Origin of Spinel Macrocryst of 1.1GA Kimberlite Clan Rocks from Central Indian Diamond Province

Spinels from 2 kimberlite pipes from the Central Indian Diamond Province (CIDP) have been analysed. Most of the spinels are classified as high-chromium chromite (Chr) and xenocryst spinel (Xen) representing two significant stages of spinel formation. Most of the spinel in the study are dominated by Magnesiochromite composition in the range of Cr/Cr+Al>0.5 and Fe²⁺ / Fe²⁺ + Mg <0.5. These composition ranges are characteristic of a depleted peridotite, which formed as a result of magmatic depletion processes. Majority of spinel grains are interpreted to be xenocrysts, derived by the disintegration of garnet bearing mantle peridotites, that laterwere swept up by kimberlite magma.Three compositional trends can be observed from spinel analysis, Trend T1 (Cr/(Cr+Al) = 0.80 to 0.90) representing the primary spinel, crystallizing directly from kimberlite and Trend T2 (Cr/Cr+Al = 0.60 to 0.80) & T3 (Cr/(Cr+Al) = <0.60) assumed be the product of interaction between the depleted peridotite and fertile fluids or magma (refertilization).