二连盆地巴彦乌拉铀矿区花岗岩锆石U-Pb年龄和Hf同位素特征及地质意义  

Zircon U-Pb ages and Hf isotopic compositions of the granites from Bayanwula area and their geological significance

作　　者：刘佳林[1] 刘武生[1] 虞航[1] 章展铭 LIU Jialin;LIU Wusheng;YU Hang;ZHANG Zhanming(CNNC Beijing Research Institute of Uranium Geology,Beijing 100029,China)

机构地区：[1]中核集团核工业北京地质研究院,北京100029

出　　处：《地质通报》2020年第8期1285-1295,共11页Geological Bulletin of China

基　　金：中核集团项目《二连基地砂岩型铀矿地质数字平台和大数据找矿预测》(编号:地LCEQ03);《北方重点盆地砂岩型铀矿资源扩大与靶区优选》(编号:地LTD1601)。

摘　　要：二连盆地中部巴彦乌拉地区位于中亚造山带东段,发育有多个砂岩型铀矿床(点)。利用LA-ICP-MS锆石U-Pb同位素和Hf同位素分析对巴彦乌拉地区巴音宝力格隆起东部花岗岩开展了年代学研究。结果显示,2个样品的锆石U-Pb年龄在292±3~288±2 Ma之间,与巴彦乌拉地区巴音宝力格隆起中西部发育的早二叠世花岗岩及流纹岩的年龄范围基本一致。结合区域成岩年代学数据可知,巴彦乌拉地区巴音宝力格隆起发育一条主要由晚石炭世—早二叠世花岗岩及火山岩组成的岩浆岩带。锆石Hf同位素数据显示,2个花岗岩样品的εHf(t)值为+10.6^+18.2,表明其源区为新生下地壳物质。综合区域地质特征可知,中亚造山带东段显生宙的构造-岩浆活动与二连盆地中部及巴彦乌拉地区赛汉组上段砂岩型铀成矿作用关系密切,为砂岩型铀矿床的形成提供了一系列有利条件。The Bayanwula area is located in the middle part of the Erlian Basin,eastern part of the Central Asian orogenic belt,and hosts some sand-type uranium deposits.In this paper,the authors present two LA-ICP-MS zircon U-Pb ages and Hf isotopic compositions for granites from the study area,which show that the emplacement ages of these granitic rocks are 292±3 Ma and 288±2 Ma.Theses ages are consistent with those of granitic and volcanic rocks occurring in the Bayinbaolige horst of the Bayanwula area.The data obtained by the authors and previously published data indicate that a magma belt consisting of Late Carboniferous-Early Permian granitic and volcanic rocks were developed in the Bayinbaolige horst of the Bayanwula area.Zircon Hf isotopic compositions show that two granite samples haveεHf(t)values of+10.6 to+18.2,which are similar to those of the Early Permian granitic rocks located on the Bayinbaolige horst of the study area,indicating that the granites were derived from the partial melting of juvenile lower crust.Integrated with geological data,this study indicates that the formation of the sand-type uranium deposits developed in the upper member of the Saihan Formation was associated with tectonic-magmatism processes that happened in the eastern part of the Central Asian orogenic belt during Phanerozoic,which provided many optimum conditions for these sand-type uranium deposits.

关 键 词：二连盆地 巴彦乌拉 砂岩型铀矿 锆石U-Pb年龄 HF同位素 

分 类 号：P619.14[天文地球—矿床学] P597[天文地球—地质学]