Lydia J. Harmon , Guilherme A.R. Gualda , Blake M. Wallrich , Calvin F. Miller
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引用次数: 0
Abstract
Identifying the storage depths of melt-dominated magma bodies prior to eruption is critical for understanding magma transport, eruption hazards, and magma body longevity. Rhyolite-MELTS has been used effectively to calculate pre-eruptive storage pressures for silicic magma bodies in the upper crust (∼100–350 MPa), but its precision and accuracy in very low-pressure systems (<100 MPa) has not been sufficiently investigated. During the 2009 Krafla IDDP-1 drilling project, magma was surprisingly intersected at 2.1 km depth. Here, we test the use of rhyolite-MELTS geobarometry for this very low-pressure system, using natural Krafla IDDP-1 compositions that were intersected at a known depth. We input the composition of the melt (preserved as glass) and search in pressure and temperature and oxygen fugacity (fO2) spaces to model the storage conditions of the Krafla magma. For the average composition of the drilled glass, rhyolite-MELTS yields reasonable storage pressures (∼40–50 MPa). After converting calculated pressure to depth, the calculated depths are 1.6–1.9 km. These estimates are only 0.2–0.5 km different from that of the intersected magma, showing that rhyolite-MELTS provides excellent estimates for very shallow magma storage, further strengthened by results from a Monte Carlo analysis. The agreement between rhyolite-MELTS pressures and the drilled depth of the Krafla magma supports the previously calculated very shallow storage pressures in other locations, like the Taupō Volcanic Zone (TVZ), Aotearoa New Zealand. This shallowest storage zone of melt-dominated magmas has significant implications for modeling volcanic unrest and evaluating geothermal and economic resource potential.
期刊介绍:
Earth and Planetary Science Letters (EPSL) is a leading journal for researchers across the entire Earth and planetary sciences community. It publishes concise, exciting, high-impact articles ("Letters") of broad interest. Its focus is on physical and chemical processes, the evolution and general properties of the Earth and planets - from their deep interiors to their atmospheres. EPSL also includes a Frontiers section, featuring invited high-profile synthesis articles by leading experts on timely topics to bring cutting-edge research to the wider community.