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1. A revised map of volcanic units in the Oman ophiolite: insights into the architecture of an oceanic proto-arc volcanic sequence

   https://doi.org/10.5194/se-10-1181-2019  

   Belgrano, Thomas M. ; Diamond, Larryn W. ; Vogt, Yves ; Biedermann, Andrea R. ; Gilgen, Samuel A. ; Al-Tobi, Khalid ( January 2019 , Solid Earth)

   Abstract. Numerous studies have revealed genetic similarities between Tethyanophiolites and oceanic “proto-arc” sequences formed above nascent subductionzones. The Semail ophiolite (Oman–U.A.E.) in particular can be viewed as ananalogue for this proto-arc crust. Though proto-arc magmatism and themechanisms of subduction initiation are of great interest, insight isdifficult to gain from drilling and limited surface outcrops in marinesettings. In contrast, the 3–5 km thick upper-crustal succession of theSemail ophiolite, which is exposed in an oblique cross section, presents anopportunity to assess the architecture and volumes of different volcanicrocks that form during the proto-arc stage. To determine the distribution ofthe volcanic rocks and to aid exploration for the volcanogenic massivesulfide (VMS) deposits that they host, we have remapped the volcanic unitsof the Semail ophiolite by integrating new field observations, geochemicalanalyses, and geophysical interpretations with pre-existing geological maps.By linking the major-element compositions of the volcanic units to rockmagnetic properties, we were able to use aeromagnetic data to infer theextension of each outcropping unit below sedimentary cover, resulting ina new map showing 2100 km2 of upper-crustal bedrock. Whereas earlier maps distinguished two main volcanostratigraphic units, wehave distinguished four, recording the progression from early spreading-axisbasalts (Geotimes), through axial to off-axial depleted basalts (Lasail), topost-axial tholeiites (Tholeiitic Alley), and finally boninites (BoniniticAlley). Geotimes (“Phase 1”) axial dykes and lavas make up ∼55 vol % of the Semail upper crust, whereas post-axial (“Phase 2”) lavasconstitute the remaining ∼45 vol % and ubiquitously coverthe underlying axial crust. Highly depleted boninitic members of the Lasailunit locally occur within and directly atop the axial sequence, marking anearlier onset of boninitic magmatism than previously known for theophiolite. The vast majority of the Semail boninites, however, belong to theBoninitic Alley unit and occur as discontinuous accumulations up to 2 kmthick at the top of the ophiolite sequence and constitute ∼15 vol % of the upper crust. The new map provides a basis for targetedexploration of the gold-bearing VMS deposits hosted by these boninites. Thethickest boninite accumulations occur in the Fizh block, where magma ascentoccurred along crustal-scale faults that are connected to shear zones in theunderlying mantle rocks, which in turn are associated with economicchromitite deposits. Locating major boninite feeder zones may thus be anindirect means to explore for chromitites in the underlying mantle. 

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2. Late Quaternary Eruption Record and Probability of Future Volcanic Eruptions in the Long Valley Volcanic Region (CA, USA)

   https://doi.org/10.1029/2018JB015644  

   Bevilacqua, Andrea ; Bursik, Marcus ; Patra, Abani ; Bruce Pitman, E. ; Yang, Qingyuan ; Sangani, Radhika ; Kobs-Nawotniak, Shannon ( July 2018 , Journal of Geophysical Research: Solid Earth)
3. Skillful prediction of multidecadal variations in volcanic forcing: SKILLFUL PREDICTION OF VOLCANIC FORCING

   https://doi.org/10.1002/2016GL072234  

   Tuel, A. ; Naveau, P. ; Ammann, C. M. ( March 2017 , Geophysical Research Letters)
4. Modeling Magma System Evolution During 2006–2007 Volcanic Unrest of Atka Volcanic Center, Alaska

   https://doi.org/10.1029/2020JB020158  

   Zhan, Yan ; Gregg, Patricia M. ; Lu, Zhong ( February 2021 , Journal of Geophysical Research: Solid Earth)

   Surface deformation and seismicity provide critical information to understand the dynamics of volcanic unrest. During 2006–2007, >80 mm/yr uplift was observed by interferometric synthetic aperture radar (InSAR) at the central Atka volcanic center, Alaska, coinciding with an increasing seismicity rate. On November 25, 2006, a phreatic eruption occurred at the Korovin volcanic vent, 5‐km north of the central Atka, following the drainage of its crater lake a month prior to the eruption. The InSAR data are assimilated into three‐dimensional finite element models using the Ensemble Kalman Filter to investigate: (1) the pressure source creating the surface deformation; (2) the triggering of the volcano‐tectonic (VT) earthquakes in the Atka volcanic center; and (3) the triggering of the phreatic eruption at Korovin. The models show that the pressure source required to create the surface deformation is a NE‐tilted, oblate ellipsoid, which rotated from steep to gentle dipping from June to November 2006 before the eruption. The modeled dilatancy in a pre‐existing weak zone, coinciding with the Amlia‐Amukta fault, driven by the pressure source has a spatial and temporal correlation with the evolution of the VT earthquakes during the unrest. The fault dilatancy may have increased the connected porosity and permeability of the fault zone allowing fluid injection which triggered the observed seismicity. In addition, the dilatated fault may have increased the fluid capacity of the fault zone by ∼10⁵ m³, causing the discharge of the crater lake at Korovin. Consequently, the phreatic eruption of the Korovin volcano may have been triggered.

    

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5. Volcanic glass properties from 1459 C.E. volcanic event in South Pole ice core dismiss Kuwae caldera as a potential source

   https://doi.org/10.1038/s41598-019-50939-x  

   Hartman, Laura H. ; Kurbatov, Andrei V. ; Winski, Dominic A. ; Cruz-Uribe, Alicia M. ; Davies, Siwan M. ; Dunbar, Nelia W. ; Iverson, Nels A. ; Aydin, Murat ; Fegyveresi, John M. ; Ferris, David G. ; et al ( October 2019 , Scientific Reports)

   A large volcanic sulfate increase observed in ice core records around 1450 C.E. has been attributed in previous studies to a volcanic eruption from the submarine Kuwae caldera in Vanuatu. Both EPMA–WDS (electron microprobe analysis using a wavelength dispersive spectrometer) and SEM–EDS (scanning electron microscopy analysis using an energy dispersive spectrometer) analyses of five microscopic volcanic ash (cryptotephra) particles extracted from the ice interval associated with a rise in sulfate ca. 1458 C.E. in the South Pole ice core (SPICEcore) indicate that the tephra deposits are chemically distinct from those erupted from the Kuwae caldera. Recognizing that the sulfate peak is not associated with the Kuwae volcano, and likely not a large stratospheric tropical eruption, requires revision of the stratospheric sulfate injection mass that is used for parameterization of paleoclimate models. Future work is needed to confirm that a volcanic eruption from Mt. Reclus is one of the possible sources of the 1458 C.E. sulfate anomaly in Antarctic ice cores.

    

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