新疆且末阿尔金断裂南缘斜长片麻岩锆石U—Pb测年及其地质意义

Zircon UPb Dating and Its Geological Significance of Plagioclase Gneiss in the South Margin of Altun Fault in Qiemo County in Xinjiang Uygur Autonomous Region

摘要:

在阿尔金地块南缘构造混杂岩带中，新发现了多个规模较大的斜长片麻岩块体。运用LAICPMS 锆石UPb 定年分析方法，对阿尔金地块南缘且末大石门地区构造混杂岩带中的斜长片麻岩进行了年代学测定，并初步探讨其地质意义。30 个锆石颗粒的28个有效测点，测出的年龄明显分为2个区间：①(1784±41)～(2150±34)Ma 之间，加权平均值为(2130±27)Ma（MSWD=0.21，1σ）；②(2324±32)～(2684±51)Ma 之间，加权平均值为(2520±23)Ma（MSWD=0.06，1σ）。根据该次年龄测试结果和区域调查资料表明，阿尔金地块南缘且末大石门地区，在古元古代存在一期构造热事件，该期事件与吕梁运动的时限相吻合。

Abstract:

In the structural melange belt in the south margin of Altun, several largescale plagioclase gneiss blocks have been found. By using LAICPMS zircon UPb dating method, the chronology of plagioclase gneiss in the tectonic melange belt in the south margin of Altun and Dashimen area has been determined, and its geological significance has been discussed preliminarily. 28 effective sites of 30 zircon grains can be divided into two distinct intervals: one is between(1784±41)～(2150±34)Ma, and the weighted average value is (2130±27)Ma（MSWD=0.21，1σ）, the other is between (2324±32)～(2684±51)Ma，and the weighted average value is (2520±23)Ma（MSWD=0.06，1σ）. According to regional geological data, plagioclase gneiss blocks are derived from the Altun group. According to the results of this age test and regional survey data, there is a tectonic thermal event in Paleoproterozoic in the south margin of Altun and the last Dashimen area, which is agreement with the time limit of Lvliang movement.