西天山博故图金矿床H-O-S-Pb同位素示踪和Re-Os法测年  

H-O-S-Pb isotopic tracing and Re-Os dating of Bogutu gold deposit,western Tien Shan,Xinjiang

作　　者：孙升升 薛春纪[1] 陶剑丰 季海强 

机构地区：[1]地质过程与矿产资源国家重点实验室,中国地质大学地球科学与资源学院,北京100083

出　　处：《岩石学报》2016年第5期1346-1360,共15页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(U1303292);国家科技支撑计划(2011BAB06B02);中国地质调查项目(1212011085069)联合资助

摘　　要：博故图金矿床是西天山近年新发现的一处大型金矿床,位于新疆特克斯县城北东部依什基里克成矿带东段。金矿体赋存于下石炭统大哈拉军山组火山岩地层中的NW或EW向断裂构造破碎带内,呈脉状或透镜状。由金矿体到两侧火山岩地层围岩,基本对称依次出现硅化、黄铁绢英岩化、青磐岩化等热液蚀变。矿石矿物主要有黄铁矿、毒砂、方铅矿、闪锌矿、银金矿、辉银矿,脉石矿物主要有石英、玉髓、方解石、绢云母等。电子探针观测发现矿石中自然金主要在黄铁矿内呈包裹金,或在其他金属硫化物粒间赋存。含金脉石英氢氧同位素分析和计算表明,成矿流体δ18O水-SMOW=-4.2‰~1.4‰,δDV-SMOW=-111.2‰^-94.1‰,主体属循环的大气降水。矿区金属硫化物的δ34SV-CDT范围为-7.5‰~5.8‰,均值为0.45‰,接近于原始地幔硫,矿石铅和火山岩铅同位素组成特征基本一致,206Pb/^(204)Pb=18.243~18.535,207Pb/^(204)Pb=15.565~15.753,208Pb/^(204)Pb=38.021~38.647,结合载金黄铁矿的187Os/188Os(i)平均值为0.774±0.076,γOs(t)平均值为520,显示成矿物质主要来自赋矿围岩大哈拉军山组火山岩。载金黄铁矿的Re-Os等时线年龄为356.1±9.3Ma(MSWD=16),矿区火山岩年龄为344±6Ma^368.3±1.7Ma。博故图金矿床应为低硫型浅成低温热液金矿。The Bogutu larger gold deposit,western Tien Shan,was discovered recently. It was located in the eastern Yishijilike metallogenic belt,Xinjiang. Gold mineralization is hosted by volcanic rocks of the Lower Carboniferous Dahalajunshan Formation. The ore bodies are bedded and lenticular and controlled by EW and NW trending faults. The main wall-rock alteration consists of three zoning; they are silicification,beresitization,propylitization from the orebody to the wallrock. Ore minerals mainly consist of pyrite,arsenopyrite,galena,sphalerite,electrum,argentite,whereas gangue minerals mainly consist of quartz,chalcedony,calcite,sericite in the ore. By electron probe scanning of the main minerals,the gold was often wrapped in pyrite or embodied as intergranular. Theδ18OH_2O-SMOWof vein quartz is from-4. 2‰ to 1. 4‰,δDV-SMOWfrom-111. 2‰ to-94. 1‰,showing that ore-forming fluids were mainly circulating atmospheric water. The ore δ34SV-CDT（ from-7. 5‰ to 5. 8‰,the mean value 0. 45‰） is close to the mantle value of 0‰. The ore Pb isotope composition is similar to that of the volcanic rock,206 Pb /^（204）Pb ranges from 18. 243 to 18. 535,207 Pb /^（204）Pb from 15. 565 to 15. 753,208 Pb /^（204）Pb from 38. 021 o 38. 647. The radiogenic initial187 Os /188Os（ i）of gold-bearing pyrite is 0. 774 ±0. 076,the γOs（ t）mean value is 520,indicating that the metal was sourced from hosted volcanic rocks of the Lower Carboniferous Dahalajunshan Formation. Re-Os dating of gold-bearing pyrite yielded an isochron age of the 356. 1 ± 9. 3Ma（ MSWD = 16）,which is closed the ages（ 344 ± 6Ma to 368. 3 ± 1. 7Ma） of regional volcanic rocks. The Bogutu gold deposit is a low-sulfidation epithermal gold deposit.

关 键 词：H-O-S-Pb同位素示踪 RE-OS测年 博故图金矿 浅成低温热液金矿 新疆西天山 

分 类 号：P597[天文地球—地球化学]