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Geobiotropy on Early Earth and in the Rocky Universe

It is currently proposed that life existed 3.5-3.8 Ga ago. However, the origin of the microorganisms is not yet explained. This presentation shows an anoxic path of formation of ferric minerals together with production of H2, when ferrous rocks interact with water at 300°-350°C, 10-25 MPa, 700-600 kg/m3, and at very alkaline pH, 11-14. The released H2 can interact with the dissolved CO2 and lead to CO that is known to be the preferred simple molecule for prebiotic chemistry reactions. Fluid inclusions that form during the hydrolysis can thus contain H2, CO, H2O. When N2 is present, this assemblage of molecules is known in the laboratory to lead to organic molecules of life. Therefore, from the rocks may form the molecules that are required for the emergence of life, process that I represented in 2016, by the concept of geobiotropy. This conclusion arises from the analysis of the redox potential E of the electrochemical system Fe-high subcritical water, in the high pH range. The induced precise values of T, P, density, pH, can be applied to the anoxic geological world, such as Early Earth and Enceladus, the icy satellite of Saturn. A Raman observation of a sample from the 3.4 Ga Buck Reef Chert, Barberton Greenstone Belt, South Africa, shows quartz, siderite, hematite and the peak of water inside a 1 μm fluid inclusion in quartz. Other lines are under study. The theoretical predictions on anoxic ferrous iron oxidation will be tested with laboratory experiments that are currently under preparation.


Marie-Paule, Renelde Bassez
University of Strasbourg, France, France
GeoKarlsruhe 2021