Paper No. 1
Presentation Time: 1:30 PM
MINERALOGY OF CARLIN-TYPE DEPOSITS IN THE GREAT BASIN, NEVADA AND UTAH, UNITED STATES OF AMERICA
The mineralogy of Carlin-systems is, at first glance, staggering. In excess of 300 mineral species have been identified in the various deposits (nearly 160 at the Goldstrike Mine alone), ranging from mundane to very exotic and extremely rare. Eleven new mineral species have been described from these deposits, and others are pending. The mineral assemblages differ from deposit to deposit, depending on host rock composition and variations in the chemistry of the ore fluids. However, general mineralogy is similar from deposit to deposit, as is paragenesis, spatial distribution and zonation. Minerals found in Carlin-type deposits generally fall into one of six genetic categories, from earliest to latest: I.) original sedimentary and diagenetic minerals; II.) igneous and metamorphic minerals (in Paleozoic to Cenozoic mafic to silicic intrusive and volcanic rocks and accompanying metamorphic halos); III.) early pre-gold hydrothermal minerals with clay and chemically simple sulfides; IV.) gold-bearing sulfides; V.) waning gold deposition with formation of As-Sb-Zn-(Tl) sulfides and sulfosalts along with Ba-(Ca) sulfate (including the bulk of the complex sulfosalts and rare halides); VIA. and VIB.) post-gold secondary mineralization related to hypogene (A) and supergene (B) processes. Few species form in more than one of these categories with the exceptions of pyrite, some base metal sulfides (e.g. sphalerite), quartz, calcite, dolomite, illite and, to a lesser extent kaolinite, graphite and gypsum.