南秦岭造山带韧性剪切系中—晚侏罗世运动学分析与力学机制探讨  

The Mid-Late Jurassic Kinematic Model and Mechanical Mechanism of the Ductile Shear Zones in the South Qinling Structural Belt

作　　者：陈鹏[1] 施炜[1] 

机构地区：[1]中国地质科学院地质力学研究所,北京100081

出　　处：《地球科学进展》2015年第1期69-77,共9页Advances in Earth Science

基　　金：国家自然科学基金面上项目"川东北双弧构造形成机理"(编号:41172184);中国地质调查局地质调查项目"中央造山带与南北构造带交汇区地壳深部地质调查"(编号:1212011220259)资助

摘　　要：南秦岭构造带为商丹缝合线以南的秦岭造山带部分。构造分析与同构造年代学研究证实该构造带内发育2条中—晚侏罗世区域性共轭韧性剪切带,即ENE向宁陕左旋韧性剪切带和NW向安康右旋韧性剪切带,其剪切变形年龄分别为169-162 Ma和178-163 Ma。通过对2条韧性剪切带的线理测量分析,反演其最大主压应力的方位约为NE向,与2条共轭韧性剪切带的钝角平分线一致,符合最大有效力矩准则。据此确定中一晚侏罗世秦岭造山带主要受控于NE-SW向区域性构造挤压作用,大致以秦岭造山带最狭窄部位（汉南一米仓山杂岩体）为界,其内部地块受ENE向与NW向共轭韧性剪切系控制,存在分别向西与向东的构造挤出活动。这一运动学模式可能代表了秦岭造山带中—晚侏罗世的主体变形方式。The South Qinling structural belt,as a part of the Qinling orogen,is bounded by the Shang-Dan suture to the north.Previous studies show the two regional conjugate ductile shear zones developed in the Mid-Late Jurassic epoch,e.g.,Ningshan ductile shear zone characteristic of ENE-striking,sinistral shearing,Ankang ductile shear zone typical of NW-direction,dextral shearing,whose shear deformation age respectively is 169-162 Ma and 178-163 Ma respectively.The lineations collected from the two ductile shear zones suggest the maximum principal stress（σ_1）is characterized by the direction of NE trending consistent with their obtuse angle bisector,which is corresponded with maximum effective moment criterion.Thus,our work suggests the blocks delimited by the conjugate ductile shear zones（e.g.,ENE-striking and NW-trending）in the interior of the Qinling orogen,dominated by NE-SW compression,pinned by the Hannan-Micangshan massif,laterally extruded in the Mid-Late Jurassic time,which is featured by westward escaping in western Qinling belt and eastward in the eastern Qinling belt.This kinematical model probably marks the dominated activity of the Qinling orogen in the Mid-Late Jurassic time.

关 键 词：南秦岭构造带 宁陕断裂带 安康断裂带 最大有效力矩准则 中—晚侏罗世 

分 类 号：P542[天文地球—构造地质学]