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Published 1976 | Published
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Plumbotectonics IIA, Precambrian massive sulfide deposits


Professor Tugarinov has long recognized the importance of common lead in rocks and ore deposits as an age indicator. The paper he authored with L. K. Gavrilova and V. P. Bedrinov in 1963, and the work of Cantanzaro and Gast (1960), are two of the most extensive studies of the evolution of lead isotopes in feldspars. Such studies are very important to our understanding of crustal evolution because of our ability to calibrate feldspar ages by other means. The pioneer paper by Stanton and Russell (1959) opened the way for dating certain deposits submarine volcanic exhalative massive sulfide deposits in the orogene. It is now generally accepted that these deposits formed during volcanism or shortly thereafter (Hutchinson, 1973). Therefore their lead isotope evolution may be correlated with time by dating the enclosing rocks. Over the last eight years, investigators have gradually realized that lead isotopic analyses, coupled with geochronologic studies, may yield much additional information about ore deposits and their origins. This paper evaluates the lead isotopic characteristics of Precambrian massive sulfide deposits of all types. The treatment here will be similar to that used by Doe and Zartman (1976) in their "plumbotectonics" model for Phanerozoic deposits of this type. The submarine volcanic exhalative ores were chosen for emphasis because they are the type class for "conformable" or "stratiform" leads used in lead isotope model theory. We suggest that any deviation from a strictly average isotopic composition for a given age of deposit can often be explained by differences in the tectonic settings in which the ores were formed. This paper is a "state-of-knowledge" discussion of that thesis.

Additional Information

We wish to thank C. A. Anderson of the University of California at Santa Cruz for the samples from Arizona and discussions concerning them. Gary Landis of the University of New Mexico provided the samples from New Mexico. Thomas Kalk of Noranda Exploration, Inc. donated the sample from Rhinelander, and Edwarde May of the Flambeau Mining Corporation gave us the samples from Ladysmith. Olavi Kouvo of the Geological Survey of Finland provided the samples from Finland and the information on their occurrence. Robert Houston of the University of Wyoming gave us the sample from, and background information on, the Wyoming deposit. Brian Skinner of Yale University sent us the sample from New Jersey. We wish to thank M. R. Stauffer of the University of Saskatoon for permission to quote unpublished information on the Manitoba deposits, D. F. Sangster of the Geological Survey of Canada for discussions of other Canadian deposits, and G. L. Snyder of the U.S. Geological Survey for providing descriptions of the Colorado deposits The new analyses were made by M. H. Delevaux of the U.S. Geological Survey using the triple-filament thermal emission technique, and the ratios were converted to absolute through repeated analyses of the NBS 981 substandard. The ratios are thought to be within 0.1 percent of absolute. Randall Rohrbough of the U.S. Geological Survey developed the automated plotting program that greatly aided the data analysis.

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August 19, 2023
January 15, 2024