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Paleomagnetism of the native copper mineralization, Keweenaw Peninsula, Michigan

Symons, David T. A ; Kawasaki, Kazuo

Canadian journal of earth sciences, 2019-09, Vol.56 (9), p.932-947 [Periódico revisado por pares]

Ottawa: National Research Council of Canada

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Título:
Paleomagnetism of the native copper mineralization, Keweenaw Peninsula, Michigan
Autor: Symons, David T. A ; Kawasaki, Kazuo
Assuntos: Caledonia Mine ; Copper ; copper ores ; Deformation ; Delaware Mine ; Demagnetization ; Economic geology ; Extrusion ; Fluids ; Geochronology ; Haematite ; Hematite ; Houghton County Michigan ; Houghton Michigan ; Infusion fluids ; Keweenaw County Michigan ; Keweenaw Peninsula ; Keweenawan ; Lake formation ; Lakes ; lithostratigraphy ; magnetic properties ; magnetic susceptibility ; Magnetism ; Magnetite ; magnetization ; metal ores ; Michigan ; Michigan Upper Peninsula ; Mineralization ; natural remanent magnetization ; Ontonagon County Michigan ; Oxidation ; oxides ; Palaeomagnetism ; Paleomagnetism ; Polarity ; pole positions ; Portage Lake Lava Series ; Precambrian ; Proterozoic ; Remanent magnetization ; Tectonics ; thermal demagnetization ; United States ; Uplift ; upper Precambrian ; Weathering
É parte de: Canadian journal of earth sciences, 2019-09, Vol.56 (9), p.932-947
Descrição: The age and genesis of Michigan's world-class native copper deposits are poorly constrained. The copper is hosted by basaltic flow tops and conglomeratic interbeds of the 1095 ± 2 Ma Keweenawan Portage Lake Formation. Progressive thermal demagnetization isolates stable hematite remanent magnetization components at 28 paleomagnetic sites. Paleomagnetic tilt tests show that magnetite in massive flow interiors is primary (1095 ± 2 Ma) and that hematite throughout the formation is syntectonic. The altered cupriferous deposits contain primary ∼1095 Ma and secondary ∼1053 Ma hematite in various proportions. The Caledonia Mine's basaltic mineralization carries the ∼1053 Ma hematite dominantly whereas the Delaware Mine's conglomeratic interbed mineralization carries the ∼1095 Ma hematite dominantly. The ∼1095 Ma hematite is attributed mostly to magnetite exsolution during flow extrusion and to weathering oxidation between extrusion events. An infusion of epigenetic hydrothermal fluids emplaced the native copper with additional hematite and polarity self-reversing titanohematite at 1053 ± 7 Ma. Importantly, paleomagnetic evidence supports a 1053 ± 7 Ma age also for the White Pine stratiform sedimentary copper mineralization, for the oxidation of the Oronto Group clastic rocks to red beds, and for the time limits of major tectonic uplift and deformation on the Keweenaw Peninsula.
Editor: Ottawa: National Research Council of Canada
Idioma: Inglês

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Paleomagnetism of the native copper mineralization, Keweenaw Peninsula, Michigan

Symons, David T. A ; Kawasaki, Kazuo

Ottawa: National Research Council of Canada

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