Description
- Abstract:
- Various geological processes in the Earth can be studied using geochemistry. Melts derived from the mantle can be used to estimate the source composition to understand its physical properties such as its viscosity and seismic properties. Chemical tracers such as major, trace, volatile elements, and radiogenic isotopes can be used to understand the geological process that formed the mantle source of the melts as well as the shallow level processes that the melts have undergone. In addition, thermobarometry can be used to constrain the physical condition that a rock experienced. This dissertation research uses various methods to attempt to provide a better understanding of a wide range of geological processes in the Earth. Chapter 1 examines the generation process of mid-ocean ridge basalts (MORB) in the mantle and shallow level processes they undergo in the crust to make better estimates of the volatile contents in the upper mantle. After considering the effect of shallow level processes, the data suggests that Pacific MORB are mixtures of melts derived from a two-component upper mantle that are both peridotitic in lithology with the majority ultra-depleted in volatile and refractory incompatible elements while the rest is enriched. Chapter 2 investigates the poorly understood effects of re-melting of a metasomatized oceanic lithosphere on the chemical composition of MORB using the data from chapter 1. We show that some MORB might not originate from the asthenosphere, but instead originate from melting of a metasomatized oceanic lithosphere using geological evidences and geochemical modeling. In chapter 3, we developed parameterized lattice strain models for REE partitioning between amphibole and silicate melt. The newly developed models suggest that fractional crystallization of amphibole has a strong leverage on the REE concentrations in arc magmas and likely plays a key role in depleting its MREE relative to HREE and LREE. In chapter 4, we developed a REE-in-amphibole-plagioclase thermometer. Application of our REE-in-amphibole-plagioclase thermometer to oceanic and continental gabbros shows that REE-based thermometer records higher temperatures compared to major element thermometers, and we examine the physical meaning of the recorded temperatures.
- Notes:
- Thesis (Ph.D. -- Brown University (2016)
Access Conditions
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- Restrictions on Use
- Collection is open for research.
Citation
Shimizu, Kei,
"Volatile Content of the Earth’s Upper Mantle and Roles of Hydrous Phases in Igneous Processes"
(2016).
Earth, Environmental and Planetary Sciences Theses and Dissertations.
Brown Digital Repository. Brown University Library.
https://doi.org/10.7301/Z0X34VW0
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Earth, Environmental and Planetary Sciences Theses and Dissertations
Theses and Dissertations for the Earth, Environmental and Planetary Sciences department....