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Rare Earth Element Transport In The Yucca Mountain Region, Liqiong Zhang

UNLV Theses, Dissertations, Professional Papers, and Capstones

In sync with environmental pollution of solutes in nature, from source, process to consequence, geochemical processes (leaching and sorption) and hydraulic transportation of the rare earth elements (REEs) have been investigated at Yucca Mountain (YM), Nevada. This research includes the leaching behavior of trace elements (including REEs) from aquifer rocks, the surface complexation reactions of REEs in synthetic groundwater, and transportation of reactive REEs in the local-scale groundwater system of YM. This dissertation includes three projects. These studies indicate that surface complexation reactions may retard the transportation of REEs along groundwater paths in YM, which suggests a similar behavior of …

The Interaction Of Rock And Water During Shock Decompression: A Hybrid Model For Fluidized Ejecta Formation, Audrey Hughes Rager

UNLV Theses, Dissertations, Professional Papers, and Capstones

Crater and ejecta morphology provide insight into the composition and structure of the target material. Martian rampart craters, with their unusual single-layered (SLE), double-layered (DLE), and multi-layered ejecta (MLE), are the subject of particular interest among planetary geologists because these morphologies are thought to result from the presence of water in the target. Also of interest are radial lines extending from the crater rim to the distal rampart of DLE craters. Exactly how these layered ejecta morphologies and radial lines form is not known, but they are generally thought to result from interaction of the ejecta with the atmosphere, subsurface …

Carbon Isotopic Fractionation Across A Late Cambrian Carbonate Platform: A Regional Response To The Spice Event As Recorded In The Great Basin, Jonathan Lloyd Baker

UNLV Theses, Dissertations, Professional Papers, and Capstones

Geochemical models have suggested that the late Cambrian was characterized by a greenhouse climate with high pCO2. Furthermore, stableisotope analyses within the Great Basin have documented a large carbonate isotope (δ13Ccarb) excursion, known as the Steptoean Positive Carbon Isotope Excursion (SPICE). This event has been documented globally, and is interpreted as having resulted from enhanced organic carbon burial. Unless the size of carbon reservoirs in the Cambrian ocean was significantly different from those of the Cenozoic, this forcing should have resulted in a comparable carbon-isotope excursion in organic matter (δ13Corg). It is also predicted that increased organic carbon burial would …

Age And Petrogenesis Of The Roaring Mountain Rhyolites, Yellowstone Volcanic Field, Wyoming, Kathleen Marie Wooton

UNLV Theses, Dissertations, Professional Papers, and Capstones

Extracaldera rhyolites in the Norris-Mammoth Corridor of the Yellowstone Volcanic Field (YVF) appear to be unrelated to intracaldera volcanism, resulting instead from a new crustal magma source derived from northeastward propagation of the Yellowstone “melting anomaly.” The youngest extracaldera rhyolite unit, the Roaring Mountain Member (RM), is chemically distinct from the previous extracaldera lavas, reverting to more primitive compositions.

This study suggests that the majority of the RM rhyolites erupted from the same large-scale silicic magma system. Based on geochemistry and 40Ar/39Ar geochronology, the Crystal Spring mingled rhyolite and Obsidian Cliff rhyolite erupted concurrently at 59.1 ± 2.0 ka. The …

Late Paleozoic Deformation In The Osgood Mountains And Dry Hills, Northern Nevada, Samuel A. Siebenaler

UNLV Theses, Dissertations, Professional Papers, and Capstones

Pennsylvanian (IP) and Permian (P) deposits (Etchart Formation) and structures in the northern Osgood Mountains and Dry Hills are identified and interpreted to reconstruct a late Paleozoic tectonic history for the time between the Antler and Sonoma orogenies. Mapping, field observations, fusulinid-based unit ages, and structural analysis are used to identify three fold and fault sets, a fault set, a fold set, and at least two angular unconformities. The faults consist of N to S striking normal faults (fault set 1) that are cross cut by WSW-ENE striking thrust faults (fault set 2). Fault sets 1 and 2 are cross …

Sequence And Chemostratigraphy Of The Middle Cambrian Succession In Nevada And Utah, Robyn A. Howley

UNLV Theses, Dissertations, Professional Papers, and Capstones

The House Range Embayment of western Utah and eastern Nevada was a prominent topographic feature on the passive margin of western North America during the middle and late Cambrian. In this study, detailed documentation of sequence boundaries, and their intervening sequences across a platform-to-basin transect of the House Range Embayment was used to establish a sequence-stratigraphic framework from which the depositional history of the embayment was deciphered. This framework was then used to test the hypothesis that the House Range Embayment formed by tectonic subsidence. In addition, the chemostratigraphic (δ13Ccarb) record across the embayment was analyzed within this framework to …

The Effects Of Contact Metamorphism On The Host Rocks For Carlin-Type Mineralization At The Getchell Development, Nevada, Usa, Nathan C. Eck

UNLV Theses, Dissertations, Professional Papers, and Capstones

Carlin-type gold deposits (CTGDs) result from low to moderate temperature hydrothermal systems which form replacement bodies in carbonate or calcareous host rocks. The Getchell CTGD is located on the Getchell trend in north central Nevada. The Eocene age mineralization is locally hosted within the metamorphic aureole of the Cretaceous age Osgood stock. Previous studies have noted that the effects of the contact metamorphism can be heterogeneous, with strongly calc-silicate altered carbonates transitioning to relatively pristine limestone over short distances. The main finding of this study was that the variability in calc-silicate alteration is largely dependent on the differing host lithologies …

Petrogenesis Of The Greenwater Range: Comparison To The Crater Flat Volcanic Field And Implications For Hazard Assessment, Ashley Kaye Tibbetts

UNLV Theses, Dissertations, Professional Papers, and Capstones

Pliocene basalts of the Greenwater Range, California erupted from 24 volcanic vents now represented by volcanic plugs, craters and scoria mounds. Basaltic magmas originated in the asthenospheric mantle, but show evidence of a lithospheric component. Depths and temperatures of melting calculated using a silica activity geobarometer are 54.3–89.6 km and 1367-1435oC, placing melting in the asthenosphere. The preferred petrogenetic model involves melting of lithospheric mantle thermally and mechanically, but not chemically, converted to asthenospheric mantle. Melting depths correspond to low velocity zones in the mantle as revealed in seismic profiles. Chemical and lithologic similarities between basalt in the Greenwater Range …

An Experimental Investigation Of Chemical Mass Transfer Processes In Crystallizing, Hydrous Silicate Magmas: The Genesis Of Ore Deposits And Metasomatic Fluids, Aaron S. Bell

UNLV Theses, Dissertations, Professional Papers, and Capstones

This dissertation is comprised of three broadly related experimental petrology projects on phase equilibria and noble metal solubility in hydrous silicate melts. Chapters two and three combine experimental petrology with high precision laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analysis of experimental run products in order to quantitatively constrain the behavior of the investigated metals. Chapter four presents experimental evidence detailing a novel oxidation mechanism for degassing silicate liquids as well as exploring the geochemical consequences of the proposed mechanism.

Chapter two presents the results of an experimental study on Au, Pt, and Pd behavior in coexisting silicate melt-sulfide-oxide …

Using Fluid Inclusions To Trace Formative Fluid Evolution At The Verde And Pancho Porphyry Au Deposits Of The Refugio District, Chile, Brian Joshua Aillaud

UNLV Theses, Dissertations, Professional Papers, and Capstones

Evolution of magmatically-derived formative fluids, and the processes that control the ratio of ore metals in porphyry and high-sulfidation epithermal deposits remain enigmatic. The Refugio district in the Maricunga Belt of Northern Chile hosts the temporally and spatially related Pancho and Verde porphyry gold deposits. Vein types at Pancho include A-veins, transitional veins, banded veins, D-veins and quartz-alunite ledges that formed by replacement. Verde East and West lack A-veins, and show an earliest vein type with transitional characteristics of A- to banded veins, banded veins and D-veins. Fluid inclusions and quartz textures were characterized by using optical microscopy and cathodoluminesence …

Phyllosilicate Mineralogy, 40ar/39ar Geochronology, And Genesis Of Petrocalcic Soils In The Southwest U.S.A., Colin R. Robins

UNLV Theses, Dissertations, Professional Papers, and Capstones

Obtaining isotope ages for arid soils and paleosols, including carbonate-cemented (calcic and petrocalcic) horizons, constitutes a significant challenge for soil scientists, geomorphologists, and stratigraphers. Carbonate-cemented soils foster diverse suites of authigenic minerals with exciting potential for geochronology, however, this potential has not been realized. This dissertation describes the timing of pedogenic palygorskite and sepiolite crystallization in extremely old, extant petrocalcic soils of the southwest U.S.A., and assumes that these fibrous, high-magnesium phyllosilicates contain sufficient lattice-bound K to warrant vacuum-encapsulated 40Ar/39Ar geochronology. This three-part study evaluated the (1) selective extraction, (2) 40Ar/39Ar analysis, and (3) pedogenesis of palygorskite and sepiolite.

Effects …