183 / 2023-04-15 15:12:02

Geochemical Process of Fluorine Incorporation into Calcite at Earth’s Surface

Fluorine,calcite,high temperature and high pressure

高压物理与材料科学 > 高压地球科学-海报

Being a component of volcanic gases and a major constituent of oceans, fluorine has been suggested to be a promising candidate for reconstructing paleoceanographic parameters. Fluorine is present in rock-forming minerals such as fluorite and fluorapatite and the only form of fluorine occurring in natural waters is fluoride anion (F^-). The primary sink of fluorine is thought to be via doping in calcium carbonate in modern oceans, which may be subsequently transfer to the deep solid Earth by subduction processes. High concentrations of fluorine erupted via volcanic emission have also suggested a fluorine reservoir in the deep solid Earth. The abundance of calcium carbonate minerals in marine sediments and their high fluorine content also make fluorine a promising candidate for reconstructing paleoceanographic parameters. However, the processes of F-incorporation into carbonates are not yet fully understood though pervious work by Feng et al. (2021) has used density functional theory (DFT) calculations to analyze the incorporation mechanisms of fluorine into crystalline calcium carbonates and suggested several favorable forms of halogen substitution theoretically. We have studied F-incorporation into calcite experimentally at high pressure. Our findings have significant implications for understanding the geochemical processes involving fluorine incorporation into calcite at the Earth's surface, which is not only important to understand geochemical cycling, but also key to the measurement of climate and environmental change in the oceans.

 

1. X Feng, Z Steiner, S A T Redfern (2021) Fluorine incorporation into calcite, aragonite and vaterite CaCO₃: Computational chemistry insights and geochemistry implications. Geochimica Cosmochimica Acta, DOI: 10.1016/j.gca.2021.05.029