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Publication Date

2021

First Advisor

Sarah Mazza

Document Type

Honors Project

Degree Name

Bachelor of Arts

Department

Geosciences

Keywords

Geoscience, Geochemistry, Tungsten, Thrym Complex, Greenland, Archean, Tungsten mobilization, LA-ICP-MS

Abstract

The significance of Earth’s tectonic system is grounded in its unique appearance in the solar system, and its influence over the planet’s geologic, atmospheric, and hydrological cycles. Despite its profound scientific importance, the precise evolution of the modern tectonic system on Earth is not yet fully understood. The manner of occurrence, or even existence, of tectonics throughout the Archean is an area of continued study and debate. In modern subduction zones, stable tungsten isotope fractionation has successfully been used to identify the state of subduction. This is because the fluid mobile nature of tungsten results in the heavy 184W isotope preferentially leaving the slab during dehydration, and in cases where the slab melts (e.g. hot subduction zones or rear arc magmatism) there is an increase in proportion of the light isotope (183W). The samples used in this study are being analyzed in an effort to apply this technique to identify if modern style tectonics onset in the Archean. However, because of the fluid mobile nature of tungsten, tungsten can be re-mobilized in post-petrogenesis processes like metasomatism. Therefore, the state of tungsten remobilization needs to be identified first to confirm that tungsten in the sample reflects the primary rock forming processes. This was done by petrographic and geochemical analysis of mineral phases of Archean samples from SE Greenland that have been proposed to represent the root of a magmatic arc. The geochemical analysis necessary for the tungsten investigation resulted in the first LA-ICP-MS trace element analysis preformed at Smith College. Therefore, this manuscript also details the method development for in-situ LA-ICP-MS geochemical trace element analysis.

Rights

©2021 Victoria Eileen Devlin McLoughlin

Language

English

Comments

49 pages : color illustrations, color map Includes bibliographical references (pages 34-35)

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