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Golden Triangle |
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Guizhou, China |
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Au
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Super Porphyry Cu and Au
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IOCG Deposits - 70 papers
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All papers now Open Access.
Available as Full Text for direct download or on request. |
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The Golden Triangle gold province occupies an area of more than 100 000 km2 in south-west Guizhou, south-east Yunnan and north-west Guangxi Provinces in southern China. Large parts of this region are characterised by extensive zones of significant mercury, arsenic, gold and thallium anomalism which encompass numerous gold deposits, some of which have reported resources in excess of 30 tonnes of gold.
The Golden Triangle is located overlying the south-western margin of South China Block, within the Phanerozoic Youjiang (or Nanpanjiang) Basin in China, also known as the Song Hiem basin in northern Vietnam, which are characterised by a predominantly Devonian to Middle Triassic marine succession. The South China Block is the product of the amalgamation of the Yangtze Craton (to the NW) and Cathaysia terrane, separated by a NE-SW trending fold belt/tectonic zone and the Jiangshan-Shaoxing suture. The two terranes were accreted following protracted NW-directed subduction between the Mesoproterozoic and Early Palaeozoic.
The Yangtze Craton is composed of a thick basement sequence of Archaean hornblende-plagioclase gneiss, biotite-plagioclase gneiss, amphibolite, granulites, marbles and banded iron formation; and Palaeoproterozoic quartzite, mica schist, slates and metavolcanic rocks and biotite-plagioclase gneiss, amphibolite, quartz schist, marble, overlain by the vast Yangtze Platform succession of shallow-water carbonate rocks that spanned the Neoproterozoic to Middle Triassic, followed by a thick succession of mostly siliciclastic rocks which spread across the platform in the Late Triassic (Pirajno, 2013; Rui and Mei, 2012; Enos et al., 2006).
The Cathaysia Terrane, to the SE of the Jiangshan-Shaoxing suture, is composed of sparsely exposed Palaeo- and Mesoproterozoic continental crust basement rocks, represented by 1.9 to 1.8 Ga sedimentary rocks and 1.8 to 1.4 Ga granites and volcanic rocks (Yu et al., 2005). During the Neoproterozoic the Cathaysia Block underwent a rifting stage between 857 and 837 Ma, corresponding to initiation of the break-up of the Rodinia supercontinent. Due to Early Palaeozoic (Caledonian) orogenic activity, Late Ordovician to Middle Devonian strata are absent over the Cathaysia Terrane, although crustal material of Palaeo- to Neoproterozoic age, with some Archaean components, are all extensively reworked at various stages during Caledonian (450 Ma), Indosinian (240 Ma) and early Yanshanian (160 Ma) thermal events, resulting in widespread granitic intrusions (Yu et al., 2005). The Indosinian (Triassic) magmatism produced voluminous granitic plutons in south China (Chen and Jahn 1998), with a wide range of ages, from ~260 to 200 Ma (Wang et al., 2005, 2007; Zhou et al., 2006; Chen et al., 2011). The Indosinian magmatism is interpreted to be in part due to NW-directed flat subduction of the Pacific plate beneath south China, leading to NW migration of shortening and broadly zonal distribution of plutons (Cui and Li 1983; Li and Li 2007). The Indosinian deformation and magmatism were equally influenced by the collision between the Indochina Craton from the SW with the South China Block in response to the closure of the Palaeotethys Ocean along the Jinshajiang-Ailaoshan-Song Ma suture zone on the SW margin of the South China Block (Wang et al., 2005, 2007; Zhou et al., 2006; Lepvrier et al., 2008; Chen et al., 2011; Rui and Mei, 2012) and collision of the Qiangtang-Sibumasu terranes to the west. The giant Yanshanian igneous province subsequently swept across South China, forming a swath >1000 km wide across the whole Cathaysian Block and the eastern part of the Yangtze Craton (Li and Li 2007). The granitic rocks in this province range in age from Jurassic to Cretaceous, notably the ∼180 to 170 Ma Early, ∼150 to 139 Ma Mid and ∼125 to <98 Ma Late Yanshanian events, interpreted to be related to further westward subduction of the Pacific oceanic lithosphere beneath the South China Block. During the same time, compression was also affected by the NE directed subduction of the Meso-Tethys Ocean beneath Sibumasu Block to the SW.
The Youjiang (or Nanpanjiang) Basin covers a diamond shaped area that is ~500 km across overlying the southwestern margin of the South China Block and passes laterally to the north and east into the more extensive cover sequences of the Yangtze Platform. It is bounded on all sides by major NW-SE and NE-SW regional fault zones (Xie et al., 2018). These structures include the Ziyun-Luodian Fault to the NE, the Shizong-Mile Fault to the NW and the Pingxiang-Nanning Fault to the SE. It extends to the northeastern Vietnam nappes to the southwest (Cai and Zhang, 2009; Lepvrier et al., 2011; Yang et al., 2012; Faure et al., 2014). The latter includes north, NE and east vergent folds and thrusts which resulted from the Indosinian Triassic collision between the South China and Indochina blocks which are separated by the Ailaoshan-Song Ma ophiolitic suture. These structures are overprinted by up to 800 km of Cenozoic sinistral offset along the broadly coincident NW-SE trending Ailaoshan-Red River Fault. In varying interpretations, the Jiangshan-Shaoxing suture, which separates the Yangtze Craton and Cathaysia Terrane: i). passes along the northern rim of the basin, which therefore overlies the latter terrane, or ii). follows the basins eastern margin, in which case the Yangtze Craton is basement, or iii). the basin straddles the suture and both basement blocks.
Deposition of the Youjiang-Nanpanjiang Basin succession was initiated by Late Cambrian (Early Caledonian) extension of the Yangtze Craton, with the oldest strata being Cambrian to Ordovician shales and calcareous rocks which outcrop in the cores of 50 km scale anticlines and domes formed by superimposed folds. These are followed by Early to Middle Devonian sandstone, siltstone and shale, intercalated with rift affinity basalt and dolerite (Bureau of Geology and Mineral Resources of Guangxi Zhuang Autonomous Region - BGMRGX, 1985; Yang et al., 2012) representing the main phase of deposition within the Youjiang Basin. This sequence commenced with Hercynian extension and rifting which commenced along the passive southwestern margin of the South China Block from the Early Devonian. Extension was coincident with the opening of the Ailaoshan‐Honghe ocean basin to the SW of what is now the major Ailaoshan‐Red River fault zone just south of the Vietnam-China border. This extension broke up the Yangtze Platform in the south by giving rise to a series of NW trending high-angle normal faults to form a complex pattern of platforms and interplatform rift basins (Chen et al., 2001) that influenced Youjiang Basin deposition, controlling its patterns of sedimentation and deformation (BGMRGX, 1985; Hu et al., 2002; Chen et al., 2011). Subsequently, from the Late Devonian to Triassic, a thermal sag phase sequence developed on the continental margin. A sequence of shallow-water platform-facies sedimentary rocks were deposited in the northwestern part of the Youjiang Basin, mainly composed of carbonate rocks interbedded with terrigenous detrital rocks which formed the 'grey unit' (Wang, 1990; Han et al., 1999). In contrast, in the southern and eastern sections of the basin, deeper-water slope to basin-facies rocks, dominated by calcareous mudstone, siltstone and siliceous rocks were deposited, intercalated with thinly layered carbonate rock and sandstone which together comprise the 'pink unit' (Wang, 1990; Han et al., 1999). The thermal sag/passive margin deposition was interrupted by the Indosinian and Yanshanian events mentioned above. In an emergent section of the eastern Youjiang Basin, Late Permian to Early Triassic marine sediments are uncomfortably overlain by Late Triassic to Jurassic red clastic rocks (BGMRGX, 1985; Yang et al., 2012).
The major Emeishan Flood Basalt and lesser (≤5%) silicic volcanic and plutonic rocks form a Large Igneous Province that was erupted between 262 Ma and 261 Ma in the Mid Permian, covering an area of >250 000 km2 and thickness of up to 5 km, but averaging 700 m. It overlies Yangtze Craton basement on the immediate northwestern margin of the Youjiang Basin. Facies thicknesses and distribution indicate this event was preceded by updoming and erosion prior to the basalt outpouring, influencing the location of the northwestern margin of the basin during the early Permian (Shellnutt, 2014).
Igneous rocks, including granites, quartz porphyry dykes and alkaline ultramafic dykes intrude the sedimentary rocks of the Youjiang Basin. In the west, east, and SE parts of the basin, ~80 to 95.6 Ma Late Yanshanian granites are exposed (Cai et al., 2006; Liu et al., 2007; Li et al., 2008; Cheng and Mao, 2010; Cheng et al., 2010; Mao et al., 2013; Xu et al., 2015), interpreted to be predominantly derived from crustal melts. Minor 95 to 97 Ma quartz porphyry (Chen et al., 2014; Zhu et al., 2017) and 85 to 88 Ma alkaline ultramafic dykes (Liu et al., 2010) related to the onset of renewed basin extension intruded the sedimentary rocks.
The sedimentary lithologies and facies distribution and depositional breaks, and the location and type of igneous rocks, along with geochemical characteristics of the sequences, all led Qiu et al. (2017) to conclude the tectonic setting of the Youjiang Basin represented a transition from an Early Triassic passive continental margin, to a Middle Triassic synorogenic foreland of the Indosinian orogeny during closure of the Palaeotethys Ocean and collision between the Indochina and South China blocks (BGMRYN, 1990; Lehrmann et al., 2007; Yang et al., 2012).
The majority of the gold is hosted by Triassic sedimentary rocks, with the larger accumulations being localised at the transition from thin bedded carbonate facies (tidal flat and reef) to the deeper water basinal siliciclastic suites. This concentration may be due to both chemical and porosity changes at the transition, and/or to buried rift margin structures influencing the position of the facies change and fluid ingress.
Most intrusions within the basin are ~10 to 30 km from the sediment-hosted Au deposits of the Golden Triangle. Only at the Liaotun Au deposit in the southeastern part of the Youjiang Basin is there an unaltered 95.5±0.7 Ma quartz porphyry dyke crosscutting gold mineralisation (40Ar/39Ar plateau age of magmatic muscovite phenocryst; Chen et al., 2014). This age provides a minimum for Au mineralisation, assuming all are coeval. Wang (1997) reported a small Jurassic sedimentary rock exposure near the Shuiyindong and Jinfeng deposits, which is conformable and folded with Late Triassic sedimentary rocks. As some of the orebodies in the Shuiyindong and Jinfeng deposits crosscut these folds, Au mineralisation should be synchronous with or younger than the folding, which suggests a maximum Jurassic age for Au mineralisation. Collectively, these relationships indicate that the Au mineralisation of the Golden Triangle sediment-hosted Au deposits was emplaced between the Jurassic and Late Cretaceous (Xie et al., 2018).
While Permian extension is indicated by alkalic Emeishian Flood Basalt and discordance at the Permo-Triassic boundary, the major deformation phases influencing the Youjiang-Nanpanjiang Basin were the Triassic Indosinian and Cretaceous Yanshanian orogenies (230 to 67 Ma) producing tight, small scale folding, numerous domal structures, NE directed overthrusting of Phanerozoic sedimentary rocks over the basement, and brittle WNW and north-south faults which host gold deposits.
Hydrothermal activity and gold deposition is interpreted to have been related to thermal activity during the Yanshanian, related to magmatic fluids and basin dewatering induced by compression and uplift, although no significant igneous activity is reported apart from minor dyking. Xie et al. (2018) undertook a study of pre-ore pyrite and ore-related sulphide minerals from the Shuiyindong and Jinfeng Au deposits, the largest strata-bound and fault-controlled deposits respectively in Guizhou, as well as collating data from other examples in the basin. A broad range of S isotope compositions were revealed from the pre-ore sedimentary pyrite which implies the S in these was most likely generated by diagenetic bacterial reduction from marine sulphate. In contrast, they found there was a narrow range of δ34S values of between ~-5 and +5‰ for ore-related sulphide minerals in all sediment hosted Au deposits in Guizhou, with the notable exception of the Jinfeng deposit. This was taken to suggests that the deposits may have formed in response to a single widespread metallogenic event. At Jinfeng, ore-related sulphide minerals have δ34S values ranging from 1.9 to 18.1‰, with most data plotting between 6 and 12‰. This may be explained by ore fluids mixing with local fluids with heavier δ34S, possibly basin brines with δ34S typically of >18‰ (Xie et al., 2018).
Few igneous rocks are exposed in the area surrounding these deposits, although there is evidence of magmatic activity within ~10 to 30 km, whilst gravity and magnetic data suggest a pluton ~5 km below the Shuiyindong deposit. Based on the in situ S isotope Xie et al. (2018) interpret a deep magmatic sulphur source for the ore fluids that formed the Guizhou sediment-hosted Au deposits.
Much of the gold is refractory, associated with fine arsenian pyrite and arsenopyrite with accompanying high As and Hg (as an assemblage of pyrite, arsenopyrite, cinnabar, native Hg, realgar and orpiment) and enriched antimony and carbon. Mineralisation is in general restricted to the confines of steep transgressive faults forming lenticular to anastomosing bodies cutting calcareous siliciclastic rocks below carbonates within domal structures, although stratabound ore is also recorded in calcareous arenites intersected by such faults.
The deposits in the Golden Triangle resemble those of the Carlin and related trends in Nevada, USA, although they differ in the absence of associated igneous activity and that the carbonate facies are above rather than below the basinal siliciclastics.
Key deposits include: Jinfeng/Lannigou, Yata, Getang, Zimudang, Shuiyindong, Nibao, Badu, which are the subject of separate records, and others such as Zhesang, Jinya, Liaotun, Banqi and Taipingdong.
The most recent source geological information used to prepare this decription was dated: 2018.
Record last updated: 24/3/2019
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd. Unauthorised copying, reproduction, storage or dissemination prohibited.
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Ashley R P, Cunningham C G, Bostick N H, Dean W E and Chou I M, 1991 - Geology and geochemistry of three sedimentary-rock-hosted disseminated gold deposits in Guizhou Province, Peoples Republic of China : in Ore Geology Reviews v6 pp 133-151
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Faure, M., Chen, Y., Feng, Z., Shu, L. and Xu, Z., 2017 - Tectonics and geodynamics of South China: An introductory note: in J. of Asian Earth Sciences v.141, pp. 1-6.
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Hu Rui-Zhong, Su Wen-Chao, Bi Xian-Wu, Tu Guang-Zhi and Hofstra A H 2002 - Geology and geochemistry of Carlin-type gold deposits in China: in Mineralium Deposita v37 pp 378-392
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Hu, X., Gong, Y., Zeng, G., Zhang, Z., Wang, J. and Yao, S., 2018 - Multistage pyrite in the Getang sediment-hosted disseminated gold deposit, southwestern Guizhou Province, China: Insights from textures and in situ chemical and sulfur isotopic analyses: in Ore Geology Reviews v.99, pp. 1-16.
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Jin, X.-Y., Hofstra, A.H., Hunt, A.G., Liu, J.-Z., Yang, W. and Li, J.-W., 2020 - Noble gases fingerprint the source and evolution of ore-forming fluids of Carlin-type gold deposits in the Golden Triangle, South China: in Econ. Geol. v.115, pp. 455-469.
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Pi, Q., Hu, R., Xiong, B., Li, Q. and Zhong, R., 2017 - In situ SIMS U-Pb dating of hydrothermal rutile: reliable age for the Zhesang Carlin-type gold deposit in the golden triangle region, SW China: in Mineralium Deposita v.52, pp. 1179-1190
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Qiu, L., Yan, D.-P., Yang, W.-X., Wang, J., Tang, X. and Ariser, S., 2017 - Early to Middle Triassic sedimentary records in the Youjiang Basin, South China: Implications for Indosinian orogenesis: in J. of Asian Earth Sciences v.141, pp. 125-139.
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Su Wenchao, Heinrich CA, Pettke T, Zhang Xingchun, Hu Ruizhong and Xia Bin, 2009 - Sediment-Hosted Gold Deposits in Guizhou, China: Products of Wall-Rock Sulfidation by Deep Crustal Fluids : in Econ. Geol. v104 pp 73-93
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Wilde A R 2003 - The Golden Triangle of southeast China: Another Carlin Trend ?: in SEG Newsletter, Soc. Econ. Geol., Denver No. 55, Oct 2003 pp 1, 9-12
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Xie, Z., Xia, Y., Cline, J.S., Pribil, M.J., Koenig, A., Tan, Q., Wei, D., Wang, Z. and Yan, J., 2018 - Magmatic Origin for Sediment-Hosted Au Deposits, Guizhou Province, China: In Situ Chemistry and Sulfur Isotope Composition of Pyrites, Shuiyindong and Jinfeng Deposits: in Econ. Geol. v.113, pp. 1627-1652.
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Zhao, J., Liang, J., Long, X., Li, J., Xiang, Q., Zhang, J. and Hao, J., 2018 - Genesis and evolution of framboidal pyrite and its implications for the ore-forming process of Carlin-style gold deposits, southwestern China: in Ore Geology Reviews v.102, pp. 426-436.
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