甘肃岗岔金矿床同位素地球化学特征及成矿物质来源探讨  

Stable Isotope Geochemical Characteristics and Ore-Forming Material Source of the Gangcha Gold Deposit,Gansu Province,China

作　　者：李杰[1,2] 申俊峰[1] 李金春 刘圣强[1] 王冬丽[1] 张弘[1] LI Jie SHEN Jun-feng LI Jin-chun LIU Sheng-qiang WANG Dong-li ZHANG Hong(China University of Geoseiences , Beijing 100083, China Hui Tian-ran Mining Limited, Lanzhou 730000, China Inner Mongolia Ninth Geology Mineral Exploration and Development Institute ,Xilinhaote Inner Mongolia 026000, China)

机构地区：[1]中国地质大学(北京)地球科学与资源学院,北京100083 [2]内蒙古第九地质矿产勘查开发有限责任公司,内蒙古锡林浩特026000 [3]惠天然矿业有限公司,兰州730000

出　　处：《矿物岩石地球化学通报》2016年第5期976-983,共8页Bulletin of Mineralogy, Petrology and Geochemistry

基　　金：国家自然科学基金项目(41072070)

摘　　要：岗岔金矿床为近年来新发现的中型受断裂构造控制的浅成低温热液矿床,为了探讨其成矿物质来源,对主矿脉Au3号脉矿体中的黄铁矿、赋矿围岩全岩的S、Pb同位素和矿脉中石英的H、O同位素进行了分析测试。结果显示,矿体中黄铁矿δ34S变化范围为0.6‰~1.3‰,均值为0.975‰,同位素组成比较均一,具有明显的幔源硫特征;矿体黄铁矿与赋矿围岩具有相近的Pb同位素组成,其206Pb/204Pb值为17.935~18.208(均值为18.090),207Pb/204Pb值为15.539~15.74(均值为15.568),208Pb/204Pb值为38.093~38.478(均值为38.280);μ值(238U/204Pb)介于为9.39~9.53,ω值为36.81~38.14,暗示其铅源为壳幔混合来源,且受造山作用与岩浆作用影响较为明显。矿脉中石英H、O同位素测试获得:δDH2O值为-88.6‰^-76.7‰(均值为-80.92‰),δ18OH2O值为6.53‰~8.63‰(均值为7.46‰),显示出岗岔金矿床成矿热液流体主要来自岩浆,混有少量大气降水。上述S、Pb、H、O同位素特征表明岗岔金矿床成矿物质和流体来自壳幔混源且以幔源为主。The Gangcha gold deposit is a fault-controlled medium sized epithermal gold deposit which was recently discov-ered in Gansu Province.In order to discuss the ore-forming material source,S and Pb isotopes of pyrite fromof the Lode Au3 and of host rocks,and H and O isotopes of gangue quartz samples have been analyzed in this paper.The results indi-cate that δ34S values of pyrites in ores change from 0.6‰ to 1.3‰,with average of 0.975‰,indicating that they have relatively homogeneous sulfur isotopic compositions and obvious features of mantle sourced sulfur.The pyrite and host rock have similar Pb isotopic compositions,with their 206Pb/204Pb values changing from 1 7.935 to 1 8.208（average 1 8.090）, 207Pb/204Pb values changing from 15.539 to 15.74（average 15.568）,and 208Pb/204Pb values changing from 38.093 to 38.47 （average 38.280）,respectively.The μand ω（232 Th/204Pb）values of Pb isotopic compositions change from 9.39 to 9.53 and from 36.81 to 38.1 4,respectively.This indicates that Pb was derived from the mixed source of lower crust and mantle ,with obvious influence of the magmatism and orogenesis.H,O isotopes of inclusion waters in quartz veins are ana-lyzed with the δDH2O values varying from -88.6 to -76.7‰（the average -80.92‰）and δ18OH2O values ranging from 6.53 to 8.63‰（average 7.46‰）.It shows that the ore-forming fluid of the Gangcha deposit is mainly originated from magmatic fluid with a minor input of meteoric water.Above features of the S,Pb,H,O isotopes indicate that the ore-forming mate-rials and fluid of the Gangcha deposit were mainly derived from the mantle with minor input of crustal materials.

关 键 词：稳定同位素 地球化学 成矿物质 幔源 金矿床 甘肃省 

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