鄂尔多斯盆地延河剖面延长组碎屑错石U-Pb年龄分布特征及地质意义

摘要

In our study, we measures the U-Pb age of detrital Zircon in the middle and lower formation of Upper Triassic Yanchang Formation in Yanhe Section of Ordos Basin , the results show that the most outstanding Zircon U-Pb age of the samples are 2 271-2 567 Ma and 1 599-1 937 Ma, and five zircons having a small amount of young magma zircon have a U-Pb ages of 261-285 Ma.The study shows that the time interval of 2 271 Ma and 2 567 Ma with a peak of about 2 500 Ma is an effective evidence for the activity of mantle adding related to basaltic magma in the late Late Archean in North China Craton.While the time interval of 1 599 Ma and 1 973 Ma with a peak of about 1 800 Ma is an effective evidence for tectonic heat event initiated by continent-continent collision of Columbia Supercontinent during the Palaeoproterozoic and the structure movement during the Mesoproterozoic in North China Craton.Magma zircon age distributed between 261Ma and 285Ma of the five zircons is the main evidence for magma intrusion activity during the Early Indo-Chinese.In this paper, we used the detrital zircon age to determine that the Craton provenance of North China from which the clastic sediments of Yanhe Strata Section come from in the interval of about 2500Ma, that is, from the Late Archaean, Palaeoproterozoic deeply metamorphosed diorite, gneiss and granulitite of Yinshan Mountain.%通过鄂尔多斯盆地东部延河剖面上三叠统延长组中下部地层中碎屑锆石U-Pb同位素年龄测定显示:锆石年龄以2 271～2 567Ma和1 599～1 937 Ma最为突出,还有少量的261～285 Ma年轻岩浆锆石.研究表明,分布在2 271～2 567 Ma、以2 500 Ma为峰值的碎屑锆石年龄是华北克拉通晚太古代与地幔添加有关的玄武质岩浆活动的证据.1 599～1 937 Ma、以1 800 Ma为峰值的年龄为华北克拉通早元古代哥伦比亚超大陆陆-陆碰撞构造热事件以及中元古代构造运动的证据.出现的5颗261～285Ma的岩浆锆石,主要为华力西期岩浆侵人活动的证据.笔者从碎屑锆石年龄的角度确定了延河剖面碎屑沉积物来自以约2 500 Ma为主的华北克拉通物源区,即来源于阴山地区的晚太古代、早元古代的深变质闪长岩、片麻岩和变粒岩.