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GEOREF RECORD

The effect of metamorphism on metal distribution near base metal deposits

Hubert Lloyd Barnes
The effect of metamorphism on metal distribution near base metal deposits
Economic Geology and the Bulletin of the Society of Economic Geologists (August 1959) 54 (5): 919-943

Abstract

Sedimentary rocks near 3 base metal deposits were analyzed to determine possible changes in Zn, Cu, and Fe content caused by alteration or contact metamorphism. Of the sediments in the Hanover, New Mexico district of "contact metasomatic" Zn-Cu deposits, only the Devonian (Percha) fissile shale contains sufficient Zn (70 p. p. m. Zn, 48 p. p. m. Cu, and 4% Fe) to contribute significantly to the metal content of the deposits. However, this shale has the same metal content (within + or -20 p. p. m. Zn and Cu and within + or - 1% Fe) when unaltered, as in the recrystallized and silicified contact zone (excluding the skarn). Extraction of 20 p. p. m. Zn from the altered area of the shale is quantitatively insufficient to account for the 600,000 metric tons Zn in the skarn and ore deposits of the contact zone. In the northern Mississippi valley district, neither the Maquoketa shale (35 p.p.m. Zn, 65 p.p.m. Cu, and 3% Fe), nor the oil rock (20 p. p. m. Zn, 60 p. p. m. Cu, and 7% Fe) has a sufficient metal content in comparison with the background level given by average igneous rock (100 p. p. m. Zn, 70 p. p. m. Cu, and 5% Fe) to be the source for the metals in the deposits. Near the margins of the San Francisco del Oro district, Chihuahua, Mexico, the gradient of Zn content from the veins into the silicified wall rocks passes through a minimum below that of unaltered shale (123 p. p. m. Zn, 75 p. p. m. Cu, and 5% Fe). However, the quantity of Zn shown by this gradient to have been extracted from the shale is only a negligible fraction of the metal content of the entire deposit. It is quantitatively impossible for the metal content of these 3 districts to have been derived from the surrounding Paleozoic or younger sediments by lateral secretion.


ISSN: 0361-0128
EISSN: 1554-0774
Coden: ECGLAL
Serial Title: Economic Geology and the Bulletin of the Society of Economic Geologists
Serial Volume: 54
Serial Issue: 5
Title: The effect of metamorphism on metal distribution near base metal deposits
Pages: 919-943
Published: 195908
Text Language: English
Publisher: Economic Geology Publishing Company, Lancaster, PA, United States
Accession Number: 1959-042329
Categories: Economic geology of ore deposits
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. geol. sketch maps
N25°45'00" - N32°00'00", W108°00'00" - W103°00'00"
N31°30'00" - N37°00'00", W109°04'60" - W103°00'00"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from Bibliography and Index of North American Geology, U. S. Geological Survey, Reston, VA, United States
Update Code: 1959
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