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TitleInitiation of the Wrangell arc: A record of tectonic changes in an arc-transform junction revealed by
File Size15.8 MB
Total Pages217
Table of Contents
Table of Contents
List of Figures
List of Tables
Chapter 1 -  Introduction
	Regional Tectonic Framework
		Wrangell Arc Geology- Underlying Rocks and Wrangell Arc Volcanic Rocks
	Previous Geochemical Work
		Western Wrangell Arc Volcanism: Geochemical Trends
		Eastern Wrangell Arc Volcanism: “Leaky” Strike-Slip
		Central Wrangell Arc Volcanism: Frederika Formation
		Age Progression of Wrangell Arc Volcanism
	>20 Ma Magmatism From the Central Wrangell Arc
	Sonya Creek Volcanic Field Study Area
		Structural Evidence for Local Extensional Faulting
Chapter 2 -  Methods
	Field Methods
	Analytical Methods
		Major, Trace, and Rare Earth Element Analysis
		Sr-Nd-Pb-Hf Isotope Analysis
		40Ar/39Ar Geochronology Analysis
Chapter 3 -  Results
	Field Relations, Physical Characteristics, and Geochronology
	Geochemistry Results
		Geochemical Classification
		Major Element Geochemistry
		Trace Element Geochemistry
		Rare Earth Element Geochemistry
		Primitive Mantle Normalized Multi-Element Diagrams
		Trace Element Ratios and Other Parameters: Sr/Y, (Sr/P)n, Ba/Nb, Eu/Eu*
		Cabin Creek Chemostratigraphy
	Sr-Nd-Pb-Hf Radiogenic Isotope Results
Chapter 4 -  Discussion
	Initiation of Wrangell Arc Magmatism
	Volcanic History of the Sonya Creek Volcanic Field (SCVF)
		Volcanic Architecture – Geochronology and Field Relations
		Geochemical Trends Through Time, and Implications For the Development of the Sonya Creek Volcanic Field
			Rocker Creek Lavas and Domes
				Source of Adakite-like Signature
			Silicic Lavas
			Intermediate Domes
			Sonya Creek Shield Volcano
				Cabin Creek Chemostratigraphy
				Flat Top
				Silicic Plug
			Young Creek Rocks
			Border Lavas
	Discussion of Radiogenic Isotope data
		Mixing Models
			Crustal Contamination of Primitive Magmas
			Contamination of the Mantle Wedge by Subducted Sediment
				Geologic Evidence for Oligo-Miocene Sediment Delivery to the Trench
				Mixing Models Between Mantle and Subducted Sediment
				Problems with the Mixing Model and Adjustment of Pb Concentrations
	Comparisons to Other Wrangell Arc Volcanic Centers
	Comparisons to Global Arc-Transform Settings
	Tectonic Implications for Wrangell Arc Initiation
		Temporal Connections to Regional Research
		Original Position and Subsequent Geographic Migration of the Wrangell Arc
	Final Thought
	Key Remaining Questions/Future Work
Chapter 5 -  Conclusions
	Appendix A -  Sample Locations and Petrographic Descriptions
	Appendix B -  Geochemical and Geochronologic Data
	Appendix C -   40Ar/39Ar Step-Heat Spectra

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