江南隆起带北缘新生代构造演化的石英ESR年代学研究

运用α石英热活化ESR定年法对江南隆起带北缘35件样品进行了研究。结果显示,江南隆起带北缘的石英脉ESR年龄范围在195.8~3.4 Ma之间,主要集中在喜山期(75~3.4 Ma)。结合其他地质证据,江南隆起带北缘新生代构造演化可以划分为伸展断陷期(75~61.5 Ma)和挤压隆升期(43.2~3.4 Ma)两个阶段。前者以发育正断层和断陷盆地为特征,后者以重力滑脱构造为特征。喜山期的构造作用对先存构造进行了强烈的改造,包括南华北、中下扬子和江南隆起带北缘的整个中国东部地区在喜山期都经历了显著的构造活动。ESR测年结果与江南隆起带已有地质事实相吻合,检验了ESR测年的可靠性。

Structural Evolution of Northern Jiangnan Uplift: Evidence from ESR Dating

Thirty-five samples from tectogenetic α quartz veins in northern Jiangnan uplift have been studied by using ESR dating method.The results show that the ESR ages of α quartz veins from northern Jiangnan uplift change between 195.8 Ma and 3.4 Ma,mainly from 75 Ma to 3.4 Ma(Himalayan).Combined ESR dating results with other geological evidence,the evolution history of northern Jiangnan uplift in the Cenozoic can be classified into two phases.The former is extend and faulted depressions stage(75-61.5 Ma).Normal faults and fault basins formed during this time.The latter is squeezing uplift stage(43.2-3.4 Ma).Its main feature is gravitational detachment structure.The Indosinian and Yanshanian structures had been intensely reconstructed during Himalayan.Entire eastern China experienced distinct tectonic movement,including southern North China,mid-lower Yangtze and northern Jiangnan uplift.The ESR dating results are consistent with geological evidence,which checked up the dependability of ESR dating.