Stable chlorine isotope behavior during volcanic degassing of H2O and CO2 at Mono Craters, CA

Barnes, Jaime D.; Prather, Timothy; Cisneros, Miguel; Befus, Kenneth S.; Gardner, James E.; Larson, Toti E.

doi:10.1007/s00445-014-0805-y

Cited by 27 publications

(37 citation statements)

References 63 publications

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“…δD composition measurements of lava dome fragments and pumice clasts from the P1 eruption exclude significant contribution of meteoric water in this material 16 . Similar isotopic data on obsidian clasts from fallout deposits, lava domes and flows from the Western United States show that total water content is controlled by degassing processes in such samples of similar composition 48 49 .…”

Section: Methodsmentioning

confidence: 59%

What factors control superficial lava dome explosivity?

Boudon

Balcone-Boissard

Villemant

et al. 2015

Sci Rep

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Dome-forming eruption is a frequent eruptive style and a major hazard on numerous volcanoes worldwide. Lava domes are built by slow extrusion of degassed, viscous magma and may be destroyed by gravitational collapse or explosion. The triggering of lava dome explosions is poorly understood: here we propose a new model of superficial lava-dome explosivity based upon a textural and geochemical study (vesicularity, microcrystallinity, cristobalite distribution, residual water contents, crystal transit times) of clasts produced by key eruptions. Superficial explosion of a growing lava dome may be promoted through porosity reduction caused by both vesicle flattening due to gas escape and syn-eruptive cristobalite precipitation. Both processes generate an impermeable and rigid carapace allowing overpressurisation of the inner parts of the lava dome by the rapid input of vesiculated magma batches. The relative thickness of the cristobalite-rich carapace is an inverse function of the external lava dome surface area. Explosive activity is thus more likely to occur at the onset of lava dome extrusion, in agreement with observations, as the likelihood of superficial lava dome explosions depends inversely on lava dome volume. This new result is of interest for the whole volcanological community and for risk management.

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Section: Methodsmentioning

confidence: 59%

What factors control superficial lava dome explosivity?

Boudon

Balcone-Boissard

Villemant

et al. 2015

Sci Rep

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“…The 1 GSA Data Repository item 2017049, details on sample information and processing, cooling rates, and diffusion modeing, is available online at www .geosociety.org /pubs /ft2017.htm, or on request from editing@geosociety.org. tephra section sampled for this study consists of soil at the base, overlain by 10 well-sorted lapilli layers that are rich in pumice clasts and less common obsidian clasts, interbedded with well-sorted ash-fall beds (Barnes et al, 2014). Pyroclastic obsidian clasts were collected from four of the coarser lapilli layers, including layers from near the base to near the top.…”

Section: Geological Context Of Samplesmentioning

confidence: 99%

“…We selected eight obsidian clasts that collectively span the observed range of volatile contents (Barnes et al, 2014) and collected area maps of CO 2 and H 2 O concentrations by Fourier transform infrared spectroscopy (see the Data Repository). We also made measurements of hydrous speciation (H 2 O m and OH, where m denotes molecular water), which yield cooling rates for six of the eight clasts that are consistent with glass formation by air quench as opposed to slow cooling in the subsurface (see the Data Repository).…”

Section: Geological Context Of Samplesmentioning

confidence: 99%

“…Many of the ideas that underlie magmatic degassing models can be traced back to chemical analyses of dense, nearly bubble-free obsidian fragments from the A.D. 1340 eruption sequence at Mono Craters, California, USA (black circles in Fig. 1A; Taylor et al, 1983;Newman et al, 1988;Dobson et al, 1989;Rust et al, 2004;Barnes et al, 2014). A key observation is that CO 2 /H 2 O ratios are higher than what would be expected from simple closed-or open-system degassing of a single parental melt (solid curves in Fig.…”

Section: Introductionmentioning

confidence: 99%

“…Yoshimura and Nakamura, 2011), new types of measurements are needed to test the different degassing models and to guide future modeling developments. Many of the previous measurements are based on single (or a few) spot analyses of vesicle-and crystal-free regions of the clasts (Newman et al, 1988;Rust et al, 2004;Barnes et al, 2014). While this avoids complications that can be introduced by analyzing domains of a sample with different physical properties (see the GSA Data Repository 1 ; von Aulock et al, 2014), it may be overlooking small-scale heterogeneities.…”

Section: Introductionmentioning

confidence: 99%

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Nonequilibrium degassing, regassing, and vapor fluxing in magmatic feeder systems

Watkins

Gardner

Befus

2017

Geology

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Magma degassing models typically invoke volatile depletion of a single parental melt, with permeable loss of exsolved gas having served for many years as the paradigm for the transition from volatile-rich, explosive eruptions to volatile-depleted lava flows. These degassing models are guided by measurements of H 2 O, CO 2 , and hydrogen isotope variations retained in melt that quenched to glass, but the existing models are not uniquely constrained by the data. There also remains uncertainty surrounding the origin and significance of volcanic glass fragments. We show that individual obsidian pyroclasts from Mono Craters, California (USA), are heterogeneous in dissolved H 2 O and CO 2 , suggesting that clasts are assembled from juvenile melt and rewelded ash during magma ascent. This is in contrast to the conventional view that clasts are chemically homogeneous and sample the chilled, glassy margins of conduit walls. The new measurements of dissolved H 2 O and CO 2 help reconcile existing open-system degassing models used to explain elevated CO 2 /H 2 O ratios, provide time scales based on diffusion modeling for pyroclast formation, and show that magma does not necessarily lose volatiles monotonically during ascent-driven decompression.

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