Localization of High-Titanium Dolerites in Kimberlite Fields: Possible Causes and a New Criterion for Kimberlite Search

Abstract

Abstract ––The generalized chemical composition data on the studied dolerites from the Vilyui–Markha dike swarm (Vilyui paleorift) allowed detecting geochemically anomalous areas among them. It has been found that percentage of TiO2 and a number of heavy rare-earth elements (Th, Ta, Hf, Y, Nd) in the dolerites of dikes located within the kimberlite fields show almost twofold increase compared to the normal content for these elements in the Vilyui–Markha dolerites. Similar behavior of these elements is also observed in the dolerite dikes near the Kuoika kimberlite field (the Molodo dike swarm, Olenek paleorift). It is inferred that there is a connection between the increase in abundances of titanium and rare-earth elements in the dolerites and that the latter occur within the lithosphere blocks hosting kimberlite fields. The areas of lithospheric mantle roots linked with the formation of proto-kimberlites may have had bearing on the composition of tholeiite melt both in the processes of its generation and during its ascent to the Earth’s surface, which led to its local enrichment in titanium and a number of other elements. While the processes of the alignment of the geochemical composition between the high-titanium basites and the rest of the melt beyond the contours of the lithospheric blocks with kimberlite fields were weakly pronounced, they were responsible for appearance of zones enriched in titanium. Kimberlite fields that formed before or after basite magmas intrusion overlap with placements of high-titanium dolerite dikes. Thus, high-titanium dolerites in dike swarms (belts) can be used as one of the criteria for kimberlite searches. In view of the above, two new potential zones (Tenkelyakh and Kyulenke areas) for kimberlite exploration have been identified within the Vilyui–Markha dike swarm.