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中国沙漠 ›› 2020, Vol. 40 ›› Issue (6): 105-117.DOI: 10.7522/j.issn.1000-694X.2020.00078

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青藏高原东北部晚第四纪黄土-古土壤的元素组成及其物源指示

曾方明1(), 薛红盼1,2   

  1. 1.中国科学院青海盐湖研究所 中国科学院盐湖资源综合高效利用重点实验室/青海省盐湖地质与环境重点实验室,青海 西宁 810008
    2.中国科学院大学,北京 100049
  • 收稿日期:2020-05-08 修回日期:2020-07-24 出版日期:2020-12-09 发布日期:2020-12-09
  • 作者简介:曾方明(1982—),男,湖南邵阳人,博士,副研究员,研究方向为黄土地球化学。E-mail: fmzeng@163.com
  • 基金资助:
    中国科学院青年创新促进会专项项目(2017468);第二次青藏高原综合科学考察研究项目(2019QZKK0805)

Elemental compositions of the late Quaternary loess-paleosol on the northeastern Qinghai-Tibet Plateau and their implications for provenance

Fangming Zeng1(), Hongpan Xue1,2   

  1. 1.Key Laboratory of Comprehensive and Highly Efficient Utilization of Salt Lake Resources / Qinghai Provincial Key Laboratory of Geology and Environment of Salt Lakes,Qinghai Institute of Salt Lakes,Chinese Academy of Sciences,Xining 810008,China
    2.University of Chinese Academy of Sciences,Beijing 100049,China
  • Received:2020-05-08 Revised:2020-07-24 Online:2020-12-09 Published:2020-12-09

摘要:

青藏高原东北部的晚第四纪黄土-古土壤记录了该区环境变化的信息,以往的物源研究样品空间覆盖度不足,仍需进一步研究。在青藏高原东北部较大范围地采集了黄土-古土壤、风成砂、河流沉积、湖相沉积样品,并对这些样品小于75 μm组分的元素组成进行了X射线荧光光谱(XRF)分析。结果表明:(1)青藏高原东北部晚第四纪黄土-古土壤的元素组成以SiO2、Al2O3、Fe2O3、CaO为主;与UCC(上地壳)相比,青藏高原东北部晚第四纪黄土-古土壤的CaO、MgO含量较高,Na2O、K2O含量较低。(2)具有物源指示意义的K2O/Al2O3(摩尔比)、TiO2/Al2O3(摩尔比)、Zr/Nb和Zr/Ti比值图解显示青藏高原东北部青海湖地区的晚第四纪黄土-古土壤与当地的河流沉积、湖相沉积存在较大差异,揭示它们来自青海湖地区以外的区域。(3)K2O/Al2O3(摩尔比)、TiO2/Al2O3(摩尔比)、Zr/Nb和Zr/Ti比值图解显示青藏高原东北部的晚第四纪黄土-古土壤与柴达木盆地的风成砂、河流沉积和湖相沉积重叠在一起,表明柴达木盆地的风化细碎屑物质在近地面西北风、高空西风环流的作用下很可能为青藏高原东北部黄土-古土壤的堆积提供了主要物源。

关键词: 黄土, 古土壤, 元素地球化学, 物源, 青藏高原东北部

Abstract:

Late Quaternary loess-paleosol deposits on the northeastern Qinghai-Tibet Plateau (NE QTP) recorded information of environmental changes in this area. Previous studies have been carried out on their source area. However, due to the insufficient space coverage of samples in previous studies, this issue still needs further study. We collected samples of loess-paleosol, eolian sands, fluvial sediments and lacustrine deposits on the NE QTP. Chemical compositions of these samples (less than 75 μm fraction) were determined by X-ray fluorescence (XRF) spectrometry. The results show that: (1) The chemical composition of the late Quaternary loess-paleosol on the NE QTP is mainly composed of SiO2, Al2O3, Fe2O3, and CaO; compared with the composition of UCC (upper continental crust), the late Quaternary loess-paleosol on the NE QTP has higher CaO and MgO content, lower Na2O and K2O content. (2) K2O/Al2O3 (molar ratio), TiO2/Al2O3 (molar ratio), Zr/Nb and Zr/Ti ratios show that the source area of the late Quaternary loess-paleosol in the Qinghai Lake area on the NE QTP is different from that of the fluvial sediments and lacustrine sediments in this area, indicating that the loess-paleosol in the Qinghai Lake area is probably from a region far away from the Qinghai Lake area. (3) K2O/Al2O3 (molar ratio), TiO2/Al2O3 (molar ratio), Zr/Nb and Zr/Ti ratios show that the late Quaternary loess-paleosol on the NE QTP and the eolian sand, fluvial sediments and lacustrine deposits in the Qaidam Basin cannot be distinguished, indicating that the weathered detrital material in the Qaidam Basin is likely to provide substantial material for loess-paleosol on the NE QTP under the influence of the near-surface northwest wind and the Westerly circulation.

Key words: loess, paleosol, elemental geochemistry, provenance, northeastern Qinghai-Tibet Plateau

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