Geology of volcanic rocks in the south half of the Ishpeming greenstone belt, Michigan

The south half of the Ishpeming greenstone belt is dominated by a thick succession of subaqueously erupted volcanic rocks. A regional structural interpretation of the belt provides a framework for placing this succession in a stratigraphic order. The south half of the Ishpeming greenstone belt preserves the remnants of overlapping subaqueous volcanic complexes within an arc system. The Kitchi Formation comprises the lower half of the volcanic succession and is subdivided into three informal units. The Kitchi Formation represents an evolving tholeiitic, mafic shield to calc-alkalic, mafic to felsic subaqueous volcano. The Mona Formation is in structural contact with the Kitchi Formation, but is likely younger. It is subdivided into three informal units and represents an evolving tholeiitic, mafic shield to mafic-felsic calc-alkalic, mafic to felsic subaqueous volcano. The Deer Lake Peridotite, an ultramafic sill complex that intrudes the Kitchi Formation, is speculatively interpreted as a subvolcanic ultramafic komatiite base of the Mona Formation. -from Authors