Isotope and Trace Element Geochemistry of Augustine Volcano, Alaska: Implications for Magmatic Evolution

Johnson, Kathleen E.; Harmon, Russell S.; Richardson, Jean M.; Moorbath, S.; Strong, D. F.

doi:10.1093/petrology/37.1.95

Cited by 24 publications

(11 citation statements)

References 75 publications

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“…K 2 O‐SiO 2 variations in Alaskan (open circles) and Aleutian lavas (solid circles). These are compared with Aleutian‐Alaskan data from Nye and Reid [1986], Miller et al [1994], Class et al [2000], Romick et al [1990], Hildreth [1983], Johnson et al [1996], Nye and Turner [1990], Nye et al [1994], Kay and Kay [1994], and J. Myers and T. McElfrish (unpublished data compilation); as well as samples from the Piip and Komandorsky block [ Yogodzinski et al , 1994, 1995]. The back‐arc Bogoslof sample (B) is distinguished by its high K 2 O content.…”

Section: Resultsmentioning

confidence: 99%

Melting processes and fluid and sediment transport rates along the Alaska‐Aleutian arc from an integrated U‐Th‐Ra‐Be isotope study

et al. 2003

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[1] A comprehensive data set for young lavas erupted along the Alaska-Aleutian arc is used to examine how fluid and sediment transport rates and melting processes vary in response to systematic changes in subduction rate and dip along the arc and across the ocean-continent boundary. Positive correlations between convergence rate, volcano volume, and 238 U excesses suggest that magmatic output is closely linked to the size of the fluid flux which occurred <10 kyr prior to eruption. Sediment-sensitive tracers like Th/Nb, Ce/Ce*, and 10 Be/ 9Be also increase with convergence rate. However, the inferred 10 Be/ 9 Be ratio of this component is low relative to that in the incoming sediments, and this could reflect either sediment removal by accretion or storage in the mantle wedge for $0.5-1 Myr. Th/Nb and Th/Nd ratios exceed those expected from bulk sediment addition in the center of the arc suggesting that the enhanced sediment signal reflects transfer in a partial melt phase, whereas partial melts from the subducted oceanic crust appear to be restricted to the western tear in the Pacific plate. Therefore the thermal structure at the slabwedge interface in the center of the arc must lie close to, and possibly between, the sediment and basalt solidii and is thus constrained to be in the region of 670-740°C at 3 GPa. Ra excesses in many of the lavas are modeled as the products of dynamic melting effects superimposed upon a fluid-fluxed mantle wedge. The transition from oceanic to continental lithosphere seems to play an important role in determining the relative effects of fluid addition and partial melting upon U-Th disequilibria. We infer that the change from fast and steep plate subduction in the Aleutians to shallow and slow subduction, coupled with increasing lithospheric lid thickness, in Alaska together control slab and wedge temperatures and the rate of matrix flow through the melting region.INDEX TERMS: 1040 Geochemistry: Isotopic composition/chemistry; 8434 Volcanology: Magma migration; 8450 Volcanology: Planetary volcanism (5480); KEYWORDS: uranium series, beryllium isotopes, Aleutians, Alaska, arc petrogenesis Citation: George, R., S. Turner, C. Hawkesworth, J. Morris, C. Nye, J. Ryan, and S.-H. Zheng, Melting processes and fluid and sediment transport rates along the Alaska-Aleutian arc from an integrated U-Th-Ra-Be isotope study,

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Section: Resultsmentioning

confidence: 99%

Melting processes and fluid and sediment transport rates along the Alaska‐Aleutian arc from an integrated U‐Th‐Ra‐Be isotope study

et al. 2003

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“…Consequently, lavas from the five volcanoes exhibit similar bulk chemical compositions and are predominantly Doukas and Gerlach (1995), 6 Doukas and Gerlach (1995), 7 Roman et al (2004), 8 Gardine et al (2010), -= not mesured, data formats unchanged from original publications medium-K calc-alkaline andesites and dacites (Kienle and Swanson 1983;Miller et al 1998) ( Table 2). Detailed chemical, mineralogical, and limited isotopic data are available for Mount Spurr, Redoubt, and Augustine volcanoes (Nye and Turner 1990;Reed et al 1992;Begét and Nye 1994;Nye et al 1994;Swanson et al 1994;Till et al 1994;Harbin et al 1995;Johnson et al 1996;Wolf and Eichelberger 1997;Swanson and Kearney 2008;Larsen et al 2010). Much less is known about Iliamna and Fourpeaked volcanoes, although their bulk compositions and mineral assemblages are very similar to those of the better-studied volcanoes (Kienle and Swanson 1983;Miller et al 1998 Table 2).…”

Section: Background On Volcanoes: Eruptive and Unrest Activity Since mentioning

confidence: 99%

“…Augustine is the most active volcano in the region (Miller et al 1998) with at least four eruptive periods in the twentieth century (1935, 1963-64, 1976, and 1986) before the most recent eruption in 2006. Augustine erupts mostly andesitic and dacitic lavas (Kienle and Swanson 1983;Johnson et al 1996;Larsen et al 2010). In mid-2005, Augustine started experiencing unrest in the form of increased seismicity and deformation .…”

Section: Augustine Volcanomentioning

confidence: 99%

Gas emissions from failed and actual eruptions from Cook Inlet Volcanoes, Alaska, 1989–2006

2011

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Cook Inlet volcanoes that experienced an eruption between 1989 and 2006 had mean gas emission rates that were roughly an order of magnitude higher than at volcanoes where unrest stalled. For the six events studied, mean emission rates for eruptions were ∼13,000 t/d CO 2 and 5200 t/d SO 2 , but only ∼1200 t/d CO 2 and 500 t/d SO 2 for non-eruptive events ('failed eruptions'). Statistical analysis suggests degassing thresholds for eruption on the order of 1500 and 1000 t/d for CO 2 and SO 2 , respectively. Emission rates greater than 4000 and 2000 t/d for CO 2 and SO 2 , respectively, almost exclusively resulted during eruptive events (the only exception being two measurements at Fourpeaked). While this analysis could suggest that unerupted magmas have lower pre-eruptive volatile contents, we favor the explanations that either the amount of magma feeding actual eruptions is larger than that driving failed eruptions, or that magmas from failed eruptions experience less decompression such that the majority of H 2 O remains dissolved and thus insufficient permeability is produced to release the trapped volatile phase (or both). In the majority of unrest and eruption sequences, increases in CO 2 emission relative to SO 2 emission were observed early in the sequence. With time, all events converged to a common molar value of C/S between 0.5 and 2. These geochemical trends argue for roughly similar decompression histories until shallow levels are reached beneath the edifice (i.e., from 20-35 to ∼4-6 km) and perhaps roughly similar initial volatile contents in all cases. Early elevated CO 2 levels that we find at these highlatitude, andesitic arc volcanoes have also been observed at mid-latitude, relatively snow-free, basaltic volcanoes such as Stromboli and Etna. Typically such patterns are attributed to injection and decompression of deep (CO 2 -rich) magma into a shallower chamber and open system degassing prior to eruption. Here we argue that the C/S trends probably represent tapping of vapor-saturated regions with high C/S, and then gradual degassing of remaining dissolved volatiles as the magma progresses toward the surface. At these volcanoes, however, C/S is often accentuated due to early preferential scrubbing of sulfur gases. The range of equilibrium degassing is consistent with the bulk degassing of a magma with initial CO 2 and S of 0.6 and 0.2 wt.%, respectively, similar to what has been suggested for primitive Redoubt magmas.

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“…а -адакиты, б -породы неадакитового состава. Кроме материалов, отмеченных в подписях к рисунку 1, использованы также данные из работ: [1,2,18,20,28,34,40,50,51,52,56,57,75,82,89]. Область составов нижней-средней коры выделена по данным [3].…”

Section: рис 8 соотношение Nb-k для адакитов и ассоциирующих с нимиunclassified

Adakite Volcanic Activity on the Continental Margin and Its Problems. Part Ii. Types and Petrogenesis of Adakites in Rocks From the Sea of Okhotsk, Kamchatka, and Bering Sea Regions

Колосков¹,

Коваленко²,

Ananyev³

2019

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Isotope and Trace Element Geochemistry of Augustine Volcano, Alaska: Implications for Magmatic Evolution

Cited by 24 publications

References 75 publications

Melting processes and fluid and sediment transport rates along the Alaska‐Aleutian arc from an integrated U‐Th‐Ra‐Be isotope study

Melting processes and fluid and sediment transport rates along the Alaska‐Aleutian arc from an integrated U‐Th‐Ra‐Be isotope study

Gas emissions from failed and actual eruptions from Cook Inlet Volcanoes, Alaska, 1989–2006

Adakite Volcanic Activity on the Continental Margin and Its Problems. Part Ii. Types and Petrogenesis of Adakites in Rocks From the Sea of Okhotsk, Kamchatka, and Bering Sea Regions

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