Volcanology Commons^™

Geochemistry Of The Lazufre Volcanic Complex: Determining The Geometries And Processes Of The Magmatic Sources In The Central Andean Volcanic Zone, Brooke Erin Benz

MSU Graduate Theses

The Central Andes in South America contain many active volcanoes and volcano complexes due to constant subduction producing extrusive rocks varying in composition. The Lazufre Complex, Chile-Argentina border, consists of two Pleistocene volcanic centers, Lastarria and Cordon del Azufre andesite and dacite lava flows and domes. Whole-rock K-Ar dates of lavas from Cordon del Azufre place the most recent eruptions at 0.6-0.3 Ma ±0.3 Ma. Major-element data of plagioclase and pyroxene show homogeneous compositions between the centers, which is consistent with whole rock major- and trace-element compositions. The primary composition of the pyroxenes are augite and diopsides for cpx and …

Petrology And Geochemistry Of The Bearwallow Mountain Andesite, Mogollon-Datil Volcanic Field, New Mexico, Conor Lee O'Dowd

MSU Graduate Theses

The Mogollon-Datil volcanic field (MDVF), located in southern New Mexico, is the result of episodic volcanism and the transition between arc and rift magmatism. The MDVF has been the focus of several mapping, stratigraphic, petrologic, geochronological, and geochemical studies to understand the complete volcanic and tectonic history. However, the majority of previous studies lack geochemical analyses on intermediate composition volcanic rocks, giving more attention to the large-volume ignimbrites and rhyolite flows as well as the minor basalt flows that occurred between 36 and 20 Ma. I present new whole-rock major- and trace-element analyses and petrographic textures on one of the …

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 …

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) …