东昆仑埃坑地区磷灰石裂变径迹年代学及构造意义

Apatite Fission Track Thermochronology and Tectonic Significance in Aikeng Area,East Kunlun Mountains

东昆仑位于青藏高原北部,埃坑地区处在东昆仑昆中和昆南断裂带之间。通过对该区域5个磷灰石样品分析,获得其裂变径迹年龄分别为(99±10)、(103±9)、(80±6)、(98±6)、(65±5)Ma。埃坑地区热历史可分为3个阶段:第1阶段(160~58Ma)持续隆升,对应羌塘地块与拉萨地块向欧亚板块的拼贴作用;第2阶段(58~35Ma)快速隆升,印度板块与欧亚板块碰撞导致埃坑强烈隆起;第3阶段(35Ma至今),构造活动较弱,未受青藏高原新近纪以来热事件影响。该地区5个样品的隆升量分别为3 374、3 283、3 230、3 157、3 278m,平均隆升量为3 264m,平均隆升速率为0.038mm/a。

East Kunlun Mountains is located in the northern margin of Tibetan Plateau,and Aikeng is situated between Mid-Kunlun fault zone and South-Kunlun fault zone.Using apatite fission track thermochronology,the datings of five samples were analyzed,and they are(99±10),(103±9),(80±6),(98±6)and(65±5)Ma respectively.There are three stages of thermal history.The first stage(160-58 Ma)fits in with that the Qiangtang block and the Lhasa block squeeze the Eurasian plate,and the second stage(58-35 Ma)corresponds to the collision between India plate and Eurasia plate.For the last stage(35 Ma to now),because of the stable tectonic activity,it is considered that it is not affected by the thermal events of the Tibetan Plateau since Neogene.In accordance with the results based on the three stages of thermal history,the formular calculations for the five samples have their rock uplifts of 3 374,3 283,3 230,3 157 and 3 278 m,the average rock uplift is 3 264 m,and the average uplifting rate is 0.038 mm/a.