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)

摘要

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 degrees C) 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. (C) 2015, V.S. Sobolev IGM, Siberian Branch of the RAS. Published by Elsevier B.V. All rights reserved.