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Geochemical investigation of the hydrothermal system on Akutan Island, Alaska, July 2012

Scientific Investigations Report 2013-5231
By: , , , , , and 
https://doi.org/10.3133/sir20135231

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Abstract

We have studied the geochemistry of the hot springs on Akutan Island in detail for the first time since the early 1980s. Springs in four discrete groups (A-D) along Hot Springs Creek showed generally higher temperatures and substantially higher Na, Ca, and Cl concentrations than previously reported, and total hot-spring discharge has also increased markedly. The springs now account for a heat output of ~29 MW, about an order of magnitude more than in 1981. Gas samples from the hot springs and from a fumarolic area on the flank of Akutan Volcano show high 3He/4He ratios (>6.4 RA) after correction for air contamination and reveal a common magmatic heat source. Hot-spring gases are unusually rich in N2, Ar, and CH4, suggesting that the water has boiled and lost CO2 during upflow beneath the flank fumarole field. Gas geothermometry calculations applied to the flank fumarole field implies temperatures of 200–240 °C for the reservoir, and Na-K-Ca geothermometry implies temperatures near 180 °C for the outflow waters that feed the hot springs. The results of our study confirm the existence of a substantial geothermal resource on the island.

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Publication type Report
Publication Subtype USGS Numbered Series
Title Geochemical investigation of the hydrothermal system on Akutan Island, Alaska, July 2012
Series title Scientific Investigations Report
Series number 2013-5231
DOI 10.3133/sir20135231
Year Published 2014
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Volcano Hazards Program, Volcano Science Center-Menlo Park
Description v, 19 p.
Country United States
State Alaska
Other Geospatial Akutan Island
Online Only (Y/N) Y
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