Diamond prospectivity of Mesoproterozoic kimberlites from the Wajrakarur field, southern India: perovskite oxybarometry and bulk-rock transition element geochemistry constraints

Abstract

Prognostication of the primary diamond host rocks such as kimberlites and lamproites is traditionally carried out by deploying proven techniques such as indicator (xenocryst) mineral chemistry and pressure-temperature estimates on co-existing phases in mantle xenoliths. However, in the recent past new methodologies-such as estimation of redox nature of the magmas from perovskite oxybarometry and response of first-row transition elements to oxygen fugacity-essentially involving the bulk-composition of the host rocks have also emerged for predicting the diamond prospectivity. Here, we test the applicability of such host rock models to the well-characterized Mesoproterozoic kimberlites from the Wajrakarur field, eastern Dharwar craton, southern India, whose diamond incidence is well-established. We demonstrate that a combination of perovskite oxybarometry and transition element geochemistry in conjunction with petrography can impose better first order controls on the prognostication of the primary diamond host rocks rather than by applying them individually, in isolation. We also highlight that such a combined approach holds as much promise as the well-established and age-old prognostication techniques that are currently in vogue, for inferring the diamond prospectivity of the primary host rocks.