秦岭勉略缝合带两期韧性剪切变形及其动力学意义

摘要

Detailed structural analyses indicate that the Mianxian -Lueyang suture zone has undergone two stages of ductile shear thrusting deformation. The early defor m ation existed mainly in ophiolitic and volcanic slices, showing the NW→SE she aring direction. The late deformation is characterized by the NNE→SSW shearing directi on at a high angle and makes up the imbricate thrust structure of the Mianxian -Lueyang sut ure zone. Metamorphism and deformation research reveals that the two stages of t he d uctile thrusting deformation are under high pressure and low temperature. In the lig ht of the deformation style, magmatism and metamorphism together with the evolut ion of the Mianxian-Lueyang suture zone, the following conclusions can be obtai ned, that is, the two stages of the ductile shear deformations represent subduction deformation and collision defo rmation, respe ctively. The dynamic analysis suggests that both the subduction and collision co urses have oblique features.%构造解析表明勉略蛇绿构造混杂岩带经历了两期韧性逆冲剪切变形，早期剪切变形主 要发育于蛇绿岩和火山岩岩片中，与区域变质作用同期，剪切运动方向NW→SE；晚期剪切变 形具有NNE→SSW高角度逆冲特点，并使不同岩片推覆叠置，构成缝合带现今主导叠瓦状构造 样式。变质变形作用研究显示，两期剪切变形都具有高压-低温性质;综合变形时代以及整 个缝合带构造演化,认为它们分别代表了俯冲与碰撞造山期变形，并指示洋壳俯冲和碰撞造 山作用均具有斜向特点。