四川茂县渭门组凝灰岩锆石SHRIMPU-Pb测年及地质意义  

Zircon SHRIMP U-Pb Dating and Geological Significance of the Weimen Group Tuffs From Mao County, Sichuan Province

作　　者：白富正[1] 王一伟[1] 罗绍强[1] 吕行[1] 母永鸿 

机构地区：[1]四川省地质矿产勘查开发局川西北地质队,绵阳621000

出　　处：《高校地质学报》2015年第1期163-167,共5页Geological Journal of China Universities

基　　金：中国地质调查局地质调查项目(1:25万绵阳幅区域地质调查;1212011220411)资助

摘　　要：对出露于松潘-甘孜褶皱带四川茂县渭门一带的渭门组的形成时代一直令人关注,但迄今为止未见其形成年龄的报道,在开展1∶25万绵阳幅区域地质调查（修测）时,在渭门组中上段发育近100 m厚的具地层意义的凝灰岩中采集高精度SHRIMP测年样品一件,获得SHRIMP U-Pb加权平均年龄为530.1±4.3 Ma（MSWD=1.5）。样品中的锆石Th/U介于0.36-1.09 Ma之间,并具清晰的振荡环带结构,均为岩浆成因的锆石,表明渭门组形成于早寒武世,为准确地界定渭门组的时代和层序提供了新的参考依据,对正确认识松潘-甘孜褶皱带的地层格架和构造濱化具有重要意义。The age of the Weimen Group that is exposed in Songpan-Ganzi（Sichuan） fold belt is of great interest. But so far there are noreports of its formation age. During a 1：250000 scale survey of Mianyang area, a nearly 100 m thick tuff bed in the Upper WeimenGroup was identified and one sample was collected for high precision SHRIMP dating. A SHRIMP U-Pb weighted mean age of 530.1 ±4.3 Ma（MSWD = 1.5） was obtained. The zircon Th / U ratios of the sample are from 0.36 to 1.09, and zircon grains show a clearoscillatory banding structure, indicating that zircons are of magmatic origin. The age results suggest that the Weimen Group was formedin the early Cambrian. The new age provides a chronologic basis for understanding the tectonic evolution of the Songpan-Ganzi foldbelt.

关 键 词：四川茂县 渭门组 锆石SHRIMP U-PB年龄 早寒武世 

分 类 号：P588.12[天文地球—岩石学]