Publication Date

5-2023

Date of Final Oral Examination (Defense)

December 2022

Type of Culminating Activity

Thesis

Degree Title

Master of Science in Geosciences

Department

Geosciences

Supervisory Committee Chair

Dorsey Wanless, Ph.D.

Supervisory Committee Member

Mark Schmitz, Ph.D.

Supervisory Committee Member

Darin Schwartz, Ph.D.

Abstract

The Naifeh and Plumeria seamount clusters, which consist of 10 submarine volcanoes located ~220km north of the Northwest Hawaiian Ridge, were mapped and sampled by the E/V Nautilus expedition NA101 in 2018. The origin of these seamounts is unknown, but their unique orientation and location imply several possible mechanisms of formation. Four possible mechanisms of formation include: 1) off-axis upwelling of the Hawaiian mantle plume, 2) ancient arch volcanism, 3) intraplate extension and deformation, 4) hotspot volcanism. Investigating the origin of these seamount clusters will better constrain the composition of the underlying mantle, as well as the depth and extent of melting required to generate these large volcanic structures and provide insight into the interaction between mantle plumes, the upper mantle, and surrounding lithosphere.

Here we present major and trace element compositions of 28 samples from the five Naifeh seamounts and 22 samples from the five Plumeria seamounts. Major element data indicate that all lavas are alkalic, ranging from trachybasalts to trachyandesites. The lavas from both seamount chains have low MgO contents (0.62-2.31 wt.%) and are cogenetic. Trace element patterns are relatively consistent throughout both chains, suggesting the lavas came from a similar mantle source and extent of partial melting. Naifeh and Plumeria both have enriched incompatible trace element compositions compared to mid ocean ridge basalts (MORB), suggesting their source is not typical depleted upper mantle, but more similar to a mixture of ocean island basalt (OIB) and enriched-mid ocean ridge basalt (EMORB), and normal MORB. Thus, it is not likely these were formed simply from intraplate extension and deformation as has been suggested for the nearby Musician seamounts or from Cretaceous crust building. The seamounts are also distinct from North and South Arch lavas, suggesting that they were not created from melting beneath the flexural bulge associated with plate loading. Instead, Naifeh and Plumeria have compositions similar to lavas from the Line Islands and Rurutu, which have been explained by multiple hotspots stemming from the South Pacific Superswell or small scale sublithospheric convection. Naifeh and Plumeria also have compositional similarities with the Shatsky, Ojin, and Hess rise seamounts, which are hotspot derived seamounts erupted during the early to mid-Cretaceous. Based on this, we suggest that the Naifeh and Plumeria seamounts originated from a hotspot source emanating from the South Pacific Superswell with the incorporation of recycled oceanic crust or are a product of small scale sublithospheric convection.

DOI

https://doi.org/10.18122/td.2070.boisestate

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