东昆仑造山带北缘早志留世黑云母花岗岩成因  

Petrogenesis of Early Silurian biotite granite in northern margin of East Kunlun orogen

作　　者：白奋飞 张红兵 巨银娟[2,3] 赵俊英 周康 BAI Fenfei;ZHANG Hongbing;JU Yinjuan;ZHAO Junying;ZHOU Kang(Reseach Institute of Yanchang Petroleum(Group)Co.,Ltd.,Xi’an 710065,China;Department of Geology,Northwest University,Xi’an 710069,China;State Key Laboratory of Continental Dynamic,Xi’an 710069,China;Institute of Exploration and Development,SINOPEC Shanghai Offshore Oil&Gas Company,Shanghai 200120,China)

机构地区：[1]陕西延长石油(集团)有限责任公司研究院,陕西西安710065 [2]西北大学地质学系,陕西西安710069 [3]大陆动力学国家重点实验室,陕西西安710069 [4]中国石化上海海洋油气分公司勘探开发研究院,上海200120

出　　处：《西安科技大学学报》2023年第5期894-902,共9页Journal of Xi’an University of Science and Technology

基　　金：陕西省自然科学基金项目(2023-jc-yb-249);延长石油集团战略研究课题项目(ycsy2021zlyj-A-05)。

摘　　要：昆北地区早古生代花岗岩记录了东昆仑造山带古特提斯造山带的构造演化的重要信息。选择柴达木盆地西南缘昆北早古生代花岗岩进行了详细的年代学、地球化学和锆石Lu-Hf同位素研究。结果表明:花岗岩的LA-ICP-MS锆石U-Pb年龄为430±1.05 Ma,形成时代为早志留纪;岩石具有高硅(SiO_(2)=70.0~71.9 wt%)、高碱(Na_(2)O+K_(2)O=7.09~7.58 wt%)、A/CNK=1.03~1.11的特征,属于弱过铝质高钾钙碱性Ⅰ型花岗岩;岩石富集Rb、Th、Pb等大离子亲石元素,亏损镍、钛、磷等高场强元素,具有明显的铕负异常(Eu/Eu^(*)=0.49~0.52);岩石具有富集的锆石Lu-Hf同位素,其ε_(Hf)(t)=-11.47~-0.36,对应的二次模式年龄为2.1~3.1 Ga,表明其起源于中元古代成熟地壳的黑云母脱水部分熔融。综合区域地质背景以及岩石地球化学特征,认为黑云母花岗岩是由于昆北地体和柴南地体碰撞后阶段,地壳物质在伸展减薄背景下发生脱水部分熔融形成的。Early Paleozoic granites in the East Kunlun orogenic belt preserve important information about the tectonic and crustal evolution,which also retained the crustal magma response during the Caledonian orogeny in this area.A detailed examination has been made of zircon U-Pb age,Lu-Hf isotope and whole-rock geochemistry for the Early-Silurian biotite granites in Qaidam Basin.The results indicate that zircon U-Pb age is 430±1.05 Ma,an Early silurian period.The granites has high SiO_(2)(70.0~71.9 wt%),and alkaline(Na_(2)O+K_(2)O=7.09~7.58 wt%)contents,with A/CNK values of 1.03 to 1.11,which display high K peraluminous calcium-alkaline features.It is enriched in large ion lithophile elements such as Rb,Th,Pb,and depleted in high field strength elements such as Ni,Ti,P,with obvious negative Eu anomaly(Eu/Eu^(*)=0.49 to 0.52).In combination with its evolved zircon Lu-Hf isotopes,ε_(Hf)(t)ranges from-11.47 to-0.36,with corresponding two-stage model ages of_(2).1 to 3.1 Ga,indicating that it was derived from biotite dehydration melting of Mesoproterozoic crust.Considering the regional geology,it is proposed that the Early Silurian biotite granite was possible formed in the extension setting after the collision between the north Kunlun terrane and the Qaidam terrane,which led to the extension and thinning of the crust and the partial melting of the matured crust.

关 键 词：东昆仑造山带 柴达木西南缘 早志留世 HF同位素 

分 类 号：P588[天文地球—岩石学]