塔里木北缘新元古代早期构造演化的锆石U-Pb年代学和地球化学约束  

Early Neoproterozoic Tectonic Framework of North Margin of Tarim Basin,Constraints from Zircon U-Pb Geochronology and Geochemistry

作　　者：杨鑫[1,2] 徐旭辉[1] 李慧莉[1] 蒋华山[3] 张继标[1] 钱一雄[1] 

机构地区：[1]中国石化石油勘探开发研究院,北京100083 [2]中国科学院油气资源研究重点实验室,甘肃兰州730000 [3]中国石化西北油田分公司勘探开发研究院,新疆乌鲁木齐830011

出　　处：《大地构造与成矿学》2017年第2期381-395,共15页Geotectonica et Metallogenia

基　　金：国家重大专项(2017ZX05005002);中石化科技部项目(P15090)资助

摘　　要：塔里木盆地被沙漠区覆盖,基底岩心样品对前寒武纪构造演化的研究具有重要意义。在前人研究基础上,结合盆地内钻井、地震资料,通过基底岩心样品的锆石U-Pb年代学和地球化学分析,为塔里木盆地北缘新元古代构造演化格架提供约束。LA-ICP-MS法给出片麻岩基底样品的加权平均年龄为822?7 Ma(置信度95%,MSWD=2.4),SHRIMP法在上覆震旦系砂岩中获得~2.5 Ga和2.1~1.8 Ga的两组锆石年龄。岩相学和元素地球化学特征显示二云斜长片麻岩样品的原岩为花岗闪长岩类,与相邻钻井揭示的青白口系基性岩墙都属于钙碱性–高钾钙碱性岩浆系列,具有相似的REE配分型式,以强烈亏损Nb、Ta、P等HFSE为特征。构造环境判别图解和Sr-Nd同位素比值显示塔里木盆地北缘新元古代早期的岩浆活动可能形成于陆缘弧的构造环境。Being covered by vast desert, the Neoproterozoic tectonic evolution of the Tarim Basin is not well-documented. In this study, zircon U-Pb geochronological and geochemical analyses were carried out on samples from the drilling cores, and the Early Neoproterozoic tectonic evolution of the north margin of the Tarim Basin is discussed on the basis of the results and previous works on the outcrops around the desert. LA-ICP-MS U-Pb dating of zircon grains from the gneiss in the metamorphic basement of the Tarim Basin yields a weighted average age of 822±7 Ma （MSWD=2.4）. In addition, two distinctive groups of zircon ages of ca. 2,5 Ga and 2.1-1.8 Ga were obtained from the Sinian sandstones using SHRIMP zircon U-Pb method. The petrographic and geochemical characteristics of the two-mica plagioclase gneiss demonstrated that it is metamorphosed granodiorite. Both the granodiorites and the mafic dyke collected from the adjacent drilling cores are of calc-alkaline and high-K calc-alkaline series. The rocks are characterized by right-dipping REE patterns and strong depletion of Nb, Ta, P and other HFSEs. The trace element and Sr-Nd isotope compositions of the igneous rocks suggest that setting of continental margin arc in the Neoproterozoic. the north margin of the Tarim Basin was under a tectonic

关 键 词：塔里木盆地 天山南 新元古代 变质基底 

分 类 号：P597[天文地球—地球化学] P595[天文地球—地质学]