Mineralogy and Geochemistry of Garnet Rhyolites, Black Hills, South Dakota
Hooper, Robert L.
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This study is looking at the mineralogy of the garnet bearing rhyolites to determine the origin of the garnets and other associated minerals. Thin sections are being examined using SEM/EDS. Initial results suggest the garnets are igneous phenocrysts, they are free of inclusions of metamorphic minerals, and are associated with ferro-knebelite (Mn-olivine), quartz, fluorine-rich biotite, anorthoclase, plagioclase (~An 30) and thorium-rich monazites. Continued study of this suite of rocks should allow us to determine more about the igneous history of these rhyolite intrusions.
Black Hills (South Dakota)