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

摘要

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.%Fifty-eight samples from tectogenetic a 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 a 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.