Paper No. 49-10
Presentation Time: 11:15 AM
DECIPHERING P-T-T CONDITIONS OF METAMORPHIC ROCKS FROM THE SOUTHERN MENDERES MASSIF OF SW TURKEY
The Aegean region contains numerous metamorphic core complexes that reflect post-collision extensional tectonics. The largest of these is the Menderes Massif of Turkey, which covers an area of ~40,000km2. At its southern border is the Selimiye Shear Zone, a key location for studying the metamorphic history of the Menderes Massif. Only limited and scattered pressure-temperature-timing (P-T-t) data exists in the Southern Menderes Massif (SMM), and here we report conditions to supplement information regarding its evolution. Rocks were collected perpendicular to strike along 7 spaced transects in the SMM. We analyzed garnets in the samples using electron beam microscopy and obtained high-resolution back-scattered electron (BSE) images, X-ray element (Fe, Mg, Mn, Ca and Y) maps, and quantitative compositional data. We completed in thin section or in-situ U-Pb dating of zircon and U,Th-Pb dating of monazite to determine the age relationship of matrix and inclusion grains hosted by garnet. The results show the garnets record a complex metamorphic history and ages reveal timing constraints of a Pb loss event and garnet growth. Sixteen garnet X-ray element maps from separate samples show zoning consistent with multiple stages of growth, diffusion, and retrogression. The zoning is often visible in high contrast BSE images and indicates the rocks experienced conditions inconsistent with a simple, single stage metamorphic history. We applied common thermobarometers to generate preliminary peak metamorphic P-T conditions. The rocks record 545±20 ºC to 652±25 ºC and high pressures (11.0±1.8 kbar to 14.8±1.1 kbar). U-Pb zircon ages range from 253.0±5.0 Ma to 2022.0±30.0 Ma, and monazite ages have U-Pb and Th-Pb ages from 17.5±2.4 Ma to 130.2±15.8 Ma. Data reported here support the hypothesis that polymetamorphism is recorded in SMM rocks in close proximity to the Selimiye Shear Zone. To model the thermal evolution of the region accurately requires an understanding of the peak P-T the rocks experienced and the time at which they were at those conditions.