MAGNETIC AND GRAVITY ANALYSIS AND CRITICAL MINERAL EXPLORATION IN THE NORTHWEST SUPERIOR PROVINCE, MINNESOTA

The Superior Province which is an Archean-aged craton, covers approximately 132,000 square miles across south-central Canada and the north-central United States. The Superior Province in Minnesota consists mainly of a variety of granitic and granitic-type intrusions with lesser amounts of metamorphic lithologies formed by a series of orogenies ranging between 2.8 to 2.6 Ga. The Minnesota Orogeny was the last accretion event and covers most of west-central Minnesota. Additionally, within the Superior Province in northwestern Minnesota, there are minor amounts of Cretaceous clastic sediments, and all bedrock rock units are covered by a thin layer of glacial deposits. The Superior Province is host to numerous world-class ore deposits including banded-iron formations, volcanogenic massive sulfides, and granitoid-hosted gold and copper deposits. Northwestern Minnesota is largely unexplored in terms of potential ore deposits due to the lack of outcrops and detailed geophysical and geochemical surveys. To remedy this situation, a high-resolution aeromagnetic and radioactivity survey was conducted as part of the USGS Critical Mineral program. In conjunction with the available gravity data, a geophysical analysis will be conducted that involves creating a variety of residual and derivative anomaly maps and two and three-dimensional gravity and magnetic models that will be correlated with the available geochemical data. Preliminary gravity and magnetic anomaly maps indicate gravity and magnetic minima on the Bouguer, reduced to the pole magnetic, and residual gravity and magnetic anomaly maps correlate with Archean granite intrusions while gravity and magnetic maxima correlate with banded-iron formations and basaltic dikes. The larger scale gravity and magnetic anomalies all on maps trend SW-NE while the anomalies due to the iron formations and dikes trend SE-NW. The derivative analysis confirms the above and provides more exact location of the source bodies. Future work involves creating additional residual anomaly maps, and subsurface models and using machine learning methods in conjunction with geochemical data to predict which areas are best for more detailed mineral exploration.