阿拉善地块东北缘狼山地区大红山组沉积时代、物质来源及区域构造意义  

The age and potential provenance information of Dahongshan Formation in the Langshan Mountain,the northeastern margin of the Alxa Block and its geological implications

作　　者：林灿楠 解国爱[1] 田荣松 王博[1] 张庆龙[1] LIN Cannan;XIE Guoai;TIAN Rongsong;WANG Bo;ZHANG Qinglong(School of Earth Sciences and Engineering,Nanjing University,Nanjing,210093;Resource and Environmental Engineering College,Guizhou University,Guiyang,550025)

机构地区：[1]南京大学地球科学与工程学院,南京210093 [2]贵州大学资源与环境工程学院,贵阳550025

出　　处：《地质论评》2022年第3期781-796,共16页Geological Review

基　　金：国家自然科学基金资助项目“华北中部新太古代—古元古代镁铁质火成岩地幔源区性质随时间变化的地球化学研究”(编号:42072218);国家重点研发计划项目“深部过程与成矿作用研究集成”(编号:2018YFC0603703);2020年南京大学本科教育教学改革项目的成果。

摘　　要：阿拉善地块位于中亚造山带南缘,是研究中亚造山带南缘二叠纪构造背景及演化的关键地区。本研究在阿拉善地块东北缘狼山地区野外调查的基础上,对狼山地区大红山组地层进行古流向、碎屑锆石LA-ICP-MS U-Pb定年和砂岩碎屑组分分析。研究表明砾石最大扁平面倾向为SWW—NWW,指示大红山组地层沉积时的古水流的流向总体呈现自西向东,推测大红山组砾石主要来自狼山西部地区。砂岩中碎屑锆石最小年龄峰值为275 Ma和278 Ma,表明大红山组沉积时代不早于中二叠世早期。砂岩的碎屑组分分析和碎屑锆石年龄谱指示大红山组可能来自于晚古生代诺尔公—狼山弧,砾石的古流向分析和碎屑锆石年龄谱推测大红山组砾石极有可能来自于阿拉善地块前寒武纪变质基底。结合诺尔公—狼山构造带晚古生代大陆岩浆弧的存在,认为二叠系大红山组地层沉积于弧背前陆盆地的构造背景。Objectives: Located in a key position in the southern Central Asian Orogenic Belt,the Alxa Block provides an ideal window to evaluate the Permian tectonic setting and evolution.Methods: Based on the field geological investigation in the Langshan region,northeastern margin of the Alxa Block,this study presents comprehensive research on the paleocurrent,sandstone components,and detrital zircon U-Pb dating from the Permian Dahongshan Formation.Results: The original maximum flat surface of gravel from the Dahongshan Formation dips to SWW to NWW,revealing the paleocurrent during the deposition of the Dahongshan Formation was generally from west to east and also suggesting gravels from this Formation mainly come from the western Langshan. Detrital zircons from the sandstone samples with the minimum age peaks of 275 Ma and 278 Ma constraints the depositional age of the Dahongshan Formation no earlier than the early Middle Permian.Conclusions: Paleocurrent data and detrital zircon age spectrum,coupled with sandstone components data support that the detrital materials of Dahongshan Formation originated from the Late Paleozoic magmatic arc,while the gravels were originated from the Alxa Block basement. Combined with the Late Paleozoic continental arc in the Nuoergong—Langshan tectonic belt,we suggest that the Dahongshan Formation was deposited in a retroarc foreland basin.

关 键 词：阿拉善地块 狼山 碎屑锆石 砂岩碎屑组分 古流向 弧背前陆盆地 

分 类 号：P548[天文地球—构造地质学] P512.2[天文地球—地质学]