引用本文：付俊彧,孙巍,汪岩,钟辉,那福超,杨帆,张广宇,于宏斌.2018.吉林永吉县头道沟地区镁铁—超镁铁质岩U-Pb年代学研究及地质意义[J].地质学报,92(9):1859-1872. FU Junyu,SUN Wei,WANG Yan,ZHONG Hui,NA Fuchao,YANG Fan,ZHANG Guangyu,YU Hong bin.2018.Zircon U-Pb Chronology of the Toudaogou Mafic-Ultramafic Rocks from Yongji, Jilin Province, and Its Geological Implications[J].Acta Geologica Sinica,92(9):1859-1872.
Abstract:A large amount of mafic-ultramafic rocks, which are accompanied with the Toudaogou Formation, occurs in the Toudaogou area, Yongji County, Jilin Province. They have received wide attention from geological industry due to its location near to the Changchun-Yanji tectonic belt. But lacking the high-precision chronology data has greatly restricted the in-depth study of regional tectonic. In this paper, we conducted chronological study for the mafic-ultramafic rocks using zircon U-Pb dating (LA-ICP-MS) method. The study yielded an age of 270±5 Ma for metadiabase and a minimum age of 297 Ma for zircons captured in the metamorphic peridotite. Considering the rock association and their close occurrence, we thought they were both formed in Middle Permian. The zircons captured in the mafic-ultramafic rocks record many important tectonic heat events occurring in the North China Craton and its northern margin. Among them, an age of 446±6 Ma yielded for the metadiabase might indicate the age of magmatic event, and the age of 434±240 Ma for metamorphic peridotite may reflect an important Early Paleozoic tectono-magmatic thermal event in the northern margin of North China Craton. A large number of 1.8~2.4 Ga ages corresponds to the Paleoproterozoic thermal events in Liao-Ji orogenic belt, while 1377 Ma and 1542 Ma corresponds to the era of Jixianian. 869~997 Ma corresponds to the formation era of the Qingbaikouan. In addition, zircons with age of 3.0~3.2 Ga occur commonly in metadiabase. Based on analysis of the age structure and distribution characteristics of the Paleozoic geological bodies in the northern margin of Longgang landmass, this study suggests that there may exist an old metamorphic basement in the study area, and that the exposed mafic-ultramafic rocks formed in the intracontinental tectonic environment, rather than the components of ophiolite. This understanding is of great significance in deepening the research on regional tectonic.