扬子板块西缘盐边群及周边岩体地质年代学新格局

扬子板块西缘的盐边群及其周边岩体,作为前寒武纪构造岩浆活动带的核心,是观察和研究新元古代大陆壳生长的重要窗口.查明这一构造岩浆活动带内地质体的产出时代及构造岩浆活动的轨迹,是揭示新元古代大陆壳产生、发展地球动力学过程的重点环节.对盐边群及周边岩体的地质年代学研究表明:(1)区内大规模的岩浆事件集中在中元古代晚期至新元古...

New geochronology framework of Yanbian Group and its surrounding magmatic bodies in western margin of Yangtze Block,China

As the core of the Precambrian tectono-magmatic activity zone,the Yanbian Group and its surrounding magmatic rocks in the western margin of the Yangtze Block are important windows to observe and study the growth of the Neoproterozoic continental crust.It is the key link to reveal the geodynamic process of the formation and development of the Neoproterozoic continental crust and find out the time of the formation of the interior bodies and the track of the tectono-magmatic activity in this tectono-magmatic activity zone.The geochronology study of the Yanbian Group and its surrounding magmatic rocks shows that:(1)The large scale magmatic events in the area were concentrated in the late Mesoproterozoic to early Neoproterozoic,and the marine basalt of the Huangtian Formation first appeared in 1122~1038 Ma B.P.The zircon U-Pb ages of the early Guandaoshan rock mass are 988±51 Ma(N=6)and 924±17 Ma(N=9),and extend to 857 Ma B.P.The age of Tongde rock mass mainly concentrates in 886~814 Ma with the peak age of 847.2±4.9 Ma(N=39).(2)The deposition age of Yumen and Xiaoping Formations of the Yanbian Group was later than the age of Huangtian Formation basalts,and Guandaoshan and Tongde magmatic rock masses.(3)The detrital zircons of the Yanbian Group have nearly the same age as the U-Pb zircons of the magmatic rock masses around the Yanbian Group.Whether there is a genetic relationship between them needs to be further confirmed.It is a prerequisite to reconstruct the growth and geodynamic process of the new continent crust on the western margin of the Yangtze Block by taking the Yanbian Group and the surrounding magmatic rock mass as the core and extending to the south,east and north directions,at the same time to verify the generation age,spatial distribution and provenance characteristics of the major magmatic geological bodies in the area.