柴达木盆地北缘新元古代-早古生代大洋的形成、发展和消亡  

The Initiation,Development and Termination of the Neoproterozoic-Early Paleozoic Ocean in the Northern Margin of Qaidam Basin

作　　者：朱小辉[1,2] 陈丹玲[2] 王超[1] 王红[3] 刘良[2] 

机构地区：[1]国土资源部岩浆作用成矿与找矿重点实验室中国地质调查局西安地质调查中心,西安710054 [2]西北大学大陆动力学国家重点实验室西北大学地质学系,西安710069 [3]河北省地矿局第十一地质大队,河北邢台054000

出　　处：《地质学报》2015年第2期234-251,共18页Acta Geologica Sinica

基　　金：国家基础研究规划项目“973”项目(2009CB825003);国家自然科学基金项目(41402051、41472053);中国地质调查局工作项目(12120113013400)联合资助的成果

摘　　要：柴达木盆地北缘构造带是一条典型的早古生代造山带,是由陆壳深俯冲形成的高压/超高压变质带,产于其中的高压/超高压变质岩石原岩形成时代普遍大于750Ma,原岩的性质为陆壳属性,但柴北缘东段都兰沙柳河地区出露的含柯石英榴辉岩原岩的形成时代为516Ma,原岩的性质为洋壳属性,证实柴北缘局部地段还存在洋壳深俯冲,柴北缘地区可能记录了从大洋俯冲到大陆俯冲再到碰撞造山这一完整的演化历史。本文主要从岩石学、年代学、地球化学以及同位素地球化学等方面对柴北缘地区陆壳深俯冲前新元古代-早古生代大洋发展与演化的岩石记录进行了系统总结,认为柴北缘地区在700~850Ma时受Rodinia超大陆裂解事件的影响发生了裂解;535~700Ma时在裂解事件的基础上形成了一个新元古代-早古生代的大洋,沿柴北缘连续分布的岩石记录表明该洋盆可能在早古生代已具有一定的规模;460~535Ma时该洋壳发生了俯冲消减作用;450~460Ma期间洋盆闭合消失。这一认识对全面深入了解柴北缘高压/超高压变质带早古生代构造演化历史具有重要意义。The North Qaidam was an Early Paleozoic orogenic belt which was formed from deep subduction of continental crust.The U-Pb zircon ages reveal that most of the protolith ages of HPM/UHPM rocks in the North Qaidam are older than 750 Ma,and the protolith belong to continental crust type.But the protolith age of coesite-bearing eclogite from Shaliuhe section in Dulan area is 516 Ma,and the protolith belong to oceanic crust type,suggesting the existence of deep subduction of oceanic crust prior to the continental subduction in the North Qaidam.This paper focuses on the progress of petrology,geochronology,geochemistry and isotope geochemistry studies of the evolution about the Neoproterozoic-Early Paleozoic ocean in the North Qaidam,suggesting a continental breakup event occurred during 700~850Ma in this area,which could be related with the breakup of Rodinia,then a Neoproterozoic-Early Paleozoic ocean appears to have developed between Qaidam and Olongbuluck blocks during 535~700Ma on this basis,which was then subducted during 460~535Ma,and disappeared during 450~460Ma at last.It is of great importance to know the evolution of the HP/UHP belt in the North Qaidam.

关 键 词：新元古代-早古生代 大洋 洋壳俯冲 大陆俯冲碰撞 高压/超高压变质带 柴北缘 

分 类 号：P534[天文地球—古生物学与地层学]