大别山早白垩世变质核杂岩的结构与演化  

Structure and evolution of the Early Cretaceous Dabieshan metamorphic core complex

作　　者：冀文斌 林伟[1] 石永红[3] 王清晨[1] 褚杨[1,2] 

机构地区：[1]中国科学院地质与地球物理研究所岩石圈演化国家重点实验室,北京100029 [2]中国科学院研究生院,北京100049 [3]合肥工业大学资源与环境工程学院,合肥230009

出　　处：《地质科学》2011年第1期161-180,共20页Chinese Journal of Geology(Scientia Geologica Sinica)

基　　金：国家重点基础研究发展计划项目子课题"深俯冲洋壳与陆壳折返的流变学及构造背景"(编号:2009CB825008);"中国海相碳酸盐岩层系形成与后期演化"(编号:2005CB422101)资助

摘　　要：大别山中部混合岩—片麻岩穹隆的构造属性认识方面一直众说纷纭。通过对中大别杂岩及其边界剪切带或断裂带的构造解析,并结合对前人相关研究的总结,我们将中大别杂岩厘定为早白垩世的变质核杂岩,其中商麻断裂与晓天—磨子潭断裂和水吼—五河剪切带构成了一个完整的拆离断层带,并将变质核杂岩的形成时间限定在145～120 Ma。中大别杂岩与拆离断层具有统一的北西—南东向矿物拉伸线理和上部指向北西的剪切变形,推测在早白垩世早期大别山中下地壳岩石与其上部早期折返的高压—超高压板片之间存在一个解耦面。早白垩世混合岩化作用和岩浆作用为同期构造—热事件产物,造山带规模变质核杂岩的形成强烈地改造了大别山早中生代的构造格局。综合大别山及整个中国东部发育的早白垩世伸展构造,认为大别山变质核杂岩的形成与华北克拉通破坏具有相同的动力学背景,是在中国东部晚中生代岩石圈区域伸展作用下,由于造山带根部的垮塌与拆沉去根作用、中下部地壳物质发生部分熔融并向南东方向的塑性流动以及顶部上盘岩系的拆离与揭顶剥蚀作用,3个不同层次地质过程的综合效应。The nature of the extension dome in the Central Dabieshan Domain remains in debates for a long history. Based on the structural analysis of the core complex as well as its boundary shear zones or fracture zones and associated with a comprehensive review of the relative studies,we define this migmatite-gneiss dome as a metamorphic core complex（MCC） developed during 145 ~ 120 Ma. The Shangma fault,Xiaotian-Mozitan fault and Shuihou-Wuhe shear zone constitute the detachment faults of the Dabieshan MCC. The ductile deformation of the core complex and the detachment faults with the same kinematics of top-to-NW shearing indicates that they initiated as a uniform, flat-lying shear zone, possibly corresponding to the decoupled suface between the exhumated HP-UHP slabs and middle-lower crust. The Early Cretaceous migmatization and magmatism in Dabieshan was manifestations of the same tectonic-thermal event, the formation of the orogen-scale MCC intensively reconstructed the Early Mesozoic tectonic framework. Comparing with the extension tectonics in the east China, we propose that the occurrence of the Dabieshan MCC was the combined effects of three different geological processes in different levels ： the gravitational collapse and delamination of the orogenic root, the ductile flow of the middle-lower crust towards SE and the detachment and unroofing of the hanging wall, which shares the same tectonic settings as the destruction of the North China Craton under the Late Mesozoic regional extension in the east China.

关 键 词：大别山 变质核杂岩 伸展构造 超高压变质作用 华北克拉通破坏 

分 类 号：P588.34[天文地球—岩石学]