Effect of NaCrSi2O6 component on Lindsley’s pyroxene thermometer: An evaluation based on strongly metamorphosed LL chondrites.

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Nakamuta, Y., Urata, K., Shibata, Y. and Kuwahara, Y.

Meteoritics & Planetary Science. doi: 10.1111/maps.12808

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“In Lindsley’s thermometry, a revised sequence of calculation of components is proposed for clinopyroxene, in which kosmochlor component is added. Temperatures obtained for the components calculated by the revised method are about 50 °C lower than those obtained for the components calculated by the Lindsley’s original method and agree well with temperatures obtained from orthopyroxenes. Ca-partitioning between clino- and orthopyroxenes is then thought to be equilibrated in types 5 to 7 ordinary chondrites. The temperatures for Tuxtuac (LL5), Dhurmsala (LL6), NWA 2092 (LL6/7), and Dho 011 (LL7) are 767–793°, 818–835°, 872–892°, and 917–936°C, respectively, suggesting that chondrites of higher petrographic types show higher equilibrium temperatures of pyroxenes. The regression equations which relate temperature and Wo and Fs contents in the temperature-contoured pyroxene quadrilateral of 1 atm of Lindsley (1983) are also determined by the least squares method. It is possible to reproduce temperatures with an error less than 20 °C (2SE) using the regression equations.”

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