北祁连肃南一带奥陶纪硅质岩沉积地球化学特征及其多岛洋构造意义  

Sedimentary Geochemistry and Tectonic Significance of Ordovician Cherts in Sunan, North Qilian Mountains

作　　者：杜远生[1] 朱杰[1] 顾松竹[1] 

机构地区：[1]中国地质大学地球科学学院,湖北武汉430074

出　　处：《地球科学（中国地质大学学报）》2006年第1期101-109,共9页Earth Science-Journal of China University of Geosciences

基　　金：国家自然科学基金项目(No.40372061)

摘　　要：北祁连造山带位于华北板块西南缘,是柴达木微板块与华北板块碰撞形成的加里东造山带．北祁连肃南百泉门—边马沟位于北祁连西段,跨奥陶纪弧后盆地、岛弧、海沟俯冲杂岩等构造带和百泉门—九个泉、大岔大坂、边马沟3个蛇绿岩带．北祁连肃南一带奥陶系主要分布阴沟组地层,主要为中基性火山岩、火山碎屑岩夹硅质岩、大理岩、变质泥岩(板岩或片岩) 及砂岩．硅质岩的沉积地球化学研究表明,边马沟与大洋俯冲蛇绿杂岩共生的硅质岩、大岔大坂与岛弧蛇绿岩共生的硅质岩及九个泉、百泉门与弧后蛇绿岩共生的硅质岩均形成于大陆边缘盆地的构造背景,但硅质岩稀土元素特征反映其受陆源影响不明显,为远离陆源的深水盆地沉积．推测北祁连奥陶纪处于多岛洋的构造背景,北祁连奥陶纪存在宽阔、多岛的古洋盆．The North Qilian orogenic belt in northwestern China is an elongate tectonic unit situated between the North China plate in the north and the Qaidam plate in the south. It is a result of the collision of two plates during the Caledonian stage. The Sunan area, from Baiquanmen to Bianmagou, is located in the western sector of the North Qilian mountains, crossing three tectonic units （back-arc basin, island-arc and trench subduction complex） and three ophiolite zones （Baiquanmen-Jiugequan, Dachadaban and Bianmagou）. The Yingou Formation is distributed over the Sunan area, and consists of mediumbasic volcanic rocks, volcanic clastic rocks interspersed with cherts, marbles, metamorphic mudstone （slate or schist） and sandstone. The geochemistry of the cherts shows that the cherts, coexisting with ophiolite from Bianmagou, Dachadaban, Jiugequan and Baiquanmen, all formed the background of the continental margin basin. The rare earth elements show that these cherts formed in the deep-water basin far from the continent, where terrestrial material had no obvious effect on them. It is inferred that North Qilian orogenic belt was located in the tectonic background of an archipelagic ocean where a wide multi-island ocean existed in the Ordovician.

关 键 词：北祁连造山带 硅质岩 地球化学 大地构造 

分 类 号：P594[天文地球—地球化学]