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NDSU Geosciences Petrology 422/622 Spring 2004 STUDENT TERM PROJECTS Roark Franklund and Chad Weisenburger Title: Garnet-Biotite Geothermometry of Schist from the Black Hills, South Dakota Proposal: We have a sample of garnet schist from Keystone Pass in the Black Hills of South Dakota. Our goal is to give an estimation of pressure and temperature for the formation of this rock. We obtained data with the help of the SEM lab at University of Minnesota, via webcast. We will use this data in a garnet-biotite Fe-Mg exchange geothermobarometer to determine the metamorphic conditions under which this rock formed. Peter Schlater and Aric Olsen Title: Comparison of compositions of phenocrysts in cobbles, with sand from the Chalky Butte member of the Chadron Formation, western North Dakota. Proposal: We will look at feldspar sand grains, and feldspar phenocrysts in volcanic porphyry clasts, found in the Chalky Buttes Member of the Chadron Formation, Stark County, North Dakota. The purpose is to determine whether the feldspars are from the same provenace. Suggested source areas for these sand grains and porphyry are the Black Hills, South Dakota and/or the Absaroka Mountains in Montana. We will be looking at thin sections of a porphyry collected from the Black Hills, feldspar sand grains from the Chalky Buttes Member, and a porphyry from the Chalky Buttes Member. We will also be using SEM to determine feldspar chemistries. Michael Wright and Dan Stephney Title: Whole Rock chemical analysis of cobbles and sand from the Chalky Butte member of the Chadron Formation to determine provenance. Proposal:The Chalky Buttes member of the Chadron formation contains numerous inclusions of volcanic material. With no near by volcanic source nearby, their origins are a mystery. Several possibilities have been suggested to explain these inclusions, including: the uplift of the Rocky Mountains, eruption of the Yellowstone volcano, and the uplift of the Black Hills. For this project we will be laying the foundation for exploring the problem. Using x-ray refraction methods, we will obtain whole rock chemistries for twelve samples of ignimbrites and volcanic porphyries which can then be compared to the literature for the surrounding regional volcanic locations to determine their possible origins. Abbey Marohl and Stephanie Seeger Title: Metamorphic Rocks from the Minnesota River Valley, southern Minnesota Michael Nelson and Jennifer Thorstad Title: Origin of Devil's Tower Proposal: In our presentation we will discuss the general geology, mineralogy and, textures of Devils Tower, Wyoming. We will analyze the texture of the rock to determine the possible origin of Devils Tower. We will compare our data with the other two main hypotheses and come to our own conclusions about the origin. Jason Triplett and Troy Kummer Title: Phenocryst and Whole Rock Chemistries of Rhyolites from the El Cuy Region, Northern Patagonia, Argentina. Proposal:We will analyze phenocrysts within rhyolites from Argentina using a scanning electron microscope. With this information we can create a chemistry profile across both zoned and unzoned phenocrysts and compare that to the whole rock chemistry. Using this data we plan to come up with a hypothesis on the formation of the rhyolites with respect to magma chemistry and temperature and pressure of formation. Ashley Schmidt Title: Mylonitic Rocks from the El Cuy Region, Northern Patagonia, Argentina.

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