皖浙赣相邻区构造活动ESR测年、Ar-Ar测年及其构造年代学意义

ESR dating,Ar-Ar dating and its tectonic implications of tectonic activity in adjacent area of Anhui-Zhejiang-Jiangxi

皖浙赣相邻区大地构造位置位于江南造山带东段北缘,经历了加里东期、印支期及燕山期的多次构造运动,发育不同方向、不同时代的断裂带,其中燕山期构造运动较为活跃。基于ESR测年、Ar-Ar测年及地质构造调查和分析,重点论述了研究区燕山晚期的构造活动特征。测年结果显示:东源矿区辉绿岩脉Ar-Ar坪年龄为(113.5±1.1)Ma,断裂带内石英ESR年龄值分布在120~100 Ma之间,集中于(115±5)Ma;桐村剖面桐村岩体及围岩晚奥陶世长坞组中的裂隙石英脉ESR年龄值为120.2~100.4 Ma。研究认为,皖浙赣地区在燕山晚期(120~100 Ma)发生了一次强烈的构造热事件,在早白垩世中晚期发生了一次从挤压向伸展构造体制的反转。

The tectonic position of adjacent areas in Zhejiang-Jiangxi-Anhui is located in the northern margin of the eastern section of Jiangnan orogenic belt,which have experienced multi-period tectonic movements,including Caledonian Period,Indochinese Period and Yanshanian Period.Fault belts with various orientation and different geological ages were formed during the tectonic movements,and the tectonic movement during Yanshanian Period is the most active.Based on the ESR dating,Ar-Ar dating and geological field investigation,the authors focus on the tectonic activity characteristics in the Late Yanshania.The Ar-Ar dating in Dongyuan deposit area is(113.5±1.1)Ma,and ESR dating of quartz veins in the fault is distributed between 120 and 100 Ma,approximately(115±5)Ma.The ESR dating of quartz veins in the fault of Tongcun rock mass and surrounding rock of Shichangwu Formation in Late Ordovician is distributed between 120.2 and 100.4 Ma.Therefore,this research shows that a strong tectothermal event occurred in Late Yanshanian Period(120~100 Ma)and a tectonic reversal from extrusion to stretch occurred in late and middle Early Cretaceous.