Summary:
Syntectonic plutons, intruded near regional-scale shear zones, became the focus of exploration and research due to their close spatial relationships with some gold deposits. Mineralizing fluids are interpreted to have been derived from the plutons during emplacement. The Fenn–Gib Deposit is best represented by this model.
Project Geology
The Project is underlain by the dominantly volcanic Kidd-Munro assemblage to the north and the dominantly sedimentary Hoyle assemblage to the south. The two sequences are juxtaposed along the Contact Fault, an east-west to southeast trending shear zone, which is interpreted to be a splay of the Porcupine-Destor Fault Zone. Within the deposit, the Contact Fault is characterized by brittle deformation accompanied by intense carbonatization and silicification. Rocks from both assemblages were intruded by a variety of late intrusive rock including syenite and granitoid plugs and dykes, lamprophyre dykes, and diabase dykes. A 3 km-long, by 100 to 200 m-wide mafic intrusive complex intrudes the Kidd-Munro Assemblage at or near its southern contact.
All lithologic units in and adjacent to the Deformation Zone are moderately to intensely altered. This alteration persists for a distance north and south of the fault, outlining a major alteration halo at least 2 km long and 500 m wide. A variety of alteration styles occur within the broad alteration halo, including silicification, albitization, potash metasomatism, carbonatization, sericitization, chloritization, and hematization. Fuchsite (Mariposite) can occur within the Deformation Zone. Sulphide mineralization, mainly pyrite, occurs as disseminations and fracture fillings in concentrations ranging from trace to 20% in association with the more strongly altered areas. Gold is commonly associated with the sulphide mineralization, especially in areas of coincident silicification and albitization.
Several styles of gold mineralization have been identified within the Project area. The most common style consists of quartz-carbonate veins, stringers, and breccias hosted within intensely altered volcanic rocks and granitoid intrusions (i.e., the Main Zone and Deformation Zone). A second style is characterized by gold associated with intensely altered sediments, containing variable amounts of fine crystalline pyrite within and in the hanging wall to the Deformation Zone. A third style involves gold mineralization related to alteration, shearing, and sulphide mineralization within north-northeast-trending structures including the Main Zone, Deformation Zone, and Footwall Zone.
Mineralization
Significant concentrations of gold mineralization on the Project primarily occur within two zones, the Main Zone and the Deformation Zone. The third zone, Footwall Zone, also contains gold mineralization and is approximately 100 m north of the Main Zone.
The Main Zone is a broad zone (average width of 100 m) of disseminated gold mineralization up to 500 m along strike, with grades for gold between 0.50 and 3.00 g/t Au. Massive, pillowed, and variolitic basalts crop out and can be seen in diamond drill core from holes collared near Highway 101. Hydrothermally altered variolitic basalts are the principal hosts of the Main Zone mineralization. These basalts were affected by pervasive and vein silicification, carbonatization, albitization, pervasive but weak hematization, and vein sericitization. Syenite and lamprophyre dykes intruded the basalts and are locally mineralized. Pyrite is the main sulphide mineral and occurs as disseminations and in veins, locally up to 50%, over narrow intervals (average 5% to 10%).
The Deformation Zone contains narrower and higher-grade intersections associated with altered sediments, intermediate dykes, and grey syenite. Gold mineralization is associated with pyrite either in quartz-healed breccias or as very fine disseminations. The Contact Fault has been interpreted to have acted as a channel for gold-bearing hydrothermal fluids and is host to the Deformation Zone and the southern boundary of the Main Zone. The Deformation Zone mineralization has been defined for approximately 2.0 km along strike (width ranges from 50 to 250 m) but remains open along strike and open at depth.
The Footwall Zone's structural and mineralized corridor strikes in a north easterly direction, and drilling has intercepted the zone over a strike length of approximately 500 m (average width 250 m) and a vertical depth of about 600 m below surface (open in all directions). The Footwall Zone consists of multiple mineralized zones hosted primarily in the footwall mafic volcanic assemblage, with a steep northerly dip. Mineralization consists of bleached, buff-altered (silica-albite-sericite-carbonate alteration), pillowed mafic volcanic with pyrite ranging from 2% to over 20%.