High-pressure-low-temperature metamorphism of metasedimentary rocks,southern Menderes Massif,western Turkey

摘要

Kilometer-scale lenses of quartz-rich metasedimentary rocks crop out in a discontinuous belt along the southern margin of the Menderes Massif,Turkey,and preserve evidence for high-pressure-low-temperature(HP-LT)metamorphism related to subduction of a continental margin during Alpine orogeny.Kyanite schist,quartzite,and quartz veins contain kyanite+phengite+Mg-chlorite,and the veins also contain magnesiocarpholite.A deformed carbonate metaconglomerate juxtaposed with the quartzite-dominated unit does not contain HP index minerals,and likely represents the tectonized boundary of the siliceous rocks with adjacent marble.The HP-LT rocks(10-12 kbar,470-570°C)record different pressure conditions than the adjacent,apparently lower pressure Menderes metasedimentary sequence.Despite this difference there is disagreement as to whether these HP-LT rocks are part of the Menderes sequence or are related to the tectonically overlying Cycladic blueschist unit.If the former,the entire southern Menderes Massif experienced HP-LT metamorphism but the evidence has been obliterated from most rocks;if the latter,rocks recording different metamorphic-kinematic conditions experienced different tectonic histories and were tectonically juxtaposed during thrusting.Based on observations and data in this study,the second model better accounts for the differences in P-T-deformation histories of the southern Menderes Massif rocks,and suggests that the HP-LT rocks are not part of the Menderes cover sequence.