A-type granites and related rocks: Petrogenesis and classification |
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| Institution: | 1. A.A. Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia;2. A.P. Karpinsky Russian Geological Research Institute (VSEGEI), Srednii pr. 74, St. Petersburg, 199106, Russia;3. Novosibirsk State University, ul. Pirogova 2, Novosibirsk, 630090, Russia;1. Institute of Earth’s Crust, Siberian Branch of the Russian Academy of Sciences, ul. Lermontova 128, Irkutsk, 664033, Russia;2. Far Eastern Federal State University, ul. Sukhanova 8, Vladivostok, 690950, Russia;3. Geological Institute, Russian Academy of Sciences, Pyzhevsky per. 7, Moscow, 119017, Russia;4. V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia;1. A.A. Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia;2. Novosibirsk State University, ul. Pirogova 2, Novosibirsk, 630090, Russia;3. Novosibirsk State Technical University, pr. K. Marksa 20/1, Novosibirsk, 630073, Russia;1. V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia;2. Novosibirsk State University, ul. Pirogova 2, Novosibirsk, 630090, Russia;3. Institute of the Earth’s Crust, Siberian Branch of the Russian Academy of Sciences, ul. Lermontova 128, Irkutsk, 664033, Russia;4. Geological Institute, Russian Academy of Sciences, Pyzhevskii per. 7, Moscow, 119017, Russia;5. Tomsk Polytechnic University, pr. Lenina 30, Tomsk, 634050, Russia |
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| Abstract: | The problems of identification of A-type granitoids are analyzed. These rocks occur in different geodynamic settings. Owing to their mantle nature, they show distinct REE specialization. These are acid intrusive rocks, whose volcanic products are of crucial scientific and practical significance. However, neither the great number of proposed classification schemes and diagrams, including those based on expensive analytical data, nor hot scientific discussions of their identification and the ambiguity of the term A-granitoids helped to determine their classification features in full measure. A principally new discriminant diagram is proposed for the classification of igneous A-type rocks, based on the analysis of earlier obtained results and the petrochemical composition of these rocks. A comparative analysis of subdivision of granites and related felsic volcanic rocks (SiO2 > 67 wt.%), based on the ternary (Na2O + K2O)–Fe2O3* x 5–(CaO + MgO) x 5 and other widely applied diagrams, has shown the advantage of the proposed discriminant diagram for the classification of A-type granitoids from different geodynamic settings. |
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