Behaviour of dolerite intrusion into kimberlite bearing rocks

The unusual behaviour of dolerite sills (traps) near kimberlite pipes in the Daldyno-Alakitsky diamondiferous region of Western Yakutia, Siberia, has been studied. Formation of kimberlite pipes occurs through explosive pulses that shift upward, causing significant compaction of the overlying sedimentary rocks. This process generates thermoelastic stress fields, leading to epigenetic and petrophysical changes, such as variations in density and magnetic properties. As a result, the areas surrounding kimberlite pipes become less accessible to relatively viscous, crystal-rich mafic magmas. When emplaced near kimberlite pipes, these mafic intrusions – primarily sills – can form torus-shaped zones with sharply increased thickness. In some instances, magma flowing around kimberlites creates dolerite-free ‘windows’, while in others, it splits into thin ‘tongues’. Additionally, sills adjacent to kimberlites often become crumpled and take on a wave-like shape. We propose that identifying these morphological features in sills can serve as an indirect method for locating kimberlite pipes and determining optimal drill hole sites, particularly in regions with a continuous mafic cover dominated by dolerite sills, such as Western Yakutia, Siberia.