Daniel J. Rasmussen
Terry Plank
Peter J. Kelly
Christoph Kern
Taryn Lopez
Jonas Gliss
John Power
Diana Roman
Pavel Izbekov
John J. Lyons
Cynthia Werner
2020
<p><span>Mount Cleveland is one of Alaska's most active volcanoes, yet little is known about the magmatic system driving persistent and dynamic volcanic activity. Volcanic gas and melt inclusion (MI) data from 2016 were combined to investigate shallow magmatic processes. SO</span><sub>2</sub><span> emission rates were between 166 and 324 t/day and the H</span><sub>2</sub><span>O/SO</span><sub>2</sub><span> was 600 ± 53, whereas CO</span><sub>2</sub><span> and H</span><sub>2</sub><span>S were below detection. Olivine‐, clinopyroxene‐, and plagioclase‐hosted MIs have up to 3.8 wt.% H</span><sub>2</sub><span>O, 514 ppm CO</span><sub>2</sub><span>, and 2,320 ppm S. Equilibration depths, based on MI H</span><sub>2</sub><span>O contents, suggest that a magmatic column extended from 0.5 to 3.0 km (~10–60 MPa). We used MI data to empirically model open‐system H‐C‐S degassing from 0 to 12 km and found that a column of magma between 0.5 and 3 km could produce the measured gas H</span><sub>2</sub><span>O/SO</span><sub>2</sub><span> ratio. However, additional magma deeper than 3 km is required to sustain emissions over periods greater than days to weeks, if the observed vent dimension is a valid proxy for the conduit. Assuming an initial S content of 2,320 ppm, the total magma supply needed to sustain the annual SO</span><sub>2</sub><span> flux was 5 to 9.8 Mm</span><sup>3</sup><span>/yr, suggesting a maximum intrusive‐to‐extrusive ratio of 13:1. The model predicts degassing of <50 t/day CO</span><sub>2</sub><span> for July 2016, which corresponds to a maximum predicted CO</span><sub>2</sub><span>/SO</span><sub>2</sub><span> of 0.2. Ultimately, frequent recharge from deeper, less degassed magma is required to drive the continuous activity observed over multiple years. During periods of recharge we would expect lower H</span><sub>2</sub><span>O/SO</span><sub>2</sub><span> and measurable volcanic CO</span><sub>2</sub><span>.</span></p>
application/pdf
10.1029/2019GC008882
en
Geological Society of America
Linking subsurface to surface using gas emission and melt inclusion data at Mount Cleveland volcano, Alaska
article