Geodynamics of the Tavşanlı zone, western Turkey: Insights into subduction/obduction processes

Abstract

Abstract The tectono-metamorphic evolution of the high-pressure low-temperature (HP–LT) Tavsanli zone (Western Anatolia, Izmir–Ankara suture zone) is herein reappraised to highlight processes occurring along a fossil subduction interface, from initial obduction stages to continental subduction. Structural and petrological data allow in particular to constrain the nature, internal structure and PT conditions of the oceanic accretionary complex sandwiched between the subducted continental margin of the Anatolide–Tauride Block (Orhaneli unit) and the non-metamorphic obducted ophiolite on top. Two distinct oceanic units (termed complexes 1 and 2) are recognised on top of one another, with metamorphic conditions ranging from incipient HP-LT imprint (complex 1) to blueschist facies conditions (complex 2). Based on the first occurrence of Fe–Mg carpholite and on pseudosection calculations, PT estimates of 250–350 °C and 11–13 kbar are inferred for complex 2. The internal structure of the accretionary complex points to the underplating of kilometre-scale units at different depths along the plate interface and to contrasting dynamics with respect to both the underlying continental unit and the ophiolite. Inter-plate mechanical coupling within the Tavsanli zone is compared to the Oman case-study. The variable HP–LT overprint of the metamorphic sole places further constraints on regional scale tectonics, the accretionary dynamics and on the rapid thermal reequilibration of the subduction interface.