The geology and geochemistry of the 194 orebody, Getchell Mine, Humboldt County, Nevada

The 194 orebody is a compact, high-grade gold, collapse-breccia body located in the Getchell underground mine, Nevada. The orebody measures approximately 180 m (600 ft) high, 120 m (400 ft) long, and up to 50 m (165 ft) wide. The primary host rocks for gold mineralization comprise silty, variably carbonaceous calcarenite limestone of the Cambrian Preble Formation. The orebody occurs at the intersection of a 30 to 45 m- (100 to 150 ft-) wide northeast fault zone and a 100 m- (325 ft-) wide east-west fault system. Decarbonatization and fluid-rock reactions were most intense in the highly fractured reactive rocks, resulting in extensive loss of strata and the formation of collapse brecciation. Cavefill was deposited as internal sediments in open cavities in the orebody. Galkhaite, a late gold-stage mineral, was dated at 39 +/- 2.1 Ma, which is considered the date of gold mineralization in the Getchell mine.