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

104

Abstract

The Wilson Ridge pluton contains a rare occurrence of hydrothermal sodic amphibole. hydrothermal amphibole occurs as fracture coatings, veinlets, dense stockwork-type networks, and diffusive alteration fronts. Electron microprobe analyses of the hydrothermal amphibole reveal a range of Na-rich compositions, most notably magnesio-riebeckite. Magnesio-riebeckite in the Wilson Ridge pluton formed by Na-metasomatism related to subsolidus hydrothermal alteration involving Na-rich fluids of meteoric origin. Whole-rock geochemistry of samples from zones of hydrothermal amphibole show enrichment of Na2O (>9.6 wt. %) and depletion of K2O (0.15 wt. %) and CaO (2.4 wt. %) relative to unaltered host rock. Secondary fluid inclusions associated with zones of hydrothermal amphibole contain daughter crystals of halite and up to three other unknown crystals. Oxygen isotope studies suggest that granitoid rocks containing hydrothermal amphiboles have lower delta18O values (+3.68‰ to +6.97‰) than unaltered granitoid rocks (delta 18O values +6.04‰ to +9.23‰).

Keywords

Metasomatism; Mineralization; Pluton; Ridge; Riebeckite; Sodium; Wilson

Controlled Subject

Geology; Geochemistry; Mineralogy

File Format

pdf

File Size

2826.24 KB

Degree Grantor

University of Nevada, Las Vegas

Language

English

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