Abstract

A stratabound tungsten (scheelite) occurrence is exposed in Proterozoic (1650–1720 Ma) metamorphic terrane near Santa Fe, New Mexico, and may be the first volcanogenic-exhalative tungsten deposit recognized in the United States. The tungsten-bearing horizon is composed of disseminated scheelite within epidote-actinolite rock, exhibits pronounced mineralogic zoning and anomalous metal contents, and is localized along the contact between sulfide-bearing felsic tuffs and cherts and barren basalts and mafic sediments. It is interpreted as a syngenetic tungsten deposit exhaled as a chemical sediment at the close of a volcanic cycle and subsequently metamorphosed to lower amphibolite facies and deformed. We suggest that other tungsten deposits in Precambrian terrane in the western United States may also be volcanogenic-exhalative. Application of this model to exploration could lead to additional discoveries.

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