Physical Sciences and Mathematics Commons^™

Petrogenesis Of Enriched And Intermediate Poikilitic Shergottites: From Magmatic Source To Emplacement, Rachel Rahib

UNLV Theses, Dissertations, Professional Papers, and Capstones

Poikilitic shergottites, making up >20% of martian meteorites, likely represent a significant composition of the martian crust, as intrusive gabbroic rocks. To further constrain petrogenetic relationships amongst enriched and intermediate poikilitic shergottites, we utilize bulk rock trace element compositions, mineral major element compositions, phosphorus maps of olivine grains, oxygen fugacity (ƒO2) values, subsolidus equilibration temperatures, and quantitative textural analyses, of the most comprehensive suite of poikilitic shergottites yet (11 samples), including three newly recovered samples (Northwest Africa [NWA] 11065, NWA 11043, NWA 10961). Although petrographically light rare earth element (LREE) enriched and intermediate poikilitic shergottites are similar, distinct LREE abundances …

Prokaryotic Diversity And Aqueous Geochemistry Of Subsurface Environments Of The Death Valley Regional Flow System, Joshua David Sackett

UNLV Theses, Dissertations, Professional Papers, and Capstones

This dissertation summarizes over four years of effort towards the completion of a Ph.D. in Biological Sciences. The work presented in this document covers a broad range of topics, but a central unifying theme is prokaryotic life in the continental subsurface. The work presented in each chapter relied heavily on cultivation-independent methods for assessing prokaryotic communities, including prokaryotic community structure reconstruction from high-throughput sequencing of 16S rRNA gene libraries and single-cell genome analysis of novel uncultivated bacteria.

Chapter 2 examines the aqueous geochemistry and prokaryotic diversity of Devils Hole, a cavernous limnocrene and sole natural habitat for the critically endangered …

The Sisal Database: A Global Resource To Document Oxygen And Carbon Isotope Records From Speleothems, Kamolphat Atsawawaranunt, Laia Comas-Bru, Sahar Amirnezhad Mozhdehi, Michael Deininger, Sandy P. Harrison, Andy Baker, Meighan Boyd, Nikita Kaushal, Syed Masood Ahmad, Yassine Ait Brahim, Monica Arienzo, Petra Bajo, Kerstin Braun, Yuval Burstyn, Sakonvan Chawchai, Wuhui Duan, István Gábor Hatvani, Jun Hu, Zoltán Kern, Inga Labuhn, Matthew Lachniet, Franziska A. Lechleitner, Andrew Lorrey, Carlos Pérez-Mejías, Robyn Pickering, Nick Scroxton, Sisal Working Group Members

Geoscience Faculty Publications

Stable isotope records from speleothems provide information on past climate changes, most particularly information that can be used to reconstruct past changes in precipitation and atmospheric circulation. These records are increasingly being used to provide out-of-sample evaluations of isotope-enabled climate models. SISAL (Speleothem Isotope Synthesis and Analysis) is an international working group of the Past Global Changes (PAGES) project. The working group aims to provide a comprehensive compilation of speleothem isotope records for climate reconstruction and model evaluation. The SISAL database contains data for individual speleothems, grouped by cave system. Stable isotopes of oxygen and carbon (δ18O, δ13C) measurements are …

Mitigating Accumulation Of Aeolian Dust Particles On Solar Power Generator Panels Without Water, Sanjana Das

UNLV Theses, Dissertations, Professional Papers, and Capstones

Accumulation of dust on solar panels poses a serious problem as it can significantly reduce light absorption and electrical energy output. Several factors affect the dust accumulation such as location, dust properties, wind velocity, system orientation, ambient temperature, humidity, and panel surface properties. Experimental and theoretical studies show that short circuit current and maximum power output of photovoltaic panels reduce approximately linearly with dust concentration. Incidentally, the locations with higher solar energy concentrations are also arid or semi-arid regions with higher dust concentrations. In order to avoid loss in power output, most PV installations perform periodic panel cleaning with water. …

Formation Of Evolved Rocks At Gale Crater By Crystal Fractionation And Implications For Mars Crustal Composition, Arya Udry, Esteban Gazel, Harry Y. Mcsween Jr.

Geoscience Faculty Publications

The recent discovery of some ancient evolved rocks in Gale crater by the Curiosity rover has prompted the hypothesis that continental crust formed in early Martian history. Here we present petrological modeling that attempts to explain this lithological diversity by magma fractionation. Using the thermodynamical software MELTS, we model fractional crystallization of different Martian starting compositions that might generate felsic igneous compositions like those analyzed at Gale crater using different variables, such as pressure, oxygen fugacities, and water content. We show that similar chemical and mineralogical compositions observed in Gale crater felsic rocks can readily be obtained through different degrees …

Introduction To A Resources Special Issue On Criticality Of The Rare Earth Elements: Current And Future Sources And Recycling, Simon M. Jowitt

Geoscience Faculty Publications

The rare earth elements (REE) are vital to modern technologies and society and are amongst the most important of the critical elements. This special issue of Resources examines a number of facets of these critical elements, current and future sources of the REE, the mineralogy of the REE, and the economics of the REE sector. These papers not only provide insights into a wide variety of aspects of the REE, but also highlight the number of different areas of research that need to be undertaken to ensure sustainable and secure supplies of these critical metals into the future.

Provenance And Paleogeography Of The 25-17 Ma Rainbow Gardens Formation: Evidence For Tectonic Activity At Ca. 19 Ma And Internal Drainage Rather Than Throughgoing Paleorivers On The Southwestern Colorado Plateau, Melissa A. Lamb, L. Sue Beard, Malia Dragos, Andrew D. Hanson, Thomas A. Hickson, Mark Sitton, Paul J. Umhoefer, Karl E. Karlstrom, Nelia Dunbar, William Mcintosh

Geoscience Faculty Publications

The paleogeographic evolution of the Lake Mead region of southern Nevada and northwest Arizona is crucial to understanding the geologic history of the U.S. Southwest, including the evolution of the Colorado Plateau and formation of the Grand Canyon. The ca. 25–17 Ma Rainbow Gardens Formation in the Lake Mead region, the informally named, roughly coeval Jean Conglomerate, and the ca. 24–19 Ma Buck and Doe Conglomerate southeast of Lake Mead hold the only stratigraphic evidence for the Cenozoic pre-extensional geology and paleogeography of this area. Building on prior work, we present new sedimentologic and stratigraphic data, including sandstone provenance and …

Petrology And Geochemistry Of The Enriched Poikilitic Shergottite Northwest Africa 10169: Insight Into The Martian Interior, Logan Matthew Combs

UNLV Theses, Dissertations, Professional Papers, and Capstones

The martian meteorite Northwest Africa (NWA) 10169 is classified as a new member of the geochemically enriched poikilitic shergottites, based on mineral composition, Lu-Hf isotope systematics, and rare earth element (REE) composition. Akin to other poikilitic shergottites, it shows a similar bimodal texture to other enriched and intermediate poikilitic shergottites. In addition, olivine and pyroxene in the poikilitic zone have higher Mg#’s (Mg/Mg+Fe) than those in the interstitial areas, suggesting that the poikilitic texture represents early-stage crystallization, opposed to late-stage non-poikilitic crystallization. Calculated fO2 values are reduced (FMQ -2.3 ± 0.23) within the poikilitic texture, and more oxidized (FMQ -1.07 …

Holocene Climate Evolution Of Continental Western Eurasia Constrained By Stable-Isotope And Cation Geochemistry Of U-Th-Dated Speleothems And Meteogenic Travertine, Jonathan Lloyd Baker

UNLV Theses, Dissertations, Professional Papers, and Capstones

Reliable reconstructions of global and regional climate during the Holocene (11,700 years ago to present) are vital to constraining the natural range of climate variability and testing state-of-the-art models, which seek to forecast the near- and long-term impact of anthropogenic greenhouse forcing. Much of continental Eurasia is still underrepresented, however, in geological proxy reconstructions of Holocene climate variability, and the vast majority of paleoclimate data only reflect conditions during peak summer months (JJA) or the growing season. The paucity of winter proxy data has therefore been cited as a possible explanation for the current mismatch between geological proxy-based and climate-model …

Structural Evolution And Regional Implications Of The Arrowhead Mine Fault Within The Pahranagat Shear Zone, Nevada, Usa, Michael Dennis Evans

UNLV Theses, Dissertations, Professional Papers, and Capstones

The Basin and Range province is characterized by normal faults associated with

extension, but the occurrence of strike-slip faults and the seismic hazard accompanying

them is less understood. One major strike-slip zone, the Pahranagat shear zone (PSZ),

lies in Lincoln County, Nevada and within the boundary zone between northern Basin

and Range (NBR) and central Basin and Range (CBR) sub-provinces. The PSZ is a 20-

25 km long zone of Cenozoic left-lateral faults. The Arrowhead Mine Fault (AMF) is one

of the three major faults in the PSZ. The western AMF and the faults that surround and

abut it are …

Miocene-Quaternary Deformation Along The Central Maynard Lake Fault, Pahranagat Shear Zone, Nevada, Alexander Peck

UNLV Theses, Dissertations, Professional Papers, and Capstones

The left-lateral Pahranagat shear zone (PSZ) and Caliente-Enterprise zone (CEZ) exist at the boundary between two sub-provinces, the Northern (NBR) and Central Basin and Range (CBR). The PSZ contains three major ENE striking sinistral faults, including the Maynard Lake fault (MLF), which is the longest fault and marks the southern boundary of the zone. The PSZ has been suggested to be a transfer zone, but little is known about the structures along these major faults that are involved in strain transfer. These left-lateral systems exist within the Central Nevada seismic belt which has experienced significant earthquakes in recent history. Possible …

A Novel Approach To Analyzing Strain Heterogeneity In Polycrystalline Quartz Specimens Deformed At High Pressure And Temperature, Nolan Ambrose Regis

UNLV Theses, Dissertations, Professional Papers, and Capstones

Rheological studies of rocks and minerals allow researchers to study the grain-scale deformation mechanisms that govern large-scale geologic processes from mountain building to mantle mixing. Deforming rock samples with high pressure and temperature apparatuses similar to the Griggs piston cylinder apparatus allows us to simulate deformation at depth. However, many apparatuses are limited to “cook-and-look” analysis and require modeling techniques to determine the evolution of deformation patterns found in experimental samples. A previous study used two-dimensional finite element models to analyze the development of stress and strain patterns in polycrystalline rocks. The study suggested rhythmic patterns in deformed rocks develop …

Craters Of The Moon National Monument Basalts As Unshocked Compositional And Weathering Analogs For Martian Rocks And Meteorites, Christopher T. Adcock, Arya Udry, Elisabeth M. Hausrath, Oliver Tschauner

Geoscience Faculty Publications

The availability of terrestrial sites that are martian analogs allows researchers to investigate Mars using knowledge gained on Earth. Among the terrestrial analog sites for Mars is Craters of the Moon National Monument (COTM) in Idaho, U.S.A. Craters of the Moon National Monument is home to over 60 basalt lava flows, many of which have been dated from 2050 to 18 340 years before present (y.b.p.). Following previous authors, we examined the chemistry and petrogenesis of COTM basalts compared to basaltic martian rocks, martian meteorites, and meteorite clasts, and then examined the results of chemical weathering of the basaltic flows. …

Humans Thrived In South Africa Through The Toba Eruption About 74,000 Years Ago, Eugene I. Smith, Zenobia Jacobs, Racheal Johnsen, Minghua Ren, Erich C. Fisher, Simen Oestmo, Jayne Wilkins, Jacob A. Harris, Panagiotis Karkanas, Shelby Fitch, Amber Ciravolo, Deborah Keenan, Naomi Cleghorn, Christine S. Lane, Thalassa Matthews, Curtis W. Marean

Geoscience Faculty Publications

Approximately 74 thousand years ago (ka), the Toba caldera erupted in Sumatra. Since the magnitude of this eruption was first established, its effects on climate, environment and humans have been debated1. Here we describe the discovery of microscopic glass shards characteristic of the Youngest Toba Tuff—ashfall from the Toba eruption—in two archaeological sites on the south coast of South Africa, a region in which there is evidence for early human behavioural complexity. An independently derived dating model supports a date of approximately 74 ka for the sediments containing the Youngest Toba Tuff glass shards. By defining the input of shards …

Elastic Geothermobarometry: Corrections For The Geometry Of The Host-Inclusion System, M. L. Mazzucchelli, Pamela Burnley, R. J. Angel, S. Morganti, M. C. Domeneghetti, F. Nestola, M. Alvaro

Geoscience Faculty Publications

Elastic geothermobarometry on inclusions is a method to determine pressure-temperature conditions of mineral growth independent of chemical equilibrium. Because of the difference in their elastic properties, an inclusion completely entrapped inside a host mineral will develop a residual stress upon exhumation, from which one can back-calculate the entrapment pressure. Current elastic geobarometric models assume that both host and inclusion are elastically isotropic and have an ideal geometry (the inclusion is spherical and isolated at the center of an infinite host). These conditions do not commonly occur in natural rocks, and the consequences for inclusion pressures can only be quantified with …

Nevada Desert Dust With Heavy Metals Suppresses Igm Antibody Production, Deborah E. Keil, Brenda J. Buck, Dirk Goossens, Brett Mclaurin, Lacey Murphy, Mallory Leetham-Spencer, Yuanxin Teng, James E. Pollard, Russell Gerads, Jamie C. Dewitt

Geoscience Faculty Publications

Systemic health effects from exposure to a complex natural dust containing heavy metals from the Nellis Dunes Recreation Area (NDRA) near Las Vegas, NV, were evaluated. Several toxicological parameters were examined following lung exposure to emissive dust from three geologic sediment types heavily used for recreational off-road activities: yellow sand very rich in arsenic (termed CBN 5); a shallow cover of loose dune sand overlying a gravelly subsoil bordering dune fields (termed CBN 6); and brown claystone and siltstone (termed CBN 7). Adult female B6C3F1 mice were exposed by oropharyngeal administration to these three types of geogenic dusts at 0.01–100 …