This study is designed to shed light on processes that deposit gold in Carlin-type deposits, which are the main source of gold outside South Africa. Gold in these deposits is found in arsenic-rich pyrite that is disseminated throughout the host rocks. Previous work at one deposit, Twin Creeks, shows that: 1) iron in mineralized rocks with high concentrations of gold is in pyrite, 2) iron in barren rock that lacks gold is in minerals other than pyrite, and 3) iron contents of mineralized and barren rocks are the same. These relations suggest that iron in mineralized rocks was converted to pyrite and that this caused gold deposition by the process known as sulfidation. The present study will attempt to determine whether sulfidation took place at other Carlin-type deposits and whether this is a general mechanism for deposition of gold in these deposits. This study also will test preliminary observations at Twin Creeks which suggest that the distribution of ferroan dolomite in sedimentary rocks reflects their post-depositional history. The results of this research will be useful in guiding exploration for new Carlin-type deposits.
