摘要
造山带地壳结构和成分的基本特征对于认识大陆地壳成分演化和区域成矿背景具有重要意义.综合青藏高原拉萨地体东南部地球物理、高温高压岩石物性和岩浆岩地球化学资料,分析该地区地壳整体成分特征,并探讨其可能成因.该地区平均地壳波速显著低于全球大陆和造山带地壳的平均值,表明地壳整体具有中酸性成分,下地壳特征也可由中性岩石(残余体性质的中性含石榴石麻粒岩)解释.拉萨地体东南部整体地壳成分特征应与多阶段长英质化有关,包括碰撞前大陆弧演化阶段(以堆晶或残余体下地壳拆沉为主)和碰撞后高原垮塌阶段(以加厚下地壳拆沉为主,伴随印度古老长英质陆壳物质的俯冲回返/构造底侵).拉萨地体是研究大陆地壳成分演化的绝佳区域,亟待进一步开展多学科综合研究.
The structure and composition of orogenic belts are important for understanding the chemical evolution of the continental crust and the background for metallogenesis. This study integrates previously published crustal seismic structures,experimentally determined petrophysical properties of various rock types, and geochemical data of magmatic rocks from the southeastern Lhasa Terrane, in order to discuss the compositional features of the continental crust in this region and their possible causes. The average crustal seismic velocity in this region is lower than the average values of global continental crust and orogenic belts, suggesting a more felsic composition for the bulk continental crust. Moreover, the lower crust could also be composed of intermediate rocks (restitic intermediate garnet granulite). The felsic bulk crustal composition of the southeastern Lhasa terrane is supposed to be related to multiple episodes of felsification, including the pre-collisional continental arc evolution stage (mainly by delamination of cumulate or restitic lower crust) and the post- collisional plateau collapsing stage (mainly by delamination of thickened lower crust, which is accompanied by the relamination/tectonic underthrusting of felsic materials from the ancient Indian continental crust). The Lhasa terrane is one of the best places to study the chemical differentiation of continental crust, which demands further comprehensive studies of multiple disciplines.
作者
郭京梁
张宏飞
徐旺春
郭亮
吴耀
崔丹丹
Guo Jingliang;Zhang Hongfei;Xu Wangchun;Guo Liang;Wu Yao;Cui Dandan(School of Earth Sciences,China University of Geosciences,Wuhan 430074,China;State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences,Wuhan 430074,China)
出处
《地球科学》
EI
CAS
CSCD
北大核心
2019年第6期1809-1821,共13页
Earth Science
基金
国家重点研发计划(No.2016YFC0600309)
国家自然科学基金项目(Nos.41730211,41502049)
中国地质大学中央高校基本科研业务费(No.CUGL180413)
关键词
大陆地壳
成分演化
拆沉
Nd
同位素
冈底斯
青藏高原
岩石学
continental crust
chemical differentiation
foundering
Nd isotopes
Gangdese
Tibetan Plateau
petrology
