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Evolution of a mid-Tertiary extensional shear zone in the southern Menderes massif, western Turkey

1997-01-01
Bozkurt, Erdin
Park, RG
The late Oligocene evolution of the southern Menderes Massif in western Turkey involves deformation in a crustal-scale, moderately dipping, ductile shear zone. The granitic rocks of the massif have been progressively transformed to augen gneisses along the footwall of a south-dipping extensional shear zone. The augen gneisses are strongly mylonitic and exhibit a moderately dipping foliation variably associated with a pronounced NNE- to NNW- trending mineral elongation lineation. The non-coaxial fabrics formed during mylomitization strongly suggest an unambiguous top-to-the-south, down-dip shear sense in a direction parallel to the south plunging stretching lineation. The mylonitic foliation was later deformed into NNE-SSW trending open folds, with axis approximately parallel to the mineral elongation lineation, which suggests that the ductile deformation was accompanied during its later stages by WNW-ESE directed compression.