Basites of the Vilyui paleorift: geochemistry and sequence of intrusive events |
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| Authors: | MD Tomshin AG Kopylova KM Konstantinov SS Gogoleva |
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| Institution: | 1. Diamond and Precious Metals Geology Institute, Siberian Branch of the Russian Academy of Sciences, pr. Lenina 39, Yakutsk, 677980, Russia;2. Research Geological Enterprise ALROSA, Chernyshevskoe Shosse 16, Mirnyi, 678174, Russia;3. Institute of the Earth’s Crust, Siberian Branch of the Russian Academy of Sciences, ul. Lermontova 128, Irkutsk, 664033, Russis |
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| Abstract: | We present results of study of the basites of the Vilyui paleorift. Their 40Ar/39Ar isotopic ages were used to establish the sequence of their intrusion, which lasted ~ 18 Myr. Dolerite sills of the Kontai-Dzherba zone were the first crystallizing phase (378.0-380.7 Ma), which was followed by the intrusion of dikes of the Vilyui-Markha zone (372-373 Ma). Dikes of the Chara-Sinsk zone were the last crystalizing phase (362-364 Ma). The prolonged plume-lithosphere interaction resulted in the successive enrichment of basaltic melt with titanium, phosphorus, REE, HSFE, and LILE. Accumulation of the melt and formation of a magmatic lens at the crust-mantle boundary led to early crystallization of the melt at a depth of 35-40 km from the paleosurface under reducing conditions at a temperature of 1450-1470 °C. We assume that the inception and sequent opening of the Vilyui paleorift were associated with the relative rotation of 22° of the Angara-Anabar block with respect to the Aldan block in Early Famennian time. The Euler pole of rotation was located in the southern part of the paleorift, and a melting zone was directly beneath it. |
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| Keywords: | Middle Paleozoic 40 paleomagnetic studies dike swarms dolerites |
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