Indian KimberIites and Lamprophyres: Mineralogical and Chemical Aspects

Abstract Mineralogical, chemical and isotopic age and abundance data on Indian kimberlites and lamprophyres are discussed to show critical differences. The available K-Ar ages indicate that the kimberlites (840-1120 Ma) are much older than the lamprophyres (56.7-113 Ma). New whole-rock chemical analyses of the Majhgawan diatreme, the only producing diamond mine in India, suggest that fractionation of olivine and spinel has been important during its evolution. In general, the lamprophyres of the Gondwana coalfield bear geochemical similarity with the kimberlites. The source region for both rock types need to be enriched in incompatible elements but the lamprophyres are likely to have formed at shallower depth compared to the kimberlites.