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In the Grenville age basement rocks of Virginia and North Carolina, nearly thirty Cryogenian volcanic/plutonic complexes have been recognized. A-type granites and rhyolites dominate the igneous complexes within the Cryogenian Magmatic Province (CMP), but compositional variations range from gabbro through syenites. The mineralogy, chemical composition and field data including microstructural emphasis suggests emplacement of these igneous complexes in an extensional setting. In this study U/Pb zircon ages of several plutons were determined using secondary ion mass spectrometry. The ages suggest two episodes of magmatism. An older episode (739 to 745 Ma) of magmatism includes White Oak Creek, Suck Mountain, and Amisville plutons. The younger episode (613 to 694 Ma) includes Dillons Mill, Stewartsville, Mobley Mountain, Rockfish River, and Fine Creek Mills plutons. These two age groups also display differences in geochemistry. In contrast to the older group of plutons, the younger plutons are characteristically more metaluminous, lower in silica, higher in aluminum and phosphate, lower agpatic index, less REE enrichment, minimal K-feldspar and accessory mineral fractionation. The distribution of the older group of plutons over a distance of nearly 600km requires the development of a crustal scale zone of extension. A space-time analysis suggests that these plutons represent a continental plume track similar to the White Mountain Magma Series. Plume head arrival ages of 765 to 754 Ma in the southern part of the region are measurably older than 735 to 705 Ma observed in the north, and yield a plate motion rate of ~2 cm/year. / Master of Science

<p dir="ltr">This study contributes to research involving wave rotor combustors by studying the</p><p dir="ltr">development of a hot jet issuing from a cylindrical pre-combustion chamber. The pre-chamber was</p><p dir="ltr">developed to provide a hot fuel-air mixture as an ignition source to a rectangular combustion</p><p dir="ltr">chamber, which models the properties of a wave rotor channel. The pre-combustion chamber in</p><p dir="ltr">this study was rebuilt for study and placed in a new housing so that buoyancy effects could be</p><p dir="ltr">studied in tandem with other characteristics. The effectiveness of this hot jet is estimated by using</p><p dir="ltr">devices and instrumentation to measure properties inside the pre-chamber under many different</p><p dir="ltr">conditions. The properties tracked in this study include maximum pressure, the pressure and time</p><p dir="ltr">at which an aluminum diaphragm ruptures, and the moment a developed flame reaches a precise</p><p dir="ltr">location within the chamber. The pressure is tracked through use of a high-frequency pressure</p><p dir="ltr">transducer, the diaphragm rupture moment is captured with a high-speed video camera, and the</p><p dir="ltr">flame within the pre-chamber is detected by a custom-built ionization probe. The experimental</p><p dir="ltr">apparatus was used in three configurations to study any potential buoyancy effects and utilized</p><p dir="ltr">three different gaseous fuels, including a 50%-50% methane-hydrogen blend, pure methane, and</p><p dir="ltr">pure hydrogen. Additionally, the equivalence ratio within the pre-chamber was varied from values</p><p dir="ltr">of 0.9 to 1.2, and the initial pressure was set to either 1.0, 1.5, or 1.75 atm. In all cases, combustion</p><p dir="ltr">was initiated from a spark plug, causing a flame to develop until the diaphragm breaks, releasing</p><p dir="ltr">a hot jet of fuel and air from the nozzle inserted into the pre-chamber. In the pressure transducer</p><p dir="ltr">tests, it was found that hydrogen produced the highest pressures and fastest rupture times, and</p><p dir="ltr">methane produced the lowest pressures and slowest rupture times. The methane-hydrogen blend</p><p dir="ltr">provided a middle ground between the two pure fuels. An equivalence ratio of 1.1 consistently</p><p dir="ltr">provided the highest pressure values and fastest rupture out of all tested values. It was also found</p><p dir="ltr">that the orientation has a noticeable impact on both the pressure development and rupture moment</p><p dir="ltr">as higher maximum pressures were achieved when the chamber was laid flat in the “vertical jet”</p><p dir="ltr">orientation as compared to when it was stood upright in the “horizontal jet” orientation.</p><p dir="ltr">Additionally, increasing the initial pressure strongly increased the maximum developed pressure</p><p dir="ltr">but had minimal impact on the rupture moment. The tests done with the ion probe demonstrated</p><p dir="ltr">that an equivalence ratio of 1.1 produces a flame that reaches the ion probe faster than an</p><p dir="ltr">equivalence ratio of 1.0 for the methane-hydrogen blend. In its current form, the ion probe setup</p><p>18</p><p dir="ltr">has significant limitations and should continue to be developed for future studies. The properties</p><p dir="ltr">analyzed in this study deepen the understanding of the processes that occur within the pre-chamber</p><p dir="ltr">and aid in understanding the conditions that may exist in the hot jet produced by it as the nozzle</p><p dir="ltr">ruptures. The knowledge gained in the study can also be applied to develop models that can predict</p><p dir="ltr">other parameters that are difficult to physically measure.</p>