This data release includes electron microprobe and 40Ar/39Ar data collected at the U.S. Geological Survey for samples from the Raft River metamorphic core complex in Utah, USA. Rock samples were collected by Raphael Gottardi, currently at Auburn University. Muscovite in thin sections from quartzites, micaceous quartzites, and quartz-kyanite rocks were analyzed by electron probe microanalysis at the U.S. Geological Survey, Reston Electron Microbeam Laboratory. Muscovite and K-feldspar from the same suite of rocks were analyzed by 40Ar/39Ar geochronology at the U.S. Geological Survey Bascom ARgon Dating (BARD) Laboratory in Reston, Virginia.