5 Recent Advances in the Studies on the Origin of Magmatic and Hydrothermal Ore Deposits
Thursday, 2 May 2013
10:00 AM - 12:00 PM
Room 2040
CO2 CYCLING IN THE DEEP EARTH
Paper number: 5-5
Program: Theme Sessions
Time: 11:20 AM – 11:40 AM
Authors
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John G. ComptonIndiana University South Bend, South Bend, IN
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Maggie HasanNorthern Illinois University, DeKalb, IL
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Mark FrankNorthern Illinois University, DeKalb, IL
Abstract
We have used laser-heated Diamond Anvil Cells (LDAC's) coupled with synchrotron X-ray diffraction to make in situ observations of magnesite formation from CO2 plus simple oxide (i.e., MgO) and silicate (e.g., Mg2SiO4) components at mantle pressures and temperatures. Previously we demonstrated that the reaction MgO + CO2 = MgCO3 proceeds readily at pressures up to 40 GPa and temperatures around 1,800 K, despite the existence of relatively dense high-pressure CO2 polymorphs. For our most recent study, we have incorporated the magnesium end-member of olivine to consider the reaction CO2 + Mg2SiO4 = MgSiO3 + MgCO3, as studied extensively at low pressures (i.e., less than 4 GPa) by previous workers (e.g., Newton and Sharp, 1975). As expected, higher temperatures favor the forsterite side of the reaction, especially at low pressures. In this presentation, we will discuss our extension of this system to pressures greater than 20 GPa and the role played by high-pressure polymorphism in CO2 and the magnesium silicates.