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首页> 外文期刊>Journal of Asian earth sciences >Greigite formed in early Pleistocene lacustrine sediments from the Heqing Basin, southwest China, and its paleoenvironmental implications
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Greigite formed in early Pleistocene lacustrine sediments from the Heqing Basin, southwest China, and its paleoenvironmental implications

机译：西南鹤庆盆地更新世早期湖相沉积物中的钙铁矿及其古环境意义

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摘要

The ferrimagnetic iron sulfide greigite (Fe3S4) occurs widely in sulfidic lacustrine and marine sedimentary environments. Knowledge of its formation and persistence is important for both magnetostratigraphic and paleoenvironmental studies. Although the formation mechanism of greigite has been widely demonstrated, the sedimentary environments associated with greigite formation in lakes, especially on relatively long timescales, are poorly understood. A long and continuous sequence of Pleistocene lacustrine sediments was recovered in the Heqing drill core from southwestern China, which provides an outstanding record of continental climate and environment. Integrated magnetic, geochemical, and paleoclimatic analysis of the lacustrine sequence provides an opportunity to improve our understanding of the environmental controls on greigite formation. Rock magnetic and scanning electron microscope analyses of selected samples from the core reveal that greigite is present in the lower part of the core (part 1, 665.8-372.5 m). Greigite occurs throughout this interval and is the dominant magnetic mineral, irrespective of the climatic state. The magnetic susceptibility (chi) record, which is mainly controlled by the concentration of greigite, matches well with variations in the Indian Summer Monsoon (ISM) index and total organic carbon (TOC) content, with no significant time lag. This indicates that the greigite formed during early diagenesis. In greigite-bearing intervals, with the chi increase, B-c value increase and tends to be stable at about 50 mT. Therefore, we suggest that chi values could estimate the variation of greigite concentration approximately in the Heqing core. Greigite favored more abundant in terrigenous-rich and organic poor layers associated with weak summer monsoon which are characterized by high chi values, high Fe content, high Rb/Sr ratio and low TOC content. Greigite enhancement can be explained by variations in terrigenous inputs. Our studies demonstrate that, not only the greigite formation, but also its concentration changes could be useful for studying climatic and environmental variability in sulfidic environments.
机译：亚铁磁性硫化铁钙铁矿（Fe3S4）广泛存在于硫化湖相和海洋沉积环境中。对于磁地层学和古环境研究而言，有关其形成和持久性的知识都很重要。尽管钙镁石的形成机理已得到广泛证实，但与湖泊中钙铁矿形成有关的沉积环境，尤其是在相对较长的时间尺度上，了解得很少。在中国西南部的鹤庆钻探岩心中发现了一个长而连续的更新世湖相沉积物，这是大陆气候和环境的杰出记录。湖泊序列的磁性，地球化学和古气候综合分析为我们提供了一个机会，使我们对钙铁矿形成的环境控制有了更深入的了解。岩心和扫描电子显微镜对岩心中选定样品的分析表明，岩心存在于岩心下部（第1部分，665.8-372.5 m）中。钙铁矿在整个时间间隔内发生，并且是占主导地位的磁性矿物，与气候状态无关。磁化率（chi）记录主要由钙铁矿的浓度控制，与印度夏季风（ISM）指数和总有机碳（TOC）含量的变化非常匹配，没有明显的时间滞后。这表明在早成岩过程中就形成了钙铁矿。在含钙铁矿的时间间隔中，随着chi的增加，B-c值增加，并趋于稳定在约50 mT。因此，我们认为chi值可以估计鹤庆岩心中的辉绿岩浓度的变化。灰云母偏爱夏季季风薄弱的陆源丰富和有机质较差的地层，这些地层的特征在于具有较高的chi值，较高的Fe含量，较高的Rb / Sr比和较低的TOC含量。 Greigite增强可以通过陆源输入的变化来解释。我们的研究表明，不仅钙铁矿的形成，而且其浓度的变化对于研究硫化环境中的气候和环境变化也可能是有用的。

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  • 来源
    《Journal of Asian earth sciences》 |2018年第may1期|256-264|共9页
  • 作者

    Qiang Xiaoke; Xu Xinwen; Zhao Hui; Fu Chaofeng;

  • 作者单位

    Chinese Acad Sci, Inst Earth Environm, State Key Lab Loess & Quaternary Geol, Xian 710061, Shaanxi, Peoples R China;

    Chinese Acad Sci, Inst Earth Environm, State Key Lab Loess & Quaternary Geol, Xian 710061, Shaanxi, Peoples R China;

    Shaanxi Normal Univ, Dept Geog, Xian 710062, Shaanxi, Peoples R China;

    Changan Univ, Minist Educ China, Key Lab Western Mineral Resources & Geol Engn, Xian 710054, Shaanxi, Peoples R China;

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  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

    Lacustrine sediments; Rock magnetism; Greigite formation; Sedimentary environments;

    机译：Lacustrine沉积物;岩石磁性;Grigite形成;沉积环境;

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