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Introduction

SEDIMENTARY rock-hosted strata-bound copper deposits are widespread in the Kangdian region of southwest China, wherethey are known as “Dongchuan-type” copper deposits (Li et al.,1953; Gong and Wang, 1981; Sun et al., 1991; Chen and Ran,1992; Gong et al., 1996; Zhao, 2010). Although these copperdeposits have been mined for decades and extensively studied,they remain poorly known outside of China. The deposits con-tain disseminated and veinlet copper sulfides along a regionalredox boundary above weakly metamorphosed hematitic

sandstones and siltstones within a weakly metamorphosed,dolostone sequence and a stratigraphically higher carbonaceousslate of latest Paleoproterozoic to early Mesoproterozoic age.

The Dongchuan-type copper deposits share many charac-teristics with other sedimentary rock-hosted stratiform cop-per deposits (Hitzman et al., 2005). This class of depositscomprises disseminated to veinlet copper and copper-ironsulfides in siliciclastic or dolomitic sedimentary rocks. Sul-fides conform closely, but usually not exactly, with the strati-fication of the host rocks. These deposits commonly occur inbasins that contain a basal sequence of continental red beds

overlain by marine or lacustrine rocks with evaporites(Brown, 1997; Hitzman et al., 2005). The Dongchuan-typecopper deposits of South China are remarkably similar to car-bonate-hosted stratiform deposits within the Mines Series of the Central African Copperbelt.

The genesis of the Dongchuan-type copper deposits haslong been debated and several genetic models have beenproposed. Meng et al. (1948) and Li et al. (1953) invoked anepigenetic model in which copper sulfides were precipitatedfrom magmatic-hydrothermal fluids. Gong and Wang (1981)

and Gong et al. (1996) advocated a synsedimentary, exhalativemodel based on the strata-bound nature of orebodies. Acomposite diagenetic model was proposed in the 1980s (Ran,1983, 1989a; Hua, 1990) wherein metals were derived fromcontinental red beds and precipitated in reduced sulfur-bearingdolostones during diagenetic or late metamorphic events.

The Tangdan deposit, the largest in the Kangdian region, was selected for a geologic and geochemical study to betterunderstand these strata-bound copper deposits.

Methodology

The Tangdan deposit was investigated through geologicmapping and logging of drill core. Samples from the deposit

Late Paleoproterozoic to Early Mesoproterozoic Tangdan Sedimentary Rock-HostedStrata-bound Copper Deposit, Yunnan Province, Southwest China

X IN-FU ZHAO,1 MEI-FU ZHOU,1,† MURRAY W. HITZMAN,2 JIAN-W EI LI,3 MITCHELL BENNETT,2 COREY MEIGHAN,2

AND ERIC ANDERSON2

1 Department of Earth Sciences, University of Hong Kong, Hong Kong SAR, China

2 Department of Geology and Geological Engineering, Colorado School of Mines, Golden, Colorado 80401

3 State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, China

Abstract

Sedimentary rock-hosted strata-bound copper deposits are widespread in the Kangdian region of the Cen-tral Yunnan and southern Sichuan provinces, southwest China. The deposits occur within weakly metamor-phosed rocks of the late Paleoproterozoic to early Mesoproterozoic Dongchuan Group and are spatially asso-ciated with discordant breccia bodies that are interpreted as having formed from salt diapirs. The Tangdandeposit, the largest in the region, consists of stratiform and discordant orebodies predominantly hosted indolostones immediately above hematitic sandstones and siltstones and in black shales above the dolostones.

Host rocks for the deposit display a complex paragenetic sequence of alteration and mineralization. Early sodic alteration resulted in the growth of both albite and ferroan dolomite. Later potassic alteration resulted inthe precipitation of potassium feldspar and locally biotite in argillaceous layers. Sulfide mineralization was tem-porally and spatially associated with silicification that postdated both sodic and potassic alteration. Textures sug-gest that silicification may have preferentially affected evaporite minerals in the dolostones.

Copper sulfides form bedding-parallel disseminations, veinlets and, to a lesser extent, stockworks. Coppersulfides are dominated by chalcopyrite with lesser bornite and chalcocite. Hypogene chalcopyrite and bornitefrom the Tangdan deposit have δ34S values that range from −12.7 to +9.3‰ and cluster between −3 to +5‰.The values suggest derivation from Mesoproterozoic marine sulfates. The dolostone host rocks have relatively homogeneous C and O isotope values ranging from 0.2 to 1.3‰ δ13C V-PDB and from 19.1 to 22.4‰ δ18O V-SNOW .Carbonate minerals in quartz sulfide veins display both a trend toward lighter oxygen isotope values and a trendto significantly lighter carbon isotope values. The light carbon isotope values suggest involvement of organiccarbon in the mineralizing process.

Alteration and mineralization at Tangdan probably occurred via interaction of oxidized saline brines derivedfrom the underlying red-bed sequence with partially to wholly lithified dolostones. Sulfide precipitation waslikely due to both redox reactions and mineralizing fluid pH changes resulting from dolomite and sulfate dis-

solution. The styles of alteration and mineralization at the Tangdan deposit are similar to those observed in theCentral African Copperbelt, particularly the dolostone-hosted orebodies in the Mines Series of the Democra-tic Republic of Congo.

† Corresponding author: e-mail, [email protected]

©2012 Society of Economic Geologists, Inc.Economic Geology, v. 107, pp. 357–375

Submitted: March 20, 2011 Accepted: September 17, 2011



were analyzed utilizing standard petrographic techniques andQEMSCAN® analysis. Petrographic studies focused on delin-eating the paragenetic sequence of alteration and mineraliza-tion. Sulfur isotope analyses were undertaken on sulfides andcarbon and oxygen analyses were performed on samples of host carbonate rocks and sulfide-bearing carbonate veins toconstrain the geochemistry of the mineralizing system.

QEMSCAN® analysis

Petrographic analysis included utilization of the QEM-SCAN® instrument at the Colorado School of Mines. QEM-SCAN® is an automated quantitative mineralogy tool that uti-lizes an electron-beam platform with four energy dispersive

X-ray spectrometers to produce false-colored mineral mapsfrom backscatter electron signals and EDS (energy dispersivespectrometer) spectra. The system contains proprietary soft-

ware that allows automated data acquisition and interactivedata analysis.

Carbon and oxygen isotopes

Both host-rock dolostone and carbonate minerals from veins were collected for analysis of carbon and oxygen isotopes. Sam-ples analyzed in China (indicated as HKU in Table 1) werecrushed to 40 to 60 mesh and the carbonate minerals (calcite,dolomite, and siderite) were handpicked under a binocularmicroscope. The analyses were performed on a Finnigan MAT251EX mass spectrometer at the Stable Isotope Laboratory, In-stitute of Mineral Resources, Chinese Academy of GeologicalSciences, Beijing. Carbon dioxide was extracted by reaction

with 100% phosphoric acid at 25° and 50°C, respectively. Theprecision from in-house and international standards is ~0.2‰.

For the samples analyzed at Colorado School of Mines(CSM), approximately 90 ug of carbonate sample material de-rived from microdrilling was weighed into individual sample

vials. Samples were quantitatively acidified in vacuo in an on-line autosampler with 100% orthophosphoric acid at 90°C.After cryogenic purification of the generated carbon dioxide,the gas was analyzed simultaneously for stable carbon andoxygen isotopes in a GV Instruments Isoprime stable isotopemass spectrometer using traditional dual-inlet techniques.Laboratory standard reference gas was calibrated against alaboratory working calcium carbonate powder derived fromthe Colorado Yule Marble. The composition of Colorado YuleMarble has been calibrated against NBS-18 and NBS-19 stan-dard reference materials obtained from the National Instituteof Standards and Technology. Precision determined throughrepeated analyses of Colorado Yule Marble and blind dupli-

cate analysis of samples is 0.05‰ for carbon and 0.08‰ foroxygen. All data are corrected for the contribution of 17Ousing the correction factors from Craig (1957). All carbon andoxygen isotope ratios are presented in δ notation relative toPDB Peedee belemnite (PDB) and standard mean ocean

water (SMOW) standards, respectively.

Sulfur isotope

Sulfide mineral separates (bornite, chalcopyrite, chalcocite) were analyzed for sulfur isotope compositions. At HKU sam-ples were crushed to 40 to 60 mesh and the sulfide mineral sep-arates were handpicked under a binocular microscope. Thesulfur isotopes were analyzed at the Stable Isotope Laboratory,

Institute of Mineral Resources, Chinese Academy of GeologicalSciences, Beijing. The sulfide separates were converted to sul-fur dioxide using V 2O5 as an oxidant, and the isotopic composi-tions were measured with a Finnigan MAT 252 mass spectrom-eter. At the Colorado School of Mines, approximately 25 to 100 µg (weight dependent on the mineral analyzed) of samplesderived from microdrilling was combusted in a Eurovector

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TABLE 1. Carbon and Oxygen Isotopes fromKangdian Sedimentary Rock-Hosted Cu Deposits

Sample Mineral 18OSMOW (‰) 13CPDB (‰) Reference1

Host-rock dolostone (Luoxue Formation) at TangdanDC-32 Dolomite 22.4 0.8 This study (HKU)DC-33 Dolomite 22.0 0.6 This study (HKU)DC-41 Dolomite 20.3 1.1 This study (HKU)Tang 1b2 Dolomite 20.6 0.3 This study (CSM)Tang 8b2 Dolomite 20.6 0.6 This study (CSM)

Host-rock dolostone (Luoxue Formation) at other Dongchuan depositsLX13A Dolomite 21.0 1.0 Hua et al. (1988)LX13B Dolomite 21.1 1.1 Hua et al. (1988)L32A Dolomite 21.9 1.3 Hua et al. (1988)L32B Dolomite 22.0 1.3 Hua et al. (1988)Y18 Dolomite 19.1 0.8 Hua et al. (1988)Y33 Dolomite 19.8 0.9 Hua et al. (1988)Y34A Dolomite 19.2 0.8 Hua et al. (1988)Y34B Dolomite 19.2 0.8 Hua et al. (1988)Y13 Dolomite 19.5 0.2 Hua (1990)Y31 Dolomite 20.0 0.6 Hua (1990)Y32 Dolomite 19.4 0.7 Hua (1990)Y35 Dolomite 19.7 1.1 Hua (1990)

Y49 Dolomite 19.7 0.5 Hua (1990)

Unmineralized dolostone of Luoxue Formation (Tongchang Section)L6 Dolomite 19.3 0.6 This study (CSM)L8a Dolomite 19.2 1.0 This study (CSM)

Carbonate-sulfide veins cutting Luoxue Formation at TangdanDC-8 Calcite 13.4 –0.4 This study (HKU)DC-26 Calcite 13.1 –0.2 This study (HKU)Tang 1b1 Calcite 20.4 0.3 This study (CSM)Tang 6 Calcite 15.3 0.3 This study (CSM)Tang 8b Calcite 19.8 0.8 This study (CSM)Lou 2b Ankerite 7.4 –3.5 This study (CSM)

Carbonate-sulfide veins cutting Luoxue Formation at otherDongchuan deposit

YN07-400 Siderite 17.2 –5.4 This study (HKU)YN07-401 Siderite 17.3 –5.4 This study (HKU)LX04A Calcite 10.0 0.3 Hua et al. (1988)LX04B Calcite 9.9 0.3 Hua et al. (1988)LX35 Calcite 14.1 1.7 Hua et al. (1988)LX41 Calcite 17.4 0.2 Hua et al. (1988)LX53 Calcite 14.2 –0.9 Hua et al. (1988)LX70 Calcite 17.3 –5.3 Hua et al. (1988)

Dolomite-sulfide veins in the E’touchang Formation at TangdanDC-49 Dolomite 19.1 –8.5 This study (HKU)Tao 2 Dolomite 16.8 –1.9 This study (CSM)

Carbonaceous slate of E’touchang Formation at TangdanDC-42 Bulk rock –9.5 This study (HKU)DC-43 Bulk rock –25.9 This study (HKU)

LC-13 Bulk rock –26.9 This study (HKU)LC-14 Bulk rock –27.0 This study (HKU)

1 HKU = samples analyzed in China, CSM = samples analyzed at the Col-orado School of Mines



3000 elemental analyzer, yielding sulfur dioxide that was deliv-ered to an Isoprime mass spectrometer using continuous-flow techniques, with helium as the carrier gas. Repeat analysis of alab working standard (Colorado School of Mines Barium Sul-fate) yielded a precision of 0.3‰. The isotopic data are re-ported using the δ notation in units of per mil, relative to theCañón Diablo Troilite (CDT) standard (Beaudoin et al., 1994)

Geologic Background

South China is bounded by the Tibetan Plateau to the westand is separated by the Red River Fault from the Indochinablock to the south (Fig. 1). It comprises the Yangtze block tothe northwest, which hosts the sedimentary rock-hostedstrata-bound copper deposits, and the Cathaysia block to thesoutheast (Fig. 1A); these blocks were probably amalgamated

TANGDAN SEDIMENTARY ROCK-HOSTED STRATA-BOUND Cu DEPOSIT, YUNNAN PROVINCE, CHINA 359

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L u z

h i j i a

n g

f a u

l t z o n

e

0 20km

N

J i n s h a

R i v

e r

Huili

Dongchuan

E’shan

Yuanjiang

Yimen

R e d

R i v

e r F a u l t

Yuanmou

102 E

26 N

24 N

Tangdan

Gabbro

Diorite

Granite

Breccia body

Fault

Inferred fault

Cu deposit

Others

B)

Kunming

746 13 Ma[Zhou et al.,2002]

819 8 Ma[Li, X-.H. et al.,2003a]

746 10 Ma[Zhao and Zhou,2007]

Sichuan Province

Yunnan Prov ince

Q i n l i n g

D a b i e

S u l u

North ChinaCraton

Yangtze Block

A)

TibeteanPlateau

Guangzhou

Cathaysia Block

0

Fig.1b

500kmN

Neoproterozoic intrusions

Fig.4

Dahongshan Group

Dongchuan Group

Kunyang Group

Paleoproterozoic andMeso-proterozoic strata

Neoproterozoic andyounger rocks

Tongchang

Yinachang

FIG. 1. A. Simplified tectonic map showing thestudy area in the Yangtze block. B. Geologic mapshowing the locations of Paleoproterozoic and Meso-proterozoic strata and Neoproterozoic intrusions inthe Kangdian region, SW China (modified from Wuet al., 1990). The map also shows the distribution of sedimentary rock-hosted strata-bound Cu depositsincluding Tangdan.



at approximately 0.83 Ga (Wang et al., 2007; Zhou et al.,2009; Zhao et al., 2011).

Paleoproterozoic and Mesoproterozoic strata of theYangtze block, including the Dahongshan, Dongchuan, andKunyang Groups, are widely distributed in the Kangdianregion (Wu et al., 1990; Greentree et al., 2006; Greentree andLi, 2008; Zhao et al., 2010). The area containing these se-

quences is bounded by the Luzhijiang Fault to the west andcut by a series of subordinate NNE-trending faults (Fig. 1B).The oldest rocks in the Kangdian region belong to theDahongshan Group (Fig. 1B), which consists of an amphibo-lite-facies metamorphosed volcano-sedimentary sequence

that hosts the Dahongshan iron oxide-copper-gold (IOCG)deposits (Zhao and Zhou, 2011). A volcanic unit within theDahongshan Group has a SHRIMP zircon U-Pb age of 1675± 8 Ma (Greentree and Li, 2008).

The Dongchuan Group includes the Yinmin, Luoxue, E’touchang, and Luzhijiang Formations, all of which containcopper mineralized zones (Sun et al., 1991; Gong et al., 1996;

Fig. 2). The contact between the Dahongshan and DongchuanGroups is not exposed. The two sequences may either be lat-eral equivalents (Zhao et al., 2010) or the Dongchuan Groupmay overlie the Dahongshan Group (Wu et al., 1990). Rocksof the Dongchuan Group are distributed discontinuously in a

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si si si si

L u z h i j i a n g F o

r m a t i o n

1 1 6 2 ~ 2 0

3 1 m

Y i n m i n F o r m a t i o n

c c c

c c c

si si si si

L u o x u e F o r m a t i o n

E t o u c h

a n g F o r m a t i o n

c c c

c c c

Lithological logFormations Lithology

8 6 2 ~ 1 6 6 0 m

1 3 7 ~ 2 0 5 m

4 8 4 ~ 7 8 6 m

c si c si

c si c si

c si c si

c

c c cc

Transition zone of intercalated siltstoneand dolostone

Purplish-red rhythmically siltstone andargillaceous siltstone, now slate, withlocal tuff

Sandstone and siltstone

Conglomerate at the base

White, thick-layered dolostone withabundant stromatolites

Bluish-grey, thick-layered dolostone,with minor chert interbeds

Argillaceous dolostone

Black shale, slate now, with minorlimestone interbeds

Interbedded siltstone and mudstonemetamorphosed to slate now;tuff locally present

Carbonaceous slate

Greyish, thick-layered dolostone,locally contains stromatolites

Medium-thick, layered dolostonewith chert and mudstone interbeds

Stratigraphic extent of sulfides

FIG. 2. Stratigraphy of the DongchuanGroup based on measured cross sectionsof Wu et al. (1990) and mapping from thisstudy.



narrow belt more than 300 km long and less than 35 km wide(Fig. 1B). The rocks are weakly deformed and were subjectedto lowest greenschist grade metamorphism (Wu et al., 1990).

The Yinmin Formation is primarily composed of purplish-red, hematitic meta-arenite (sandstone and siltstone) and slate

(Fig. 3A, B) with minor meta-tuffaceous beds. It is consideredto be the oldest continental red-bed sequence in the Yangtzeblock (Wu et al., 1990; Hua, 1993). The preserved thicknessof the Yinmin Formation in the region ranges from less than100 to more than 1,000 m. Pseudomorphs of halite and


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A B

C D

F

Yinmin Fm.Luoxue Fm.

5 m 20 cm

3 cm 10 cm

20 cm2 cm

E F

FIG. 3. Images of rocks in the Dongchuan Group. A. Steeply dipping conformable contact between metasandstone of the Yinmin Formation and dolostone of the Luoxue Formation in the Dongchuan area. The boundary is marked by aban-doned adits. B. Purplish-red siltstones of the Yinmin Formation at the Tangdan mine. The insert photo is a scan of a thin sec-tion from these rocks showing fluidization structures. C. Algally banded dolostone of the Luoxue Formation from the Tang-dan deposit, showing typical pale-buff color of weathered rocks. The gray bands that parallel and crosscut bedding aresilicified zones. D. Stromatolite structures in dolostones from the lower portion of the Luoxue Formation in the Dongchuandistrict. E. Laminated carbonaceous slate of the lower E’touchang Formation from the Taoyuan Mine at Tangdan with minordisseminated pyrite and chalcopyrite and bedding parallel white nodules with quartz and chalcopyrite. F. Yinmin Breccia with various colored, angular to rounded siltstone and dolostone clasts in a fine-grained matrix of quartz, albite, and carbon-ate minerals. This breccia has been interpreted as the product of halokinesis (Ruan et al., 1991). The breccia is from the Yin-min Mine, approximately 20 km northwest of Tangdan (Fig. 4).



anhydrite in the upper Yinmin Formation indicate the formerpresence of evaporites (Hua, 1993; Xiong et al., 1993). Theuppermost portion of the Yinmin Formation consists of intercalated slate and weakly metamorphosed dolostone. Thelower Yinmin Formation was probably deposited in a fluvialand/or alluvial fan environment, whereas the uppermost por-tion of the Formation records deposition in a restricted shal-

low marine setting. The Yinmin Formation is generally viewedas the source rock for the strata-bound copper deposits in theoverlying sedimentary rocks (Ran, 1983, 1989a; Hua, 1990).

The Luoxue Formation conformably overlies the YinminFormation and is composed predominantly of thick-bedded,

white-gray dolostone and weakly argillaceous to arenaceousdolostone (Fig. 3A, C, D). The contact between the Yinminand Luoxue Formations is generally sharp, suggesting a rapidmarine transgression. Some areas, including the TangdanMine region, appear to contain a transitional zone at the baseof the Luoxue Formation up to approximately 10 m thick of interbedded dolostones and siltstones. The lower LuoxueFormation contains abundant stromatolites, includinglamellar, cylindrical, and spherical types (Fig. 3D; Ran,1989b). Luoxue Formation dolostones are buff to pale gray incolor, though some zones contain dark (carbonaceous) band-ing along algal layers and argillaceous partings. The upperportions of the Luoxue Formation are cherty in some areas.Regionally, the Luoxue Formation ranges in thickness fromapproximately 100 to over 500 m; the unit is approximately 140 to 205 m thick at Tangdan. Luoxue Formation dolostonesgenerally form outcrops, as opposed to the recessive weath-ering siltstones of the overlying and underlying units.

The E’touchang Formation appears to conformably overlierocks of the Luoxue Formation. The lowermost E’touchangFormation contains shales and siltstones, now largely slates,and rare tuff beds, which pass upward into mixed less meta-

morphosed siltstone, dolostone, and mudstone. At Tangdan,

the basal E’touchang Formation is highly carbonaceous (Fig.3E). The rapid transition from shallow marine dolostones inthe Luoxue Formation to locally highly carbonaceous slates of the E’touchang Formation suggests this contact represents amajor, basin-wide transgressive event. The uppermost E’-touchang Formation consists of thick-bedded green shalesand siltstones. The overall thickness of the E’touchang For-

mation is approximately 1,660 m.The Luzhijiang Formation, which apparently conformably

overlies the E’touchang Formation, grades upward from car-bonaceous dolostones interbedded with siltstones to shallow marine, massive, locally ferruginous stromatolitic dolostones(Wu et al., 1990). The Luzhijiang Formation contains minorcopper deposits and a number of small zinc-lead deposits. It isoverlain by rocks of the Kunyang Group consisting largely of shales and arkosic sandstones of probable fluvial origin. TheDongchuan and Kunyang Groups are in fault contactthroughout the area (Fig. 1B).

Detrital zircons from the Yinmin Formation have U-Pbages of ~3.5 to ~1.78 Ga (Zhao et al., 2010). Tuffaceous rocksin the Yinmin and E’touchang Formations have zircon U-Pbages of 1742 ± 13 and 1503 ± 17 Ma, respectively (Sun et al.,2009; Zhao et al., 2010). These ages indicate that theDongchuan Group was deposited during the latestPaleoproterozoic to early Mesoproterozoic (~1.7−~1.5 Ga).The large age span indicated by the available data suggeststhat significant disconformities may exist within theDongchuan Group. Samples from a tuff in the overlying Kun-

yang Group have yielded SHRIMP zircon U-Pb ages of 1032± 9 and 995 ± 15 Ma (Greentree et al., 2006; Zhang et al.,2007), suggesting that this sequence unconformably overliesthe Dongchuan Group sedimentary rocks.

The Yinmin, Luoxue, E’touchang, and portions of Luzhi- jiang Formations of the Dongchuan Group are cut by breccia

bodies (Figs. 1B, 4), known as the Yinmin Breccia (Wu et al.,

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0 5 kmN

Jinsha River

Yinmin

Luoxue

Tangdan

X i a o j i a n g f a u l t

102 30 E

26 20 N

Lanniping

Kunyang Gr.

Dongchuan Gr.

Luexue Fm.

Gabbro

Yinmin Breccia

Fault

Inferred fault

Cu deposit

Fig.5

FIG. 4. Simplified geologic map showing the distribution of copper deposits in the Dongchuan ore district (modifiedfrom Gong et al., 1996). Note their spatial association with the Yinmin Breccia.



1990). These breccia bodies range from a few meters toseveral kilometers in diameter. The breccias are both clastand matrix supported and contain rounded to angular clasts of Yinmin Formation siltstones and sandstones (Fig. 3F) withless common clasts from the Luoxue and E’touchang Forma-tions and rare mafic igneous rock that range in size from<1cm to a few meters or tens of meters in diameter. The brec-

cia matrix consists of fine-grained dolomite, ankerite, albite,quartz, potassium feldspar, and biotite. Breccia contacts withsurrounding wall rocks grade over centimeters from crackle-brecciated wall rock to polylithologic breccia. The YinminBreccia is megascopically similar to breccias in the KatangaProvince of the Democratic Republic of Congo that containlarge (up to kilometer scale) mineralized clasts. The Con-golese breccias are attributed to the former presence of salt(Jackson et al., 2003). A similar genesis has been suggestedfor the Yinmin Breccia with the salt thought to have originally been present in the lower Yinmin Formation (Ruan et al.,1991). Salt tectonics may account for the occurrence of tightfolds cored by breccia (Fig. 4) observed throughout the Kang-dian region that probably represent former salt walls. Thepresence of low-angle faults at the base of the Yinmin For-mation may represent a regional plane of movement lubri-cated by salt.

Paleoproterozoic and Mesoproterozoic igneous rocks aresparse in the western Yangtze block though the mafic igneousclasts in some Yinmin Breccia indicate they must be present.Neoproterozoic intrusions with ages between ~860 and ~740Ma are widespread in the region (Zhou et al., 2002; Li, X.-H.et al., 2003). They include tonalite-trondhjemite, granite,diorite, and gabbro. These rocks have been interpreted asproducts of either subduction-related (Zhou et al., 2002; Zhaoand Zhou, 2007) or mantle plume-induced magmatism (Li,

X.-H. et al., 2003; Li, Z.X. et al., 2003).

Kangdian Sedimentary Rock-HostedStrata-Bound Copper Deposits

The Kangdian region contains numerous sedimentary rock-hosted strata-bound copper deposits hosted within rocksof the Dongchuan Group (Fig. 1B). The majority of the de-posits occur in dolostones of the Luoxue Formationimmediately above the contact with the Yinmin Formation(Sun et al., 1991; Gong et al., 1996). Individual depositscommonly extend for hundreds of meters to kilometers alongthis lithologic interface.

The Dongchuan district contains several of the largestknown examples of Dongchuan-type deposits in an approxi-

mately 30 km long belt (Fig. 4). The Luoxue Mine containsapproximately 500,000 metric tons (t) of contained copper(50 Mt @ 1% Cu). Immediately to its north and essentially part of the same orebody is the Yinmin Mine with >210,000 tof contained copper (21 Mt @ 1% Cu; Ruan et al., 1991). TheTangdan deposit contains approximately 120 Mt of 1.1% Cu(Gong et al., 1996). The Luoxue Formation, which hosts thedeposits, is weakly mineralized throughout the entire district.The deposits are spatially associated with the Yinmin Brecciaand many are cut by mafic intrusions.

The cumulative tonnage in the Dongchuan district is prob-ably in excess of 391 Mt at 1% Cu (Gong et al., 1996). Takentogether, the number of deposits of the Dongchuan type in

the Kangdian region would rank the area as the world’s thirdor fourth largest sediment-hosted strata-bound copper dis-trict after the Central African Copperbelt and the EuropeanKupferschiefer and comparable in terms of size with theDzhezkazgan district in Kazakhstan (Hitzman et al., 2005).

The Dongchuan-type copper deposits contain both strati-form and discordant styles of mineralization. Stratiform min-

eralized zones contain copper sulfides as disseminations and veinlets hosted within dolostone of the lower LuoxueFormation and less commonly in black shales of the lower-most E’touchang Formation. Discordant mineralized zonescontain copper sulfide-bearing veins along fractures, joints,and faults, either concordant to, or crosscutting, both the Lu-oxue and E’touchang Formations. In the Dongchuan district,discordant mineralized zones are estimated to account foronly 3% of the total copper reserves (Gong et al., 1996), butthese occurrences are relatively high grade, containing 1 to 10

wt % Cu. None of the Dongchuan-type deposits have signifi-cant by-product metals such as Co, Ag, Pb, or Zn.

Some of the Dongchuan-type copper deposits (e.g., theYinmin and Lanniping deposits) contain small bodies of mas-sive magnetite/hematite in the underlying Yinmin Formationor Yinmin Breccia (Sun et al., 1991; Gong et al., 1996). It isunclear whether these Fe oxide bodies, some of which arecupriferous, are genetically related to the copper deposits inthe overlying rocks; they were not investigated as part of thecurrent study. The Fe oxide bodies may represent zones of in-tense mineralizing fluid flow through the Yinmin Formation.

The majority of the known copper and iron deposits in theDongchuan Group occur in the cores of tight to faulted anti-clines and in diapiric blocks. It appears that mineralizing flu-ids utilized the Yinmin Breccia as a flow path in many areas.If the breccias were derived from salt movement, the dissolu-tion of the salt could have provided a source of high-salinity

fluids capable of leaching copper under oxidizing conditionsand precipitating copper sulfides in zones that contained re-duced sulfur.

Geology of the Tangdan Deposit

The Tangdan deposit is the largest strata-bound copperdeposit in the Kangdian region with a proven reserve of >1.29Mt Cu (Gong et al., 1996). Cobalt and germanium are locally enriched (up to hundreds of ppm) at the Tangdan deposit butdo not form economic accumulations (Gong et al., 1996). Thehost strata exposed in the mining area include the Luoxue andYinmin Formations, which are in fault contact with, or over-lain by, black shales of the E’touchang Formation (Fig. 5). A

gabbroic intrusion with a zircon U-Pb age of 1047 ± 3 Ma(Zhao, 2010) and a K-Ar age of 1059 Ma (Gong et al., 1996)cuts the E’touchang and Luoxue Formations immediately tothe northwest of the mining area (Figs. 5, 6). TheseDongchuan Group rocks are unconformably covered by Sinian (late Neoproterozoic) dolostones of the DengyingFormation to the southeast of the mine (Fig. 5).

The orebodies at Tangdan are predominantly hosted indolostones of the lower Luoxue Formation but locally ex-tend throughout the Luoxue Formation and into blackshales of the lowermost E’touchang Formation (Figs. 5−7).Minor sulfides occur in dolostones of the uppermost portionof the Yinmin Formation. Both stratiform and discordant


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mineralized zones occur in all stratigraphic positions. Sulfidesoccur as disseminations, veinlets, and to a lesser extent,stockworks (Fig. 8A-F). Disseminated sulfides generally occur along the lamina of the dolostone (Fig. 9A-E), alongstylolites, and throughout the carbonaceous slates (Fig. 8E).The ore minerals are chalcopyrite, bornite, and chalcocite

with minor pyrite, digenite, and covellite (Fig. 9B-I); sulfidesare commonly intergrown with fine- to medium-grained re-placive quartz (Fig. 9B-F).

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Sinian dolostone

Etouchang Fm

Luoxue Fm

Yinmin Fm

Cu orebodyGabbro

Fault

0 200m

N

6 0

3 6 45

5 6

4 0

Tangdan

1047 3 Ma

Fig. 6Fig. 7

FIG. 5. Geologic map of the Tangdan deposit showing the distribution of copper orebodies.

Luoxue Fm.

0.661.99

0.7512.0

0.6512.0

1.0011.0

0 100m

Elevation (m)2600

2400

2200

2000

1800

Yinmin Fm

Luoxue Fm

Gabbro

Drill core

Ore grade (wt%)

Thickness (m)

Cu orebody

Etouchang Fm

0.65

12.0

Etou chang Fm.Yinmin Fm.

FIG. 6. Geologic cross section through the Tangdan deposit (modifiedfrom Gong et al., 1996), illustrating that copper orebodies are locatedthroughout the Luoxue Formation. A fault cuts out the Luoxue Formationnear the surface and progressively cuts upsection downward. This fault is oc-cupied by a 1047 ± 3 Ma gabbro.

1552500

2300

2100

1900

Luoxue Fm.

E t o

u c

h a n g

F m

.Yinmin Fm.

Elevation (m)

Yinmin Fm

Luoxue Fm

Cu orebody

Etouchang Fm

FIG. 7. Geologic cross section of the Tangdan deposit, illustrating pref-erential mineralization along the upper and lower contacts of the LuoxueFormation and within carbonaceous slate of the lowermost E’touchang For-mation (modified from Gong et al., 1996).



Alteration and mineralization

Siliciclastic and tuffaceous rocks of the Yinmin Formationthroughout the Kangdian area have been extensively alteredand contain a variety of secondary minerals such as quartz,dolomite, ferroan dolomite, calcite, albite, potassium feldspar,sericite/muscovite, biotite, chlorite, hematite, and minoramounts of apatite and tourmaline (Figs. 9J, 10A). The matrixof the Yinmin Breccia was particularly susceptible to alter-ation. Locally the breccia matrix has been converted to a fine-to coarse-grained assemblage of albite and ferroan dolomite

with minor apatite (Fig. 10A). Ferroan dolomite appears to

replace earlier dolomite. Albite is rimmed and locally re-placed by potassium feldspar, which in turn may be replacedby muscovite-chlorite. Quartz grains in the Yinmin Formationrocks have been extensively overgrown by diagenetic-hy-drothermal quartz. The alteration assemblage in the YinminFormation and Yinmin Breccia indicates that the rocks weresubjected to early sodic alteration followed by a potassic(dominantly potassium feldspar with lesser biotite) alterationevent. It is usually texturally unclear if potassium feldspar andbiotite are intergrown with, or replaced by, muscovite andmagnesian chlorite.


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A

D

E

1 cm

30 cm

30 cm 1 cm

10 cm

C

F

CpyCpy

2 cm

B

Cu-sulf ide ooid

Cc

Cu-sulfide

Dolostone

Qtz

FIG. 8. Images of mineralized rocks from the Tangdan deposit. A. and B. Stratiform disseminated and veinlet chalcopy-rite and bornite along beds and stylolites in bleached and silicified stromatolitic dolostone. This texture is referred to as“horsetail-like.” C. Oval concentrations of copper sulfides in the dolostone of the Luoxue Formation. Sulfides areconcentrated at the edge of quartz nodules possibly formed by replacement of biogenetic structures. D. The contact between well-mineralized dolostone and relatively barren dolostone in the Luoxue Formation; sulfide-rich bands are at a high angleto bedding. E. High-angle chalcopyrite veins cutting carbonaceous slate of the E’touchang Formation, which contains very fine grained disseminated chalcopyrite. F. Sample of coarse quartz and chalcopyrite in a vein cutting Luoxue Formation dolo-stone.



The basal portion of the Luoxue Formation at Tangdan con-tains a thin (<3m thick) sequence of pale- to medium-gray argillaceous dolostones. The argillaceous material in these dolo-stones, together with blocky diagenetic minerals, were perva-sively replaced by a mixture of potassium feldspar, magnesian

chlorite, and quartz (Fig. 9E, K, L), commonly with extremely fine grains of chalcopyrite (Fig. 10B). These rocks contain dis-seminated, extremely fine grained (1−5 um) quartz (Fig. 11A,B)suggesting weak silicification. Locally the basal Luoxue Forma-tion dolostones have a slight reddish color due to the presence

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Figs .9D and E

B

1 cm 0.5 mm

Bor

Cpy

Qtz

Cc

0.2 mm

0.2 mm0.2 mm

0.5 mm

Cpy

Bor

Ank

Ms

Qtz

Ank

Cpy

Bor

Dig

0.5 mm0.2 mm

0.2 mm

CcBor

Dig

A C

D E F

HG I

Cpy

Kf

Ank

Qtz

Dolomite

Qtz

Hem

Kf

Py?

Kf

Ank

QtzJK

L

0.2 mm 0.5 mm 0.5 mm

FIG. 9. Photomicrographs of rocks from the Tangdan deposit. A. Scan of a thin section of mineralized Luoxue Formationdolostone, showing the location of images D-E. B. Image under crossed polars of bedding-parallel disseminated chalcopyriteand bornite. C. Transmitted light image of (B) showing sulfides (opaque) intergrown with quartz and minor ankerite that re-place wall-rock dolomite. D. Reflected light image showing bedding-parallel disseminated chalcopyrite and bornite with minorcrosscutting veinlets of copper sulfides extending out from sulfide-rich layers. E. Image under crossed polar of (C) showing

bedding-parallel sulfides along bands with minor ankerite and muscovite that probably represent original clay seams in thedolostone. F. Quartz sulfide vein cutting Luoxue Formation dolostone. The vein contains ankerite and albite. G. Hypogenebornite within silicified Luoxue Formation dolostone replaced by supergene digenite, which is in turn replaced by chalcocite.H. Supergene chalcocite enclosing previously formed pyrite. I. Bornite replacing chalcopyrite and both replaced by digenite.J. Hematitic alteration of the Yinmin Formation overprinted by sericite and quartz. K. Dolostone from the Luoxue Forma-tion with disseminated K-feldspar and quartz. This texture is typical of moderately silicified rocks. L. Almost completereplacement of dolomite in the Luoxue Formation by Fe dolomite, K-feldspar, and quartz with disseminated chalcopyrite.



of minor hematite along microfractures. This reddening may be similar to the Rote Fäule alteration recognized in portionsof the Kupferschiefer district of central Europe that is believedto represent oxidation of originally reduced rocks through ex-tensive brine infiltration (Schmidt, 1987; Oszczepalski, 1999).

Luoxue Formation dolostones are pale gray to white col-ored. Paler dolostones are most common in well-mineralized

areas. Local geologists call this bleaching of the dolostones the“fading effect”; the color is used as an important indicator forexploration. Staining of the dolostones (Hitzman, 1999) sug-gests the dolomite is ferroan, though QEMSCAN® analysisindicates the mineral is not pure ankerite. The Luoxue For-mation dolostones are weakly to moderately ferroan through-out the Kangdian area, suggesting a regional alteration event.


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A

Yimin bx

Tang 7

Yinmin bx Tang 7B

1 cm

FIG. 10. QEMSCAN® images of Yinmin Breccia (A) and the lowermost Luoxue Formation argillaceous carbonate rocks(B). A. This sample of Yinmin Breccia (Yinmin bx) is from the Yinachang Mine located approximately 100 km southeast of the Tangdan Mine. The breccia texture of the rock has been nearly completely masked by hydrothermal sodic alteration thatformed an assemblage of ferroan dolomite and albite. Original quartz grains can still be discerned but are largely overgrownby secondary quartz. This sample contains nearly 50% albite, 30% ferroan dolomite, and 5% quartz. The ferroan dolomiteappears to be replacing earlier dolomite (6% of the sample). It is unclear if this dolomite formed carbonate clasts or grew di-agentically in the breccia matrix. The albitized rock contains abundant apatite grains and rare clots of pyrite. Magnesian chlo-rite also forms clots throughout the rock and late veins with ferroan dolomite and quartz that cut albite. Though difficult todiscern at this magnification, albite grains are commonly surrounded and apparently weakly replaced by a thin rim of mus-covite-chlorite-potassium feldspar. The sample contains 3% muscovite, 2% chlorite, and 1% potassium feldspar. B. Sampleof argillaceous dolostone (Tang 7) from the base of the Luoxue Formation at Tangdan. The sample displays a chlorite- andpotassium feldspar-rich bedding plane separating an impure dolostone with quartz, chlorite, and potassium feldspar below from a dolomite bed above containing blocky grains now composed of quartz, chlorite, and potassium feldspar with minorchalcopyrite. The blocky grains may have originally been an evaporite mineral. The rock contains very fine grained dissemi-nated chalcopyrite (2% of the rock) and is cut by late chalcopyrite-quartz veins. This rock has undergone potassic alterationand weak silicification. The rock contains 76% dolomite, 6% quartz, 7% potassium feldspar, 7% muscovite, and 2% calcite.



At Tangdan this ferroan dolomite is cut and replaced by patches of potassium feldspar indicating potassic alterationpostdated ferroan dolomite alteration.

Petrography and QEMSCAN® analysis indicates that theLuoxue Formation ferroan dolostones outside of the TangdanMine area may contain up to 10% replacive quartz (Fig. 11A)and minor albite along argillaceous partings. At Tangdan the

ferroan dolostones commonly contain in excess of 35% re-placive and vein-controlled quartz (Figs. 9C, 11B, C). Theleast altered dolostones at Tangdan contain micrometer-sizedgrains of quartz throughout the rock with concentrationsalong specific, presumably higher permeability, beds (Fig.11A, B). The quartz in these beds commonly displays a nodu-lar appearance. Some of the quartz grains have elongate

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C

1 cm

L1

Lou 2A

Tang 5

L1 Tang 5 A Lou 2A B

FIG. 11. QEMSCAN® images of the Luoxue Formation dolostone. A. Very weakly silicified Luoxue Formation dolostonefrom a stratigraphic section at Tongchang approximately 200 km south of the Tangdan Mine. The sample is dominantly dolomite (90%). It contains beds of nodular quartz as well as extremely fine grains of disseminated quartz; the sample con-tains a total of 7% quartz. The quartz-replaced beds also contain minor albite (2% total in the rock), indicating the rock hasbeen affected by weak sodic alteration. The rock is cut by several thin quartz veins. B. Silicified dolostone (Lou 2A) from theTangdan Mine. The dolomite contains abundant micrometer-sized grains of disseminated quartz that is commonly inter-grown with similar-sized grains of chalcopyrite and lesser bornite. The sample has a single thin argillaceous band composed

of muscovite with subsidiary potassium feldspar, indicating potassic alteration of clay seams within the carbonate rock. Therock is cut by veins of coarse-grained quartz and dolomite with minor muscovite, chalcopyrite and bornite. C. Intensely sili-cified dolostone from the Tangdan Mine (Tang 5). The rock contains 80% quartz and only 17% dolomite. Quartz has pref-erentially replaced a number of beds and occurs as late, monomineralic veins. The rock contains minor (1%) muscovite andtrace amounts of both potassium feldspar and chlorite. Chalcopyrite occurs within some silicified beds but not in others.



shapes suggestive of replaced gypsum or other precursorevaporite minerals (Fig. 11C).

Argillaceous beds within the dolostones at Tangdan havebeen converted to an assemblage of fine-grained potassiumfeldspar and muscovite (Fig. 9E, L) or chlorite and muscovite(Fig. 11B). These assemblages probably represent potassic al-teration of clay seams. The absence of a significant amount of

potassium feldspar, muscovite, and chlorite throughout mostof the Luoxue Formation dolostones at Tangdan is probably due to their originally low aluminum (clay) content.

The basal portion of the E’touchang Formation at Tangdandisplays variable degrees of both potassic alteration and silici-fication. Weakly veined, but still sulfide mineralized blackshale contains significant quartz intergrown with sulfides, sug-gesting hydrothermal silicification (Fig. 12A). Heavily veinedslate has been converted to a potassium feldspar-quartz-mus-covite rock (Fig. 12B) due to intense potassic alteration.

Additional studies are required to determine the extent of sodic, potassic, and siliceous alteration both in the broaderTangdan Mine area and throughout the Kangdian region. Al-bitic alteration is best developed outside of the Tangdan de-posit. It affects the Yinmin and Luoxue Formations as well asthe Yinmin Breccia. Samples of E’touchang Formation silt-stones away from Tangdan were not examined petrographi-

cally, so it is not known whether sodic alteration extended tothis stratigraphic level. However, Yinmin Breccia cutting theE’touchang Formation has a similar megascopic appearanceto breccia known to contain replacive albite, suggesting thatsodic alteration did extend this high in the sequence. Based onscattered field traverses throughout the area, it is thought thatthe region was subjected to widespread alteration similar tothat observed in the Zambian Copperbelt (Selley et al., 2005).

Whereas sulfides occur from the upper Yinmin Formationthrough to the lower E’touchang Formation at Tangdan, they


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1 cm

ETOU-3 Tao-1

ETOU-3

Tao-1

A B

FIG. 12. QEMSCAN® images of black shale from the basal E’touchang Formation at the Tangdan Mine. A. Finely lam-inated black shale (ETOU-3) consisting of quartz (62%), chlorite (20%), and muscovite (11%) with abundant disseminated,fine-grained chalcopyrite (6%). The rock also contains 2% biotite/phlogopite primarily intermixed along chlorite bands. B.Brecciated and veined black shale (Tao-1) that has been intensely potassically altered with 32% potassium feldspar. The rockis cut by quartz veins with dolomite centers. The veins contain chalcopyrite and minor pyrite and are cut by chalcopyrite veins. The rock contains a total of 12% chalcopyrite. The quartz veins have weak muscovite selvages probably derived frombreakdown of potassium feldspar.



are concentrated in weakly argillaceous dolostones of thelower and upper Luoxue Formation and within black shalesof the basal E’touchang Formation. Diagenetic pyrite is com-mon in the basal E’touchang Formation where it forms dis-seminated euhedral to subhedral crystals. Although minor euhedral to subhedarl pyrite is present in argillaceous inter-calations in the Luoxue Formation, it is unclear whether it

was deposited during diagenesis or during the later sulfidemineralization event. Pyrite is commonly partially replaced by copper sulfides (Fig. 9H). Chalcopyrite is the dominant sul-fide at Tangdan. Where present, bornite is commonly inter-grown with chalcopyrite (Fig. 9D, I). The majority of chal-cocite observed at Tangdan appears to be supergene in origin.Hypogene chalcocite has been reported from deep levels of the mine by Gong et al. (1996).

Copper sulfides do not appear to be spatially associated with zones of either sodic or potassic alteration. Chalcopyriteand bornite are typically intergrown with disseminated re-placive quartz, indicating that they were precipitated duringsilicification. A large amount of the sulfides in both the Lu-oxue and E’touchang Formations occurs as micrometer-sizedgrains disseminated in silicified rocks (Figs. 11, 12). Such sul-fide grains are virtually invisible megascopically and difficultto see in thin section. Chalcopyrite and bornite also occur inlater quartz-sulfide-(dolomite-calcite-ankerite-siderite-mus-covite-chlorite) veins that crosscut silicified rock (Fig. 8E).Barren quartz veins in many samples (e.g., Fig. 11C) indicatethat silicification continued after sulfide precipitation.

The Tangdan deposit contains weathered zones with a su-pergene mineral assemblage of chalcocite, digenite, covellite,

and malachite. Digenite commonly replaces bornite and is inturn replaced by chalcocite (Fig. 9G, I). Supergene alterationoccurs along high-angle faults and fractures and is recognized todepths of several tens of meters. The absence of large super-gene enriched zones in the Kangdian region, similar to those inthe Central African Copperbelt, is probably due to recent up-lift and erosion as the result of Himalayan mountain formation.

Paragenetic sequence of alteration and mineralization

Detailed petrographic work at Tangdan suggests the hostrocks have been subjected to a protracted period of alterationand mineralization (Fig. 13). The earliest alteration event re-sulted in albitization that was concentrated in the Yinmin For-mation. Sodic alteration assemblages are better developed orpreserved outside of the immediate mine area. Ferroan dolomi-tization affected both the Yinmin and Luoxue Formations andmay have occurred concurrently with sodic alteration. Al-bitized and ferroan dolomitized rocks were then subjected topotassic alteration that precipitated potassium feldspar andminor biotite in beds that contained sufficient aluminum,such as intercalations within the upper Yinmin Formation, thebasal argillaceous Luoxue Formation, along clay seams withinthe Luoxue Formation dolostones, and in the shales of the E’-touchang Formation. Potassically altered zones are com-monly barren of sulfides, suggesting that this alteration event

was not associated with significant copper mineralization.The major alteration event affecting the Tangdan area was

a period of silicification that appears to have affected the entire sedimentary sequence but was concentrated in the Luoxue Formation. Silicification was initially permeability

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Ferroan dolomite

Albite

Potassium feldspar

Dolomite

Ankerite

Siderite

Calcite

Biotite

Magnesian chlorite

Muscovite

QuartzPyrite

Chalcopyrite

Bornite

Digenite

Chalcocite

Covellite

Malachite

Sodic Alteration

and FerroanDolomitization

Potassic

Alteration

Silicification

HypogeneMineralization

Supergene

Alteration

TIME

FIG. 13. Paragenetic sequence of alteration and mineralization at the Tangdan deposit.



controlled with some beds becoming much more silicifiedthan adjacent ones. Beds in the Luoxue Formation containnodular to elongate quartz grain shapes suggesting that someof the silica replaced evaporites, similar to the silicificationobserved in the Katangan Copperbelt (Muchez et al., 2008).Chalcopyrite and bornite are intimately intergrown with bothfine-grained disseminated quartz and coarser grained quartz

in veins. Quartz-sulfide and quartz-dolomite-(calcite)-sulfide veins cut silicified and mineralized dolostones, suggesting thehost rocks lost permeability during silicification. Where sul-fide-bearing quartz or quartz-dolomite veins cut previously potasically altered rocks, potassium feldspar was commonly altered to muscovite, suggesting the siliceous fluids may havehad a slightly acid pH. Magnesian chlorite occurs in trace tomoderate amounts throughout the Tangdan area. It is unclearif it is paragenetically related to potassic alteration or to thelater silicification event.

The overall paragenetic sequence at Tangdan includes anearly sodic alteration event followed by a potassic event. Sul-fide mineralization accompanied a siliceous alteration eventperhaps related to magnesium-rich brine. This parageneticsequence of alteration and mineralization is similar to that ob-served in the Katangan Copperbelt (Muchez et al., 2008; ElDesouky et al., 2009).

Analytical Results of Stable Isotopes

Carbon and oxygen isotopes

Carbon and oxygen isotope data, including previously published data, are presented in Table 1. Dolomite samplesof unmineralized ferroan dolostone from the lower portion of the Luoxue Formation at Tongchang (Fig. 1B) have δ13C V-PDB

values of 0.6 to 1.0‰ and an identical δ18O V-SNOW value of 19.2‰ (Fig. 14). Dolostone samples of the Luoxue Formation

from Tangdan have relatively homogeneous C and O isotopes, with δ13C V-PDB and δ18O V-SNOW values ranging from 0.2 to 1.3‰ and from 19.1 to 22.4‰, respectively (Fig. 14). Dolomitefrom highly silicified dolostones does not display significantly different isotopic values from less silicified dolostones. The δ13C

values for both the unmineralized and mineralized Luoxue For-mation dolomites are similar to those of other early Proterozoic

dolostones (Kah et al., 1999; Bartley et al., 2001). The resultssuggest insignificant changes to isotopic values of the carbon-ate rocks due to diagenetic and hydrothermal fluid interaction.

In contrast to the host dolostones, samples of carbonateminerals within sulfide-bearing veins show significant

variations in both carbon and oxygen isotopes (Fig. 14). Onegroup of carbonate minerals displays a trend toward lighteroxygen isotope values (min 7.4‰), with a correspondingslight decrease in carbon isotope values (min −3.5‰). Asmaller group of samples shows relatively little change in oxy-gen isotope values but a significant shift to carbon isotope val-ues as light as −8.5‰.

The shift to lower oxygen isotope values with only a slightshift in carbon isotope values is typical of burial diagenesis incarbonate rocks (Choquette and James, 1990; Ohmoto andGoldhaber, 1997) and results from increased exchange of oxy-gen, which is abundant in water, relative to the exchange of car-bon which is generally present in low concentrations in water.The trend of vein carbonate minerals toward significantly lower carbon isotope values may indicate isotopic exchange

with organic carbon (Valley, 1986). The low δ13C V-PDB values(−9.5 to −27‰) of the carbonaceous slates of the E’touchangFormation represent a potential source of light carbon.

Sulfur isotopes

Hypogene chalcopyrite and bornite from the Tangdan de-posit have δ34S values ranging from −12.7 to +9.3‰; the val-

ues cluster between −3‰ to +5‰ (Table 2; Fig. 15A). Theδ34S values of supergene chalcocite are generally similar tothose of bornite and chalcopyrite with one heavy outlier(+26.7‰). The sulfur isotope data from the Tangdan depositare generally similar to values observed in other Dongchuansedimentary rock-hosted strata-bound Cu deposits (Fig.15B). The absence of significantly depleted sulfur values in-dicates that biogenic processes were not important in the pre-cipitation of sulfides in the Kangdian copper deposits.Though the values cluster near 0‰, there is no geologic evi-dence of widespread magmatism or igneous rocks that couldprovide a magmatic sulfur source. The trend toward heaviersulfur isotope values probably reflects the involvement of sea-

water sulfate, which averaged approximately +20‰ through-out the Mesoproterozoic (Strauss, 1993). Sulfur in the sul-fides was most likely derived from oceanic sulfate orevaporitic sulfate from evaporites within the Yinmin or Lu-oxue Formations. The variable δ34S values of the sulfides areconsistent with thermochemical reduction of sulfate (e.g.,Ohmoto and Goldhaber, 1997; McGowan et al., 2003).

Discussion

Ore-forming mechanism

Strata-bound copper deposits occur throughout the Kang-dian region. Copper sulfides are present regionally along the


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-20

-15

-10

-5

0

5

0 5 10 15 20 25 30

Mineralized vein carbonate (E’touchang Fm Tangdan)

Unmineralized Luoxue dolomite (Tongchang)

Mineralized Luoxue dolomite (Tangdan)

Mineralized Luoxue dolomite (Dongchuan)

Mineralized vein carbonate (Tangdan)

Mineralized vein carbonate (Dongchuan)

δ18O (‰)

1 3 C ( ‰ )

FIG. 14. Carbon and oxygen isotope data for dolomites of host strata andcarbonate minerals in mineralized veins from the Tangdan deposit. The hostrock dolomites display a restricted range typical of early Mesoproterozoicdolomites (Kah et al., 1999; Bartley et al., 2001). Carbonate minerals in sul-fide-bearing veins display two divergent trends, one towards lighter oxygenisotope values with a corresponding slight decrease in carbon isotope valuesand another with little change in oxygen isotope values but a significant shiftto lighter carbon isotope values.



interface between oxidized, hematitic siltstones and sand-stones of the Yinmin Formation red beds and shallow marinedolostones of the Luoxue Formation. Mineralized zones alsooccur locally along the contact between the dolostones of theupper Luoxue Formation and black shales of the overlying E’-touchang Formation. In the Dongchuan district, deposits areclustered in areas containing discordant Yinmin breccia.

Sedimentary rock-hosted stratiform copper deposits arecommonly controlled by faults that allowed access of oxidized,copper-bearing brines to higher stratigraphic levels wherethey encountered a reducing environment capable of precip-itating sulfides (Hitzman et al., 2005). Fault control may besubtle and such faults were commonly modified by later basininversion. Recognition of the former presence of early faultsis commonly through detailed stratigraphic analysis that candemonstrate thickness or facies changes across such struc-tures. Such detailed work has not yet been conducted in theKangdian area. Though mineralizing fluid-channeling faults

have not yet been demonstrated in the Dongchuan deposits,it is likely that they may now be represented by linear zonesof the Yinmin Breccia. These breccias, which are thought toresult from diapiric salt movement, were probably concen-trated along preexisting structures within the basin. It is un-clear if mineralization in the region took place prior to, dur-ing, or after breccia formation.

The fluids responsible for the formation of sedimentary rock-hosted stratiform copper deposits are generally thoughtto be oxidized, saline brines (Hitzman et al., 2005). Quartzfrom both the stratiform and discordant ores in the Kangdiancontain liquid-rich aqueous and CO2-dominated inclusions

with subordinate daughter mineral-bearing inclusions in thediscordant ores (Ran, 1989b). Fluid inclusions from quartz of the stratiform copper ores have homogenization tempera-tures (Th) ranging from 109° to 209°C with an average of 169°C; whereas those in the discordant ores have Th rangingfrom 131° to 290°C with an average of 230°C (Ran, 1989b).

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TABLE 2. Sulfur Isotope from Kangdian Sedimentary Rock-Hosted Strata-bound Cu Deposits

Sample Mineral Formation δ34S (‰) Reference1 Sample Mineral Formation δ34S (‰) Reference1

Tangdan deposit Other deposits in Dongchuan area (cont.)

YN07-411 Chalcopyrite Luoxue –1.1 This study (HKU)YN07-412 Chalcopyrite Luoxue –0.3 This study (HKU)YN07-414 Bornite Luoxue –0.7 This study (HKU)

YN07-415 Bornite Luoxue 4.6 This study (HKU)YN07-416 Bornite Luoxue –1.1 This study (HKU)YN07-419 Chalcocite Luoxue 9.3 This study (HKU)Tang 4a Chalcocite Luoxue 26.7 This study (CSM)Tang 4b Bornite Luoxue –12.7 This study (CSM)Tang 4c Chalcocite Luoxue –12.3 This study (CSM)Tang 5a Chalcocite Luoxue –2.4 This study (CSM)Tang 5b Bornite Luoxue –2.9 This study (CSM)Lou-2a Chalcopyrite Luoxue –0.9 This study (CSM)Lou-2b Bornite Luoxue 0.1 This study (CSM)Tang 8a Chalcopyrite Luoxue 9.3 This study (CSM)Tang 8b Chalcocite Luoxue 10.2 This study (CSM)Tang 9a Chalcocite Luoxue –0.5 This study (CSM)Tang 9b Chalcocite Luoxue –1.4 This study (CSM)Tang 7 Bornite Yinmin/Luoxue 1.3 This study (CSM)

Taoyuan Mine (E’touchang Formation orebody of Tangdan deposit)

ETOU-3 Chalcopyrite Etouchang –1.7 This study (CSM)ETOU-4 Chalcopyrite Etouchang –0.7 This study (CSM)Tao-1 Chalcopyrite Etouchang 5.2 This study (CSM)Tao-2 Chalcopyrite Etouchang 6.3 This study (CSM)T42-1 Pyrite Etouchang 7.1 Chen and Ran (1992)L86 Chalcopyrite Etouchang 7.4 Chen and Ran (1992)L25 Pyrite Etouchang 4.3 Chen and Ran (1992)

Tongchang section

L9 Chalcocite Luoxue 7.4 This study (CSM)

Other deposits in Dongchuan area

YN07-401 Chalcopyrite Luoxue 1.8 This study (HKU)YN07-402 Chalcopyrite Luoxue 2.2 This study (HKU)YN07-403 Chalcopyrite Luoxue 0.9 This study (HKU)

YN07-404 Chalcopyrite Luoxue 0.6 This study (HKU)T-31 Bornite Luoxue 5.7 Chen and Ran (1992)L97 Chalcocite Luoxue 3.5 Chen and Ran (1992)L97 Bornite Luoxue 3.5 Chen and Ran (1992)L98 Chalcocite Luoxue 4.1 Chen and Ran (1992)L98 Bornite Luoxue 3.7 Chen and Ran (1992)

L55 Chalcocite Luoxue –0.5 Chen and Ran (1992)L55 Bornite Luoxue 0.6 Chen and Ran (1992)L105 Chalcocite Luoxue 13.7 Chen and Ran (1992)

L105 Bornite Luoxue 9 Chen and Ran (1992)T-53 Bornite Luoxue 6.4 Chen and Ran (1992)L11 Bornite Luoxue 6.2 Chen and Ran (1992)L14 Chalcocite Luoxue 6.9 Chen and Ran (1992)L14 Bornite Luoxue 5.7 Chen and Ran (1992)T45-2 Bornite Luoxue 6.5 Chen and Ran (1992)LK6-5 Bornite Luoxue 4.4 Chen and Ran (1992)L17-1 Chalcocite Luoxue 12.1 Chen and Ran (1992)L17-1 Bornite Luoxue 9.7 Chen and Ran (1992)L17-2 Chalcopyrite Luoxue 12.2 Chen and Ran (1992)L17-2 Bornite Luoxue 11.2 Chen and Ran (1992)T27 Bornite Luoxue 8.1 Chen and Ran (1992) yk30-25 Chalcopyrite Luoxue 6.7 Chen and Ran (1992) yk14-12 Bornite Luoxue –2 Chen and Ran (1992) yk30-21 Pyrite Luoxue –1.4 Chen and Ran (1992)TK11-12 Bornite Luoxue 13.7 Chen and Ran (1992)L56 Chalcopyrite Luoxue 3 Chen and Ran (1992)

T54 Bornite Luoxue 11 Chen and Ran (1992)T59 Bornite Luoxue 13.1 Chen and Ran (1992)T44 Chalcopyrite Luoxue 10.8 Chen and Ran (1992)L12 Bornite Luoxue 9.4 Chen and Ran (1992)T44 Bornite Luoxue 9.4 Chen and Ran (1992)T60 Chalcopyrite Luoxue 1.7 Chen and Ran (1992)L71 Chalcopyrite Luoxue 4.6 Chen and Ran (1992)L71 Bornite Luoxue 2.9 Chen and Ran (1992)L83-3 Chalcopyrite Luoxue 2.5 Chen and Ran (1992)L83-2 Bornite Luoxue 2.8 Chen and Ran (1992)L83-3 Chalcocite Luoxue 5.9 Chen and Ran (1992)s-1 Chalcopyrite Luoxue 18.8 Chen and Ran (1992)s-2 Chalcopyrite Luoxue 9.4 Chen and Ran (1992)s-3 Chalcopyrite Luoxue 19.5 Chen and Ran (1992)s-4 Chalcopyrite Luoxue –1.5 Chen and Ran (1992)s-6 Chalcopyrite Luoxue 6.2 Chen and Ran (1992)

L78 Chalcocite Luoxue 9.7 Chen and Ran (1992)L91-1 Chalcocite Luoxue 16.7 Chen and Ran (1992)L111 Chalcopyrite Luoxue 15.2 Chen and Ran (1992)L111 Bornite Luoxue 10.4 Chen and Ran (1992)L113 Bornite Luoxue 14.8 Chen and Ran (1992)

1 HKU = samples analyzed in China, CSM = samples analyzed at the Colorado School of Mines



Calculated salinities of the fluid inclusions mostly fall in therange of 10.0 to 23.2 wt % NaCl equiv but range up to 35 wt% NaCl equiv for the daughter mineral-bearing inclusions(Ran, 1989b). Ruan et al. (1991) reported similar results fromfluid inclusions in quartz veinlets containing copper sulfidesfrom the Dongchuan region. These inclusions contain liquid, vapor, and daughter minerals NaC1, CaC12, KC1, and BaC12

that homogenize between 200° and 280°C.Mineralization in sedimentary rock-hosted stratiform cop-

per systems was fundamentally due to reduction of oxidizedcopper-bearing brines. Such reduction can be accomplishedthrough reaction of the oxidized fluids with an in situ reduc-tant, such as organic matter, or with migrated hydrocarbons(Hitzman et al., 2005). At Tangdan abundant carbonaceousmaterial and lesser diagnetic pyrite in slates of the E’-touchang Formation provide obvious in situ reductants. Thesource of reductant within the Luoxue Formation dolo-stones, the major host rock in the district, is less obvious.Carbon and oxygen isotope results from carbonate mineralsin sulfide veins suggest local interaction with organic matter

but are not as compelling as isotopic results from other dis-tricts worldwide (e.g., Selley et al., 2005).

The dolostone-hosted ores at Tangdan are similar to thedeposits of the Katangan Copperbelt where sulfides are con-centrated in dolostones of the Mines Series. Like the LuoxueFormation dolostones at Tangdan, the Mines Series dolo-stones of the Democratic Republic of Congo are pale colored,

often weakly ferroan, and lack evidence of significant in situcarbonaceous material or migrated hydrocarbons (Cailteux,1994; Cailteux et al., 2005). The Luoxue Formation dolo-stones and the Mines Series dolostones are also similar in dis-playing significant silicification that is spatially associated withsulfides. Recent work suggests that sulfide in the Congolesedeposits was generated by dissolution and reduction of evap-oritic sulfate within the dolostones (Muchez et al., 2008).Though evaporite pseudomorphs are not as well preserved inthe Luoxue Formation dolostones as in dolostones from theMines Series, the nodular and tabular shapes of some quartzgrains in the Tangdan rocks suggest that similar processesmay have been operative. Sulfide precipitation at Tangdanmay also have been triggered by an increase of fluid pH dur-ing silicification of the dolostones, which could have led to adecrease in sulfide solubility.

As in the Congolese dolostone-hosted deposits, sulfides atTangdan occur as bedding-controlled disseminations and

within stylolites and crosscutting fractures. The amount of copper sulfides in the rocks does not always increase propor-tionally with the degree of silicification. This is similar to thesituation in the Congolese Copperbelt where the Roches Sil-iceuses Cellulaires, the most silicified layer in the Mines Se-ries sequence (Cailteux, 1994), is generally less mineralizedthan the less silicified, but commonly more argillaceous dolo-stones stratigraphically above and below (Cailteux et al.,2005).

Constraint on the timing of mineralization

The age of mineralization in the Dongchuan-type copperdeposits has been contentious. Synsedimentary, exhalativemodels for the deposits based on their strata-bound naturehave been widely embraced (Gong and Wang, 1981; Gong etal., 1996; Chang et al., 1997). However, Qiu et al. (1997) re-ported a Pb-Pb isochron age of 794 ± 73 Ma for stratiformcopper sulfides at Tangdan and inclusion fluids from sulfide-bearing quartz veins give 40Ar/ 39Ar plateau ages of 711 ± 34and 768 ± 1 Ma (Qiu et al., 1997; Ye et al., 2004). These agesare contemporaneous with regional magmatism and wereinterpreted to support the epigenetic model advocated by

Meng et al. (1948) and Li et al. (1953). A diagenetic model forthe formation of the deposits has also been suggested but lacksgeochronological constraints (Ran, 1983, 1989a; Hua, 1990).

A minimum age of the Tangdan mineralization event isprovided by the recently published zircon U-Pb age of 1047± 3 Ma (Zhao, 2010) for the gabbroic intrusion that cuts thedeposit. Past attempts to directly date the deposit have re-sulted in younger ages that are now known to be geologically unreasonable. The Neoproterozoic ages probably reflectthermal overprinting and resetting of the isotopic systems.

The detailed petrographic work conducted at Tangdan in-dicates that the host rocks for the deposit underwent signifi-cant alteration (sodic, ferroan dolomitization, potassic) prior


0361-0128/98/000/000-00 $6.00 373

Bornite

Chalcopyrite

Chalcopyrite (E’touchang Fm)

Chalcocite

-15 -10 -5 0 5 10 15 20 25 3034

S ( )δ

N u m b e r

0

2

4

6

N u m b e r

0

2

4

6

-15 -10 -5 0 5 10 15 20 25 3034 S ( )δ

Bornite

Chalcopyrite

ChalcociteB

A

FIG. 15. A. Plot of sulfur isotope data for hypogene chalcopyrite and bor-nite and supergene chalcocite from the Tangdan deposit. B. Plot of sulfur iso-tope data for copper sulfides from other deposits in the Kangdian region.



to the silicification event associated with copper mineralization.The timing of these alteration events relative to host-rock de-position is unknown. However, textural evidence suggests thatLuoxue Formation dolostones retained some permeability and/or geochemical variability such as distribution of evaporiteminerals until the period of silicification and sulfide mineral-ization. Textures of mineralized rocks at Tangdan indicate that

sulfide mineralization could have taken place while the rocks were incompletely lithified but certainly continued into a pe-riod when the rocks were thoroughly lithified. Fluid inclusionresults for the district indicate mineralizing fluids temperaturesin excess of 200°C (Ran, 1989b), suggesting deep burial in theabsence of a direct magmatic heat source. The preponder-ance of evidence suggests mineralization in the Dongchuandeposits occurred relatively late in the basin’s history.

Many sedimentary rock-hosted copper districts have evi-dence of lengthy periods of mineralization, for example,Zambian stratiform Cu deposits and those in Kupferschieferblack shale at Germany (Selley et al., 2005; Symons et al.,2011), in some cases apparently extending for tens to hun-dreds of millions of years (Hitzman et al., 2010). It is likely that the sedimentary rock-hosted strata-bound copper de-posits of the Kangdian region of South China were alsoformed over an extensive time period.

Acknowledgments

This study was supported by grants from the ResearchGrant Council of Hong Kong (HKU707210P and HKU707511P) (Zhou), funding from Jinshan Gold Mines Inc.(Hitzman), and the financial support for the Chemical Geo-dynamics Joint Laboratory from Croucher Foundation be-tween HKU and GIGCAS. We thank geologists from ChinaUniversity of Geosciences (Wuhan), Yunnan GeologicalSurvey, and local mines especially Zhanke Li, Yongchang

Wang, and Hua Li for their help during the fieldwork. Tworeviewers, Prof. Gregor Borg and Prof. Franco Pirajno, andthe editor, Dr. Larry Meinert, are gratefully acknowledged forproviding constructive comments.

REFERENCES

Bartley, J.K., Semikhatov, M.A., Kaufman, A.J., Knoll, A.H., Pope, M.C., andJacobsen, S.B., 2001, Global events across the Mesoproterozoic-Neopro-terozoic boundary: C and Sr isotopic evidence from Siberia: PrecambrianResearch, v. 111, p. 165−202.

Beaudoin, G., Taylor, B.E., Rumble, D., III, and Thiemens, M., 1994, Varia-tions in the sulfur isotope composition of troilite from the Cañon Diabloiron meteorite: Geochimica et Cosmochimica Acta, v. 58, p. 4253−4255.

Brown, A.C., 1997, World-class sediment-hosted stratiform copper deposits:Characteristics, genetic concepts and metallotects: Australian Journal of

Earth Sciences, v. 44, p. 317−328.Cailteux, J., 1994, Lithostratigraphy of the Neoproterozoic Shaba-type

(Zaire) Roan Supergroup and metallogenesis of associated stratiform min-eralization: Journal of African Earth Sciences, v. 19, p. 279−301.

Cailteux, J.L.H., Kampunzu, A.B., Lerouge, C., Kaputo, A.K., and Milesi,J.P., 2005, Genesis of sediment-hosted stratiform copper-cobalt deposits,Central African Copperbelt: Journal of African Earth Sciences, v. 42, p.134−158.

Chang, X., Zhu, B., Sun, D., Qiu, H., and Zou, R., 1997, Isotope geochemistry study of Dongchuan copper deposits in Middle Yunnan Province, SW China: Stratigraphic chronology and application of geochemical explorationby lead isotopes: Geochimica, v. 26, p. 32−38 (in Chinese with English abs.).

Chen, H., and Ran, C., 1992, Isotope geochemistry of copper deposits inKandian Axis: Beijing, Geological Publishing House, 100 p. (in Chinese with English abs.).

Choquette, P.W., and James, N.P., 1990, Limestones—the burial diageneticenvironment: Geoscience Canada Reprint Series 4, p. 75−111.

Craig, H., 1957, Isotopic standards for carbon and oxygen and correction fac-tors for mass-spectrometric analysis of carbon dioxide: Geochimica et Cos-mochimica Acta, v. 12, p. 133−149.

El Desouky, H.A., Muchez, P., and Cailteux, J., 2009, Two Cu-Co sulfidephases and contrasting fluid systems in the Katanga Copperbelt, Democra-tic Republic of Congo: Ore Geology Reviews, v. 36, p. 315−332.

Gong, L., and Wang, C., 1981, On the origin of “Dongchuan type” copper de-posit: Scientia Geologica Sinica, p. 203−211 (in Chinese).

Gong, L., He, Y., and Chen, T., 1996, Proterozoic Dongchuan-type rift Cudeposit in Yunnan: Beijing, Metallurgical Industry Publication, 248 p. (inChinese).

Greentree, M.R., and Li, Z.-X., 2008, The oldest known rocks in south-west-ern China: SHRIMP U-Pb magmatic crystallisation age and detrital prove-nance analysis of the Paleoproterozoic Dahongshan Group: Journal of Asian Earth Sciences, v. 33, p. 289−302.

Greentree, M.R., Li, Z.-X., Li, X.-H., and Wu, H., 2006, Late Mesoprotero-zoic to earliest Neoproterozoic basin record of the Sibao orogenesis in western South China and relationship to the assembly of Rodinia: Precam-brian Research, v. 151, p. 79−100.

Hitzman, M.W., 1999, Routine staining of drill core to determine carbonatemineralogy and distinguish carbonate alteration textures: Mineralium De-posita, v. 34, p. 794−798.

Hitzman, M.W., Kirkham, R., Broughton, D., Thorson, J., and Selley, D.,

2005, The sediment-hosted stratiform copper ore system: ECONOMIC GE-OLOGY 100TH ANNIVERSARY V OLUME, p. 609−642.

Hitzman, M.W., Selley, D., and Bull, S., 2010, Formation of sedimentary rock-hosted stratiform copper deposits through Earth history: ECONOMIC

GEOLOGY, v. 105, p. 627−639.Hua, R., 1990, The sedimentation-reworking genesis of Dongchuan-type strat-

iform copper deposits: Chinese Journal of Geochemistry, v. 9, p. 231−243.Hua, R.M., 1993, Some characteristics of sedimentation of the Yinmin For-

mation: Acta Sedimentologica Sinica, v. 11, p. 32−40 (in Chinese with Eng-lish abs.).

Hua, R.M., Ruan, H.C., Liu, Y., and Huang, Y.S., 1988, Characteristics of carbon and oxygen isotope composition of the Dongchuan copper deposits:Journal of Guilin College of Geology, v. 8, p. 57−62 (in Chinese with Eng-lish abs.).

Jackson, M.P.A., Warin, O.N., Woad, G.M., and Hudec, M.R., 2003, Neo-proterozoic allochthonous salt tectonics during the Lufilian orogeny in the

Katangan Copperbelt, central Africa: Geological Society of America Bul-letin, v. 115, p. 314−330.Kah, L.C., Sherman, A.G., Narbonne, G.M., Knoll, A.H., and Kaufman, A.J.,

1999, δ13C stratigraphy of the Proterozoic Bylot Supergroup, Baffin Island,Canada: Implications for regional lithostratigraphic correlations: CanadianJournal of Earth Sciences, v. 36, p. 313−332.

Li, X.-H., Li, Z.-X., Ge, W., Zhou, H., Li, W., Liu, Y., and Wingate, M.T.D.,2003, Neoproterozoic granitoids in South China: Crustal melting above amantle plume at ca.825 Ma?: Precambrian Research, v. 122, p. 45−83.

Li, X.J., Hua, R.Y., Li, L.J., Fan, C.Y., Duan, G.L., and Qu, Y.C., 1953, Geol-ogy of the Dongchuan-type copper deposit in Yunnan: Acta GeologicaSinica, v. 33, p. 76−84 (in Chinese).

Li, Z.X., Li, X.H., Kinny, P.D., Wang, J., Zhang, S., and Zhou, H., 2003,Geochronology of Neoproterozoic syn-rift magmatism in the Yangtze Cra-ton, South China and correlations with other continents: Evidence for amantle superplume that broke up Rodinia: Precambrian Research, v. 122,p. 85−109.

McGowan, R.R., Roberts, S., Foster, R.P., Boyce, A.J., and Coller, D., 2003,Origin of the copper-cobalt deposits of the Zambian Copperbelt: An epige-netic view from Nchanga: Geology, v. 31, p. 497−500.

Meng, H.M., Chang, H.C., Hsu, S.C., Teng, Y.S., and Shu, C.A., 1948, Geol-ogy of the Tungchuan district, northeastern Yunnan: Shanghai, NationalResearch Institute of Geology, 68 p.

Muchez, P., Vanderhaeghen, P., El Desouky, H., Schneider, J., Boyce, A., De- waele, S., and Cailteux, J., 2008, Anhydrite pseudomorphs and the origin of stratiform Cu-Co ores in the Katangan Copperbelt (Democratic Republicof Congo): Mineralium Deposita, v. 43, p. 575−589.

Ohmoto, H., and Goldhaber, M.B., 1997, Sulfur and carbon isotopes, inBarnes, H.L., ed., Geochemistry of hydrothermal ore deposits: New York,John Wiley & Sons, p. 517−611.

Oszczepalski, S., 1999, Origin of the Kupferschiefer polymetallic mineraliza-tion in Poland: Mineralium Deposita, v. 34, p. 599−613.

374 ZHAO ET AL.

0361-0128/98/000/000-00 $6.00 374



Qiu, H.N., Sun, D.Z., Zhu, B.Q., and Chang, C.Y., 1997, Isotopic geochem-istry study of Dongchuan copper deposits in middle Yunnan Province, SW China: Dating the ages of mineralizations by Pb-Pb and 40Ar-39Ar methods:Geochimica, v. 26, p. 39−45.

Ran, C.Y., 1983, On genetic model of Dongchuan type strata-bound copper-deposit: Scientia Sinica (Series B), v. 26, p. 983−993.

——1989a, Dongchuan-type stratabound copper deposits, China: A geneticmodel: Geological Association of Canada Special Paper 36, p. 667−677.

——1989b, Formation mechanism of stratabound copper deposit in Kang-dian Axis: Beijing, Geological Publishing House, 50 p. (in Chinese withEnglish abs.).

Ruan, H.C., Hua, R.M., and Cox, D.P., 1991, Copper deposition by fluid mix-ing in deformed strata adjacent to a salt diapir, Dongchuan area, YunnanProvince, China: ECONOMIC GEOLOGY, v. 86, p. 1539−1545.

Schmidt, F.P., 1987, Alteration zones around Kupferschiefer-type base metalmineralization in West Germany: Mineralium Deposita, v. 22, p. 172−177.

Selley, D., Broughton, D., Scott, R.J., Hitzman, M., Bull, S.W., Large, R.R.,McGoldrick, P.J., Croaker, M., and Pollington, N., 2005, A new look at thegeology of the Zambian Copperbelt: ECONOMIC GEOLOGY 100TH ANNIVER-SARY V OLUME, p. 965−1000.

Strauss, H., 1993, The sulfur isotopic record of Precambrian sulfates: New data and a critical evaluation of the existing record: Precambrian Research, v. 63, p. 225−246.

Sun, K., Shen, Y., Liu, G., Li, Z., and Pan, X., 1991, Proterozoic iron-copperdeposits in Central Yunnan Province: Wuhan, China University of Geo-

science Press, 169 p (in Chinese with English abs.).Sun, Z.-M., Yin, F.-G., Guan, J.-L., Liu, J.-H., Li, J.-M., Geng, Y.-R., and

Wang, L.-Q., 2009, SHRIMP U-Pb dating and its stratigraphic significanceof tuff zircons from Heishan Formation of Kunyang Group, Dongchuanarea, Yunnan Province, China: Geological Bulletin of China, v. 28, p.896−900 (in Chinese with English abs.).

Symons, D., Kawasaki, K., Walther, S., and Borg, G., 2011, Paleomagnetismof the Cu-Zn-Pb-bearing Kupferschiefer black shale (Upper Permian) atSangerhausen, Germany: Mineralium Deposita, v. 46, p. 137−152.

Valley, J.W., 1986, Stable isotope geochemistry of metamorphic rocks: Re- views in Mineralogy, v.16, p. 445−489.

Wang, X.L., Zhou, J.C., Griffin, W.L., Wang, R.C., Qiu, H.S., O’Reilly, S.Y., Xu, X.S., Liu, X.M., and Zhang, G.L., 2007, Detrital zircon geochronology of Precambrian basement sequences in the Jiangnan orogen: Dating the as-sembly of the Yangtze and Cathaysia blocks: Precambrian Research, v. 159,p. 117−131.

Wu, M.-D., Duan, J.-S., Song, X.-L., Chen, L., and Dan, Y., 1990, Geology of Kunyang Group in Yunnan Province: Kunming, Scientific Press of YunnanProvince, 265 p. (in Chinese with English abs.).

Xiong, X.W., Chen, Y.Y., Hou, S.G., and Xue, S.R., 1993, Studies on lithofa-cies and paleogeography of the Yinmin Formation: China University of Geosciences (Wuhan), Unpublished report, 94 p. (in Chinese with Englishabs.).

Ye, L., Liu, Y.-P., Li, C.-Y., and Liu, J.-J., 2004, The Ar-Ar isotopic age inDongchuan Taoyuan type copper deposit, Yunnan Province and its signifi-cance: Journal of Mineralogy and Petrology, v. 24, p. 57−60 (in Chinese with English abs.).

Zhang, C.H., Gao, L.Z., Wu, Z.J., Shi, X.Y., Yan, Q.R., and Li, D.J., 2007,SHRIMP U-Pb zircon age of tuff from the Kunyang group in central Yun-nan: Evidence for Grenvillian orogeny in South China: Chinese ScienceBulletin, v. 52, p. 1517−1525.

Zhao, J.-H., and Zhou, M.-F., 2007, Geochemistry of Neoproterozoic maficintrusions in the Panzhihua district (Sichuan Province, SW China): Impli-cations for subduction-related metasomatism in the upper mantle: Pre-cambrian Research, v. 152, p. 27−47.

Zhao, J.-H., Zhou, M.-F., Yan, D.-P., Zheng, J.-P., and Li, J.-W., 2011, Reap-praisal of the ages of Neoproterozoic strata in South China: No connection with the Grenvillian orogeny: Geology, v. 39, p. 299−302.

Zhao, X.-F., 2010, Paleoproterozoic crustal evolution and Fe-Cu metallogeny of the western Yangtze block, SW China: Unpublished Ph.D. thesis, Uni- versity of Hong Kong, 192 p.

Zhao, X.-F., and Zhou, M.-F., 2011, Fe-Cu deposits in the Kangdian region,SW China: A Proterozoic IOCG (iron oxide-copper-gold) metallogenicprovince: Mineralium Deposita, v. 46, p. 731–747.

Zhao, X.-F., Zhou, M.-F., Li, J.-W., Sun, M., Gao, J.-F., Sun, W.-H., and Yang,J.-H., 2010, Late Paleoproterozoic to early Mesoproterozoic DongchuanGroup in Yunnan, SW China: Implications for tectonic evolution of theYangtze block: Precambrian Research, v. 182, p. 57–69.

Zhou, J.-C., Wang, X.-L., and Qiu, J.-S., 2009, Geochronology of Neopro-terozoic mafic rocks and sandstones from northeastern Guizhou, SouthChina: Coeval arc magmatism and sedimentation: Precambrian Research, v. 170, p. 27−42.

Zhou, M.-F., Yan, D.-P., Kennedy, A.K., Li, Y., and Ding, J., 2002, SHRIMPU-Pb zircon geochronological and geochemical evidence for Neoprotero-zoic arc-magmatism along the western margin of the Yangtze block, SouthChina: Earth and Planetary Science Letters, v. 196, p. 51−67.


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