摘要
扬子板块的太古宙-古元古代基底出露十分有限,制约了对扬子早前寒武纪地质演化的认识。本次研究对扬子板块西南缘撮科地区的大红山群和昆阳群变沉积岩开展了碎屑锆石原位U-Pb年龄、Hf-O同位素及微量元素研究。测年结果显示,大红山群谐和锆石年龄分布于3092~1786Ma之间,最年轻碎屑锆石年龄为1786Ma,限定大红山群最大沉积时代为古元古代晚期。昆阳群谐和锆石年龄分布于2874~1031Ma之间,最年轻碎屑锆石年龄为1031Ma,表明昆阳群最大沉积时代为中元古代晚期。除少量较年轻锆石(<1.75Ga)外,昆阳群和大红山群具有相似的年龄分布特征,两个主要的年龄峰为2.0~1.85Ga和2.4~2.2Ga。尽管古元古代碎屑锆石的年龄峰与撮科地区已报道的古元古代岩浆活动期次一致,但仅有少部分碎屑锆石的Hf-O同位素特征与撮科古元古代岩浆岩相似,大多数碎屑锆石Hf-O同位素组成与加拿大Rae克拉通古元古代变沉积岩中碎屑锆石相似,暗示古元古代碎屑物质可能仅少部分来自撮科地区已识别的古元古代岩浆岩,而大部分可能来自与Rae克拉通发育的古元古岩浆岩相似的源区。大红山群和昆阳群中1.9~1.03Ga的碎屑锆石可能来自扬子西南缘发育的古元古代晚期-中元古代晚期岩浆岩。结合前人的资料,我们认为我国撮科和越南北部的Phan Si Pan带经历了与加拿大Rae克拉通相似的古元古代演化过程,支持2.4~2.3Ga扬子西南缘卷入Arrowsmith造山事件,并与Rae克拉通一起参与哥伦比亚超大陆聚合过程的认识。
The exposure of the Archean-Paleoproterozoic basement in the Yangtze Block is very limited,which constrains the understanding of its Early Precambrian geological evolution.In this study,U-Pb ages,Hf-O isotopes and trace elements of detrital zircon from the metasedimentary rocks of the Dahongshan and Kunyang groups in the Cuoke area are reported.Zircon from Dahongshan Group yield a spectrum age ranging from 3092 to 1786Ma,and the youngest detrital zircon has an age of 1786Ma,limiting the maximum depositional age of the Dahongshan Group to the Late Paleoproterozoic.The age distribution of the concordant zircon in the Kunyang Group is between 2874Ma and 1031Ma,and the youngest age of detrital zircon is 1031Ma,indicating that the maximum depositional age of the Kunyang Group is the late Middle Proterozoic.Except for a small amount of younger zircon(<1.75Ga),the Kunyang and Dahongshan groups have similar age distribution characteristics,with two main age peaks of 2.0~1.85Ga and 2.4~2.2Ga.Although the age peaks observed in the Paleoproterozoic detrital zircon are consistent with the Paleoproterozoic magmatic rocks reported in the Cuoke area,only a small portion of the detrital zircon have Hf-O isotopic characteristics similar to the Paleoproterozoic magmatic rocks in the Cuoke area,and most of the detrital zircon have Hf-O isotopic compositions similar to those of the Paleoproterozoic metasedimentary rocks of the Rae Craton in Canada,which suggests that a small portion of the Paleoproterozoic components originated from the identified Paleoproterozoic magmatic rocks in the Cuoke area,and most of them may be derived from a source region which is similar to the Paleoproterozoic magmatic rocks developed in the Rae Craton.The 1.9~1.03Ga detrital zircon in the Dahongshan and Kunyang groups may be derived from the Late Paleoproterozoic-Late Mesoproterozoic magmatic rocks distributed in the southwestern margin of the Yangtze Block.Combined with previous studies,we suggest that the Paleoproterozoic tectonic evolution of the Cuoke area in China and Phan Si Pan belt in northern Vietnam is similar to that of the Rae Craton in Canada,supporting the proposal that the southwestern margin of the Yangtze Block was involved in the Arrowsmith orogeny,and then underwent the assembly of the Columbia supercontinent together with the Rae Craton.
作者
高嘉敏
谢士稳
刘倩
王舫
陶鹏
龙涛
GAO JiaMin;XIE ShiWen;LIU Qian;WANG Fang;TAO Peng;LONG Tao(School of Earth Science and Resources,China University of Geosciences(Beijing),Beijing 100083,China;Beijing SHRIMP Center,Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China;Shandong Provincial No.4 Institute of Geological and Mineral Survey,Weifang 261021,China)
出处
《岩石学报》
SCIE
EI
CAS
北大核心
2025年第1期304-320,共17页
Acta Petrologica Sinica
基金
国家自然科学基金项目(42172219、41772193)
中国地质科学院基本科研业务费专项经费(JKYQN202312)联合资助.
关键词
扬子西南缘
撮科地区
哥伦比亚超大陆
大红山群和昆阳群
碎屑锆石
Southwest margin of the Yangtze Block
Cuoke area
Columbia Supercontinent
Dahongshan and Kunyang groups
Detrital zircon
