Methane, water, quartz, siderite, hematite, and possibly greenalite and sodium hydroxide in a BARB3 drilled sample of the 3.4 Ga Buck ReefChert. Crustal anoxic alkaline high subcritical water at the origin of the observed ferric minerals, methane and disordered graphitic carbon, and of plausible molecules of life

Abstract

Abstract Molecular components of the 3.4 Ga Buck Reef Chert, Barberton Greenstone Belt, South Africa, are reported following spectroscopic results. Earlier hypotheses for their formation and for the synthesis of molecules of life prior to the emergence of life are confirmed. The observations are conducted with four Raman spectrometers located in Johannesburg-South Africa, Cergy-Paris Université-France, Orléans-France and Lille-France. The studied sample is a banded iron section from the BARB3 drill core. Siderite, hematite and possibly greenalite are observed in the quartz matrix. Water, methane, and possibly greenalite or sodium hydroxide, are observed in the quartz cavities. Disordered graphitic carbon appears covering homogenously the section. Its formation is proposed as a deposition from an anoxic methane-rich fluid. A comparison with Raman spectra of graphitic carbon of various origins, suggests a possible direct relation between the Raman profiles and the amount of oxygen contained inside the disordered graphitic matter. The methane may be a remnant of the Archean methane-rich water. In the continuity of the theoretical earlier articles, interactions between high subcritical alkaline anoxic water and the ferrous silicates fayalite and/or ferrosilite are proposed to be at the origin of the experimentally observed ferric minerals and methane. Molecular H2 is emitted during the oxidation of Fe2+ into Fe3+ and induces the transformation of CO2 into CH4. The constructions of the Neoproterozoic and Archean Banded Iron Formations are proposed by ejection of the minerals that formed inside the Earth crust, during processes involving subduction events or not.