内蒙古1017高地银多金属矿床40Ar／39Ar年龄及地质意义

1017高地银多金属矿床位于内蒙古自治区东乌珠穆沁旗境内，是近几年新发现的与华力西中期岩浆岩有关的小型银多金属矿床。矿区大地构造位置处于位于西伯利亚板块东南缘查干敖包．奥尤特．朝不楞早古生代构造．岩浆岩带东段。银多金属矿体主要赋存在上泥盆统安格尔音乌拉组砂岩和华力西中期二长花岗岩中，矿石工业类型主要为石英脉型矿石和蚀变二长花岗岩型矿石。利用40Ar-39Ar同位素定年方法对1017高地蚀变岩型银多金属矿石中热液绢云母进行同位素定年，绢云母40Ar-39Ar坪年龄to=（301．2±1．8）Ma（26），正等时线年龄ti=（300．2±3．1）Ma（26），反等时线年龄ti=（300．0±3．5）Ma（2σ），测试结果可信。测试结果表明1017高地银多金属矿床形成于华力西中期，为东乌旗地区第一个Ag、Pb、Zn等多金属成矿高峰期，其成矿动力学背景为古蒙古洋壳向西伯利亚板块俯冲造山环境。

40Ar/39Ar age and its geological significance of 1017 highland Ag polymetallic deposit in Dong Ujimqin Banner,Inner Mongolia

Located in the easternmost part of Early Paleozoic Chaganobo-Aououte-Chaobuleng tectono- magmatic belt along the southeastern edge of the Siberian plate, 1017 highland Ag polymetallic deposit in Dong Ujimqin Banner, Inner Mongolia is a small deposit which has been discovered in recent years and has close relationship with middle-stage Hercynian magmatic rocks. The ore bodies mainly occur in sandstone of the Upper Devonian Angeeryinwula Formation and monzonitic granite of the middle-stage Hercynian and the commercial types of ore include quartz-vein type and altered- monzonitic granite type. 40Ar-39Ar dating of sericite from altered rock, yield a plateau age of （301.2±1.8） Ma （2σ） an isochron age of （300.2±3.1） Ma （2σ） and an inverse isochron age of （300.0±3.5） Ma （2σ）. The result indicates that 1017 Highland Ag polymetallic deposit formed in the middle-stage Hercynian, which was the first silver, lead and zinc metallogenic peak in Dong Ujimqin Banner region and geodynamically corresponded to the subduction of paleo-Asian oceanic crust underneath the Siberian plate.