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The composition of magnetite in Archean mafic-ultramafic intrusions within the Superior Province
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|Authors:||Sappin, A. -A.; Houlé, M. G.|
|Volume Title:||Targeted Geoscience Initiative 5: Advances in the understanding of Canadian Ni-Cu-PGE and Cr ore systems - Examples from the Midcontinent Rift, the Circum-Superior Belt, the Archean Superior Province, and Cordilleran Alaskan-type intrusions|
|Volume Authors:||Bleeker, W., editor|
|Source:||Targeted Geoscience Initiative 5: Advances in the understanding of Canadian Ni-Cu-PGE and Cr ore systems - Examples from the Midcontinent Rift, the Circum-Superior Belt, the Archean Superior Province, and Cordilleran Alaskan-type intrusions, edited by W. Bleeker and M. G. Houlé. Open-File Report - Geological Survey of Canada, No.8722, p.181-196. Publisher: Geological Survey of Canada, Calgary, AB, Canada|
|Note:||In English. This publication is contained in Targeted Geoscience Initiative 5: Advances in the understanding of Canadian Ni-Cu-PGE and Cr ore systems - Examples from the Midcontinent Rift, the Circum-Superior Belt, the Archean Superior Province, and Cordilleran Alaskan-type intrusions, Geological Survey of Canada, Open File 8722, 2020. 32 refs.; illus., incl. tables|
|Summary:||The mineral chemistry of magnetite from eleven Archean mafic, mafic-ultramafic, and ultramafic intrusions within the Superior Province was determined to be used as a petrogenetic indicator and to identify the most prospective areas for exploration of Fe-Ti-V and Fe-Ti-P mineralization. The composition of magnetite is influenced by the presence of exsolutions and inclusions (e.g. ilmenite, Al-spinel), the type of parental melt (e.g. komatiitic, basaltic) and its Ti contents (e.g. high-Ti or low-Ti parental magmas), and the element partitioning with co-crystallized minerals (e.g. clinopyroxene) or previously crystallized minerals (e.g. chromite). The overall composition of magnetite, however, appears to be mainly independent of the host-rock type. The composition of magnetite in compatible (e.g. Mg, Co, V, Ni, and Cr) and incompatible (e.g. Al, Ga, Mn, Ti, Zn) elements during fractionation processes also provides useful information about the degree of differentiation of the host intrusions. Among the studied intrusions with a mafic-dominated composition, the Riviere Bell and Lac Dore complexes appear to be the most evolved, whereas the Croal Lake, Big Mac, Butler, and Wabassi Main intrusions and the Highbank-Fishtrap intrusive complex are the most primitive. Furthermore, the variation of the minor and trace element contents of the magnetite could be used to determine the internal stratigraphy within the mafic to ultramafic intrusions. For example, in the mafic-dominated Big Mac intrusion and in the ultramafic-dominated Baie Chapus Pyroxenite, the more vent-proximal facies appear to be located to the north and to the east, respectively. In addition, the V and Ni+Cr contents of magnetite from the Big Mac intrusion suggest that the northern part of this intrusion is a prospective area for Fe-Ti-V mineralization, whereas the southern part has more potential for Fe-Ti-P mineralization. In the Baie Chapus Pyroxenite, the concentrations in V and Ni+Cr in magnetite support the prospectivity of this intrusion for Fe-Ti-V mineralization. Magnetite from the oxide-bearing mafic to ultramafic rocks and the semi-massive to massive Fe-Ti oxide layers have lower Ti+V values than expected, with magnetite compositions plotting within the fields for hydrothermal deposits in Ni/(Cr+Mn) versus Ti+V, Ca+Al+Mn versus Ti+V, and Ni+Cr versus Ti+V discrimination diagrams. Considering that the Fe-Ti-V deposit fields in these diagrams were mostly defined based on Fe-oxides hosted within Proterozoic and Phanerozoooic Fe-Ti deposits, the preliminary results presented here suggest there may be a specific signature for magnetite from Archean Fe-Ti-V-oxide-bearing intrusions. However, further work is required to confirm this distinct signature to the Archean.|
|Subjects:||Archean; Bedrock; Chemostratigraphy; Controls; Cores; Crystal fractionation; Dikes; Electron probe data; Emplacement; Exploration; Exsolution; Fluid dynamics; Genesis; Greenstone belts; Host rocks; Igneous rocks; Inclusions; Intrusions; Iron ores; Komatiite; Mafic composition; Magmas; Magnetite; Mass spectroscopy; Mesoarchean; Metal ores; Metamorphic belts; Mineral assemblages; Mineral deposits, genesis; Mineral exploration; Mineral resources; Mineralization; Minor elements; Neoarchean; Oxides; Phosphorus; Plutonic rocks; Precambrian; Pyroxenite; Samples; Spectroscopy; Sulfides; Tectonics; Titanium ores; Trace elements; Ultramafic composition; Ultramafics; Vanadium ores; Volcanic rocks; Abitibi Belt; Canada; Canadian Shield; Eastern Canada; Manitoba; North America; Ontario; Quebec; Superior Province; Western Canada; Hydrothermal processes; Igneous activity; Igneous processes|
|Coordinates:||N050000 N620000 W0640000 W1000000|
|Copyright Information:||GeoRef, Copyright 2021 American Geosciences Institute. Produced under license from Her Majesty the Queen in Right of Canada, represented by the Minister of Natural Resources|
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