闽西南下古生界东坑口组与魏坊组地层层序与物源区特征——来自碎屑锆石LA-ICP-MS U-Pb测年的约束

闽西南地区下古生界魏坊组与东坑口组地层层序长期以来一直存在争议。应用LA-ICP-MS U-Pb测年,对闽西南地区下古生界魏坊组与东坑口组进行了120颗碎屑锆石的U-Pb测年,获得锆石年龄范围为506~3431Ma,主要分布于511~2796Ma之间,主要峰值年龄为964Ma,次要峰值年龄为514Ma,并存在813Ma、1231Ma、2483Ma的次级峰。年龄谱特征显示,魏坊组沉积早于东坑口组,东坑口组时代不属于中上寒武世。下古生界物源以964Ma峰值为代表,反映Grenville构造热事件的物源最显著。还获得了较丰富的峰值年龄为514Ma的泛非期构造热事件年龄,以及古太古代锆石年龄记录,为闽西南地区下古生界地层层序的确立和物源研究提供了重要新资料。

Stratigraphic sequence and characteristics of the source area of Lower Paleozoic Weifang Formation and Dongkengkou Formation in southwestern Fujian:Constraints from detrital zircon LA-ICP-MS U-Pb dating

The stratigraphic sequence of Lower Paleozoic Weifang Formation and Dongkengkou Formation in southwestern Fujian has long been a problem of controversy. In this paper, the authors studied geochronology of 120 detrital zircon samples from the Lower Paleozoic Weifang Formation and Dongkengkou Formation sedimentary rocks in southwestern Fujian by LA-ICP-MS U-Pb dating, and obtained zircon ages ranging from 506Ma to 3431Ma, with most of the data from 511Ma to 2796Ma, the main peak value 964Ma, a secondary peak value 514Ma, and secondary peak values 813Ma, 1231Ma, 2483Ma. Characteristics of the age spectrum suggest that Weifang Formation was deposited earlier than Dongkengkou Formation. Age of Dongkengkou Formation does not belong to MiddleUpper Cambrian. Lower Paleozoic source with peak value at 964Ma most significantly reflects the Grenville tectonic event. The au-thors also received peak value age of 514Ma of Pan-African tectonic event. In addition, the authors found Paleoarchean zircon ages re-cord. Important new information is thus provided for the establishment of Lower Paleozoic stratigraphic sequence; source studies.