Physical Sciences and Mathematics Commons^™

Pluton Zonation Unveiled By Gamma-Ray Spectrometry And Magnetic Susceptibility; A Case Study Of The Sheeprock Granite, Western, Utah, Paul D. Richardson

Theses and Dissertations

A radiometric survey of the zoned 21 Ma, A-type Sheeprock granite, western Utah, combined with measurements of magnetic susceptibility and field observations were analyzed using a geographic information system. The intrusion spans 25 square km and is roughly eliptical in shape with its long axis trending northwest. Concentration maps (composed of more than 500 survey stations) of eU, eTh, texture, magnetic susceptibility, color, and joint density help to constrain magmatic and post-magmatic processes related to its chemical and physical zonation. Uranium ranges from 3.9 to 26.9 ppm (mean 12.7) and thorium from 1.7 to 125.7 ppm (mean 45.5). Similarities in …

Platinum Group Element Mineralization In "Ballrooms" Of The J-M Reef Of The Stillwater Complex, Montana, Matthew P. Harper

Theses and Dissertations

The J-M Reef of the Stillwater Complex, Montana (a large layered mafic intrusion), is one of the highest grade platinum group element (PGE) deposits known in the world, producing primarily palladium and platinum in a 3.4:1 ratio. "Ballrooms" of the Stillwater Complex are anomalously wide areas within or stratigraphically below the J-M Reef that host platinum group element mineralization. Ballrooms have two typical morphologies (type 1 and type 2); the first is an abrupt thickening of the mineralization that extends below the Reef Package and the second is a gentle widening of the Reef Package and associated reef mineralization to …

Modeling The Hydrogeochemistry Of Denitrification In The Elk Valley Aquifer, Paul A. Skubinna

Theses and Dissertations

Nitrate (NO₃¯) in groundwater has become an important tissue in the last few decades. It is known to cause methemoglobinemia, commonly known as “blue baby syndrome,” and is suspected of being a carcinogen. The most common sources for dissolved NO₃¯ in shallow groundwater include excessive application of nitrogenous fertilizers, misuse of septic systems, improper disposal of domestic wastewater or sludge, and livestock waste.

Denitrification is the most effective sink for NO₃¯. The Elk Valley aquifer (EVA) of eastern North Dakota is known to support denitrification. The objective of this study was to gain a better understanding of the geochemical processes …

Discontinuities In The Icebox Formation (Ordovician), Williston Basin, North Dakota And Montana, Aaron J. Ulishney

Theses and Dissertations

The Ordovician Winnipeg Group is composed of three formations; in ascending order, the Black Island Formation, the Icebox Formation, and the Roughlock Formation. The Icebox Formation is largely composed of shale. This work shows that discontinuities and coarser facies exist within the Icebox Formation and that they are traceable throughout the subsurface of North Dakota and eastern Montana. This work also illustrates possible sea-level changes during the deposition of the Icebox Formation along with probable source areas providing detrital sediments into the study area.

Gamma-ray wireline logs were used to distinguish the formations of the Winnipeg Group from each other, …

Design And Evaluation Of A Modified In Situ Mesocosm To Study Denitrification In The Karlsruhe Aquifer, Jason M. Warne

Theses and Dissertations

To simplify the in situ mesocosm (ISM) design given in Schlag (1999), a modified ISM was designed and built in which a 6-inch long sand point replaces three 16-inch diameter screens. The modified design also includes an optional submersible pump mounted on top of the ISM chamber, making it capable of applications at depths greater than those attainable using a peristaltic pump from the ground surface. Two ISMs, one the original design (0-ISM) and the other the modified design (M-ISM) with an optional submersible pump, were installed in the Karlsruhe aquifer, near Minot, ND, in late June, 2003. Tracer tests …

A Boundary Element Method For Thermo-Poroelasticity With Applications In Rock Mechanics, Qiang Zhang

Theses and Dissertations

Coupled thermal and poromechanical processes play an important role in many geomechanics problems, such as borehole stability analysis and studies of initiation and propagation of hydraulic fractures. Thermal effects, as well as hydraulic effects, can greatly change the stresses and pore pressure fields around an underground opening. This is due to the fact that thermal loading induces a volumetric deformation because of thermal expansion/contraction of both the pore fluid and the rock solid. Volumetric expansion can result in significant pressurization of the pore fluid. In order to take into account the influence of temperature gradients on pore pressure and stresses, …