Browsing by Subject "indicator mineral chemistry"

Kimberlites are a primary source of diamonds. However, not all kimberlites contain diamonds, let alone in the abundance that enable economically profitable exploitation. To assess the diamond potential of kimberlites, the study of kimberlite/diamond indicator minerals (i.e. mantle-derived xenocrysts) can be utilized. In this study the diamond potential of Liqhobong kimberlite cluster in Lesotho, Southern Africa, was studied. Indicator mineral grains (chromian diopside, garnet, chromite, ilmenite) from Liqhobong kimberlites were analysed for major and minor elements using electron microprobe. Results were used to examine formation conditions (P/T) and chemical characteristics of indicator minerals, to define local geotherm and diamond window and to provide general overview to diamond potential of the Liqhobong kimberlite cluster. Based on single clinopyroxene thermobarometry (using Cr-diopside grains as a thermobarometer), the local Liqhobong geotherm is estimated to be ~41 mW/m². It corresponds reasonably accurately to the reference geotherm 40 mW/m², which is widely considered being a decent “average” geotherm at Kaapvaal-Kalahari Craton area. Analysed xenocrysts are principally from the peridotitic source rock. Geochemistry of the indicator minerals show that there is a significant diamond potential in Liqhobong kimberlites. Specifically, Ni-in-garnet thermometry, using the formation depth of the G10 garnets combined to the relevant 40 mW/m² reference geotherm, displays the existence of a significant diamond window at the depth interval of ~140-230 km below the Liqhobong area.