11 isotope geochemistry and implications for ore genesis, china

8/13/2019 11 Isotope Geochemistry and Implications for Ore Genesis, China

http://slidepdf.com/reader/full/11-isotope-geochemistry-and-implications-for-ore-genesis-china 1/15

The Shanggong gold deposit, Eastern Qinling Orogen, China:Isotope geochemistry and implications for ore genesis

Yan-Jing Chen a,b, Franco Pirajno b,c,*, Jin-Ping Qi b

a Key Laboratory for Metallogenic Dynamics, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, Chinab Department of Geology, Peking University, Beijing 100871, China

c Geological Survey of Western Australia, 100 Plain Street, East Perth, WA 6004, Australia

Received 10 June 2007; received in revised form 22 October 2007; accepted 31 December 2007

Abstract

The Shanggong Au deposit in the Xiong’er Terrane, East Qinling, China, has resources of about 30 ton Au, making it one of the larg-est orogenic-mesothermal Au deposits hosted in volcanic rocks of the Mesoproterozoic Xiong’er Group. Three stages of hydrothermalactivity are recognized (early, middle and late), of which two (early and middle) were ore producing and characterized by quartz–pyriteand polymetallic sulfides, respectively. The third and late stage is represented by a carbonate–quartz assemblage. Hydrogen, oxygen andcarbon isotope systematics of the Shanggong deposit from a previous work suggest that the early stage fluids were derived from mag-matic and/or metamorphic devolatilization of sedimentary rocks at depth. This is supported by new C, S and published Sr and Pbisotopic data, presented in this paper. These new data, d13C values ranging from 1.5‰ for early stage ankerite to 2.2‰ for late stageankerite, negative d34S values for sulfides from the middle stage (–19.2 to –6.3 ‰), suggest a contribution from organic matter and thatthe ore fluid evolved from deeply sourced to shallowly sourced, with those of the middle stage representing a mixture of these two fluidsystems. The comparison of the hydrogen–oxygen–carbon–sulfur–lead–strontium isotope systematics between the Shanggong deposit

and the main lithologies in the Xiong’er Terrane, shows that neither these nor the underlying lower crust and mantle, or combinationsthereof, could be considered as the source of ore fluids for the Shanggong Au deposit. A likely source was a carbonaceous carbonate,sandstone, shale, chert sequence in the underthrusted Guandaokou and Luanchuan Groups, exposed south of the Xiong’er Terrane.

Ar–Ar and Rb–Sr isochron ages for mineral phases of the early, middle and late stages, together with geological field data, constrainthe timing of the hydrothermal activity and Au metallogenesis at 242 ± 10, 167 ± 7 and 112 ± 7 Ma, respectively. This metallogenesisand associated granitic magmatism, can be related to the continental collision between the Yangtze and North China Cratons thatresulted in the formation of the Qinling Orogen, led to the different hydrothermal systems that were responsible for the three stages thatformed the Shanggong Au deposit, over a period of about 130 Myrs. 2008 Elsevier Ltd. All rights reserved.

Keywords: Qinling Orogen; Orogenic lode; Shanggong; Isotope geochemistry; Ore genesis

1. Introduction

The Shanggong Au deposit, Henan Province (centralChina), discovered in 1982 by the No. 1 Geological Teamof the Henan Bureau of Geology and Mineral Resources

(unpublished report, 1988), has a resource of about 30ton of Au metal with ore grades averaging 6.9 g/ton Au.Since its discovery, more than 10 large (>20 ton) and med-ium (10–20 ton) Au deposits and one large Ag deposit(>1000 ton Ag) have been found in the region. Thesedeposits are mainly hosted in volcanic rocks of Paleo-Mes-oproterozoic age, with a few hosted in high-grade meta-morphic rocks of Archean-Paleoproterozoic age. Recentstudies (Mao et al., 2002; Chen et al., 2004, 2005a) showthat these Au and Ag deposits belong to the orogenic class

1367-9120/$ - see front matter 2008 Elsevier Ltd. All rights reserved.

doi:10.1016/j.jseaes.2007.12.002

* Corresponding author. Address: Geological Survey of Western Aus-tralia, 100 Plain Street, East Perth, WA 6004, Australia. Fax: +61 892223633.

E-mail address: [email protected] (F. Pirajno).

www.elsevier.com/locate/jaes

Available online at www.sciencedirect.com

Journal of Asian Earth Sciences 33 (2008) 252–266

mailto:[email protected]

mailto:[email protected]



(Groves et al., 1998; Hagemann and Cassidy, 2000; Kerrichet al., 2000; Goldfarb et al., 2001). More specifically, theShanggong Au deposit is comparable to the orogenic dis-seminated Au deposits as defined in Bierlein and Maher(2001). In this paper, we report the results of new C, S dataand published Pb and Sr isotopic studies of the Shanggong

Au deposit, which we integrated with D–O systematics andfluid inclusion studies presented in a previous study (Chenet al., 2006). The integrated isotopic data enable us to pro-pose a model of ore genesis in the context of regional geo-dynamics and associated magmatism.

2. Geological setting

The Shanggong Au deposit is hosted in volcanic rocks of the 1.8 Ga Xiong’er Group, in the Xiong’er terrane(Xiong’er Shan region; shan means mountains), HenanProvince, China (Fig. 1). The Xiong’er terrane is one of the Precambrian terranes at the southern margin of theNorth China craton and is the result of a complex tectonicevolution related to the Mesozoic continental collisionbetween the North China and the Yangtze Cratons (Hu

et al., 1988; Zhang et al., 2001; Chen et al., 2004 and refer-ences therein). This collision produced the Qinling Orogenof central China (inset in Fig. 1), which extends for morethan 2000 km, separating the North China Craton fromthe Yangtze Craton. The suture is marked by the Shang– Dan (Shangnan–Danfeng) fault and defines the southern

boundary of the northern Qinling Orogen (Fig. 1). The tec-tonic evolution of the Qinling Orogen is discussed in detailby Zhang et al. (2001) and Ratschbacher et al. (2003).

The development of the Xiong’er terrane (Fig. 2)involved three main events (Chen and Fu, 1992): (1) forma-tion of the early Precambrian crystalline basement before1850 Ma, (2) Mesoproterozoic-to-Paleozoic accretion,and (3) Mesozoic intracontinental shortening and exten-sion related to the collision between the North China andYangtze Cratons. In the east and west the terrane is cov-ered by Cretaceous to Quaternary sedimentary rocksdeposited in structural depressions. The northern part of the terrane is overthrust onto the 1300 Ma Ruyang

Group (Yin et al., 2005) along the San–Bao (Sanmenxia– Baofeng) fault (Chen and Fu, 1992). Its southern part isdelimited by the Machaoying fault.

Fig. 1. Schematic tectonic map of the eastern Qinling Orogen showing the general area of study. The major tectonic domains of China are shown in the

inset; note that the eastern part of the Central China Orogen is also known as Qinling Orogen.

Y.-J. Chen et al. / Journal of Asian Earth Sciences 33 (2008) 252–266 253



The main lithostratigraphic units of the Xiong’er ter-rane are the Taihua Supergroup (basement) and the Xion-g’er Group (supracrustals). The Taihua Supergroup iscomposed of high-grade metamorphic rocks, with agesranging from 2900 to 2200 Ma (Kroner et al., 1988; Hu

et al., 1988, 1997; Chen and Fu, 1992; Xue et al., 1995),consisting of greenstone belts and a khondalite series(sillimanite–garnet–quartz gneiss, graphite gneiss, marble,banded iron formation) (Hu et al., 1988; Chen et al.,2000b).

The Xiong’er Group, has a thickness from 3.0 to 7.6 kmand an inferred areal extent of about 60,000 km2 (Zhaoet al., 2002). It is well-preserved, unmetamorphosed tometamorphosed to lower greenschist facies, and onlylocally deformed. It is predominantly a volcanic sequencethat unconformably overlies the metamorphic basement(Taihua Supergroup) and is overlain by Mesoproterozoicrocks of the Guandakou and Luanchan Groups, repre-sented by a carbonate–sandstone–shale–chert succession,referred to in this paper as CSC, which near the Shanggongdeposit underthrusts the Xiong’er Group. The Xiong’ervolcanic rocks include basaltic andesite, dacite and rhyo-lite, with minor sedimentary intercalations and pyroclasticunits. The age of the Xiong’er Group is constrained by sin-gle and multigrain zircon populations (Sun et al., 1990).These include SHRIMP U–Pb ages from rhyolitic rocks:1826 ± 32 Ma from a single zircon, 1840 ± 14 Ma from16 zircon grains, and ages ranging from 2089 ± 12 to2511 ± 10 Ma for xenocrystic zircons. The origin of theXiong’er volcanic rocks is uncertain. Jia (1987), Hu et al.

(1988), Chen and Fu (1992), Zhao et al. (2004) consider

that these volcanic rocks may be part of an early Mesopro-terozoic continental volcanic arc, formed by the north-dip-ping subduction of the Kuanping oceanic lithosphere alongthe Heigou–Luanchuan fault. Kusky and Li (2003), on theother hand, suggested that the Xiong’er volcanic rocks are

a bimodal succession related to the opening of the Qinlingocean. This view is shared by Ren et al. (2001) and Zhaoet al. (2002), who proposed that the Xiong’er volcanicrocks were erupted in a rift setting and suggested a mantleplume origin. An overview of the Xiong’er Group isprovided by Pirajno and Chen (unpublished data, June2005 LIP of the Month, posted at www.largeigneousprovinces.org).

The above lithostratigraphic units are intruded byYanshanian (Jurassic to Cretaceous) granitoids, such asthe Huashan complex and a number of mineralized por-phyry intrusions, diatremes and breccia pipes, includingthe Qiyugou Au-bearing breccia pipes (with K/Ar agesranging from 128 to 103 Ma) and the Leimengou Au– Mo–bearing porphyries (Chen and Fu, 1992; Zhanget al., 2005; Fig. 2). The Huashan complex comprises mul-tistage granitic plutons, including the 200 km2 Haopingintrusion, the 60 km2 Wuzhangshan pluton and the Hua-shan pluton, which have zircon SHRIMP U–Pb ages of 156.8 ± 1.2, 132.0 ± 1.6, and 130.7 ± 1.4 Ma, respectively(Table 1) (Li, 2004). These Mesozoic granitic intrusionsare interpreted to be related to Mesozoic collisional tecton-ics that formed the Qinling Orogen (Chen and Fu, 1992;Chen et al., 2000a).

Numerous faults are present in the Xiong’er terrane.

Northeast-trending faults are spaced at more or less regu-

Fig. 2. Simplified geologic map of the Xiong’er Terrane showing the location of ore deposits and the Shanggong Au deposit. SBF, San–Bao fault; STF,Sanmen–Tieluping fault; KQF, Kangshan–Qiliping fault; HQF, Hongzhuang–Qinggangping fault; TMF, Taocun–Mayuan fault. Selected orogenic lodedeposits, other than Shanggong: (A) Haopinggou Ag–Pb, (B) Tieluping Ag–Pb, (C) Xiaochigou Au, (D) Kangshan Au–Ag–Pb, (E) Hugou Au, (F)Hongzhuang Au, (G) Qinggangping Au, (H) Tantou Au, (I) Yaogou Au, (J) Qianhe Au, (K) Leimengou Mo–Au, (L), Qiyugou Au. Huashan granitesuites: HP, Haoping granite; WZS, Wuzhangshan granite; JSM, Jinshanmiao granite.

254 Y.-J. Chen et al. / Journal of Asian Earth Sciences 33 (2008) 252–266

http://www.largeigneousprovinces.org/






lar intervals and spatially control the ore deposits of theXiong’er terrane (Fig. 2). The Yaogou and the QiyugouAu deposits are sited along the Taocun–Mayuan fault,with the Kangshan and the Shanggong Au deposits beinglocated along the Kangshan–Qiliping fault (Fig. 2). Struc-tural analysis (Henan Bureau of Geology and MineralResources, 1988, unpublished report) shows that theseNE-trending Au-hosting structures experienced early com-pression, followed by a tensional regime and later com-pressive shearing. All the faults in the ore field aresubsidiary to the major E–W-trending and 200 km-longMachaoying Fault, which has been active since ca.1400 Ma (Hu et al., 1988) and has been interpreted asthe trace of a north-dipping subduction zone (Chen andFu, 1992; Hu et al., 1997; Wang et al., 1997; Zhanget al., 2001). This subduction zone formed during theMesozoic collision between the Yangtze and North China

Cratons (Chen and Fu, 1992; Sui et al., 2000) and it

involved the underthrusting of the Yangtze plate beneaththe North China Craton leading to intracontinentalshortening, folding and thrusting, in a fashion similar tothe India–Tibet collision and underthrusting. We referto this subduction as A-type, in the sense of Howell(1995).

We argue that this north-dipping A-type subduction isassociated with the emplacement of Mesozoic granitoidsand the formation of the ore deposits and in the Xiong’erTerrane, as explained below.

3. Ore deposit geology and mineralization stages

The Shanggong Au deposit, contains 30 orebodieswithin a horsetail-like dilational jog (Fig. 3A). All theorebodies are located in high strain zones and are distrib-uted in a NE-trending array, about 2200 m long and

600 m wide (Fig. 3B and C). The ore zones have irregular

Table 1Isotopic ages and I Sr values of the Shanggong deposits and associated granitoids

Geologic Body Mineralogy/lithology of measured samples

Method Ma ISr Reference

Shanggong Bulk rocks of the E-stageproximal alteration

Rb–Sr isochron 242 ± 11 Li et al. (1996)

Shanggong M-stage phyllite, quartzite,

quartz-vein and pyrite–bearingsericite–quartzite

Rb–Sr isochron 165 ± 7 0.7174 ± 3 Zhang et al. (1994)

Shanggong Quartz, calcite, and sericiteseparates from L-stagegenerations

Rb–Sr isochron 113 ± 6 0.7153 ± 42 Zhang et al. (1994)

Shanggong Quartz separate from the E-stagequartz vein

Ar/Ar 222.8 ± 24.9 Ren et al. (2001)

Heyu Biotite–monzogranite Ar/Ar 132.5 ± 1.1 Han et al. (2007)Wuzhangshan Granodiorite Ar/Ar 156.8 ± 3.1 Han et al. (2007)Huashan Porphyritic alkali feldspar

granite, Wuzhangshan intrusionZircon SHRIMP 156.8 ± 1.2,

MSWD = 0.90, n = 6Li (2004)

Huashan Biotite alkali feldspar granite,Haoping intrusion

Zircon SHRIMP 130.7 ± 1.4,MSWD = 1.5, n = 14

Li (2004)

Huashan Biotite granite, Huashanintrusion

Zircon SHRIMP 132.0 ± 1.6,MSWD = 2.0, n = 4

Li (2004)

Huashan Porphyritic alkali feldspargranite, Wuzhangshan intrusion

Rb–Sr isochron 183 0.7077 HBGMR (1989)

Huashan Biotite alkali feldspar granite,Haoping intrusion


Huashan Alkali feldspar granite,Jinshanmiao intrusion


Huashan Bulk rocks and mineral separates K–Ar 159, 127, 125 HBGMR (1989)Qiyugou K-feldspar of ore Ar/Ar isochron 125 ± 3, 124 ± 4 Wang et al. (2001b)Qiyugou K-feldspar of ore Ar/Ar plateau 115 ± 2, 122 ± 0.4 Wang et al. (2001b)Qiyugou Bulk rock of the Motianling

porphyryK–Ar 125.7 ± 7.2 Ren et al. (2001)

Qiyugou Zircon of the Qiyugou porphyry U–Pb 119.6 ± 7.5 Ren et al. (2001)Qiyugou Bulk rock of quartz porphyry

dike cutting the oresK–Ar 114.7 ± 1.7 Chen and Fu (1992)

Qiyugou Bulk rock of granodioriteporphyry

K–Ar 113 ± 2 Chen and Fu (1992)

Qiyugou K-feldspar formed by potassicalteration

K–Ar 121 ± 2 Chen and Fu (1992)

Qiyugou K-feldspar formed by potassicalteration

K–Ar 148 Ren et al. (2001)

Qiyugou Pyrite of the ore Ar/Ar 103 Ren et al.(2001)




and gradational borders, depending on cut-off grades, but

are commonly more or less lenticular or tabular, both inplan and section views. Orebodies are usually within silici-fied zones that contain thin (mostly > 1 mm) quartz veins.These veins have brecciated, mylonitic and banded struc-tures and form stockworks, disseminated veinlets andlocally massive veins. The Shanggong orebodies are later-ally zoned, from the centre outward: a Au–bearingsulfide–quartz–ankerite–sericite zone (usually 1 to 3 mwide; > 3g/ton Au), a 1–20-m wide pervasively altered pyr-ite–carbonate–sericite–chlorite–epidote zone (0.5–3 g/tonAu), grading outward to a ca. 50 m-wide of weakly alteredpyrite–carbonate–sericite–chlorite–epidote zone (<1 g/tonAu), and finally unaltered country rock of the Xiong’erGroup (ca. 0.7 ppb Au; Chen and Fu, 1992). No verticalzoning has been observed.

The gangue and ore mineral associations are complex.Gangue minerals comprise quartz, ankerite and sericite(>5 vol%), chlorite, epidote and fluorite (0.1–5 vol%), withlesser (<0.1 vol%) calcite, kaolinite, smectite, albite, apa-tite, and tourmaline. Major ore minerals are pyrite(>5 vol%) and galena (0.1–5 vol%). Other minerals(<0.1 vol%) include magnetite, hematite, chalcopyrite,sphalerite, wolframite, scheelite, chalcocite, tetrahedrite,argentite, bornite, pyrrhotite, molybdenite, native Au, elec-trum, calaverite, hessite, petzite, altaite, melonite, colora-

doite, horobetsuite, and siderite. In addition, limonite,

jarosite, cerusite, anglesite, covellite, malachite, azurite,

and hydrocerussite can be observed in the weathering zone.Based on field data, petrographic observations and tex-

tural relationships, the mineralization and alteration can bedivided into: early (E), middle (M) and late (L) stages. TheE-stage is further subdivided into an older substage charac-terized by sericite, albite, quartz, ankerite, chlorite, epidote,pyrite, and minor tourmaline, which form infills or replacesfine-grained (<2 mm) minerals, and a younger substage, of coarse-grained, milky quartz veins (generally tens to hun-dreds of centimeter thick) that contain ankerite, coarse-grained cubic pyrite, and locally, fluorite, scheelite, wol-framite, and molybdenite. The alteration assemblages andveins of E-stage are locally mylonitized with developmentof corona-like textures. The M-stage is characterized bystockworks of pyrite, galena, sphalerite, chalcopyrite, tetra-hedrite, and minor tellurides and native elements (Au, Ag,Cu, and Te). M-stage gangue minerals include quartz, chlo-rite, sericite, epidote, and ankerite, which also filled thebrecciated E-stage coarse-grained milky quartz veins. TheM-stage minerals are fine-grained, including fine-grainedpentagonal dodecahedron pyrite and quartz and do notshow any deformation. The L-stage is dominated byquartz–carbonate veinlets (1 to 30 mm thick in general),locally associated with chlorite, sericite, and fluorite. TheseL-stage veinlets penetrate fracture zones in the country

rocks and quartz crystals typically grew from both walls

Fig. 3. Structurally-controlled Au orebodies and associated alteration zones (modified after Henan Bureau of Geology and Mineral Resources, 1988,unpublished). (A) The Shanggong Au deposit is located in a horsetail-like dilational jog of the Kangshan–Qiliping fault system. (B) At the 1111 m level,the dilational fracture splays control the alteration and ore occurrence. (C) A profile along No. 27 exploration line, showing the vertical geometry of theorebodies and surrounding altered wallrocks. Roman numerals in (B) and (C) indicate the six main ore-hosting tectonite zones.




towards the center, which is filled with calcite crystals. It ispertinent to note that E-stage anhedral quartz with undu-lose extinction, was replaced by L-stage euhedral quartzwith no undulose extinction.

4. Isotope geochemistry

Hydrogen and oxygen isotope systematics and the geo-chemistry of ore fluids from the Shanggong Au depositshave been reported by Chen et al. (2006) and are summa-rized below. In this contribution, we present new S, C iso-topic data, integrated with published Pb and Sr data.

4.1. Samples and analytical methods

Sampling was carried out taking into account the fieldrecognition of the previously mentioned lateral zonation.Samples used for isotope analyses were selected from 462

specimens by using microscopy to confirm which minerali-zation stage they represented. More than 15 mg of clearmineral grains were picked out for every sample under bin-ocular microscope. However, it was difficult to obtainquartz and carbonate mineral separates from M-stage sam-ples, due to the very fine grain size. In order to eliminateother interlocking minerals (e.g. sulfides), quartz separateswere treated with HNO3 solution at 60–80 C for 12 h andrinsed with deionized water. Then the separates were trea-ted 6 times using supersonic centrifugal clarifier and rinsedby deionized water over a week. The last rinsed water wasmonitored by WFX-110 atomic absorption spectropho-tometer to confirm that no ions were left. The samples were

dried in an oven at 120 C before analysis.Carbon isotopic analyses were made from CO2 liberated

from powdered carbonates using 100% phosphoric acid, orreleased from fluid inclusions in quartz separates by ther-mal decrepitation. Carbon dioxide was collected, con-densed and separated in a liquid nitrogen–alcohol coolingtrap (70 C) for d13C mass spectrometry analysis.

The d34S of sulfide was determined on SO2 obtained byplacing the sulfide–CuO composite (at weight ratio of 1/7)into a vacuum system heated to 1150 C.

Carbon and sulfur isotopes were measured using a Finn-igan MAT251 mass spectrometer in the State Key Labora-

tory of Endogenetic Deposits, Nanjing University. Isotopicdata were reported in per mil relative to the Canyon Diablo

triolite (CDT) standard for sulfur and the Peedee Belem-nite limestone (PDB) standard for carbon. Total uncertain-ties were estimated to be better than ± 0.2‰ for d34S, and± 0.2‰ for d13C.

4.2. Carbon

Five d13C values for ankerite separates (Table 2) range

from 2.2‰ to 1.5‰, (average 0.8‰), and whereas threed13CCO2 values for inclusion fluids released from M-stage

quartz separates (Table 2) range from 1.2‰ to 0.5‰(average 0.2‰). These values are higher than thoseexpected for organic matter (27‰), atmospheric CO2

(7‰ to 11‰; Hoefs, 2004), fresh water bicarbonate(9‰ to 20‰: Hoefs, 2004), or from igneous rocks(3‰ to 30‰: Hoefs, 2004; Zheng, 1999), continentalcrust (7‰: Faure, 1986) and the mantle (5‰ to 7‰:Hoefs, 2004). We suggest that the most likely source of car-

bon in ankerite is CO2 derived from metamorphic decar-bonation of marine carbonates, which have d13Cankerite

values close to 0.5‰ (Schidlowski, 1998). Therefore, weinterpret the high d

13C values of the Shanggong ankeriteto reflect decarbonation of the marine carbonates of theunderthrust Guandaokou and Luanchuan groups.

Qi et al. (2005) recently reported four d13CCarbonate val-ues for these rocks, which range from 2.8‰ to 0.8‰(average 0.9‰). According to fractionation factors fordolomite–CO2 and calcite–CO2 from Sheppard and Schw-arcz (1970) and Chacko et al. (1991), metamorphic temper-atures of 400 C, the 103lnadolomite-CO2 and 103lnacalcite-CO2

are 1.8 and 1.9, respectively. This means that the

d13CCO2 values of metamorphic fluids equilibrated withthe CSC sequence at 400 C, would be in the range of – 1‰ to 2.7‰, similar to the measured d

13C of ankerite inthe Shanggong ore system (Table 2). The d

13C values forankerite decrease from E-stage (1.5‰), through M- or L-stage (0.0‰), to L-stage (1.6‰ to 2.2‰) (Table 2). Thisgradual decrease in d

13C values follows a decrease ind13CCO2 values of ankerite from E-stage to L-stage. Two

possibilities can be considered to explain the d13C decrease.

One is an input of low-d13C fluids, which is consistent withthe O and H data on the hydrothermal fluids and theconclusions obtained from fluid inclusion studies (Chen

et al., 2006) that indicate the late involvement of meteoricwater. Another possibility is the continuing metamorphic

Table 2The d13C (‰, PDB) values in ankerite separates from the Shanggong deposit

No. Details of samples (Nos. or location) d13C d

13CCO2 Stage

1 Ankerite from ankerite–bearing quartz vein (PD1ym1bt2) 1.5 E2 Ankerite from ankerite cement of breccia ore (DF2-0) 0.0 M+L3 Ankerite from ankerite net–vein (PD1-23) 2.2 L4 Ankerite from ankerite–quartz net vein (PD3cm6df1) 1.9 L5 Ankerite from Galena–bearing ankerite net vein (PD1ym1cm4c2) 1.6 L6 Fluid in quartz separate from M-stage sulfide aggregate (S2-1) 0.1 M7 Fluid in quartz separate from M-stage sulfide aggregate (S1-2) 0.5 M

8 Fluid in quartz separate from M-stage sulfide aggregate (S12-1)

1.2 M




Table 3The d34S values (‰, CDT) in minerals from the Shanggong deposit and its related rocks

Sample Mineral d34S Stage

1 Medium cubic pyrite in milky quartz lenticular vein Pyrite 6.0 E2 Medium cubic pyrite in altered andesite Pyrite 4.2 E3 Medium cubic pyrite in altered andesite Pyrite 4.1 E4 Cubic pyrite in milky quartz vien (SH-13) Pyrite 2.11 E

5 Medium cubic pyrite in milky quartz lenticular vein Pyrite 3.01 E6 Chalcopyrite in milky, quartz lenticular vein Chalcopyrite 6.7 E

Average (6 samples, 2.1–6.7) 4.3 E

7 Fine pentagonal dodecahedron pyrite in breccia ore Pyrite 11.3 M8 Fine pentagonal dodecahedron pyrite in breccia ore Pyrite 13.2 M9 Fine pentagonal dodecahedron pyrite in breccia ore Pyrite 10.7 M10 Fine pentagonal dodecahedron pyrite in breccia ore Pyrite 12.0 M11 Fine pentagonal dodecahedron pyrite in breccia ore Pyrite 14.6 M12 Fine pentagonal dodecahedron pyrite in fluorite–pyrite ore Pyrite 10.9 M13 Fine pentagonal dodecahedron pyrite in pyrite–galena ore Pyrite 7.8 M14 Fine pentagonal dodecahedron pyrite in disseminated ore Pyrite 6.5 M15 Fine pentagonal dodecahedron pyrite in disseminated ore Pyrite 11.3 M16 Fine pentagonal dodecahedron pyrite in breccia ore Pyrite 10.5 M17 Fine pentagonal dodecahedron pyrite in banded ore Pyrite 10.6 M

18 Fine pentagonal dodecahedron pyrite in breccia ore Pyrite 13.1 M19 Fine pentagonal dodecahedron pyrite in breccia ore Pyrite 11.41 M20 Fine pentagonal dodecahedron pyrite in breccia ore Pyrite 11.11 M21 Fine pentagonal dodecahedron pyrite in breccia ore Pyrite 12.01 M22 Fine pentagonal dodecahedron pyrite in breccia ore Pyrite 9.11 M23 Fine pentagonal dodecahedron pyrite in breccia ore Pyrite 11.61 M24 Fine pentagonal dodecahedron pyrite in breccia ore Pyrite 6.31 M

Average (18 samples, 14.6 – 6.3) 10.8 M

25 Polymetallic sulfide–bearing breccia ore Galena 16.6 M26 Massive galena ore Galena 15.9 M27 Galena–bearing ankerite net–vein Galena 19.2 M28 Polymetallic sulfide breccia ore Galena 17.0 M29 Polymetallic sulfide breccia ore Galena 13.0 M30 Polymetallic sulfide breccia ore Galena 19.2 M31 Galena–bearing ankerite net–vein Galena 13.4 M32 Polymetallic sulfides disseminated ore Galena 14.5 M33 Polymetallic sulfides disseminated ore Galena 16.21 M34 Polymetallic sulfides disseminated ore Sphalerite 13.9 M

Average (10 samples, 19.2 – 13.0) 15.9 M

35 Galena–bearing carbonate net–vein Galena 0.8 L36 Galena–bearing carbonate net–vein Galena 1.5 L37 Pyrite–bearing quartz–calcite net–vein Pyrite 0.91 L

Average (3 samples, 0.78–1.51) 1.1

38 Volcanic rock of Xiong’er Group Pyrite 3.61

39 Amygdaloidal andesite (SH6-3) Pyrite 4.31

40 Amygdaloidal andesite (SH-22) Pyrite 4.61

41 Megaphyric amygdaloidal andesite of the Xiong’er Group Pyrite 2.51

42 Andesite of the Xiong’er Group Pyrite 5.41

Average of Xiong’er Group (5 samples, 2.5–5.4) 4.1

43 Biotite-plagioclase gneiss (GPDF4s), Taihua Supergroup Pyrite 5.71

44 Plagioclase amphibolite (SbDF1), Taihua Supergroup Pyrite 2.91

45 Plagioclase amphibolite (GDF43), Taihua Supergroup Pyrite 2.91

46 Plagioclase amphibolite (FH665), Taihua Supergroup Pyrite 1.31

Average of Taihua Supergroup (4 samples, 1.3–5.7) Pyrite 3.2

47 Haoping granite Pyrite 2.31

48 Adamellite (FH052) Pyrite 2.31

49 Adamellite (HDF3) Pyrite 1.81

50 Biotite granite (HDF2) Pyrite 5.41

Average of Huashan complex (4 samples, 1.8–5.4) 3.0

The samples were collected by the authors and Shimei Li, and were analyzed in the State Key Laboratory of Endogenetic Deposits, Nanjing University.Data marked with ‘‘1” were cited from Fan et al. (1994).




decarbonation that can result in the decrease of d13C andd18O, in both the generated CO2 and residual carbonate

from early to late stages (Valley, 1986). This possibility,however, is not supported by fluid inclusion studies (Chenet al., 2006).

4.3. Sulfur

The d34S values for the Shanggong Au deposit ore min-erals as well as sulfides from rocks of the Taihua Super-group and Mesozoic granites are listed in Table 3. Thed34S values range from 19.2‰ to 6.7‰ and show a bimo-

dal distribution (Fig. 4). The E-stage sulfides have positived34S values (average 4.3‰), which are very similar to the

rocks of the Xiong’er Group (Fig. 6, average 4.1‰). There-fore, we argue that the Xiong’er Group contributed muchof the sulfur to the E-stage sulfides during fluid–rock inter-action. This interpretation is also consistent with the obser-

vations that the E-stage sulfides are disseminated in thealtered andesites and in lenticular quartz veins and the E-stage alteration and veining are characteristic of pervasivefluid–rock interaction within high strain zones.

The d34S values of 28 samples of the M-stage pyrite,

galena, and sphalerite range from –19.2 to –6.3‰ (Table

3) and are quite different from the d34S values of both

the E- and L-stage sulfides. This wide d34S variation

shows that the S-isotope fractionations, among coexistingpyrite, galena, and sphalerite, were not equilibrated, prob-ably due to rapid precipitation of the M-stage minerals.The negative d

34S values were previously interpreted to

have resulted from relatively oxidized fluids (Zhang,1989; Fan et al., 1994). However, the M-stage mineralassemblage, which contains native metallic elements, indi-cate that the M-stage sulfides were reduced, relative to theE- and L-stage fluids. In the Xiong’er terrane, only theCSC sequence of the Guandaokou and LuanchuanGroups contains organic material, which can be consid-ered as a possible source of the biogenic sulfur of theShanggong hydrothermal system. The average d

34S valueof sulfides of the L-stage is 1.1‰, suggesting that thissulfur may have been sourced either from igneous rocksor from the immediate host rocks by meteoric watercirculation.

4.4. Isotopic data from previous work

4.4.1. Lead

Table 4 lists Pb isotope ratios for the Shanggong Audeposit and associated rocks (Henan Bureau of Geologyand Mineral Resources, 1988; Henan Institute of Geology,1985). In Fig. 5, the ore samples from the Shanggongdeposit show a wide scatter, probably reflecting interactionor mixing of ore-forming fluids with rocks of the Xiong’erGroup. This is supported by the fact that the Pb isotopecompositions of altered andesite lie between those of ores

and unaltered andesite (Fig. 7a and b). However, comparedto the ores, the rocks of the Xiong’er Group have lower207Pb/204Pb, 208Pb/204Pb and 206Pb/204Pb ratios, which ruleout the possibility that the ore lead was derived from theXiong’er Group rocks.

The rocks of the Taihua Supergroup are less radiogenicthan the ores of the Shanggong deposit (Fig. 7a) and couldnot have provided the ore Pb in the deposit. The Pb isoto-pic composition of the Shanggong deposit is close to orslightly less radiogenic than that of the Yanshanian grani-toids (including the Huashan complex and Qiyugou por-phyry belt). The latter are similar in composition to theMesozoic granitoids of the southern margin of the NorthChina craton (Table 4 and Fig. 5a and b). This may indi-cate either that the ore metals were sourced from the gra-nitic magmas or that they have the same Pb-source as thegranitoids. The Qiyugou porphyries have lower207Pb/204Pb and higher 208Pb/204Pb ratios than the Hua-shan Complex (Table 4, Fig. 5), suggesting a deeper sourceof lead for the Qiyugou porphyries.

The lower crust and the mantle beneath the Xiong’erterrane would have less radiogenic Pb than the TaihuaSupergroup and the Xiong’er Group, which rules out thepossibility of the lower crust and/or mantle as a sourceof the ore lead. Thus, a possible source of lead is in the

upper crust.

Fig. 4. Histogram of d34S for the Shanggong Au deposit and associatedlithologies (data listed in Table 3). The Taihua Supergroup, Xiong’erGroup and Huashan Complex have similar d34S values due to theirigneous lithologies. The d34S values of E- and L-stages sulfides of the oresare similar to those of the wallrocks, the Xiong’er Group, showing thecontribution of the wallrocks. The M-stage sulfides have negative d

34Svalues suggesting a source characteristic of biogenic sulphur, and

contrasting to the main lithologies in the Xiong’er terrane.




4.4.2. Oxygen–hydrogen systematicsChen et al. (2006) found that the ore fluid’s dD and d

18Ovalues were higher than the Xiong’er Group and that d18Ovalues systematically increase from unaltered volcanicrocks (6.7–8.0‰), through altered volcanic rocks (8.5– 8.9‰) to ores (12.7‰), suggesting that 18O is added tothe wall rocks during fluid–rock interaction. Calculated18OW values for E-stage fluids average 8.1‰, which is inthe range of metamorphic water (Fig. 6). dD values forinclusion fluids of E-stage mineral separates range from66‰ to 88‰ and in Fig. 6 the data plot in the magmaticbox and below the metamorphic water box. Chen et al.(2006) concluded that the E-stage fluids show characteris-tics of magmatic and/or metamorphic fluids. Calculatedvalues of d18Ow of L-stage fluids range from 2.4‰ to1.1‰. These low values show that the L-stage fluids hada large meteoric water component. In addition, the dDH2O

value of the L-stage fluid, extracted from fluid inclusionsin fluorite, is 56‰, which together with the d18Ow value,would plot towards the meteoric water line (Fig. 6).

Three d18OW values for M-stage fluids range from 1.9‰ to

4.5‰, are intermediate between those for E-stage (8.1‰)andL-stage (2.4‰ to1.1‰). This trend may be interpreted toindicate a mixing of deep-sourced metamorphic fluids withmeteoric water. In Fig. 6, the M-stage samples plot between

the E- and L-stages fluid boxes. However, dDW values of

M-stage fluids range from 113‰ to 94‰, average103‰, lower than those of the E- and L-stage fluids.

4.4.3. Strontium

Analysis of the Huashan Complex yielded initial87Sr/86Sr ratio values of 0.7077, 0.7072, and 0.7074 (Table1 and references cited therein), within the range of grani-toids in East Qinling area (0.705 to 0.714; Chen et al.,2000a). Two Sri values for altered rocks of the ShanggongAu deposit are 0.7153 and 0.7174 (Table 1), which arehigher than those of the Mesozoic granitoids (e.g., theHuashan Complex), and the lower crust and mantlebeneath the Xiong’er Terrane, considering that the grani-toids came from a source no shallower than middle crust.This suggests that the ore metals by a source in the uppercrust and/or supracrustal rocks, having Sri values > 0.714.

5. Genetic model of the Shanggong Au deposit

5.1. Geochronological constraints and timing of

metallogenesis

The isotopic ages for the Shanggong Au deposit, gra-nitic rocks and Qiyugou porphyry system are listed inTable 1. The L-stage sericite, quartz and calcite yielded a

Rb–Sr isochron age of 113 ± 6 Ma (Zhang et al., 1994).

Table 4Lead isotope composition of ores and related rocks; data from Henan Bureau of Geology and Mineral Resources (HBGMR) (1988) and Henan Instituteof Geology (HIG) (1985)

Geology of samples Sample site Mineral 206Pb/204Pb 207Pb/204Pb 208Pb/204Pb Reference

Galena-rich ore Shanggong Galena 17.095 15.387 37.502 HBGMR (1988)Breccia ore Shanggong Galena 17.053 15.344 37.417 HBGMR (1988)Disseminated ore Shanggong Galena 17.208 15.503 37.949 HBGMR (1988)

Breccia ore Shanggong Galena 17.105 15.384 37.558 HBGMR (1988)Breccia ore Shanggong Galena 17.188 15.508 37.938 HBGMR (1988)Breccia ore Shanggong Galena 17.119 15.393 37.566 HBGMR (1988)Galena–ankerite net–vein Shanggong Galena 17.085 15.367 37.474 HBGMR (1988)Polymetallic sulfide ore Shanggong Galena 16.378 15.355 36.426 HBGMR (1988)Polymetallic sulfide ore Shanggong Galena 17.283 15.615 38.168 HIG (1985)Ore Shanggong Galena 17.132 15.415 37.644 Fan et al., 1994Pyrite–galena ore Weijiagou Galena 17.226 15.344 37.295 HBGMR (1988)Limonitized galena ore Qiliping Galena 17.273 15.420 37.677 HBGMR (1988)Polymetallic sulfide ore Qiliping Galena 17.344 15.436 37.971 HIG, 1985Polymetallic sulfide ore Qiliping Galena 17.615 15.406 38.024 HIG, 1985Breccia ore Ganshuwo Galena 17.136 15.402 37.642 HBGMR, 1988Average (n = 15) 17.149 15.419 37.617

Granitic porphyry dike Qiyugou Rock 17.271 15.278 37.265 Cui (1991)

Granitic porphyry dike Qiyugou Rock 17.926 15.415 38.075 Cui (1991)Granitic porphyry dike Qiyugou Rock 17.562 15.344 37.822 Cui (1991)Granitic porphyry dike Qiyugou Orthoclase 17.415 15.379 37.674 Cui (1991)Granodiorite Leimengou Rock 17.476 15.454 37.936 Fan et al. (1994)Average porphyry (n = 5) 17.530 15.374 37.754

Aver granite (n = 7) Huashan 17.355 15.411 37.647 Chen et al. (2004)Mesozoic granitoids (n = 26) Huaxiong Block Feldspar 17.470 15.427 37.799 Zhang et al. (2002)Avg. gneiss (n = 8; TC) Taihua SGp. Rock 17.034 15.274 38.295 Chen et al. (2004)Avg. migmatite (n = 2;TZ) Taihua SGp. Rock 16.635 15.198 36.572 Zhang et al. (2002)Avg. basalt (n = 2; XZ) Xiong’er Gp Rock 16.279 15.300 36.047 Zhang et al. (2002)Avg. andesite (n = 3; XF) Xiong’er Gp Rock 16.664 15.331 36.570 Fan et al. (1994)Altered andesite (n = 1) Xiong’er Gp Rock 17.116 15.405 37.345 Fan et al. (1994)




Rubidium–Sr isochron ages of bulk rocks hosting E-stageand M-stage veins, yielded 242 ± 11 and 165 ± 7 Ma,respectively (Li et al., 1996; Zhang et al., 1994). Graniteplutons of the Huashan Complex, i.e. the Wuzhangshan,Heyu, Haoping and Jinshanmiao granites, yielded Rb–Srisochron ages of 183, 123, and 105 Ma (no errors reported),respectively (Henan Bureau of Geology and MineralResources, 1989; Table 1) and Ar/Ar ages of 156.8 ± 3.1and 132.5 ± 1.1 Ma (Wuzhangshan and Heyu, respectively;Han et al., 2007). These ages are in agreement with thecrosscutting relations between the Taochun–Mayuan andKangshan–Qiliping faults and the intrusions of the Hua-shan suite (Fig. 2), and confirm that the Huashan graniteswere emplaced during the Yanshanian Orogeny. Isotopicages for the Qiyugou porphyry belt range from 148 to103 Ma (Table 1), falling into the time-span of Early Cre-taceous and accord with the Rb–Sr isochron age for the

L-stage minerals from the Shanggong deposit.

5.2. Geodynamic evolution and metallogenesis

There remain unanswered questions regarding the gene-sis of orogenic lode deposits (Groves et al., 1998; Kerrichet al., 2000; Hagemann and Cassidy, 2000; Goldfarbet al., 2001), such as the relationship to coeval graniticmagmatism, the geodynamic regime, and the fluid andmetal sources. Answers to these questions are necessaryin order to understand the ore-forming processes, and to

develop well-constrained models of ore genesis.Age constraints suggest that the origin of the ShanggongAu deposit is related to the collision between the NorthChina and Yangtze continental plates and subsequent ther-mal relaxation and extension. This collision formed theQinling Orogen, which now marks the suture between theNorth China and Yangtze cratons. The Qinling Orogen isthe result of a complex geodynamic history, includingdivergence and convergence of continental blocks, span-ning a period from the Late Neoproterozoic to the Creta-ceous (Zhang et al., 2001; Ratschbacher et al., 2003).Chen and Fu (1992), Chen (1998), Chen et al. (2004,2005a,b) interpreted the latest phases in the geodynamicevolution of this orogen to have occurred in three stages:(1) an early compressive stage, during the Triassic to mid-dle Jurassic; (2) a transitional stage from compression toextension in the late Jurassic to early Cretaceous; and (3)a late extensional stage in the Cretaceous. The recognitionof these three tectonic stages is based on the following.

Intracontinental or A-type subduction (Howell, 1995),deformation and foreland thrusting of turbidites occurredduring the Late Triassic and Jurassic (Xu et al., 1986; Huet al., 1988; Li et al., 1999; Zhang et al., 2001; Ratschbach-er et al., 2003). A paleomagnetic study (Zhu et al., 1998)shows that the Yangtze and North China Cratons were sep-

arated before the Triassic and sutured during the Triassic,

Fig. 5. Plots of lead isotopic ratios for the Shanggong Au deposit. Data

listed in Table 4 and reference lines based on Zartman and Doe (1981).The close plots of ores, Mesozoic granitoids and porphyries suggest auniform source. In Fig. 7A the ores plot righter and higher than theTaihua Supergroup and Xiong’er Group, ruling out the possibility that theore lead were mainly sourced from these lithologies. The altered Xiong’erGroup andesite (wallrock) plots between the ores and the unalteredsamples of the Xiong’er Group, suggesting an exchange in Pb isotopesduring fluid–wallrock interaction.

Fig. 6. dD versus d18O of ore-forming fluids of the Shanggong Au deposit(from Chen et al., 2006). Domain of E-stage fluids is defined according tothe maximum and the minimum values. Arrow indicates evolutionary pathof fluids from E-, through M- to L-stages.




and that their relative positions have not changed since themiddle Cretaceous. This indicates that crustal shorteningand thickening occurred between the Triassic and EarlyCretaceous (Zhu et al., 1998). Studies of metamorphicPTt-path and magmatic evolution of the Qinling–DabieOrogen suggest that the most extensive granitic magma-

tism, generation of hydrothermal fluids and metallogenesistook place in response to lithospheric delamination andassociated rising geothermal gradients, during Late Juras-sic–Early Cretaceous time (Li et al., 2001).

The timing of metallogenesis and its relationship to theMesozoic tectonic evolution shows that the Shanggong Audeposit was formed during geodynamic processes from col-lisional compression to extension in the Mesozoic. Thisinterpretation is in agreement with the following keyaspects of the Shanggong deposit: (1) decrease in regionalpressure and temperature from early to late stages (Fanet al., 1998), probably related to uplift and mountain-build-ing; (2) Au-hosting structures changed from reverse faults

in the Triassic to tensional in the Jurassic–Cretaceous; (3)ore fabrics changed from E-stage compressive shearing toL-stage open space filling textures, quartz changed fromE-stage anhedral and stressed crystals to L-stage unstressedeuhedral crystals; (4) ore-forming fluids changed frommagmatic and/or metamorphic to meteoric water domi-nant; and (5) the composition of Mesozoic granitoids inthe Xiong’er Terrane changed from peraluminous to K-rich and K-feldspar porphyritic calc-alkaline series (Huet al., 1988; Chen and Fu, 1992; Chen et al., 2000a).

5.3. Sources of ore fluids and metals

The Huashan Complex, Xiong’er Group and TaihuaSupergroup and their underlying lower crust and mantlewere assumed to be the source of the ore fluids and metalsfor the Shanggong Au deposit (e.g. Hu et al., 1988, 1997;Cui, 1991; Fan et al., 1998; Li et al., 1996 ). However, thecomplexity and the effects of isotope and chemicalexchange during fluid–rock interactions makes most iso-tope tracers non-diagnostic in terms of sources of metalsand fluids (Kerrich et al., 2000; Hagemann and Cassidy,2000). Indeed, in any large scale hydrothermal system allrocks that interact with the fluids are likely to contributevarious amounts of metals and isotopes to the system.Whilst we acknowledge the inherent difficulty in pinpoint-ing a specific source, we draw attention to the following.Sui et al. (2000), Wang et al. (2001a) and Chen et al.(2004, 2005b, 2006) on the basis of isotope systematics of H, O, C, S, and Pb proposed that carbonate–bearing sedi-mentary rocks containing biogenic matter could be a likelysource of fluids and metals, even though the ore-bodies arehosted in volcanic rocks of the Xiong’er Group or the Tai-hua Supergroup. Since there is no significant sedimentaryrock component in the volcanic-dominated Xiong’er Ter-rane, we infer that deep-seated sedimentary rocks of theGuandaokou and Luanchuan Groups south of the Mach-

aoying fault may have been the sources of fluids and some

of the metals, with Au perhaps being sourced from themafic rocks of the Xiong’er Group (Fig. 2).

The H–O isotope data of Chen et al. (2006) and ourd13C data suggest that the ore fluids of Shanggong Au

deposit were derived from devolatilization of a source withhigh d

18O and d13C. The possibility of the Xiong’er Group

as fluid and metal source is precluded by its low-d18

O (6.7to 8.0) and low-d13C (likely around 5‰ because of its vol-canic lithology) and insufficient concentration of carbon.The Xiong’er Group is also ruled out because it has lowervalues of Sri,

207Pb/204Pb, 208Pb/204Pb, and 206Pb/204Pbthan the Shanggong ores.

The strongest metamorphism and devolatilization of theTaihua Supergroup occurred before 1850 Ma (Hu et al.,1988; Chen and Zhao, 1997), whereas the metallogenesisof the Shanggong deposit occurred within the time spanof from 250 to 110 Ma. The lower values of d18O, Sri,207Pb/204Pb, and 206Pb/204Pb and higher values of 208Pb/204Pb and dD of the Taihua Supergroup relative to

the ores of the Shanggong deposit confirm that rocks of the Taihua Supergroup could not have been the source of fluids, as previously discussed. On the other hand, Cui(1991) and Li et al. (1996) also considered that the Shang-gong deposit and the Qiyugou–Leimengou porphyry Au– Mo ore belt were the results of late differentiation of theHuashan Complex, based on their similarity in Pb isotoperatios and their spatial association. In addition, the Sri val-ues of the ore are higher than those of the Huashan Com-plex, and the dD, d18O, d13C and d

34S values of the orefluids or ores are different from those possibly evolved fromthe Huashan Complex.

5.4. Metallogenic and geodynamic model for the Shanggong

Au deposit

We propose that the origin of the Shanggong Au depositis related to Mesozoic collision tectonics and uplift (Yansh-anian orogeny), thereby including it within the orogenicclass, as defined by Groves et al. (1998) and Goldfarbet al. (2001). We envisage that the major inflow of fluids,especially E-stage, was probably derived from the meta-morphic devolatilization of sedimentary rocks at depth.Questions such as, how can the metallogenesis of theShanggong Au deposit be genetically linked to Mesozoiccollision, when did devolatilization of sedimentary rockoccur, why the fluids evolved from deep-sourced to mete-oric water dominant, and why is the main mineralizationassociated with M-stage, can be reasonably answered bycalling upon a metallogenic model linked to A-type sub-duction (Chen and Fu, 1992; Chen and Pirajno, 2005).A-type subduction (Howell, 1995) involves a subductingplate with continental lithosphere underthrusting an over-riding continent, with crustal shortening, mountain build-ing, and imbricate stacking of crustal slices. This isfollowed by extensional collapse, perhaps due to the incep-tion of a thermal anomaly associated with lithospheric

delamination and asthenospheric upwelling (Qiu and




Groves, 1999; Li et al., 2001; Chen et al., 2005a; Pirajnoand Chen, 2005). A classic modern example of a collisionalorogen is provided by the Alpine–Himalayan mountainranges (see Windley, 1995, for a comprehensive overview;O’Brien, 2001, for the specific example of the Alpine andHimalayan collisional orogens, and Goldfarb et al., 2001,

for an overview of collisional orogens and their linkagewith orogenic Au mineralization).The Mesozoic collision between the Yangtze and North

China continents, re-activated a series of pre-existingfaults, including the Machaoying fault, which wereinvolved in a north-dipping A-type subduction zone (Yuanet al., 2002; Chen et al., 2000a; Zhang et al., 2001)(Fig. 7A). PTt paths indicate that, in general, continentalcollisions evolve from an early compressive stage, througha transitional compression-to-extension stage, to a finalstage characterized by extensional tectonics (Jamieson,1991; Fig. 7B).

In the early compression stage (Fig. 7B), the CSC

sequence (Guandaokou and Luanchuan Groups) was sub-

ducted northwards beneath the Xiong’er Terrane (Fig. 7C).The temperature and pressure of the subducting slabincreased with depth, resulting in metamorphism and par-tial melting of the subducted materials (G1 syncollisionalperaluminous granites; Fig. 7C1). Water, other volatiles(e.g. CO2), silica, and organic matter were mobilized during

devolatilization processes forming metamorphic fluids,which moved upward together with some ore-forming ele-ments (e.g. Te). These fluids also mobilized and extractedore elements (e.g. Au) from the wallrocks (e.g. the Xiong’erGroup) during their upward movement. When the fluidsreached favorable sites, e.g. lithological discontinuities,dilatant fault-jogs and the ductile-to-brittle transitions(Cox et al., 2001; Streit and Cox, 2002), the ore-formingcomponents were precipitated. This is the E-stage in themineralization paragenesis of the Shanggong Au deposit.

During the transition stage, P–T conditions (from P max

to T max, i.e., decompression–rising geotherms, possibly dueto upwelling asthenospheric mantle) (Fig. 7B) resulted in

decompression melting in the deep levels, providing energy,

Fig. 7. Metallogenic model for the Shanggong Au deposit and its relationship to regional geodynamics. (A) Simplified tectonic structure of the QinlingOrogen from Chen (1998), inferred from geophysical and structural studies by Yuan et al. (2002), Zhang et al. (2001), Xu et al. (1986) and Hu et al. (1988),showing that the faults within Qinling Orogen are shallower than the Moho discontinuity. (B) Typical PTt-path of collisional orogens, modified afterJamieson (1991), showing the three different geodynamic regimes (compression, transition to extension, extension of the collision process), which areresponsible for fluid generation, large-scale fluid flow, metallogenesis and magmatism. (C) Schematic diagram illustrating the regional tectonothermal,fluid flow and ore-forming processes, the position of the Kangshan–Shanggong hydrothermal Au–Ag belt and its spatial and temporal relationships tosubduction, ore-hosting structures, various generations of granitoids (G1, G2, G3; see text for details) and the Qiyugou Au–bearing breccia pipes. C1, C2and C3 correspond to compression (crustal thickening, shortening), transition (uplift and beginning of extension) and final extensional stages as shown in

(B), respectively. See detailed discussion in text.




fluids for metallogenesis and melts (G2 metaluminousgranites; Fig. 7C2). Structures would dilate due to regional(terrane- or orogen-scale) decompression and uplift,providing good conduits for fluid circulation. Theseupward-flowing, deeply-sourced, fluids would mix withthe downward-flowing, shallow-sourced, fluids in fractures

and other favorable loci (Fig. 7C2). Upon mixing, theupward-flowing deep-sourced fluids and the downward-flowing shallow-sourced fluids change their physicochemi-cal character, depositing ore-forming elements rapidly,resulting in the most intensive mineralization that is char-acteristic of the M-stage.

During the late extensional stage and thermal relaxation(after T max; Fig. 7B), heat energy and the mobilized orecomponents became less and the deep-sourced fluidsbecame negligible, with only the shallow-sourced fluid-sys-tems acting weakly and restrictedly (Fig. 7C3). Therefore,this latest stage is characterized by low-temperature andshallow-sourced fluids and contributed little to Au mineral-

ization. This is the L-stage of the Shanggong Au deposit.This late extensional stage is also characterized by alkalinegranitoids typically associated with the final stages of extension in rift settings (G3 granites; Fig. 7C3).

The model is supported by our studies not only on theShanggong Au deposit, but also by studies on similardeposits in the Xiong’er Terrane (e.g. Tieluping Ag deposit;Chen et al., 2004).

6. Concluding remarks

The Qinling Orogen contains a diverse range of hydrothermal ore deposits at the eastern end of the Qin-ling Mountains. The Qinling Orogen was formed duringthe Yanshanian orogeny, and was accompanied by gra-nitic magmatism and hydrothermal activity, whichresulted in the formation of structurally-controlled oro-genic lodes of Au, Ag, porphyry Mo deposits, mineral-ized diatremes and breccia pipes, skarns andstratabound precious and base metal deposits (Huet al., 1988, 1997; Chen and Fu, 1992; Li et al., 1996;Wang et al., 1997; Fan et al., 1998; Chen, 1998; Chenet al., 2000a; Mao et al., 2002).

The orogenic Shanggong lode Au deposit is hosted inunmetamorphosed Proterozoic volcanic rocks and ischaracterized by mineral assemblages of early quartz– pyrite, middle-stage sulfides and late-stage quartz–car-bonate. Hydrogen–oxygen–carbon isotope systematicsindicates that the ore fluids evolved from deep-sourcedmagmatic and/or metamorphic systems to systems domi-nated by meteoric water. The main mineralising phase,which we recognise as M-stage in the Shanggong Audeposit, occurred during extensive mixing of these twofluid-systems. Nineteen d

18Ow values of the E-stage flu-ids, from 4.2‰ to 13.4‰ and with an average of 8.1‰, together with a positive d

13C value (1.5‰) for

ankerite, suggest that metamorphic devolatilization of

carbonate–bearing sedimentary rocks at depth was thesource of the hydrothermal fluids.

On the basis of isotope systematics of the Shanggongdeposit we argue that the CSC sequence of the Guan-daokou and Luanchuan Groups could have been a favor-able source for the mineralizing fluids. A similar origin is

envisaged for other orogenic lodes in the region (Fig. 2),such as the Tieluping Ag-dominated deposit (Chen et al.,2004).

Rb–Sr isochron data indicate ages of 242±11, 165 ± 7,and 113 ± 6 Ma for the early, middle and late mineralis-ing stages, respectively. These ages tie in reasonably wellwith the regional tectonic evolution, involving the Indo-sinian (Triassic) and Yanshanian (Jurassic and Creta-ceous) orogenies. These orogenic events progressedfrom early collisional compression (Triassic to EarlyJurassic), through a compression-to-extension transition(Late Jurassic to Early Cretaceous), to late extension(Cretaceous). During the Mesozoic collision events, a

north-dipping A-type subduction zone was active alongthe Machaoying fault. The slab south of the Machaoyingfault, mainly consisting of the Guandaokou and Luanch-uan Groups, was subducted beneath the Xiong’er Ter-rane and subsequently metamorphosed and dehydrated.This provided fluids to the overriding slab (i.e. Xiong’erTerrane) and was ultimately responsible for the develop-ment of the Kangshan–Shanggong hydrothermal Au–Agbelt, the Huashan granitoids and the Qiyugou–Leimen-gou porphyry-breccia belt. In our model, this three-stageevolution can be linked to the three stages of mineralis-ing fluid evolution. We argue that the collisional com-

pression-to-extension transition regime is an idealgeodynamic setting for large-scale hydrothermal metallo-genesis and granitic magmatism, and that these two areeffects of the same cause. The region between the Mach-aoying fault and Huashan granites is, perhaps, the bestarea for structurally-controlled orogenic Au, Ag, andbase metals deposits, whereas the zone north of theHuashan granite suite would be more favourable formagmatic-hydrothermal deposits, such as porphyry-,breccia- and epithermal style deposits.

Acknowledgments

The study is financially supported by the 973-program(Grant No. 2006CB403508) and the National Natural Sci-ence Foundation of China (Nos. 40425006, 40730421 and40352003), and. We thank Profs. S. F. Cox, D. J. Ellisand Fan Hongrui for their constructive advice on the re-search and manuscript preparation. Drs. K. Cassidy, S.Hagemann, T. Baker, N. Cook, and K. Zaw are thankedfor their comments of the earlier versions of this manu-script. Prof. Lian-Xing Gu and an anonymous referee arethanked for their constructive review of this paper. FrancoPirajno publishes with the permission of the Director of the

Geological Survey of Western Australia.




References

Bierlein, F.P., Maher, S., 2001. Orogenic disseminated Au in Phanerozoicfold belts—examples from Victoria, Australia and elsewhere. OreGeology Reviews 18, 113–148.

Chacko, T., Mayeda, T.K., Clayton, R.N., Goldsmith, J.R., 1991. Oxygenand carbon isotope fractionations between CO2 and calcite. Geochi-

mica et Cosmochimica Acta 55, 2867–2882.Chen, Y.J., 1998. Fluidization model for continental collision inspecial reference to study on ore forming fluid of Au deposits inthe eastern Qinling mountains, China. Progress in Natural Science8, 385–393.

Chen, Y.J., Fu, S.G., 1992. Gold Mineralization in West Henan, China.China Seismological Press, Beijing, p. 234, In Chinese, with EnglishAbstract.

Chen, Y.J., Li, C., Zhang, J., Li, Z., Wang, H.H., 2000a. Sr and O isotopiccharacteristics of porphyries in the Qinling molybdenum deposit beltand their implication to genetic mechanism and type. Science in China,Series D 43 (suppl), 82–94.

Chen, Y.J., Liu, C.Q., Chen, H.Y., Zhang, Z.J., Li, C., 2000b. Carbonisotope geochemistry of graphite deposits and ore-bearing khondaliteseries in North China. Implications for several problems. Acta

Petrologica Sinica 16, 233–244, in Chinese, with English Abstract.Chen, Y.J., Pirajno, F., Sui, Y.H., 2004. Isotope geochemistry of the

Tieluping Ag deposit, Henan Province, China. A case study of orogenic Ag mineralization and related tectonic model. MineraliumDeposita 39, 560–575.

Chen, Y.J., Pirajno, F., Sui, Y.H., 2005a. Geology and D–O–C isotopesystematics of the Tieluping silver deposit, Henan, China. Implicationsfor ore genesis. Acta Geologica Sinica 79, 106–119.

Chen, Y.J., Pirajno, F., Qi, J.P., 2005b. Origin of gold metallogeny andsources of ore-forming fluids, in the Jiaodong province eastern China.International Geology Reviews 47, 530–549.

Chen, Y.J., Pirajno, F., Qi, J.P., Li, J., Wang, H.H., 2006. Ore geology,fluid geochemistry and genesis of the Shanggong gold deposit, EasternQinling orogen, China. Resource Geology 56, 99–116.

Chen, Y.J., Pirajno, F., 2005. Linking the CMF model to metallogenic

zoningin the east Qinling Orogen, central China. In: Mao, J.W.,Bierlein, F.P. (Eds.), Mineral Deposit Research: Meeting the GlobalChallenge. Springer, Berlin SGA 2005, Beijing, pp. 905–908.

Chen, Y.J., Zhao, Y.C., 1997. Geochemical characteristics and evolutionof REE in the Early Precambrian sediments: evidences from thesouthern margin of the North China Craton. Episodes 20, 109–116.

Cox, S.F., Knackstedt, M.A., Braun, J., 2001. Principles of structuralcontrol on permeability and fluid flow in hydrothermal system.Reviews in Economic Geology 14, 1–24.

Cui, B., 1991. Lead isotope compositions of non-ferrous and preciousmetallic deposits at the southern margin of the North China Platform.Mineral Deposits Exploration 2, 30–41, in Chinese.

Fan, H.R., Xie, Y.H., Wang, Y.L., 1998. Fluid–rock interaction duringmineralization of the Shanggong structure-controlled alteration-typeAu deposit in western Henan province, Central China. Acta Petro-

logica Sinica 14, 529–541, In Chinese, with English abstract.Fan, H.R., Xie, Y.H., Zhao, R., Wang, Y.L., 1994. Stable isotope

geochemistry of rocks and gold deposits in the Xiong’ershan area,western He’nan province. Contributions to Geology and MineralResources Research 9, 54–64, In Chinese, with English abstract.

Faure, G., 1986. Principles of Isotope Geology, second ed. John Wiley andSons, New York, p. 589.

Goldfarb, R.J., Groves, D.I., Cardoll, S., 2001. Orogenic Au and geologictime: a global synthesis. Ore Geology Reviews 18, 1–75.

Groves, D.I., Goldfarb, R.J., Gebre-Mariam, M., Hagemann, S.G.,Robert, F., 1998. Orogenic Au deposits: a proposed classification inthe context of their crustal distribution and relationship to other Audeposit types. Ore Geology Reviews 13, 7–27.

Hagemann, S.G., Cassidy, K.F., 2000. Archean orogenic lode Audeposits. Reviews in Economic Geology 13, 9–68.

Han, Y.G., Zhang, S.H., Pirajno, F., Zhang, Y.H., 2007. Evolution of theMesozoic granites in the Xiong’ershan–Waifangshan region, westernHenan Province, China and its tectonic implications. Acta GeologicaSinica 81 (2), 253–265.

Henan Bureau of Geology and Mineral Resources (HBGMR), 1989.Regional Geology of Henan Province. Geological Publishing House,Beijing, p. 772 (in Chinese).

Henan Institute of Geology (HIG), 1985. Study on metallogenic condi-tions and types of Au deposits in Henan Province. UnpublishedResearch Report, Zhengzhou, p. 165 (in Chinese).

Hoefs, J., 2004. Stable Isotope Geochemistry, fifth ed. Springer-Verlag,Berlin, p. 201.

Howell, D.G., 1995. Principles of Terrane analysis – New Applications forGlobal Tectonics. Chapman and Hall, London, p. 245.

Hu, S.X., Lin, Q.L., Chen, Z.M., Li, S.M., 1988. Geology and Metallog-eny of the Collision Belt Between the North and the South ChinaPlates. Nanjing University Press, Nanjing, p. 558, in Chinese.

Hu, S.X., Zhao, Y.Y., Xu, J.F., Ye, Y., 1997. Geology of Au Deposits inNorth China Platform. Science in ChinaPress,Beijing,p. 220, in Chinese.

Jamieson, R.A., 1991. P–T–t paths of collisional orogenesis. GeologischeRundschau 180, 321–332.

Jia, C.Z., 1987. Geochemistry and tectonics of the Xionger Group in theeastern Qinling Mountains of China—a mid Proterozoic volcanic arcrelated to plate subduction. Geological Society of London SpecialPublication 33, 437–448.

Kerrich, R., Goldfarb, R.J., Groves, D.I., Garwin, S., Jia, Y.F., 2000. Thecharacteristics, origins and geodynamic settings of supergiant Aumetallogenic provinces. Science in China, Series D 43 (Suppl.), 1–68.

Kroner, A., Compston, W., Zhang, G.W., Guo, A.L., Todt, W., 1988. Ageand tectonic setting of late Archean greenstone-gneiss terrain in HenanProvince, China, as revealed by single-grain zircon dating. Geology 16,211–215.

Kusky, T.M., Li, J.H., 2003. Paleoproterozoic tectonic evolution of theNorth China Craton. Journal of Asian Earth Sciences 22, 383–397.

Li, Y.F., 2004. Study of the large-scale hydrothermal ore-forming goldsystem in Xiaoqinling-Xiong’ershan area. Unpublished Report StateKey Project No. 973 (in Chinese).

Li, C., Chen, Y.J., He, S.D., 2001. East Qinling–Dabieshan lithospheredelaminating age, mechanism and direction-petrological evidences andstipulation. Chinese Journal of Geochemistry 20, 59–72.

Li, J.L., Sun, S., Hao, J., Xiao, W.J., 1999. Time limit of collision event of collision orogeny. Acta Petrologica Sinica 15, 315–320, In Chinese,with English Abstract.

Li, S. M., Qu, L. Q., Li, X. M., Li, D. T., Xu, Z. X., 1996. Themineralizing conditions and regularities of altered-structural type Audeposits in the Xiong’er Mountain. In: Geology and Metallogeny of the Southern Margin of the North China Platform. Publishing Houseof China University of Geosciences, Wuhan, p. 161–189. (in Chinese).

Mao, J.W., Goldfarb, R.J., Zhang, Z.W., Xu, W.Y., Qiu, Y.M., Deng, J.,2002. Au deposits in the Xiaoqinling–Xiong’ershan region, QinlingMountains, central China. Mineralium Deposita 37, 306–325.

O’Brien, P.J., 2001. Subduction followed by collision: Alpine and

Himalayan examples. Physics of Earth and Planetary Interiors 127,277–291.Pirajno, F., Chen, Y.J., 2005. Hydrothermal ore systems associated with

the extensional collapse of collision orogens. In: Mao, J.W., Bierlein,F.P. (Eds.), Mineral Deposit Research: Meeting the Global Challenge.Springer, Berlin, SGA 2005, Beijing, pp. 1045–1048.

Qi, J.P., Zhang, J., Tang, G.J., 2005. Carbon and oxygen isotopecomposition of the Meso-Neoproterozoic strata south of the Xiong’erTerrane: evidences of the CMF model. Acta Petrologica Sinica 21,1365–1372, In Chinese with English abstract.

Qiu, Y.M., Groves, D.I., 1999. Late Archean collision and delaminationin the southwest Yilgarn craton: the driving force for Archeanorogenic lode Au mineralization?. Economic Geology 94 115–122.

Ratschbacher, L., Hacker, B.R., Calvert, A., Webb, L.E., Grimmer, J.C.,McWilliams, M.O., Ireland, T., Dong, S., Hu, J., 2003. Tectonics of




the Qinling (Central China): tectonostratigraphy, geochronology anddeformation history. Tectonophysics 366, 1–53.

Ren, F.G., Yin, Y.J., Li, S.B., Zhao, J.N., 2001. The coupling characterbetween isotopic geochronology of Indosinian Epoch in Xiong’er faultbasin. Bulletin of MineralogyPetrology and Geochemistry 20, 286–288.

Schidlowski, M., 1998. Beginning of terrestrial life: problems of the earlyrecord ad implications for extraterrestrial scenarios. Instruments,Methods and Missions for Astrobiology SPIE 3441, 149–157.

Sheppard, S.M.F., Schwarcz, H.P., 1970. Fractionation of carbon andoxygen isotopes and magnesium between coexisting metamorphiccalcite and dolomite. Contribution to Mineralogy and Petrology 26,161–198.

Streit, J.E., Cox, S.F., 2002. Evolution of fracture networks in shear zones:insights from see-through experiments on biphenyl aggregates. Journalof Structural Geology 24, 107–122.

Sui, Y.H., Wang, H.H., Gao, X.L., Chen, H.Y., 2000. Ore fluid of theTieluping Ag deposit of Henan Province and its illustration of thetectonic model for collisional petrogenesis, metallogenesis and fluid-ization. Science in China, Series D 43 (supp.), 108–121.

Sun, D.Z., Hu, W.X., Tang, M., Zhao, F.Q., Condie, K.C., 1990. Originof Late Archean and Early Proterozoic rocks and associated mineraldeposits from the Zhongtiao Mountains, east-central China. Precam-brian Research 47, 287–306.

Valley, J.W., 1986. Stable isotope geochemistry of metamorphic rocks. In:Valley J.W, Taylor, H.P., O’Neil, J.R. (Eds.), Stable Isotopes in HighTemperature Geological Processes. Review in Mineralogy 16, pp. 445–489.

Wang, H.H., Chen, Y.J., Gao,X.L.,2001a.The isotopegeochemistryof theKangshan Au deposit, Henan and its illustration of the CPMF model.Mineralium Deposita 20, 190–198, in Chinese, with English Abstract.

Wang, Y.T., Mao, J.W., Lu, X.X., 2001b. 40 Ar/39 Ar dating andgeochronological constraints on the ore-forming epoch of the Qiyugoudeposit in Songxian County, Henan Province. Geology Review 47,551–555, In Chinese, with English Abstract.

Wang, Z.G., Cui, B., Xu, M.L., 1997. Tectonic Evolution and Mineral-ization of the Southern Margin of the North China Block. Metallur-gical Industry Press, Beijing, p. 310, in Chinese.

Windley, B.F., 1995. The Evolving Continents, third ed. John Wiley &Sons, Chichester, p. 526.

Xu, Z.Q., Lu, Y.L., Tang, Y.Q., 1986. Deformation characteristics andtectonic evolution of the eastern Qinling orogenic belt. Acta GeologicaSinica 60, 237–247.

Xue, L.W., Yuan, Z.L., Zhang, Y., Qiang, L.Z., 1995. The Sm–Nd isotopeage of the Taihua Group in the Lushan area and their implications.Geochimica 24 (suppl.), 92–97, in Chinese.

Yin, L.M., Yuan, X.L., Meng, F.W., Hu, J., 2005. Protists of the upperMesoproterozoic Ruyang group in Shanxi Province, China. Precam-brian Research 141, 49–66.

Yuan, X.C., Ren, J., Xu, M.C., Tang, W.B., 2002. Reflection seismicprofile from Dengxian to Nanzhang, Eastern Qinling, and its tectonicimplication. Geology in China 29, 4–19, In Chinese, with EnglishAbstract.

Zartman, R.E., Doe, B.R., 1981. Plumbotectonics-the model. Tectono-physics 75, 35–162.

Zhang, B.R., Gao, S., Zhang, H.F., Han, Q.W., 2002. Geochemistry of Qinling Orogen. Science Press, Beijing, p. 187 In Chinese.

Zhang, G.W., Zhang, B.R., Yuan, X.C., Xiao, Q.H., 2001. QinlingOrogen and Continental Geodynamics. Science Press, Beijing, p. 855,In Chinese.

Zhang, L.G., 1989. Petrogenic and Minerogenic Theories and Prospecting.Beijing University Technology Press, Beijing, p. 200, In Chinese withEnglish abstract.

Zhang, Y.H., Zhang, S.H., Han, Y.G., Pirajno, F., 2005. Low-sulphida-tion epithermal gold–bearing Qiyugou breccia pipes, Xiong’ershanmountains, China. In: Mao, J.W., Bierlein, F.P. (Eds.), MineralDeposit Research: Meeting the Global Challenge. Springer, Berlin,SGA 2005, Beijing, pp. 1111–1114.

Zhang, Z.H., Zhang, J.X., Ye, S.Z., 1994. Isotope Dating on Au Depositsin East Shandong. China Seismological Press, Beijing, p. 56 InChinese..

Zhao, G.C., Sun, M., Wilde, S.A., Li, S.Z., 2004. A Paleo-Mesoprotero-zoic supercontinent: assembly, growth and breakup. Earth-ScienceReviews 67, 91–123.

Zhao, T.P., Zhou, M.F., Zhai, M., Xia, B., 2002. Paleoproterozoic rift-related volcanism of the Xiong’er Group, North China Craton:implications for the breakup of Columbia. International GeologyReviews 44, 336–351.

Zheng, Y.F., 1999. Stable isotope geochemistry. In: Zheng, Y.F. (Ed.),Chemical Geodynamics. Science Press, Beijing, pp. 62–118, inChinese.

Zhu, R.X., Yang, Z.Y., Wu, H.N., 1998. Paleomagetic constraints on thetectonic history of the major blocks of China during the Phanerozoic.Science in China, Series D 41 (suppl), 1–21.


11 isotope geochemistry and implications for ore genesis, china

Documents