Structural setting of the Young-Davidson syenite-hosted gold deposit in the Western Cadillac-Larder Lake Deformation Zone, Abitibi Greenstone Belt, Superior Province, Ontario

Within the southern Abitibi greenstone belt of the Superior Province, intrusion-related, in particular syenite-hosted gold deposits represent a significant type that is poorly understood. Whether the gold mineralization is genetically linked to the syenite intrusions (as in a magmatic model) or structurally associated with the development of subsequent shear zones remains very controversial. Our new structural data show that the multiply deformed Young-Davidson gold deposit and its surrounding Matachewan area occur along the western extension of the Cadillac - Larder Lake Deformation Zone (CLLDZ), a tectonically and economically important crustal-scale deformation zone in the southern Abitibi greenstone belt. Four generations (D-1-D-4) of deformation are recognized. The first part of the D-1 deformation (D-1a) records a NE-SW-oriented shortening and resulted in regional upright folding without penetrative foliation, whereas the subsequent D-1b generates regional penetrative foliations and top-to-NE reverse faults. D-2 occurs during a NW-SE-oriented shortening and produces asymmetric folds, oblique-slip thrusts and dextral strike-slip shear zones. D-3 semi-brittle deformation refolds the D-1 and D-2 fabrics, whereas the latest D-4 sinistral fault records a Paleoproterozoic brittle deformation. The Young-Davidson deposit is a lode-gold deposit that at least in part was structurally controlled. It is associated with the development of the CLLDZ and hosted in a syenite. Four main generations of veins are identified in the syenite. VI veins are characterized by folded and boudinaged quartz-ankerite veins, V-2 veins are represented by folded or en echelon quartz-pyrite veinlets, V-3 veins are comprised of en echelon quartz-carbonate veins with sulfide minerals, and V-4 veins consist of planar carbonate-quartz veins and minor hematite. Petrological studies reveal that the major phase of gold mineralization is associated with the V-2 veins and partially with the V-3 veins. Gold mineralization and emplacement of the associated veins appear to have occurred during regional D-1b NE-SW-oriented shortening and top-to-NE shearing and the syenite acted as a mechanical trap due to competency contrast to the wall rock (C) 2014 Elsevier B.V. All rights reserved.