Barboni MDepartment of Earth, Planetary, and Space Sciences, University of California, Los Angeles, CA 90095; tmark.harrison@gmail.com mbarboni@epss.ucla.edu.
Boehnke PDepartment of Earth, Planetary, and Space Sciences, University of California, Los Angeles, CA 90095.
Schmitt AKInstitute of Earth Sciences, Heidelberg University, 69120 Heidelberg, Germany.
Harrison TMDepartment of Earth, Planetary, and Space Sciences, University of California, Los Angeles, CA 90095; tmark.harrison@gmail.com mbarboni@epss.ucla.edu.
Shane PSchool of Environment, The University of Auckland, 1142 Auckland, New Zealand.
Bouvier ASInstitute of Earth Sciences, University of Lausanne, 1015 Lausanne, Switzerland.
Baumgartner LInstitute of Earth Sciences, University of Lausanne, 1015 Lausanne, Switzerland.
English
Felsic magmatic systems represent the vast majority of volcanic activity that poses a threat to human life. The tempo and magnitude of these eruptions depends on the physical conditions under which magmas are retained within the crust. Recently the case has been made that volcanic reservoirs are rarely molten and only capable of eruption for durations as brief as 1,000 years following magma recharge. If the "cold storage" model is generally applicable, then geophysical detection of melt beneath volcanoes is likely a sign of imminent eruption. However, some arc volcanic centers have been active for tens of thousands of years and show evidence for the continual presence of melt. To address this seeming paradox, zircon geochronology and geochemistry from both the frozen lava and the cogenetic enclaves they host from the Soufrière Volcanic Center (SVC), a long-lived volcanic complex in the Lesser Antilles arc, were integrated to track the preeruptive thermal and chemical history of the magma reservoir. Our results show that the SVC reservoir was likely eruptible for periods of several tens of thousands of years or more with punctuated eruptions during these periods. These conclusions are consistent with results from other arc volcanic reservoirs and suggest that arc magmas are generally stored warm. Thus, the presence of intracrustal melt alone is insufficient as an indicator of imminent eruption, but instead represents the normal state of magma storage underneath dormant volcanoes.