Abstract
The Aleutian Arc is remote and highly active volcanically. Its 4,000 km extent from mainland Alaska to Russia’s Kamchatka peninsula hosts over 140 volcanic centers of which about 50 have erupted in historic times. We present data of volcanic gas samples and gas emission measurements obtained during an expedition to the western-most segment of the arc in September 2015 in order to extend the sparse knowledge on volatile emissions from this remote but volcanically active region. Some of the volcanoes investigated here have not been sampled for gases before this writing. Our data show that all volcanoes host high-temperature magmatic-hydrothermal systems and have gas discharges typical of volcanoes in oceanic arcs. Based on helium isotopes, the western Aleutian Arc segment has minimal volatile contributions from the overriding crust. Volcanic CO2fluxes from this arc segment are small, compared to the emissions from volcanoes on the Alaska Peninsula and mainland Alaska. The comparatively low CO2emissions may be related to the lower sediment flux delivered to the trench in this part of the arc.
Highlights
The Aleutian Arc is one of the most volcanically active and remote arcs in the world
In this publication we present the first constraints on the chemical composition of volcanic gases from Western Aleutians volcanoes of Gareloi, Kiska and Kanaga
The results indicate that all the volcanoes investigated host high-temperature mixed liquid-vapor systems that are fed by volatiles primarily sourced from the mantle wedge and the subducted slab, with negligible crustal contamination
Summary
The Aleutian Arc is one of the most volcanically active and remote arcs in the world. The arc extends ∼4,000 km from mainland Alaska to Russia’s Kamchatka Peninsula and separates the Bering Sea to the North from the Pacific Ocean to the South (Figure 1). The eastern 2,500 km of the arc represents the region of active volcanism and is undergoing subduction of the Pacific plate beneath the North American plate. At the time of writing (2021), Semisopochnoi, Great Sitkin and Pavlof volcanoes are currently erupting, and Gareloi and Cleveland volcanoes have shown signs of unrest (GVP, 2015; GVP, 2019; GVP, 2021a; GVP, 2021b; GVP, 2021c; GVP, 2021d). The frequent eruptions occurring in the Aleutian Arc often produce high-altitude ash clouds that are hazardous to the numerous aircraft that fly over the North Pacific Ocean. Previous studies have investigated volcanic gas emissions from many Eastern and Central Aleutian volcanoes; at the time of this study little was known about volcanic gas emissions from the Western Aleutian volcanoes
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