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Duration of Hydrothermal Activity at Steamboat Springs, Nevada, From Ages of Spatially Associated Volcanic Rocks

Description: Abstract: Steamboat Springs is a presently active equivalent of epithermal gold-silver ore-forming systems. Hot-spring sinter deposits contain small amounts of gold, silver, mercury, antimony, and arsenic. Hot-spring activity probably started before extrusion of the basaltic andesite of Steamboat Springs. Old sinter from the Steamboat Springs system occurs in gravels above and below the basaltic andesite. Intense hydrothermal alteration, including almost complete replacement by hydrothermal potassium-feldspar, has affected the basaltic andesite. Three plagioclase separates of differing potassium content from fresh basaltic andesite yielded potassium-argon ages of 2.52 to 2.55 m.y. Basaltic andesite almost completely replaced by potassium-feldspar yielded an age of 1.1 m.y. The source of energy for the thermal convection system is probably a large rhyolitic magma chamber that supplied the pumice and from which the rhyolite domes were emplaced. Sanidine and obsidian from four of the rhyolite domes yielded potassium-argon ages of 1.15 to 1.52 m.y. and obsidian from one of the northeastern domes yielded apparent ages of 2.97 and 3.03 m.y. The data indicate that hydrothermal activity has occurred at Steamboat Springs, possibly intermittently, for more than 2-1/2 m.y. These data agree with other radiogenic age studies indicating 1- and 2-m.y. lifetimes for the hydrothermal systems that generate epithermal gold-silver deposits.
Date: 1979
Creator: Silberman, M. L.; White, D. E.; Keith, T. E. C. & Dockter, R. D.
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Partner: UNT Libraries Government Documents Department

Nomenclature of Precambrian Rocks in Colorado

Description: Abstract: "The Precambrian rocks of Colorado consist of a metaphoric complex more than 1,700 million years in age, three groups of igneous rocks about 1,700, 1,400, and 1,000 million years in age, here designated informal age groups, and two areally restricted units of sedimentary rocks, one between 1,400 and 1,700 million years in age and one between 950 and 1,400 million years. A systematic nomenclature for many of the rocks does not exist, but the present state of knowledge will permit establishment of a comprehensive nomenclature. Numerous formal names that have been applied to elements of the Precambrian assemblage are appraised and classified in a table, and eight names are abandoned."
Date: 1977
Creator: Tweto, Ogden
Partner: UNT Libraries Government Documents Department

Problems with Applying Topographically Driven Flow to Genesis of the Upper Mississippi Valley Zinc-Lead District and to Fluid Flow in the Illinois Basin

Description: A report about how topographically driven ground-water flow and other processes that involve dewatering of basins fail to account for the temperatures indicated by fluid inclusion and sulfur isotope studies in the Upper Mississippi Valley zinc-lead district on the northern edge of the Illinois Basin.
Date: 1995
Creator: Spirakis, Charles S.
Partner: UNT Libraries Government Documents Department

Quaternary Stratigraphy and Paleoceanography of the Canada Basin, Western Arctic Ocean

Description: A report about lithologic, paleontologic, and paleomagnetic analyses of sediment cores from Northwind Ridge in the western Canada Basin which provides a stratigraphic framework for interpreting the upper Quaternary paleoceanographic records of the western Arctic Ocean.
Date: 1994
Creator: Poore, Richard Z.; Ishman, Scott E.; Phillips, R. Lawrence & McNeil, David H.
Partner: UNT Libraries Government Documents Department

Coal Resources of the United States

Description: A report about the United States's coal supply. The U.S. has 25 percent of the world's identified coal resources and about 20 percent of the world's estimated total coal resources.
Date: January 1, 1974
Creator: Averitt, Paul
Partner: UNT Libraries Government Documents Department

Geology of the Clark Fork Quadrangle Idaho-Montana

Description: A report about the Clark Fork quadrangle which is underlain by more than 38,000 feet of low-grade metasedimentary rocks of the Precambrian Belt series. The quadrangle has both metallic and nonmetallic mineral deposits of considerable value.
Date: 1963
Creator: Harrison, J. E. & Jobin, D. A.
Partner: UNT Libraries Government Documents Department