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Trace element composition and Lu-Hf isotope systematics of zircon from plagiogneisses of the Kola superdeep well: Contribution of a Paleoarchean crust in Mesoarchean metavolcanic rocks |
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| Authors: | V R Vetrin E A Belousova V P Chupin |
| Institution: | 1. Geological Institute, Kola Science Center, Russian Academy of Sciences, ul. Fersmana 14, Apatity, 184209, Russia 2. NSW 2109, Macquarie University, Department of Earth and Planetary Sciences, Faculty of Science, Sydney, Australia 3. Sobolev Institute of Geology and Mineralogy, Siberian Branch, Russian Academy of Sciences, pr. Akad. Koptyuga 3, Novosibirsk, 630090, Russia 4. Novosibirsk State University, ul. Pirogova 2, Novosibirsk, 630090, Russia |
| Abstract: | Zircons have been studied in three samples of Archean plagiogneisses from the Kola superdeep well (SG-3). The crystals consist of cores, magmatic shells, and metamorphic rims. The cores and shells are characterized by similar lowered concentrations of most trace elements, which is typical of zircons from plagiogranitoids, rocks of elevated basicity, and basites. At a wide range of Hf isotope characteristics, the cores and shells have similar average 176Hf/177Hfi, which determines the close composition of their sources. The metamorphic rims have close 176Hf/177Hfi ratio. The minimum age of the crustal contaminant of parental melts is estimated at 3.4 and 3.3 Ga for cores and 3.3–3.2 Ga for shells at almost equal proportions of mantle and crustal components in them. The contribution of Paleoarchean crust established in zircons from plagiogneisses of SG-3 using Lu-Hf isotope systematics is confirmed by the presence of 3.3and 3.4-Ga old zircons in surrounding TTG. |
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