新疆望峰金矿区成矿流体的Si同位素示踪研究及其成矿意义  

A study of Si isotopic tracing of ore_forming fluid in Wangfeng gold orefield and its mineralization significance

作　　者：杨猛[1,2] 王居里[1] 王建其[1] 

机构地区：[1]大陆动力学国家重点实验室西北大学地质学系,陕西西安710069 [2]西北有色地质勘查局,陕西西安710054

出　　处：《矿床地质》2015年第2期352-360,共9页Mineral Deposits

基　　金：国家科技支撑计划项目"巴尔鲁克_谢米斯台大型矿床找矿靶区优选与评价(编号:2011BAB06B01_03)"和"西天山天格尔_依连哈比尔尕金矿带大型金矿床定位预测与找矿靶区评价技术与应用研究(编号:2006BAB07B04_05)"共同资助

摘　　要：新疆望峰金矿区金的成矿作用与硅化作用密切相关,文章通过对矿区典型矿体的赋矿围岩、蚀变岩石及矿石进行Si同位素组成研究,探讨了成矿流体中硅质来源、演化过程及其成矿意义。结果表明:1望峰金矿体围岩具有较均一的Si同位素组成,δ30Si=-0.2‰(n=3),显示了花岗质原岩Si同位素组成特征,动力变质作用对原岩硅同位素组成无明显影响;2蚀变岩石Si同位素组成均一性较高,δ30Si=-0.1‰(n=3),显示了花岗质原岩Si与成矿期热液Si的混合特征;3矿石Si同位素组成变化范围较大,不同类型矿石的Si同位素组成差异较明显:硅化蚀变糜棱岩型δ30Si=-0.5‰^-0.2‰(n=9),集中于-0.3‰^-0.2‰,平均-0.3‰;硅化蚀变岩型δ30Si=-0.3‰^-0.1‰(n=9),平均-0.2‰;热液石英脉型δ30Si=-0.3‰~0.1‰(n=6),平均-0.1‰。望峰金矿区金成矿流体中的硅质,主要来源于花岗质赋矿围岩。矿石中Si同位素组成变化较大,是富硅成矿流体演化过程中发生Si同位素动力学分馏的结果,矿体下部及矿区深部应有一定的找矿前景。Gold mineralization in the Wangfeng gold orefield is closely related to silicification. Analytical results of sili- con isotopes show that mylonitized country rocks have the data δ30Si = -0.2‰ （n = 3）, suggesting that dynamic metamorphism had no effect on silicon isotopic compositions d primary granitoids, whereas altered rocks shared even silicon isotopic compositions with δ30Si equal to - 0.1‰（ n = 3）, implying the mixture of magmatic and hy- drothermal silicon isotopic compositions in the process of mineralization. Gold ore shows a wide range of silicon isotopic composition characterized by different types of ore with diverse δ30Si values： δ30Si = -0.59 ‰ -- -0.2‰ （n = 9） mainly changing from -0.3‰ to -0.2‰ for silicified altered mylonite-type with an average of -0.3‰, δ30Si= -0.3‰-- -0.1‰ （n = 9） for silicified altered rock-type with an average of -0.2‰, and δ30Si= -0.3‰-0.1‰（ n = 6） for hydrothermal quartz vein-type with an average of -0.1‰. Based on the above analysis, the authors hold that granitoids provided the main silicon source for ore-forming fluid, and dy- namic fractionation of silicon happened in the process of gold mineralization. Fractionation strength of silicon iso- tope at the shallower mineralization level is stronger than that at the deeper level. Cold orebodies are likely to be found beneath the Wangfeng gold orefield.

关 键 词：地球化学 硅化作用 硅同位素 动力学分馏 硅源 碱交代 新疆望峰金矿 

分 类 号：P618.51[天文地球—矿床学] P597.2[天文地球—地质学]