Metamorphism during Alpine crustal thickening and extension in Central Anatolia, Turkey: the Nigde metamorphic core complex

Abstract

The Nigde massif, a metamorphic core complex in Central Anatolia (Turkey), contains petrologic evidence for the transition from Alpine crustal thickening to extension and exhumation of high-grade mid-crustal rocks. Sillimanite-potassium feldspar gneiss formed and partially method during Barrovian metamorphism and records maximum conditions of 5-6 kbar, <700°C. The two-mica Uckapth granite and a related dike suite intruded the migmatitic metapelitic rocks, forming a contact aureole that contains andalusite and cordierite. These low-pressure minerals indicate that crustal thickening was followed by exhumation of mid-crustal rocks to relatively shallow depths (<10 km) at lower temperatures before the emplacement of granitic magma. Formation of andalusite was followed by a second, prograde episode of sillimanite growth during low-P-high-T metamorphism in the central part of the massif, where magmatism was most extensive. A generalized P-T path for the highest grade rocks therefore consists of an initial clockwise path with a late thermal spike and characterizes burial and subsequent exhumation accompanied by magmatism.