Summary:
The gold mineralization at the Mine exhibits features analogous to mesothermal or “orogenic” gold deposits typified by Archean deposits of the Abitibi region, Canada. Features characteristic of the gold mineralization at the Mine include:
• A strong spatial association to large scale shear zones;
• Relative late timing during active compressional deformation;
• A strong spatial association with large scale shear zones;
• Formed during greenschist metamorphic conditions;
• Association with a propylitic-phyllic alteration assemblages; and
• Principally hosted in quartz-ankerite-pyrite veining.
Gold mineralization at Aurora is divided into four main mineralized zones; Rory’s Knoll, East Walcott and Walcott Hill, Mad Kiss and Mad Kiss West, and Aleck Hill and Aleck Hill North.
All the deposits display an association of gold mineralization with quartz veining and pyrite, locally as much as 10%. The auriferous veins developed relatively late in the deformational history and occur as brittle stockworks in more competent host rocks, e.g., Rory’s Knoll diorite and lesser quartz-feldspar porphyry dikes, and as foliation parallel, ribbon-like veins that vary in width from a few centimetres to rarely up to one to two metres wide.
At least three major generations of veining have been observed:
• Early quartz carbonate veins which are typically foliation parallel and folded or truncated.
• Brittle extensional arrays and stockworks – quartz-pyrite +/- ankerite, associated with mineralization.
• Late stage barren extensional quartz-calcite veins.
Coarse visible gold occurs in quartz-bearing veins and in pyrite-rich fractures. Gold-bearing structures have undergone minor post-formation strain. Vein selvages display sericite-iron carbonate hydrothermal alteration.
Rory’s Knoll
Rory’s Knoll is the principal gold deposit at Aurora. The deposit is entirely hosted by a distinctive, highly altered diorite pipe.
The host diorite extends approximately 250 m along a trend of 325º, plunges approximately 70° northwest. The mineralization lies in a segment approximately 180 m by 120 m in plan view and is mineralized down-plunge to over greater than 2.0 km below surface.
Mineralization is associated with disseminated pyrite and quartz veins, which display a timing that is structurally late and likely syn-peak to post-peak metamorphism. Quartz is the primary constituent of veins, with lesser carbonate and sulphide minerals. The veins typically occur as extensional sets or as breccia style erratic veins and stockwork zones.
Minor accessory albite, chlorite, white mica, tourmaline, and scheelite can accompany the veins. Carbonates include calcite, dolomite, and ankerite. Gold mineralization at Rory’s Knoll is associated with pyrite, and lesser chalcopyrite, sphalerite, and molybdenite. Argentite, native silver, and bornite have been noted in polished section. Gold is usually associated with sulphide minerals but can occur as free gold.
East Walcott and Walcott Hill
East Walcott is hosted by mafic volcanoclastic sediments and is located approximately 60 m southwest of the main Rory’s Knoll diorite pipe. The East Walcott zone consists of a series of tight fold closures over an area measuring approximately 100 m by 100 m in plan.
The geometry of East Walcott is controlled by the steep northwest plunging hinge line of fold
closures, which have a similar orientation to the Rory’s Knoll stock.
The style of mineralization is similar to Rory’s Knoll, hosted by stockwork zones and brecciated quartz-ankerite-pyrite veins in fold hinges. The highly foliated limbs also host narrow planar zones of layer parallel laminated veins.
The Walcott Hill deposit is located approximately 150 m west of East Walcott and extends southwest to over a distance of approximately 200 m. A number of historic adits, dating back to the 1940s, totalling approximately 327 m, were mined at Walcott Hill.
Mad Kiss and Area
The Mad Kiss deposit is located approximately 500 m south-southwest of the Rory’s Knoll deposit. The mineralization occurs as extensional and foliation-parallel quartz-ankerite veining hosted by a foliated quartz-feldspar porphyry dike. The central portion of the dike is up to 300 m in length and varies in width from two to fifteen metres. The main body, on which the pit is centred, strikes 240° azimuth and dips approximately 70° northwest.
Mineralization is currently understood to be hosted within three separate mineralized shoots, which are segments of the porphyry that is offset across high strain zones. Mineralization has been intersected by drilling to a depth of approximately 700 m below surface.