[SGC52-P06] Geochemistry of olivine melt inclusions in Pitcairn Island basalts: A multiple-instrument approach
Most of the olivine-hosted melt inclusions contain microcrystals due to slow cooling after emplacement of the host lavas. In the preliminary study, we found that measured element concentrations were blurred by the microcrystals. Therefore, we homogenized the melt inclusions by a heating and quenching method. Homogenization experiment was performed in a CO2 + H2 atmosphere using an electric furnace. For the first step, liquidus temperature of the melt inclusions was explored by altering the furnace temperature at every 25 °C between 1100 °C and 1350 °C. We found that the liquidus temperature was between 1150 °C and 1175 °C. All the olivines were then heated just above the liquidus temperature at 1150 °C or 1175 °C for 10 minutes and quenched. Previous studies showed that H2O may be diffused out from a melt inclusion through host olivine during homogenization. In order to assess the effect on H2O diffusion, we also heated naturally homogeneous melt inclusions in a pyroclastic rock and compared H2O concentrations before and after heating. In this presentation, effects of homogenization on volatile compositions will be discussed. After corrections for the effects of post-entrapment crystallization, concentrations of the volatile elements together with the major and trace elements, and Pb isotopes in the melt inclusions are used to explore volatile contents in the source mantle of the Pitcairn OIBs.