High temperature mass spectrometric gas-release studies of Hawaiian volcanic glass: Pele's tears

Abstract

The identification of gaseous molecular species and mechanisms of their release from glassy lava have been investigated with a high temperature mass spectrometer. Using Pele's tears as representative of quenched liquids of Hawaiian tholeiitic basalts, it was found that volatiles are released at low temperatures by a rate-limiting diffusion mechanism and, at temperatures in the softening range of the glass, by bursting of bubbles trapped near the vaporizing surface of the sphere-like particles. Gases released by bursting gave pressure surges and were found to be water vapor, CO 2 and CO. Those released principally by diffusion, and in some cases generated by thermal degradation and further reaction with the sample, include H 2, O 2, N 2, S 2, H 2S, SO 2, SO 3, COS, HCl, HF and NH 3. Average mole percent compositions of the volatiles H 2O, CO 2 and SO 2 relative to the total gas released were found to be 95 per cent, 3·5 per cent and 1 per cent, respectively. Minor concentrations of organic constituents, previously unobserved in volcanic gas analyses, were also found. Fragmentation patterns and gas release behavior suggest that these are derived from a mixture of low-molecular weight saturated and unsaturated acyclic hydrocarbons (C 1-C 4).