TY - CONF

T1 - Primary and secondary water content heterogeneity in volcanic glasses

AU - Tuffen, Hugh

N1 - Mineralogical Magazine 75 (3), Abstract no. 2086

PY - 2011/6/10

Y1 - 2011/6/10

N2 - Spatial heterogeneities in the dissolved water content within volcanic glasses are generated by diffusive degassing and crystallization of melts, as well as subsequent posteruptive hydration of quenched glasses. Characterization ofthe resultant water diffusion gradients using micro-analytical techniques such as SIMS or synchrotron FTIR allows us to model the timescale of water diffusion and thus key pre-, synand post-eruptive processes. We present a variety of microanalytical data to illustrate three sources of water content heterogeneity within rhyolitic glasses.Firstly, enrichment of water in glass surrounding spherulites reflects its expulsion during growth of anhydrous mineral phases. Our diffusion models have placed new constraints on spherulite growth rates within obsidian flows [1]. Secondly, we have found strong water enrichment adjacent to perlitic fractures in subglacially erupted obsidian lavas [2]. Diffusion and cooling models show that perlitisationstarts at ~400 °C and occurs over timescale of days [3].Finally, we have used SIMS analysis to overcome the hydration problem and successfully measure the dissolved magmatic water content of pumices [4]. This provides new insight into magma storage and degassing prior to anexceptionally violent eruption.

AB - Spatial heterogeneities in the dissolved water content within volcanic glasses are generated by diffusive degassing and crystallization of melts, as well as subsequent posteruptive hydration of quenched glasses. Characterization ofthe resultant water diffusion gradients using micro-analytical techniques such as SIMS or synchrotron FTIR allows us to model the timescale of water diffusion and thus key pre-, synand post-eruptive processes. We present a variety of microanalytical data to illustrate three sources of water content heterogeneity within rhyolitic glasses.Firstly, enrichment of water in glass surrounding spherulites reflects its expulsion during growth of anhydrous mineral phases. Our diffusion models have placed new constraints on spherulite growth rates within obsidian flows [1]. Secondly, we have found strong water enrichment adjacent to perlitic fractures in subglacially erupted obsidian lavas [2]. Diffusion and cooling models show that perlitisationstarts at ~400 °C and occurs over timescale of days [3].Finally, we have used SIMS analysis to overcome the hydration problem and successfully measure the dissolved magmatic water content of pumices [4]. This provides new insight into magma storage and degassing prior to anexceptionally violent eruption.

M3 - Conference paper

SP - 2038

T2 - Goldschmidt Conference

Y2 - 14 August 2011 through 19 August 2011

ER -