Phase Petrology and Mineral Chemistry of Coexisting Amphiboles from Telemark, Norway |
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Authors: | STOUT JAMES H |
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Institution: | Department of Geological Sciences, Harvard University Cambridge, Massachusetts 02138
1 Present address: Department of Geology, and Geophysics, University of Minnesota, Minneapolis 5545. |
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Abstract: | Electron microprobe analyses of coexisting amphiboles, garnet,and cordierite in specimens collected from a single outcropprovide the basis for phase diagrams thought to be representativeof fixed external conditions in the sillimanite zone. A projectionthrough the compositions of quartz and plagioclase is employedto characterize the mineral facies and to facilitate comparisonswith other metamorphic terrains. Limiting recalculations whichbracket the possible range of Fe+3 contents in calcic amphiboleanalyses by electron probe permit an additional projection throughthe composition of magnetite, a ubiquitous phase. From thesedata the apparent non-ideality exhibited by various combinationsof coexisting cumming-tonite, anthophyllite, gedrite, and calcicamphibole is explained by intracrystalline cation ordering. |
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