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Petrogenesis and Geochemistry of Tabas Black Land volcanic field: implications for volcanic activity along the Nayband fault, East Iran

Abstract : The 14 Ma Tabas Black Land volcanic field lies on the major active Nayband Fault, Western Lut Block, central-east Iran. Eroded cones and broad craters are surrounded by lavas. Eastern lavas are fault-deformed, partly covered by sediments, while western undeformed lavas stand out as inverted relief. We study the magmatic evolution of this volcanic field and assess relationships with regional tectonics. Compositions are intraplate basaltic trachyandesite-basaltic-andesite, produced from postcollisional asthenospheric melting. Modelling indicates 5-10 wt.% partial melting of primary garnet peridotite mantle with residual garnet. Modest K 2 O values are consistent with limited source hydrous phases (e.g. phlogopite). Low P 2 O 5 /K 2 O indicates little crustal contamination. Geothermobarome-try results point towards lower crust (480-760 MPa = 18-29 km) magma storage and differentiation, where olivine and clinopyroxene fractionated to produce differentiated trachybasalt to basaltic trachyandesite at magma temperatures of 1150-1200 • C. Compared to other Lut Block volcanics, there is more partial melting in Tabas, with the lowest level of crustal contamination. The ongoing 14 million year period of volcanism along the Nayband Fault appears to have had the same source, migrating southwards over time from the Tabas Black Lands with decreasing partial melting. Nayaband magmatism seems to be dwindling, even if the fault itself remains active.
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Submitted on : Thursday, November 26, 2020 - 10:09:02 AM
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Esmail Elahpour, François Nauret, Etienne Médard, Mhammed Benbakkar, Gabrielle Quéinnec, et al.. Petrogenesis and Geochemistry of Tabas Black Land volcanic field: implications for volcanic activity along the Nayband fault, East Iran. Volcanica, Presses Universitaires de Strasbourg, 2019, 2 (2), pp.105-127. ⟨10.30909/vol.02.02.105127⟩. ⟨hal-02278205⟩

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