Morphology of trap sills near kimberlites

Abstract

Research subject. Trap sills of the Daldin-Alakit diamond-bearing region of western Yakutia. Aim. To establish the reason for the influence of sedimentary rocks containing kimberlite diatremes on the introduction of basite magma that forms trap sills and the possibility of using the morphology of sills as a search signs for kimberlites. Materials and methods. Sections of trap sills near kimberlites, their structure, petrographic and petrochemical composition of dolerites performing sills were studied. Results. During the formation of kimberlite diatremes, accompanied by pulsating explosions shifting to the top, a significant compaction of the sedimentary rocks containing kimberlites occurs, associated with thermoelastic stress fields. This process leads to the formation of zones near kimberlites, which are difficult to penetrate for relatively viscous, protocrystalline-enriched basite magmas. When such magmas are introduced, the latter before kimberlites form torus-shaped shafts with a sharply increasing power in intrusions. Sometimes magma, flowing around kimberlites, creates “trappless windows”, occasionally splitting into low-power “tongues”. Quite frequently, before kimberlites, sills crumple, acquiring a wave-like shape. Conclusion. All the listed morphological features of traps arise during the introduction of magma, thus providing an indirect method of searching for kimberlites, particularly during the areal drilling of territories covered by continuous trap fields conducted by ALROSA in Western Yakutia.