Paragenesis, fluid origin, and thermal history of a low-sulfidation epithermal gold-silver system

Samples of banded veins, microcrystalline quartz veins, and hydrothermal breccias +/- Au in the southern Castle Mountains, California were collected from four different zones within and up to 5 km outside the mine area in order to construct a paragenesis, interpret fluid origin, describe the thermal history, and examine fluid inclusion gas compositions as an exploration tool for low-sulfidation deposits. Two-thirds of the gold from the Lesley Ann deposit is associated with pyrite, found in zones of intense silicification, and precipitated due to sulfidation of rhyolitic host rock during the earliest stages of hydrothermal activity. The remaining gold occurs freely in breccia matrix quartz and was deposited after silicification as a result of cooling and boiling of 200 to 240°C fluids with 0 to 0.2 wt % NaCl equivalent. Late banded quartz and drusy quartz precipitated in all areas from 150 to 185°C waters with 0 to 1.1 eq wt % NaCl equivalent. Chalcedony bands adjacent to quartz in barren banded veins north of the mine area represent temperature drops likely resulting from abrupt changes in boiling zone levels, evidenced by platy calcite textures found in a few, but not all, quartz bands. (Abstract shortened by UMI.).

Name thesis:degree_name

Master of Science (MS)

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Geoscience

Grantor dc:publisher

University of Nevada, Las Vegas

Year

2000

Author dc:creator

• Rotert, Joel William

Contributors dc:contributor

• Jean S. Cline

Statement dc:rights

• IN COPYRIGHT. For more information about this rights statement, please visit http://rightsstatements.org/vocab/InC/1.0/

Language dc:language

English

Identifier

https://oasis.library.unlv.edu/rtds/1223

OAI identifier oai:identifier

oai:oasis.library.unlv.edu:rtds-2222