Award Date

5-1999

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Geoscience

Advisor 1

Terry Spell

First Committee Member

Terry L. Spell, Chair

Second Committee Member

Rodney Metcalf

Third Committee Member

Eugene Smith

Fourth Committee Member

Kathleen Robins

Fifth Committee Member

Philip Kyle

Number of Pages

163

Abstract

Around 82% of mapped Bearhead Rhyolite (Main Cluster) and Peralta Tuff appears to have been derived from a relatively long-lived (~680 ka), large, shallow (<10 km below Earth's surface) magma chamber that did not produce a caldera-forming eruption. Although volatile contents were great enough (~ wt.% H2O), no large-scale explosive eruptions occurred because magma may have been tectonically vented. The lack of systematic chemical variation within the Main Cluster with time during this ~680 ka interval may imply that erupted magmas were physically separated from each other by fault-formed cupolas in the roof of the magma chamber. These results are significant because Bearhead Rhyolite may represent a poorly documented style of silicic volcanism that may be more common than realized.

The remaining ~18% of mapped Bearhead Rhyolite is chemically and/or temporally distinct from the majority of Bearhead Rhyolite and is located in the southwest periphery of the field area.

Keywords

Geochemistry; Geological time; Magmas; New Mexico -- Jemez Region; Rhyolite; Volcanic ash, tuff, etc.; Volcanism

Disciplines

Geochemistry | Geology | Volcanology

Language

English

Comments

(Refer to PDF file for exact formulas.)


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