Stratigraphic, structural, tectonic, and economic studies of the Archean Ishpeming greenstone belt, Marquette County, Michiga

The Archean Ishpeming greenstone belt is located on the southernmost edge of the Wawa subprovince of the Superior province. It is composed of three lithostratigraphic blocks and represents a minimum accumulation of 6,700 meters of mafic and felsic volcanic rocks. The stratigraphic succession is divided into two mafic to felsic volcanic cycles. The two volcanic cycles in the Ishpeming greenstone belt represent the transition from subaqueous shield to caldera/dome complex volcanism within an island arc believed to be associated with north-directed subduction.;The volcanic stratigraphy has undergone multiple Archean deformations. Deformation is due to regional transpression associated with Archean oblique continent-continent collision along the Great Lakes tectonic zone.;Unconformably overlying the volcanic rocks of the Ishpeming greenstone belt is the Reany Creek Formation--a Timiskaming-type sequence of Archean age. The Reany Creek Formation has a "lazy-Z" outcrop pattern and is spatially associated with the Archean Dead River shear zone.;The Ishpeming greenstone belt has the potential to host Archean lode gold, volcanic-associated massive sulfide and komatiite-associated nickel deposits. The complex deformation history of the major shear zones, anomalous gold occurrences, associated broad zones of carbonate alteration and close spatial association with the Reany Creek Formation, a "Timiskaming-type" sequence, are characteristic of giant gold deposits in the Timmins-Kirkland Lake area of Ontario. The occurrence of high-silica rhyolites and anomalous zinc and copper occurrences in the Reany Lake pyroclastic unit of the Lighthouse Point Basalt of the north block suggest the potential for economic volcanic-associated massive sulfide mineralization. The Deer Lake Peridotite may host komatiite-associated nickel mineralization. (Abstract shortened by UMI.).