Porphyry Copper Deposits In China Research Articles

Critical elements in porphyry copper deposits of China

As the world’s major source of Cu, Mo, and Au, porphyry copper deposits are magmatic-hydrothermal systems in which base and precious metals are deposited from aqueous solutions at temperatures generally >300°C. During formation of the deposits, metal-transporting fluids typically affected large volumes (up to ~100 km3) of upper crustal rocks, which has led to enormous mass redistribution and local concentration of many elements. Several critical elements, including Re, Se, and Te that are typically not found as primary ores, are locally concentrated in some porphyry copper deposits. Presently, mining and milling of porphyry copper deposits supply ~80% of the world’s Re and nearly all of the Se and Te. China has about 70 economic porphyry copper deposits, including 11 giant and 16 large deposits, with total pre-mining resources of ~78 million tonnes (Mt) Cu averaging 0.2% to 1% Cu, ~4.7 Mt Mo averaging 0.01% to 0.08% Mo, and 1400 tonnes (t) Au averaging 0.5 g/t Au. Rhenium, Se, Te, and PGE (platinum group elements) have been reported to be enriched in some porphyry copper deposits in China, but their tonnage, grade, occurrence, and resource potential remain unclear. In this study, based on a simple synthesis of critical elements in the porphyry copper deposits worldwide and geological characteristics of Chinese porphyry copper deposits, we systematically summarize these attributes of critical elements, particularly Re, in the porphyry copper deposits of China. The porphyry copper deposits in China are mainly concentrated in the following belts or districts: The Gangdese belt in southern Tibet, the Yulong belt in eastern Tibet, the Duolong district in central Tibet, the Zhongdian belt in northwestern Yunnan Province, the Central Asian orogenic belt across northern China, the Zhongtiaoshan belt in Shanxi Province, the Middle-Lower Yangtze River Valley belt, and the Dexing district in Jiangxi Province. Chinese porphyry copper deposits were formed during Paleoproterozoic, Ordovician, Carboniferous, Late Triassic to Early Cretaceous, and Eocene to Miocene, with the majority forming during the latter two time periods. Approximately 45% of the giant and ~30% of the large porphyry copper deposits in China formed in arc settings, whereas at least 35% of the giant and ~45% of the large porphyry copper deposits in China occured in post-collisional settings. The porphyry copper deposits in China typically contain ~3−313 t of Re at average grades ranging from 0.03 to 0.5 g/t Re, with ten deposits containing >50 t Re. The Re-rich porphyry copper deposits in China were mainly formed during Jurassic and Eocene to Miocene. The three largest deposits (Yulong, Jiama, and Qulong), in terms of contained Re, were formed during Eocene to Miocene and in a postcollisional setting. Rhenium in these porphyry copper deposits mainly occurs in molybdenite, and is associated with potassic and/or phyllic alteration. Average Re content in molybdenite from these deposits ranges from 30 to 1000 ppm, but shows a negative correlation with the Mo grade of the corresponding deposit. In contrast, there are only limited data on the endowment of Se, Te, and PGE for Chinese porphyry copper deposits. Similar to porphyry copper deposits worldwide, Se, Te, and PGE in Chinese porphyry copper deposits are concentrated in the sulfide minerals. The contents of Se and Te in sulfide minerals from several deposits (e.g., Bolong, Shaxi) range from ~3 to 700 ppm and are typically highest (generally >300 ppm) in Cu-bearing sulfides (e.g., bornite, chalcopyrite). Concentrations of PGE in ores of Chinese porphyry copper deposits are highly variable, with Pd+Pt contents ranging from 0.2 to 450 ppb. In summary, Chinese porphyry copper deposits, particularly those in postcollisional settings, show similar grades of Re, Se, Te, and PGE to porphyry copper deposits worldwide, indicating a large potential of these critical elements in Chinese porphyry copper deposits to meet the nation’s economic needs. To better understand the occurrence, resource potential, and enrichment processes of critical elements in the porphyry copper deposits of China, detailed case studies and regional comparisons, as well as improvements in analytical techniques, are a pressing need.

Geochronology and geochemistry of Eocene potassic felsic intrusions in the Nangqian basin, eastern Tibet: Tectonic and metallogenic implications

The Jinshajiang–Ailaoshan copper belt is the most significant porphyry copper belt in eastern Tibet. In the northern segment of this belt within the Nangqian basin, which occurs 100km east of the Yulong porphyry copper deposit, several felsic intrusions have been recently discovered. The Yulong porphyry copper deposit is one of the largest porphyry copper deposits in China, and it is associated with peraluminous adakitic rocks formed in a post-collisional setting. The Nangqian felsic intrusions vary from syenite porphyry to monzonite porphyry in rock types. No significant Cu–Au mineralization has been found in the Nangqian felsic intrusions despite extensive exploration in recent years. LA-ICP-MS zircon U–Pb dating reveals that the Nangqian syenite porphyry and monzonite porphyry were emplaced at ~35.6±0.3Ma and from 39.5±0.3 to 37.4±0.3Ma, respectively, similar to the age of the Yulong porphyry copper deposit. The Nangqian felsic intrusions are characterized by metaluminous compositions (A/CNK=0.82–1.01), and they share some common features with shoshonites such as high K2O contents (4.58–5.58wt.%), high K2O/Na2O ratios (0.92–1.28), LREE–LILE enrichments and negative Nb–Ta–Ti–P anomalies, as well as with adakites derived from an eclogite-facies source with high Al2O3 (14.98–15.74wt.%), Sr (954–2190ppm), Sr/Y (68–132) and La/Yb (53–85), and low Y and Yb contents. The Nangqian felsic intrusions have high initial 87Sr/86Sr (0.7050–0.7055), variable εNd(t) (−0.31–1.43) and small variations in (206Pb/204Pb)i (18.68–18.74), (207Pb/204Pb)i (15.53–15.62) and (208Pb/204Pb)i (38.51–38.80). Zircon crystals from both syenite and monzonite porphyries are characterized by positive εHf(t) from 5.2 to 8.5. The results suggest that the syenite and monzonite magmas were differentiated from parental shoshonitic melts by fractional crystallization of olivine, clinopyroxene and minor feldspar. The parent magmas originated from a lithospheric mantle metasomatized by slab-derived fluids or melts during continental subduction. The differences in both sources and depths of partial melting may explain the difference in the extent of Cu–Au mineralization between the Yulong and Nangqian porphyries.

Spatial pattern and dynamic control for mineralization in the Pulang porphyry copper deposit, Yunnan, SW China: Perspective from fractal analysis

The Pulang ore deposit, one of the largest porphyry copper deposits in China, is located in the Yidun continental arc, SW China. The alteration zones in the deposit transit upward and outward from early potassium-silicate, through quartz–sericite, to later propylitization. The wallrock near the porphyry stock was mostly changed into hornfels. The former two alterations host the main orebodies, constituting the core of mineralized zone; the later two alterations only develop weak mineralization surrounding the core. In this paper, various fractal indices, including the exponent of lacunarity, multifractal spectrum, correlation dimension and Hurst exponent, are applied to characterize the Cu spatial distribution in 114 drillcores in the Pulang ore deposit, with the aim to correlate the element spatial pattern with its dynamic drive. Compared to fractal indices in the propylitic zone and hornfels, the exponents of lacunarity in the potassium-silicate and quartz–sericite zones exhibit lower and more stable values, the correlation dimensions are higher and more consistent; yet the values of height difference of multifractal spectrum are lower and largely varied, and the Hurst exponents show little difference. Variations of the former three indices suggest that the core of mineralized zone has more homogeneity, stronger compactness of high concentrations, and greater proportion of high concentrations in the Cu distribution compared to the other parts of the deposit. More importantly, the correlation dimension, indicating the complexity of controls underpinning the system, is closely correlated to the exponent of lacunarity, which represents the homogeneity of spatial pattern. This correlation between those two indices implies a genetic link, that is to say the greater complexity of controls results in a more homogeneous spatial distribution of Cu in the porphyry deposit. The stability of the two indices is considered to reflect the development of thick orebody, providing a new perspective to understand the genesis of porphyry ore deposit. This interpretation from the fractal perspective is consistent with the geological understanding for the formation of porphyry deposits, which is considered to be subject to the complexity of ore fluid evolution with multifaceted physicochemical conditions. For a pragmatic use, these two fractal indices are successfully applied in the delineation of the core of mineralized zone in the plane view.

Reviews of Structural Settings of Porphyry Copper Deposits in China

Reviews of Structural Settings of Porphyry Copper Deposits in China

SHRIMP U-Pb DATING ON HYDROTHERMAL ZIRCONS: EVIDENCE FOR AN EARLY CRETACEOUS EPITHERMAL EVENT IN THE MIDDLE JURASSIC DEXING PORPHYRY COPPER DEPOSIT, SOUTHEAST CHINA

The Dexing porphyry copper deposit, part of the circum-Pacific porphyry copper ore belt, is the largest porphyry copper deposit in China (1,500 million tonnes [Mt] of ore at 0.43% Cu, 0.02% Mo, and 0.16 grams per tonne Au, approximately equivalent to 6.45 Mt Cu, 0.25 Mt Mo, and 24 tonnes Au). We report results of sensitive high resolution ion microprobe (SHRIMP) U-Pb dating on zircons separated from a thick (~20-cm-wide) pyrite-chalcopyrite-quartz vein in this deposit, which is mineralogically and texturally different from the porphyry-related ore-bearing thin quartz veins. The zircons from the thick quartz vein are unzoned and nonluminescent (black) in the cathodoluminescence images. They show relatively flat light rare-earth element patterns and have high La content and low (Sm/La)N and Ce/Ce* values. These features are typical of hydrothermal zircons. SHRIMP U-Pb dating on these hydrothermal zircons yielded weighted mean 206Pb/238U ages of 106.5 ± 0.9 and 100.9 ± 3.5 Ma, which are ca. 70 m.y. younger than the ages (172–171 Ma) of the ore-bearing porphyries and the molybdenite Re-Os ages (170.9 ± 1.1 Ma) of the porphyry-related disseminated and veinlet (usually <1 cm in width) ores. This suggests the occurrence of a younger, distinct Cu (Au?) hydrothermal event superimposed on the porphyry Cu-Mo-Au mineralization at Dexing. The mineralogical features and age of this hydrothermal event suggest that it could belong to the metallogenic event responsible for the formation of the late Early Cretaceous to early Late Cretaceous (110–95 Ma) epithermal Cu-Au-Ag deposits in southeast China.

Mantle origin of the Dexing porphyry copper deposit, SE China

The Dexing ore deposit, Jiangxi Province, is the largest porphyry copper deposit in China. Controversies exist regarding the ore-forming source of this deposit. We have conducted Pb isotope analyses of pyrites from the Tongchang and Fujiawu mines. Our results document consistent Pb isotopes from these two orebodies, with 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb ratios of 17.954–18.320, 15.407–15.517, and 37.888–38.153, respectively. These Pb isotope ratios are consistent with those of ore-bearing adakitic porphyries but distinctly different from those of the Neoproterozoic metamorphic wall rocks, which indicates that the metals were derived from the porphyries. Based on previous S and Os isotopic data and comparisons with more than 20 Mo-bearing deposits worldwide, we further attribute the narrow range of δ34S values of sulphide minerals and high Re–187Os concentrations of associated molybdenites to a mantle origin. This large-scale copper deposit was evidently emplaced in a continental arc setting attending westward subduction of the palaeo-Pacific plate. Partial melting of the downgoing oceanic slab generated the adakitic magmas. The associated metals were extracted from the lithospheric mantle by these magmas during ascent through the mantle wedge.

Origin of the Dexing Cu-bearing porphyries, SE China: elemental and Sr–Nd–Pb–Hf isotopic constraints

The Dexing porphyry copper deposit, part of the circum-Pacific porphyry copper ore belt, is the largest porphyry copper deposit in China. We present new LA–ICP–MS zircon U–Pb and molybdenite Re–Os dating, bulk-rock elemental and Sr–Nd–Pb isotopic as well as in situ zircon Hf isotopic geochemistry for these ore-bearing porphyries, in an attempt to better constrain their petrogenesis. LA–ICP–MS zircon U–Pb dating shows that the Dexing porphyries were emplaced in the early Middle Jurassic (∼171 Ma); molybdenite Re–Os dating indicates that the associated Cu–Mo mineralization was contemporaneous (∼171 Ma) with the igneous intrusion. The rocks are mainly high-K calc-alkaline and show adakitic affinities, including high Sr and low Y and Yb contents, high Sr/Y and La/Yb ratios, and high Mg# (higher than pure crustal melts). These porphyries have initial 87Sr/86Sr ratios of 0.7044−0.7047, ϵNd(T) values of –1.5 to +0.6, and ϵHf(T) (in situ zircon) values of +2.6 to +4.6. They show unusually radiogenic Pb isotopic compositions with initial 206Pb/204Pb ratios up to 18.41 and 207Pb/204Pb up to 15.61. These isotopic compositions are distinctly different from either Pacific MORB or Yangtze lower crust but are similar to the subducting sediments in the western Pacific trenches. Detailed elemental and isotopic data suggest that the Dexing porphyries were emplaced in a continental arc setting coupled with westward subduction of the palaeo-Pacific plate. Partial melting involved the subducted slab (mainly the overlying sediments), with generated melts interacting with the lithospheric mantle wedge, thereby forming the investigated high-K calc-alkaline porphyry magmas.

Formation of the adakite-like granitoid complex and porphyry copper-gold deposit in Shaxi from southern Tancheng-Lujiang fault belt: A clue to the West Pacific plate subduction

On the basis of the geological and geochemical studies, including chemical analysis of bulk rocks, rare-earth and trace element studies, fluid inclusion, and S and O isotopic analyses, the authors described the geological background of the deposit in detail and presented significant proofs for the conditions of formation of the Shaxi porphyry copper-gold deposit. Compared with other large and supper-large porphyry copper deposits in China and the adjacent Cu-Au mineralized areas, the ore-forming processes and conditions were analyzed; and the possibility of forming large porphyry copper deposits in the Shaxi area was discussed. The present study indicated that the ore-forming fluid and material were mainly of magmatic origin, while meteoric water played a certain role in the ore-forming processes. Interactions between subducting and overriding plates provided a major driving force for the formation of igneous rocks and the deposition of metal elements in East China since Jurassic. Based on the geochemical data of the Shaxi intrusive, it is found that the copper (gold) mineralization is closely related to the genesis of adakite-like intrusive in the Shaxi area. This adakite-like intrusive was formed in the subduction environment as a result of the subduction of the West Pacific plate toward the East China continent, where there is a great potentiality to form a large porphyry copper deposit.

Discrimination of Ore-Bearing and Barren Porphyries in the Yulong Porphyry Copper Ore Belt, Eastern Tibet

The Yulong porphyry copper ore belt is the largest belt of porphyry copper deposits in China. Detailed geological and geochemical comparison indicates that ore-bearing and barren porphyries in this belt were derived by progressive partial melting of veins of phlogopite-garnet clinopyroxenite in lherzolitic lithosphere. Ore-bearing porphyry represents the earliest melt derived by partial melting of accessory phases such as apatite, carbonate, and phlogopite, and thus contains high contents of volatiles F, Cl, and H2O. These volatiles promoted copper extraction and enrichment. Barren porphyry is the product of relatively high degrees of partial melting involving clinopyroxene and garnet, and thus is depleted in volatiles, hence barren of copper. This is the essential petrogenetic discrimination between ore-bearing and barren porphyries. Geochemical discrimination includes the following: Cu > 100 ppm, W > 5 ppm, F + Cl > 900 ppm, K2O/Na2O > 1.2, and Sm/Yb > 6.5 for bulk rock of the ore-bearing porphyries, and Mg/(Mg + FeT) > 0.57 and Fe3+/Fe2+ > 0.7 for biotite in the ore-bearing porphyries. In contrast, such values are all less for barren porphyries. These geochemical parameters have important significance for copper exploration in the Yulong porphyry copper belt.

Hydrothermal Alteration and Mineralization of Middle Jurassic Dexing Porphyry Cu‐Mo Deposit, Southeast China

AbstractThe Dexing deposit is located in a NE‐trending magmatic belt along the southeastern margin of the Yangtze Craton. It is the largest porphyry copper deposit in China, consisting of three porphyry copper orebodies of Zhushahong, Tongchang and Fujiawu from northwest to southeast. It contains 1168 Mt of ores with 0.5% Cu and 0.01% Mo. The Dexing deposit is hosted by Middle Jurassic granodiorite porphyries and pelitic schist of Proterozoic age. The Tongchang granodiorite porphyry has a medium K cal‐alkaline series, with medium K2O content (1.94–2.07 wt%), and low K2O/(Na2O + K2O) (0.33–0.84) ratios. They have high large‐ion lithophile elements, high light rare‐earth elements, and low high‐field‐strength elements. The hydrothermal alteration at Tongchang is divided into four alteration mineral assemblages and related vein systems. They are early K‐feldspar alteration and A vein; transitional (chlorite + illite) alteration and B vein; late phyllic (quartz + muscovite) alteration and D vein; and latest carbonate, sulfate and oxide alteration and hematite veins. Primary fluid inclusions in quartz from phyllic alteration assemblage include liquid‐rich (type 1), vapor‐rich (type 2) and halite‐bearing ones (type 3). These provide trapping pressures of 20–400 ´ 105 Pa of fluids responsible for the formation of D veins. Igneous biotite from least altered granochiorite porphyry and hydrothermal muscovite in mineralized granodiorite porphyry possess δ18O and δD values of 4.6‰ and −87‰ for biotite and 7.1–8.9‰, −71 to −73‰ for muscovite. Stable isotopic composition of the hydrothermal water suggests a magmatic origin. The carbon and oxygen isotope for hydrothermal calcite are −4.8 to −6.2‰ and 6.8–18.8‰, respectively. The δ34S of pyrite in quartz vein ranges from −0.1 to 3‰, whereas δ34S for chalcopyrite in calcite veins ranges from 4 to 5‰. These are similar to the results of previous studies, and suggest a magmatic origin for sulfur. Results from alteration assemblages and vein system observation, as well as geochemical, fluid inclusion, stable isotope studies indicate that the involvement of hydrothermal fluids exsolved from a crystallizing melt are responsible for the formation of Tongchang porphyry Cu‐Mo orebodies in Dexing porphyry deposit.

Quantitative Assessment of the Resource Potential of Porphyry Copper Systems in China

Using the method and principle of the “three-part” mode of mineral resource assessment, we have studied the geological setting, and temporal spatial distribution rule and models of the porphyry copper deposits in China. In our assessment we have also included 46 prospective areas. Based on the metal reserves database in 1999 and data from currently producing deposits, we have constructed a database of 984 deposits. We have studied grade-tonnage models according to the different types of mineralization, constructed a digital ore finding model, and developed quantitative assessment procedures for mineral resources. The probable resources for each prospective area have been calculated. This provides a reference database for evaluating the resource potential of porphyry copper systems in China.

Nature, diversity of deposit types and metallogenic relations of South China

The South China Region is rich in mineral resources and has a wide diversity of deposit types. The region has undergone multiple tectonic and magmatic events and related metallogenic processes throughout the earth history. These tectonic and metallogenic processes were responsible for the formation of the diverse styles of base and precious metal deposits in South China making it one of the resource-rich regions in the world. During the Proterozoic, the South China Craton was characterised by rifting of continental margin before eruption of submarine volcanics and development of platform carbonate rocks, and the formation of VHMS, stratabound copper and MVT deposits. The Phanerozoic metallogeny of South China was related to opening and closing of the Tethyan Ocean involving multiple orogenies by subduction, back-arc rifting, arc–continent collision and post-collisional extension during the Indosinian (Triassic), Yanshanian (Jurassic to Cretaceous) and Himalayan (Tertiary) Orogenies. The Late Palaeozoic was a productive metallogenic period for South China resulting from break-up and rifting of Gondwana. Significant stratabound base and precious metal deposits were formed during the Devonian and Carboniferous (e.g., Fankou and Dabaoshan deposits). These Late Palaeozoic SEDEX-style deposits have been often overprinted by skarn systems associated with Yanshanian magmatism (e.g., Chengmenshan, Dongguashan and Qixiashan). A number of Late Palaeozoic to Early Mesozoic VHMS deposits also developed in the Sanjiang fold belt in the western part of South China (e.g., Laochang and Gacun). South China has significant sedimentary rock-hosted Carlin-like deposits, which occur in the Devonian- to Triassic-aged accretionary wedge or rift basins at the margin of the South China Craton. They are present in a region at the junction of Yunnan, Guizhou, and Guangxi Provinces called the ‘Southern Golden Triangle’, and are also present in NW Sichuan, Gansu and Shaanxi, in an area known as the ‘Northern Golden Triangle’ of China. These deposits are mostly epigenetic hydrothermal micron-disseminated gold deposits with associated As, Hg, Sb + Tl mineralisation similar to Carlin-type deposits in USA. The important deposits in the Southern Golden Triangle are Jinfeng (Lannigou), Zimudang, Getang, Yata and Banqi in Guizhou Province, and the Jinya and Gaolong deposits in Guangxi District. The most important deposits in the Northern Golden Triangle are the Dongbeizhai and Qiaoqiaoshang deposits. Many porphyry-related polymetallic copper–lead–zinc and gold skarn deposits occur in South China. These deposits are related to Indosinian (Triassic) and Yanshanian (Jurassic to Cretaceous) magmatism associated with collision of the South China and North China Cratons and westward subduction of the Palaeo-Pacific Plate. Most of these deposits are distributed along the Lower to Middle Yangtze River metallogenic belt. The most significant deposits are Tonglushan, Jilongshan, Fengshandong, Shitouzui and Jiguanzui. Au–(Ag–Mo)-rich porphyry-related Cu–Fe skarn deposits are also present (Chengmenshan and Wushan in Jiangxi Province and Xinqiao, Mashan-Tianmashan, Shizishan and Huangshilaoshan in Anhui Province). The South China fold belt extending from Fujian to Zhejiang Provinces is characterised by well-developed Yanshanian intrusive to subvolcanic rocks associated with porphyry to epithermal type mineralisation and mesothermal vein deposits. The largest porphyry copper deposit in China, Dexing, occurs in Jiangxi Province and is hosted by Yanshanian granodiorite. The high-sulphidation epithermal system occurs at the Zijinshan district in Fujian Province and epithermal to mesothermal vein-type deposits are also found in the Zhejiang Province (e.g., Zhilingtou). Part of Shandong Province is located at the northern margin of the South China Craton and the province has unique world class granite-hosted orogenic gold deposits. Occurrences of Pt–Pd–Ni–Cu–Co are found in Permian-aged Emeishan continental flood basalt (ECFB) in South China (Jinbaoshan and Baimazhai in Yunnan Province and Yangliuping in Sichuan Province). South China also has major vein-type tungsten–tin–bismuth–beryllium–sulphide and REE deposits associated with Yanshanian magmatism (e.g., Shizhuyuan and Xihuashan), important world class stratabound base metal–tin deposits (Dachang deposit), and the large antimony deposits (Xikuangshan and Woxi). During the Himalayan Orogeny, many giant deposits were formed in South China including the recently emerging Yulong and Gangdese porphyry copper belts in Tibet and the Ailaoshan orogenic gold deposits in Yunnan.

Geological Setting of the Porphyry Copper Deposit Series of China

Abstract In accordance with the terms global minerogenic series, regional metallogenic series and ore deposit system which are put forward here, metallogenic environments at different levels are discussed for the porphyry copper deposit series in China. It is considered that the porphyry copper deposits in China are controlled not only by the boundaries of convergent plates but, more importantly, by the boundaries of intraplate divergent mobile belts and those between continental blocks. Besides, the emplacement of hypabyssal and supper‐hypabyssal calc‐alkaline magmas and the temporal‐spatial distribution of China's porphyry copper deposits are governed by the superimposition of fracture systems of the pre‐Alpine basements, Meso‐Cenozoic cover and continental‐margin new‐born crust. Such a superimposition has also resulted in the polycyclicity of the mineralization.