Date of Graduation

Spring 2017

Degree

Master of Natural and Applied Science in Geography, Geology, and Planning

Department

Geography, Geology, and Planning

Committee Chair

Gary Michelfelder

Abstract

The Mogollon-Datil volcanic field (MDVF), located in southern New Mexico, is the remnant of extreme and punctuated volcanism over ~12 m.y. of activity. The Bursum caldera is the youngest of three nested calderas in the Mogollon Mountains in the western MDVF. Here I present data from a high-silica, large volume tuff associated with the Bursum caldera, the Bloodgood Canyon Tuff (BCT). Extensive mapping by previous workers have provided a limited whole rock geochemical dataset and descriptions of the unit, but a detailed study had not been conducted. I present new whole-rock major- and trace-element analyses, Sr, Nd, and Pb isotope ratios, mineral chemistry, and petrographic textures to suggest an evolution model for the BCT. I suggest a model of assimilation and fractional crystallization of a dacite composition magma followed by the remobilization of a crystal mush by the upwelling of mafic magma at the peak of ignimbrite flare-up in southern New Mexico. Thermal disequilibrium induced by an intrusion of high-temperature mafic magma initiated the eruption of the BCT, and remobilization of this mush mixed with rhyolitic composition magma lenses within the mush that interacted locally with the amphibolitic-composition crust. Further destabilization of the magma chamber initiated a trapdoor style collapse of the Bursum caldera and erupted most of the remaining eruptible magma.

Keywords

ignimbrite, cumulate, continental arc, arc magmatism, magma evolution

Subject Categories

Geochemistry | Volcanology

Copyright

© Emily Elizabeth Salings

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