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首页> 外文期刊>International Journal of Earth Sciences >Influence of volcanism on the development of black shales in the Chang 7 Member of Yanchang Formation in the Ordos Basin
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Influence of volcanism on the development of black shales in the Chang 7 Member of Yanchang Formation in the Ordos Basin

机译：Valcanism对鄂尔多斯盆地延长组建中昌7次成员的黑宝龙发展的影响

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摘要

In geological history, volcanism is closely related to the deposition of many black shales. However, the specific mechanism between volcanism and the deposition of black shales is still unclear. The black shales developed in the Chang 7 Member of the Yanchang Formation in the Ordos Basin are considered the most important hydrocarbon source rocks in Central China. The shales are deposited by frequent volcanic activities and preserved by extremely rich volcanic ash layers, making them an excellent example when investigating the influence of volcanism on the deposition of black shales. In this paper, petrographic, mineralogical, and geochemical analyses of three typical tuff and black shale segments of the Chang 7 Member were carried out. The productivity indicators [total organic carbon (TOC), P/Al, Ni/Al, and Cu/Al], redox indicators (V/Al, Mo/Al, U/Al and U/Th), and clastic influx indicators (Ti/Al and Sigma REE) of the shales basically increased together in the longitudinal direction, and a relatively good positive correlation existed between P/Al, Ni/Al, Cu/Al, V/Al, Mo/Al, U/Al, U/Th, Ti/Al, Sigma REE, and TOC. This finding indicated that the development of the Chang 7 black shales is the result of a combination of high primary productivity, anoxic conditions, and increased clastic influx. Considering that increased clastic influx may dilute organic matter, many phosphate nodules represented high productivity above the volcanic ash layers, and anoxic conditions are likely to be the result of a large amount of organic matter degradation indicated by the covariations of TOC versus P/Al and TOC versus Ba/Al. Therefore, the Chang 7 black shales in this study may be mainly controlled by the increased primary productivity. In addition, compared with the Weathering Index of Parker of background shales (not the contact clip or tuff layer), that of the black shales was significantly reduced after tuff deposition. On the contrary, the clastic influx indicators, redox indicators, productivity indicators of black shales significantly increased. This finding suggested that a series of environmental effects, such as enhanced weathering of terrestrial sources, increased clastic influx, anoxic water, and productivity bloom, was likely caused by volcanic activity. Considering that hydrothermal activity at the same time as volcanism may not cause productivity bloom, the nutrients (P/Al and Fe/Al) of the Chang 7 tuffs were significantly depleted, and the total sulfur content of black shales was much higher than that in ordinary freshwater sedimentation. Therefore, this paper reviewed and proposed the volcanism hypothesis model of the Chang 7 black shales. Volcanism generates large amounts of SO2 and volcanic ash. SO2 forms large areas of acid rain and accelerates terrigenous weathering with an increase in the lake land-based sources of debris and nutrient supply, while volcanic ash is decomposed and releases nutrients. These phenomena lead to biological productivity bloom and massive accumulation of organic matter, which in turn results in lake water anoxia and the eventual formation of black shales.
机译：在地质历史中，火山主义与许多黑色神出士的沉积密切相关。然而，火山中的特定机制和黑色神座的沉积仍然不清楚。在鄂尔多斯盆地延长地区延长组建中发展的黑色罗斯被认为是中国中部最重要的碳氢化合物源岩。通过频繁的火山活动沉积了罗斯人，并通过极其富含火山灰层保存，使他们在调查火山主义对黑宝龙沉积的影响时，使其成为一个优秀的例子。在本文中，进行了三种典型凝灰岩和常齿7个成员黑色页岩区段的岩体，矿物学和地球化学分析。生产率指示剂[总有机碳（TOC），P / Al，Ni / Al和Cu / Al]，氧化还原指标（v / Al，Mo / Al，U / Al和U / Th），以及碎片涌入指示灯（ Shales的Ti / Al和Sigma Ree基本上在纵向方向上一起增加，并且在P / Al，Ni / Al，Cu / Al，V / Al，Mo / Al，U / Al之间存在相对良好的正相关， U / TH，TI / AL，SIGMA REE和TOC。这一发现表明，Chang 7 Black Hales的发展是高初级生产率，缺氧条件和增加的碎片流入的组合的结果。考虑到增加碎片流量可以稀释有机物，许多磷酸盐结节在火山灰层上方表示高生产率，并且缺氧条件可能是TOC与P / Al的共变量表示的大量有机质降解的结果。 toc与ba / al。因此，该研究中的Chang 7黑色Shales可以主要通过增加的初级生产率来控制。此外，与背景Haales帕克（不是接触夹或凝灰岩层）的风化指数相比，在凝固沉积后，黑色的Haales的避难所显着降低。相反，碎屑涌入指示灯，氧化还原指标，黑色士叶的生产率指标显着增加。这一发现表明，一系列环境影响，如陆地来源的耐候增强，增加碎片流入，缺氧水和生产率绽放，可能是由火山活度引起的。考虑到水热活性与火山的同时可能不会引起生产率绽放，常7根茎的营养物质（P / Al和Fe / Al）显着耗尽，黑色HALES的总硫含量远高于此普通淡水沉降。因此，本文审查并提出了常7黑色罗斯的火山主义假设模型。火山产生大量的SO2和火山灰。 SO2形成大面积的酸雨，并随着南陆陆地碎片和营养供应的增加，加速危及风化，而火山灰分解并释放营养素。这些现象导致生物生产率绽放和大量积累的有机物，这反过来导致水缺氧和最终形成黑色页岩。

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  • 来源
    《International Journal of Earth Sciences》 |2021年第6期|1939-1960|共22页
  • 作者

    Wang Cheng; Wang Qinxian; Chen Guojun; Chen Duofu;

  • 作者单位

    Changan Univ Sch Sci Xian 710064 Shaanxi Peoples R China|Chinese Acad Sci State Key Lab Organ Geochem Guangzhou Inst Geochem Guangzhou 510640 Peoples R China;

    Shanghai Ocean Univ Shanghai Engn Res Ctr Hadal Sci & Technol Coll Marine Sci Shanghai 201306 Peoples R China|Chinese Acad Sci State Key Lab Organ Geochem Guangzhou Inst Geochem Guangzhou 510640 Peoples R China;

    Chinese Acad Sci Key Lab Petr Resources Res Lanzhou 730000 Peoples R China;

    Shanghai Ocean Univ Shanghai Engn Res Ctr Hadal Sci & Technol Coll Marine Sci Shanghai 201306 Peoples R China|Chinese Acad Sci State Key Lab Organ Geochem Guangzhou Inst Geochem Guangzhou 510640 Peoples R China;

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

    Volcanism; Hydrothermal activity; Black shale; Clastic influx; Primary productivity; Redox conditions; Upper triassic; Ordos basin;

    机译：山脉;水热活动;黑色页岩;碎片流入;初级生产力;氧化还原条件;上三叠纪;鄂尔多斯盆地;

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