XS (2026-2028): Collaborative Research: Investigating intraplate melting processes in northwest New Zealand with seismic imaging

• whoi.edu

The goal of this study is to develop a better global understanding of the processes that produce intraplate volcanism by resolving the origins of the Holocene Auckland Volcanic Field (AVF). The AVF is spatially separated from the subduction zone arc, and its magmas do not bear obvious contributions from subduction-related melting. Neither are these magmas clearly connected to a lower mantle plume, based on existing seismic tomography and helium isotopes. Rather, geochemical data raise the possibility that the AVF magmas provide a global end-member case of mantle melting that emanates from transition zone depths, a class of intraplate volcanism that has recently emerged. However, other processes such as melting driven by upwelling related to lithospheric instabilities and small-scale convection cannot be ruled out, and even upwelling from the lower mantle needs to be further evaluated. New seismic data will be collected from a temporary array of 20 US seafloor broadband seismometers (OBSs). These stations will be complemented by New Zealand-based land arrays, and an OBS deployment from SUSTech (China). With the proposed array, seismic analyses will test for the presence or absence of seismic velocity and attenuation anomalies, transition zone discontinuity topography, and seismic anisotropy associated with the competing hypotheses. US work will be integrated with seismological and volcanological analyses by New Zealand collaborators and a SUSTech geodynamical modeling effort. Results from this synthesis will provide estimates of the depth extent of melting, volatile ascent, and the degree to which this intraplate volcanism is driven by processes in the lithosphere, transition zone, or both. A range of critical questions will be addressed, including: What is the thermal structure from surface to transition-zone depths? Does upwelling occur, and from what depth, and are lithospheric instabilities present? What pathways do fluids and melt take as they ascend, and how do those pathways interact with large-scale flow? How does volcanism far behind the arc interact with the subduction system, if at all? This project will support graduate and undergraduate students at Cornell and Brown. Results from the project will be incorporated in the outreach and teaching activities of the PIs. The proposed project will enhance international collaborations. The project will provide a better understanding of the deep drivers for volcanic hazards, including young (<1 ka) volcanism within the Auckland urban area.

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