Rare eclogite‐mafic granulite in felsic granulite in Blanský les: precursor of intermediate granulite in the Bohemian Massif? |
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| Authors: | P ?típská R Powell M Racek |
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| Institution: | 1. Czech Geological Survey, Center for Lithospheric Research, , 11821 Praha 1, Czech Republic;2. Ecole et Observatoire des Sciences de la Terre, Institut de Physique du Globe, CNRS UMR 7516, Université de Strasbourg, , F‐67084 Strasbourg Cedex, France;3. School of Earth Sciences, University of Melbourne, Melbourne, , Victoria, 3010 Australia;4. Institute of Petrology and Structural Geology, Charles University, , 12843 Praha 2, Czech Republic;5. Czech Geological Survey, Regional Geology of Crystalline Complexes Department, , 1182 1 Praha 1, Czech Republic |
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| Abstract: | Mafic granulite, generated from eclogite, occurs in felsic granulite at Kle?, Blanský les, in the Bohemian Massif. This is significant because such eclogite is very rare within the felsic granulite massifs. Moreover, at this locality, strong interaction has occurred between the mafic granulite and the adjacent felsic granulite producing intermediate granulite, such intermediate granulite being of enigmatic origin elsewhere. The mafic granulite involves garnet from the original eclogite, containing large idiomorphic inclusions of omphacite, plagioclase and quartz, as well as rutile. The edge of the garnet is replaced by a plagioclase corona, with the garnet zoned towards the corona and also the inclusions. The original omphacite–quartz–?plagioclase matrix has recrystallized to coarse‐grained polygonal (‘equilibrium’‐textured) plagioclase‐diopsidic clinopyroxene–orthopyroxene also with brown amphibole commonly in the vicinity of garnet. Somewhat larger quartz grains are embedded in this matrix, along with minor ilmenite, rutile and zircon. Combining the core garnet composition with core inclusion compositions gives a pressure of the order of 18 kbar from assemblage and isopleths on a P?T pseudosection, with temperature poorly constrained, but most likely >900 °C. From this P?T pseudosection, the recrystallization of the matrix took place at ~12 kbar, and from Zr‐in‐rutile thermometry, at relatively hot conditions of 900–950 °C. It is largely at these conditions that the eclogite/mafic granulite interacted with the felsic granulite to make intermediate granulite (see next paper). |
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| Keywords: | Bohemian Massif eclogite mafic granulite Zr‐in‐rutile thermometry |
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