华北克拉通北缘内蒙古达茂旗地区前寒武纪基底岩石组合及形成时代

在华北克拉通北缘达茂旗地区, 近东西向分布前寒武纪基底, 前人根据岩石组合特征将其划为色尔腾山岩群, 但缺乏年代学依据。通过岩石学、LA-ICP-MS锆石U-Pb年龄及其微量元素地球化学、锆石Lu-Hf同位素等研究对达茂旗地区前寒武纪基底岩石组合、形成时代、物质来源进行讨论。研究表明, 达茂旗地区前寒武纪基底由色尔腾山岩群和古元古代变质侵入岩构成。色尔腾山岩群由黑云斜长片麻岩、大理岩组成, 形成时间为2009~2142 Ma, 属古元古代。古元古代存在2期侵入岩, 分别为1992~1999 Ma、1920 Ma。达茂旗地区在约2.6 Ga、2009~2142 Ma分别发生过陆壳增生作用, 并受到古老陆壳物质混染, 1999~1992 Ma的碱长花岗岩与石英闪长岩为新生陆壳重熔产物, 可能受到古老陆壳物质混染; 1920 Ma的黑云母二长花岗岩为古老陆壳重熔产物。这些认识为进一步研究华北克拉通北缘前寒武纪构造发展演化提供了更多依据。

Precambrian basement rock assemblage and formation age in Damaoqi area of Inner Mongolia,northern margin of the North China Craton

Precambrian basement is distributed nearly east-west trending in the Damaoqi area along the northern margin of the North China Craton.Previous studies classified it as the Sertengshan Group based on the characteristics of rock assemblage, but without chronological evidence.This paper discusses the Precambrian basement rock assemblage, formation age and material source in this area, based on petrology, LA-ICP-MS zircon U-Pb age and trace element geochemistry, and zircon Lu-Hf isotope.The research shows that the Precambrian basement is composed of the Sertengshan Group and Paleoproterozoic metamorphic intrusions.The Sertengshan Group is composed of biotite plagiogneiss and marble, formed during 2009~2142 Ma and belongs to the Paleoproterozoic.There are two periods of intrusions in Paleoproterozoic, 1992~1999 Ma and 1920 Ma respectively.In the Damaoqi area, continental crust accretion occurred at ~2.6 Ga and 2009~2142 Ma, respectively.The alkali feldspar granite and quartz diorite formed at 1999~1992 Ma were remelted products of juvenile continental crust, which may be contaminated by ancient continental crust materials.The biotite monzogranite formed at 1920 Ma was the product of the remelting of the ancient continental crust.The results of this study provide more evidences for the Precambrian tectonic evolution of the northern margin of the North China Craton.