地质学报2018，Vol.92Issue(1)：1-14,14.
印度-亚洲大陆碰撞初期的海沟沉积:藏东南宗卓组沉积岩石学与物源分析
Trench Deposition during the Initial Indian-Asian Collision: Petrologic and Provenance Analysis of the Zongzhuo Formation, Southeastern Tibet
摘要
Abstract
Mélange is mainly developed in convergent boundaries of oceanic subduction or continental collision.This study carried out detailed field investigations,petrologic study and detrital zircon geochronology for sandstones from the Zongzhuo Formation in the Nagarze area,southeastern Tibet.Field investigation shows that the contact relation of the Zongzhuo Formation to the underlying Tethys Himalayan strata is sedimentary at early stage and transfers to faulting contact due to late tectonic activities.Collapsed fragments of the Zongzhuo Formation are distributed along the direction of schist foliation,presenting features of mixing sedimentation.Most of the the Zongzhuo Formation is characteristic of multiple latestage tectonic overprinting.The Zongzhuo Formation mélange includes fragments and matrix,the former consisting of sandstones,chert,micrite,and the later consisting mainly of shale or mudstone.Fragments of the sandstones are composed mainly of igneous rocks and sedimentary rocks.U-Pb ages of detrital zircons cluster at 88～140 Ma,and εHf(t) of the Mesozoic-Cenozoic zircons varies greatly from-20 to 17.All these features suggest that the provenance derived from active Asian continental margin.Considering that the basement of the Zongzhuo Formation is the Tethys Himalayan strata in the northern margin of the Indian continent,the Zongzhuo Formation is inferred to be developed after the initial Indian-Asian collision.Due to the fact that the sandstone of the Zongzhuo Formation lacks young detrital U-Pb age of ＜90 Ma which is characterized by the Gangdese arc (＜60 Ma),we suggest that those sandstone blocks were probably recycled from the Xiukang mélange in the west,instead of the Xigaze foreare,Gangdese arc or the Lhasa terrane directly.The Zongzhuo Formation is one set of sedimentary mélange formed from lateral movement of the Xiukang mélange in the west at the deep marine environment during the early IndianAsian continent collision.Thus,the Zongzhuo Formation represents trench deposition at early stage of the Indian-Asian continent collision,whose distribution indicates the position of the suture zone of the early Indian-Asian continent collision.关键词
宗卓组/混杂岩/印度-亚洲大陆碰撞/藏南/浪卡子/物源分析Key words
Zongzhuo Formation/mélange/Indian-Asian collision/South Tibet/Nagarze/provenance analysis引用本文复制引用
周博,胡修棉,安慰,马安林,赖文..印度-亚洲大陆碰撞初期的海沟沉积:藏东南宗卓组沉积岩石学与物源分析[J].地质学报,2018,92(1):1-14,14.基金项目
本文为国家自然科学基金项目“藏南晚白垩世—古近纪宗卓混杂岩与印度亚洲大陆碰撞的关系”(编号41172092)、国家杰出青年基金项目(编号41525007)资助的成果. （编号41172092）
