Award Date

12-1995

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Geoscience

First Committee Member

Rodney V. Metcalf, Chair

Second Committee Member

Eugene I. Smith

Third Committee Member

Wanda J. Taylor

Graduate Faculty Representative

Donna Weistrop

Number of Pages

120

Abstract

The Dolan Springs volcanic field (DSV), of northwestern Arizona, is dominated by andesite and basaltic-andesite flows and breccias, with minor amounts of basalt, rhyolite, and ash-flow tuff. Geochemistry is used here as a tool to evaluate the roles and contributions of the lithospheric and asthenospheric mantles to magmatism related to Miocene extension in the Colorado River extension corridor (CREC). The majority of synextensional volcanic rocks in the DSV are geochemically similar to regional trends, but rare tholeiitic basalts erupted near the end of extension. The tholeiites have trace element signatures similar to ocean island basalt (OIB), but have isotopic values indicative of a source in the lithosphere. The tholeiites represent the endpoint in a progressive decrease in the depth of lithospheric melting (22-8 Ma) that occurs just prior to the onset of asthenospheric volcanism at 6 Ma. Using geochemical arguments, models are presented here for trace element stratification in the lithospheric mantle and magma genesis in the CREC.

Keywords

Arizona -- Dolan Springs; Geochemistry; Igneous rocks; Magmas; Miocene Geologic Epoch

Disciplines

Geochemistry | Geology | Volcanology

Language

English

Comments

Signatures have been redacted for privacy and security measures.


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