ABSTRACT Diamond exploration and mantle studies have pushed geochemical methods to very high resolution, which is useful both in evaluating kimberlites and in describing the subcontinental lithosphere. Developing these methods initiated with direct comparisons of distinctive indicator minerals from kimberlite and sediment concentrates to unusual compositions of the same minerals included in diamond. More recently, single grain thermobarometer methods have been developed based on simplifications of equilibrium phase studies of mantle xenoliths and high pressure experiments. These single grain methods have enhanced evaluation of indicator mineral concentrates for diamond potential by greatly increasing the proportion of each suite that provides useful data on mantle conditions. Concurrently, these methods have broadened studies of the subcontinental lithosphere by permitting detailed evaluations beyond the occurrence of kimberlites with well studied mantle xenoliths.
In this review, simple comparison of diamond inclusion compositions for Cr-pyropes, eclogitic garnets, chromite, chrome diopside and enstatite is followed by a review of the concepts behind equilibrium phase thermobarometry, an underlying foundation of increasingly widely applied single grain thermobarometry methods. Descriptions of such single grain methods based on peridotitic chrome diopside, pyrope garnet saturated with chromium and Ni in Cr-pyrope are followed by brief examples of the power of these methods to describe the subcontinental lithospheric mantle.
- Received July 23, 2008.
- Accepted September 15, 2008.
- © 2010 AAG/Geological Society of London