Rhyolite-MELTS: a Modified Calibration of MELTS Optimized for Silica-rich, Fluid-bearing Magmatic Systems

Gualda, G. A.; Ghiorso, Mark S.; Lemons, Robin V.; Carley, Tamara L.

doi:10.1093/petrology/egr080

Cited by 1,082 publications

(799 citation statements)

References 34 publications

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“…Note that absolute deviations for all calibration data relative to P-T values predicted by the model @Thomas et al, 2010; equation~9!# average 60.9 kbar and 6208C, respectively. For natural samples, a TiO 2 is calculated using the Rhyolite-MELTS program RMELTS; Gualda et al, 2012!, and Table 3. Also, for comparison, if all experiments of Thomas et al~2010!…”

Section: Resultsmentioning

confidence: 99%

A Study of Cathodoluminescence and Trace Element Compositional Zoning in Natural Quartz from Volcanic Rocks: Mapping Titanium Content in Quartz

et al. 2012

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Abstract:This article concerns application of cathodoluminescence~CL! spectroscopy to volcanic quartz and its utility in assessing variation in trace quantities of Ti within individual crystals. CL spectroscopy provides useful details of intragrain compositional variability and structure but generally limited quantitative information on element abundances. Microbeam analysis can provide such information but is time-consuming and costly, particularly if large numbers of analyses are required. To maximize advantages of both approaches, natural and synthetic quartz crystals were studied using high-resolution hyperspectral CL imaging~1.2-5.0 eV range! combined with analysis via laser ablation inductively coupled plasma mass spectrometry~LA-ICPMS!. Spectral intensities can be deconvolved into three principal contributions~1.93, 2.19, and 2.72 eV!, for which intensity of the latter peak was found to correlate directly with Ti concentration. Quantitative maps of Ti variation can be produced by calibration of the CL spectral data against relatively few analytical points. Such maps provide useful information concerning intragrain zoning or heterogeneity of Ti contents with the sensitivity of LA-ICPMS analysis and spatial resolution of electron microprobe analysis.

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Section: Resultsmentioning

confidence: 99%

A Study of Cathodoluminescence and Trace Element Compositional Zoning in Natural Quartz from Volcanic Rocks: Mapping Titanium Content in Quartz

et al. 2012

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“…These thermometry calculations have utilised Fe-Ti oxides (Hildreth, 1977(Hildreth, , 1979Hildreth and Wilson 2007;Evans and Bachmann 2013), Ti concentrations in quartz Thomas et al 2010;Thomas and Watson 2012;Wilson et al 2012), Ti concentrations in zircon (Reid et al 2011;Chamberlain et al 2014), 18 O fractionation between crystal phases (Bindeman and Valley 2002), and 2-pyroxene compositions (Hildreth 1979;Frost and Lindsley 1992) all of which yield ~100 °C temperature difference between upper and lower regions in the magma chamber. In contrast, thermodynamic modelling of the Bishop Tuff system has been used to propose a very uniform temperature range (Gualda et al 2012b). Calculations for thermometry can be somewhat limited as they often involve assumptions about the uniformity of pre-eruptive melt conditions (e.g.…”

Section: Discussionmentioning

confidence: 99%

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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“…We used the melt inclusion data above to perform MELTS modelling (Gualda et al 2012), allowing us to integrate information from both the mineralogy and the melt inclusions. We modelled three separate processes, using a representative whole-rock composition (Sample 61: a trachybasaltic lava bomb from Batch 2-we also carried out models with Sample 12 from Batch 1, but the differences were minor) and 1.29 wt% dissolved H 2 O (consistent with the most primitive vapour-saturated inclusion).…”

Section: Melts Modellingmentioning

confidence: 99%

The 2011 eruption of Nabro volcano, Eritrea: perspectives on magmatic processes from melt inclusions

Donovan

Blundy

Oppenheimer

et al. 2017

Contrib Mineral Petrol

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The 2011 eruption of Nabro volcano, Eritrea, produced one of the largest volcanic sulphur inputs to the atmosphere since the 1991 eruption of Mt. Pinatubo, yet has received comparatively little scientific attention. Nabro forms part of an off-axis alignment, broadly perpendicular to the Afar Rift, and has a history of large-magnitude explosive silicic eruptions, as well as smaller more mafic ones. Here, we present and analyse extensive petrological data obtained from samples of trachybasaltic tephra erupted during the 2011 eruption to assess the pre-eruptive magma storage system and explain the large sulphur emission. We show that the eruption involved two texturally distinct batches of magma, one of which was more primitive and richer in sulphur than the other, which was higher in water (up to 2.5 wt%). Modelling of the degassing and crystallisation histories demonstrates that the more primitive magma rose rapidly from depth and experienced degassing crystallisation, while the other experienced isobaric cooling in the crust at around 5 km depth. Interaction between the two batches occurred shortly before the eruption. The eruption itself was likely triggered by recharge-induced destabilisation of vertically extensive mush zone under the volcano. This could potentially account for the large volume of sulphur released. Some of the melt inclusions are volatile undersaturated, and suggest that the original water content of the magma was around 1.3 wt%, which is relatively high for an intraplate setting, but consistent with seismic studies of the Afar plume. This eruption was smaller than some geological eruptions at Nabro, but provides important insights into the plumbing systems and dynamics of off-axis volcanoes in Afar.

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Rhyolite-MELTS: a Modified Calibration of MELTS Optimized for Silica-rich, Fluid-bearing Magmatic Systems

Cited by 1,082 publications

References 34 publications

A Study of Cathodoluminescence and Trace Element Compositional Zoning in Natural Quartz from Volcanic Rocks: Mapping Titanium Content in Quartz

A Study of Cathodoluminescence and Trace Element Compositional Zoning in Natural Quartz from Volcanic Rocks: Mapping Titanium Content in Quartz

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

The 2011 eruption of Nabro volcano, Eritrea: perspectives on magmatic processes from melt inclusions

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