Petrology of the Late Jurassic ultramafic-mafic Veselki massif,southeastern framing of the Siberian craton |
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| Authors: | I V Buchko A E Izokh E B Sal’nikova A A Sorokin A B Kotov S Z Yakovleva |
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| Institution: | (1) Institute of Geology and Natural Management, Far East Division, Russian Academy of Sciences, ul. B. Khmel’nitskogo 2, Blagoveshchensk, 675000, Russia;(2) Geological Institute, United Institute of Geology, Geophysics, and Mineralogy, Siberian Division, Russian Academy of Sciences, pr. Ak. Koptyuga 3, Novosibirsk, 630090, Russia;(3) Institute of Precambrian Geology and Geochronology, Russian Academy of Sciences, nab. Makarova 2, St. Petersburg, 199034, Russia |
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| Abstract: | The Veselki peridotite-websterite-gabbronorite massif was dated by U-Pb zircon method at 154 ± 1 Ma. This is the first Late Jurassic date obtained for ultramafic-mafic massifs in the eastern part of the Selenga-Stanovoy superterrane bounding the southeastern margin of the Siberian craton. The mineralogical specifics of the massif is expressed in the presence of three-pyroxene assemblage bronzite-pigeonite-augite (diopside)] and exsolution lamellae of Cr-spinel and Cr-magnetite in Fe-Cr picotite and suggests unstable crystallization at shallow depths. Geochemical similarity between the Upper and Lower series attests to their genetic relation through intrachamber differentiation. The massif was generated from a highly evolved melt, as is seen from the LREE enrichment (La/Yb)N = 3.89–30. Plagioclase varieties display a weak positive Eu anomaly (Eu/Eu* = 1.1–1.25), whereas other rocks have an insignificant negative Eu anomaly (Eu/Eu* = 0.85–0.97). Model calculations show that parental melt was close to subalkaline picrite, which evolved along two fractionation trends into dunites and subalkaline gabbroids and monzodiorites. |
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