塔里木盆地东北部新元古代花岗质岩浆活动及地质意义  

Neo-proterozoic Granitoid Magmatism in the Kuqe Depression of Northeastern Tarim Basin and Its Significance

作　　者：罗金海[1] 车自成[1] 张小莉[1] 韩伟[1] 张国锋[1] 年秀清[1] 

机构地区：[1]大陆动力学国家重点实验室(西北大学)西北大学地质学系,西安710069

出　　处：《地质学报》2011年第4期467-474,共8页Acta Geologica Sinica

基　　金：国家自然科学基金项目(编号40972141)资助成果

摘　　要：库车坳陷东部侵入于元古宇基底变质岩中的黑云母二长花岗岩属于高钾钙碱性岩系,岩石具有富硅（SiO2=75.77%-77.79%）、高碱（Na2O＋K2O=6.90%-7.95%）、富钾（K2O/Na2O=1.21-1.98）、低TiO2（0.06%-0.13%,平均0.08%）和准铝质（铝饱和指数A/CNK=0.92-1.15,平均1.07）的特点。岩石明显富集Rb、Th、K、Nd、Hf、Zr、Tb、Y和Yb,亏损Ba、U、Nb、Ta、Sr、P、Sm、Ti等元素,具有明显的负Eu异常（δEu=0.06-0.11,平均0.10）。地球化学特征表明该花岗岩起源于中—下地壳的部分熔融。对花岗岩进行的LA-ICP-MS锆石U-Pb同位素地质年代学研究,获得了646.5±3.9 Ma的206Pb/238U加权平均年龄,说明花岗岩形成于早震旦世,而不是以前认为的石炭纪。结合区域地质资料分析认为,这次岩浆事件是塔里木地块基底在Rodinia超大陆裂解过程中的产物。Biotite adamellite intruding in the Proterozoic metamorphic basement of the eastern part of the Kuqe depression belongs to K-high calc-alkaline igneous rock.It is characterized by SiO2-rich,alkaline-rich,K-high,low-TiO2 and metaluminous rock with A/CNK=0.92~1.15.The adamellite is enriched in elements such as Rb,Th,K,Nd,Zr,Y and Tb,and depleted in elements such as Ba,U,Nb,Ta,Sr,P,Sm,and Ti,with distinct negative Eu anomaly（δEu=0.06~0.11）.Geochemical features of the granitoid rocks reveal its derivation from partial melting of middle-lower crust.Zircon U-Pb LA-ICP-MS dating on the magmatic genetic zircon yields an age of 646.5±3.9 Ma,representing the emplacement age of the granites.Combined with regional tectonic analysis,it is concluded that the Neo-proterozoic magmatism is resulted from the response of basement of Tarim craton to the Rodinia splitting.

关 键 词：塔里木盆地 库车坳陷东部 石炭纪 花岗岩 新元古代 Rodinia超大陆裂解作用 

分 类 号：P588.121[天文地球—岩石学]