New Mineralogic Data and Implications for the Tectonometamorphic Evolution of the Alanya Nappes, Central Tauride Belt, Turkey

Abstract

The Alanya Unit, consisting of three nappes, crops out in the Demirtas-Anamur area of the Tauride Belt and is related to the Alpine orogeny. The Mahmutlar nappe of Permian and pre-Permian age progressively evolved as indicated by 2M1 white K-mica, Mg-chlorite, and 1M biotite which are related to increasing metamorphism from its upper (phyllite, metasiltstone) to lower parts (biotite schist, staurolite-kyanite-garnet-mica schist). The b values of the white K-micas are characterized by a facies series of medium- to high-pressure metamorphism. The Sugözü nappe comprises garnet-mica schist with metabasite (eclogite, glaucophane schist) interbands and/or lenses composed of muscovite, chlorite, and rarely paragonite and illite-smectite. The crystallinity and b values of phengitic micas in the metapelites represent epizonal and medium-pressure facies conditions. The Yumrudag nappe of Pre-Permian-Triassic age is characterized by index minerals, such as chloritoid, paragonite, kaolinite/dickite, 1Tc pyrophyllite, and margarite. Epizonal 2M1 white K-micas with low b values indicate lower-pressure metamorphism. The mineralogic and geochemical signatures of these metasedimentary rocks indicate that the nappes were predominantly derived from different sources. The Mahmutlar nappe developed under a Barrovian-type, regional dynamothermal progressive metamorphism. The Sugözü nappe records an earlier high-pressure/low-temperature metamorphism that has been overprinted—together with the structurally overlying Mahmutlar nappe—by a later Barrovian metamorphic event. The Yumrudag nappe, on the other hand, is characterized by a metamorphic evolution with a typical counterclockwise P-T-t path in an extensional basin, such as those of the northern allochthonous Tauride units, indicating that its southward emplacement onto the other nappes was relatively late.