Partial melting of the Indarch (EH4) meteorite: A textural, chemical, and phase relations view of melting and melt migration

To test whether aubrites can be formed by melting of enstatite chondrites a nd to understand igneous processes at very low O fugacities, we have conduc ted partial melting experiments on the Indarch (EH4) chondrite at 1000-1500 C. Silicate melting begins at 1000 C, and Indarch is completely melted by 1500 C. The metal-sulfide component melts completely at 1000 degrees C. Sub stantial melt migration occurs at 1300-1400 C, and metal migrates out of th e silicate charge at 1450 C and similar to 50% silicate partial melting. As a group, our experiments contain three immiscible metallic melts (Si-, P-, and C-rich), two immiscible sulfide melts (Fe- and FeMgMnCa-rich), and sil icate melt. Our partial melting experiments on the Indarch (EH4) enstatite chondrite suggest that igneousprocesses at low fO(2) exhibit several unique features. The complete melting of sulfides at 1000 C suggests that aubriti c sulfides are not relics. Aubritic oldhamite may have crystallized from Ca and S complexed in the silicate melt. Significant metal-sulfide melt migra tion might occur at relatively low degrees of silicate partial melting. Sub stantial elemental exchange occurredbetween different melts (e.g., S betwee n sulfide and silicate, Si between silicate and metal), a feature not obser ved during experiments at higher fO(2). This exchange may help explain the formation of aubrites from known enstatite chondrites.