Title
Recycled calcium carbonate is an efficient oxidation agent under deep upper mantle conditions
Author
Renbiao Tao
Year
2021
Journal
Communications earth & environment
Abstract
Observations of high ferric iron content in diamond garnet inclusions and mantle plume melts suggest a highly heterogeneous distribution of ferric iron in the mantle. Recycling of oxidized materials such as carbonates from Earth’s surface by subduction could explain the observed variations. Here we present high-pressure high-temperature multi-anvil experiments to determine the redox reactions between calcium-, magnesium-, or iron-carbonate and ferrous iron-bearing silicate mineral (garnet or fayalite) at conditions representative of subduction zones with intermediate thermal structures. We show that both garnet and fayalite can be oxidized to ferric iron-rich garnets accompanied by reduction of calcium carbonate to form graphite. The ferric iron content in the synthetic garnets increases with increasing pressure, and is correlated with the Ca content in the garnets. We suggest that recycled sedimentary calcium carbonate could influence the evolution of the mantle oxidation state by efficiently increasing the ferric iron content in the deep upper mantle.
Full Article
Instrument
NRS-3100
Keywords
Calcium, Oxidation