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The Canadian Malartic low-grade bulk tonnage gold mine (total production and reserves of 303.3 t or 10.7 Moz at 0.97 g/t) is located in the Archean Abitibi greenstone belt, immediately south of the crustal-scale Larder Lake-Cadillac fault zone. The deposit is predominantly hosted in clastic metasedimentary rocks of the Pontiac Group and, to a lesser extent, in subalkaline porphyritic quartz monzodiorite and granodiorite. The quartz monzodiorite and granodiorite yielded syn-Timiskaming U-Pb ID-TIMS zircon ages of 2677.8 ± 1.5 and 2678.4 ± 1.7 Ma, respectively. The ore, which is characterized by a Au-Te-W-S-Bi-Ag ± Pb ± Mo metallic signature, mainly consists of quartz-carbonate vein stockworks and replacement zones with disseminated pyrite. The ore zones are dominantly oriented subparallel to a NW-striking S2 foliation and to the E-striking and S-dipping Sladen fault, thus forming NW-SE and E-W mineralized trends. In both the sedimentary rocks and the quartz monzodiorite, the proximal and distal alteration zones are characterized by the presence of calcite and ferroan dolomite, respectively. In the sedimentary rocks, the ore zones show a wide distal biotite alteration halo with proximal assemblages made up of albite and/or microcline with pyrite. The quartz monzodiorite comprises a distal hematite-bearing alteration zone that is overprinted by proximal microcline + albite + quartz + pyrite replacement zones. The metallic signature of the ore, the presence of mineralized stockworks, the potassic alteration (biotite/microcline), and an association with ca. 2678 Ma porphyritic intrusions suggest the possibility of an early, syn-Timiskaming magmatic-hydrothermal auriferous event in the area. However, this study indicates that gold mineralization and its distribution at Canadian Malartic are largely controlled by D2 deformation and related features such as faults, shears, and high-strain zones. Of particular importance are the S2 cleavage developed in the hinge zone of F2 folds, and the Sladen fault. Molybdenite from high-grade ore yielded a Re-Os age of 2664 ± 11 Ma that is compatible with a syn-D2 timing for the bulk of the mineralization. The main characteristics of the Canadian Malartic deposit are thus best explained by a syndeformational event (D2; ca. 2670–2660 Ma) potentially superimposed onto a gold-bearing magmatic/hydrothermal intrusion-related system associated with Timiskaming-age porphyritic intrusions emplaced along the crustal-scale Larder Lake-Cadillac fault zone.

The Canadian Malartic Mine consists of an Archean low-grade bulk tonnage gold deposit (reserves of 10.7 Moz Au @ 0.97 g/t) hosted by clastic metasedimentary rocks of the Pontiac Group and subalkaline porphyritic quartz monzodiorite and granodiorite located immediately south of the Larder Lake-Cadillac Fault Zone. The quartz monzodiorite and granodiorite yield syn-Timiskaming U-Pb zircon ages of 2677 and 2678 Ma, respectively. Gold mineralization is characterized by zones of quartz-carbonate vein stockwork and disseminated pyrite with a Au-Te-W-S-Bi-Ag}Pb}Mo metallic signature. These ore zones are dominantly oriented subparallel to the northwest-striking S2 foliation and to the east-striking and south-dipping Sladen Fault, thus forming northwest-southeast and east-west mineralized trends. Molybdenite from highgrade ore yielded a Re-Os age of ca. 2664 Ma. In both the sedimentary rocks and the quartz monzodiorite, the proximal and distal alteration zones are characterized by the presence of calcite and ferroan dolomite, respectively. In the sedimentary rocks, the ore zones show a wide distal biotite alteration halo with proximal assemblages comprising albite and/or microcline. The quartz monzodiorite comprises a distal hematitic alteration zone that is overprinted by proximal microcline + albite + quartz replacement zones. This study suggests that at Canadian Malartic deposit, the gold mineralization and its distribution are largely controlled by D2 faults, shear and high-strain zones developed in the hinge zone of F2 folds, and by the Sladen Fault. A ?2678 Ma syn-Timiskaming magmatic-hydrothermal early phase of gold mineralization can be inferred by the metallic signature or the ore, the presence of mineralized stockworks, the potassic alteration (biotite/microcline), and association with porphyritic intrusions. The main characteristics of the Canadian Malartic deposit is thus best explained by syn-D2 deformation gold (ca. 2670-2660 Ma) superimposed onto, or remobilized from, a gold-bearing magmatic/hydrothermal system related to Timiskaming-age porphyritic intrusions emplaced along a major fertile fault zone.

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Pyrite efficiently incorporates many key metals during progressive precipitation and thus records the chemical evolution of fluids from which it was deposited. To reveal this information, a new LA-ICP-MS mapping procedure has been developed to allow generation of 2-D trace element concentration maps of minerals in petrographic section. The technique has been applied to pyrite-/pyrrhotite-bearing Au ores from three major gold deposits. Canadian Malartic is a low-grade bulk-tonnage deposit, which is located immediately south of the Larder Lake-Cadillac Fault Zone. It is hosted mainly by clastic metasedimentary rocks of the Pontiac Group, as well as by porphyritic quartz monzodiorite and granodiorite. Textural evidence and elemental mapping have revealed five types of pyrite. The pre-mineralization pyrite (py1) is likely diagenetic pyrite, with high Co, As, and Se, and low Ni, Te, Sb, Bi, and Pb. Gold-bearing pyrite 2, 3 and 4 (py2-py4) has covariant Co and Ni, high Au, Ag, Te, Bi, and Pb, and generally contains abundant potassic inclusions. Postmineralization pyrite (py5) has high Co and Ni but is low in other metals. Pyrite from the ore zones distributed along the Sladen fault zone shows evidence of post-precipitation metal enrichment in fractures associated with Ca metasomatism. Though the elemental maps cannot unequivocally discriminate the deposit type, pyrite chemistry is consistent with a two-stage model comprising early syn-pyrite Au mineralization associated with potassium alteration and a later post-pyrite upgrading associated with Ca metasomatism. The Côté Gold deposit is hosted by the Chester intrusive complex, a high-level, multi-phase synvolcanic intrusion composed of tonalite and diorite. Nickel, As, Sb, and Pb are generally relatively depleted in the cores and enriched in the rims of the pyrite grains, whereas Te and Ag are relatively enriched in the cores and depleted in the rims. Arsenopyrite grains have high Co, Ni, Se, Sb, and Te, but low Ag, Pb, and Bi. Gold is depleted both in pyrite and arsenopyrite, except locally in fractures, but is enriched in silicate minerals, possibly as nanoparticles, suggesting that gold mineralization is related to a hydrothermal event post-dating pyrite precipitation. The Musselwhite deposit is a banded iron formation-hosted lode gold deposit in a sequence of volcanic and sedimentary rocks that include carbonaceous argillite locally hosting diagenetic pyrite nodules. Cobalt, Cu, Ni, Se, As, Ag, Sb, Te, Au, Tl, Pb, and Bi are enriched in the nodules but are depleted in recrystallized pyrite and pyrrhotite. Element and Pb-isotope maps are consistent with a model whereby at least some of the ore gold was derived from fluids that garnered Au liberated via metamorphic recrystallization of auriferous diagenetic pyrite and, probably, carbonaceous material in local argillite. The elemental maps show that gold has multiple sources. The Musselwhite deposit provides evidence for local pyritic carbonaceous sedimentary rocks as one of the possible sources of Au. The Canadian Malartic and Côté deposits have a strong association with magmatic hydrothermal activity, although additional sources of Au may also have been important.