The Bishop Tuff giant magma body: an alternative to the Standard Model

Gualda, G. A.; Ghiorso, Mark S.

doi:10.1007/s00410-013-0901-6

Cited by 96 publications

(132 citation statements)

References 55 publications

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“…Figure 8a in Sumita and Schmincke 2013c), suggesting that rapid recharge by less evolved magma into a higher-level body helped to trigger the rhyolitic eruptions (Sumita and Schmincke 2013c;Schmincke et al 2014). These features are consistent with the "Standard Model" of the evolution of silicic systems of Gualda and Ghiorso (2013), where a stably stratified magma chamber forms over thousands of years by crystal settling and upward migration of volatiles.…”

Section: The Nemrut Plumbing Systemsupporting

confidence: 69%

Peralkaline felsic magmatism at the Nemrut volcano, Turkey: impact of volcanism on the evolution of Lake Van (Anatolia) IV

Macdonald

Sumita

Schmincke

et al. 2015

Contrib Mineral Petrol

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Section: The Nemrut Plumbing Systemsupporting

confidence: 69%

Peralkaline felsic magmatism at the Nemrut volcano, Turkey: impact of volcanism on the evolution of Lake Van (Anatolia) IV

Macdonald

Sumita

Schmincke

et al. 2015

Contrib Mineral Petrol

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“…In contrast, recent thermodynamic modelling (Gualda et al 2012b) has led to the assertion that there was no significant thermal gradient through the Bishop Tuff magma chamber (and that in fact there existed two separate magma chambers: Gualda and Ghiorso 2013). This modelling suggests that the 'late' Bishop Tuff magma was held at ~760 °C and that there was a <30 °C gradient across the 'late' north and north-western units.…”

Section: Discussionmentioning

confidence: 96%

Timescales of mixing and mobilisation in the Bishop Tuff magma body: perspectives from diffusion chronometry

Chamberlain

Morgan

Wilson

2014

Contrib Mineral Petrol

135

173

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Abstract:We present two-feldspar thermometry and diffusion chronometry from sanidine, orthopyroxene and quartz from multiple samples of the Bishop Tuff, California, to constrain the temperature stratification within the pre-eruptive magma body and the timescales of magma mixing prior to its eruption. Two-feldspar thermometry yields estimates that agrees well with previous Fe-Ti oxide thermometry and gives a ~80 °C temperature difference between the earlier-and later-erupted regions of the magma chamber. Using this thermometry, we model diffusion of Ti in quartz, and Ba and Sr in sanidine as well as Fe-Mg interdiffusion in orthopyroxene to yield timescales for the formation of overgrowth rims on these phenocryst phases. Diffusion profiles of Ti in quartz and Fe-Mg in orthopyroxene diffusion both yield timescales of <150 years for the formation of overgrowth rims. In contrast, both Ba and Sr diffusion in sanidine yield nominal timescales 1-2 orders of magnitude longer than these two methods. The main cause for this discrepancy is inferred to be an incorrect assumption for the initial profile shape for Ba and Sr diffusion modelling (i.e., growth zoning). Utilising the divergent diffusion behaviour of Ba and Sr, we place constraints on the initial width of the interface and can refine our initial conditions considerably, bringing Ba and Sr data into alignment, and yielding timescales closer to 500 years, the majority of which are then within uncertainty of timescales modelled from Ti diffusion in quartz. Care must be thus taken when using Ba-in-sanidine geospeedometry in evolved magmatic systems where no other phases or elements are available for comparative diffusion profiling. Our diffusion modelling reveals piecemeal rejuvenation of the lower parts of the Bishop Tuff magma chamber at least 500 years prior to eruption. Timescales from our mineral profiling imply either that diffusion coefficients currently used are uncertain by 1-2 orders of magnitude, or that the minerals concerned did not experience a common history, despite being extracted from the same single pumice clasts. Introduction of the magma initiating crystallization of the contrasting rims on sanidine, quartz, orthopyroxene and zircon was prolonged, and may be a marker of other processes that initiated the Bishop Tuff eruption rather than the trigger itself. 2 AbstractWe present two-feldspar thermometry and diffusion chronometry from sanidine, orthopyroxene and quartz from multiple samples of the Bishop Tuff, California, to constrain the temperature stratification within the pre-eruptive magma body and the timescales of magma mixing prior to its eruption. Twofeldspar thermometry yields estimates that agree well with previous Fe-Ti oxide thermometry and gives a ~80 °C temperature difference between the earlier-and later-erupted regions of the magma chamber. Using this thermometry, we model diffusion of Ti in quartz, and Ba and Sr in sanidine as well as Fe-Mg interdiffusion in orthopyroxene to yield timescales for the formation of overgrowth rims on th...

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“…Finally, we use rhyolite-MELTS to calculate crystallization paths-including H 2 O and CO 2 evolution in the melt-and show how the results of modeling can be used to constrain the crystallization conditions and initial H 2 O/CO 2 ratios of natural magmas. Figure 14 shows computed saturation curves for a highsilica rhyolite composition liquid, namely an average of late-erupted glass inclusions found in quartzes from the Bishop Tuff (see Table 3 Wallace et al 1995Wallace et al , 1999 (see Gualda and Ghiorso 2013), particularly with respect to SiO 2 and Al 2 O 3 values, which makes the calculated saturation curves generally applicable to all Bishop Tuff glass inclusions plotted in Fig. 14. Solid curves in Fig.…”

Section: Applicationsmentioning

confidence: 96%

An H2O–CO2 mixed fluid saturation model compatible with rhyolite-MELTS

Ghiorso

Gualda

2015

Contrib Mineral Petrol

Self Cite

479

397

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a maximum in melt CO 2 at nonzero H 2 O melt concentrations, regardless of bulk composition. This feature is universal and can be attributed to the dominance of hydroxyl speciation at low water concentrations. The model is applied to four examples. The first involves estimation of pressures from H 2 O-CO 2 -bearing glass inclusions found in quartz phenocrysts of the Bishop Tuff. The second illustrates H 2 O and CO 2 partitioning between melt and fluid during fluid-saturated equilibrium and fractional crystallization of MORB. The third example demonstrates that the position of the quartz-feldspar cotectic surface is insensitive to melt CO 2 contents, which facilitates geobarometry using phase equilibria. The final example shows the effect of H 2 O and CO 2 on the crystallization paths of a high-silica rhyolite composition representative of the late-erupted Bishop Tuff. Software that implements the model is available at ofm-research.org, and the model is incorporated into the latest version (1.1+) of rhyolite-MELTS.

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The Bishop Tuff giant magma body: an alternative to the Standard Model

Cited by 96 publications

References 55 publications

Peralkaline felsic magmatism at the Nemrut volcano, Turkey: impact of volcanism on the evolution of Lake Van (Anatolia) IV

Peralkaline felsic magmatism at the Nemrut volcano, Turkey: impact of volcanism on the evolution of Lake Van (Anatolia) IV

Timescales of mixing and mobilisation in the Bishop Tuff magma body: perspectives from diffusion chronometry

An H2O–CO2 mixed fluid saturation model compatible with rhyolite-MELTS

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