Lloyd White, Ian Graham, Dominique Tanner, Robert Hall & Richard Armstrong
This study aimed to determine the enigmatic source for the Cempaka paleo-alluvial diamond deposit. To do this, we: (1) dated detrital zircons to understand the age of potential source material; (2) obtained geochemical data from Cr-spinels to verify if a kimberlite/lamproite source was evident, and; (3) examine the morphology and age of the zircon grains relative to the morphology and chemistry of diamonds to test the tectonic model(s) that have previously been proposed to explain the origin of the Cempaka diamonds.
Several gem quality diamond deposits are found within paleo-alluvial sediments in several locations in southern Borneo. Various models have been proposed to explain the origin of these diamonds. They may have been emplaced in kimberlite/lamproite pipes in Borneo or could be related to diamond deposits in NW Australia, and carried with the Southwest Borneo Block after it rifted from Australia in the Late Jurassic. Alternatively, the diamonds could have been produced in subduction zones in Asia, and were later transported to Borneo via major river systems.