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Publication Date

Summer 2014

Degree Type

Thesis - Campus Access Only

Degree Name

Master of Science (MS)

Department

Geology

Advisor

Jonathan Miller

Keywords

Geochemistry, geochronology, Ti-in-zircon, trace element, volcanics, Zircon

Subject Areas

Geology

Abstract

The middle Miocene Searchlight pluton (~17-15.8 Ma) in southern

Nevada, USA, located in the Colorado River Extensional Corridor, has an

extensive spatially and temporally associated volcanic record. Regional

extension has rotated a large crustal block ca. 90° to expose a 12-13 km section

of crust that included parts of the Searchlight pluton and its volcanic cover in the

adjacent Highland Range. Recent geochronology and geochemistry of the

pluton and volcanic strata have shown that the construction of the Searchlight

magma system was piecemeal. We examined the growth and dynamics of the

Searchlight magma system using zircon trace elements from U/Pb age-dated

plutonic and volcanic rocks. Zircon trace element indices for magmatic

temperature and evolution, including Ti, Hf, Th, U, Th/U, Yb/Gd, and Eu/Eu*,

showed a strong correlation to rock type and age. The Searchlight magmatic

system has recorded a complex solidification history, a progression from a

trachyandesitic to rhyolitic composition with time, and clear cogenetic links

between some of the plutonic and volcanic rocks.

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