Geology of the Nevada Scheelite Mine, Mineral County, Nevada

Abstract

The Nevada Scheelite area is underlain by a Mesozoic sequence of volcanic, volcanoclastic, and carbonate rocks of Jurassic-Triassic age, in part correlative with the Middle Triassic Luning Formation of west- central Nevada. The tungsten deposit of the Nevada Scheelite Mine is a scheelite- bearing contact metasomatic deposit developed at the contact of Jurassic- Triassic limestone with Cretaceous biotite granodiorite. The tactite display weak calc-silicate zonation from intrusive outward of a garnet- scheelite zone followed by either an epidote, amphibole, or wollastonite zone. Formation of tactite followed an evolutionary trend from an early oxidized assemblage of andraditic garnet, epidote, and Molybdenum-bearing scheelite to a late, in the most part, retrograde assemblage of actinolite and ferroactinolite which formed contemporaneously with sulfidation of the tactite. Scheelite was deposited later than garnet and epidote, prior to sulfides and amphiboles, and is most abundant in the garnet-scheelite zone. Localization of major ore bodies is controlled by large scale reentrants, and embayments of marble into granodiorite.