Granulite Facies Gneisses from the Pulur Region, Eastern Pontides

Authors: Aral I. OKAY

Abstract: In the Pulur region in the Eastern Pontides a metamorphic basement outcrops under the Jurassic-Cretaceous sequence. The metamorphic rocks are divided into two tectonic units. At the base is the Hasso Group of greenschist facies metatuffs and phyllites, which are tectonically overlain by the Cenci Group of gneiss, migmatite, metaquartzite, amphibolite and variably deformed granitic rocks. The metapelitic gneisses of the Cenci Group contain the granulite facies mineral assemblage of cordierite + garnet + sillimanite + biotite + K-feldspar + plagioclase + quartz. Mineral equilibria in this assemblage indicate P-T conditions of 730 ± 50¼C and 5 ± 0.5 kbar for the regional metamorphism. Regional tectonic considerations indicate that the granulite facies metamorphism is probably of Late Devonian age. In contrast, the Hasso Group can be compared with the Agvanis Massif of probable late Triassic metamorphic age, which forms part of the Karakaya Complex and is located 90 km southwest of the Pulur metamorphic rocks. The tectonic juxtaposition of the two groups must have occurred during the latest Triassic Cimmeride orogeny.

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