Geology and hydrothermal alteration of the Palmetto property, Esmeralda County, Nevada

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Authors

Wolverson, Nancy Jean

Issue Date

1987

Type

Thesis

Language

en_US

Keywords

Hydrothermally Altered Andesite Lava , Hydrothermally Altered Dactite Lava , Precious Metals , Paleozoic Sedimentary Rocks , Palmetto Property , Volcanic Rocks , Alteration Envelopes , E-w-trending Silica+alunite Ribs , Argillically Altered Rocks , Propylitized Rocks , Quartz+alunite , Cristobalite+alunite , Sulfur Isotopic Determinations , Coarsegrained Alunite , Pyrite , Hypogene , Supergene , Gold , Zone Of Oxidation , Hydrothermal Breccias , Adularia , Sulfate Minerals , Ore , Mackay Theses and Dissertations Grant Collection

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Abstract

Hydrothermally altered andesite/dacite lavas containing detectable precious metals and largely unaltered Paleozoic sedimentary rocks are exposed at the Palmetto property. Within the volcanic rocks alteration envelopes are centered on prominent E-W-trending silica+alunite ribs in sharp contact with argillically altered rocks that grade outward into propylitized rocks. The ribs vary from quartz+alunite in the north to cristobalite+alunite in the south. Sulfur isotopic determinations suggest coarsegrained alunite (£34S = 23.5 per mil) and pyrite (^34S = 3.7 per mil) are hypogene, whereas fine-grained alunite (£34S=0.7 per mil) is supergene. The hypogene alunite has a K-Ar age of 16.1+0.7 m.y. Gold increases below the zone of oxidation with the appearance of approximately 1% pyrite. Based on the presence of hydrothermal breccias and adularia and the abundance of sulfate minerals, boiling probably occurred. The lack of repeated boiling episodes may explain the absence of ore.

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University of Nevada, Reno

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In Copyright(All Rights Reserved)

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