内蒙兴安地区的板块构造问题

本文通过早二叠世岩相、生物群落、岩石化学、古地磁资料的综合研究分析,认为内蒙—兴安亚区的古地理,早二叠世早期,在乌兰浩特—林东—林西—线存在—火山弧。火山弧对沉积物和生物群落均有一定的控制作用,古地势为东低西高。早二叠世晚期,亚区东部迅速抬升,西部以海盆沉积为主,古地势为东高西低。同时根据海洋底栖、浮游生物的不同时混生现象,确定了板块分隔、对接、碰撞时期。

PLATE TECTONIC PROBLEMS OF THE INNER MONGOLIA XINGAN REGIONS

Through synthetically studying of lithofacies, fossil community, petrochemistry of volcanic rocks and paleomagaetism of early Permian, the writer has thought the Inner Mongolia Xingan subdomain to belong to active continental margin in early Permian, The contact between Tethys warm water type of living things and Arctic cold water type of ones was separated by existed deep sea.In early stage of early Permian, a volcanic are extended along Wulanhot-Lindong-Linxi areas. It controlled distribution of sediments and biocoenosis. In a-rc front area, Corals-Brachiopods-Bryozora community lived; Close to arc, Fusulinds-Brachiopods-Mollusca community; Volcanic arc, Brachiopods-community and in arc-rear area, Brachiopods-Mullusca community. Paleotopography subdomain dropped from west to east.Late stage of early Permian, east part of the subdomain speedly uplifted. The sediments are represented by marine with continental intercalations, while west part is marine basin exposition. East of the subdomain is higher than west in paleotopo-graphy. Moreover, based on the intermingling of planktons and benthoses in different time, three tectonic stages are determined as following; Hugeterian is separating stege of oceans Zhesian is junction stage of plate; Yihewusurian to early Triassic period is collision stage of plate.