Documenting Exhumation in the Central and Northern Menderes Massif (Western Turkey): New Insights from Garnet-Based P-T Estimates and K-Feldspar 40Ar/39Ar Geochronology

The Menderes Massif (Turkey) is a metamorphic core complex that records Alpine crustal shortening and extension. Here, nine garnet-bearing schist samples in the Central Menderes Massif (CMM) from below the Alaşehir detachment (AD) were studied to reconstruct their growth history. P-T estimates made using a chemical zoning approach, and petrological observations, indicate garnet grew between ~6 kbar and 550°C and 7.5-9 kbar and 625-650°C. Two P-T path shapes from two samples emerged (isobaric and burial), suggesting that either separate garnet-growth events occurred, or different garnet generations from the same metamorphic event were sampled. Despite observable diffusional modification in most garnets, thermobarometric estimates for crystal-rim growth yield P-T estimates similar to those reported elsewhere in the region. Ion microprobe monazite ages, paired with textural observations, from three of the samples time early retrograde metamorphism (~36-28 Ma). To better understand Neogene extension/exhumation, K-feldspar 40Ar/39Ar ages were obtained from two synextensional granites (Salihli and Turgutlu) exposed along the AD and two from the northern Simav detachment (Koyunoba and Eğrigöz). This data suggests the Simav detachment footwall rapidly exhumed at ~20 Ma, whereas the AD experienced two periods of exhumation/cooling (~14 Ma and~5 Ma). AD ages support a pulsed exhumation model for the massif.

“Rootless” Ophiolites above the Exhuming Pelagonian Core Complex, Northern Greece

The Mesohellenic ophiolites (MHO) in the Western Hellenides are part of an oceanic slab emplaced onto Pelagonian (Pangaean) continental rocks in the mid-Jurassic with a documented NE ophiolite emplacement. Ophiolitic outliers to the east of the MHO are oceanic lithospheric fragments, not complete ophiolite bodies, preserved above exhumed Pelagonia continental rocks. As these fragments lack connection to original root zone provenance, we refer to these as the “rootless” ophiolites.Pelagonian exhumation, possibly triggered by transcurent shear along its continental margin with the Pindos basin, began by the Late Jurassic and continued into the mid-Cretaceous. Exhumation affected the emplaced oceanic slab in the following ways: i) The metamorphic facies of the basal mélange separating the ophiolite from the Pelagonian basement grades from phyllitic to schist and amphibolite-schist over the exhumed Pelagonia. ii) Ophiolitic remnants are metasomatized where in contact with the exhumed Pelagonian rocks. iii) Remnant ophiolitic fragments are rotated and largely disassociated from their original relative pseudostratigraphic positions in their parent slab. iv) No amphibolite emplacement soles are preserved beneath ophiolitic remnants found directly above Pelagonia.East of Vourinos, remnants of the slab were tectonically entrapped between the exhuming Pelagonian core and its sedimentary overburden, and demonstrate extensional, largely gravitational displacements as well as rotation from original emplacement vectors. Primary constrictive slab emplacement features are obscured, but a general westerly sense of kinematics via listric and extensional faults have been imprinted. In the exhumation model, this "SW topping" direction cannot be interpreted as indicative of an eastern origin of the Pindos Basin ophiolites from the Vardar Zone, but rather as a local response to the uplift of Pelagonia and active deformation of the sedimentary overburden.