东昆仑西段阿其音金矿成矿流体特征及其成因机制

Analysis of the Genesis and H−O−S−Pb Isotopic Characteristics of Aqiyin Gold Deposit in the Western Section of the East Kunlun

阿其音金矿是东昆仑西段近年来新发现的一处金矿产地,笔者对该矿床成矿期含黄铁矿石英细网脉型金矿石开展流体包裹体分析、石英脉中流体H−O同位素分析、黄铁矿及毒砂S−Pb同位素分析。结果显示,包裹体均一温度为167~356.9℃,盐度主要为3.21~9.99 wt%NaCleqv,密度为0.65~0.94 g/cm^(3),成矿流体具有中温、低盐度、低密度的特征。含矿石英脉δDV-SMOW值为−90.3‰~−98.7‰,δ^(18)O石英V-SMOW值为9.4‰~11.3‰。硫化物δ34S值为11.6‰~13.9‰,^(208)Pb/^(204)Pb值为38.067~38.651,^(207)Pb/^(204)Pb值为15.598~15.681,206Pb/^(204)Pb值为18.122~18.553,µ值为9.49~9.61。结合阿其音金矿成矿地质背景,认为含矿热液为变质水与大气降水的混合,S主要来源于动力变质作用,Pb显示出造山带铅源的特征,成因类型为造山型(构造蚀变岩型)金矿。

Aqiyin gold deposit is a newly discovered gold deposit in the western section of East Kunlun in recent years.In order to explore the genesis of the deposit,the characteristics of ore−forming fluid and the source of ore−forming materials,and establish the metallogenic model,the fluid inclusion analysis of pyrite bearing quartz fine mesh vein type gold ore in the metallogenic period was carried out,and the isotopic analysis of fluid H−O,pyrite and arsenopyrite S−Pb in quartz vein was carried out.The results show that the homogenization temperature of inclusions is 167~356.9℃,the salinity is mainly concentrated between 3.21~9.99 wt%NaCleqv,and the density is 0.65~0.94 g/cm^(3).The ore-forming fluid has the characteristics of medium temperature,low salinity and low density.The fluid inclusions in ore bearing quartz vein haveδDv-smow values of−90.3‰~−98.7‰,δ^(18)O of 9.4‰~11.3‰andδ34S of 11.6‰~13.9‰。The Pb isotopes of Au−bearing pyrite vary from 38.067 to 38.651,from 15.598 to 15.681,and from 18.122 to 18.533 for^(208)Pb/^(204)Pb,^(207)Pb/^(204)Pb and 206Pb/^(204)Pb ratios,respectively.The values ofµare from 9.49 to 9.61.Combined with the geological background of the Aqiyin gold deposit,the author hold that the ore-bearing hydrothermal fluid is a mixture of metamorphic water and meteoric water,sulfur is mainly derived from dynamic metamorphism,and lead shows the characteristics of lead source in orogenic belt.The genetic type is orogenic(tectonic altered rock type)gold deposit.