75 Mineralogy, Geochemistry, Petrology, and Volcanology Student Session (Posters)

GSA’s MGPV student representatives invite the division’s student population to present their research (oral or poster). We encourage abstracts from any subdiscipline within our respective fields with hopes of stimulating a multi-disciplinary, early career researcher (ECR) community within MGPV.

Sunday, 19 October 2025
8:00 AM - 5:30 PM
HBGCC, Hall 1

Zircon petrochronology of the oldest fall deposits from Santa Barbara Caldera, Terceira Island, Azores Archipelago

Paper number: 75-29
Program: Technical Sessions
Time: 8:00 AM – 8:00 AM

Authors

Abstract

 Santa Barbara caldera is the westernmost caldera on Terceira Island and has erupted trachytic composition magmas for the last 100 k.y. It is located along the Terceira Rift zone in the Central Group islands. The oldest eruptions are basalts and trachytic lavas with a transition to explosive intermediate compositions around 10 k.y. The most recent eruption from the caldera occurred in 1761 A.D., as eight low-formed domes on the east side of the main caldera. Here we use zircon ages and trace element chemistry determined by SHRIMP-RG and LA-ICPMS, respectively, to understand the conditions of magma storage. We use pumices from two fall deposits, Fall “A” (~10 ka) and Fall “B” (10-3 ka), combined with whole-rock major and trace element compositions to determine the magma processes operating during magma storage. We propose a model where magma is stored and evolves under warm conditions until eruption is triggered.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6

doi: 10.1130/abs/2025AM-414496

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