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Published August 1, 1977 | Submitted
Journal Article Open

U-Pb isotope ages of granitic plutons near Cananea, Sonora

Abstract

The Cananea "granite" crops out in the Cananea mining district, which includes some of the most important known copper deposits in Mexico. The area is in northern Sonora, approximately 100 km southeast of the twin cities of Nogales, Arizona-Sonera, on the international border.By means of isotopic analyses of U-Pb systems in cogenetic suites of zircon from two different phases of the pluton, its interpreted age has been firmly established at 1,440 + or - 15 m.y. Cananea granite, actually a quartz monzonite, is lithologically characteristic of a major Precambrian suite of anorogenic, consanguineous plutons of porphyritic granodiorite to granite. Constituents of this previously recognized series, which crop out throughout the southwestern U. S. and into northern Mexico, consistently yield zircon radiometric ages within the interval 1,425-1,475 m.y.Major younger intrusions in and nearby the Cananea district include Cuitaca granodiorite and Chivato monzodiorite. These bodies yield apparent zircon ages of 64 + or - 3 and 69 + or - 1 m.y., respectively. Although more precise geochronologic relationships between young plutons, the adjacent layered sequence, and cross-cutting, brecciated, quartz porphyry plugs are needed, correlation exists between major plutonism and mineralization.The Precambrian age of the Cananea granite precludes its chronological association with the younger mineralized plugs and should be taken into account in future planning of exploration.

Additional Information

© 1977 Society of Economic Geologists. April 9, October 14, 1976. Throughout our investigations Ing. Ramon Ayala and Ing. Guillermo A. Salas, geologists at Compania Minera de Cananea, S. A., were cooperative and most helpful while maintaining friendly skepticism. Mineral separations by O. Shields and Jaime Alvarez, as well as numerous noted and unnoted feats of chemistry and mass spectrometry by Gerri Silver and Maria Pearson, are most kindly acknowledged. This work was supported by NSF Grants GA-15989 and EAR 74-00155 A01 (formerly GA-40858) awarded to Caltech.

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August 22, 2023
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October 24, 2023