Bedrock Geology Map of the Footwall of the Soudan Iron Formation South of Twin Lakes, St. Louis County, Northeastern Minnesota

Abstract

This map is one of four maps produced from the capstone project of the Precambrian Research Center Field Mapping Course during the summer of 2007. Publication of this map is the beginning of a planned series of detailed maps of the Precambrian Crustal Terrain of northeastern Minnesota. Efforts to obtain this map information were conducted in association with the University of Minnesota-Duluth, Precambrian Research Center and the Natural Resources Research Institute. Such mapping will help aid in the exploration for VMS-style mineralization deposits as well as provide a better understanding of the Twin Lakes supracrustal volcanic stratigraphy. Prior to this project, the geology of the Twin Lakes area was inferred from other published maps. The first of these publications describing the geology in the Twin Lakes area was included in the larger scale regional map of the Lower Ely Greenstone Member, (Sims and Southwick, 1985). Additional mapping and compilation of exploratory data collected by Bear Creek Mining (during the 1960's) was included in a later publication compiled by D. Peterson and M. Jirsa, 1999. Recent mapping by the authors was concentrated in the Twin Lakes region at a scale of 1:5000. The authors mapped 300 outcrops in an area covering approximately 260 hectares south of Twin Lakes. The authors believe that further geological studies (i.e. additional field mapping, petrographic studies, and lithogeochemical studies) should be completed to better constrain the geological and geochemical processes that occurred during the evolution of both the supracrustal and intrusive strata in the Twin Lakes area. Such studies will assist in unambiguously determining the correlations between the geology of the western and eastern parts of the Vermillion District.