The Colima Deep Seismic Experiment: Imaging the Magmatic Root of Colima Volcano

University Of Alaska Fairbanks Campus, Fairbanks AK

Investigators

Abstract

ABSTRACT Most of the world's explosive volcanism occurs at widely-spaced volcanic centers along convergent margins. Basaltic magmas from the subduction wedge are channeled to volcanoes separated by tens or hundreds of kilometers and evolve into silica-rich compositions associated with dome growth, pyroclastic flows and explosive eruptions. Decades of geochemical research have outlined a suite of processes which control the chemical and spatial evolution of these volcanoes. These ideas, which rely heavily on processes in the lowermost crust, have evolved with limited input from geophysics because the deep crust has been difficult to probe with seismics, gravity, and/or electromagnetics. The Colima Deep Seismic Experiment is one of the first to target the deep crustal processes which create discrete volcanoes and ultimately control eruptive behavior. In conjunction with the Observatorio Vulcanologico of Colima University in Mexico, the PI will install and maintain a seismic array for 18 months in the vicinity of Colima Volcano. The Observatorio is responsible for monitoring Colima Volcano, which is in the midst of an on-going eruption cycle, and seismicity throughout the state of Colima which has had two earthquakes greater than magnitude 7.5 in the last ten years. This project will be co-deployed with the arc-scale network of Grand and Ni (EAR #0335782) which is serendipitously centered on Colima. This array of intermediate-band instruments will be wider than a typical volcano monitoring array and is designed to optimize seismic tomography and receiver functions of the deep crust. Teleseismic data, together with seismicity in the local crust and subducting slab, will be used to map the temperature and melt conditions beneath Colima Volcano. The results will be interpreted in the context of existing geochemical models for the Colima complex to address two primary questions. (i) Is the location and longevity of an arc volcano governed principally by diapirism in the mantle wedge or by deep crustal conditions and Moho topography? (ii) What are the relative roles of magma ponding at the base of the crust and magma storage in the lower crust in controlling the evolution of subduction basalts into more silicic arc volcanics? These questions, though ideally suited to Colima, have implications at all arc volcanoes. This project is co-sponsored by the Americas Program in the International Division.