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2013 |
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Comparative characteristic of alkaline rock complexes of Ukraine with other regions of the world Donskoy A.N., Donskoy N.A. M.P. Semenenko Institute of Geochemistry, Mineralogy and Ore Formation of the NAS of Ukraine
Massifs of nepheline rock series are related to the ancient Proterozoic platforms: the Ukrainian and Baltic Shields, geological structures of Southern Africa, the Canadian platform. The nepheline rock series manifestations correspond to long periods of syntectonic magmatism, the periods of global reconstruction of the Earth. The series associate with large deep faults transporting fluids from the depth of the Earth. Such Proterozoic massifs as Sakharyok, Eletozero, Gremyakha-Vyrmes (the Baltic Shield), Yellowknife, Haliburton, Bancroft (the Canadian platform), Palaborwa, Shpitzkop (the Kaapvaal craton) are synchronic to the Ukrainian ones. Judging by a ratio of the alkaline rock complexes of different ages the region of the Ukrainian Crystalline Shield is one of the most ancient Precambrian shields of the world, because the all alkaline massifs were formed after the end of Archean and Paleoproterozoic orogeny. They relate to raised early consolidated megablocks. For edge parts of Precambrian faults zones the relation to long-term deep faults which approach low level of the Earth crust is peculiar. For Meso-Paleozoic era an extension of alkaline series regions and their diversity are characteristic features. Among Ural’s Hercynian orogeny the massifs of miaskites were formed, in the zone of Baltic Shield’s paleorift the Lovozero and Khibiny plutons are well-developed. The similar rocks series of Kazakhstan, Central Asia, Altai-Sayany area, Northern Mongolia, Transbaikal, Northern Cisbaikalia and Eastern China are related to middle Paleozoic rift formation. The general geochemical feature of alkaline series of the world is increased grades of aluminum, alkali (Na, K), rare (Nb, Ta) and rare-earth metals. | ||||
