华南早中生代从印支期碰撞构造体系向燕山期俯冲构造体系转换的形变记录  

Deformation record of the change from Indosinian collision-related tectonic system to Yanshanian subduction-related tectonic system in South China during the Early Mesozoic

作　　者：张岳桥[1] 徐先兵[2] 贾东[2] 舒良树[2] 

机构地区：[1]中国地质科学院地质力学研究所,北京100081 [2]南京大学地球科学系,江苏南京210093

出　　处：《地学前缘》2009年第1期234-247,共14页Earth Science Frontiers

基　　金：国家自然科学基金项目(40634022)

摘　　要：华南地区中生代动力体制经历了从特提斯构造域向滨太平洋构造域的转换,但对这种动力体制转换发生的时间和产生的地质效应则存在不同的认识。通过分析华南印支—早燕山构造层(D—J1-2)广泛发育的褶皱构造,识别了早中生代两个世代褶皱构造的横跨叠加型式,发现早期近东西向褶皱构造具有南北成带、晚期NNE向褶皱构造具有东西分区的区域展布特征。基于地层接触关系和早中生代岩浆岩和火山岩同位素年代学数据统计分析,认为这两组叠加褶皱构造清楚地记录了华南早中生代两期挤压事件,近东西向褶皱是对印支早期华南地块南北边缘碰撞造山事件的远程响应,NNE向褶皱则起源于燕山早期((170±5)Ma)古太平洋板块向华南大陆之下低角度俯冲作用,两者发生转换的时代在中晚侏罗世之交。伴随这两期构造挤压而产生的地壳增厚分别诱发了华夏地块三叠纪和晚侏罗世地壳深熔作用和岩浆侵入活动。华南两组叠加褶皱构造的识别为进一步探讨早中生代从碰撞动力构造体系向俯冲动力构造体系转换提供了关键的构造地质学依据。It is commonly accepted that tectonic regimes underwent a tremendous change, during the Mesozoic, from the Tethys tectonic domain to the Pacific tectonic domain in South China, although the timing and geological effects of such a change have been debated. This paper identified two generations of superimposed folds that widely develop in Indosinian to early Yanshanian tectonic layer （D-J1-2 ） in South China, and it is found that the earlier generation of folds is well zonated in W-E and the later one is distributed in NNE. Based on the analysis of stratigraphic contact relationship and isotopic dating results of Early Mesozoic igneous rocks, it is considered that these two fold generations clearly record two phases of Early Mesozoic tectonic compression in South China： the nearly W-E trending fold zones resulted from far-field effect of Indosinian collision or accretion occurred along the northern and southern margins of the South China Block, while the NNE-trending folds were originated from low angle subduction of the paleo-Pacific plate under the South China Block, which occurred in the time of Middle to Late Jurassic around （170±5） Ma. Crustal thickening caused by these two compressions induced melting and emplacement of Triassic and Late Jurassic granites particularly developed in the Cathaysian Block. The recognition of the two superimposed fold generations in South China is key to understanding the change from the Triassic continent-continent collision-related tectonic system to the Middle Late Jurassic subduction-related tectonic system.

关 键 词：华南地块 叠加褶皱 印支期碰撞褶皱体系 早燕山期俯冲褶皱系统 构造动力体制转换 

分 类 号：P552[天文地球—构造地质学]