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Genetic model for the Gilman District, based on fluid inclusion, stable isotope, alteration/vein/replacement distribution, and fission-track geochronologic studies

By
David W. Beaty
David W. Beaty
Chevron Oil Field Research CompanyP.O. Box 446, La Habra, CA 90633-0446
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C.W. Naeser
C.W. Naeser
U.S. Geological SurveyMail Stop 424, P.O. Box 25046, Denver Federal Center, Denver, CO 80225
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C.G. Cunningham
C.G. Cunningham
U.S. Geological Survey959 National Center, Reston, VA 22092
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Gary P. Landis
Gary P. Landis
U.S. Geological SurveyMail Stop 963, P.O. Box 25046, Denver Federal Center, Denver, CO 80225
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Published:
January 01, 1988

Abstract

A large manto/chimney complex is located at Gilman, Colorado, about 120 km WSW of Denver. The district was discovered in 1879, was consolidated beginning in 1912 by New Jersey Zinc Company as the Eagle mine, and was closed in 1984. Cumulative production of all ore types has been about 11.7 million metric tons with an average grade of 8.5% Zn, 1.5% Pb, 0.7% Cu, 228 gpt (grams per metric ton) Ag, and 1.7 gpt Au (Beaty et al., 1989).

At Gilman, a sequence of Cambrian through Mississippian sedimentary rocks (total stratigraphic thickness-200 m) dip homoclinally eastward at 12-15°. These sedimentary rocks unconformably overlie Precambrian basement (predominantly the Cross Creek batholith), and are in turn overlain by 3000+ m of coarse elastics of the Pennsylvanian Minturn Formation. The sedimentary rocks in the Gilman area are intruded by one exposed igneous mass, the Pando Porphyry, which forms a sill 12–27 m thick in the Belden shale. The Pando Porphyry is a fine-grained quartz latite which crystallized at about 72 Ma (data of Pearson et al., 1962 recalculated by Beaty et al., 1987).

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Contents

Society of Economic Geologists Guidebook Series

Geology and Mineralization of the Gilman-Leadville Area, Colorado

T. B. Thompson
T. B. Thompson
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David W. Beaty
David W. Beaty
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Society of Economic Geologists
Volume
2
ISBN electronic:
9781934969557
Publication date:
January 01, 1988

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