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首页> 外文期刊>Comptes rendus >The role of the early diagenetic dolomitic concretions in the preservation of the 2.1-Ga paleoenvironmental signal: The Paleoproterozoic of the Franceville Basin, Gabon
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The role of the early diagenetic dolomitic concretions in the preservation of the 2.1-Ga paleoenvironmental signal: The Paleoproterozoic of the Franceville Basin, Gabon

机译：早期成岩的白云岩沉积物在2.1-Ga古环境信号的保存中的作用：加蓬弗朗斯维尔盆地的古元古代

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摘要

Dolomite concretions from Paleoproterozoic organic-rich sediments of the Franceville Basin (Francevillian) in southeastern Gabon are studied. These concretions, belonging to one of the rare well-preserved Proterozoic sediments in the world, are mainly observed in the shaly levels of the Francevillian B1 Formation. The concretions often show a central pyrite-rich layer. The decrease in the carbonate content from the centre to the edges, and the carbon isotopic signal of carbonate within the concretions indicate a concentric growth of the concretions prior to compaction and precipitation of carbonate associated with the degradation of organic matter during early diagenesis. From its geochemical signature and texture, dolomite was not recrystallized. Moreover, the interior of the concretions shows well-preserved accumulations of microbial mats. These concretions thus appear to represent an exceptional record of the biogeochemical signature of the crucial period when the oxygen rose for the first time in Earth’s atmosphere. If their rare- earth element pattern does not seem to reflect that of Paleoproterozoic seawater, they appear as potential tools for estimating the original oceanic temperature in surface sediments.
机译：研究了加蓬东南部弗朗斯维尔盆地（弗朗西斯维利安）古元古代有机质富集沉积物中的白云岩。这些凝结物属于世界上稀有的，保存完好的元古代沉积物之一，主要在弗朗西维利亚B1组页岩层中观察到。这些凝结物经常显示出富集黄铁矿的中央层。碳酸盐含量从中心到边缘的减少，以及固结物中碳酸盐的碳同位素信号表明，在压实和沉淀之前，固结物是同心生长的，这与早期成岩过程中有机物的降解有关。从其地球化学特征和质地来看，白云石并未重结晶。而且，混凝土的内部显示出保存完好的微生物垫。因此，这些凝结物似乎代表了关键时期生物氧化学特征的特殊记录，当时氧气在地球大气中首次上升。如果它们的稀土元素形态似乎不能反映古元古代海水的形态，那么它们就可以作为估算地表沉积物中原始海洋温度的潜在工具。

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  • 来源
    《Comptes rendus》 |2016年第8期|609-618|共10页
  • 作者

    Nathaelle Onanga Mavotchy; Abderrazak El Albani; Alain Trentesaux; Claude Fontaine; Anne-Catherine Pierson-Wickmann; Philippe Boulvais; Armelle Riboulleau; Lauriss Ngombi Pemba; Florent Pambo; Francois Gauthier-Lafaye;

  • 作者单位

    Institut de chimie des milieux et mate´riaux de Poitiers (IC2MP), UMR 7285 CNRS–INSU–INC, universite´ de Poitiers, 86000 Poitiers, France;

    Institut de chimie des milieux et mate´riaux de Poitiers (IC2MP), UMR 7285 CNRS–INSU–INC, universite´ de Poitiers, 86000 Poitiers, France;

    Laboratoire d’oce´anologie et de ge´osciences (LOG), UMR 8187 CNRS, universite´ de Lille, 59655 Villeneuve d’Ascq cedex, France;

    Institut de chimie des milieux et mate´riaux de Poitiers (IC2MP), UMR 7285 CNRS–INSU–INC, universite´ de Poitiers, 86000 Poitiers, France;

    OSUR, laboratoire de ge´osciences, UMR 6118 CNRS, universite´ de Rennes-1, 35000 Rennes, France;

    OSUR, laboratoire de ge´osciences, UMR 6118 CNRS, universite´ de Rennes-1, 35000 Rennes, France;

    Laboratoire d’oce´anologie et de ge´osciences (LOG), UMR 8187 CNRS, universite´ de Lille, 59655 Villeneuve d’Ascq cedex, France;

    Universite´ des sciences et techniques de Masuku, Franceville, Gabon;

    Socie´te´ COMILOG, groupe ERAMET, Moanda, Gabon;

    Laboratoire d’hydrologie et de ge´ochimie de Strasbourg, UMR 7517 CNRS, 67084 Strasbourg, France;

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  • 正文语种 eng
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  • 关键词

    Concretions; Paleoproterozoic; Francevillian; Palaeoenvironment; Gabon;

    机译：结石;古元古代Francevillian;古环境加蓬;

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