Award Date

1-1-2000

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Geoscience

First Committee Member

Rodney V. Metcalf

Number of Pages

136

Abstract

The Early Devonian (404 +/- 3 Ma) Porcupine Lake mafic intrusive complex of the Trinity terrane consists primarily of ultramafic-mafic plutonic and dike lithologies. The plutonic rock forms steep intrusive contacts with adjacent Ordovician peridotite, and consists of basal layered peridotite, cumulate clinopyroxenite, and isotropic gabbro. East-west trending mafic-to-felsic aphanitic dikes intrude the plutonic rocks, with high dike concentrations (>80%) in the southern portion of the complex; Gabbro and mafic dikes display subduction-related enrichment of light-ion lithophile elements and high degrees of depletion of high-field strength elements (Nb, Ta ≅ 0.1 NMORB). Trace element mixing models indicate gabbro and mafic dikes are derived from a residual mantle source with enrichment by small amounts of slab-derived aqueous fluids and pelagic sediments. Mafic dikes are also enriched by fertile MORB (asthenospheric) mantle. Subduction zone enrichment of a depleted mantle source suggests the Porcupine Lake mafic intrusive complex formed in a forearc tectonic setting.

Keywords

California; Complex; Intrusive; Lake; Mafic; Northern; Petrogenetic; Porcupine; Study; Terrane; Trinity

Controlled Subject

Geology; Geochemistry

File Format

pdf

File Size

4874.24 KB

Degree Grantor

University of Nevada, Las Vegas

Language

English

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