Abstract
In this paper, we present boron isotope analy- ses of variably degassed rhyolitic glasses from Long Valley, California. The following results indicate that pre-eruptive boron isotopic signatures were preserved in degassed glasses: (1) averaged secondary ionization mass spectrometry (SIMS) measurements of H2O-rich (� 3 wt%) melt inclusions from late erupted Bishop Tuff pumice are indistinguishable from positive thermal ionization mass spectrometry (PTIMS) analysis of vesiculated groundmass glass (d 11 B=+5.0±0.9& and +5.4±0.5&, respectively); (2) SIMS spot-analyses on H2O-poor obsidian (� 0.15 wt% H2O) from younger Glass Mountain Dome YA (average d 11 B=+5.2±1.0&) overlap with compositionally similar late Bishop Tuff melt inclusions; and (3) four variably degassed obsidian samples from the 0.6 ka Mono Craters (H2O between 0.74 and 0.10 wt%) are homogeneous with regard to
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
