柴达木盆地北缘新生代沉积物再旋回作用研究:以大红沟剖面为例  

Sediment recycling in the northern Qaidam Basin margin during the Cenozoic:A case study from the Dahonggou section

作　　者：桑胜萍 卢海建 叶家灿 潘家伟[1,2] 李海兵 SANG Shengping;LU Haijian;YE Jiacan;PAN Jiawei;LI Haibing(Key Laboratory of Deep-Earth Dynamics of Ministry of Natural Resources,Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China;Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou),Guangzhou 511458,Guangdong,China)

机构地区：[1]中国地质科学院地质研究所,自然资源部深地动力学重点实验室,北京100037 [2]南方海洋科学与工程广东省实验室,广东广州511458

出　　处：《中国地质》2024年第2期606-622,共17页Geology in China

基　　金：第二次青藏高原综合科学考察研究项目(2019QZKK0901);中国地质调查局项目(DD20190059);南方海洋科学与工程广东省实验室(广州)人才团队引进重大专项(GML2019ZD0201)联合资助。

摘　　要：【研究目的】近来,越来越多的研究显示沉积物再旋回作用在构造事件反演、沉积物源区识别以及风尘沉积溯源等方面具有重要作用。【研究方法】为了探究柴达木盆地新生代沉积物再旋回作用,本文对柴北缘大红沟剖面的砂岩进行了薄片鉴定、碎屑颗粒统计和重矿物等分析,以及对泥岩进行了主微量与稀土元素、黏土矿物等分析。【研究结果】大红沟剖面泥岩的主微量元素与稀土元素分别表现出相似的大陆上地壳(UCC)和球粒陨石标准化配分模式,可能表明沉积物已完全混合或发生再旋回作用;砂岩的主要成分为石英以及少量的长石和岩屑,其中岩屑主要由沉积岩屑组成,表明其源区主要为再旋回造山带;剖面上部稳定重矿物的含量和锆石、电气石和金红石(ZTR)指数突然降低,这表明后期可能主要为近源堆积;相反,黏土矿物中易发生分解的绿泥石的含量在剖面上部突然增加,这也表明此时的物源区更近,有更多的绿泥石保存下来。【结论】综合已有的地层沉积相、砂岩薄片以及碎屑锆石U-Pb年龄等资料,认为柴北缘逆冲褶皱带内广泛分布的侏罗系和白垩系沉积岩曾经历过大规模的沉积物再旋回作用,是盆地新生代地层的重要源区之一;近来的碎屑磷灰石裂变径迹分析表明,柴北缘新生代沉积岩在9~7 Ma经历了显著的沉积物再旋回作用;随着逆冲褶皱作用进一步向盆地内部扩展,~3 Ma以后盆地北部的隆起区沉积岩再次经历沉积物再旋回作用,可能成为柴达木盆地第四纪湖泊以及中国黄土高原黄土的重要源区。[Objective]Recently,more studies show that the sediment recycling plays an important role in the inversion of the tectonic events,the identification of sediment source areas and the sources of eolian dust.[Methods]In order to explore the Cenozoic sediment recycling in the Qaidam Basin,this paper conducts thin section identification,detrital framework grain composition and heavy mineral analysis of sandstones,and major,trace,and rare earth elements,and clay minerals of mudstones of the Dahonggou section in the northern Qaidam Basin.[Results]The major,trace,and rare earth elements of mudstones are similar to the standard distribution patterns of upper continental crust(UCC)and chondrite,which may indicate that the sediments have been completely mixed or recycled;Sandstone is mainly composed of quartz,and a small amount of feldspar and lithic grains which are mainly composed of sedimentary ones.Sandstone framework detrital mode indicates a provenance type of recycled orogenic belt;The content of stable heavy minerals and ZTR(zircon,tourmaline,and rutile)index suddenly decrease in the upper portion of the section,indicating a closer source area to the section during the late stage;On the contrary,the contents of chlorite,which is easy to decompose,suddenly increase in the upper portion of the section.This observation might also shows that its source area was closer at this time.[Conclusions]Based on the analysis of sedimentary facies,sandstone thin section and detrital zircon U-Pb age,it was suggested that the Jurassic and Cretaceous sedimentary rocks in the thrust-fold belt of the northern Qaidam Basin experienced large-scale sediment recycling and were one of the important provenances of the Cenozoic strata in the basin;Then,the fission-track analyses of detrital apatite show that the Cenozoic sedimentary rocks in the northern margin of the Qaidam basin have experienced significant recycling at 9-7 Ma;After about 3 Ma,with fold-thrusting propagating into the basin center,the uplifted sedimentary rocks in the northe

关 键 词：地球化学分析 碎屑颗粒统计 重矿物分析 沉积物再旋回作用 大红沟剖面 沉积盆地 柴达木北缘 地质调查工程 

分 类 号：P512.2[天文地球—地质学] P534.6