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Major ore types of the Lalor gold-rich massive sulfide deposit, Snow Lake, Manitoba.

Duff, Shamus; Hannington, Mark D.; Caté, Antoine; Mercier-Langevin, Patrick; Kjarsgaard, Ingrid; Dubé, Benoît; Gagné, Simon (2013). Major ore types of the Lalor gold-rich massive sulfide deposit, Snow Lake, Manitoba. In: GAC/MAC Annual Meeting, 22-24 mai 2013, Winnipeg, Canada.

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The Lalor deposit is a recently opened (August 2012) Au-Cu-Zn VMS deposit located in Snow Lake, Manitoba, at the east end of the Paleoproterozoic Flin Flon-Snow Lake greenstone belt within a tectonostratigraphic sequence known as the Snow Lake Arc (SLA) assemblage. At an estimated 27 Mt, (reserves plus resources) it is the largest deposit within the SLA assemblage. Eleven ore zones have been identified: 6 base metal-rich zones and 5 gold zones. During the summer of 2012, 150 drill core samples were selected from 7 ore zones (3 base metal zones and 4 gold zones) to better establish the mineralogical and trace element associations of the different ore types. Four main gold-rich ore types and metal associations have been identified: Type 1 massive sulfide (Au-Zn±Cu±Ag), Type 2 carbonate-chlorite-schist (Ag-Au±Pb±Zn), Type 3 semi-massive chalcopyrite (Au-Cu), and Type 4 low-sulfide ore (Au±Ag). Type 1 massive sulfide ore (average 7.5 ppm Au, 46.9 ppm Ag, 1.3% Cu, 8.5% Zn, 0.3% Pb, n= 34 samples) comprises mainly pyrite with interstitial sphalerite and minor calcite/dolomite. Chalcopyrite is present but discontinuous, and pyrrhotite occurs locally. Gahnite also occurs with sphalerite. Type 2 mineralization (14.8 ppm Au, 90.2 ppm Ag, 0.6% Cu, 2.2% Zn, 1.0% Pb, n=34) contains abundant disseminated galena and less common sphalerite in a chlorite and carbonate matrix; Cu-Fe sulfides are present locally but never the dominant sulfides. Type 3 semi-massive chalcopyrite ore (12.1 ppm Au, 37.4 ppm Ag, 2.8% Cu, 0.8% Zn, <0.01% Pb, n=27) occurs with quartz, biotite, and anthophyllite and commonly contains coarse garnet and staurolite. Type 1 mineralization is restricted to three upper lenses (#40, 10 and 20). Type 2 mineralization (#21 and 25 lenses) occurs at intermediate depths. Type 3 mineralization is found at the base of lens #27, which is the deepest known ore lens. Type 4 low-sulfide ore (19 ppm Au, 57.2 ppm Ag, 1.3% Cu, 0.6% Zn, 0.1% Pb, n=19) forms isolated zones within lenses #21, #25 and #27, in which gold occurs as rounded grains of electrum associated with tetrahedrite and galena. Intensive recrystallization and annealing is seen in all ore types. Polyphase deformation (F1 through F4) and amphibolite facies metamorphism have had a major impact on the ore-hosting assemblages. A goal of the present study is to determine the paragenesis of the precious metals in the different ore zones and, in particular, how hydrothermal alteration and metamorphism have influenced the distribution of gold in the deposit.

Type de document: Document issu d'une conférence ou d'un atelier
Mots-clés libres: minerai; gisement de sulfure; or; Manitoba
Centre: Centre Eau Terre Environnement
Date de dépôt: 19 nov. 2020 20:11
Dernière modification: 19 nov. 2020 20:11
URI: http://espace.inrs.ca/id/eprint/4050

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