Redox-controlled mechanisms of C and H isotope fractionation between silicate melt and COH fluid in the Earth’s interior

Abstract

The behavior of COH fluids, their isotopes (hydrogen and carbon), and their interaction with magmatic liquids are at the core of understanding formation and evolution of the Earth. Experimental data are needed to aid our understanding of how COH volatiles affect rock-forming processes in the Earth's interior. Here, I present a review of experimental data on structure of fluids and melts and an assessment of how structural factors govern hydrogen and carbon isotope partitioning within and between melts and fluids as a function of redox conditions, temperature, and pressure. The solubility of individual COH components in silicate melts can differ by several orders of magnitude and ranges from several hundred ppm to several wt%. Silicate solubility in fluid can reach several molecular at mantle temperatures and pressures. Different solubility of oxidized and reduced C-bearing species in melts reflects different solution equilibria. These equilibria are 2CH 4

Hydration and Dehydration in Earth's Interior

“…Many hydrous minerals such as chlorite, amphibole, and serpentine are known to exist in the crust and slabs descending into the upper mantle. Dehydration of these minerals as the slab descends produces fluids that transport volatile and large iron lithophile elements from the slab to the overlying mantle (e.g., Mysen 2018Mysen , 2019 and so create volcanism in island arcs and earthquakes in subduction zones (e.g., Hacker et al 2003).…”

Diamond formation in an electric field under deep Earth conditions

“…The mechanism(s) by which an electric field induces carbon generation and diamond crystallization can be reconstructed on the basis of the obtained experimental results and published data. As mantle carbonate and carbonate-silicate melts contain anionic СО 3 2− groups ( 42 , 43 ), the process of carbon reduction under high-pressure high-temperature (HPHT) conditions is likely similar to electrolytic deposition of carbon from carbonate melts implemented at ambient pressure ( 44 , 45 ). For the dolomite composition, the reactions are as follows.…”