Multiphase solid inclusions in orogenic peridotites as tracers of metasomatism in collisional orogens
Orogenic peridotites exposed in UHP terranes in collisional orogens record metasomatism by fluids derived from the subducting slab. Multiphase solid inclusions (MSI) trapped in their peak minerals, mostly garnet, record information on physical and chemical composition of these deep fluids. We focus on MSI in garnet peridotites and pyroxenites in the Bohemian Massif (European Variscan Belt) to test the hypothesis that mantle metasomatism in hot orogens is a multiphase process, facilitated by percolating supercritical melts of mixed crust-mantle origin (now garnetpreserved as pyroxenite veinss). To achieve that, we will reconstruct bulk chemical composition of the well-preserved MSI. We will also along with use high-resolution analytical techniques to measure specify contents of halideschemical composition including major and and trace elements and C, O, Cl, resp. Sr isotope composition MSI constituents (silicates, graphite, carbonates, apatite) as proxies for distinction of the source of metasomatizing agents. P-T-t constraints on formation and metasomatism will be also provided using thermodynamic modelling and different geochronological methods, Lu-Hf dating, and in-situ U-(Th)-Pb dating of garnet and Th-U phases.
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