Determining the relationship between intrusive and volcanic rocks at the Lynne Zn- Cu-Pb Deposit, Oneida Co. Wisconsin

Abstract

The purpose of this research is to determine the temporal relationship between the intrusions and the surrounding volcanic rocks hosting the Lynne Zn-Cu-Pb deposit in Oneida County, WI. Volcanogenic massive sulfide (VMS) deposits are among the richest sources of copper, zinc, lead, silver, and gold that are associated with submarine volcanism in extensional tectonic settings. During the Paleoproterozoic (1.8-1.9 Ga) Penokean Orogeny, ancient VMS deposits formed in Wisconsin due to back-arc volcanism within the Pembine-Wausau Terrane. The Lynne deposit, discovered by Noranda Exploration in 1990, is one of several VMS deposits with economic potential in northern Wisconsin. Petrographic observations of the Lynne drill core show the presence of felsic and mafic dikes, along with a large granophyre/granodiorite pluton at the bottom of the deposit. The felsic dikes are fine grained and light in color. The mafic dikes appear fine grained, dark in color, and are occasionally accompanied by plagioclase phenocrysts. The granodiorite and granophyre are coarser grained and present in multiple colors ranging from shades of grey to yellows and pinks. Geochemical data obtained from these samples will enable direct comparisons of the tectonic and magmatic settings between intrusive and volcanic rocks.