The aluminum-in-olivine thermometer for mantle peridotites - Experimental versus empirical calibration and potential applications

This study provides an experimental calibration of the empirical Al-in-olivine thermometer for mantle peridotites proposed by De Hoog et al. (2010). We report Al concentrations measured by secondary ion mass spectrometry (SIMS) in olivines produced in the original high-pressure, high-temperature, four-phase lherzolite experiments by Brey et al. (1990). These reversed experiments were used for the calibration of the two-pyroxene thermometer and Al-in-orthopyroxene barometer by Brey and Kohler (1990). The experimental conditions of the runs investigated here range from 28 to 60 kbar and 1000 to 1300 degrees C. Olivine compositions from this range of experiments have Al concentrations that are consistent, within analytical uncertainties, with those predicted by the empirical calibration of the Al-in-olivine thermometer for mantle peridotites. Fitting the experimental data to a thermometer equation, using the least squares method, results in the expression: T[degrees C] = (11245 + 46.0 * P[kbar])/(13.68- In (Al[ppm])-273. This version of the Al-in-olivine thermometer appears to be applicable to garnet peridotites (lherzolites and harzburgites) well outside the range of experimental conditions investigated here. However, the thermometer is not applicable to spinel-bearing peridotites. We provide new trace element criteria to distinguish between olivine from garnet-, garnet-spinel-, and spinel-facies peridotites. The estimated accuracy of the thermometer is +/- 20 degrees C. Thus, the thermometer could serve as a useful tool in settings where two-pyroxene thermometry cannot be applied, such as garnet harzburgites and single inclusions in diamond. (C) 2016 Elsevier B.V. All rights reserved.