ARTICLE Expanding the size of multi-parameter metasomatic footprints in gold exploration: utilization of mafic dykes in the Canadian Malartic district, Québec, Canada Stéphane Perrouty 1,2 & Robert L. Linnen 2 & Michael C. Lesher 1 & Gema R. Olivo 3 & Stephen J. Piercey 4 & Nicolas Gaillard 5 & James R. Clark 5 & Randolph J. Enkin 6 Received: 13 December 2017 /Accepted: 23 July 2018 # Springer-Verlag GmbH Germany, part of Springer Nature 2018 Abstract Ore-forming hydrothermal fluids react differently with different country rocks, but few studies have applied this knowledge with the specific goal of expanding the size of hydrothermal footprints in mineral exploration. To develop this concept, 122 meta- morphosed mafic dykes from the world-class Canadian Malartic gold district (18.6 Moz Au) were sampled and analyzed for mineralogy, physical properties, and lithogeochemistry (partial and total digestion). The mafic dykes intrude mainly metasedimentary rocks, post-date D 1 deformation, and cross-cut early-D 2 quartz monzodiorite intrusions, but they were de- formed and altered during D 2 deformation, mineralization, and metamorphism. They can be subdivided into three groups: Group 1 dykes are least-altered, characterized by amphibole-rich regional metamorphic assemblages and distributed throughout the Pontiac Subprovince. Group 2 and 3 dykes underwent ore-related hydrothermal biotite–calcite–pyrite alteration and are associ- ated with density- and volume-adjusted concentration gains of over 100% in Au–W–Te–C–S–Ag–Cs–Mo–Cu–K–Rb–Se–U– Pb–Ba–F–Bi–Sn. They define a metasomatic footprint up to 6 km away from the deposit toward the SE and up to 2 km away from the deposit toward the SW. Fifty-eight variables that define halos around the Canadian Malartic deposit have been identified and integrated using principal component analysis. PC1 explains 30% of the variance, separates least-mobile elements from ore- related elements, and is interpreted to reflect the ore-forming alteration process. PC2 and PC3 represent igneous processes. PC4 highlights the calcite–pyrite and biotite alteration. Spatial variations of the modal abundances of amphibole, biotite, calcite, and pyrite are the simplest expression of the metasomatic footprint, and they can easily be documented during exploration at the camp scale. Keywords Abitibi . Pontiac Subprovince . Gold deposits . XRD cluster analysis . Aqua regia digestion . Principal component analysis Editorial handling: K. Kelley Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00126-018-0829-x) contains supplementary material, which is available to authorized users. * Stéphane Perrouty SPerrouty@laurentian.ca 1 Mineral Exploration Research Centre, Harquail School of Earth Sciences, Goodman School of Mines, Laurentian University, 935 Ramsey Lake Road, Sudbury, ON P3E 2C6, Canada 2 Department of Earth Sciences, Western University, 1151 Richmond Street N, London, ON N6A 5B7, Canada 3 Department of Geological Sciences and Geological Engineering, Queen’ s University, Kingston, ON K7L 3N6, Canada 4 Department of Earth Sciences, Memorial University of Newfoundland, 9 Arctic Avenue, St. John’ s, NL A1B 3X5, Canada 5 Department of Earth and Planetary Sciences, McGill University, 3450 University Street, Montréal, QC H3A 0E8, Canada 6 Geological Survey of Canada—Pacific, 9860 West Saanich Road, POB 6000, Sidney, BC V8L 4B2, Canada Mineralium Deposita https://doi.org/10.1007/s00126-018-0829-x