Reconstructing Paleoproterozoic Volcanism in Northcentral Wisconsin: Geology of the Lobo Zn-Cu Deposit

Abstract

The Lobo Zn-Cu deposit in northwestern WI, USA, is one of several volcanogenic massive sulfide (VMS) deposits in the state. This deposit has never been mined; therefore, further studies can only be conducted by examining the hypogene geology through drill cores that are found at the Wisconsin Geological and Natural History Survey (WGNHS) in Mt. Horeb, WI. The Lobo deposit is a part of the Wisconsin Magmatic Terranes composed of plutonic, volcanic, and sedimentary rocks that were accreted during a collision between the Pembine-Wausau terrane and Superior craton during the Paleoproterozoic Penokean orogeny. This tectonic setting has since been overprinted by many regional metamorphism events. The host rocks of the Lobo deposit are primarily sericite-altered lapilli tuff. This project aims to assess the magmatic and tectonic affinity of the host rocks to provide an insight to the petrogenesis of the Lobo volcanic system and control on VMS mineralization during the ocean-continent collision.