Phase-equilibrium geobarometers for silicic rocks based on rhyolite-MELTS. Part 4: Plagioclase, orthopyroxene, clinopyroxene, glass geobarometer, and application to Mt. Ruapehu, New Zealand

Experimental Constraints on Magma Storage Conditions of Two Caldera‐Forming Eruptions at Towada Volcano, Japan

“…In contrast, plagioclase‐in and orthopyroxene‐in curves intersect at 800–840°C and 195–400 MPa in the pressure range investigated (25–400 MPa) under relatively reducing and water‐rich conditions (5–6 wt.% H 2 O at NNO). The lack of a constraint from clinopyroxene may have resulted in the large uncertainties in our pressure estimate (Harmon et al., 2018). It is known that rhyolite‐MELTS poorly predicts the stability of minor mafic minerals such as iron–titanium oxides, pyroxenes, biotite, and amphibole in rhyolitic magmas (Gardner et al., 2014; Gualda et al., 2012), which may strongly influence the saturation of orthopyroxene and particularly clinopyroxene in our calculations.…”

“…Coexistence of plagioclase + orthopyroxene + clinopyroxene with melt in our samples may allow us to use the phase equilibria geobarometer proposed by Harmon et al (2018). This geobarometer utilizes rhyolite-MELTS to determine the magma storage conditions under which the melt having measured matrix glass compositions becomes simultaneously saturated with plagioclase and two pyroxenes.…”

The Whakamaru magmatic system (Taupō Volcanic Zone, New Zealand), part 1: Evidence from tephra deposits for the eruption of multiple magma types through time

“…We use a combination of 1) field observations and sampling, 2) major-and trace-element compositions of glass in tephra clasts, 3) zircon EarthArXiv pre-print. This article has been peer-reviewed and accepted by the Journal of Volcanology and Geothermal Research saturation geothermometry (Watson and Harrison, 1983;Boehnke et al, 2013), and 4) geobarometry via rhyolite-MELTS Ghiorso 2012a, 2015;Gualda et al, 2014;Bégué et al, 2014b;Pamukçu et al, 2015b;Harmon et al, 2018) to determine the changes in volcanological deposition through time, the number and compositions of melt-dominated magma bodies, and the storage conditions of the melt-dominated magma bodies. A total of 146 clasts were analyzed in this study for major-and trace-element glass compositions, with five to six of the largest, pristine juvenile clasts chosen from each horizon.…”

Thermobar: An open-source Python3 tool for thermobarometry and hygrometry

“…Based on the complexities associated with the local installation of thermodynamic software tools, we also don't provide calculation tools for geothermobarometers developed using rhyoliteMELTS as a framework [e.g. Gualda and Ghiorso 2014;Harmon et al 2018], thermodynamic models of Fe-Ti oxides relying on ThermoEngine, [Ghiorso and Prissel 2020], or thermobarometers used heavily within the field of metamorphic petrology (e.g. Thermocalc, Perple-X, THERIAK-DOMINO [Powell et al 1998;Connolly and Petrini 2002;de Capitani and Petrakakis 2010]).…”