Decarbonation reaction of magnesite in subducting slabs at the lower mantle
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High-pressure and temperature experiments (28–62 GPa, and 1,490–2,000 K, corresponding to approximately 770–1,500 km depth in the mantle) have been conducted on a MgCO3 + SiO2 mixture using a laser-heated diamond anvil cell combined with analytical transmission electron microscope observation of the product phases to constrain the fate of carbonates carried on the subducting basalt into the lower mantle. At these conditions, the decarbonation reaction MgCO3 (magnesite) + SiO2 (stishovite) → MgSiO3 (perovskite) + CO2 (solid) has been recognized. This indicates that above reaction takes place as a candidate for decarbonation of the carbonated subducting mid ocean ridge basalts in the Earth’s lower mantle.
KeywordsHigh-pressure solid CO2 Carbonate Slab Diamond
This research was supported by a 21st Century Center of Excellence (COE) Program on “Neo-Science of Natural History” (Program Leader: Hisatake Okada) at Hokkaido University financed by the Ministry of Education, Culture, Sports, Science and Technology, Japan. Nagai was supported by Grant-in-Aid for Research (No. 18340167) from the Ministry of Education, Science, and Culture of Japan. The sample of magnesite is a specimen of the National Science Museum, Tokyo with the registration number of NSM-MF10684. We thank two anonymous reviewers for their critical and constructive comments on this manuscript.
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