北阿尔金地区大平沟金矿H-O-S-Pb同位素地球化学特征对金矿成因的启示

大平沟金矿床是北阿尔金地区典型金矿床之一，矿化类型以钾长石-石英脉型和蚀变岩型为主，矿体赋存于近东西向韧性剪切带中，围岩为太古宇米兰岩群钾长变粒岩。矿石矿物以黄铁矿为主，另有少量褐铁矿和自然金等。大平沟金矿床含金石英脉中石英的δ¹⁸O_VSMOW值为12.4‰~15.3‰，估算的流体δ¹⁸O_H2O值介于7.4‰~10.3‰之间，石英中流体包裹体的氢同位素为-97‰~-66‰，表明成矿流体以变质流体来源为主；含金石英脉中硫化物的δ³⁴S_VCDT值为6.9‰~8.3‰，主要为壳源硫，与典型造山型金矿的硫值一致；硫化物的²⁰⁶Pb/²⁰⁴Pb值为18.310 1~19.373 9，²⁰⁷Pb/²⁰⁴Pb值为15.587 2~15.654 1，而²⁰⁸Pb/²⁰⁴Pb值为38.119 1~39.143 9，反映硫化物的铅来源具有造山带铅特征。综合分析认为，大平沟金矿床属于造山型金矿，其形成受近东西向次级断裂和韧性剪切带控制，成矿流体以变质流体为主，成矿物质来源于太古宙深变质岩。

H-O-S-Pb Isotopic Geochemistry of Dapinggou Gold Deposit in Northern Altun and Its Implications for Ore Genesis

Dapinggou gold deposit is one of the typical gold deposits in Northern Altun. The deposit is characterized by K-feldspar quartz vein-type and altered rock-type mineralization. The gold mineralization occurs within near the E-W ductile shear zone with the K-feldspar leptynite of Archaean Milan Group as the principal host rock. The ore minerals are mainly pyrite, with minor limonite and natural gold. The measured δ¹⁸O_VSMOW values for the gold-bearing quartz range from 12.4‰ to 15.3‰, the estimated δ¹⁸O_H2O fluid values range from 7.4‰ to 10.3‰, and the δD_VSMOW values of fluid inclusions in quartz range from-97‰ to -66‰, indicating that the ore-forming fluid is dominated by metamorphic sources. The δ³⁴S_VCDT values of sulfide minerals range from 6.9‰ to 8.3‰ in accordance with those of the typical orogenic gold deposits. The ²⁰⁶Pb/²⁰⁴Pb ratios of sulfides range from 18.310 1 to 19.373 9, ²⁰⁷Pb/²⁰⁴Pb ratios from 15.587 2 to 15.654 1, and the ²⁰⁸Pb/²⁰⁴Pb ratios from 38.119 1 to 39.143 9, indicating the lead source of sulfide the same as the orogenic type. It is proposed that Dapinggou gold deposit can be classified as the orogenic gold deposit, the gold formation is controlled by the near EW secondary fault and the ductile shear zone, the metallogenic material is derived from the Archaean metamorphic rocks, and the ore-forming fluids are mainly metamorphic fluids.