Abstract:
The basic igneous complex of Mayurbhanj is a differentiated suite composed of harzburgite, gabbronorite, leucogabbronorite and anorthosite. EPMA of the coexisting oxides in the rock samples reveal that magnetite-ilmenite have re-equilibrated between 770 degrees C and less than 500 degrees C and fo(2) of 10(-16) to less than 10(-25). Ilmenite granules and thick lamellae have identical composition and approach pure FeTiO3. The chromian spinel-olivine geothermometry in harzburgite suggests a temperature of 1263 degrees C. The pyroxene geothermometric data in gabbroic rocks indicate equilibration temperature range of 819 degrees C to 1071 degrees C. The thermometric data indicate that the magnetite and ilmenite equilibrated at lower temperature than the coexisting pyroxenes for a particular rock sample.