Geology Faculty Research

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Early Mount St. Helens Volcanic History

Most previous work and research done concerning the eruptive stages of Mount St. Helens (MSH), Washington focuses on the more recent eruptive period, the Spirit Lake Stage. There is a lack of information on the older eruptive stages including the Ape Canyon eruptive stage (300 to 35 ka), the Cougar eruptive stage (28-18 ka), and the Swift Creek eruptive stage (16-12.8 ka). This is problematic given the complexity of MSH. The main objective of this study is to obtain a better understanding of the magmatic processes that took place during the early history of MSH. These samples are being examined by electron microprobe (EPMA) and laser ablation-inductively coupled plasma mass spectrometry (LA-ICPMS) to determine the chemistry of the minerals and the melt inclusions. Researchers: Will Bradford, Kevin Gryger, Dr. Rocky Severs, Associate Professor of Geology.

Investigating the Origins of Adakites

Adakites are unusual volcanic rocks whose origin is not entirely clear. Senso stricto, adakites have geochemical characteristics that have typically been attributed to be generated by melting of subducted ocean crust. Adakites are important because they are often considered analogues of the tonalite-trondhjemite-granodiorite (TTG) suite plutonic igneous rocks that make up a significant portion of the Archean continental crust. Recent evidence suggests that adakites may represent complex mixtures that may have a continental crust component as well changing the model for how early continental crust formed. This study focuses on investigating adakites that were defined from Mount St. Helens, Washington. This project is aimed at examining the mineral chemistry and geochemistry of melt inclusions using the EPMA and LA-ICPMS to better understand how these adakites are formed. Researchers: Will Bradford, Kevin Gryger, Dr. Rocky Severs, Associate Professor of Geology.

Understanding Adirondack Garnet Formation

Garnets from the Adirondacks in upstate New York have been used economically over the past 125 years for their extreme hardness. They are also famous for because of their abnormally large size. The garnets are typically found in two different rock types: meta-gabbros and meta-anorthosites. Debate lingers whether these garnets are growing exclusively by metamorphic processes or also from partial melts. Four main areas that produce these garnets of interest include Gore Mountain, Warrensburg, Ruby Mountain and the Old Hooper Mine. The focus of this study is to better understand the growth and generation of garnets in different rock types by examining their geochemistry using the EPMA and LA-ICPMS and by experiments on the polyphase mineral inclusions found inside the garnets. Researchers: Steven Booty, Matt Remuzzi, T.J. Sarnoski Jr., Dr. Rocky Severs, Associate Professor of Geology.

Crystal Size Variation in Byram Diabase (NJ)

The Byram (NJ) diabase mafic igneous intrusion is a Jurassic-age unit associated with the failed continental rifting found in the Newark Basin. It is fault-bounded by shales of the Lockatong Formation. Hand samples from the Byram diabase appear to have significant differences in the crystal sizes over the span of 500 meters or less. Samples were collected from the diabase in February 2011 in order to determine whether there is a quantitative difference in grain size. Samples are currently being made into thin sections and will be analyzed by crystal size distribution (CSD) image analyses to make such a determination. CSD analyses will also provide constraints on the crystal growth rates and nucleation rates of the diabase. Researchers: Sarah Justus, Dr. Rocky Severs, Associate Professor of Geology

Emplacement of the Mount Powell Batholith in western Montana

The Flint Creek Range of western Montana lies in the footwall of the Anaconda Detachment and is characterized by a sequence of Cretaceous to Paleogene intrusive rocks. Intrusions are hosted by metasedimentary rocks of the Belt Supergroup and Phanerozoic supracrustal units. Significant positive aeromagnetic anomalies are observed along the eastern portion of the Flint Creek Range and may be correlated to individual intrusive phases or structures. This project is aimed at mapping and characterizing the magnetic properties of distinct phases of the Mount Powell Batholith. The project is funded by the USGS EDMAP program and is in collaboration with the Montana Bureau of Mines and Geology. Researchers: Shannon Ahern, Rudy Engel, and Dr. Jeffrey R. Webber, Assistant Professor of Geology.

Precambrian tectonics of the Absaroka-Beartooth Wilderness, southwestern Montana

Ongoing research in and around the Paradise Valley is concerned with the structural evolution and tectonic significance of deformed Precambrian rocks that spatially correlate to Cenozoic structures such as the Deep Creek fault. This work is focused on deciphering the relative and absolute timing of multiple phases of deformation in order to investigate the role of Precambrian structural inheritance during Cenozoic extension. Our primary approach integrates detailed field studies focused on documenting the structural architecture of features across the Paradise Valley with compositional analyses used to constrain the pressures and temperatures of metamorphism specific to different phases of deformation. Researchers: Alex Avelar-Flores, Andrew Del Turco, and Dr. Jeffrey R. Webber, Assistant Professor of Geology.

Strain analysis within the Bridger Mountains of southwestern Montana

Three-dimensional strain analyses of rocks collected from the Sevier Fold and Thrust Belt of the Helena Salient provide useful constraints on the localization of deformation during orogenic processes. Samples of the Rierdon Formation collected throughout the central and northern Bridger Mountains allowed for detailed analysis of internal strain variations with proximity to regional faults and folds. Our results document that distortion within these exposures is very limited and deformation is largely localized on brittle faults. Researchers: Anna Ternova, Timothy Shamus, and Dr. Jeffrey R. Webber, Assistant Professor of Geology.

Magnetism of the Athabasca Granulite Terrane, northern Saskatchewan Canada

Northern Saskatchewan is an incredible location to investigate the magnetic architecture of a 20,000 km2 region of exhumed lower continental crust. Specifically, aeromagnetic surveys across the Chipman domain of the east Athabasca mylonite triangle display large variations in magnetic total field strength that primarily correspond to bulk changes in the mode of ferrimagnetic minerals such as magnetite. My current research in Northern Saskatchewan is focused on investigating the metamorphic and structural context for magnetite production and break-down within the lower continental crust. By using these key relationships metamorphic conditions such as pressure, temperature, and oxygen fugacity may be partially constrained at the regional scale through aeromagnetic data. Furthermore, this information provides a better understanding of crustal magnetism on Earth that may also be used as a proxy for other celestial bodies. Researcher: Dr. Jeffrey R. Webber, Assistant Professor of Geology.