The Galapagos Archipelago and surrounding seafloor are unique in their construction and the center of much scientific investigation of processes of seafloor crustal construction. This research complements already on-going work in the Galapagos seeking to understand the nature and role of lineaments (Wolf-Darwin Lineament and Genovesa Ridge) on the seafloor and their ties to Galapagos volcanism and Pacific plate tectonics. Goals are to: (1) determine the age of volcanic rocks along the two lineaments using 40Ar/39Ar dating to understand the timing of eruptions in the area and (2) use trace elements compositions and ratios to determine mantle sources and melting regimes. These data, along with a compilation of other data from the literature and from recent cruises by German collaborators will be used to generate a set of seafloor tectonic maps showing the location and composition of volcanism in the Galapagos region over the past 10 million years. These maps will be used to produce a tectonic reconstruction of Galapagos hotspot-ridge interactions. Broader impacts of the work include international collaboration with German scientists and strong integration of research and education in terms of involving undergraduates in research activities which include having them participate in an oceanographic cruise, participate fully in research planning and implementation, and training in state of the art geochemical techniques. The Program notes that the project involves PIs from two undergraduate institutions.
Oceanic volcanism in the region of the Galápagos Islands reflects a complex interaction between the Galápagos hotspot and the Galápagos Spreading Center (GSC) located north of the islands. This research involved geochemical analyses and radiometric dating (40Ar-39Ar) of basaltic lavas that were recovered from submarine volcanoes (seamounts) during several previous oceanographic cruises that covered the regions between the main Galápagos platform and the GSC. Trace elements compositions of the lavas were determined at Colgate University and these allow us to differentiate between a hotspot and the spreading center source. The eastward direction of the Nazca tectonic plate on which the seamounts erupted combined with the age of the lavas allows us to backtrack the volcanoes to the location that they originally formed. Our findings demonstrated that a set of five seamounts on the northeast edge of the current islands formed between 1.0 and 3.8 million years ago. Some of these seamounts appear to be drowned islands whose original eruption location is well east of the current location of the hotspot. The lava compositions of these Northeast Seamounts are also very different from the present-day hotspot lavas on Fernandina Island. They appear more like mid-ocean ridge lavas, which indicates that the present day interaction between the hotspot and the GSC has persisted at least four million years. These former islands also allow evolutionary biologists to determine dates and locations of potential habitats for species to evolve. Lastly, this project gave four undergraduate students the opportunity to participate in exciting and relevant research.
