地质学报2017，Vol.91Issue(4)：703-723,21.
祁漫塔格造山带——青藏高原北部地壳演化窥探
The Qiman Tagh Orogen as A Window to the Crustal Evolution of the Northern Tibetan Plateau
摘要
Abstract
The Qiman Tagh Orogenic Belt (QTOB),located along the northern part of the largest Qinghai-Tibet plateau,was constructed through protracted accretion and collision of a collage of terranes during subduction and closure of theQiman Tagh Ocean,a branch of Paleo-Tethys Ocean from the Neoproterozoic to Early Mesozoic.The orogen is located between the Qaidam Basin and Kumukuri Basin,and cut by the Altun Fault to the west.The Early Neoproterozoic (ca.1000～820 Ma) ages from this orogen suggest link with the formation of Rodinia supercontinent.The QTOB is tectonically divided into the North Qiman Tagh Terrane (NQT) and the South Qiman Tagh Terrane (SQT).The NQT developed as an active continental margin,and preserves abundant Early Paleozoic granitoids which possibly formed through the melting of old basement,and a series of mafic-ultramafic rocks considered as VA type ophiolites.In contrast,the SQT witnessed intra-oceanic subduction,where SSZ type ophiolites are documented together with island arc tholeiite (IAT) to the youngest calc-alkaline lavas,in a primary oceanic island arc environment during the Early Paleozoic.With continued subduction,the young island arc was transformed into a mature island arc with thickened crust.This region preserves typical evidence for sedimentation and volcanism in the initial stages of volcanic arc development.The collision between the SQT and NQT occurred probably in the Late Silurian (ca.422 Ma) and continued until ca.398 Ma,as evidenced from the abundant within-plate granites developed in the NQT after 398 Ma.In the SQT,voluminous oceanic island arc granitoids formed during the Early-Middle Devonian (ca.418～389 Ma),with contrasting geochemical features as to those in the NQT.The SQT as an exotic terrane that has been incorporated into the continental margin contributed significantly to the continental growth in this orogenic belt.A trench jam might explain the large gap (ca.357 ～ 251 Ma) of granitoid magmatism.The final closure of thePaleo Tethyan Qiman Tagh Ocean might have occurred in the Late Permian,and resulted in the accretion of the Kumukuri microcontinent.A series of Y-depleted granitoids formed during Early-Middle Triassic (before 237 Ma),which might be associated to the partial melting of thickened lower crust induced by the oceanic lithosphere delamination.Subsequently,a series of calc-alkaline and alkaline granitoids yielded by the old crust melting were emplaced in the SQT,and their formation is linked to the transition from post-collision to within-plate settings.关键词
祁漫塔格/构造—岩浆演化/古特提斯洋/蛇绿岩/弧—陆碰撞Key words
Qiman Tage/tectonic-magmatic evolution/Paleo Tethys Ocean/ophiolite/arc-continental collision引用本文复制引用
于淼,周建厚,钟世华,丰成友,何书跃,赵梦琪,赵一鸣,李大新,瞿泓滢,刘建楠,王辉..祁漫塔格造山带——青藏高原北部地壳演化窥探[J].地质学报,2017,91(4):703-723,21.基金项目
本文为国土资源部公益性行业科研专项经费项目(编号:201411025)、中国地质调查局地质调查项目(编号:1212011085528)、中国地质调查局高层次地质人才培养计划(编号:201309)和青年地质英才计划(编号:201112)资助的成果. （编号:201411025）
