Stability of forsterite + CO2 and its bearing on the role of CO2 in the mantle |
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| Authors: | RC Newton WE Sharp |
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| Institution: | Department of the Geophysical Sciences, University of Chicago, Chicago, Ill. USA;Geology Department, University of South Carolina, Columbia, S.C. USA |
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| Abstract: | An experimental determination of the reaction MgCO3 + MgSiO3 = Mg2SiO4 + CO2 between 20 and 40 kbars and in the range 1000–1500°C yields an average pressure effect on the equilibrium of 44 bars/°C. This result shows that the assemblage forsterite and carbon dioxide is not stable under most pressure and temperature conditions expected in the upper mantle. Hypotheses requiring the presence of free CO2 in the low-velocity zone, CO2 as a drive mechanism for kimberlite emplacement, or action of a free CO2 phase in ultramafic rocks may need considerable revision. |
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