UNRAVELING TRANSIENT CHANGES IN ERUPTION STYLE DURING THE 2018 MOUNT VENIAMINOF ERUPTION, ALASKA: PRELIMINARY OLIVINE GEOCHEMISTRY RESULTS

Mount Veniaminof is a 35 km wide arc tholeiitic volcano in the western Alaskan Peninsula with prolific history of volcanic activity in the Pleistocene and Holocene. Multiple caldera-forming eruptions occurred in the Pleistocene, but the most recent stage of magmatism is low Volcanic Explosivity Index (VEI), Strombolian eruptions. The most recent eruption lasted from September-December, 2018 and began with small lava flows into the ice-filled caldera, but, in November, there was a paroxysmal event, resulting in a 450 km long ash plume. While this plume was short lived, it marked the first large explosive eruption in recent history.

In this study, we investigate the transient changes in eruption style during the most recent eruption. Here, we present preliminary geochemical analyses of olivine grains from tephra via LA-ICP-MS in order to understand the changes in eruption dynamics during this eruption, and to investigate potential sources for these phenocrysts. Mineral chemistry suggests a composite origin of this eruption tapping different components within the crust. While there is little variation in major elements, analyses of trace element reveal two potential populations of olivine. One population having crystallized from the erupting magma and the other potentially representing remobilized cumulates.