40Ar/39Ar geochronologic data for mafic and intermediate volcanic rocks in the vicinity of Henrys Fork caldera, Yellowstone Plateau volcanic field

While the timing and composition of the Yellowstone Plateau volcanic field’s caldera-forming tuffs and rhyolite flows are well-characterized, the chronology of smaller-volume mafic eruptions is poorly known, thereby limiting our understanding of how mafic magmatism drives rhyolite volcanism, particularly Yellowstone’s large caldera-forming eruptions. To address this gap in knowledge, we measured 40Ar/39Ar ages for 13 mafic and intermediate volcanic rocks collected from within and adjacent to Henrys Fork caldera (eastern Idaho, USA), in the western portion of the Yellowstone Plateau volcanic field. Our data reveal three episodes of small-volume eruptive activity over the past ~1.2 Ma. Argon isotope analyses were conducted at the USGS facility in Menlo Park, California using an Isotopx NGX-600 multi-collector mass spectrometer or a MAP216 single-collector mass spectrometer.