南华盆地成冰纪氧化还原环境和有机碳堆积机制： 大塘坡组沉积物铁元素，硫、碳和氧...

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南华盆地成冰纪氧化还原环境和有机碳堆积机制：

大塘坡组沉积物铁元素，硫、碳和氧同位素分析

Advances in Geo-Energy Research, 2019, 3(1): 67-75

原文网址: http://www.astp-agr.com/index.php/Index/Index/detail?id=97

      新远古代全球冰川覆盖、氧气含量升高和真核生物繁盛是地球早期演化的标志性事件。然而，这些事件之间的耦合关系尚未被探知。成冰系大塘坡组黑色页岩含有丰富的有机质，这些有机质的形成和保存能够反映其形成时所处的氧化还原环境，因而成为研究有机质成因和地球早期环境条件的良好对象。本研究提供了华南地区大塘坡剖面新的沉积岩地球化学证据，包括铁元素组成、有机质含量（TOC）、黄铁矿硫同位素、和碳、氧同位素等。分析结果显示，在成冰纪早期，海洋中存在大量的营养物质，例如磷酸盐含量较高，为形成高含量的有机碳奠定了基础。这些营养物质可能与间冰期间的火山喷发活动有关。黑色页岩中的铁元素和硫同位素分析显示，大塘坡组下部沉积物形成于贫氧、还原环境的深水环境。贫氧的条件为有机碳的保存提供了良好的条件。但是，氧化铝（Al2O3）和有机质含量具有反相关关系，说明陆源碎屑物质的输入对有机质有稀释作用。

Redox condition and organic carbon accumulation mechanism in the Cryogenian Nanhua basin, south China: Insights from iron chemistry and sulfur, carbon, oxygen isotopes of the Datangpo Formation

Chaoyong Wang, Guanzhong Shi

(Published: 2018-11-07)

CorrespondingAuthor and Email:  Guanzhong Shi, cugshi@163.com; ORCID: https://orcid.org/0000-0003-2957-6647

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Citation: Wang, C., Shi, G. Redox condition and organic carbon accumulation mechanism in the Cryogenian Nanhua basin, south China: Insights from iron chemistry and sulfur, carbon, oxygen isotopes of the Datangpo Formation. Advances in Geo-Energy Research, 2019, 3(1): 67-75, doi: 10.26804/ager.2019.01.05.

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ArticleType: Original article

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Abstract：

         Global glaciation, oxidation event and eukaryotic expansion and diversification in the Neoproterozoic period are marked events that characterize the early evolution of the Earth, but how the interactions occurred among these events is not well understood. The organic matters preserved in the black shales of the Datangpo Formation (Cryogenian period) are sensitive to redox conditions, and thus its accumulation and preservation offer beneficial clues to unravel the early evolutional history of the Earth. This study presents new chemostratigraphic data of iron component, TOC content, sulfur isotope of pyrite, carbon and oxygen isotopes of carbonaceous shale of the Datangpo Formation (Cryogenian period) in the Datangpo section, South China. The analyzed results imply abundant nutrients existing in the ocean in the Early Cryogenian. The nutrients, such as phosphorus, resulting from neighbor volcanic eruptions, provided nutrients that enabled microbes to flourish during the Cryogenian interglacial gap. Iron components and sulfur isotopes indicated anoxic, euxinic deep water environments for the black shales in the lower portion of the Datangpo Formation. The anoxic setting was good for the preservation of organic matter, but terrigenous materials inputs, as revealed by the high Al2O3 contents, diluted the organic carbon content (TOC).

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Keywords: Cryogenian period, Datangpo Formation, organic matter, paleoenviroment.