北祁连永登石灰沟奥陶纪硅质岩地球化学特征及大地构造意义  

Sedimentary Geochemistry of Cherts from the Middle—Upper Ordovician in Shihuigou Area, North Qilian Orogenic Belt and Its Tectonic Implications

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,武汉430074

出　　处：《地质论评》2006年第2期184-189,共6页Geological Review

基　　金：国家自然科学基金资助项目(编号40372061)的成果

摘　　要：北祁连造山带位于华北板块西南缘,是中—南祁连微板块与华北板块碰撞形成的加里东造山带。永登石灰沟位于北祁连东段,跨奥陶纪岛弧构造带。永登石灰沟一带奥陶系主要分布中堡群,其主要为中基性火山岩、火山碎屑岩夹硅质岩、大理岩、板岩及变质砂岩。硅质岩的沉积地球化学研究表明,与岛弧火山岩共生的硅质岩为生物成因,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, and is resulted from collision of two plates in Caledonian stage. Shihuigou in Yongdeng county locates in the eastern sector of Northern Qilian Mountains, crossing the island--arc zones of the Ordovician age. Zongpu Group is distributed over the Shihuigou area, and consists of medium--basic volcanic rocks, volcanic clastic rocks interbedded with cherts, limestone, slate and metamorphic sandstone. The geochemistry of the cherts reflects that the cherts coexisting with island-arc volcanic rocks all formed the background of continental margin basin. The rare earth elements reflect that these cherts formed in the deep-water basin far from continent where terrestrial material had no obvious effect to them. It is inferred that northern Qilian located in a tectonic background of archipelagic ocean where existed a wide ocean but multi--island in the Ordovician.

关 键 词：北祁连造山带 奥陶系 硅质岩 沉积地球化学 大地构造 

分 类 号：P534.42[天文地球—古生物学与地层学]