University of Strasbourg, Jean-Marie Lehn Foundation, Strasbourg, France.
Orig Life Evol Biosph. 2023 Jun;53(1-2):1-41. doi: 10.1007/s11084-023-09638-x. Epub 2023 Aug 16.
The present article reports Raman spectroscopic observations of siderite, hematite, disordered graphitic carbon and possibly greenalite inside the quartz matrix of a banded iron sample from the BARB3 core drilled inside the 3.4 Ga Buck Reef Chert of the Barberton Greenstone Belt in South Africa. The article also reports Raman spectroscopic observations of quartz cavities, concluding in the presence of water, methane and sodium hydroxide at high concentration leading to pH ~ 15 inside the inclusion, suggesting an Archean water which was strongly basic. Fe-greenalite may also be present inside the inclusion. The possible role of anoxic alkaline high subcritical water in the formation of ferric minerals and the CO required for the synthesis of molecules of biological interest has been demonstrated theoretically since 2013 and summarized in the concept of Geobiotropy. The present article experimentally confirms the importance of considering water in its anoxic strongly alkaline high subcritical domain for the formation of quartz, hematite, Fe-greenalite, methane and disordered graphitic carbon. Methane is proposed to form locally when the carbon dioxide that is dissolved in the Archean anoxic alkaline high subcritical water, interacts with the molecular hydrogen that is emitted during the anoxic alkaline oxidation of ferrous silicates. The carbon matter is proposed to form as deposition from the anoxic methane-rich fluid. A detailed study of carbon matter from diverse origins is presented in a supplementary file. The study shows that the BARB3_23B sample has been submitted to ~ 335 °C, a temperature of the high subcritical domain, and that the graphitic structure contains very low amounts of oxygen and no hydroxyl functional groups. The importance of considering the structure of water is applied to the constructions of the Neoproterozoic and Archean banded iron formations. It is proposed that their minerals are produced inside chemical reaction chambers containing ferrous silicates, and ejected from the Earth's oceanic crust or upper mantle, during processes involving subduction events or not.
本文报道了拉曼光谱观察到的菱铁矿、赤铁矿、无定形石墨碳和可能的绿纤石，它们存在于南非巴伯顿绿岩带 3.4Ga 巴克燧石中的 BARB3 岩芯中带铁样品的石英基质内。本文还报道了石英腔的拉曼光谱观察结果，得出的结论是包裹体内部存在高浓度的水、甲烷和氢氧化钠，导致包裹体内部的 pH 值约为 15，表明太古宙水呈强碱性。包裹体内部也可能存在 Fe-绿纤石。自 2013 年以来，理论上已经证明了缺氧碱性高亚临界水在铁矿物形成和合成生物感兴趣分子所需的 CO 中的作用，并在地球生物化学假说中进行了总结。本文通过实验证实了考虑缺氧强碱性高亚临界水在石英、赤铁矿、Fe-绿纤石、甲烷和无定形石墨碳形成中的重要性。提出当溶解在太古缺氧碱性高亚临界水中的二氧化碳与亚铁硅酸盐缺氧碱性氧化过程中释放的分子氢相互作用时，甲烷会在局部形成。提出碳质物质是从缺氧富甲烷流体中沉淀形成的。在补充文件中提出了对来自不同来源的碳质物质的详细研究。该研究表明，BARB3_23B 样品经历了约 335°C 的温度，这是高亚临界域的温度，并且石墨结构中含有非常低量的氧和没有羟基官能团。考虑水的结构的重要性适用于新元古代和太古宙条带状铁建造的构造。提出它们的矿物是在含有亚铁硅酸盐的化学反应室内生成的，并在俯冲事件或不涉及俯冲事件的过程中从地球的海洋地壳或上地幔中喷出。
