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Huiliang Xiao, Nanjing Institute of Geology and Mineral Resources (China)
Yongguan Dong, Nanjing Institute of Geology and Mineral Resources (China)
Lezhu Chen, Nanjing Institute of Geology and Mineral Resources (China)
Hanyu Wu, Nanjing Institute of Geology and Mineral Resources (China)
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The Duolanasayi gold deposit, located in 180 km NWW of Altay city in Xinjiang, is a middle-large scale telluride-type gold deposit controlled by the brittle-ductile shear. It's forming process is related to the albite-granite dykes and post-stage magma evolution of the rift valley dragging of the continental margin in early Palaeozoic. After Caledonian folding, this area developed open fissure and got into the rift stage in both side of south and north of the area in early stage of late Palaeozoic. There was orogenic belt developed in middle-late Variscian. The ore bodies occurr as the albitite veins (mylonitic albitite and mineralized albite-granite), and the mineralized phyllite presents an opposite ¡°S¡± shape in the SN strike. There are a lot of tellurides such as calaverite, petzite, sylvanite in the ores. Nine gold ore bodies and dozens of gold mineralizing sites were explored in the gold deposit district. The ore bodies occur as vein, lens or lenticular shape. There are two major ore bodies in the ductile shear zone. With regard to the north major ore body, it is 1000 m long and 2.55 m wide on an averaging, and the drilling has revealed that the depth of the ore body is over 400 m. The maximum gold grade is 1152.0¡Á10-6, the average grade is 7.34¡Á10-6; Concerning the south major ore body, it is 1100 m long and 0.24-11.98 m wide, its depth of the ore body is over 200 m. The average gold grade is 7.34¡Á10-6.
There are three ore types in the Duolanasayi gold deposit: the pyrite-gold bearing altered rock, the gold-bearing albite-quartz and ferrohydrite-gold bearing quartz. Gold minerals in the Duolanasayi deposit are dominated by native gold and gold-bearing tellurides. There are three gold-bearing types of native gold: in inclusion, in crack of minerals and in crack of minerals crystal. The percentage of Au in native gold is high (£¾950) , and there are a small of Ag, Hg, Bi, Te, Fe etc. The characteristic gold minerals of the gold-bearing tellurides are calaverite, petzite, sylvanite, montbrayite.
The studies of fluid inclusions indicate that the homogenization temperatures rang from 160¡æ to 315¡æ. The mineralization pressures are of from 21.0 ¡Á10 Mpa to 64.5 Mpa. The salinities of fluids rang from 2.75-10.86 NaCl (%Wt) in gas-solution inclusions and 35.57-37.22 NaCl (%Wt) in halite-bearing multi-phase inclusions. The sulfur, hydrogen, oxygen and strontium isotopic compositions are: ¦Ä34S=-2.46¡ë¡ª-7.02¡ë;¦Ä18O H2O=1.65¡ë¡ª12.4¡ë;¦ÄD=-132.2¡ë¡ª-51.8¡ë . The low initial (87Sr/86Sr) i rate (0.7043¡ª0.7073) suggests the ore-forming fluid of the Duolanasayi gold deposit was a kind of mixed hydrothermal solution. It was mainly composed of magmatic water, metamorphic water, meteroric water and formation water in rocks. The magmatic water in early mineralization is mantle fluid. HAu£¨HS£©20¡¢Au£¨HS£©2- ¡¢Au(HTe) 2 -¡¢Au(Te2) -¡¢Au2 (Te2) 0¡¢Au(Te2) 2 3-and [AuCl2]- are likely the principal gold complexes in the ore-bearing fluid.
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