Description
Boron concentrations and isotopic composition of phlogopite mica, amphibole, and selected coexisting anhydrous phases in mantle-derived xenoliths from the Kaapvaal Craton were measured by secondary ion mass spectrometry in an effort to better understand the B isotope geochemistry of the subcontinental lithospheric mantle (SCLM) and its implications for the global geochemical cycle of B in the mantle. These samples display a wide, and previously unrecognized, range in their boron contents and isotopic compositions reflecting a complex history involving melt depletion and metasomatism by subduction- and plume-derived components, as well as late stage isotopic exchange related to kimberlite emplacements. Micas from ancient lithospheric harzburgite metasomatized by slab-derived fluids suggest extensive B-depletion during subduction, resulting in low-B, isotopically light compositions whereas kimberlite-related metasomatic products and a sample from the 2 Ga Palabora carbonatite have boron isotopic compositions similar to proposed primitive mantle. The results suggest that subduction of oceanic lithosphere plays a limited role in the B geochemistry of the convecting mantle.
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Details
Title
- Boron isotopic composition of the subcontinental lithospheric mantle
Contributors
- Guild, Meghan R (Author)
- Hervig, Richard L (Thesis advisor)
- Bell, David R. (Committee member)
- Mcnamara, Allen (Committee member)
- Arizona State University (Publisher)
Date Created
The date the item was original created (prior to any relationship with the ASU Digital Repositories.)
2014
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Note
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thesisPartial requirement for: M.S., Arizona State University, 2014
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bibliographyIncludes bibliographical references (p. 46-53)
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Field of study: Geological sciences
Citation and reuse
Statement of Responsibility
by Meghan R. Guild