摘要
吉林省永吉县头道沟地区出露许多与头道沟岩组相伴产出的镁铁—超镁铁质岩,鉴于其处于长春-延吉构造带附近而受到业内关注,但由于缺少高精度年代学资料,制约了对区域大地构造的深入研究。本文采用锆石U-Pb(LA-ICP-MS)方法,对镁铁—超镁铁质岩进行了年代学研究。变质辉绿岩年龄为270±5 Ma,变质橄榄岩中捕获锆石最小年龄为297 Ma,考虑岩石组合及二者紧密相伴产出,认为二者均形成于中二叠世。镁铁—超镁铁质岩中捕获的锆石记录了华北克拉通及其北缘多次重要的构造热事件。其中,变辉绿岩中获得446±6 Ma的年龄与变质橄榄岩中获得的不一致线下交点434±240 Ma年龄共同对应了华北克拉通北缘早古生代的重要构造岩浆热事件;大量的1.8~2.4Ga年龄对应古元古代辽吉造山带热事件;1377 Ma、1542 Ma与蓟县系建造时代对应;869~997 Ma与青白口系建造时代对应;在变质辉绿岩中还存在众多3.0~3.2Ga锆石年龄。分析上述年龄结构及龙岗陆块北缘古生代地质体分布特征,推测研究区深部可能存在古老的变质基底,同时也表明研究区出露的镁铁—超镁铁质岩形成于陆内构造环境,而非蛇绿岩的组成成分,这对深化区域大地构造研究具有重要意义。
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 highprecision 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±5Ma for metadiabase and a minimum age of 297Ma 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 tectonomagmatic thermal event in the northern margin of North China Craton.A large number of 1.8~2.4Ga ages corresponds to the Paleoproterozoic thermal events in Liao-Ji orogenic belt,while 1377 Ma and 1542Ma corresponds to the era of Jixianian.869~997 Ma corresponds to the formation era of the Qingbaikouan.In addition,zircons with age of 3.0~3.2Ga 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.
作者
付俊彧
孙巍
汪岩
钟辉
那福超
杨帆
张广宇
于宏斌
FU Junyu;SUN Wei;WANG Yan;ZHONG Hui;NA Fuchao;YANG Fan;ZHANG Guangyu;YU Hong bin(Shenyang Geological Survey Center,China Geological Survey,Shen yang,110034;Jilin Province Institute of Regional Geology and Mineral Survey,Changchun,130012)
出处
《地质学报》
EI
CAS
CSCD
北大核心
2018年第9期1859-1872,共14页
Acta Geologica Sinica
基金
中国地质调查局项目(编号DD20179383
1212011220435
DD20160343-08
DD20160343-09)资助成果
