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Journal of Undergraduate Research

Keywords

trace element analysis, quartz grains, Wah Wah Springs, granodiorite intrusion

College

Physical and Mathematical Sciences

Department

Geological Sciences

Abstract

The Wah Wah Springs Tuff and the Wah Wah Springs Intrusive Granodiorite are both part of the Indian Peak caldera complex in southwest Utah, an area of intense volcanic activity 30 million years ago. This time period is known for explosive silicic activity due to the subduction of the Farallon Plate along North America’s western edge. In the eruption connected with the Wah Wah Springs an estimated 5,900 km3 of magma came out of the Earth, making it one of the largest known explosive eruptions in our planet’s history. This massive eruption was partially dependent upon the changing temperatures and pressures of the magma body as it rose through he crust. These changes are recorded in the rocks through a disequilibrium texture known as zoning. Zoning is found in microscopic crystals of igneous rocks and can reveal the history of a magma body. In the case of the Wah Wah Springs Granodiorite, it is thought that variable abundances of titanium in the mineral quartz are responsible for dark and bright zones seen within individual grains when viewed in a scanning electron microscope using a cathodoluminescence detector (Figure 1). These small changes in the abundance of Ti can be used to calculate paleo temperatures and pressures thanks to recent experiments of Huang and Audetat1. H&A developed an equation that can be used as a geothermometer and geobarometer given the abundance of Ti measured in ppm in quartz.

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