从弧后盆地到前陆盆地——北祁连造山带奥陶纪—泥盆纪的沉积盆地与构造演化  

From the back-arc basin to foreland basin-Ordovician-Devonian sedimentary basin and tectonic evolution in the North Qilian orogenic belt

作　　者：杜远生[1] 朱杰[1] 韩欣[1] 顾松竹[1] 

机构地区：[1]中国地质大学,湖北武汉430074

出　　处：《地质通报》2004年第9期911-917,共7页Geological Bulletin of China

基　　金：国家自然科学基金(No.40372061)资助。

摘　　要：北祁连加里东期造山带是在新元古代Rodinia联合大陆(Pangea-850)基础上裂解,经由寒武纪裂谷盆地、奥陶纪初期成熟洋盆、奥陶纪中晚期北祁连活动大陆边缘、志留纪—早、中泥盆世碰撞造山而形成的。奥陶纪中、晚期,北祁连、走廊地区中、上奥陶统发育洋壳-岛弧-弧后火山岩,形成典型的沟-弧-盆体系的沉积。志留纪—早、中泥盆世是北祁连-走廊沉积盆地的转换时期。除天祝、古浪、景泰及肃南等局部地区发育下志留统钙碱性系列火山岩以外,全区志留系均以碎屑岩沉积为主。志留系底部多见一套砾岩层。下—中志留统为典型复理石相的浊流沉积。上志留统变为滨浅海相磨拉石沉积。早、中泥盆世雪山群为典型的陆相粗碎屑磨拉石沉积。从空间分布上看,志留系—泥盆系在走廊—北祁连地区也有自北向南厚度加大、粒度变粗的特征,古流以由南向北、来自造山带的古流为特征。北祁连-河西走廊奥陶纪弧后盆地火山岩—志留系复理石-海相磨拉石—中、下泥盆统陆相磨拉石的充填序列以及空间分布特点,反映为典型的弧后盆地向前陆盆地转化的沉积序列。The late Caledonian to early Hercynian North Qilian orogenic belt in northwestern China formed on the basis of breakup of late Proterozoic Rodinia (Pangea-850), and its evolution progressed through a rift basin in the Cambrian, a mature ocean basin in the initial Ordovician, the active continental margin of the North Qilian in the Mid-Late Ordovician and collisional orogeny in the Silurian to Early-Mid Devonian. The Mid-Late Ordovician witnessed development of oceanic crustal, island-arc and back-arc volcanic rocks in the Mid-Upper Ordovician in the North Qilian and Hexi Corridor, which formed deposits of a typical trench-arc-basin system. The Silurian to Early-Mid Devonian was a transition period of the North Qilian-Corridor sedimentary basin. Except in Tianzhu, Gulang, Jingtai and Sunan where volcanic rocks of the Lower Silurian calc-alkaline series are developed, the Silurian of the whole area is dominated by clastic deposits. The base of the Silurian consists mostly of a conglomerate bed and the Lower-Mid Silurian is typical turbidity deposits of flysch facies, while the upper Silurian becomes littoral-neritic molasse deposits. The Early-Mid Devonian Xueshan Group is typical terrestrial coarse clastic molasse deposits. In terms of spatial distribution, the Silurian-Devonian in the Corridor-North Qilian area also has the features of southward thickening and coarsening in grain size. The paleo-currents are characterized by those from the orogenic belt form south to north. The filling sequence and spatial distribution of the Ordovician back-arc basin volcanic rocks-Silurian flysch-marine molasse-Mid-Lower Devonian continental molasse in the North Qilian-Hexi Corridor reflect a typical sedimentary sequence of transition from the back-arc basin to foreland basin.

关 键 词：北祁连造山带 奥陶纪 泥盆纪 弧后盆地 前陆盆地 

分 类 号：P534.4[天文地球—古生物学与地层学] P512.2[天文地球—地质学]