Geologic and Structural Setting of Gold Mineralization in the Kirkland Lake-Larder Lake Gold Belt, Ontario

Abstract

The Kirkland Lake-Larder Lake gold belt includes the giant Kirkland Lake and world-class Kerr-Addison-Chesterville gold deposits, along with several smaller deposits and occurrences. It corresponds to an east-trending band of Timiskaming clastic and volcanic rocks that unconformably overlie older volcanic assemblages in the southern Abitibi greenstone belt of the Archean Superior province. The gold belt is bounded to the south by the Larder Lake-Cadillac deformation zone, which roughly follows the contact between the younger Timiskaming rocks and the older volcanic units. Three generations of fabrics formed during post-Timiskaming regional deformation (D2, D3, and D4) of the belt. North-south shortening during D2 produced a penetrative, generally east-striking, steeply dipping, S2 foliation, and an east-plunging, L2 stretching lineation. S2 is most intense within the syn-D2 Larder Lake-Cadillac deformation zone and its northeast-trending splay, the Upper Canada deformation zone. The D2 structures are overprinted by a north-trending crenulation cleavage S3, which formed during east-west D3 shortening across the belt. A northeast-trending regional S4 foliation associated with Z-shaped F4 folds and overprinting both S2 and S3 formed during northwest-southeast D4 shortening. Gold mineralization is localized along the Larder Lake-Cadillac deformation zone (Anoki and McBean deposits), the Upper Canada deformation zone (Upper Canada deposit), and the brittle Kirkland Lake fault and ‘04 Break (Kirkland Lake deposit). The Upper Canada, McBean, and Anoki deposits formed during D2, and, along with Kerr-Addison-Chesterville, Omega, and Cheminis deposits, are probably related to a regionally extensive hydrothermal system associated with the Larder Lake-Cadillac deformation zone. The sulfide-poor gold- and telluride-bearing quartz veins of the Kirkland Lake deposit are interpreted to have been emplaced during D4, synchronous with reverse-dextral movement along the ore-controlling brittle Kirkland Lake fault. The Kirkland Lake mineralization has a distinct metal signature (Te>Au, Mo, Pb, Ag, high Au/Ag, low As) and probably represents a separate hydrothermal system linked to a deep magmatic (alkalic) fluid source and unrelated to mineralization along the syn-D2 deformation zones.