新疆哈图金矿成矿流体地球化学

ORE FORMING FLUID GEOCHEMISTRY OF THE HATU GOLD DEPOSIT IN XINJIANG, NORTHWEST CHINA

新疆哈图金矿床赋存在石炭系基性火山岩－火山碎屑岩中，矿体受古火山口断裂系控制。矿脉内流体包裹体较为丰富，主要为气液相ＮａＣｌ－Ｈ２Ｏ包裹体和少量的ＮａＣｌ－ＣＯ２－Ｈ２Ｏ包裹体。成矿热液中富含ＣＯ２、Ｎ２、Ｎａ＋、Ｋ＋、Ｃｌ－和ＳＯ２－４，而所含的成矿元素以Ａｕ－Ａｓ－Ａｇ－Ｓｂ组合为特征。成矿热液为低盐度流体，主成矿阶段的盐度为４．１ｗｔ％～６．３ｗｔ％ＮａＣｌ，密度为０．８８～０．８０ｇ／ｃｍ３，ｆＯ２为１０－３５～１０－３１Ｐａ，Ｅｈ为０．６０～０．８０ｅＶ，为还原环境。金沉淀成矿的最佳温度为２３０～２６０℃。哈图金矿成矿热液不是典型的岩浆热液，而是受到了古大气水混入的火山晚期热液。流体不混溶、水－岩反应及古大气水的混入是造成本区金沉淀成矿的主要因素。

The Hatu gold deposit is located in western Junggar of Xinjiang, adjacent to Kazakhstan, lying in north limb of Dalabute synclinorium of Junggar Hercynian folding belt. Wall rocks of the deposit are lower Carboniferous basalt pyroclastic rocks.Orebodies are controlled by fault system of the old crater.Two ore types,quartz vein and altered rock,have been found in the mine.The ore veins contain abundant fluid inclusions,which are mainly two phase gas liquid NaCl H 2O and three phase NaCl CO 2 H 2O with liquid CO 2 Ore forming fluids are rich in CO 2,N 2,Na +,K +,Cl - and SO 2- 4,but merely contain simple ore forming elements characterized by Au As Ag Sb.Ore forming fluids are of low salinity.In the main mineralizing stage,salinity is 4 1 wt%～6 3 wt% NaCl equiv.,density 0 88 g/cm 3, f O 2 10 -35 ～10 -31 Pa,and Eh 0 60～0 80 eV.The fluids in the inclusions have a wide range of homogenization temperatures from 160℃ to 360℃,but the best temperature range for gold deposition is from 230℃ to 260℃.Quartz from auriferous veins has δ 18 O values ranging from 15 4‰ to 17 5‰.Calculated δ 18 O and δ D values for the ore forming fluids range from 6 0‰ to 11 7‰ and -86‰ to -111‰ respectively,suggesting derivation from later volcanic fluids mixed with meteoric water.Fluid immiscibility and fluid rock interaction may be the main causes for gold deposition in the mine.