Magmatic Evolution of Semisopochnoi Island, Alaska: Trace-Element and Isotopic Constraints

DeLong, Stephen E.; Perfit, Michael R.; McCulloch, Malcolm T.; Ach, Jay A.

doi:10.1086/628985

Cited by 28 publications

(5 citation statements)

References 21 publications

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“…Trends in tholeiitic differentiation and the relatively large erupted volumes at Semisopochnoi volcano are indicative of relatively fast magma ascent through fractured lithosphere (Grosse et al, ). These tholeiitic eruptions reflect segmentation boundary volcanism due to the extensional rotating block, as well as the intersection of Bowers Ridge with the Aleutian trench (Coats, ; Coombs et al, ; Delong et al, ; Geist et al, ). The only confirmed eruptions occurred in 1873 from the Mount Cerberus three cone complex, but in 1987 eyewitness accounts indicate a potential eruption from Sugarloaf Peak.…”

Section: Introductionmentioning

confidence: 99%

High Rates of Inflation During a Noneruptive Episode of Seismic Unrest at Semisopochnoi Volcano, Alaska in 2014–2015

DeGrandpre

Pesicek

Lü

et al. 2019

Geochem Geophys Geosyst

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Magma intrusion rate is a key parameter in eruption triggering but is poorly quantified in existing geodetic studies. Here we examine two episodes of rapid inflation in this context. Two noneruptive microseismic swarms were recorded at Semisopochnoi Volcano, Alaska in 2014-2015. We use differential SAR techniques and TerraSAR-X images to document surface deformation from 2011 to 2015, which comprises island-wide radial inflation totaling~25 cm (+/−1 cm) line of sight displacement in 2014-2015. Multiple source geometries are tested in an inversion of the deformation data, and InSAR data are best fit by a spheroid trending to the northeast and plunging to the southeast, with a major axis of~4 km and minor axes of~1 km, directly under the central caldera of Semisopochnoi. In 2014, a modeled influx of 0.043 km 3 of magma caused line of sight displacement of~17 cm. This magma was stored at a depth of~8 km, until 2015 when 0.029 km 3 was added. Along with the definition of inflation source parameters, the recorded seismic events are relocated using differential travel times. These relocated events outline a linear aseismic area within a larger zone of shallow (<10 km) seismicity. This aseismic region aligns with the centroid of the deformation model. Based on these geodetic and seismic models, the plumbing system at Semisopochnoi is interpreted as a spheroidal magma storage zone at a depth of˜8 km below a linear feature of partial melt. The observed deformation and seismicity appear to result from rapid injection into this main storage region.

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Section: Introductionmentioning

confidence: 99%

High Rates of Inflation During a Noneruptive Episode of Seismic Unrest at Semisopochnoi Volcano, Alaska in 2014–2015

DeGrandpre

Pesicek

Lü

et al. 2019

Geochem Geophys Geosyst

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“…Lavas from volcanoes east of the Delarofs are shades of pink triangles [Kay and Kay, 1994;Kelemen et al, 2003;Singer et al, 2007 and references therein]. Lavas from volanoes west of Bowers Ridge are shades of teal triangles [Delong et al, 1985;Kay and Kay, 1994;George et al, 2003;Singer et al, 2007]. Eocene to Pliocene data [Rubenstone, 1984;Kay et al, 1990; (Kay and Jicha unpublished).…”

Section: 1002/2015gc006067mentioning

confidence: 99%

Eocene to Pleistocene magmatic evolution of the Delarof Islands, Aleutian Arc

Schaen

Jicha

Kay

et al. 2016

Geochem Geophys Geosyst

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The Delarof Islands in the Aleutian Arc near 179º W record ∼37 million years of discontinuous arc magmatism along a SW‐NE cross‐arc transect from near the trench to the active volcanic front. Geochemical and geochronologic data from the pre‐Pleistocene volcanic record in this region are limited and the 40Ar/39Ar, isotopic, and trace element data presented here are the first from units older than the Pleistocene‐Holocene volcanoes (Tanaga, Gareloi). Twenty‐two new 40Ar/39Ar ages establish a temporal framework for geochemical data and reveal that magmatism in the Delarof region was coincident with two arc‐wide magmatic flare ups in the late Eocene/early Oligocene and latest Miocene/Pliocene. Mafic lavas and plutons in the southern Delarofs give 40Ar/39Ar plateau ages ranging from 36.8 ± 0.2 to 26.9 ± 0.6 Ma on Amatignak Island and 37.0 ± 0.2 to 29.3 ± 1.0 Ma on Ulak Island. To the north 25 km, 40Ar/39Ar ages from the central Delarof Islands, Kavalga, Ogliuga, and Skagul are late Miocene (6.28 ± 0.04 Ma) to Pliocene (4.77 ± 0.18 Ma) with younger ages to the northeast. A significant transition in arc chemistry occurs in the Pleistocene where lavas from active volcanoes Gareloi and Tanaga exhibit higher sediment and hydrous fluid signatures (Th/La, Cs/Ta, La/Sm, LILE abundances) and lower 143Nd/144Nd than older Delarof Island units closer to the trench. Similar findings from Eocene‐Miocene lavas from Amchitka to Adak suggest that a previously minor sediment melt component became more pronounced in the Quaternary.

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“…Augustine volcanic rocks display a very restricted range of 87 Sr/ 86 Sr and e Nd ( Table 5). For example, Augustine 87 Sr/ 86 Sr ratios range from 07032 to 0-7034 compared with eastern arc calc-alkaline neighbours Mt Spurr at 0-7035-0-7040 (Nye & Turner, 1990) and Novarupta dome at 0-7034-07036 (Hildreth, 1983), and western Aleutian tholeiitic volcanic suites such as Okmok at 0-7031-0-7035 (Nye & Reid, 1986) and Semisopochnoi at 0-7032-0-7033 (DeLong et al, 1985). Similarly, £ Nd illo & Taylor (1976)].…”

Section: Isotope Geochemistrymentioning

confidence: 99%

“…Novarupta at +64 (von Drach et al, 1986) and Seguam at +7-0 to +5-9 (Singer et al, 1992) and tholeiitic suites, e.g. Okmok at +83 to + 7-4 (Nye & Reid, 1986) and Semisopochnoi at + 8-5 to +8-1 (DeLong «* al., 1985). Pb-isotopic variations at Augustine (Table 5) are also rather limited ( 206 Pb/ 204 Pb = 1028-1882, 2O7 Pb/ 2O4 Pb= 15-54-15-57 and 208 Pb/ 204 Pb = 3818-38-34).…”

Section: Isotope Geochemistrymentioning

confidence: 99%

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

et al. 1996

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Volcano, a Quaternary volcanic centre of the eastern Aleutian Arc, produces predominantly andesiies and dacites of low-to medium-K calc-alkaline composition. Mineralogical and major element characteristics of representative lavas suggest that magmatic evolution has been influenced by both crystal fractionation and magma-mixing processes. However, incompatible trace element variations (e.g. K/Rb) indicate that these evolved lavas have been contaminated by the mafic arc crust of the underlying Talkeetna accreted terrane. The limited range of isotope compositions also supports the assimilation of nonradiogenic mafic crust (e.g. S7 Sr/ S6 Sr = 0 7032-0-7034; m Nd/ I44 Nd = 0-51301-0-5130). In addition, Pb-isotope compositions parallel the North Pacific mean oceanic trend (2(k Pb/ 2M Pb = 18-3-18-8; 2o/ Pb/ 2O4 Pb = 15-5-15-6; 208 Pb/ 204 Pb-38-2-38-3) and do not require a subducted sediment component in the source. Relatively high (Ba/La) # (0-79-18-10) and B/Be (14-5) ratios do, however, suggest a metasomatic fluid component derived from the dehydration of the subducting plate. The thickened continental crust (~35 km) of the eastern Aleutian Arc prevents the ascent of basaltic melts, which fractionate and assimilate at various depths to produce andesitic magmas. These andesites evolve towards more silicic compositions by fractional crystallization. The absence of evidence for a large high-level crustal magma chamber implies that the magmatic system beneath the volcano is young and at an immature stage of evolution.

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Magmatic Evolution of Semisopochnoi Island, Alaska: Trace-Element and Isotopic Constraints

Cited by 28 publications

References 21 publications

High Rates of Inflation During a Noneruptive Episode of Seismic Unrest at Semisopochnoi Volcano, Alaska in 2014–2015

High Rates of Inflation During a Noneruptive Episode of Seismic Unrest at Semisopochnoi Volcano, Alaska in 2014–2015

Eocene to Pleistocene magmatic evolution of the Delarof Islands, Aleutian Arc

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

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