INTERACTION BETWEEN MAFIC AND FELSIC MAGMAS IN SUBVOLCANIC Environment ( TASTAU IGNEOUS COMPLEX, EASTERN KAZAKHSTAN )
K.A. Dokukinaa, A.N. Konilova, T.V. Kaulinab, and V.G. Vladimirovc
aGeological Institute, Russian Academy of Sciences, Pyzhevskii per. 7, Moscow, 119017, Russia
bGeological Institute, Kola Science Center, Russian Academy of Sciences, ul. Fersmana 14, Apatity, 184209, Russia
cV.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, prosp. Akad. Koptyuga 3, Novosibirsk, 630090, Russia
Keywords: Synplutonic intrusions, coeval magmas, mingling, mixing, intraplate magmatism
Pages: 625-643
Abstract
The paper reports the results of integrated geological, petrological, geochemical, and geochronological studies of the Tastau igneous ring complex in the Zaisan orogen of eastern Kazakhstan. Interaction between felsic and mafic magmas has been studied. Hybrid rocks are represented by gabbros and diorites injected into a granitic magma chamber. They occur as dikes and pillow-like and globular mafic bodies variously disintegrated and mixed with host granitoids. The age of synplutonic rocks is 242±20 Ma (U/Pb zircon dating), which is, with regard to analytical error, substantially younger than it was presumed.
Mechanisms of interaction between felsic and mafic magmas have been studied. They include mechanical (mingling) and chemical (mixing) inreractions, which produce composite mixtures and hybrid rocks. The ratios of mafic to felsic components involved in the formation of intermediate rocks were calculated from major elements by regression analysis and tested with regard to rare and trace elements. The model for mingling includes quenching of the mafic melt when it is injected into the granitic magma chamber, decomposition of crystalline fragments, dispersion of fragments and crystals in the magma chamber under conditions of rapid turbulent flow, and enrichment of felsic magma with femic components to produce monzonitic magmas.
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