Investigating Volcanic Eruptions at the Seamount Tafu: Chemical and Geographic Variation Within the NELSC

Abstract

Most eruptions on Earth are likely submarine (Rubin et al., 2012); however, relatively little is known about deep-sea eruptions due to the difficulty in detecting and observing them. The Northeast Lau Spreading Center (NELSC) in the Northeast Lau Basin is an excellent location to study these deep-sea processes, as it is one of the most volcanically active submarine provinces on Earth. This thesis presents reports on three known eruptions that occurred at the NELSC seamount Tafu between 2006 and 2017 and compares them to a 2008 eruption that occurred at Tafu’s next-ridge neighbor, Puipui (Baker et al., 2011). The new Tafu eruption deposits were identified by bathymetric changes of up to 100m between repeated multibeam sonar surveys conducted over the past two decades. The Schmidt Ocean Institute cruise FK171110 set out in 2017 to investigate the Northeast Lau Basin using both autonomous underwater vehicle (AUV) and ship-based bathymetric mapping. During this cruise, the remotely operated vehicle SuBastian conducted several dives, including two at the NELSC: one on Tafu’s north flank, and one on Tafu’s south flank. Photos and videos were taken throughout the dive, and rock and sediment samples were collected. This study investigates the geochemistry, petrology, and morphology of samples collected, and how this relates to the locations in which they were emplaced. Pairing observations made from photo/video evidence from the dives with both electron microprobe analysis and Raman microscopy allows for reconstruction of magma formation history and eruption conditions.