Table 1 Volatile concentrations in MI and MG, expected fluid-absent concentrations in evolved MI, and Δvolatile values for pre- and syn-eruptive fluids.

U concentration is used as an index of differentiation. All analyses are in parts per million, unless noted. Numbers in parentheses represent 1σ uncertainty in units of the last reported digits. H2O and CO2 are measured by transmission or ATR FTIR. S, F, and U are measured by SHRIMP. Cl is measured by EMP. n, number of MI averaged.

Trachyte MI average
concentration
nComendite MI
average
concentration
nMG
average
concentration
Expected
fluid-absent
concentration
ΔVolatile
(pre-eruptive)
ΔVolatile
(syn-eruptive)
H2O wt %1.72 (24)132.40 (23)370.3 (15)6.183.782.10
S197 (5)35110 (3)5359 (1)90579551
F917 (28)353354 (104)533128 (97)4220896226
Cl987 (53)413974 (215)734166 (225)45300
CO223 (2.6)*90
U2.3 (1)4110.7 (7)7310 (6)

*Measured in rehomogenized bubble-bearing MI (see Materials and Methods).