Textural evolution and partial melting of arkose in a contact aureole: a case study and implications |
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Authors: | John D Clemens and Marian B Holness |
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Institution: | (1) School of Geological Sciences, CEESR, Kingston University, Penrhyn Rd, Kingston-upon-Thames, Surrey, KT1 2EE, UK;(2) Dept of Earth Sciences, University of Cambridge, Downing St, Cambridge, CB2 3EQ, UK |
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Abstract: | Recognition of partial melting in metamorphic rocks is a difficult task, as leucosomes can have a variety of origins. By comparing the observed values of the solid-solid dihedral angles with the known equilibrium values, and close examination of the shapes and compositions of feldspar grains, it is possible to unequivocally identify melt textures. Textural relations in a series of meta-arkose samples from the contact aureole of the Ballachulish Igneous Complex in the Scottish Highlands demonstrate that, when former melt pockets are not highly deformed, their presence can be recognized petrographically, by detailed examination of textures on the grain scale. Identification of melt textures and their distribution in the Ballachulish aureole has led to appreciation of the fundamental role of magmatically derived H2O in producing the partial melting. It has also allowed calculation of the H2O flux involved, and recognition that fractures were the major fluid pathways during metamorphism. |
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Keywords: | textures partial melting contact metamorphism contact aureole Ballachulish |
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