New data on geochemistry of ongonites
Ongonites of Mongolia are extremely enriched with Rb, Cs, Hf, Ta and depleted with Ba, Sr. Clear Eu minimum, typical of major part of rare-metal and alkaline rare-metal granitoids, is well defined. At the same time this rocks include elevated concentrations of F, Li, Tl, Sn, Be and Nb. This fact provides an opportunity to identify them as specific Li-F geochemical type of granitoids. Radiogeochemical peculiarities of these rocks (U - 5,7 ppm, Th - 20,6 ppm, K - 4%) are indicative of their specialization in regard to Earth's crust clark. They are similar to rhyolites and felsites of Kazakhstan, Eastern Sayans, Transbaikalia and several types of high-silica volcanites in USA (the Rocky Mountains, Spor-Mountain), Mexico, Japan. New data on geochemistry of natural radioactive elements in ongonites confirm that this high-fluoride rare-metal acid dyke complex have genesis from magmatic melt: Th/U ratio is more than 3 that typical for igneous rocks. The presence of such geochemically specified igneous rocks is an evidence of high ore-bearing potential capacity of this Earth's crust part due to contribution of matter from asthenosphere probably incoming along with plumes. Dyke rocks in Gorny Altai, known as "kalgutites", could not be considered as analogues of ongonites since they have ultimately different radiogeochemical characteristics (Th/U < 1) that most likely to reflect high degree of their metasomatic changes. Therefore, radiogeochemical characteristics could and should be used as indicators of igneous origin of rocks