Rhyolitic and basaltic reference materials for TC/EA analysis: Investigation of water extraction and D/H ratios

Increasingly, water and D/H ratios of silicic and basaltic glasses are used to investigate magmatic degassing and secondary hydration, as well as for study these parameters in the mantle and crustal magmas. The advent of the High Temperature Conversion Element Analyzer (TC/EA) continuous (f)low mass spectrometry made the determination of hydrogen isotopes relatively quick and precise (+/- 0.04 wt% H4(2)O and 1-3 parts per thousand (delta H-2). Many labs around the world have such systems, thus there is a need to develop both silicic and basaltic volcanic glass reference materials (RMs) that can be used for interlaboratory comparison by bulk and microanalytical methods. Here, we report results of such investigation run against solid RMs (USGS micas) and water RMs (including VSMOW) in three different labs and describe analytical protocols. We report on the effects of glass size fraction, the mass of aliquots measured, and yield dependency for two glasses: UOR (drill cutting of IDDP-1 rhyolite, Iceland) and UOB (an E-MORB basalt from the East Pacific Rise). Proposed RM values are: UOB rhyolitic glass (n = 31): H2O = 1.84 4 +/- 0.06 wt%(1 s.d.), and delta H-2 = -115.5 +/- 2.6 parts per thousand(1 s.d.) UOB basaltic glass (n = 60): H2O = 0.37 4 +/- 0.03 wt%(1 s.d.), and delta H-2 = - 82.1 +/- 5.7 parts per thousand(1 s.d.) Glass reference materials are available in 100 mg quantities from the Stable Isotope Laboratory at the University of Oregon for a nominal fee.

Automated summary

Water and D/H ratios in silicic and basaltic glasses are used for investigating magmatic degassing and secondary hydration in mantle and crustal magmas. The use of the TC/EA mass spectrometry has made the determination of hydrogen isotopes relatively quick and precise. Developing reference materials for both types of glasses is important for inter-laboratory comparisons.