大陆地壳活动带片麻岩穹隆构造与分层流变  

Gneiss domes and stratified middle to lower crustal flow in continental mobile belt

作　　者：刘俊来[1] 陈小宇[1] 张健 周保军 樊文魁 闫佳鑫 LIU Junlai;CHEN Xiaoyu;ZHANG Jian;ZHOU Baojun;FAN Wenkui;YAN Jiaxin(State Key Laboratory of Geological Processes and Mineral Resources,China Universityof Geosciences(Beijing),Beijing 100083,China)

机构地区：[1]中国地质大学(北京)地质过程与矿产资源国家重点实验室,北京100083

出　　处：《地质学报》2022年第9期3158-3181,共24页Acta Geologica Sinica

基　　金：国家自然科学基金项目(编号42172246,41902203,41430211);高校基本科研业务费(编号2652018114)联合资助的成果。

摘　　要：大陆克拉通化与造山带形成后的活化与再造机理和条件,是板块构造理论登陆面对的重要课题,针对广泛发育于陆缘、陆内环境中的大陆地壳活动带开展的深入研究为此提供了重要约束。以中下地壳深变质岩为核,中浅变质岩为幔部的穹隆构造是大陆地壳活动带最为典型特征构造样式之一。本文基于对古元古代—新生代不同时期典型大陆地壳活动带内片麻岩穹隆构造的分析,总结出以下共性特点:(1)发育厚皮构造,强烈的热异常与高应变使得活动带中保存着下地壳基底岩石卷入地壳变形过程的痕迹;(2)核部往往由高级变质岩石(通常伴有花岗岩或混合岩)组成,变质程度主体为低角闪岩相到高角闪岩相,局部可以达到麻粒岩相,从核部向幔部变质程度逐渐降低;(3)分层(或层状)流变是地壳活动带变形的重要表现形式;(4)中、深层次的岩石共同遭受了强烈剪切变形作用的改造,不同构造层次(核部与幔部)岩石中的构造具有几何学、运动学和动力学上的一致性,拉伸线理和不同尺度的a型褶皱广泛发育,伴随着区域尺度的a型或b型穹隆构造;(5)幔部岩系与核部岩系具有特征的运动学上的耦合关系而流变学上的解耦,二者之间及内部常发育不同尺度的剪切不连续面(Tectonic discontinuity contact,TDC)。基于上述特点分析,本文提出切向(近水平)剪切流动与多流变层分层流动是大陆地壳活动带中、下地壳流动一致性的体现。多种变形体制叠加,包括近水平切向流动作用的主要贡献并辅以垂向运动的叠加或递进变形,造就了现今大陆地壳活动带中广泛发育的片麻岩穹隆构造,它们递进演化成为线性a型穹隆群、b型穹隆或演变为变质核杂岩构造。The mechanisms of the continental activation and regeneration after cratonization and orogeny are important subjects for studies of plate tectonics in continental interiors. Such studies provide important constraints on our understanding the continental crustal active belts that are widely developed in continental margins and intracontinental environment. Dome structures with middle and lower crustal high-grade metamorphic rocks in the cores and middle crustal low-grade metamorphic rocks in the mantle are among the most typical characteristics of continent crustal mobile belts. Based on structural analysis and synthesis of dome structures from Paleoproterozoic-Cenozoic typical continental crustal mobile belts, it is shown that they have many common characteristics:(1) Development of thick-skinned structure. Evidence of involvement of lower crustal rocks in the deformation due to strong thermal anomalies and high strains is well preserved.(2) The cores of the domes are usually composed of high-grade metamorphic rocks(generally with emplacement of granites or formation of migmatites). Metamorphism grades vary from lower amphibolite facies to upper amphibolite facies, or locally granulite facies in the cores to greenschist facies or lower greenschist facies in the mantles.(3) Stratified flow is an important form of deformation in active crustal zones.(4) The rocks at different structural(crustal) levels and stratigraphic horizons were subjected to strong shearing. Deformation structures in rocks from the cores and mantles at different levels are consistent in geometry, kinematics and dynamics. Stretching lineations and a-type folds are widely developed. Regionally, a-type or b-type domes are formed.(5) The mantles and cores are kinematically coupled and rheologically decoupled, which results in the occurrence of shear discontinuities(or tectonic discontinuity contact-TDC) of different scales between the two units and within them. From the above characteristics, it is proposed that subhorizontal(tangential) shearing

关 键 词：大陆地壳活动带 片麻岩穹隆构造 近水平切向剪切变形 中下地壳分层流动 剪切不连续 

分 类 号：P542[天文地球—构造地质学] P588.345[天文地球—地质学]