Metamorphic Sole and Accreted Units Along a subduction Interface: form Birth to Steady State (the Case of Western Turkey)

Abstract:

In Western Turkey, obducted ophiolite, metamorphic sole and oceanic accretionnary complex units linked with the closure of the Neotethys are found along a 400 kilometre-long section (from north to south). We herein reappraise the metamorphic evolution of the sub-ophiolitic metamorphic units (both the metamorphic sole and the accretionnary units) of Western Turkey (i) to better characterize rock units exhumed along a cooling subduction interface, from birth to steady state (ii) to constrain the formation of metamorphic sole during the initiation of subduction (iii) and to track record of obducted ophiolite. On the basis of field and petrological observation three differents accretionnary units are reccognized with pressure-temperature estimates ranging from incipient metamorphism to blueschist-facies conditions providing information on plate coupling at different depths along the subduction interface. The upper part of the metamorphic sole was form in an amphibolite facies (garnet amphibolite - garnet clinopyroxene amphibolite). Different slices of metamorphic sole with different pressure-temperature conditions might be observed probably showing discrete timing of accretion to the upper plate. Part of the samples are characterized by a late blueschsit developpement. Both the blueschist overprint in the metamorphic sole and the high-pressure in oceanic unit were found only in the northern part of the field investigation. On the basis of the presented data, available radiometric and palaeogeographic data as well as recent themomechanical moddeling a tentative reconstruction of the subduction-zone evolution through time and the emplacement of a large-scale ophiolite is presented. Finally a comparison with ongoing work on the metamorphic sole of the Semail ophiolite of Oman is proposed with special highlights on the retrograde evolution in both settings.

 

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