Collaborative Research: High-resolution volcanic stratigraphy and geochemical evolution of the Galapagos Platform

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Ocean island volcanos are formed from repeated eruption of lavas from the Earth's mantle onto the overriding plate. Most mature ocean island systems comprise a nearly linear chain of volcanoes that increase with age in one direction, due to the tectonic plate migrating over the stationary magmatic source. However, the modern Galapagos volcanoes are situated on top of a large, shallow volcanic platform, which is atypical for an ocean island system. The presence of this massive platform has allowed the volcanic islands to remain subaerial for longer time periods, which has influenced biological speciation in the Galapagos. Despite this cursory understanding, very little is known about the construction, evolution, or composition of the Galapagos Platform. Thus, the outstanding goal of this research is to determine the compositions of lavas that make up the Galapagos Platform and relate them to spatial heterogeneity in the mantle source and the overlying islands. The project is in collaboration with UK scientists and will take place on a U.K. research vessel and use their remotely operated vehicle ISIS to sample the Galapagos Platform. This work represents an opportunity to collaborate with UK scientists on multidisciplinary oceanographic studies in the Galapagos. In addition, the ecosystems of the deep submarine environment around the Galapagos Islands remain virtually unexplored, despite the importance of the archipelago in evolutionary and biogeography studies, and the establishment of the Galapagos Marine Reserve, a UNESCO World Heritage Site. The PIs will collaborate with the Galapagos National Park, the Ecuadorian Navy's Oceanography Institute, and Charles Darwin Research Station, which is the principal organization supporting scientific research in the area. Graduate and undergraduate students will be trained during the project.Unlike many ocean island systems, the modern Galapagos Islands are situated on top of a large volcanic Platform that has been understudied compared to the subaerial portions of the islands. The goal of this work is to determine the chemical compositions of lavas forming the Galapagos Platform and relate those findings to the spatial heterogeneity in the mantle plume and the overlying islands with an overarching goal of understanding how the Galapagos Platform has formed in comparison to other ocean island systems (e.g., Hawaii). The ~21 days on-station field program using the ROV ISIS and the research vessel James Cook will be dedicated to sampling deep-sea corals (from a UK NERC funded portion of the proposal) and associated lavas from a broad spectrum of terrains along the margins of the platform, many never before sampled. The US-NSF component of this research involves ROV-based sampling and geological mapping of the volcanic stratigraphy at various locations along the margin of the Platform along with a comprehensive shore-based geochemical study of sampled lavas. These studies will allow an investigation of the volcanic emplacement processes involved in construction of the Platform and geochemical relationships between the submarine platform lavas and adjacent/overlying volcanic islands. During the planned research cruise, the most comprehensive and systematic in situ sampling of the volumetrically largest volcanic portion of the Galapagos Archipelago, the Galapagos Platform will be conducted. Results will test several important questions about the Galapagos Platform: i) is the Galapagos Platform spatially and vertically geochemically homogenous? ii) what is the relationship between the platform lavas, the overlying volcanic islands, and the overall evolution of the Galapagos Archiplelago. The field program is designed to map and sample several stratigraphic sections around the platform and will include detailed on-bottom observations, multibeam mapping, and in situ rock sampling. This will be followed by shore-based geochemical and textural analysis of lavas; including measuring major and trace element contents and radiogenic isotope ratios of the lavas. The results will be used to construct stratigraphic profiles of the Platform and compare submarine lava compositions to adjacent, overlying islands and deep-water lava flows to produce a comprehensive model for the formation of the Galapagos Platform.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.