Award Date

5-1999

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Geoscience

Advisor 1

Rodney Metcalf, Chair

First Committee Member

Jean Cline

Second Committee Member

Eugene I. Smith

Graduate Faculty Representative

Brett Riddle

Number of Pages

144

Abstract

Open-space brucite was identified in veins crosscutting hydrothermally altered limestone near the Devil Peak rhyolite plug in southern Nevada. The brucite occurs with serpentine, calcite, chalcedony, hydromagnesite, dolomite, and clinochlore.

Brucite usually forms as a replacement mineral, but textural evidence indicates that the brucite at Devil Peak precipitated in open space. The presence of chalcedony in veins indicates the temperature of the hydrothermal fluid was <180oC during and after mineral deposition. Thermodynamic modeling shows this temperature is too low for replacement brucite to form, thus the low temperature of alteration may be a factor in this unusual occurrence of brucite.

Infiltration modeling of isotopically depleted wall rocks shows that the hydrothermal fluid was initially composed of a mixture of metamorphic and meteoric water, with XCO2 = 0.15-0.16. Later, an influx of magmatic fluid or metamorphic water mixed with the early fluid. Fluid inclusion analysis shows XCO2 < 0.01 for the fluid mixture.

Keywords

Brucite; Geology; Hydrothermal deposits; Limestone; Nevada -- Devil Peak

Disciplines

Geochemistry | Geology

Language

English

Comments

Signatures have been redacted for privacy and security measures.


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