东天山雅满苏铁矿床矽卡岩成因及矿床成因类型  

The Genesis of the Skarn and the Genetic Type of the Yamansu Iron Deposit,Eastern Tianshan,Xinjiang

作　　者：李厚民[1] 丁建华[1] 李立兴[1] 姚通[1,2] 

机构地区：[1]中国地质科学院矿产资源研究所,国土资源部成矿作用与资源评价重点实验室,北京100037 [2]中国地质大学地球科学与资源学院,北京100083

出　　处：《地质学报》2014年第12期2477-2489,共13页Acta Geologica Sinica

基　　金：国家自然科学基金项目(编号41272102);国家重点基础研究发展规划"973"项目(编号2012CB416801)联合资助成果

摘　　要：新疆东天山雅满苏铁矿床是该区乃至我国产于海相火山岩中的典型铁矿床,其矿床成因类型长期以来一直有海相火山岩型和矽卡岩型之争,争论的焦点是该矿床中矽卡岩的成因,影响了关键控矿要素的确定和找矿标志的建立。为了探讨矽卡岩的成因,本文测定了穿插铁矿体和矽卡岩的辉绿岩脉的锆石SHRIMP U-Pb年龄,采用XRF方法测定了雅满苏铁矿区火山岩、火山沉积岩和矽卡岩的主量元素含量,采用电子探针方法分析了该矿床不同产态不同期次矽卡岩中石榴石的矿物组成。测得辉绿岩脉锆石年龄为335Ma,将雅满苏矿区铁矿化和矽卡岩的形成时代限定于335Ma之前,表明矿化蚀变与火山岩同期,是雅满苏组火山岩喷发期热液交代作用的产物。岩矿鉴定也显示热液改造首先形成葡萄石,进而由于流体中铁质的加入形成石榴石。两期石榴石的矿物化学特征表明早期形成的石榴石富铁;晚期形成的石榴石铁质含量低,并有磁铁矿和黄铁矿等金属矿物与其共生。由于该矽卡岩的形成与火成岩体接触带的交代作用没有明显成因联系,因此笔者认为该矿床中的矽卡岩属广义矽卡岩,矿床成因类型归为海相火山岩型铁矿床更合理。The Yamansu iron deposit developed in Eastern Tianshan,Xinjiang,is one of the typical iron deposits hosted in submarine volcanic rocks in this area.Due to the controversy on the genesis of the skarn,some researchers suggest it is of submarine type,while others consider it is a skarn deposit.This debates has disturbed the determination of the key metallogenetic factors and the prospecting guidelines.In order to study the genesis of the skarn in the Yamansu iron deposit,in this study,we have obtained the SHRIMP U-Pb ages of the zircons from the diabase dyke which cuts the skarn bodies,the major elements compositions of the volcanic rocks,volcanic-sedimentary rocks and skarn by XRF,and the mineral chemistry of various garnets by EPMA.The age data of the diabase dyke is 335Ma,which indicates the ages of the skarn and iron mineralization are earlier than 335Ma,being coeval with the volcanic activities.Under the microscope,we have found albite in the volcanic rocks has been changed into prehnite initially,then into garnet.There are two stages of garnets.The earlier garnet is mainly brown andradite,while the later garnet is colourless grossular-andradite intergrown with magnetite and pyrite.In view of no obvious genetic relationship between the skarn and intrusive bodies,we suggest that the skarn in the Yamansu iron deposit belongs to the ＂general skarn＂,and this deposit is an iron deposit of submarine volcanic type.

关 键 词：锆石SHRIMP U-PB年龄 主量元素 广义矽卡岩 海相火山岩型铁矿床 新疆雅满苏 

分 类 号：P618.31[天文地球—矿床学]