COMPOSITION FEATURES OF MAFIC ROCK-FORMING MINERALS IN THE ROCKS OF THE BURPAL ALKALINE MASSIF (NORTHERN BAIKAL REGION)
A.V. Malyutina1, 2, A.G. Doroshkevich1, 3, A.E. Starikova1, 2, I.A. Izbrodin1, 2, I.R. Prokopyev1, 2, T.A. Radomskaya2, 4, M.N. Kruk1, 2
1Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy, Novosibirsk, Russia
2Novosibirsk State University, Novosibirsk, Russia
3Geological Institute, Siberian, Branch of the Russian Academy of Sciences, Ulan-Ude, Russia
4Vinogradov Institute of Geochemistry, Siberian Branch of the Russian Academy of Sciences, Irkutsk, Russia
Keywords: Burpala massif; alkaline syenites; clinopyroxene; amphibole; mica; Northern Baikal region.
Abstract
Petrographic and mineralogical studies of the main varieties of rocks composing the Burpalа massif have been carried out: peralkaline (nepheline) syenites, alkaline syenites, quartz syenites. The emphasis was placed on the macro- and microelement composition of mafic minerals present in all types of rocks: clinopyroxenes, micas, amphiboles. Studies have shown that the composition of mafic minerals fractionates within each group of rocks, but in individual groups - peralkaline, alkaline and quartz syenites, their compositions do not fit into a single trend of evolution. Based on these observations, it can be assumed that the formation of the massif occurred under conditions of pulsed introduction of magma portions of various degrees of differentiation, as well as the probability of contamination of the first portion of magma with subsequent formation of quartz syenites.
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