Modern technology and renewable energy require large amounts of metals that are derived from minerals. Many of these resources are imported, and there is a tremendous effort to domesticate our mineral extraction and processing. Several of these critical minerals, such as Ti, are found in Wisconsin, but little data is available to guide future mineral exploration efforts. This study describes the petrology and geochemistry of the Round Lake Ti Deposit in northern Wisconsin using historic drill cores stored at the WGNHS. The Round Lake intrusion that hosts the Ti mineralization is related to 1.1 Ga Mid-Continent Rift magmatism. The main intrusion is a magnetite-ilmenite rich gabbro, ranging from 35-50% magnetite-ilmenite and 15-50% coarse grained plagioclase laths. Movement and flow of magmas during emplacement formed porphyritic and trachytic textures with aligned plagioclase crystals. In addition, there are other intrusive phases associated with the magnetite-ilmenite gabbro intrusion. The anorthosite has 55-90% euhedral plagioclase, 10-15% magnetite, and 5-15% pyroxene. The magnetite rich gabbro and anorthosite make up the intrusion and is crosscut by a fine-grained gabbro and granitic dikes. Petrographic and geochemical data and interpretations improve our understanding of Ti-bearing magmatism in the Mid-Continent Rift system.
