Midcontinent Rift mafic-ultramafic satellite intrusions

Region Central, North Central
Mineral systems
Deposit types
Critical minerals
Other minerals

Information leading to the delineation of this focus area

Basis for focus area Mapped extent of mafic and ultramafic satellite intrusions related to the 1.1 Ga Midcontinent Rift System.
Identified resources Identified vanadium resources.
Production No known production.
Status Unknown.
Estimated resources Round Lake intrusion (Wisconsin) has a reported resource potential of 50 millions tons of 1.5% V in rock consisting of 72% titaniferous magnetite.
Geologic maps Sims (1992), scale 1:500,000; Jirsa and others (2012), scale 1:500,000.
Geophysical data Inadequate aeromagnetic and aeroradiometric coverage.
Favorable rocks and structures Small mafic and ultramafic intrusions related to the early, magnetically reversed stage of the 1.1 Ga Midcontinent Rift System. Emplaced into country rock outside of the central rift area, and recognized by their geophysical attributes.
Deposits Round Lake intrusion.
Evidence from mineral occurrences Mudrey and others (2003).
Geochemical evidence Geochemical analyses in Schulz, Woodruff and Nicholson (2014).
Geophysical evidence Intrusions typically have strong magnetically reversed signatures, and are small and plug-like shape. Can sometimes be identified in poor quality aeromagnetic data against a background of Archean and Paleoproterozoic country rock.
Evidence from other sources No data.
Cover thickness and description Glacial cover ~ 25 m over the Round Lake intrusion.
Authors Laurel G. Woodruff.
New data needs New mapping, high resolution geophysics.
Geologic mapping and modeling needs At present, OUIs are presented as single lithological units on state maps. More detailed mapping and analysis to further understand lithological relationships to mineralization in the OUI is needed to form the basis for further geological/mineralogical/geochemical/structural/geophysical/mineral potential studies and associated modeling.
Geophysical survey and modeling needs Rank 1 aeromagnetic coverage may reveal additional OUIs, delineate intrusive geometry, and identify structural controls on discovered and undiscovered OUIs.
Digital elevation data needs Lidar adequate.