Picroilmenite from Kimberlites of the Daldyn Field, Yakutia

摘要

The compositional structure of kimberlite fields is among the blank spots in the geology of kimberlite vol-canism. Identification of pipe clusters within a kimberlite field is based on the geographic principle only, i.e., the spatial association of kimberlite bodies. We used one of the typomorphic kimberlite minerals- picroil-menite- in order to analyze the kimberlite field structure. The abundance of picroilmenite, its stability during the hypergene disintegration of kimberlites and the formation of diamond collectors, and other specific features define a major role for this mineral in prospecting work. The applied significance of picroilmeinite for localization of kimberlite fields has been shown by Sobolev. However, the origin of picroilmenite remains a controversial issue. Researchers have proposed different sources of picroilmenite, such as the asthenospheric layer of the mantle, disintegrated mantle xenoliths, and kimberlite melt. Without going into a discussion, let us note that specific features of the compositional variation of ilmenite over the kimberlite field, which are very important for understanding its genesis, have been virtually ignored in all the hypotheses mentioned above. The present work is devoted to the discussion of the composition of ilmenite from nearly all the pipes of the Daldyn field.