Ore Petrography and Composition Comparison of the Flambeau and Eisenbrey Massive Sulfide Deposits

Abstract

Volcanogenic massive sulfide (VMS) deposits are polymetallic mineral deposits that contain many base and precious metals such as copper, zinc, lead, gold, and silver. This study focuses on two Paleoproterozoic VMS deposits found within the Pembine-Wausau Terrane in northern Wisconsin: the Flambeau and the Eisenbrey. Despite the Flambeau and Eisenbrey being located only 4 miles from each other, they each show their own unique stratigraphy and ore mineralogy. Even though these deposits contain so much economic potential, the Flambeau is the only deposit to have been mined. Mining occurred between 1993 and 1997 and was closed just after the supergene ore was extracted. By using drill core samples from the Wisconsin Geological and Natural History Survey core repository, we were able to quantify the abundances of different ore minerals throughout their ore stratigraphy using reflected light petrography and scanning electron microscopy. Certain major and trace ore minerals form under specific hydrothermal fluid conditions); therefore, observing these mineralogical and textural variations within the ore bodies can provide important information regarding the ore-forming environments and can have implications for future mineral exploration.