The post-Mazama northwest rift zone eruption at Newberry Volcano, Oregon

McKay, D.; Donnelly‐Nolan, Julie M.; Jensen, Robert A.; Champion, Duane E.

doi:10.1130/2009.fld015(05)

Cited by 6 publications

(6 citation statements)

References 15 publications

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“…The concentration of higher velocities east and west of the caldera may be related to the east‐west extensional setting at Newberry Volcano. In this scenario rising mafic magma intrudes and solidifies around Newberry Volcano except where fractures along the Northwest Rift Zone, trending north‐south through Newberry Volcano (Figure 1b), facilitate eruptions at the surface [ Mckay et al , 2009]. Intrusions east and west of the Northwest Rift Zone may not erupt as easily and consequently build up relatively larger intrusive complexes.…”

Section: Discussionmentioning

confidence: 99%

“…In addition to caldera collapses, evidence for a shallow magma storage system beneath Newberry includes a bimodal distribution of silicic and mafic eruptions. Silicic eruptions mainly occur within the caldera, such as the Big Obsidian Flow (1300 years old), and mafic eruptions occur outside the caldera, such as the Northwest Rift Zone eruptions of 7,000 years ago [ Mckay et al , 2009]. To cause this pattern, rising mafic magmas are thought to encounter a central, silicic magma storage system beneath the caldera [ MacLeod and Sherrod , 1988].…”

Section: Introductionmentioning

confidence: 99%

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Upper crustal structure of Newberry Volcano from P‐wave tomography and finite difference waveform modeling

et al. 2012

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.[1] Seismic tomography combined with waveform modeling constrains the dimensions and melt content of a magma body in the upper crust at Newberry Volcano. We obtain a P-wave tomographic image by combining travel-time data collected in 2008 on a line of densely spaced seismometers with active-source data collected in the 1980s. The tomographic analysis resolves a high-velocity intrusive ring complex surrounding a low-velocity caldera-fill zone at depths above 3 km and a broader high-velocity intrusive complex surrounding a central low-velocity anomaly at greater depths (3-6 km). This second, upper-crustal low-velocity anomaly is poorly resolved and resolution tests indicate that an unrealistically large, low-velocity body representing $60 km 3 of melt could be consistent with the available travel times. The 2008 data exhibit low amplitude first arrivals and an anomalous secondary P wave phase originating beneath the caldera. Two-dimensional finite difference waveform modeling through the tomographic velocity model does not reproduce these observations. To reproduce these phases, we predict waveforms for models that include synthetic low-velocity bodies and test possible magma chamber geometries and properties. Three classes of models produce a transmitted P-phase consistent with the travel time and amplitude of the observed secondary phase and also match the observed lower amplitude first arrivals. These models represent a graded mush region, a crystal-suspension region, and a melt sill above a thin mush region. The three possible magma chamber models comprise a much narrower range of melt volumes (1.6-8.0 km 3 ) than could be constrained by travel-time tomography alone.Citation: Beachly, M. W., E. E. E. Hooft, D. R. Toomey, and G. P. Waite (2012), Upper crustal structure of Newberry Volcano from P-wave tomography and finite difference waveform modeling,

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Upper crustal structure of Newberry Volcano from P‐wave tomography and finite difference waveform modeling

et al. 2012

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“…All Holocene intracaldera eruptions have been rhyolitic, mainly as obsidian flows (MacLeod & Sherrod, ) that were preceded by Plinian eruptive phases. The outermost major vent of the NWRZ is 21 km from the caldera rim (McKay et al, ).…”

Section: Introductionmentioning

confidence: 99%

Composition of Magma and Characteristics of the Hydrothermal System of Newberry Volcano, Oregon, From Magnetotellurics

Bowles-martinez

Schultz

2020

Geochem Geophys Geosyst

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We use 3‐D magnetotellurics to improve our understanding of the structure and magma composition of Newberry Volcano in Oregon, USA. Newberry is a broad shield volcano with a summit caldera and strongly bimodal magmatism. Newberry has long been the subject of geothermal exploration research, but that work has focused on the volcano's west flank, leaving the caldera largely unstudied with geophysical methods until recently. Our modeling shows a relatively resistive magma reservoir of approximately 50 Ωm. Our work builds upon recent seismic models and petrological analysis to interpret Newberry's magma reservoir as a dry rhyolite with 8–11% partial melt, which matches the seismically determined melt fraction. Finding the conditions within the magma reservoir that allow the resistivity and seismic analysis to come to the same melt fraction helps us narrow down the magma temperature and composition. From this we infer a dry rhyolitic magma at 850 °C. We also image a prominent vertical conductive anomaly along the south rim below the vent that produced the most recent eruption. The anomaly extends from magma reservoir depths of 3 km to 1 km below the surface where it disperses into the caldera fill. We interpret this as the main conduit for magmatic fluids to reach Newberry's hydrothermal system. Other features that our model shows include higher conductivity along the caldera rim and a resistive older pluton on the west flank.

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“…The presence of both sideromelane and tachylite is a common feature of tephra deposits from cinder cone eruptions (e.g., Cinder Cone, CA 1 ; Stromboli, Italy 2 3 ; Mt. Etna, Italy 4 ; Parícutin, Mexico 5 ; Newberry Volcano, OR 6 ; Mt. Vesuvius, Italy 7 ).…”

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confidence: 99%

Rapid crystallization during recycling of basaltic andesite tephra: timescales determined by reheating experiments

Deardorff

Cashman

2017

Sci Rep

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Microcrystalline inclusions within microlite-poor matrix are surprisingly common in low intensity eruptions around the world, yet their origin is poorly understood. Inclusions are commonly interpreted as evidence of crystallization along conduit margins. Alternatively, these clasts may be recycled from low level eruptions where they recrystallize by heating within the vent. We conducted a series of experiments heating basaltic andesite lapilli from temperatures below the glass transition (~690 °C) to above inferred eruption temperatures (>1150 °C) for durations of 2 to >60 minutes. At 690 °C < T < 800 °C, crystallization is evident after heating for ~20 minutes; at T > 800 °C, crystallization occurs in <5 minutes. At T ≥ 900 °C, all samples recrystallize extensively in 2–10 minutes, with pyroxenes, Fe-oxides, and plagioclase. Experimental crystallization textures closely resemble those observed in natural microcrystalline inclusions. Comparison of inclusion textures in lapilli from the active submarine volcano NW Rota-1, Mariana arc and subaerial volcano Stromboli suggest that characteristic signatures of clast recycling are different in the two environments. Specifically, chlorine assimilation provides key evidence of recycling in submarine samples, while bands of oxides bordering microcrystalline inclusions are unique to subaerial environments. Correct identification of recycling at basaltic vents will improve (lower) estimates of mass eruption rate and help to refine interpretations of eruption dynamics.

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The post-Mazama northwest rift zone eruption at Newberry Volcano, Oregon

Cited by 6 publications

References 15 publications

Upper crustal structure of Newberry Volcano from P‐wave tomography and finite difference waveform modeling

Upper crustal structure of Newberry Volcano from P‐wave tomography and finite difference waveform modeling

Composition of Magma and Characteristics of the Hydrothermal System of Newberry Volcano, Oregon, From Magnetotellurics

Rapid crystallization during recycling of basaltic andesite tephra: timescales determined by reheating experiments

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