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1. Textural and geochemical window into the IDDP-1 rhyolitic melt, Krafla, Iceland, and its reaction to drilling

   https://doi.org/10.1130/B35598.1  

   Saubin, E. ; Kennedy, B. ; Tuffen, H. ; Nichols, A.R.L. ; Villeneuve, M. ; Bindeman, I. ; Mortensen, A. ; Schipper, C.I. ; Wadsworth, F.B. ; Watson, T. ; et al ( January 2021 , GSA Bulletin)

   null (Ed.)

   The unexpected intersection of rhyolitic magma and retrieval of quenched glass particles at the Iceland Deep Drilling Project-1 geothermal well in 2009 at Krafla, Iceland, provide unprecedented opportunities to characterize the genesis, storage, and behavior of subsurface silicic magma. In this study, we analyzed the complete time series of glass particles retrieved after magma was intersected, in terms of distribution, chemistry, and vesicle textures. Detailed analysis of the particles revealed them to represent bimodal rhyolitic magma compositions and textures. Early-retrieved clear vesicular glass has higher SiO2, crystal, and vesicle contents than later-retrieved dense brown glass. The vesicle size and distribution of the brown glass also reveal several vesicle populations. The glass particles vary in δD from −120‰ to −80‰ and have dissolved water contents spanning 1.3−2 wt%, although the majority of glass particles exhibit a narrower range. Vesicular textures indicate that volatile overpressure release predominantly occurred prior to late-stage magma ascent, and we infer that vesiculation occurred in response to drilling-induced decompression. The textures and chemistry of the rhyolitic glasses are consistent with variable partial melting of host felsite. The drilling recovery sequence indicates that the clear magma (lower degree partial melt) overlays the brown magma (higher degree partial melt). The isotopes and water species support high temperature hydration of these partial melts by a mixed meteoric and magmatic composition fluid. The textural evidence for partial melting and lack of crystallization imply that magma production is ongoing, and the growing magma body thus has a high potential for geothermal energy extraction. In summary, transfer of heat and fluids into felsite triggered variable degrees of felsite partial melting and produced a hydrated rhyolite magma with chemical and textural heterogeneities that were then enhanced by drilling perturbations. Such partial melting could occur extensively in the crust above magma chambers, where complex intrusive systems can form and supply the heat and fluids required to re-melt the host rock. Our findings emphasize the need for higher resolution geophysical monitoring of restless calderas both for hazard assessment and geothermal prospecting. We also provide insight into how shallow silicic magma reacts to drilling, which could be key to future exploration of the use of magma bodies in geothermal energy. 

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2. Numerical Modeling of Dike Propagation Out of Continuously and Episodically Growing Midcrustal Magma Chambers

   https://doi.org/10.1029/2019JB019021  

   Chen, Yanying ; Nabelek, Peter I. ( July 2020 , Journal of Geophysical Research: Solid Earth)

   In the continental crust, the probability of dike propagation out of magma chambers is governed by thermal, rheological, and pressure conditions of magma chamber‐wall rock systems. Incremental injection of melt into an average‐size, laccolith‐shaped, midcrustal magma chamber produces a volume of mobile magma at the bottom of the chamber that has the potential to escape as dikes through the upper, immobile portion of the chamber and the roof. Here we numerically model the conditions needed for dike propagation out of a magma chamber during continuous and episodic injections of melt into the chamber. The roles of magma buoyancy and overpressure from melt injections in generating dikes are explored within 1.78 × 10⁴to 1.78 × 10⁸ Pa·s range of magma viscosities (μ_mag), 10 to 40 GPa range of elastic moduli (E) of the immobile top portion of the magma chamber, and 10 and 20 kyr durations of chamber growth. During episodic, high‐flux melt injections (tens of km³/yr), magma overpressure can reach >100 MPa and initiate dike propagation even whenμ_magandEare near the high ends of the examined ranges. The probability of generating dikes diminishes when the injection flux is lower. Continuous low‐flux injections favor magma accumulation because injection overpressure never exceeds 20 MPa. During either continuous or episodic growth of magma chamber, there is never a sufficient amount of mobile magma in the chamber for dikes to be induced by magma buoyancy alone.

    

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3. Wavelet‐Based Characterization of Very‐Long‐Period Seismicity Reveals Temporal Evolution of Shallow Magma System Over the 2008–2018 Eruption of Kīlauea Volcano

   https://doi.org/10.1029/2020JB020837  

   Crozier, Josh ; Karlstrom, Leif ( May 2021 , Journal of Geophysical Research: Solid Earth)

   Very‐long‐period (VLP) volcano seismicity often encodes subsurface magma movement, and thus provides insight into subsurface magma transport processes. We develop a fully automated signal processing workflow using wavelet transforms to detect and assess period, decay rate, and ground motions of resonant VLP signals. We then generate a VLP catalog over the 2008–2018 open‐vent summit eruption of Kīlauea Volcano containing thousands of events. Two types of magma resonance dominate our catalog: vertical sloshing of the open magma column in and out of the shallow magma reservoir, and lateral sloshing of magma in the lava lake. These events were triggered mainly from the surface and less commonly from depth. The VLP catalog is then combined with other geophysical datasets to characterize evolution of the shallow magma system. VLP ground motion patterns show both abrupt and gradual changes in shallow magma reservoir geometry. Variation in resonant periods and decay rates of both resonance types occurred on timescales from hours to years, indicating variation in magma density and viscosity that likely reflect unsteady shallow outgassing and convection. A lack of correlation between decay rates of the two dominant resonant modes suggests a decoupling between magma in the conduit and lava lake. Known intrusions and rift zone eruptions often represented change points for resonance characteristics and their relations with other datasets. This data synthesis over a 10‐year eruptive episode at Klauea Volcano demonstrates how VLP seismicity can sharpen insights into magma system evolution for use in monitoring and understanding eruptive processes.

    

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4. Fizzy Super-Earths: Impacts of Magma Composition on the Bulk Density and Structure of Lava Worlds

   https://doi.org/10.3847/1538-4357/acea85  

   Boley, Kiersten M. ; Panero, Wendy R. ; Unterborn, Cayman T. ; Schulze, Joseph G. ; Martínez, Romy Rodríguez ; Wang 王, Ji 吉 ( September 2023 , The Astrophysical Journal)

   Lava worlds are a potential emerging population of Super-Earths that are on close-in orbits around their host stars, with likely partially molten mantles. To date, few studies have addressed the impact of magma on the observed properties of a planet. At ambient conditions, magma is less dense than solid rock; however, it is also more compressible with increasing pressure. Therefore, it is unclear how large-scale magma oceans affect planet observables, such as bulk density. We updateExoPlex, a thermodynamically self-consistent planet interior software, to include anhydrous, hydrous (2.2 wt% H₂O), and carbonated magmas (5.2 wt% CO₂). We find that Earth-like planets with magma oceans larger than ∼1.5R_⊕and ∼3.2M_⊕are modestly denser than an equivalent-mass solid planet. From our model, three classes of mantle structures emerge for magma ocean planets: (1) a mantle magma ocean, (2) a surface magma ocean, and (3) one consisting of a surface magma ocean, a solid rock layer, and a basal magma ocean. The class of planets in which a basal magma ocean is present may sequester dissolved volatiles on billion-year timescales, in which a 4M_⊕mass planet can trap more than 130 times the mass of water than in Earth’s present-day oceans and 1000 times the carbon in the Earth’s surface and crust.

    

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5. The Surface Deformation Signature of a Transcrustal, Crystal Mush‐Dominant Magma System

   https://doi.org/10.1029/2022JB024178  

   Mullet, Benjamin ; Segall, Paul ( May 2022 , Journal of Geophysical Research: Solid Earth)

   The transcrustal, mush‐dominated magma storage paradigm, which posits liquid melt is heterogeneously distributed within a vertically extensive magma mush, differs significantly from classical geodetic models, where melt is stored within liquid‐dominant chambers within an elastic crust. Here, we present mechanical models consistent with transcrustal melt storage by separating the magmatic system into three domains: liquid melt lenses, surrounding crystal‐dominated poroelastic magma mush, and elastic crust. Our results indicate that pressure changes within the melt lens may induce surface displacements that approximate the displacements predicted by spheroidal pressure sources that mimic the geometry of the mush zone. Adopting constitutive parameters of the mush dependent on mush melt fraction, we show that a magma storage system will have an effective geometry inferred from surface displacements that smoothly transitions from the geometry of the melt lens to the geometry of the mush as mush melt fraction increases. This holds true across multiple storage zone geometries, including a “transcrustal” storage zone with a magma mush that extends deep in the crust. Accounting for the presence of a magma mush can lead to an increase in the estimated volume of injected or withdrawn magma (by several multiples) compared to values obtained using fully elastic models. Comparing erupted magma volumes to source volume changes allows for an estimation of magma compressibility; we show the presence of a mush can increase this estimated magma compressibility by up to approximately 50%, suggesting magmas may have higher bubble fraction than previous geodetically derived estimates.

    

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