Publication Date
Spring 2026
Degree Type
Thesis
Degree Name
Master of Science (MS)
Department
Geology
Advisor
Jonathan Miller; Ellen Metzger; Ryan Portner
Abstract
The Searchlight pluton and proximal age-correlative Miocene volcanic rocks offer a rare glimpse into the growth and evolution of an intermediate-to-silicic magmatic system and allow investigation of the possible links between plutonic and volcanic units that are rarely preserved in the geological record. These linkages have long been the subject of debate; this thesis investigates the connections in detail. Methods employed include field mapping, petrography, major- and trace-element geochemistry, Sr- and Nd-isotope geochemistry, crystal-size distribution analysis, multivariate statistical analysis of trace-element geochemical data, and U-Pb zircon geochronology. These data are used to reconstruct and link portions of the surface volcanic and shallow-crustal intrusive record that comprise the Searchlight magmatic system. The Miocene pluton formed incrementally by periodic magmatic pulses over approximately 1 million years. From approximately 17.5-16.3 Ma, the Searchlight system produced geochemically monotonous intermediate magma, as trachyandesite and trachydacite lavas and domes, hypabyssal trachydacite porphyry near the roof of the pluton, and quartz monzonite crystallized within the upper crust. Around 16.3 Ma, there was a sharp change to silicic magma, which produced a granite magma body that fractionated to high-silica rhyolite. This high-silica rhyolite erupted as lavas and tuffs; compositionally equivalent high-silica intrusives are preserved as dikes, and leucogranite sills and pods.
Recommended Citation
Dodge, Michele C., "Volcanic–Plutonic Links Within the Miocene Searchlight Magmatic System, Southern Nevada, U.S.A." (2026). Master's Theses. 5785.
DOI: https://doi.org/10.31979/etd.835f-kdnj
https://scholarworks.sjsu.edu/etd_theses/5785
