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

Keywords

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

Subject Categories

Geochemistry | Volcanology

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.

Copyright

© Emily Elizabeth Salings

Open Access

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