额尔古纳地块新元古代岩浆作用与微陆块构造属性:来自侵入岩锆石U-Pb年代学、地球化学和Hf同位素的制约  

Neoproterozoic Magmatic Events and Tectonic Attribution of the Erguna Massif:Constraints from Geochronological,Geochemical and Hf Isotopic Data of Intrusive Rocks

作　　者：赵硕[1] 许文良[1] 唐杰[1] 李宇[1] 郭鹏[1] 

机构地区：[1]吉林大学地球科学学院,吉林长春130061

出　　处：《地球科学（中国地质大学学报）》2016年第11期1803-1829,共27页Earth Science-Journal of China University of Geosciences

基　　金：教育部博士点基金项目(No.20120061110048);国家自然科学基金项目(No.41272077);中国地质大学(武汉)地质过程与矿产资源国家重点实验室开放基金项目(No.GPMR201503);吉林大学研究生创新基金资助项目(No.2016102)

摘　　要：对额尔古纳地块新元古代花岗岩进行了锆石LA-ICP-MSU-Pb年代学、岩石地球化学和锆石Hf同位素研究，以便对其新元古代岩浆作用历史与微陆块构造属性给予制约．所测花岗质岩石中锆石的CL图像特征和Th／U比值（O．17-1．46）显示其为岩浆成因．测年结果并结合前人定年结果，可以判定额尔古纳地块上至少存在-929Ma、-887Ma、-850Ma、-819Ma、-792Ma、-764Ma和-738Ma岩浆事件．岩石地球化学特征显示，-887Ma花岗岩为一套后碰撞花岗岩类；而850-737Ma花岗质岩石整体上属于A-型花岗岩，也有部分岩体（漠河、阿木尔、碧水和室韦岩体）显示I-型花岗岩特征．锆石Hf同位素特征反映这些花岗岩的源区既有中一新元古代（TnMz-884-1563Ma）新增生地壳物质的部分熔融，同时伴有少量古老地壳物质的混染，也有残留的古老中基性下地壳物质的部分熔融．综合研究区新元古代侵入岩的地球化学特征，同时对比新元古代全球构造热事件，认为额尔古纳地块上新元古代岩浆活动记录了Rodinia超大陆形成和演化过程中的地壳响应：927-880Ma的岩浆作用应是Rodinia超大陆汇聚造山的产物；而850-737Ma的岩浆作用应是对Rodinia超大陆快速裂解的记录．通过岩浆事件对比发现，额尔古纳地块与邻近的西伯利亚南缘微陆块（如中蒙古地块和图瓦地块）具有亲缘性，而与塔里木板块和华南板块至少在新元古代岩浆活动上具有一定的相似性，而明显区别于华北板块和西伯利亚板块．This paper presents LA-ICP-MS zircon U-Pb dating, major and trace elements, and Hf isotope data of the Neoproterozoic granitoids in the Erguna Massif with the aim of constraining the Neoproterozoie tectonic evolution and tectonic attribution of the Erguna Massif. Zircons from these granitoids are of magmatic origin in accordance with CL images and high Th/U ratios （0.17--1.46）. The zircon dating results, together with previously published age data, demonstrate that the Neoproterozoic magrnatisms in the Erguna Massif can be subdivided into seven stages about 929 Ma, about 887 Ma, about 850 Ma, about 819 Ma, about 792 Ma, about 764 Ma and about 738 Ma. Geochemically, about 887 Ma granites are similar to those of post-collisional granites, whereas 850--737 Ma granit- oids are similar generally to A-type granites, except for some samples （collected from Mohe, Amuer, Bishui and Shiwei plutons） which are similar to I-type granites. Zircon Hf isotopic compositions indicate that their primary magmas could have originated not only by partial melting of a depleted lower crust that accreated during the Meso-Neoproterozoic （T =884--1 563 Ma）, with a contribu- tion of ancient crustal material in their petrogenesis, but also by partial melting of the residual ancient mafic crustal material. These ge-ochcmical data, combined with the published data and the global magmatic-tectonic-thermal events, indicate that Neoproterozoic mag- matic events within the Erguna Massif recorded crustal evolution as a result of the assembly and breakup of the Rodinia supercontinent： magmatisms between 927 Ma and 880 Ma were the result of collision-orogeny during the stage of assembly of the Rodinia superconti- nent, whereas the 850--737 Ma magmatisms recorded the breakup of the Rodinia supercontinent. The Erguna Massif has an affinity to the adjacent massifs （〈g. Central Mongolia and Tuva massifs） near the southern margin of the Siberian block, and is similar to the Ta rim and South China blocks at least in terms of these Neopr

关 键 词：额尔古纳地块 新元古代 岩浆作用 年代学 地球化学 构造属性. 

分 类 号：P597[天文地球—地球化学]