T254 Mineralogy, Geochemistry, Petrology, and Volcanology Student Session (Posters)

Wednesday, 25 September 2024
8:00 AM - 5:30 PM
Hall D

MELT INCLUSION RECONSTRUCTIONS OF THE MAGMATIC PLUMBING SYSTEM AT MT. IJEN, EAST JAVA, INDONESIA

Paper number: T254-3
Program: Technical Sessions
Time: 8:00 AM – 5:30 PM

Authors

Abstract

The Ijen Caldera Complex (ICC) in East Java, Indonesia is one of the most active yet least understood caldera complexes in Southeast Asia. Kawah Ijen, the main active feature today, experienced a significant phreatomagmatic eruption in 1817, and continues to emit fantastic quantities of sulfur, CO2, and toxic metals from its hyperacidic brine lake and neighboring fumarole field. Despite significant advances in our understanding of Kawah Ijen’s behavior in the last 10 years, there remains little to no understanding of the caldera’s magma storage conditions. Specifically, we lack constraints on the storage temperature and pressure of the ICC’s pre- and post-caldera magma reservoirs. We also lack a complete of Kawah Ijen’s plumbing system, a significant impediment to estimating its future eruptive behavior. Previous melt inclusion work concluded that Kawah Ijen’s magmas are some of the most volatile rich in the Sunda Arc with H2O/Ce ratios comparable to the most volatile-rich magmas in the world (Vigouroux et al. 2012).

In this contribution, we present preliminary data for the first comprehensive melt inclusion study of the ICC’s pre- and post-caldera magmatic system, including but not limited to Kawah Ijen. This work follows a successful field campaign in the summer of 2024, where fresh scoriaceous ejecta and lavas were sampled from the pre-caldera ignimbrites, post-caldera cinder cones, and Kawah Ijen. We quantify the volatile budget within each inclusion following established multi-instrument protocols (Rose-Koga et al. 2021), paying particular attention to melt inclusion morphology and the presence or absence of vapor bubbles. We combine our quantitative results with thermodynamic models of volatile saturation to establish storage depths, and compare our results to mineral thermobarometers. Our results provide the first 4-D picture of the ICC’s evolving magma plumbing system, highlighting Ijen's continued volcanic hazard potential.

Geological Society of America Abstracts with Programs. Vol. 56, No. 5

doi: 10.1130/abs/2024AM-405830

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