Incipient blueschist metamorphism and metasomatism in the Tav?anli region,Northwest Turkey |
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| Authors: | A I Okay |
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| Institution: | (1) Department of Earth Sciences, Downing Place, CB2 3E Cambridge, England;(2) Present address: Temel Ara tirmalar, Mineral Research and Exploration Institute (MTA), Ankara, Turkey |
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| Abstract: | Volcano-sedimentary rocks in an imbricate tectonic zone around a peridotite massif have been studied northeast of the town of Tav anli in Northwest Turkey. Basic volcanic rocks, which are the dominant rock type in this zone, show incipient blueschist metamorphism and associated metasomatism. While the igneous textures of the volcanic rocks are retained, augites are partially to completely replaced by sodic pyroxene, and plagioclase is albitised resulting in rocks with 6–8 wt.% Na2O. The volcanic rocks are cross-cut by numerous veins of calcite, aragonite, quartz, pumpellyite, albite, lawsonite and sodic pyroxene. Pelagic limestones, which are interbedded with the basic volcanic rocks, consist of coarse aragonite grains showing partial replacement by calcite. The occurrence of aragonite, lawsonite and albite indicates conditions of metamorphism for the whole zone in the range of 5–8 kb and 150–200° C. Metasomatism, probably related to high pressure serpentinization, has occurred contemporaneously with the incipient high pressure metamorphism. |
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