GEOTHERMOMETRIC AND OXYGEN FUGACITY STUDIES OF MAYURBHANJ BASIC IGNEOUS COMPLEX

The basic igneous complex of Mayurbhanj is a differentiated suite comp osed of harzburgite, gabbronorite, leucogabbronorite and anorthosite. EPMA of the coexisting oxides in the rock samples reveal that magnetit e-ilmenite have re-equilibrated between 770 degrees C and less than 50 0 degrees C and fo(2) of 10(-16) to less than 10(-25). Ilmenite granul es and thick lamellae have identical composition and approach pure FeT iO3. The chromian spinel-olivine geothermometry in harzburgite suggest s a temperature of 1263 degrees C. The pyroxene geothermometric data i n gabbroic rocks indicate equilibration temperature range of 819 degre es C to 1071 degrees C. The thermometric data indicate that the magnet ite and ilmenite equilibrated at lower temperature than the coexisting pyroxenes for a particular rock sample.