SEISMIC FAILURE ALONG THE CADILLAC-LARDER LAKE FAULT ZONE AND ITS IMPLICATIONS ON THE DISTRIBUTION OF OROGENIC GOLD DEPOSITS

Orogenic gold deposits are distributed along large-scale fault zones in clusters. Processes responsible for concentrations of mineralizing fluids in local sectors result from complex interaction between hydrothermalism, seismicity and structural segmentation. The well-documented Cadillac-Larder Lake Fault Zone (CLLFZ) in the Archean Abitibi subprovince and associated gold deposits offer an ideal ground for testing static stress modelling of seismic activity along the first order metalotect in order to explain heterogenous location of mineralization at a regional scale. Two dimensions modelling using UDEC code allows mapping prospective areas. The model is calibrated using current geological and structural knowledge of the CLLFZ and southern Abitibi. Several rheological parameters (rock distribution, lesser order structures and orientation of preferential failure plan) and seismic doublets sequences are evaluated and validated by using the models’ ability to predict the actual locations of known gold deposits. The regional geometry of Rouyn and Malartic major goldfields is adequately explained by recurrent ruptures along the optimally-oriented and perfectly linear Joannes segment, abutting against the Davidson Fault to the west and a bend of the CLLFZ to the east. In the Val d’Or camp, the presence of the Bourlamaque goldfield at distance from the main fault is explained by doublet seisms along two subsidiary structures. CLLFZ structurally segmented geometry governs ruptures along 30–40 km long seismic panels, generating typical coseismic damage areas where failure conditions are put to critical. This induces intensive and localised microseismic activity temporary enhancing permeability along critical fractures networks, which form recurrent pathways for hydrothermal drainage and iterative gold deposition. Integration of regional geological context improve model validation and refined prospective areas for gold exploration.