柴达木盆地北缘全吉地块东端变基性岩体LA-ICP-MS锆石U-Pb年龄:中元古代陆块裂解的证据  

LA-ICP-MS zircon U-Pb age of meta-basic plutons in eastern Quanji massif:evidence for Mesoproterozoic continental break-up

作　　者：廖梵汐[1] 龚松林[2] 董彦君[1] 王勤燕[1] 张璐[1] 陈能松[1,3] 

机构地区：[1]中国地质大学地球科学学院,湖北武汉430074 [2]中国地质大学教育部长江三峡地质灾害研究中心,湖北武汉430074 [3]中国地质大学地质过程与矿产资源国家重点实验室,湖北武汉430074

出　　处：《地质通报》2012年第8期1279-1286,共8页Geological Bulletin of China

基　　金：国家自然科学基金项目<全吉地块元古代镁铁质岩的岩石成因和对塔里木克拉通古地幔性质演化和构造演化的启示>(批准号:41172069);<全吉克拉通残片基底早元古代片麻状花岗岩成因背景和基底地壳演化>(批准号:40972042)

摘　　要：全吉地块东端古元古代二长花岗片麻岩中普遍发育变质的基性岩体,它们的形成时代、变质作用时代和对地块基底构造演化的指示意义尚不清楚。应用LA-ICP-MS技术测定其中的一个变基性岩体的锆石U-Pb年龄,获得的10个测点数据显示,锆石受到热事件的强烈改造而发生严重铅丢失,但拟合的不一致线仍给出相关性较好的上交点年龄1712Ma±47Ma和下交点年龄472Ma±29Ma,MSWD=1.4。这表明,变质基性岩的原岩形成于中元古代早期,是全吉地块在古元古代末期汇入Columbia超大陆之后于中元古代早期初始裂解而侵位的基性岩体。这些基性岩体在早古生代卷入了柴北缘碰撞带而发生角闪岩相变质作用,并受到构造肢解。The meta-basic plutons are extensively developed within the Paleoproterozoic monzogranitic gneiss in the eastern most Quanji massif;however,their formation and metamorphic ages and implications for the basement tectonic evolution remain unclear.In this paper,the zircon U-Pb age of one of the meta-basic plutons was determined with LA-ICP-MS.Ten analytical data show strong lead loss due to thermal events,but their discordant line remains well correlated with the upper intercept age of 1712±47 Ma and lower intercept age of 472±29 Ma,MSWD=1.4.The dating result indicates that the protolith of this pluton was formed in the early Mesoproterozoic,being the product of the initial break-up process after the assembly of the Quanji massif with the supercontinent Columbia in the Late Paleoproterozoic.The proton then underwent amphibolite facies metamorphism and structural dismantling resulting from its being involved into the North Qaidam Collision Zone in the Early Paleozoic.

关 键 词：全吉地块 变基性岩体 LA-ICP-MS锆石U-PB定年 中元古代大陆裂解 

分 类 号：P588.34[天文地球—岩石学] P597[天文地球—地质学]