[SMP38-P05] Metamorphic temperature analysis of H chondrites using revised Lindsley’s pyroxene thermometer
Keywords:H chondrite, Lindsley's pyroxene thermometer, Metamorphic temperature, Petrologic type
In this study, we have attempted to estimate the metamorphic temperatures of H chondrites (type 5 to 7) using the Lindsley’s pyroxene thermometer revised by Nakamuta et al (2017). Here we report the results of the estimation.
The chondrite samples used were three H chondrite with different metamorphic degrees; Faucett(H5), Mluga (north)(H6), and NWA7875(H7). Polished thin sections of the three H chondrites were prepared and observed using transmitted and reflecting light microscopes. Then, chemical compositions of pyroxenes, olivines, and plagioclases in the three H chondrites were analyzed by an EPMA, JEOL JXA-8530F.
For Mluga (north)(H6), the mean temperature of clinopyroxenes (72 points) calculated by the revised method was 799 ± 48°C and that of orthopyroxenes (76 points) was 804 ± 37°C. The difference in temperature between the two pyroxenes was less than 5°C much lower than that from the original method. This suggests that the revised Lindsley’s pyroxene thermometer can be effectively used even in H chondrite meteorites. On the other hand, the temperatures of clinopyroxene for Faucett(H5) tended to vary more widely than Mluga(north)(H6).