Geochemical characteristics and age of metamorphic sole rocks within a Neotethyan ophiolitic melange from Konya region (central southern Turkey)

Palaeo- and Neo-Tethyan-related magmatic and metamorphic units crop out in Konya region in the south central Anatolia. The Neotethyan assemblage is characterized by melange and ophiolitic units of Late Cretaceous age. They tectonically overlie the Middle Triassic-Upper Cretaceous neritic to pelagic carbonates of the Tauride platform. The metamorphic sole rocks within the Konya melange crop out as thin slices beneath the sheared serpentinites and harzburgites. The rock types in the metamorphic sole are amphibolite, epidote-amphibolite, garnet-amphibole schist, plagioclase-amphibole schist, plagioclase-epidote-amphibole schist and quartz-amphibole schist. The geochemistry of the metamorphic sole rocks suggests that they were derived from the alkaline (seamount) and tholeiitic (E-MORB, IAT and boninitic type) magmatic rocks from the upper part of the Neotethyan oceanic crust. Four samples from the amphibolitic rocks yielded 40Ar/39Ar isotopic ages, ranging from 87.04 +/-.36Ma to 84.66 +/-.30Ma. Comparison of geochemistry and geochronology for the amphibolitic rocks suggests that the alkaline amphibolite (seamount-type) cooled below 510 +/- 25 degrees C at 87Ma whereas the tholeiitic amphibolites at 85Ma during intraoceanic thrusting/subduction. When all the evidence combined together, the intraoceanic subduction initiated in the vicinity of an off-axis plume or a plume-centered spreading ridge in the Inner Tauride Ocean at 87Ma. During the later stage of the steady-state subduction, the E-MORB volcanics on the top of the down-going slab and the arc-type basalts (IAT/boninitic) detached from the leading edge of the overriding plate, entered the subduction zone after similar to 2 my and metamorphosed to amphibolite facies in the Inner Tauride Ocean. Duration of the intraoceanic detachment (similar to 87Ma) and ophiolite emplacement onto the Tauride-Anatolide Platform (Tavsanli Zone), followed by subsequent HP/LT metamorphism (similar to 82Ma) spanned similar to 5 my in the western part of the Inner Tauride Ocean.