Earth and Planetary Sciences ETDs

Publication Date

Winter 2022

Abstract

Triple oxygen isotope (TOI) measurements of mantle eclogite from the Orapa kimberlite pipe have reconstructed bulk rock '18O values from 4.587 to 9.542‰ (vs. VSMOW) and '17O from -0.075 to -0.044‰ (vs. VSMOW,  ~0.528). TOI values show increasing '18O with decreasing '17O, overlapping with modern measured altered oceanic crust. Orapa eclogite xenoliths with alkali enrichments show variable mantle-like and heavy 18O, consistent with subduction of seafloor altered basalt. Na# (Na/Na+Ca) in clinopyroxene for some xenoliths pairs with mantle-like oxygen, variable and extreme LREE enrichment, elevated Mg# and lower jadeite contents. These samples preserve records of eclogite melting, mantle interaction and recrystallization at lower temperatures with clinopyroxene having a pyroxenitic chemistry. 18Ocpx-gnt of most eclogites reflect disequilibrium in clinopyroxene rather than garnet, which is possibly an artifact of pyroxenite formation. This suggests metasomatism by fluids having mantle-like oxygen isotope compositions interacted within the lithosphere prior to kimberlite entrainment and eruption.

Degree Name

Earth and Planetary Sciences

Level of Degree

Masters

Department Name

Department of Earth and Planetary Sciences

First Committee Member (Chair)

Zachary Sharp

Second Committee Member

Jin Zhang

Third Committee Member

Brandon Schamndt

Project Sponsors

National Science Foundation

Language

English

Keywords

Triple Oxygen Isotopes, Mantle Eclogite, Xenoliths, Subcontinental Lithosphere, Kimberlite

Document Type

Thesis

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