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Crystalline complexes of the Tarbagatai block of the Early Caledonian superterrane of Central Asia |
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| Authors: | I K Kozakov A M Kozlovsky V V Yarmolyuk V P Kovach E V Bibikova T I Kirnozova Yu V Plotkina N Yu Zagornaya M M Fugzan Ch Erdenejargal V I Lebedev G Eenjin |
| Institution: | 1. Institute of Precambrian Geology and Geochronology, Russian Academy of Sciences, nab. Makarova 2, St. Petersburg, 199034, Russia 2. Institute of Geology of Ore Deposits, Petrography, Mineralogy, and Geochemistry, Russian Academy of Sciences, Staromonetnyi per. 35, Moscow, 109117, Russia 3. Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, ul. Kosygina 19, Moscow, 119991, Russia 4. Institute of Geology and Mineral Resources, Mongolian Academy of Sciences, ul. Mira 63, Ulan-Bator, 210351, Mongolia 5. Tuva Institute of Complex Development of Natural Resources, Siberian Branch, Russian Academy of Sciences, ul. Internatsional’naya 117a, Kyzyl, 667007, Russia |
| Abstract: | The oldest crystalline complexes of the Early Caledonian superterrane of Central Asia were formed in the Early Precambrian. They are exposed in the basement of microcontinents, which represent old cratonic fragments. Among the latters are the crystalline complexes of the Tarbagatai block previously ascribed to the Dzabkhan microcontinent. It was shown that the crystalline complexes of the Tarbagatai block have a heterogeneous structure, consisting of the Early Precambrian and later Riphean lithotectonic complexes. Structurally, the Early Precambrian complexes are made up of tectonic sheets of gneisses, migmatites, and gneiss granites of the Ider Complex that are cut by gabbroanorthosite massif. The Riphean Jargalant Complex comprises alternating hornblende crystalline schists and biotite (sometimes sillimanite-bearing) gneisses with marble horizons. The upper age boundary of the Riphean Complex is determined by the subautochthonous granitoids with age about 810 Ma. The presence of the Riphean high-grade rocks indicates that structures with newly formed crust were formed in the paleooceanic framing of the Early Precambrian blocks of the Rodinia supercontinent by the Mid-Late Riphean. Divergence that began at that time within old Rodinian cratons and caused rifting and subsequent break-up of the supercontinent was presumably changed by convergence in the paleooceanic area. |
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