A geophysical investigation of the Ely Greenstone belt in the Soudan area, northeastern Minnesota: A preliminary investigation for the proposed deep underground science and engineering laboratory (DUSEL), University of Minnesota

Abstract

Gravity and magnetic data were used investigate the subsurface structure of the Ely Greenstone belt in the vicinity of the DUSEL site in Northeastern Minnesota. The main part of the work consisted of regional-scale gravity and magnetic model studies along 5 profiles, which were constrained by rock property determinations of density, magnetic susceptibility, and natural remanent magnetization (NRM). The results indicate that the steep northward dips that are observed at the surface persist at depth, and the greenstone belt extends down to roughly 5 kilometers depth, or possibly more. It is reasonable to assume that the major geologic units of the greenstone belt extend down to similar depths. The results of the model studies imply that major changes in greenstone belt stratigraphy or structure should not be expected at the 2.5 km depth that is currently proposed for the DUSEL site.