Some aspects of the chemistry and volcanology of hotspot volcanoes: From seamounts to ocean islands

Abstract

The products of hotspot volcanoes vary widely in composition, eruptive style, volume, and emplacement conditions, and a great diversity of tools is required to unravel their origin and evolution. This dissertation investigates hotspot volcanoes and other features of oceanic intraplate volcanism on the Pacific plate, by applying geochemistry, stratigraphy, and video analysis across four independent projects. Chapter 2 examines the chemistry of the Cretaceous Naifeh-Plumeria seamount chains, revealing FOZO-like isotopic signatures in the upper mantle, suggesting their formation through small-scale convection rather than classic plume activity. Chapter 3 investigates the Cretaceous Wake seamounts in the West Pacific Seamount Province, identifying two isotopically distinct groups: one linked to the long-lived Rurutu-Arago hotspot and the other to shallower, plume-unrelated mantle sources, providing constraints for reconstructing Pacific plate motion prior to 80 Ma. Chapter 4 provides new insights into the eruptive history and hazards of rejuvenated volcanism on Oʻahu, Hawaiʻi, through a detailed stratigraphic study of the Koko Rift System (~67 ka). Chapter 5 introduces webcam videography for quantifying eruption parameters, applied to the 2022 Mauna Loa summit lava fountaining. By tracking fissure growth, lava fountain heights, and eruption flux rates through webcam footage, this study establishes a cost-effective tool for monitoring eruptions in near-real time. In summary, the study of chemical and physical properties of hotspot volcanoes conducted in this work provides a better understanding of the broader interplay of deep mantle structures and mantle convection, surface processes and eruption dynamics.