Publication Date

8-2019

Date of Final Oral Examination (Defense)

7-31-2019

Type of Culminating Activity

Dissertation

Degree Title

Doctor of Philosophy in Geosciences

Department

Geosciences

Major Advisor

V. Dorsey Wanless, Ph.D.

Advisor

Mark Schmitz, Ph.D.

Advisor

Brittany Brand, Ph.D.

Advisor

Corey Wall, Ph.D.

Abstract

Lavas erupted at ocean island volcanoes are classically used as probes of the deep Earth, with ultimate goals of discerning the compositional heterogeneity, structure and dynamics of the Earth’s mantle. However, sampling restricted to volcanic islands and large, submarine volcanic constructs alone likely results in limited spatial resolution of the mantle’s composition and structure, owing to homogenization in sub-island magma reservoirs. Further, islands provide poor temporal resolution given that their multigenetic construction can overprint any time progressive chemical variations and they subside with age making detailed sampling difficult. For my dissertation I investigate whether seamounts surrounding islands in the Galápagos Archipelago preserve a more spatially distributed record of punctuated, point-source magmatism providing a different perspective on these deeper processes. The first chapter investigates the physical characteristics of the near-island seamounts resulting in the derivation of a 0.2-0.4 m/ka subsidence rate for the archipelago. Chapters two and three evaluate the magmatic relationship of the seamounts to the islands that they surround. From this, it appears seamounts are closely related to the islands but do indeed preserve a higher resolution picture related to evolution and mantle zonation. An important component of my dissertation has been to mix and calibrate a Pb double spike for internal mass-dependent fractionation correction of Pb isotope measurements at Boise State University in an effort to collect highly accurate and precise isotopic data of the seamount lavas to complement the high-resolution sampling of the seamounts themselves (Chapter 4). Finally, the fifth chapter uses high precision Pb isotopes to show that all of the isotopic end members in the Galápagos can be produced from the recycling of a single oceanic package.

DOI

10.18122/td/1579/boisestate

Available for download on Friday, August 27, 2021

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