Single and multiphase inclusions in metapelitic garnets of the Rhodope Metamorphic Province, NE Greece.

Marius E Mayerhoefer, Georgios Karanikas, Kurt Kletter, Helmut Prosch, Barbara Kiesewetter, Cathrin Skrabs, Edit Porpaczy, Michael Weber, Thomas Knogler, Christian Sillaber, Ulrich Jaeger, Ingrid Simonitsch-Klupp, Philipp Ubl, Leonhard Müllauer, Werner Dolak, Julius Lukas, Markus Raderer

Index: Spectrochim. Acta. A. Mol. Biomol. Spectrosc. 73(3) , 477-83, (2009)

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Abstract

Single and multiphase inclusions in garnet porphyroblasts from the diamond-bearing pelitic gneisses were studied by means of combined Raman Spectroscopy and Electron Scanning Microscopy (SEM/EDX). They are either randomly distributed or with preferred orientation within the garnet host and their dimensions vary from less than 5 up to 60 microm. In the single-phase inclusions quartz, rutile, kyanite and graphite dominate. Biotite, zircon, apatite, monazite and allanite are also common. Two types of multiphase inclusions were recognized, hydrous silicate (Type I) and silicate-carbonate (Type II) ones. The carbon-bearing multiphase inclusions predominantly consist of Mg-siderite+graphite+CO(2)+muscovite+quartz formed by a high density carboniferous fluid rich in Fe, Mg, Si and less Ca, Mn, Al and K trapped in the growing garnet in a prograde stage of metamorphism at high-pressure (HP) conditions. The carbon-free multiphase inclusions predominantly consist of biotite+quartz+rutile+/-kyanite+muscovite formed through decompression-dehydration/melting reactions of pre-existing phengite. Single and multiphase inclusions are characterized by polygonal to negative crystal shape formed by dissolution-reprecipitation mechanism between the garnet host and the inclusions during the long lasting cooling period (>100 Ma) of the Kimi Complex.