zones, locally sericitic and chloritic, locally 

contains sulfide minerals

 Fault or fault zone

Alteration

 Ankerite, strong

 Ankerite, moderate

 Chlorite, strong

 Chlorite, moderate

 Sericite, strong

 Sericite, moderate

 Silica, consists of intense quartz veining or silica 

flooding

Sample localities

 Sample No. and number of samples collected

 Breccia

SH

FLT

Overburden

   





























































































    





 



     

   



             









  

  



  



















    

         

    

































































































































 





















 

























































2

3

1

2

5

10

7

8

6

9

4

11

QV

QV

QV

QV

QV-BX-FLT

QV-BX-FLT

QV

QV

QV

QV

12

14 13

15

1

109.8

127.7

148.7

185.9

166.4

290.8

208.8

217.6

SL21

ALTERATION FRACTURE ZONES

SL15

ALTERATION FRACTURE ZONES

SL5

ALTERATION FRACTURE ZONES

SL26

ALTERATION FRACTURE ZONES

SL19

ALTERATION

FRACTURE ZONES

SL7

ALTERATION FRACTURE ZONES

3

D

D

E

E

4

5

C

C

A

OB

A

C

C

1

QV-BX

QV-BX

BX-QV

QV

QV

A

A

A

A

A

B

1

1

2 3

5

7

4

6

8

A

A

A

D

11

9

10

12

13

14

15

B 16

B

17

18

19 2

3

4

B 5

E

E

E

E

6

7

8

9

14

16

18

15

17

19

22

23

20

21

24

10 B

B

B

B

11

12

C

13

C

C

C

C

C

C

C

C

2

3

OB

D

D

D

D

4

1

2

3

A

A

A

4

5

6

8 7

9

11 10

12

B

B

B

A

13

14

15

16

17

18

B

B

A

A

A

A

OB

D

D

19

D

SH-FLT

BX-FLT

BX

FLT

FLT-QV

QV

QV

QV

BX-FLT

QV-BX

1

2

E

A

A

A

A

A

A

A

A

A

BX-FLT

QV

QV

QV

QV

2

3

5

4

E

D

6

7

8

E

B

B

9

10

11

12

QV

89,500

89,600

89,700

89,800

89,900

90,000

90,100

89,500

89,600

89,700

89,800

89,900

90,000

90,100

154,500 154,600 154,700 154,800 154,900 155,000 155,200

C

1

3

4

D

D

5

6

7

8

B

B

B

B

10

9

11

D 12

D

13

14

16

20

21

E

E

15

17

18

19

23

22 D

C

B

B

5

A

A

A

A

A

E

C

6

7

B

8

9

10

11

12

13

B

E

E

E

E

14

A

B

B

QV

SL24

Significant precious metal intersections

SL21

No significant precious metal intersections

SL15

No significant precious metal intersections

Samples

SL2406-SL2410 (5)

Average Au (ppb)

796

Ag (ppm)

4.76

SL7

Significant precious metal intersections

Samples

SL704 (1)

Average Au (ppb)

2700

Ag (ppm)

55.00

SL5

Significant precious metal intersections

Samples

SL514-SL524 (11)

Average Au (ppb)

505

Ag (ppm)

4.03

SL19

Significant precious metal intersections

Samples

SL1912-SL1915 (4)

Average Au (ppb)

42

Ag (ppm)

1.10

SL28

Significant precious metal intersections

Samples

SL2817-SL2821 (4)

Average Au (ppb)

450

Ag (ppm)

24.89

SL26

Significant precious metal intersections

Samples

SL2607-SL2610 (4)

Average Au (ppb)

325

Ag (ppm)

0.850

0 50 100 200 METERS

SCALE

DRILL HOLE DATA FROM THE SALGADINHO AREA, PORTUGAL

PORTUGAL

INDEX MAP OF SOUTHERN PORTUGAL SHOWING

THE LOCATION OF THE SALGADINHO AREA (X)

SPAIN

ATLANTIC

OCEAN

Grandola

Beja

Castro

Verde

Faro

LISBON

9 

38 

37 

8 

7 

X

D

   

  

 


















































































































70

70

77

SB7

P8SB6

ag

tai

ti

rb

tf

PQ

bv

sh

ft

taa

j

vt

M Mértola Formation

Borra do vinho (purple shale)

Vitric tuff

Jasper

Shale

Felsic tuff

Altered tuff and agglomerate

Agglomerate

Tuff and agglomerate, felsic to intermediate

Tuff, intermediate

Rhyolite flow

Tuffite

Normal fault—Queried where uncertain

Thrust fault—Sawteeth on upper plate.

Queried where uncertain

Strike and dip of beds

Strike and dip of foliation

Strike and dip of rock cleavage

Sample locality and number

Drill hole and number

 MAP B.—GEOLOGIC MAP SHOWING SAMPLE LOCALITIES IN THE SERRA BRANCA AREA, PORTUGAL

55

80

75

50 70 80

7

65

DDH

SE1(60)

DDH

SB7(90)

P8SB1-3

P8SB33P8SB38

P8SB31

Cerro Bronco

P8SB30

P8SB29

P8SB27

P8SB5 P8SB4

P8SB7

P8SB20

P8SB21

P8SB22

P8SB24

P8SB23

P8SB25

P8SB26

P8SB6 P8SB8

P8SB9-19

P8SB28

P8SB34-37

P8SB32

70 70

70

62

77

80

71

80 71

69

68

82

80

80

52

67

70

58

tf

ag

ft

ft

ft

vt

ft

ft

taa

M

M

M

bv

bv

sh

sh

vt ft

ft

M

M

M

taa

taa(?)

PQ

PQ

PQ

PQ

PQ

PQ

PQ

rb

tai

tai

ti j

vt

vt

ft

sh

bv

bv

ft

ft

ft

bv

vt

?

?

?

?

?

?

?

?

?

?

?

?

?

?

?

?

?

?

?

?

?

?

?

?

?

?

?

?

0 0.5 1 KILOMETER

SCALE 1:5,000

?

?

RIO

GUADIANA

B

B'

A

A'

Monte do Vale Covo

Corte Gafo Highway

80,000

81,000

240,000 241,000 242,000

EXPLANATION

PORTUGAL

INDEX MAP OF SOUTHERN PORTUGAL SHOWING

THE LOCATION OF THE SERRA BRANCA AREA (X)

SPAIN

ATLANTIC

OCEAN

Grandola

Beja

Castro

Verde

Faro

LISBON

9 

38 

37 

8 

7 

X

PORTUGAL

SPAIN

ATLANTIC

OCEAN

Grandola

Beja

Castro

Verde

Faro

LISBON

9 

38 

37 

8 

7 

X

Xg

Xg

Xg

Xg

Xg

Xg

Xg

Xg Xg

Xg

Xg

Xg

Xg

RESERVOIR

Xg

Xg

Xg

70

70

60

60

70

65

55

50

55

75

70

20

85

75

45 70

70

70

70

70

55

75

55

50

85

70

75

80

65

55

60

P7SD25

P7SD24

MP3

MSD1

58,000

56,000

54,000

-222,000

P7SD21

P7SD23

P7SD22

P7SD12

P7SD20

P8SD1

P7SD16

P7SD15

P8SD37

P8SD38

P8SD39

P8SD40

P8SD41

P8SD42

P8SD43

P7SD1

P7SD14

P8SD47

P8SD44

P8SD1

P8SD9

P7SD7

P7SD8

P7SD10

P8SD29

14

P7SD9

P8SD19 P8SD10

P8SD46

8 7

P7SD19

P7SD18

P7SD26

sl

sl

sl

sl

sl

sl

sl

sl

sl sl

sl

sl

sl

sl

sl

sl

sl

sl

sl

sl

sl

sl sl

sl

sl

sl

sl

tf

tf

tf

tf

tf

tf

tf

tf

tf

tf

tf

tf

tf

tf

tf

tf

tf

tf

tf

tf

tf

tf

tf

tf

tf

tf

tf

tf

tf

av

av

av

av

av

av

av

av

av

av

av

av av

av av

av

av

av

av

av

av

av

av

av

av

av

av

av av

av

av

Xg

Xg

sl

sl

tfa

tfa

tf

tf

av

MS

av

av

av

sl

sl

MINE

RUBBLE

MINE

RUBBLE

MINE

RUBBLE

MINE

RUBBLE

MINE

RUBBLE

OPEN

PIT

MINE 6

4 5

3 2

28

27

26

25

45 24

22

23

21

20

13

12 11

15 18

17

35, 36

33, 34

31, 32

30

Xg

sl

tfa

tf

av

EXPLANATION 

Shale, quartzwacke, and siliceous shale

Felsic tuff, chert, vitric tuff, and shale

Felsic to intermediate tuff and agglomerate

Felsic pyroclastic and flow rocks

Spilitic basalt and andesitic basalt

Rock sample site

Drill hole site

Contact

Fault

Strike and dip

Outline of mine rubble

Repressa and

Sabina Formations,

undivided

Volcanic-Siliceous

Complex

0 0.5 1 KILOMETER

SCALE 1:10,000

Phyllite-Quartzite Group—Pyrite (iron hydroxide 

 rich) zones

Modified by R.L. Earhart from unpublished maps

by Delfim de Carvalho, Serviços Geologicos de Portugal  ́

INDEX MAP OF SOUTHERN PORTUGAL SHOWING

THE LOCATION OF THE SAO DOMINGOS AREA (X) ~

MINAS DE

SAO DOMINGOS ~

tai

ft

ti

bv

vt

Tuff, agglomeratic, felsic to intermediate

Tuff, intermediate

Tuff, felsic 

Borra do Vinho purple shale 

Vitric tuff 

sh

PQ

Black to green-gray shale 

 Quartzite Group phyllite 

Fault 

Drill core sample and number 

Drill hole 

EXPLANATION

Calcite-quartz veinlet with rhodochrosite and vuggy

 pyrite, hosted in coarse agglomerate, 12 mm thick

Quartz vein, minor calcite, agglomerate inclusions, 

 32 cm thick

Andesitic agglomerate, chloritic, trace pyrite

Dacite-keratophyre, round quartz phenocrysts, 

 disseminated pyrite

Same as SB7-4

Dacite-keratophyre, round quartz phenocrysts, 

 trace pyrite

Dacite-keratophyre, very chloritic, minor pyrite

Highly silicified pyroclastic rock, 70 percent pyrite

Dacite-keratophyre, highly chloritic, albitic, 

 calcite vugs, pyrite

Dacite-keratophyre, sheared, with calcite and pyrite

Sample

No.

Sample

Core sample descriptions No.

tai

ft

ti

vt bv

sh

PQ

SB7

tai

ft

ft

vt SE7

1

2

3

4

5

6

7

8

10

9

A A'

–200

–150

–100

–150

–0

–50

–100

–150

METERS

1

Core sample descriptions

SB7

SB7-1

SB7-2

SB7-3

SB7-4

SB7-5

SB7-6

SB7-7

SB7-8

SB7-9

SB7-10

B B'

–200

–150

–100

–50

0

50

100

150

METERS

PQ

ft

tf

ag

rb

rb

ft

taa

Rock samples

P8SB6–P8SB26

ft

ft

ft

vt

sh

bv

M

PQ

M Mertola Formation

Borra do vinho (purple shale)

EXPLANATION

ft

sh

taa

bv

vt Vitric tuff 

Shale 

 Felsic tuff

Altered tuff and agglomerate

rb

ag

tf

PQ

Flow-banded rhyolite 

Agglomerate

Tuffite

Phyllite-Quartzite Group

Contact

Fault—Arrows show direction 

 of movement

Sample

No.

 DESCRIPTION

Felsic tuff, argillically altered, sheared, greenish mica

Same as P8SB6

Same as P8SB6

Felsic tuff, sheared, greenish mica, Fe oxides minor chlorite

Same as P8SB9

Felsic tuff, with greenish mica, Fe oxides, in veinlets

Green-altered tuff, quartz phenocrysts, minor pyrite

Green-altered tuff, pink feldspar veinlets

Sub-vitreous tuff, quartz phenocrysts

Green-altered tuff, quartz and albite phenocrysts

Silicified green-altered tuff, chlorite stringers

Agglomerate, weakly silicified, weekly chloritic

Green-altered tuff

Banded vitric tuff, trace pyrite

Green-altered tuff, highly sheared

Felsite

Ferruginous quartz from fault zone

Quartz keratophyre

Quartz keratophyre

Sheared, ferruginous tuff from fault zone

Flow-banded rhyolite

Laminated tuffite

Sample locality

FLT Fault or fault zone

Sample

No. Core sample descriptions Core sample descriptions

 ́

P8SB6

P8SB7

P8SB7

P8SB8

P8SB9

P8SB10

P8SB11

P8SB12

P8SB13

P8SB14

P8SB15

P8SB16

P8SB17

P8SB18

P8SB19

P8SB20

P8SB21

P8SB22

P8SB23

P8SB24

P8SB25

P8SB26

 MAP A.—GENERALIZED GEOLOGIC MAP OF THE SAO DOMINGOS AREA SHOWING SAMPLE LOCALITIES, PORTUGAL ~