Please use this identifier to cite or link to this item: http://hdl.handle.net/2122/10649
AuthorsLopez, Taryn* 
Tassi, Franco* 
Aiuppa, Alessandro* 
Galle, Bo* 
Rizzo, Andrea Luca* 
Fiebig, Jens* 
Capecchiacci, Francesco* 
Giudice, Gaetano* 
Caliro, Stefano* 
Tamburello, Giancarlo* 
TitleGeochemical constraints on volatile sources and subsurface conditions at Mount Martin, Mount Mageik, and Trident Volcanoes, Katmai Volcanic Cluster, Alaska
Issue Date9-Sep-2017
Series/Report no./347 (2017)
DOI10.1016/j.jvolgeores.2017.09.001
URIhttp://hdl.handle.net/2122/10649
KeywordsKatmai
volcanic gases
Mount Martin
Mount Mageik
Trident
hydrothermal system
arc volcano
Subject Classification04.08. Volcanology 
AbstractWe use the chemical and isotopic composition of volcanic gases and steam condensate, in situ measurements of plume composition and remote measurements of SO2 flux to constrain volatile sources and characterize subvolcanic conditions at three persistently degassing and seismically active volcanoes within the Katmai Volcanic Cluster (KVC), Alaska:Mount Martin,Mount Mageik and Trident. In situ plume measurements of gas composition were collected at all three volcanoes usingMultiGAS instruments to calculate gas ratios (e.g. CO2/H2S, SO2/H2S and H2O/H2S), and remote measurements of SO2 column density were collected from Mount Martin and Mount Mageik by ultraviolet spectrometer systems to calculate SO2 fluxes. Fumaroles were directly sampled for chemical and isotopic composition from Mount Mageik and Trident. Mid Ocean Ridge Basalt (MORB)-like 3He/4He ratios (~7.2–7.6 Rc/RA) within Mount Mageik and Trident's fumarole emissions and a moderate SO2 flux (~75 t/d) from Mount Martin, combined with gas compositions dominated by H2O, CO2 and H2S from all three volcanoes, indicate magma degassing and active hydrothermal systems in the subsurface of these volcanoes. Mount Martin's gas emissions have the lowest CO2/H2S ratio (~2–4) and highest SO2 flux compared to the other KVC volcanoes, indicative of shallow magma degassing. Geothermometry techniques applied to Mount Mageik and Trident's fumarolic gas compositions suggest that their hydrothermal reservoirs are located at depths of ~0.2 and 4 km below the surface, respectively. Observations of an unusually reducing gas composition at Trident and organic material in the near-surface soils suggest that thermal decomposition of sediments may be influencing gas composition. When the measured gas compositions from Mount Mageik and Trident are compared with previous samples collected in the late 1990's, relatively stable magmatic-hydrothermal conditions are inferred forMountMageik,while gradual degassing of residual magma and contamination by shallow crustal fluids is inferred for Trident. The isotopic composition of volcanic gases emitted from Mount Mageik and Trident reflect mixing of subducted slab, mantle and crustal volatile sources, with organic sediment and carbonate being the predominant sources. Considering the close proximity of the target volcanoes in comparison with the depth to the subducted slab we speculate that Aleutian Arc volatiles are fed by a relatively homogeneous subducted fluid and that much of the apparent variability in volatile provenance can be explained by shallow crustal volatile sources and/or processes.
Appears in Collections:Papers Published / Papers in press

Files in This Item:
File Description SizeFormat 
Lopez et al., 2017.pdf2.07 MBAdobe PDFView/Open
Show full item record

Page view(s)

14
Last Week
1
Last month
checked on Jan 17, 2018

Download(s)

2
checked on Jan 17, 2018

Google ScholarTM

Check

Altmetric