Hydrogen isotopic composition and volatile contents of quartz-hosted rhyolitic melt inclusions from the early Bishop Tuff

To explore whether hydrogen isotopes can identify the source and modification of water in a silicic magma reservoir, we analyzed D/H ratios and dissolved H2O content of quartz-hosted, rhyolitic glass inclusions from the early Bishop Tuff, a time-honored testing ground for innovative petrologic studies. The rhyolitic inclusions indicate the early Bishop reservoir had δD values ranging from -40 to -60‰ (VSMOW). The rhyolitic melt represents a distinct, largely homogenous isotopic reservoir. When compared to the global record of basaltic glass inclusions, the rhyolitic inclusions preserve an isotopic signature that is most similar to subduction-related mafic melts.