Award Date

8-1-2012

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Geoscience

First Committee Member

Eugene I. Smith

Second Committee Member

Terry Spell

Third Committee Member

Adam Simon

Fourth Committee Member

Stephen Lepp

Fifth Committee Member

Pamela Burnley

Number of Pages

311

Abstract

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 monzonite stock. The WRP (15.18 ± 0.31 to 12.66 ± 0.54 Ma) consists of an early hypabyssal suite, monzodiorite and diorite intrusions, main phase quartz monzonite of the Teakettle Pass suite, and bimodal late stage dikes. Previous mapping linked the now faulted and detached (by 20 km) volcanic and plutonic suites. The current study establishes a more explicit link between the RM volcanic suite and WRP by using new 206Pb/238U zircon ages and a more complete geochemical data set. The major conclusions of this new work are that: 1) the WRP and the RM represent a single cogenetic igneous system and; 2) that multiple types of data (lithologic, geochronologic, and geochemical) must be used to identify cogenetic volcanic and plutonic suites. An important implication of this work is that other volcanic fields and plutons closely related in age and chemistry may represent single systems with shared magmatic histories.

Keywords

Arizona; Igneous petrology; Igneous rocks; Intrusions (Geology); Nevada – Wilson Ridge; North America – River Mountains; Petrology; Volcanic ash, tuff, etc.; Volcanology

Disciplines

Geology | Volcanology

Language

English


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