Physical Sciences and Mathematics Commons^™

Subalklaine Volcanism In The Eastern Basin And Range Province: Examples From The Miocene Mccullough Range Volcanic Field And The Pliocene To Holocene Black Rock Desert Volcanic Field, Racheal Leighann Johnsen

UNLV Theses, Dissertations, Professional Papers, and Capstones

This dissertation is composed of three papers that apply geologic mapping, whole rock geochemical and isotopic analysis, and mineral chemistry to describe two large, long-lived (~6 million years), and compositionally heterogeneous volcanic fields and posit sources of the rock types present in each. These fields are the McCullough Range in southern Nevada, which was a locus of volcanic activity from ~19 - 12 Ma and the Black Rock Desert volcanic field in west-central Utah, which began forming at ~6 Ma and is still active today, with the most recent eruption occurring ~720 years ago.

Chapter Two is composed of a …

Cretaceous And Eocene U-Pb Zircon Migmatite Ages From The East Humboldt Range Metamorphic Core Complex, Nevada, Jordan Drew

UNLV Theses, Dissertations, Professional Papers, and Capstones

Zircon separates from migmatite samples from the East Humboldt Range (EHR), northern Nevada were U-Pb dated using secondary ionization mass spectrometry. Cathodoluminescence images of zircons show bright anhedral cores with abundant euhedral overgrowths surrounding them.

The overgrowths give U-Pb dates indicating two periods of zircon growth. Inner rims have a Cretaceous age population at 70.6 ± 2.6 Ma. Outer rims give Eocene ages that either fall in to a single-age population at 45 ± 1.3 Ma or are part of a range from 41-31 Ma. Discordant zircon cores have upper intercepts between 1.8 -1.0 Ga.

Cretaceous and Eocene ages are …

Volcanic Evolution Of The Southern Quinn Canyon Range: Implications For Regional Correlation Of Volcanic Units, Christina Emery

UNLV Theses, Dissertations, Professional Papers, and Capstones

The southern Quinn Canyon Range lies in an area of the Great Basin subjected to large-volume Oligocene-Miocene silicic volcanism and smaller volume basaltic volcanism during the Pliocene. Three major ash-flow tuff units were correlated in the southern Quinn Canyon Range (the Pahranagat Tuff, Clifford Spring Tuff, and the Cow Canyon Tuff) with regional units by utilizing U/Pb and 40 Ar/ 39Ar geochronology, geochemical correlation, and field mapping. Isotopic analysis suggests that basalt in the southern Quinn Canyon Range is part of the Death Valley-Pancake Range Basalt Zone and is similar to Reveille Range Episode 1 and 2 basalts. Further comparison …

Petrogenesis Of The East Fork Member Rhyolites, Valles Caldera, New Mexico, Usa, Carla Eichler

UNLV Theses, Dissertations, Professional Papers, and Capstones

The most recent volcanism in the Valles caldera is represented by the El Cajete Pyroclastic Beds (ECPB), Battleship Rock Ignimbrite (BRI), and Banco Bonito Flow (BBF) as well as the VC-1 rhyolite, which are collectively known as the East Fork Member (EFM) of the Valles Rhyolite. The EFM was erupted at approximately 55 ka and 40 ka after an approximate 460 ka lull in volcanism. Previous studies suggested a mafic intrusion at depth triggered the eruptions. This thesis represents the first detailed study of the EFM.

Crystal assemblages consist of plagioclase, biotite, clinopyroxene, orthopyroxene, amphibole, sanidine, quartz, and oxides. Electron …

Petrogenesis Of The Linked River Mountains Volcanic Section And Wilson Ridge Pluton, Denise Kelly Honn

UNLV Theses, Dissertations, Professional Papers, and Capstones

The River Mountains (RM) volcanic suite and Wilson Ridge pluton (WRP), in the northern Colorado River extensional corridor of southern Nevada and northwestern Arizona, provide an ideal opportunity to investigate one of the most fundamental questions in igneous petrology: Do volcanic rocks erupt from subjacent plutons and do plutons vent to form volcanic fields? The RM volcanic suite (14.47± 0.26 to 12.66 ± 0.54 Ma; uncertainties are 2sigma) consists of a stack of andesite and rhyolite sills beneath a stratovolcano that primarily erupted dacite with lesser volumes of basalt and rhyolite. This volcanic suite is cored by a multiphase quartz …

Magma Chamber Processes At Mutnovsky Volcano, Russia, Kelly L. Robertson

UNLV Theses, Dissertations, Professional Papers, and Capstones

This dissertation is composed of two manuscripts about the evolution of Mutnovsky Volcano in Kamchatka, Russia. Mutnovsky has been active for the past approximately 80,000 years, during which there was the formation and subsequent eruption of four major stratocones. These four eruptive centers, named Mutnovsky I, II, III, and IV from oldest to youngest, have a range of erupted product compositions from basalt to dacite. The first major goal of this project was to investigate the melt source for Mutnovsky. Whole rock trace element and Nd, Sr, and Pb isotopic data were used to determine that the melt source was …

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 …

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 …

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 …

In Situ Element Quantification In The Hydrothermal Diamond Anvil Cell Using Synchrotron X-Ray Fluorescence With Applications Toward Subduction Zone Processes, Steven Joseph Maglio

UNLV Theses, Dissertations, Professional Papers, and Capstones

Yttrium is used in geochemical investigations of arc volcanics and metamorphic geothermometers. The ability to use Y as a geochemical tool is predicated on an understanding of the mobility of Y during fluid-saturated conditions attending metamorphic and igneous processes. The goal of this work was to use the hydrothermal diamond anvil cell (HDAC) and synchrotron radiation X-ray fluorescence to quantify, in situ, the concentration of Y in aqueous fluids at 2-5 GPa and 650 - 800 °C; conditions likely at the oceanic lithosphere - mantle wedge interface in subduction zones. Previous studies have used modified diamond anvils which limits their …

Geology Of The Southern Reveille Range, Nye County, Nevada, Matthew Alan Mckelvey

UNLV Theses, Dissertations, Professional Papers, and Capstones

The Reveille Range in central Nevada provides a unique window into the mid-Miocene geology and volcanology of the central Great Basin during the "ignimbrite flare up." Although faulted along its margins, the interior of the range is relatively undeformed thus preserving volcanic centers. The Reveille Range contains three mid-Miocene caldera complexes. Previous studies have identified the Goblin Knobs caldera (25.6 Ma) in the central Reveille Range and the caldera of northern Reveille Range (25.3 Ma) to the north. These calderas are completely filled with intracaldera tuffs. This study has identified a younger third caldera located in the southern part of …

Petrogenesis Of Pleistocene Basalts In The Norris-Mammoth Corridor, Yellowstone National Park, Kristeen Marie Bennett

UNLV Theses, Dissertations, Professional Papers, and Capstones

The basalts of the Norris-Mammoth corridor within the Yellowstone Plateau volcanic field have an outcrop erupted volume of ~94 km³. Basalt in the Yellowstone Plateau volcanic field is minor in volume compared to 3,700 km³ of felsic lavas, domes, and pyroclastic rocks. The tholeiitic eruptive products formed small Hawaiian-style shield volcanoes. A newly identified volcanic vent, called the Panther Creek vent, within the Swan Lake Flat basalt stratigraphic unit, was primarily Strombolian in its eruption style. This vent is the first recognized cinder cone in Yellowstone National Park.

All basaltic units within the Norris-Mammoth corridor, and the …

Geochemistry And Petrogenesis Of The Bonanza King Mafic Intrusive Complex, Trinity Terrane Ophiolite, California, Keith R. Willse

UNLV Theses, Dissertations, Professional Papers, and Capstones

The Bonanza King mafic intrusive complex (MIC) (>25 km^2₎ of the Trinity terrane ophiolite, northern California, consists of cogenetic plutonic and dike lithologies. Steep intrusive contacts exist between cumulate pyroxenite, isotropic gabbro, and peridotite country rock. Near vertical east-west trending, bimodal dikes intruded gabbro and are centered within the complex. Geochemical modeling indicates taht accumulation/fractionation of a gabbroic parental magma produced lithologic trends of cumulate pyroxenite and fractionated gabbro and dike lithologies. Similarities between all lithologies suggest cogenetic formation of all the elements of the Bonanza King MIC during the Late Silurian (431 +/- 3).

Parental magma …

The Geochronology And Geochemistry Of The Bearhead Rhyolite, Jemez Volcanic Field, New Mexico, Leigh Justet

UNLV Theses, Dissertations, Professional Papers, and Capstones

Around 82% of mapped Bearhead Rhyolite (Main Cluster) and Peralta Tuff appears to have been derived from a relatively long-lived (~680 ka), large, shallow (Earth's surface) magma chamber that did not produce a caldera-forming eruption. Although volatile contents were great enough (~ wt.% H₂O), no large-scale explosive eruptions occurred because magma may have been tectonically vented. The lack of systematic chemical variation within the Main Cluster with time during this ~680 ka interval may imply that erupted magmas were physically separated from each other by fault-formed cupolas in the roof of the magma chamber. These results are significant …

Volcanology And Geochemistry Of Pliocene And Quaternary Basalts On Citadel Mountain, Lunar Crater Volcanic Field, Pancake Range, Nevada, Loretta D. Dickson

UNLV Theses, Dissertations, Professional Papers, and Capstones

Alkali basalts on Citadel Mountain form the southern margin of the Lunar Crater Volcanic Field (LCVF) in the central Great Basin, Nevada. Citadel Mountain comprised of a faulted, north tilted section of Tertiary andesite and ash-flow tuff is capped by Pliocene and Quaternary alkali basalt flows that erupted from six major cinder cones. The basalt flows on Citadel Mountain can be divided into two groups (older and younger) based on age and isotopic signatures. The older basalt group is characterized by higher ⁸⁷ Sr/⁸⁶Sr and lower E_Nd and the younger group has lower ⁸⁷Sr/⁸⁶Sr …

The Geology And Structures In The Northern Hiko Range, Lincoln County, Nevada, Douglas D. Switzer

UNLV Theses, Dissertations, Professional Papers, and Capstones

In the northern Hiko Range, extension occurred in four temporally distinct episodes during the Cenozoic. The extensional events are (1) prevolcanic (> 27.31 ± 0. 03 Ma), (2) syn-volcanic (between 22.78 ± 0,03 and 18.5 ± 0.4 Ma), (3) Tertiary(?) post-volcanic ( < 14.7 ± 0.4 Ma), and ( 4) Pliocene(?) - Quaternary. Four fault sets are delineated based on orientation and cross-cutting relationships: (I) northeast- to northwest-striking moderately dipping prevolcanic faults, (2) east-west striking, steeply-dipping syn-volcanic faults, (3) east-west- and east-northeast-striking, steeply dipping Tertiary(?) post-volcanic faults, and (4) generally north-striking steeply dipping Pliocene (?) - Quaternary faults.

Prevolcanic faults in the northern Hiko Range are interpreted to be footwall faults to an Oligocene age extensional system. These faults increase the area affected by Oligocene extension and support existing evidence that suggests this event is widespread.

A tectonomagmatic rift model has been proposed to explain synvolcanic extension during the Tertiary in the northern Basin and Range …

The Petrogenesis Of Andesites Produced During Regional Extension: Examples From The Northern Mccullough Range, Nv And Xitle Volcano, Mexico, Kelly Ann Boland

UNLV Theses, Dissertations, Professional Papers, and Capstones

Andesite dominated volcanic systems produced during regional crustal extension remain a relatively unexplored aspect of andesite petrogenesis. In the southern Basin and Range province, thick sections of andesite and basaltic andesite have been documented in areas including the Piute Range, California, the Eldorado Range, Nevada, and the McCullough Range, Nevada. The northern McCullough Range, located 20 miles south-southeast of Las Vegas, is an ideal place to study the petrogenesis of an andesite dominated system. This area contains a mid-Miocene stratocone composed mainly of a 1200 m thick section of andesite flows that formed synchronous with regional extension.

The northern McCullough …

Mafic Volcanism In The Colorado Plateau: Basin And Range Transition Zone, Hurricane, Utah, Alexander Sanchez

UNLV Theses, Dissertations, Professional Papers, and Capstones

The Hurricane volcanic field (HVF) is a small-volume (0.48 km³) mafic volcanic field in the Colorado Plateau/Basin & Range Transition Zone located in the eastern part of the St. George basin in southwestern Utah. Strombolian-Hawaiian style eruptions produced thin (10 m) a'a lava flows and cinder (scoria) cones composed of vesicular basalt, bombs and agglutinate. Radiometric dating and geologic relationships demonstrate that the HVF formed over a period of at least 100,000 years. In the upper crust, magma probably rose along joints in sedimentary rocks because chains of volcanic vents follow joint orientation maxima in sedimentary rocks.

Three …

Geology And Geochemistry Of Tertiary Volcanic Rocks In The Northern Reveille And Southern Pancake Ranges, Nye County, Nevada, Kelly Brian Rash

UNLV Theses, Dissertations, Professional Papers, and Capstones

The northern Reveille and southern Pancake Ranges, located in the south-central Great Basin, experienced a prolonged history of Tertiary volcanism. Volcanic activity in this area began with the eruption of large-volumes of ash-flow tuffs from calderas of the central Nevada caldera complex. The Reveille Range and the southernmost portion of the Pancake Range are the site of two calderas that are the sources for the tuff of Goblin Knobs and tuff of northern Reveille Range. The tuff of Goblin Knobs (70.4-75.3 wt.% SiO₂) erupted from the caldera of Goblin Knobs (25.6 Ma) and is the thickest (~1700 m) …

Geochemical Evolution Of A Mid-Miocene Synextensional Volcanic Complex: The Dolan Springs Volcanic Field, Northwestern Arizona, Scott Michael Mcdaniel

UNLV Theses, Dissertations, Professional Papers, and Capstones

The Dolan Springs volcanic field (DSV), of northwestern Arizona, is dominated by andesite and basaltic-andesite flows and breccias, with minor amounts of basalt, rhyolite, and ash-flow tuff. Geochemistry is used here as a tool to evaluate the roles and contributions of the lithospheric and asthenospheric mantles to magmatism related to Miocene extension in the Colorado River extension corridor (CREC). The majority of synextensional volcanic rocks in the DSV are geochemically similar to regional trends, but rare tholeiitic basalts erupted near the end of extension. The tholeiites have trace element signatures similar to ocean island basalt (OIB), but have isotopic values …

The Geology Of The Tuff Of Bridge Spring: Southern Nevada And Northwestern Arizona, Shirley Ann Morikawa

UNLV Theses, Dissertations, Professional Papers, and Capstones

The Tuff of Bridge Spring (TBS) is a regionally-widespread, andesite to rhyolite (59.50 to 74.91 wt. %) ash-flow tuff of mid-Miocene age (ca. 15.2 Ma) that is exposed in the northern Colorado River extensional corridor of southern Nevada and northwestern Arizona. Determination of the areal distribution, geochronology, lithology, geochemistry, and internal stratigraphy of the TBS is important for its establishment as a reliable stratigraphic reference horizon for tectonic reconstructions of the extensional corridor during the middle Miocene. Based on reoccurring patterns of major and trace element variation, the TBS is divided into constant Cr/variable SiO₂ and variable Cr/variable SiO …

The Sloan Sag: A Mid-Miocene Volcanotectonic Depression, North-Central Mccullough Mountains, Southern Nevada, Hayden L. Bridwell

UNLV Theses, Dissertations, Professional Papers, and Capstones

In the Hidden Valley area of the north-central McCullough Mountains, southern Nevada, mid-Miocene andesite and dacite domes, flows and pyroclastic units (the Sloan volcanics) partially fill a sag in the underlying Hidden Valley volcanics. The 13.5 km diameter sag formed during and/or after the eruption of the Sloan volcanics. Sagging was accommodated by a combination of movement on the McCullough Wash fault system, and subsidence into evacuated chambers.

Major, trace and rare-earth element geochemistry suggests that the rocks of the Sloan volcanics belong to four groups, each of which were produced by partial melting of chemically distinct sources. With the …