东天山小尖山金矿床成矿流体特征及成矿模式探讨  

The characteristics and evolution of the ore-forming fluids in the Xiaojianshan gold deposit,eastern Tianshan Mountains

作　　者：蒋东祥 毛启贵[2] 刘家军[3] 于明杰[2] 卫晓峰 JIANG Dongxiang;MAO Qigui;LIU Jiajun;YU Mingjie;WEI Xiaofeng(Xi’an Center of Mineral Resources Survey,Xi'an,710100;Beijing Institute of Geology for Mineral Resources,Beijing,100012;School of Earth Science and Resource,China University of Geosciences,Beijing,100083)

机构地区：[1]中国地质调查局西安矿产资源调查中心,西安710100 [2]北京矿产地质研究院,北京100012 [3]中国地质大学地球科学与资源学院,北京100083

出　　处：《地质学报》2021年第2期449-462,共14页Acta Geologica Sinica

基　　金：国家重点研发计划项目(编号2017YFC0601201);国家重点基础发展研究计划项目(编号2014CB440803);中国地质调查局公益性地质调查项目(编号DD20160071)资助成果。

摘　　要：小尖山金矿床产于东天山康古尔韧性剪切带南缘,对该矿床流体特征和矿床成因类型了解较少。矿区普遍发育低绿片岩相变质,矿床由多条走向为100°~120°的陡倾斜蚀变岩型矿体组成,金平均品位3.11×10^(-6)~24.99×10^(-6);成矿过程可划分为3个阶段:(1)黄铁矿-磁铁矿-绿泥石-绢云母-石英阶段;(2)黄铁矿-黄铜矿-自然金-石英-绿泥石阶段;(3)石英-方解石-贫硫化物阶段。本文通过对矿床不同成矿阶段石英脉内发育的流体包裹体进行了岩相学、显微测温与氢氧同位素研究分析,发现矿床主要发育H_(2)O-CO_(2)及气液两相流体包裹体,从早至晚成矿过程中流体内CO_(2)包裹体逐渐减少,气液两相包裹体内气液比逐渐减小。各成矿阶段包裹体显微测温结果表明,从早至晚成矿流体均一温度分别为216.9~396.4℃、183.1~319.2℃与145.1~220.8℃;成矿流体盐度分别为1.40%~10.11%NaCleq、1.91%~11.22%NaCleq与1.63%~6.74%NaCleq,成矿流体属于中低温、中低盐度的NaCl-H_(2)O-CO_(2)体系,并经历了从中温、中盐度流体向低温、低盐度流体的演化过程;成矿早阶段流体的δD_(V-SMOW)值为-22.550‰,δ^(18)O_(水)值为9.44‰,指示变质水成因;成矿晚阶段δD_(V-SMOW)值介于-41.913‰~-34.796‰之间,平均值为-37.413‰,δ^(18)O_(水)值介于1.99‰~3.98‰之间,平均值为2.99‰,指示混合水成因,但接近变质水;成矿流体主要为变质水,成矿早阶段至晚阶段具有从变质水向混合水演化的特征。综合分析,小尖山金矿床成因类型为造山型金矿,其成矿模式为早期韧性剪切变形过程中产生的变质流体在运移过程中萃取岩石中成矿物质,形成含金成矿流体,并在糜棱岩面理等裂隙处发生结晶作用,导致金的初步富集;晚期地壳快速抬升,地质体由韧性变形向脆-韧性、脆性变形转变,伴随有花岗岩脉的侵入,变质流体在运移过程中从流经岩石中淋滤萃取金等成矿物质,�The Xiaojianshan gold deposit is located at the southern margin of the Kanggur ductile shear zone in the eastern Tianshan Mountains.The fluid characteristics and genetic types of ore deposits are poorly understood.Low greenschist facies metamorphism is widely developed in the mining area.The deposit is composed of many steeply inclined altered rock ore bodies with an average grade of Au 3.11×10^(-6)~24.99×10^(-6),striking between 100°~120°.The metallogenic process can be divided into three stages:(1)pyrite-magnetite-chlorite-sericite-quartz stage,(2)pyrite-chalcopyrite-gold-quartz-chlorite stage,and(3)quartz-calcite-low sulfide stage.Based on the study of the fluid inclusions in quartz veins of different stages by petrography,microthermometry and H-O isotope,it appears that CO_(2)-bearing fluid inclusions and aqueous two-phase fluid inclusions existed in the Xiaojianshan gold deposit inearly to late stages.CO_(2)-bearing fluid inclusions decreased gradually and the ratio of gas to liquid for aqueous two-phase fluid inclusions was smaller.From early to late stages,microthermometry results show that the average homogenization temperature of fluid inclusions was 216.9~396.4℃,183.1~319.2℃and 145.1~220.8℃;salinity was 1.40%~10.11%NaCleq,1.91%~11.22%NaCleq,1.63%~6.74%NaCleq.The ore forming fluids were medium-low temperature and low salinity NaCl-H_(2)O-CO_(2)type solutions and the evolution was from medium temperature and salinity to low temperature and salinity.H-O isotopic composition indicates thatδD_(V-SMOW)values-22.550‰andδ^(18)O_(water)values 9.44‰in the early stage of mineralization indicating the genesis of the metamorphic water.In the late stage of mineralization,δD_(V-SMOW)values were-41.913‰~-34.796‰andδ^(18)O_(water)values were 1.99‰~3.98‰,with an average of-37.413‰and 2.99‰respectively indicating that fluids were mixed water and closed to metamorphic water.These results indicate that the source of ore-forming fluids was mainly metamorphic water,and there may be a mixture of m

关 键 词：流体包裹体 氢氧同位素 流体演化 东天山 小尖山金矿床 

分 类 号：P618.51[天文地球—矿床学]