Nucleation delay in water-saturated rhyolite during decompression in shallow volcanic systems and its implications for ascent dynamics

Abstract

We developed a model of feldspar nucleation delay during decompression in water-saturated rhyolite based on classical nucleation theory (CNT). With the thermodynamic and kinetic parameters proposed in this study, the model agrees with the experimental results of this study to within a factor of two. To account for the variety of conditions encountered by magma during ascent, we propose expanding the model, developed in this study for isothermal decompression, to a wider range of pressures and temperatures (i.e., non-isothermal conditions). We present new measurements of feldspar growth rates during decompression in water-saturated rhyolite, emphasizing the importance of accurately calculating the nucleation delay in order to estimate growth rates. Using these data, we propose a method for estimating the ascent rate of water-saturated rhyolite based on the nucleation delay of feldspar microlites.The findings of this study hold the promise of a better understanding of volcanic timescales during magma ascent in the conduit, as well as the possibility of extending our model to more complicated scenarios with changing pressure and temperature.

Quantification of Feldspar and Quartz Nucleation Delay in a Hydrous Peraluminous Granitic Melt

“…Indeed, we suggest that nucleation delay in many common magmatic melts can now be modeled by combining classical nucleation theory [2], thermodynamic models of plagioclase, quartz, olivine, and clinopyroxene crystallization [61], our knowledge of Si-Al interdiffusion in silicate melts, and silicate-melt interfacial energies [13]. Although these calculated delays may not be exact, a combination of the nucleation delay time with detailed petrographic observations may provide important constraints on the times available for crystallization during processes such as intrusion of a hot magma into cold country rocks, extrusion on to the surface of a planet, ascent and undercooling of hydrous magmas in magmatic conduits, and any other magmatic process where a magma is rapidly cooled to subliquidus conditions (e.g., [5,25]).…”

“…Multiple variations of Equation ( 3) have been derived; each variant of the equation provides a slightly different estimate of the nucleation delay (e.g., [55][56][57][58]). Equation ( 3) was chosen for this study because of its previously demonstrated success in the prediction of nucleation delay times [5,25,59].…”

“…This research on nucleation delay improves our understanding of granitic systems, providing quantitative and qualitative models that describe the magmatic timescales and crystallization mechanisms responsible for their formation. Furthermore, additional knowledge of nucleation delay can also help constrain the timescales of magma ascent rates and volcanic eruptions [25].…”

Crystal habit (tracht) of groundmass pyroxene crystals recorded magma ascent paths during the 2011 Shinmoedake eruption

“…DOI: https://doi.org/10.2138/am-2022-8765. http://www.minsocam.org/ 2013; Polacci et al 2018;Le Gall et al 2021;Arzilli et al 2022), nucleation delay (Arzilli et al 2020;First et al 2020;Rusiecka et al 2020;Rusiecka and Martel 2022), and crystal growth in real time (Polacci et al 2018;Arzilli et al 2019Arzilli et al , 2022Le Gall et al 2021).…”