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Geology and hydrothermal alteration of the world-class Canadian Malartic gold deposit; genesis of an Archean stockwork-disseminated gold deposit in the Abitibi greenstone belt

Stephane De Souza, Benoit Dube, Vicki McNicoll, Celine Dupuis, Patrick Mercier-Langevin, Robert A. Creaser and Ingrid Kjarsgaard
Geology and hydrothermal alteration of the world-class Canadian Malartic gold deposit; genesis of an Archean stockwork-disseminated gold deposit in the Abitibi greenstone belt (in Archean base and precious metal deposits, southern Abitibi greenstone belt, Canada, Thomas Monecke (editor), Patrick Mercier-Langevin (editor) and Benoit Dube (editor))
Reviews in Economic Geology (January 2017) 19: 263-291

Abstract

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 + or - 1.5 and 2678.4 + or - 1.7 Ma, respectively. The ore, which is characterized by a Au-Te-W-S-Bi-Ag + or - Pb + or - 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 S (sub 2) 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 D (sub 2) deformation and related features such as faults, shears, and high-strain zones. Of particular importance are the S (sub 2) cleavage developed in the hinge zone of F (sub 2) folds, and the Sladen fault. Molybdenite from high-grade ore yielded a Re-Os age of 2664 + or - 11 Ma that is compatible with a syn-D (sub 2) timing for the bulk of the mineralization. The main characteristics of the Canadian Malartic deposit are thus best explained by a syndeformational event (D (sub 2) ; 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.


ISSN: 0741-0123
EISSN: 2374-443X
Serial Title: Reviews in Economic Geology
Serial Volume: 19
Title: Geology and hydrothermal alteration of the world-class Canadian Malartic gold deposit; genesis of an Archean stockwork-disseminated gold deposit in the Abitibi greenstone belt
Title: Archean base and precious metal deposits, southern Abitibi greenstone belt, Canada
Author(s): De Souza, StephaneDube, BenoitMcNicoll, VickiDupuis, CelineMercier-Langevin, PatrickCreaser, Robert A.Kjarsgaard, Ingrid
Author(s): Monecke, Thomaseditor
Author(s): Mercier-Langevin, Patrickeditor
Author(s): Dube, Benoiteditor
Affiliation: Geological Survey of Canada, Quebec City, QC, Canada
Affiliation: Colorado School of Mines, Department of Geology and Geological Engineering, Golden, CO, United States
Pages: 263-291
Published: 20170101
Text Language: English
Publisher: Society of Economic Geologists, Boulder, CO, United States
References: 79
Accession Number: 2022-008308
Categories: Economic geology, geology of ore depositsGeochronology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. geol. sketch maps
N48°02'60" - N48°10'00", W79°45'00" - W79°30'00"
Secondary Affiliation: University of Alberta, CAN, Canada
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2022, American Geosciences Institute.
Update Code: 202204
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