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Dissertation
Analytical applications in Geoscience: a rapid preparation and analysis method for reference materials and magma storage and transport in Snæfellsnes, Iceland
University of Iowa
Doctor of Philosophy (PhD), University of Iowa
Autumn 2024
DOI: 10.25820/etd.007728
Abstract
Trace elements are useful as a cutting-edge tool that can be critical to understanding the evolution of many earth and planetary systems, including melt generation and differentiation-assimilation processes in magmatic rocks, as discriminators of tectonic environment in igneous and sedimentary rocks, to quantify rates of processes through diffusion modeling, and for quantification of intensive parameters like temperature and pressure.
The first chapter focuses on development and statistical precision of a new multi-element analytical method that combines XRF lithium borate preparation and analysis with laser ablation ICP-MS analysis techniques, to allow rapid sample throughput in a cost-efficient manner. The proposed study relies on reducing the physical size of the samples. Statistical analysis in this study shows that the reduced size ‘bits’ and ‘shards’ are statistically and chemically interchangeable.
The second chapter focuses on evaluation of the accuracy of the XRF preparation-LA-ICP-MS analysis method. Comparison of analyzed well-characterized certified reference materials with their certificate/preferred values shows good agreement among major, minor and REE elements, with correlation confidents of >0.95 for most elements. The XRF-LA-ICP-MS method is also applied to poorly constrained or lab standards, which provides more comprehensive trace element data that is of use to the wider geochemical community.
The third chapter focuses on electron microprobe-based methods applied to olivine diffusion chronometry and geothermobarometry from two eruptions in the central Snæfellsnes peninsula and application of geothermobarometry methods on a compiled database of glass and cpx analyses to assess any variations in magma storage across the peninsula. Results show that storage and transport in the non-extensional off-axis location (Snæfellsnes) has a complex multi-storage system, with storage at multiple levels from the Moho to upper crust, ascent rates similar to those at the main spreading axis, a deepening storage trend of cpx rim formation from east to west along the peninsula (5 km to 15 km), and no deep cpx rim formation in the east but deep rim formation moving west from the mid-peninsula (~22°W).
Details
- Title: Subtitle
- Analytical applications in Geoscience: a rapid preparation and analysis method for reference materials and magma storage and transport in Snæfellsnes, Iceland
- Creators
- Lawrence Kenneth Squire Horkley
- Contributors
- David Peate (Advisor)Emily Finzel (Committee Member)C. Tom Foster (Committee Member)Bradley Cramer (Committee Member)Emily Walsh (Committee Member)
- Resource Type
- Dissertation
- Degree Awarded
- Doctor of Philosophy (PhD), University of Iowa
- Degree in
- Geoscience
- Date degree season
- Autumn 2024
- DOI
- 10.25820/etd.007728
- Publisher
- University of Iowa
- Number of pages
- xiii, 956 pages
- Copyright
- Copyright 2024 Lawrence Kenneth Squire Horkley
- Grant note
- Analytical work for this study was supported by NSF grant #1550415 (PI David W Peate), by student funding from the Geological Society of America (PI Horkley) and by development support from the Materials Analysis, Testing and Fabrication (MATFab) facility at the University of Iowa.
- Comment
- This thesis has been optimized for improved web viewing. If you require the original version, contact the University Archives at the University of Iowa: https://www.lib.uiowa.edu/sc/contact/
- Language
- English
- Date submitted
- 11/05/2024
- Description illustrations
- illustrations, tables, maps, graphs
- Description bibliographic
- Includes bibliographical references (pages 270-283).
- Public Abstract (ETD)
- Trace amounts of elements are useful as a cutting-edge tool that to understanding the evolution of many earth and planetary systems and are critical in this project. The first chapter focuses on development and precision of a new multi-element analytical method that combines XRF preparation methods and laser ablation analysis, to allow rapid sample throughput in a cost- efficient manner. The physical size of the samples is reduced to speed up the process and statistical analysis in this study shows that the reduced size ‘bits’ and ‘shards’ are statistically and chemically interchangeable. The second chapter focuses on the accuracy of the XRF-laser ablation method. Comparison of analyzed, well-characterized certified standards with their published values shows good agreement among most elements, with correlations of >0.95 for most elements. The XRF-laser ablation method is also applied to poorly constrained standards, which provides more comprehensive trace element data that is of use to the wider geochemical community. The third chapter focuses on electron microprobe-based methods applied to the rate of element mobility in olivine and element-based temperature and pressure calculations from two eruptions in the Snæfellsnes peninsula. Additionally, element-based temperature and pressure calculations on a database of glass and clinopyroxene data are used to assess any variations in where magma is stored under the peninsula. Results show that magma movement and storage in the non-spreading axis location (Snæfellsnes) is complex, with storage at multiple depths in the crust. The rates of movement of magma are similar under Snæfellsnes to those calculated at the main spreading axis in Iceland. Mineral pressure calculations showing where clinopyroxene rims are crystallizing, show a deepening trend from east to west along the peninsula (5 km to 15 km), and no deep clinopyroxene rim formation in the east of the peninsula, but deep rim formation moving west from the mid-peninsula (~22°W).
- Academic Unit
- Earth and Environmental Sciences
- Record Identifier
- 9984774457602771
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