Geological, geochemical, and geophysical survey of the geothermal resources at Hot Springs Bay Valley, Akutan Island, Alaska

Motyka, R. J.; Wescott, E. M.; Turner, David L.; Swanson, Samuel E.; Romick, J.D.; Moorman,; Poreda, Robert J.; Witte, William K.; Petzinger, B.; Allely, R.D.

doi:10.2172/5626671

Cited by 3 publications

(11 citation statements)

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“…(For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.) 230 • C, and likely exceeding 240 • C. If the sample from TG-2 (254 m) is only modestly contaminated by drilling fluid and reflects the dilution path, the projected temperature could be closer to 260 • C. Silica geothermometers, which tend to record more recently equilibrated fluid temperatures, yield temperatures of ∼170 • C for TG-2, agreeing with the spring chemistry interpretations of Motyka and Nye (1988) and Symonds et al (2003a,b), and with the maximum measured well discharge temperature of 182 • C. This is consistent with a higher temperature (>240 • C) source that is capable of producing an outflow aquifer with temperature >180 • C, consistent with the hot spring and borehole production cation and silica geothermometry (Table 4). Geothermometry estimates from HSBV fumarole gases consistently suggests reservoir temperatures of 270-300 • C, as shown, RH value (oxidation state) of −2.8 is typical for an equilibrated geothermal system associated with an andesitic stratovolcano (Giggenbach, 1991).…”

Section: Geothermometrysupporting

confidence: 62%

“…Published chemical data from hot springs, meteoric water and fumarole gases (Motyka and Nye, 1988;Motyka et al, 1993;Symonds et al, 2003a,b) were combined with data from three water samples collected during drilling: one from the productive zone in TG-2 at 178 m depth collected during drilling; one from the bottom of TG-2 (254 m depth); and one from TVD in TG-4 (500 m depth). Due to poor permeability in TG-4, the sample required an air-assist to bring well fluid samples to the surface.…”

Section: Fluid and Gas Geochemistrymentioning

confidence: 99%

“…Updated liquid geothermometer calculations (Powell and Cumming, 2010) were applied to both published chemical analyses of Akutan hot spring waters (Motyka and Nye, 1988;Bergfeld et al, 2014) as well as recently collected hot spring, fumarole gas and condensate, and well discharge fluids. Table 4 presents the results of several cation and silica geothermometers.…”

Section: Geothermometrymentioning

confidence: 99%

“…Because dilution through mixing with meteoric water is likely (Section 2.5), these compositions have been extrapolated to the equilibrium line, suggesting temperatures of at least Table 1 Geochemical analyses of Akutan waters. Hot spring data are from Motyka and Nye (1988); well discharge and steam condensate samples were analyzed by ThermoChem, Inc. Well discharge samples data have been corrected for Table 1. Hot springs and discharge from 178 m in TG-2 are from equilibrated geothermal brine that has mixed along the flow path with dilute peripheral waters that are slightly enriched with HCO3 and SO4.…”

Section: Geothermometrymentioning

confidence: 99%

“…The largest and the most accessible geothermal prospect area is HSBV, which occupies portions of two linear, glacially carved valleys (Fig. 1) in the Pliocene-Pleistocene deposits of ancestral Akutan Volcano (Finch, 1935;Motyka and Nye, 1988;Romick, 1990;Motyka et al, 1993;Richter et al, 1998, Waythomas, 1999. Bergfeld et al (2014) demonstrates that the heat flow from the lower HSBV chain of hot springs has increased by nearly an order of magnitude between the early 1980s and 2012, to 29 MW t .…”

Section: Introductionmentioning

confidence: 99%

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Exploration of the Hot Springs Bay Valley (HSBV) geothermal resource area, Akutan, Alaska

Stelling

Hinz

Kolker³

et al. 2015

Geothermics

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Section: Geothermometrysupporting

confidence: 62%

Section: Fluid and Gas Geochemistrymentioning

confidence: 99%

Section: Geothermometrymentioning

confidence: 99%

Section: Geothermometrymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Exploration of the Hot Springs Bay Valley (HSBV) geothermal resource area, Akutan, Alaska

Stelling

Hinz

Kolker³

et al. 2015

Geothermics

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Stratigraphic framework of Holocene volcaniclastic deposits, Akutan Volcano, east-central Aleutian Islands, Alaska

Waythomas

1999

Bulletin of Volcanology

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Akutan Volcano is one of the most active volcanoes in the Aleutian arc, but until recently little was known about its history and eruptive character. Following a brief but sustained period of intense seismic activity in March 1996, the Alaska Volcano Observatory began investigating the geology of the volcano and evaluating potential volcanic hazards that could affect residents of Akutan Island. During these studies new information was obtained about the Holocene eruptive history of the volcano on the basis of stratigraphic studies of volcaniclastic deposits and radiocarbon dating of associated buried soils and peat. A black, scoria-bearing, lapilli tephra, informally named the "Akutan tephra," is up to 2 m thick and is found over most of the island, primarily east of the volcano summit. Six radiocarbon ages on the humic fraction of soil A-horizons beneath the tephra indicate that the Akutan tephra was erupted approximately 1611 years B.P. At several locations the Akutan tephra is within a conformable stratigraphic sequence of pyroclastic-flow and lahar deposits that are all part of the same eruptive sequence. The thickness, widespread distribution, and conformable stratigraphic association with overlying pyroclastic-flow and lahar deposits indicate that the Akutan tephra likely records a major eruption of Akutan Volcano that may have formed the present summit caldera. Noncohesive lahar and pyroclastic-flow deposits that predate the Akutan tephra occur in the major valleys that head on the volcano and are evidence for six to eight earlier Holocene eruptions. These eruptions were strombolian to subplinian events that generated limited amounts of tephra and small pyroclastic flows that extended only a few kilometers from the vent. The pyroclastic flows melted snow and ice on the volcano flanks and formed lahars that traveled several kilometers down broad, formerly glaciated valleys, reaching the coast as thin, watery, hyperconcentrated flows or water floods. Slightly cohesive lahars in Hot Springs valley and Long valley could have formed from minor flank collapses of hydrothermally altered volcanic bedrock. These lahars may be unrelated to eruptive activity.

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Magma‐Fluid Interactions Beneath Akutan Volcano in the Aleutian Arc Based on the Results of Local Earthquake Tomography

2021

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Volcanoes in the Aleutian arc and Alaska are located in low-populated areas; nevertheless, they represent serious hazard to the local population and infrastructure, as well as to the air traffic along dense aviation routes in the northern Pacific (Casadevall, 1993). To enable fast detection of ongoing volcanic eruptions, most active volcanoes in these regions are equipped with telemetered seismic networks that continuously transmit the records to the offices of the Alaska Volcano Observatory (AVO), where they are processed in real time (Dixon et al., 2019). Besides the hazard assessment, the data recorded by these networks are used for studying fundamental aspects of functioning magma plumbing systems, which still remain poorly understood due to their complexity. Mechanical, chemical, and thermal interactions of materials in the magmatic systems require multidisciplinary approaches, in which geophysical imaging of structures beneath volcanoes is one of the essential elements. In this study, we investigate the upper-and middle-crustal structure beneath Akutan Island located in the eastern part of the Aleutian arc (Figure 1a). This island hosts Akutan volcano, which is one of the most active in the Aleutian arc, with dozens of documented eruptions starting from the eighteenth century (Siebert & Simkin, 2013). These eruptions were mostly weak or moderate; however, the existence of a Holocene caldera with a diameter ∼2 km and thick scoria-bearing, lapilli tephra (Akutan tephra) widely spreading over the entire island surface (Waythomas, 1999) indicates that Akutan has a serious potential for explosive caldera-forming eruptions. During the past century, Akutan demonstrated variable styles of volcanic activity, such as lava flows, gas emissions, and strombolian explosive eruptions ejecting ash plumes (e.g., Miller et al., 1998). The most recent eruption of Akutan occurred in 1992. However, after this, in March 1996, a remarkable episode of seismic unrest occurred, which did not lead to a volcanic eruption, but caused earthquakes with magnitudes of up to M5.3 and triggered strong ground deformations (Lu et al., 2000, 2005). These and other aspects of Akutan's activity are discussed in more detail in the next section.

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Geological, geochemical, and geophysical survey of the geothermal resources at Hot Springs Bay Valley, Akutan Island, Alaska

Cited by 3 publications

References 0 publications

Exploration of the Hot Springs Bay Valley (HSBV) geothermal resource area, Akutan, Alaska

Exploration of the Hot Springs Bay Valley (HSBV) geothermal resource area, Akutan, Alaska

Stratigraphic framework of Holocene volcaniclastic deposits, Akutan Volcano, east-central Aleutian Islands, Alaska

Magma‐Fluid Interactions Beneath Akutan Volcano in the Aleutian Arc Based on the Results of Local Earthquake Tomography

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