Trace Element Partitioning in Mantle Minerals with Applications to Subsolidus Re-Equilibration and Thermobarometry

Sun, Chenguang

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Year:: 2014
Contributor:: Sun, Chenguang (creator); Liang, Yan (Director); Cooper, Reid (Reader); Parmentier, E. (Reader); Saal, Alberto (Reader); Watson, E. (Reader); Parman, Stephen (Reader); Brown University. Geological Sciences (sponsor)
Genre:: theses
Subject:: Clinopyroxene; orthopyroxene; REE; partitioning; subsolidus equilibration; thermobarometry; Garnet; Olivine; Plagioclase
Extent:: xix, 390 p.
DOI: https://doi.org/10.7301/Z0DN43DG

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Abstract:: Olivine, orthopyroxene, clinopyroxene, garnet and plagioclase are major rock-forming minerals in the Earth mantle and other planetary bodies. The partitioning of trace elements into these minerals is fundamental to understanding of the magmatic and subsolidus processes in the Earth and other planetary bodies. In Chapters 1, 2, 3, and 6, I present a new generation of lattice strain models for rare earth elements (REEs) partitioning between mantle minerals (clinopyroxene, orthopyroxene, garnet, olivine, and plagioclase) and basaltic melts that were calibrated against experimentally determined partitioning data. Application of these models to mantle melting and magma fractionation processes demonstrate: (1) temperature, pressure and mineral composition dominate REE partitioning between mantle minerals and basaltic melts; (2) the competing effects of temperature and composition lead to constant REE partition coefficients in pyroxene during adiabatic mantle melting; (3) the combining effects of temperature and composition result in significant variations in mineral-melt REE partition coefficients during solidification of a large magma body. In Chapter 4, I have developed generalized models for REE partitioning between coexisting mantle minerals. These models reveal that subsolidus re-equilibration can significantly redistribute REEs among minerals in peridotites. Without proper correction for subsolidus re-equilibration, the extents of melting for abyssal peridotites based on REE abundances in clinopyroxene can be significantly over-estimated. In Chapters 5 and 6, I present two new thermobarometers, a REE-in-garnet-clinopyroxene thermobarometer, and a REE-in-plagioclase-clinopyroxene thermometer, for mafic and ultramafic rocks. These thermobarometers are based on the temperature and pressure dependent REE partitioning between two coexisting minerals. The REE-based thermobarometers are unique because they can fully make use of all REEs as a group to constrain robust temperatures and pressures simultaneously. Due to the slower diffusion rates of REEs in minerals, the REE-based thermometers generally record higher closure temperatures than major element-based thermometers for samples that experienced cooling, but provide former equilibrium temperatures for samples that underwent heating. The REE-based thermobarometers can shed new light on thermal evolutions of mafic and ultramafic rocks from different tectonic environments.
Notes:: Thesis (Ph.D. -- Brown University (2014)

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Sun, Chenguang, "Trace Element Partitioning in Mantle Minerals with Applications to Subsolidus Re-Equilibration and Thermobarometry" (2014). Earth, Environmental and Planetary Sciences Theses and Dissertations. Brown Digital Repository. Brown University Library. https://doi.org/10.7301/Z0DN43DG

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Earth, Environmental and Planetary Sciences Theses and Dissertations

Theses and Dissertations for the Earth, Environmental and Planetary Sciences department.
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