Abiotic synthesis during the interaction of ferrous chloride-rich silicic fluids with marble under high-grade metamorphic conditions.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 40875805.
- Also identified by DOI 10.1073/pnas.2423043122 and PMC identifier 12415227.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Ferrous chloride-rich silicic fluid and melt infiltration led to the decarbonation of dolomitic marble in the Chinese Sulu ultrahigh-pressure metamorphic terrain under temperatures ranging from 670 to 800 °C, pressures from the aragonite + albite to calcite stability fields and the oxygen fugacities between the hematite-magnetite and pyrite-pyrrhotite-magnetite buffers, resulting in the formation of olivine marble and diopsidite. The inclusions in zircons trapped during the decarbonation process suggest that the H<sub>2</sub>-producing reaction 3FeCl<sub>2</sub> (aq) + 3CaCO<sub>3</sub> + H<sub>2</sub>O = Fe<sub>3</sub>O<sub>4</sub> (magnetite) + 3CaCl<sub>2</sub> (aq) + 3CO<sub>2</sub> + H<sub>2</sub> occurred and that it induced magnetite-catalyzed Fischer-Tropsch-type synthesis, as indicated by the presence of whewellite, disordered carbonaceous material, CH<sub>4</sub>, and CO in the inclusions. The results of this study highlight the role of aqueous Fe in generating H<sub>2</sub> and magnetite and have far-reaching implications for carbon speciation and solubility in deep fluids and for endogenic abiotic synthesis, which may be pivotal in the prebiotic occurrence of organic compounds on Earth.