RUI: Volcanic, Petrologic, and Geochemical Evolution of Darwin Volcano, Galapagos

University Of Alaska Anchorage Campus, Anchorage AK

Investigators

Abstract

Naumann EAR-0207962 The western Galapagos archipelago is one of the most active volcanic areas on Earth. This volcanologic, petrologic, and geochemical study of Darwin volcano is designed to test competing hypotheses for the growth of Galapagos-type shield volcanoes and their geochemical variations. The origin of their distinct "overturned soup plate" morphology is not merely a provincial issue: Galapagos-type shields may be characteristic of many seamounts and extraterrestrial volcanoes. Little is known of Darwin volcano, but several reconnaissance specimens from the lowermost flanks indicate that it is mostly made up of basalts with isotopic compositions are between those of lavas erupted from mid-oceanic ridges and those erupted from hotspots. Despite their isotopic character, the same lavas are rich in incompatible elements, more typical of ocean-island basalts. Darwin volcano was chosen for this study because although it remains virtually unstudied, it is situated between the two well-studied volcanoes of Alcedo and Wolf on Isabela Island. Alcedo and Wolf volcanoes represent two end members in the western Galapagos with respect to geochemical variation, elevation, shape, and caldera depth, and the study of Darwin volcano will allow for testing and refinement of models that predict the origin of these diverse geochemical systems and volcano morphologies. The goals of this project seek insights into the fundamental processes of ocean-island magmatism. These include: 1) documentation of the eruptive processes and the chronology, distribution and volume of eruptions that have constructed Darwin volcano; 2) determination of the petrologic and geochemical variation of Darwin's lavas in order to document the processes involved with the generation, storage, and eruption of magmas; and 3) a comparison of Darwin volcano with other well-studied western Galapagos volcanoes in order test the hypothesis that the magma supply rate to each volcano is the dominant control not only of the geochemical variation of lavas but also each volcanoes unique size, shape and caldera morphology.