Experimental and Field Constrains on the Physicochemical Evolution of the Lunar and Terrestrial Mantles

Dygert, Nicholas James

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Year:: 2015
Contributor:: Dygert, Nicholas James (creator); Liang, Yan (Director); Hirth, James (Director); Parman, Stephen (Reader); Parmentier, Edgar (Reader); Kelemen, Peter (Reader); Brown University. Geological Sciences (sponsor)
Genre:: theses
Subject:: armalcolite; HFSE; REE; Fe-rich pyroxene; lattice strain; Trinity Ophiolite; Josephine Ophiolite; Mariana Trench; TREE; REE-in-two-pyroxene; geothermometry; tectonics; Ilmenite; Hedenbergite; Trinity; Ophiolites; Plate tectonics; North Pacific Ocean--Mariana Trench
Extent:: 17, 408 p.
DOI: https://doi.org/10.7301/Z0PN940W

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Abstract:: Abstract of Experimental and Field Constraints on the Physicochemical Evolution of the Lunar and Terrestrial Mantles, by Nicholas Dygert, PhD., Brown University, May 2015. This thesis presents experimental and field studies that place constraints on the physical and chemical evolution of the lunar and terrestrial mantles. The first two chapters are experimental investigations of trace element partitioning in Fe and Ti rich lunar basaltic systems. Chapter one focuses on high field strength element (HFSE) partitioning between ilmenite, armaloclite, and basaltic melts, and demonstrates that HFSE partition coefficients strongly depend on the TiO2 abundance of the melt. Numerical models of lunar magma ocean crystallization and mantle melting predict distinct trace element fractionation for ilmenite and armaloclite-bearing lithologies. Chapter two focuses on trace element partitioning between clinopyroxene and Fe-rich basalts. Lattice-strain based partitioning models for rare earth elements and HFSE are developed which predict very different partition coefficients for Fe-rich systems compared to more magnesian systems. Chapter three is an experimental investigation of the rheological properties of ilmenite in dislocation creep. A flow law for ilmenite is presented predicting viscosities more than four orders of magnitude weaker than olivine at mantle stresses and temperatures. Experiments investigating ilmenite-olivine aggregates suggest dilute fractions of ilmenite significantly lower the viscosity of the aggregate. Chapter four explores incompatible trace element variations across a dunite-harzburgite-lherzolite-plagioclase lherzolite sequence at Trinity ophiolite. Major and trace element concentration gradients suggest melt fluxed out of the dunite into plagioclase lherzolite, forming the lithological sequence by melt-rock reaction. This study shows that tabular dunites can be sources for melt infiltration as well as extraction pathways. Chapter five applies a recently developed REE-in-two-pyroxene thermometer to peridotites from ophiolites with supra-subduction zone (SSZ) and mid-ocean ridge (MOR) tectonic affinities. Closure temperature models are developed and demonstrate that many samples from SSZ environments cool more slowly than those from MOR environments. Some MOR ophiolites appear to have experienced similar thermal histories as abyssal peridotites from slow and ultra-slow spreading centers, suggesting cooling rate is independent of spreading rate.
Notes:: Thesis (Ph.D. -- Brown University (2015)

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Dygert, Nicholas James, "Experimental and Field Constrains on the Physicochemical Evolution of the Lunar and Terrestrial Mantles" (2015). Earth, Environmental and Planetary Sciences Theses and Dissertations. Brown Digital Repository. Brown University Library. https://doi.org/10.7301/Z0PN940W

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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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