Découverte d’une faille dans une zone de cisaillement : levé magnétique et étude de carottes de forage de la propriété du lac Valentine, à Terre-Neuve, Canada
DOI :
https://doi.org/10.4138/atlgeo.2023.008Résumé
La propriété du lac Valentine dans le sud-ouest de Terre-Neuve abrite cinq gîtes aurifères connus sur une distance de 20 km le long d’un axe du nord-est au sud-ouest et on anticipe qu’elle constituera l’emplacement de la plus vaste mine d’or au Canada atlantique. La propriété recèle des filons de quartz-tourmaline-pyrite orogéniques régis par la structure le long ou à proximité de la zone de cisaillement du lac Valentine. La minéralisation est principalement présente sur le flanc nord-ouest de la zone de cisaillement dans des roches intrusives et elle est rare dans le conglomérat sur le flanc méridional. Le secteur renferme de nombreux dykes mafiques, qui sont bien apparents lorsqu’on effectue un levé magnétique en raison de leur teneur magnétique. Ces dykes, à l’instar de la minéralisation, se manifestent surtout dans les roches intrusives et l’axe essentiellement subparallèles à la zone de cisaillement, et ils peuvent par conséquent faciliter l’élucidation de la structure. Pour circonscrire l’emplacement de la zone de cisaillement (et en conséquence la région minéralisée) dans un secteur où l’on soupçonnait un rejet, on a réalisé un levé magnétique détaillé suivant une grille de 200 m sur 300 constituée de 16 lignes. Les données recueillies ont permis la création et le traitement de cartes de l’intensité magnétique. On a alors repéré une région où la configuration des crêtes magnétiques linéaires s’estompe et semble prendre fin près du rejet soupçonné. Les données, conjuguées à l’information obtenue de carottes de forage, nous amènent à interpréter l’endroit comme un rejet vertical de la zone de cisaillement. L’affaiblissement de l’intensité magnétique est possiblement dû à une altération ou un amincissement des dykes mafiques près de la faille.
Références
Dentith, M. and Mudge, S.T. 2014. Geophysics for the mineral exploration geoscientist. Cambridge University Press, 438 p. https://doi.org/10.1017/CBO9781139024358
Evans, D.T.W. and Kean, B.F. 2002. The Victoria Lake Supergroup, central Newfoundland – its definition, setting and volcanogenic massive sulphide mineralization. Newfoundland and Labrador Department of Mines and Energy, Geological Survey. Open File NFLD/2790, 68 p.
Evans, D.T.W., Kean, B.F., and Dunning, G.R. 1990. Geological studies, Victoria Lake Group, central Newfoundland. In Current Research, Newfoundland Department of Mines and Energy, Geological Survey Branch, Report 90-1, pp. 135–144.
Flanagan, M. 2021. Magnetics study within the Valentine Gold Property, Newfoundland. Unpublished B.Sc. Honours thesis, Memorial University of Newfoundland and Labrador, St. John’s, Newfoundland and Labrador, Canada 73 p.
Geomagnetism Canada 2020. Magnetic declination calculator. URL <https://www.geomag.nrcan.gc.ca/calc/calc-en.php> 14 October 2020.
Guay, M., Riopel, J., Carrier, A., Dunsworth, S., Allou, B., Trudel, D., St-Jean, E., D’Amours, I., and Letourneau, O. 2007. Helicopter-borne magnetic, gamma-ray spectrometry and VLF geophysical survey NTS map sheets 12A/06 and 12A/07. Unpublished data acquisition report, Valentine Lake gold project, 377 p. URL <https://gis.geosurv.gov.nl.ca/geofilePDFS/ReceivedBatch46/012A_1447_Part2.pdf> 08 July 2021.
Honsberger, I.W., Bleeker, W., Kamo, S.L., Sandeman, H.A.I., Evans, D.T.W., Rogers, N., van Staal, C.R., and Dunning, G.R. 2022. Latest Silurian syntectonic sedimentation and magmatism and Early Devonian orogenic gold mineralization, central Newfoundland Appalachians, Canada: Setting, structure, lithogeochemistry, and high-precision U-Pb geochronology. Geological Society of America Bulletin, 134, pp. 2933–2957. https://doi.org/10.1130/B36083.1
Kruse, S. 2020. Structural analysis of the Valentine Gold Project. Marathon Gold Corp., Unpublished internal report Project#: 20-46-F. Terrane Geoscience. 46 p.
Marathon Gold 2021. Technical report & feasibility study on the Valentine Gold Project. URL <https://marathon-gold.com/site/uploads/2021/04/Valentine-Gold-43-101_FS-Report_FINAL_Apr23_R2.pdf> 08 July 2021
Marathon Gold 2022. Valentine Gold Project, deposits. URL <https://marathon-gold.com/valentine-gold-project/deposits/> 1 February 2022.
Melanson, D. and Parks, C. 2019. Marathon Gold: Valentine Mine. Final Report on Lidar Survey. Aethon Aerial Solutions, Burlington, ON. Marathon Gold unpublished internal report, 10 p.
Runyon, S.E., Seedorff, E., Barton, M.D., Steele-MacInnis, M., Lecumberri-Sanchez, P., and Mazdab, F.K. 2019. Coarse muscovite veins and alteration in porphyry systems, Ore Geology Reviews 113, pp. 1–32. https://doi.org/10.1016/j.oregeorev.2019.103045
Szitkar, F., Dyment, J., Choi, Y., and Fouquet, Y. 2014. What causes low magnetization at basalt-hosted hydrothermal sites? Insights from inactive site Krasnov (MAR 16°38′N). Geochemistry, Geophysics, Geosystems 15, pp. 1441–1451. https://doi.org/10.1002/2014GC005284
Terraplus. 2020. Magnetic Susceptibility Meters URL <https://terraplus.ca/product-details/magnetic-susceptibility-meters> 24 September 2020.
Tettelaar, T. and Dunsworth, S. 2015. Supplementary assessment report of diamond core drilling, prospecting, trenching, channel sampling, trench rehabilitation, geological trench mapping, line cutting, ground magnetometer survey, environmental studies, and road repair & maintenance, Valentine Lake Property, Central Newfoundland, NTS 12A/06. Unpublished data acquisition report, 981 p. URL <https://gis.geosurv.gov.nl.ca/geofilePDFS/Batch2019/012A_1761.pdf> 24 September 2020.
Tettelaar, T. and Dunsworth, S. 2016. Supplementary assessment report of diamond core drilling, line cutting, ground magnetometer survey, and road repair & maintenance, Valentine Lake Property, Central Newfoundland, NTS 12A/06. Unpublished data acquisition report, 160 p. URL <https://gis.geosurv.gov.nl.ca/geofilePDFS/Batch2019/012A_1805.pdf> 24 September 2020.
Valverde-Vaquero, P., and van Staal, C.R. 2002. Geology and magnetic anomalies of the Exploits–Meelpaeg boundary zone in the Victoria Lake area (central Newfoundland): regional implications. Newfoundland Department of Mines and Energy Geological Survey, Report 02-1, pp. 197–209.
Van Staal, C. and Valverde-Vaquero, P. 2001. Relationships between the Dunnage-Gander zones in the Victoria Lake-Peter Strides Pond area. Newfoundland Department of Mines and Energy Geological Survey, Report 2001-1, pp. 1–9.
Van Staal, C., Valverde-Vaquero, P., Zagorevski, A., Rogers, N., Lissenberg, C., McNicoll, V. 2005. Geology, Victoria Lake, Newfoundland and Labrador. Geological Survey of Canada, Open File 1667, scale 1:50 000. https://doi.org/10.4095/221287
Van Staal, C.R., Whalen, J.B., Valverde-Vaquero, P., Zagorevski, A., and Rogers, N. 2009. Pre-Carboniferous, episodic accretion-related, orogenesis along the Laurentian margin of the northern Appalachians. Geological Society, London, Special Publications, 327, pp. 271–316. https://doi.10.1144/SP327.13
White, S.E. and Waldron, J.W.F. 2022. Along-strike variations in the deformed Laurentian margin in the Northern Appalachians: Role of inherited margin geometry and colliding arcs, Earth Science Reviews 226. https://doi.org/10.1016/j.earscirev.2022.103931
Williams, H. 1979. Appalachian Orogen in Canada. Canadian Journal of Earth Sciences, 16, pp. 792–807. https://doi.org/10.1139/e79-070
Williams, H., Colman-Sadd, S.P., and Swinden, H.S. 1988. Tectonic-stratigraphic subdivisions of central Newfoundland. In Current Research, Part B, Geological Survey of Canada, Paper 88-JB, pp. 91–98. https://doi.org/10.4095/122425
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