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TitleStratigraphic and structural setting of banded-iron-formation-hosted gold mineralisation in the Geraldton area, Ontario
AuthorTóth, Z; Lafrance, B; Dubé, B; McNicoll, V J; Mercier-Langevin, P
SourceGeological Association of Canada-Mineralogical Association of Canada, Joint Annual Meeting, Abstracts Volume vol. 37, 2014 p. 272-273
LinksOnline - En ligne
Alt SeriesEarth Sciences Sector, Contribution Series 20130617
MeetingGAC-MAC 2014; Joint annual meeting of Geological Association of Canada and Mineralogical Association of Canada; Fredericton; CA; May 21-23, 2014
File formatpdf
AreaGeraldton; Mosher Lake
Lat/Long WENS-87.0000 -86.5000 49.7500 49.5000
Subjectsstructural geology; economic geology; stratigraphy; mineral occurrences; mineral deposits; gold; mineralization; volcanogenic deposits; sulphides; sulphide deposits; iron formations; structural features; hydrothermal alteration; tectonic evolution; Archean; metasedimentary rocks; igneous rocks; volcanic rocks; volcaniclastics; rhyolites; dykes; deformation; folds; faults; Beardmore-Geraldton Belt; Wabigoon Subprovince; Precambrian; Proterozoic
ProgramTargeted Geoscience Initiative (TGI-4), Gold Ore Systems
AbstractThe Beardmore-Geraldton Greenstone Belt (BGB) is located along the boundary between the Wabigoon and Quetico subprovinces of the Archean Superior Province. It produced more than 4.1 million ounces of gold over the past century. This project aims to characterise the age and provenance of the sedimentary rocks and intrusions hosting mineralisation, to determine the timing and genesis of gold mineralisation with respect to the four deformation events that affected the area, to characterise the mineralogical assemblage and geochemical footprints of the mineralised system and the associated hydrothermal alteration. The BGB is composed of structurally interleaved panels of metasedimentary and metavolcanic rocks. The metavolcanic units represent back-arc basin, oceanic island arc and MORB-type oceanic crust. The metasedimentary units formed a southward-prograding clastic wedge. Sandstone and conglomerate samples were collected across the BGB and along the northern margin of the Quetico Subprovince for U-Pb detrital zircon geochronology. All BGB sandstone samples have very similar zircon age populations, with the youngest population dated at ~2700Ma. The BGB conglomerate has a youngest zircon population age of 2711Ma, similar to that of the Quetico sandstone. This is consistent with a previous interpretation of the BGB as a transitional zone between the Wabigoon and Quetico subprovinces. The sedimentary rocks of the BGB were deposited prior to the emplacement of a quartz-feldspar porphyry which has a crystallization age of 2694±1Ma. The age of the porphyry represents the maximum age for gold mineralisation in the Geraldton area as it hosts auriferous quartz-carbonate veins.
The deformation history of the belt began with D1 thrusting followed by D2 north-south compression and D3 dextral shear. A previously unrecognised, sinistral transcurrent shear occurred prior to D3 dextral shear. Gold deposits in the Geraldton area are associated with a major fault zone next to the boundary between two subprovinces. As such they share analogies with world-class gold districts such as Timmins. Gold occurs in quartz-carbonate veins and their sericite ± carbonate ± chlorite and pyrite ± arsenopyrite alteration haloes hosted within mudstone, sandstone, banded iron formation and quartz-feldspar porphyry. Most gold-bearing veins are folded by F2 folds suggesting pre- or early-D2 gold mineralisation. Thus, an early stage deformation most probably played a key role in the formation of gold deposits in the BGB.