Petrophysical characteristics of limestone xenoliths in kimberlites from Kirkland Lake, Ontario

Pore-size distribution has been determined by mercury porosimetry for six surface limestones, six diatreme-facies kimberlites, and six limestone xenoliths (from within the kimberlites) sampled from the Kirkland Lake (Ontario) area. The purpose was to investigate how the petrophysical characteristics of limestone fragments change as a result of their mixing with kimberlite magma. Results indicate that while porosities of the xenolith core-material samples are higher than those of the parent limestones, the pore-size distribution patterns are similar, suggesting that these distribution patterns may reflect textural features that are related to the source rock. In contrast, the rim-material samples of the limestone xenoliths show lower porosities than their cores, and display pore-size distribution patterns which are similar to those of the kimberlite that hosted them. These distribution patterns most likely reflect alteration of the limestone xenoliths by the kimberlite magma.