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Rate of magma supply beneath Mammoth Mountain, California based on helium isotopes and CO2 emissions

Jennifer L. Lewicki·William C. Evans·Emily K. Montgomery-Brown·Margaret T. Mangan·John King·Andrew G. Hunt
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Abstract

Mammoth Mountain, California, has exhibited unrest over the past ~30 years, characterized by seismicity over a broad range of depths, elevated 3 He/ 4 He ratios in fumarolic gas, and large-scale diffuse CO 2 emissions. This activity has been attributed to magmatic intrusion, but minimal ground deformation and the presence of a shallow crustal gas reservoir beneath Mammoth Mountain pose a challenge for estimating magma supply rate. Here, we use the record of fumarolic 3 He/ 4 He ratios and CO 2 emissions to estimate that of the ~5.2 Mt of CO 2 released from Mammoth Mountain between 1989 and 2016, 1.6 Mt was associated with active intrusion and degassing of ~0.05–0.07 km 3 of basaltic magma. Intrusion at an average rate of ~0.002–0.003 km 3 /year into a postulated zone of partial melt at ~15-km depth could occur without detection by local Global Navigation Satellite System stations.

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Geophysical Research LettersArticle
90° N90° S · 180° W ← longitude → 180° E
Source-reported bounding extent: 37.61232767789535° to 37.66289614387081° latitude; -119.07772064208983° to -118.97832870483398° longitude. This indicates report coverage, not an exact sampling location. View area on OpenStreetMap.

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Jennifer L. Lewicki, William C. Evans, Emily K. Montgomery-Brown, Margaret T. Mangan, John King, Andrew G. Hunt. 2019-05-08. Rate of magma supply beneath Mammoth Mountain, California based on helium isotopes and CO2 emissions. https://doi.org/10.1029/2019gl082487

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