呼伦贝尔巴彦塔拉砂砾石剖面沉积物组成和锆石U⁃Pb年龄——对沉积环境和区域岩浆构造事件的指示  

Sediment Composition and Zircon U-Pb Age of the Bayan Tara Gravel Profile in Hulun Buir,China:Indications for sedimentary environments and regional magmatic tectonic events

作　　者：时蕴琳 谢远云[1,2] 康春国[3] 迟云平[1,2] 魏振宇 吴鹏 孙磊 汪烨辉 SHI YunLin;XIE YuanYun;KANG ChunGuo;CHI YunPing;WEI ZhenYu;WU Peng;SUN Lei;WANG YeHui(College of Geographic Science,Harbin Normal University,Harbin 150025,China;Heilongjiang Province Key Laboratory of Geographical Environment Monitoring and Spatial Information Service in Cold Regions,Harbin Normal University,Harbin 150025,China;Department of Geography,Harbin University,Harbin 150086,China)

机构地区：[1]哈尔滨师范大学地理科学学院,哈尔滨150025 [2]哈尔滨师范大学寒区地理环境监测与空间信息服务黑龙江省重点实验室,哈尔滨150025 [3]哈尔滨学院地理系,哈尔滨150086

出　　处：《沉积学报》2024年第2期502-520,共19页Acta Sedimentologica Sinica

基　　金：国家自然科学基金项目(42171006,41871013)。

摘　　要：【目的】砂砾石沉积物的沉积学、地球化学、锆石U-Pb年代研究对于地层划分、水系演化以及揭示山体的构造隆升历史和区域构造岩浆事件等具有重要意义。然而,呼伦贝尔巴彦塔拉砂砾石剖面薄弱的认知限制了其地层划分以及区域地表过程的深入理解。【方法】为此,对该剖面进行了沉积学、重矿物、地球化学和锆石U-Pb年代学分析。【结果】(1)沉积学、重矿物、地球化学特征和地貌证据以及锆石U-Pb年龄综合分析显示,巴彦塔拉砂砾石剖面沉积物主要是来自大兴安岭北段的中—酸性岩浆母岩,是初次循环的结果,沉积物堆积后经历了中等程度的化学风化;(2)结合宏观和微观角度(重矿物和地球化学指标等),并与大兴安岭东麓白土山组标准剖面对比,认为巴彦塔拉砂砾石剖面沉积物是在温暖偏干的氧化环境下形成的冲—洪积物堆积,其地层单位可以划分为白土山组;(3)构造背景判别图解表明构造背景为被动大陆边缘,碎屑锆石U-Pb年龄在100~200 Ma和250~350 Ma的年龄峰值记录了大兴安岭北段在古亚洲洋的闭合和古太平洋的俯冲、回退的区域构造背景下触发的多期岩浆构造事件。【结论】该研究为大兴安岭地区第四纪地层的划分和早更新世区域地表过程的重建提供了新的证据。[Objective]The study of the sedimentology,geochemistry and zircon U-Pb dating of sand-gravel sediments is highly significant for determining stratigraphic division,river system evolution,mountain tectonic uplift history and regional tectono-magmatic events.However,little is understood regarding the Hulun Buir Bayan Tara sandgravel profile,which has restricted its stratigraphic division and in-depth understanding of the regional surface process.[Methods]For this reason,analyses of the sedimentology,heavy mineral,geochemical(macronutrients,trace and rare earth elements)and zircon U-Pb chronology were performed on this section to determine the chemical weathering characteristics and sedimentary cycles,as well as the material sources,and to explore the stratigraphic delineation attribution as well as the tectonic context and indications of regional magmatic-tectonic events.This has provided a new basis for discussion of areas of sedimentary environment and stratigraphic division and correlation.[Results]The following results were obtained.(1)The gravels are poorly sorted and rounded,and have undergone a non-weak degree of weathering,with quartzaceous material(61.2%)and tuff(34.9%)dominating the gravel composition,followed by terrigenous clastics(2.6%)and rhyolite(1.3%).The heavy mineral composition is clearly dominated by white titanium(32.54%)and ilmenite(33.01%),followed by magnetite(12.11%),zircon-tourmalinerutile(ZTR)(6.53%),hematite(5.47%)and anatase(1.34%),with less than 1%chlorite,rutile and garnet.There are very few,if any,unstable minerals in the sediments,indicating that they have undergone strong chemical weathering.Combined with geochemical characteristics and geomorphological evidence,the comprehensive analysis shows that the maturity of the sediment in the Bayan Tara sand-gravel profile is low,and is the product of the first weathering cycle,with moderate chemical weathering after accumulation.Comparison with the age spectrum of detrital zircons in the northern section of the Greater Khingan Mountains i

关 键 词：锆石U-PB测年 地球化学 地层划分 沉积环境 白土山组 大兴安岭 

分 类 号：P535[天文地球—古生物学与地层学]