Post-eruptive processes in kimberlites - implications for diamond exploration

Deposits of primary diamond ore-kimberlite and, less commonly, lamproite an d lamprophyre volcanics and intrusives-are scarce, and even in highly prosp ective terranes geochemical and geophysical methods are needed to facilitat e location of the tiny volcanic targets. The environment at the time of eru ption and, more importantly, the environments to which the diamond-bearing volcanic material has been subjected since eruption condition how targets w ill respond to these survey methods. Post-eruption processes within the cra ter, such as serpentinization, and beyond the crater-in particular, the eff ects of erosion-are outlined and illustrated by reference to the Fort a 1a Corne kimberlite field in western Canada. The consequences for exploration of such factors as groundwater and seawater levels, uplift and climate are indicated.