华北北部二叠纪陆壳演化  

The evolution of Permian continental crust in northern part of North China

作　　者：邵济安[1] 何国琦[1] 唐克东[2] 

机构地区：[1]造山带与地壳演化教育部重点实验室,北京大学地球与空间科学学院,北京100871 [2]沈阳地质矿产研究所,沈阳110034

出　　处：《岩石学报》2015年第1期47-55,共9页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(41172196)资助

摘　　要：目前围绕华北北部(包括华北克拉通北缘和北邻的兴蒙造山带)的二叠纪的构造背景存在着不同的认识。其中一种影响较大的观点是古亚洲洋的演化持续到二叠纪末-三叠纪初,由于大洋板块向华北克拉通之下的俯冲,导致克拉通北缘成为"安第斯型"大陆边缘。活动陆缘有从早期(C2)的板块俯冲-汇聚向晚期(P2-T1-2)板块拆离-陆缘伸展演变的趋势,论证多偏于岩浆作用。本文将从沉积建造、变形、变质、岩浆活动以及区域构造背景等角度对此观点进行讨论,本文将研究区晚古生代陆壳演化划分为三个阶段:(1)法门阶之前的中泥盆世是兴蒙造山带的主造山阶段;(2)晚泥盆-早石炭世进入后碰撞阶段;(3)晚石炭世-早二叠世兴蒙造山带的年轻陆壳在伸展背景下,上叠的新生性裂陷槽构造而非大洋板块控制了同期的沉积作用和岩浆活动。这三阶段的地质事件在华北克拉通北缘都有相应的表现。研究区深成岩同位素年龄显示了中-晚泥盆世、早二叠世和晚二叠世三个峰值。为了揭示岩浆的形成机制,本文重点对研究区早二叠世(280Ma)和晚二叠世(260Ma)深成岩的岩石组合和Sr-Nd同位素特征进行对比研究。R1-R2图显示本区二叠纪深成岩组合与以英云闪长岩和花岗闪长岩为主的安第斯型造山带不同。早二叠世深成岩具双峰特征,Sr-Nd同位素显示早二叠世深成岩与EMI地幔源区有更密切联系。受到前人对高寺台原始岩浆研究的启发,进一步认识到华北克拉通北缘在早二叠世时存在板内OIB岩浆沿着岩石圈断裂的上涌的过程。相比之下,晚二叠世深成岩多为正长花岗岩和二长花岗岩,岩石碱性程度提高,中酸性岩石具高碱、高钾的特征。Sr-Nd同位素显示岩浆源区有向EMII演变的趋势,中-上部地壳熔融物质增多,暗示热活动带的上升。总之,从岩浆形成机制、岩浆源区演变的趋势和岩浆时空演化�At present there exist different understandings about the structural settings of northern part of North China （ including the northern margin of North China Craton and Hinggan-Mongolia Orogenic Belt） in the Permian. According to an influential viewpoint, evolution of the Paleo-Asian Ocean has continued until the end of Permian or the beginning of Triassic, with the northern margin of North China Craton becoming an ＂Andes-type continental margin＂ as a result of oceanic plate subducting toward underneath the North China Craton. And the active continental margin has correspondingly changed from an early state of subdaction-convergence （ C2 ） to a late state of detachment of subducting plate and extention of continental margin （P2-T1.2）- Such an understanding is largely based on evidences of magmatism. This viewpoint will be discussed in this paper in terms of sedimentary formation, deformation, metamorphism and regional tectonic settings with respect to the continental crust evolution of the concerned area in the Late Paleozoic, and the whole process of evolution will be divided into three stages according to our understanding： （ 1 ） the climactic orogeny of Hingga-Mongolia Orogenic Belt in the Middle Devonian before Famennian; （2） the post-collision in the Late Devonian-Early Carboniferous; and （3） the non-orogenic extension in the Late Carboniferous-Early Permian, when the young continental crust of Hingga-Mongolia Orogenic Belt under the extensional settings produces newly-born rifts, which-instead of any oceanic plate-controls the concurrent sedimentation and magmatism. All the geological events of the three stages have their expressions in the northern margin of North China Craton. The isotopic ages of plutonic rocks from the area show three peak values： Middle-Late Devonian, Early Permian, and Late Permian. The rock assemblages and Sr-Nd isotopic characteristics of plutonic rocks of Early Permian （280Ma） and Late Permian （260Ma） are particularly studied to reveal magma g

关 键 词：华北克拉通北缘 陆壳演化 安第斯型造山带 二叠纪深成岩 克拉通化 

分 类 号：P534.46[天文地球—古生物学与地层学] P541[天文地球—地质学]