扬子陆块西北缘米仓山地区新元古代早期沉积盆地演化:沉积序列与锆石U-Pb年代学证据  

Early Neoproterozoic sedimentary basin evolution in the Micangshan area,northwestern Yangtze Block:Constraints from the depositional sequence and zircon U-Pb chronology

作　　者：邓奇 汪正江 丛峰 宁括步 任光明 崔晓庄 熊国庆 刘家洪 DENG Qi;WANG Zhengjiang;CONG Feng;NING Kuobu;REN Guangming;CUI Xiaozhuang;XIONG Guoqing;LIU Jiahong(Chengdu Center,China Geological Survey(Geosciences Innovation Center of Southwest China),Chengdu,Sichuan 610218,China)

机构地区：[1]中国地质调查局成都地质调查中心(西南地质科技创新中心),四川成都610218

出　　处：《地质学报》2024年第11期3354-3367,共14页Acta Geologica Sinica

基　　金：国家自然科学基金项目(编号U2344209);四川省自然科学基金项目(编号23NSFSC0275);四川省科技发展专项(编号2023ZYD0153);中国地质调查局项目(编号DD20242881,DD20243477)联合资助的成果。

摘　　要：米仓山地区的火地垭群和正源-英萃变质火山-沉积岩系(原后河岩群)是扬子陆块西北缘前寒武纪发育的重要地层单元,是研究其形成时期沉积盆地演化过程及其与Rodinia超大陆聚合关系的重要载体,然而其准确的演化时限及构造属性仍存在较大争议。本文选择典型地层剖面对火地垭群开展系统的沉积序列演化研究,对正源-英萃变质火山-沉积岩系开展碎屑锆石U-Pb同位素年代学研究。结果显示,火地垭群是一套由碎屑岩-碳酸盐岩-碎屑岩夹火山岩构成的复杂沉积岩石组合,沉积序列及其他研究成果综合分析表明,盆地经历了三个演化阶段:(1)洋壳俯冲与弧盆开启;(2)弧后扩展与碳酸盐缓坡/台地建设;(3)盆地挠曲沉降与快速充填。正源-英萃变质火山-沉积岩系形成于新元古代早期,接受来自西北和东(南)部的双向物源供给,与火地垭群为同期异相地层,应是同一盆地不同部位的沉积产物,它们均为Rodinia超大陆汇聚过程在扬子陆块西北缘的沉积响应。The Huodiya Group and the Zhengyuan-Yingcui volcanic-sedimentary rocks(formerly known as the Houhe Group)from the Micangshan area of the northwestern Yangtze Block provide significant records of the mid-Neoproterozoic tectonic evolution related to the assembly of the Rodinia supercontinent.However,their evolutionary history and tectonic characteristics remain uncertain.This paper presents a systematic analysis of sedimentary sequences within typical sections of the Huodiya Group,complemented by detrital zircon U-Pb geochronology of the Zhengyuan-Yingcui volcanic-sedimentary rocks.This integrated approach aims to elucidate their tectonic-sedimentary evolution processes and establish a precise timeframe for these events.Our comprehensive investigations reveal that the Huodiya Group comprises a complex assemblage of sedimentary rocks,characterized by interbedded clastic,carbonatite,and volcanic rocks.The evolution history of the basin can be divided into three stages:(1)subduction of oceanic crust and the formation of an arc-basin system;(2)back-arc extension and the construction of a carbonate ramp/platform;(3)flexural subsidence in the basin and rapid infilling.Detrital zircon analysis indicates that the Zhengyuan-Yingcui volcanic-sedimentary rocks were deposited in the early Neoproterozoic and sourced from both the northwestern and east/southeastern sides of the basin.This finding,coupled with the contemporaneous yet spatially distinct nature of the Zhengyuan-Yingcui volcanic-sedimentary rocks and the Huodiya Group,suggests that they developed in different parts of the basin,which could be the response of the assemblage of the Rodinia supercontinent.

关 键 词：扬子陆块西北缘 新元古代 沉积序列 锆石U-PB年代学 盆地演化 

分 类 号：P534.3[天文地球—古生物学与地层学] P512.2[天文地球—地质学] P597.3