The Larder Lake - Cadillac deformation zone (LLCDZ) is one of two major, auriferous, deformation zones in the southern Abitibi subprovince of the Archean Superior Province. It hosts the Cheminis and the giant Kerr Addison - Chesterville deposits within a strongly deformed band of Fe-rich tholeiitic basalt and komatiite of the Larder Lake Group (ca. 2705 Ma). The latter is bounded on both sides by younger, less deformed, Timiskaming turbidites (2674-2670 Ma). The earliest deformation features are F-1 folds affecting the Timiskaming rocks, which formed either during D-1 extensional faulting or during early D-2 north-south shortening related to the opening and closure, respectively, of the Timiskaming basin. Continued shortening during D-2 imbricated the older volcanic rocks and turbidites and produced regional F-2 folds with an axial planar S-2 cleavage. D-2 deformation was partitioned into the weaker band of volcanic rocks, producing the strong S-2 foliation, L-2 stretching lineation, and south-side-up shear sense indicators, which characterize the LLCDZ. Gold is present in quartz-carbonate veins in deformed fuchsitic komatiites (carbonate ore) and turbiditic sandstone (sandstone-hosted ore), and in association with disseminated pyrite in altered Fe-rich tholeiitic basalts (flow ore). All host rocks underwent strong mass gains in CO2, S, K2O, Ba, As, and W, during sericitization, carbonatization, and sulphidation of the host rocks, suggesting that they interacted with the same hydrothermal fluids. Textural relationships between alteration minerals and S-2 cleavage indicate that mineralization is syn-cleavage. Thus, gold was deposited as hydrothermal fluids migrated upward along the LLCDZ during contractional, D-2 south-side-up shearing. The gold zones were subsequently modified during D-3 reactivation of the LLCDZ as a dextral transcurrent fault zone.
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