秦岭岩群古生代构造变形分析

Analysis of Paleozoic structural deformation of the Qingling Group

秦岭岩群是秦岭造山带中最古老的地体之一,其强烈的构造变形记录了秦岭造山带的形成和演化信息。本文在野外构造调查的基础上、结合显微构造变形分析和锆石U‑Pb定年,对秦岭岩群进行了构造变形解析及年代学研究,结果显示秦岭岩群古生代构造变形表现为由东向西的斜向挤出抬升,其构造变形时间为426.7±5.8 Ma~395.7±7.4 Ma。该期构造变形温度为480℃~560℃,对应变质相为高绿片岩相—低角闪岩相,差异应力为20.19~56.54 MPa,应变速率为1.82281×10^(-13)s^(-1)~5.62102×10^(-13)s^(-1),付林参数为0.29~0.47,涡度值为0.57~0.75。综合前人研究及本次构造变形分析,认为秦岭岩群在扬子板块与华北板块斜向汇聚背景下经历了由东向西的斜向挤出抬升。

The Qinling Group is one of the oldest terrains in the Qinling orogenic belt.Its strong structural deformation recorded the tectonic evolution information of the Qinling orogenic belt.Based on the field structural investigation,combined with microstructural deformation analysis and zircon U‑Pb dating,were conducted to study the structural deformation and chronology of the Qinling Group.The results shows that the structural deformation of the Qinling Group is characterized by the obliquely upward extrusion from east to west between 426.7±5.8 Ma~395.7±7.4 Ma.The ductile deformation temperature of mylonite is 480℃~560℃,which reached to high greenschist to low amphibolite metamorphic facies,the differential stress is 20.19~56.54 MPa,the strain rate is 1.82281×10^(‑13)s^(‑1)~5.62102×10^(‑13)s^(‑1),the Flinn parameter is 0.29~0.47,and the vorticity value is 0.57~0.75.On the basis of previous studies and this structural analysis,it is concluded that the Qinling Group has undergone an upward extrusion from east to west in the process of oblique convergence between the Yangtze and North China Plate.