Permo-Triassic hypabyssal mafic intrusions and associated tholeiitic basalts of the Kolyuchinskaya Bay,Chukotka (NE Russia): Links to the Siberian LIP |
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| Authors: | Galina V Ledneva Victoria L Pease Sergey D Sokolov |
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| Institution: | 1. State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, China;2. Department of Geology, University of Cincinnati, Cincinnati, OH 45221-0013, USA;3. Geological Survey of Canada, 1500 - 625 Robson St., Vancouver, B.C. V6B 5J3, Canada;4. State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074, China;5. Institute of Geology and Paleontology, Tohoku University, Aoba-ku, Sendai 980-8578, Japan |
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| Abstract: | In order to test tectonic hypotheses regarding the evolution of the Arctic Alaska–Chukotka microplate prior to the opening of the Amerasian basin, we investigated rocks exposed near Kolyuchinskaya Bay, eastern Chukotka. Hypabyssal mafic rocks and associated basaltic flows enclose terrigenous sediments, minor cherts and limestones in pillow interstices. The hypabyssal mafic rock yields a U–Pb zircon age of 252 ± 4 Ma and indicates intrusion of basic magma at the Permo-Triassic boundary, contemporaneous with voluminous magmatism of the Siberian large igneous province (LIP). The lava flows and hypabyssal mafic rocks of the Kolyuchinskaya Bay region have trace elements, Sm–Nd and Rb–Sr isotope compositions identical to the tholeiitic flood basalts of the main plateau stage of the Siberian LIP, but differ from the latter in the major-element variations. We conclude that compositional variations in the hypabyssal rocks studied reflect their generation in an extensional environment that might be related to the Siberian super-plume activity at the time. Although the genetic and temporal links between intrusive mafic rocks and lavas are not well proved, compositional variations of the eruptive rocks still indicate their generation in an extensional environment. |
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