摘要
晚中生代，中朝、扬子两地块的拼合带进一步受到强烈的陆内构造-岩浆活动改造，为揭示其规律性，以拼合带上北秦岭二郎坪群主体地块为研究对象，综合开展了中小构造解析、显微构造岩组学、电子探针、年代学等研究。研究发现，二郎坪群主体内部的小寨-二郎坪剪切带具右行韧性走滑特征，大庙-湾潭剪切带具右行韧性走滑兼后期脆-韧性逆掩叠加的特征；^40Ar／^39Ar构造-热年代学分析揭示出一期连续抬升-剥露过程，时间介于～121Ma和～100Ma之间。晚中生代二郎坪群地块经历了伸展-走滑-收缩背景依次控制下的构造改造过程，先是在区域伸展体制下，被内部的小寨-二郎坪剪切带、大庙-湾潭剪切带切割为抱树坪岩片、火神庙岩片、二进沟岩片等构造岩片；在其后的早白垩世早期区域走滑背景下，各构造岩片又发生了平移为主的右行走滑运动；最后，二郎坪岩体的侵入终止了内部小寨-二郎坪剪切带的活动，而大庙-湾潭剪切带也在区域收缩体制下终止活动，从而使二郎坪群重又焊接为一体。研究结果预示着北秦岭二郎坪群晚中生代同时期的构造体制可能与大别山是相反的。
The convergence belt between the Sino-Korea block and the Yangtze block was strongly deformed by intracontinental tectonomagmatic activity in the Late Mesozoic. In order to show details of the belt during the Late Mesozoic, we have carried out a series of analysis for small structure, micro-texture, right lateral slipping deformation a superimposion of ductile right electron-probe and geochronology. The the Erlangping Group on mesostudy has recognized a ductile for the Xiaozhai-Erlangping shear zone inside the Erlangping Group, and lateral slipping and late brittle-ductile thrusting for the Damiao-Wantan shear zone. ^40Ar/^39Ar tectonic-thermal chronological analysis reveals a continuous uplifting- denudating course between - 121 Ma and - 100 Ma. During the Late Mesozoic, the Erlangping Group experienced the tectonic reworkings respectively under the extensional, slipping and contractional tectonic regimes. Firstly, under the regionally extensional condition, the Erlangping Group was split by the Xiaozhai- Erlangping and Damiao-Wantan shear zones into three slabs, namely the Baoshuping, Huoshenmiao, and Erjingou slabs. Then in Early Cretaceous a right lateral movement of the slabs happened under a slipping regime. The intrusion of the Erlangping rock body ended the Xiaozhai-Erlangping shear zone, and the Damiao-Wantan shear zone was stopped under a contractional tectonic regime, which made the Erlangp Group welded into a single block again. Our results also indicated that the tectonic evolution of Erlangping Group of the North Qinling in the Late Mesozoic processed in an opposite way to that of ing the the Dabieshan tectonic belt.
出处
《地质力学学报》
CSCD
2009年第1期56-68,共13页
Journal of Geomechanics
基金
地质过程与矿产资源国家重点实验室基金项目(GPMR200634)
国家自然科学基金项目(40602026)
国家自然科学重点基金项目(90814006)
