Mineralogy and Paragenesis of Ore Stage Mineralization in the Betze Gold Deposit, Goldstrike Mine, Eureka County, Nevada
G.C. Ferdock, S.B. Castor, R.W. Leonardson, T. Collins, 1997. "Mineralogy and Paragenesis of Ore Stage Mineralization in the Betze Gold Deposit, Goldstrike Mine, Eureka County, Nevada", Carlin-Type Gold Deposits Field Conference, Peter Vikre, Tommy B. Thompson, Keith Bettles, Odin Christensen, Ron Parratt
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The Betze gold deposit in the Goldstrike Mine, north-central Carlin Trend, Eureka County, Nevada, is the largest known, sedimentary rock-hosted, disseminated gold deposit containing 32 million ounces of gold (Leonardson and Rahn, 1996)(Fig.1). The paragenesis of hydrothermal mineralization characterizes the nature of gold mineralization in the deposit. This paper describes stages of gold ore mineralization determined from hand specimen and thin section petrology, XRD analysis and SEM studies; mineral formulae reported are those from Frondel (1962) and may not be exact. The stages result from a poly-phase, mineralizing event that has determined the conditions under which gold was precipitated.
Previous studies of paragenesis and associated hydrothermal minerals of Carlin-type deposits were conducted by Arehart et al. (1993a), Bakken and Einaudi (1986), Kuehn and Rose (1992), Peters (1996) and Peters et al. (1997) who determined relative paragenesis of mineralization in a general one or two stage hydrothermal event. Our investigations suggest that three stages of hydrothermal mineral development are associated with gold ore mineralization in the Betzedeposit: Stage I: Early (pre-primary gold deposition); Stage II: Main (primary gold deposition), and Stage III: Late (post-primary gold deposition). Pre-gold stage mineralization events include diagenesis of the sediments and metasomatic processes associated with the intrusion of the dioritic Goldstrike stock. Hydrothermal minerals associated with an individual stage generally are limited to each stage; however, overlap of the major gangue minerals, such as quartz, illite, and sericite (Fig. 2) is common. Some mineralogical overlap between stages is due to cycling of circulating fluid that