Breccia Types in the Betze Orebody, Goldstrike Mine, Eureka County, Nevada

Abstract This paper describes outcrop- and hand specimen-scale breccias in the Betze orebody, which is the largest gold deposit on the Carlin trend (Bettles and Lauha, 1991; Leonardson and Rahn, 1996). The Betze orebody lies in the north-central part of the Carlin trend in the Goldstrike Mine (Fig. 1), and it is part of the Betze-Post deposits (Arehart et al., 1993; Lauha and Bettles, 1993; Smith and Sharon, 1994; Leonardson and Rahn, 1996). The orebody and much of the internal breccia bodies have a general WNW strike, with a sub-horizontal attitude (Peters, 1996; 1997). The open pit Goldstrike Mine exposes the Betze and Post orebodies, the Post anticline (Fig. 2), contacts between the Silurian and Devonian Roberts Mountains Formation, Devonian Popovich limestone and Devonian Rodeo Creek unit, and the northern contact of the Jurassic Goldstrike stock (Volk and Zimmerman (1991). Breccia bodies host much of the Betze ore body. Breccias are common rock types in most Carlin-type deposits (Williams, 1992, 1993), and they are particularly common in ore bodies of the north-central Carlin trend (Clode, 1993; Griffin et al., 1993; Leach, 1993). The host rocks in the Betze orebody are altered and deformed. The complex descriptive geology of the Goldstrike Mine is detailed by Volk et al. (1996), Peters et al.(1996), and Leonardson and Rahn (1996). The WNW-striking Dillon deformation zone (DDZ) hosts the upper central Betze orebody (Fig. 2) and contains several ore types associated with breccia (Peters, 1996, 1997). Rock types that host the orebody include phyllonitic black to