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Russian Geology and Geophysics

2015 year, number 3

ROLE OF BACK–ARC TECTONICS IN THE ORIGIN OF SUBDUCTION MAGMAS: NEW SR, ND, AND PB ISOTOPE DATA FROM MIDDLE MIOCENE LAVAS OF KUNASHIR ISLAND (Kurile Island Arc)

A.Yu. Martynov1, Yu.A. Martynov1, A.V. Rybin2, J.-I. Kimura3
1Far East Geological Institute, Far Eastern Branch of the Russian Academy of Sciences, pr. 100-letiya Vladivostoka 159, Vladivostok, 690022, Russia
2Institute of Marine Geology and Geophysics, Far Eastern Branch of the Russian Academy of Sciences, ul. Nauki 5, Yuzhno-Sakhalinsk, 693022, Russia
3Institute for Research on Earth Evolution, Japan Agency for Marine-Earth Science and Technology Yokosuka, 237 0061, Japan
Keywords: Primitive lavas, radiogenic isotopes, evolution, magma generation, geodynamics, Kurile island arc

Abstract

Sr, Nd, and Pb isotope data for basaltic rocks of different ages from Kunashir Island (southern Kurile island arc) provide clues to investigate the subduction magmatic history. Signatures of a high-temperature slab component (melt and/or supercritical liquid produced by melting of slab sediments) involved in Early Miocene-Pleistocene back-arc basaltic magmatism indicate a relatively hot (>800 ºC) slab surface. Depleted isotope characteristics of Holocene basaltic lavas in both volcanic front and back arc indicate their origin with the participation of a cold aqueous fluid produced by dehydration of altered oceanic crust of the Pacific MORB type. The difference in geological, geochemical, and isotope patterns in the Pleistocene and the Holocene lavas may be a response to stress change from extension to compression in the Kurile back-arc basin and the Kurile arc.

DOI: http://dx.doi.org/10.1016/j.rgg.2015.02.001