Oxygen isotope fractionation between calcite and forsterite formed via reaction from dolomite and tremolite at 680°C
Zheng, Yong-Fei; Metz, Paul; Satir, Muharrem; Sharp, Zachary D.
European Journal of Mineralogy Volume 6 Number 2 (1994), p. 179 - 186
published: Mar 31, 1994
manuscript accepted: Nov 22, 1993
manuscript received: Jun 15, 1993
ArtNo. ESP147050602002, Price: 29.00 €
Abstract The partitioning of oxygen isotopes between calcite and forsterite at 680°C and 500 MPa has been directly measured using the reaction of dolomite plus tremolite to produce calcite, forsterite, CO2 and H2O. The results give a mean fractionation of 3.91 ± 0.25 %o between calcite and forsterite, which is interpreted to represent equilibrium fractionation. Carbon isotope equilibration is also achieved between CO2 and calcite of the reaction product, with a mean fractionation of 3.36 ± 0.16 %o at 680°C. Apparently, oxygen and carbon isotope equilibration can be obtained between the product phases of a completed reaction. Mineral reactions usually involve the breakdown and formation of chemical bonds and thus large changes in free energy. This is probably a fundamental cause for the isotopic equilibration among the product phases. Therefore, reactions can be used as a direct approach to calibrate isotopic fractionation between product phases.