Multiple folding and pluton emplacement in Archean migmatites of the southern Vermilion granitic complex, northeastern Minnesota

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Abstract
Analysis of folding in the southwestern Vermilion granitic complex suggests that F2 folds, which formed in a regional north–south compressional regime, were locally reoriented during pluton emplacement and were subsequently refolded by F3 folds generated by continuing north–south compression. An east–west-trending F2 antiform, crossing the boundary between the southern Vermilion granitic complex and the adjacent Vermilion district, was intruded by a tonalite pluton during the later stages of F2 folding. Either emplacement of the pluton or emplacement of the nearby Lac La Croix batholith is believed to have reoriented the F2 fold so that, subsequently, the pluton and the F2 antiform were refolded by a doubly plunging east–west-trending F3 fold, now cored by the pluton.A similar relationship occurs between F2 and F3 folds north of the Vermilion fault in the main portion of the complex. Here, F3 conical folds, not cored by plutons, refold F2 folds about northwest-trending vertex axes. Analysis of the refolding of minor F2 folds and L2 lineations in this area suggests they were nearly coaxial with the F3 folds prior to the F3 folding.

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