The characteristics of the plume magmatic activity in middle part The Russian platform (Ust diamondiferous district)

Predictive and prospecting research is the example of «inverse geological task» according to preliminary spatial localization of specific region of a plume activity, prediction and estimation of ore potential of one region in a middle part of the Russian platform. The Ustyansky potential region is characterized by coinciding of all the advantageous regional and local searching suppositions in space (morphostructural, tectonic, geologic-stratigpaphical, geophysical, morphometrical, mineralogical) and search features. It can be caused by implementing of mantle diapir (plume) and can be accompanied by diamong-bearing kimberlitemagmatism. Heavy diamond concentrate contents (most of all of pirop (1206 grains), not so many
of pycroilmenite, chromespinelide, olivine, chromedyopside) in alluvion of the region is 3-5 times higher than in the ZimnyBereg diamond-bearing region. Furthermore, contents of pirop of diamond paragenesis of the G10 group is about 10%. In stream sediment samples of minimum amounts, taken from alluvial and quaternary deposits, nine diamond crystals had been founded. Six of them (octahedrons and dodecahedrons with sizes up to 3,8 mm and weight up to 52 mg) had been founded in «Severnoe» kimberlite potential field. According to a complex of morphological and physical features all diamonds of the Ustyansky region occupy a completely outlier position and have almost no analogues among the diamonds of
large known deposits and mineral occurrences of Arkhangelsk, Finland, Urals and Timan, This might indicate to crystals flowing from a new, still unknown native source (or sources) of kimberlite. This new native source of kimberlite may be heightened diamond potential and may contain high-quality and big-size diamonds. Detection of this new native source will be a final confirmation of predictable selection of the Ustyansky region as a region of a plume activity. Features of possible similarity of the Arkhangelsk diamond-bearing province to the Yakutsk diamondbearing province in relation to patterns of kimberlite position and morphological features of diamond crystals, confirm great prospects of diamond-bearance of central
regions of the European part of Russia at all, and particularly of the Ustyansky region with «Severnoye» kimberlite potential field.