Browsing by Subject "Gneiss"

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    GEOPHYSICAL AND PETROLOGIC INVESTIGATIONS OF INVERSELY CORRELATED AEROMAGNETIC AND BOUGUER GRAVITY ANOMALIES WITHIN PRECAMBRIAN GNEISS TERRANE NEAR GARVIN, SOUTHWESTERN MINNESOTA
    (Minnesota Geological Survey, 2023) Southwick, David L; Chandler, V.W.; McSwiggen, Peter L
    Geophysical models and petrologic inferences presented here are consistent with a buried gabbroic to noritic intrusion as the principal source of two geographically coincident, kilometer-scale, inversely correlated gravity and magnetic anomalies (the Garvin anomalies) located within Archean continental crust near the present-day southern margin of the Superior Craton in Minnesota. Two-dimensional profiles modeled from the total magnetic anomaly, reduced to pole, and the Bouguer gravity anomaly, upward-continued to 2 kilometers, are fit to geologically reasonable distributions of source rocks that have density and magnetic susceptibility values within the ranges reported for gabbro or norite intrusions.