东秦岭—大别造山带南、北缘晚白垩世以来构造演化的石英ESR年代学研究

运用α石英热活化ESR定年法对东秦岭—大别造山带南、北缘58件样品进行了研究。结果显示,东秦岭—大别造山带南、北缘ESR年龄范围主要集中在晚白垩世以来(99.2～3.4 Ma)。结合区域地质事实分析,晚白垩世以来,东秦岭—大别造山带南缘的构造演化可划分为73.1～52.3 Ma伸展断陷期、39.1～27.2 Ma伸展-挤压的转换期和22.8～3.4 Ma挤压期;东秦岭—大别造山带北缘的构造演化可划分为89～70.1 Ma挤压隆升期、61.6～43.2 Ma伸展断陷期、37.2～22.6 Ma伸展-挤压的转换期和15.6～3.9 Ma挤压期。东秦岭—大别造山带南缘和北缘新生代构造演化特征基本相同,但是受多种因素控制,东秦岭—大别造山带南、北缘晚白垩世的构造演化存在较大差异。ESR测年结果与东秦岭—大别造山带南、北缘已有的地质事实相吻合,验证了ESR测年的可靠性。

Structural Evolution of Northern and Southern Edges of East Qinling-Dabie Orogenic Belt: Evidence from ESR Dating

Fifty-eight samples from tectogenetic α quartz veins in northern and southern edges of East Qinling-Dabie orogenic belt were studied by the use of ESR dating method.The results show that the ESR ages of α quartz veins mainly change between 99.2 and 3.4 Ma.Combined ESR dating results with other geological evidences,it comes to the conclusion as follows:after Late Cretaceous,the evolution history of southern edge of East Qinling-Dabie orogenic belt has experienced extending and faulted depression stage(73.1-52.3 Ma),extending-squeezing transformation stage(39.1-27.2 Ma) and squeezing stage(22.8-3.4 Ma);the evolution history of northern edge of East Qinling-Dabie orogenic belt has experienced squeezing uplift stage(89-70.1 Ma),extending and faulted depressions stage(61.6-43.2 Ma),extending-squeezing transformation stage(37.2-22.6 Ma) and squeezing stage(15.6-3.9 Ma).Northern and southern edges of East Qinling-Dabie orogenic belt have similar tectonic evolution characteristics in Cenozoic.But affected by several factors,the tectonic evolution of northern and southern edges of East Qinling-Dabie orogenic belt are obviously different in Late Cretaceous.The ESR dating results are consistent with geological evidences,which checks up the dependability of ESR dating.