The Problem of the Core-Cover Boundary of the Menderes Massif and an Emplacement Mechanism for Regionally Extensive Gneissic Granites, Western Anatolia (Turkey)


Abstract: In previous studies, the stratigraphy of the Menderes Massif was divided into a Precambrian core and Mesozoic cover associations, the core consisting of gneissic granites and high-grade schists and the cover of mica schists and platform-type marbles. It has also been proposed that the two associations are separated by an unconformity although nowhere is this relation clearly observed. In this study, the Bafa and Kavaklıdere areas in the southern part of the massif have been examined. In the Bafa area, Mesozoic mica schists with marble lenses occur in the lowermost parts of the sequence and are overlain, along a gradational boundary, by a Mesozoic carbonate succession. Gneissic granites cut the detrital parts of this Mesozoic succession and the boundary is clearly intrusive, characterised by enclaves of schist within the granite body and seams and veins of granite cutting the surrounding mica schists. In the Kavaklıdere area, Mesozoic metaclastics and platform marbles are underlain by the Permo-Carboniferous Göktepe Formation which consists of black marble, chert and quartz-mica schist intercalations. The gneissic granites in this region also have intrusive contact relations with surrounding rocks and cut the Göktepe Formation. The granites were emplaced syntectonically during the main Menderes metamorphism which took place in Late Cretaceous-Early Cenozoic time and included strongly assimilated mica schist zones and patches. These granites are geochemically S-type, peraluminous and of syn-collisional character. The subdivision of the stratigraphy of the massif into core and cover associations based on the position of the gneissic granites is incorrect. The Lycian Nappes were thrust northward coevally with the main Menderes metamorphism, and the Menderes platform was recumbently folded. Along the cores of these north-verging folds, granitic melts were emplaced syntectonically and strongly assimilated, and rejuvenated the lower parts of the platform sequence. Inversion of the metamorphic grade and vertical repetition of gneisses and mica schists in some areas are consequences of recumbent flow folding.

Keywords: gneissic granites, syntectonic granites, Menderes Massif, western Anatolia

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