Chemistry of Garnet and Ilmenite from Majhgawan Diamondiferous Pipe, Panna District vis-a-vis Diamond Potential and Preservation

The compositional trends in ilmenites from Majhgawan indicates slightly increased values of -log f02 i.e., 9.2. The divariant plots of Fe₂O₃ vs MgO and Cr₂O₃ vs MgO indicate resorption of most diamonds. The rounded-dedecahendra from indicates a preservation percentage of 65-70. The wine-red garnets from diamondiferous pipe are moderately subcalcic. The CaO vs Cr₂O₃ plot shows that they fall very close to the 85 percent Gurney line indicating emplacement at the craton margin having moderate diamond content. Geothermobarometry based on the co-existing pyropeknorringite and spinel geothermobarometer for the diamondiferous pipe yielded an equilibration temperature and pressure of 1160°C and 47 KbaT.