Summary:
The Bell Creek properties are underlain by carbonate altered, greenschist facies Archean-aged, metavolcanic and clastic metasedimentary rock. The metavolcanic portion of the stratigraphy represents the lower portion of the Tisdale Assemblage (Brisbin, 1997; Pyke, 1982). The Krist Formation is absent from the Property (Berger, 1998). The clastic metasedimentary rocks belong to the Porcupine assemblage. Lithologies generally strike east-west, to west-northwest, and are steeply dipping.
Regionally, gold bearing structures most commonly form in relatively competent volcanic rocks intruded by felsic porphyry stocks and dykes prior to the deposition of the Timiskaming Assemblage sedimentary rocks. Porphyries dating from 2691 ± 3 Ma to 2688 ± 2 Ma intruded the already folded and faulted greenstone sequences and initiated the mesothermal systems with the formation of associated albitites. Observations of pyrrhotite and gold-mineralized clasts within Timiskaming conglomerates at both the Pamour and the Dome mines, located approximately 5km southeast and 10km south-southwest of the Property respectively, suggest a prolonged gold deposition event from the creation of the steep south dipping DPF zone up to the latest episode of crustal stabilization (Butler, 2008).
Berger (1998) describes the gold mineralization in the Bell Creek area as occurring along selvages of quartz veins and wall rocks, in stylolitic fractures in quartz veins, in fine grained pyrite and pyrrhotite, and in association with amorphous carbon. High grade gold mineralization occurs mostly as replacement style pyrite and pyrrhotite mineralization in the wall rock of quartz veins located within alteration zones and sometimes as free gold within these quartz veins. The alteration zones are characterized by carbonate, graphitic and amorphous carbon, fine grained pyrite, sericite, and/or paragonite and are enriched in Au, arsenic (“As”), bismuth, and tungsten.
The Bell Creek mineralization differs in style from many deposits in the area in being composed largely of disseminated, replacement style pyrite-pyrrhotite-related mineralization. Slightly younger gold-bearing quartz veins may be present but are not predominant. This style of mineralization occurs in the deeper parts of the Dome Mine and in the Rusk Zone at the Timmins West mine, but is more common to the east, in the Holloway-Holt McDermott area and at the Larder Lake, where pyritic mineralization is often termed “flow ore” (Rhys 2012).
The most significant gold mineralization at Bell Creek occurs in two lithostructural settings: a) near or along an ultramafic-to-mafic contact zones (the Bell Creek and West Zone), and b) within the mafic volcanics sequence (North Zones).
Bell Creek and West Zones
The Bell Creek and West Zones were discovered in 1980 while drill testing electromagnetic conductors and Induced Polarization (“IP”) anomalies. Kent (1990) describes the Bell Creek West Zone mineralization as occurring on or near the contact of the ultramafic metavolcanic and mafic fragmental metavolcanic rock units, with the latter as the preferred host. Mineralization consists of 2% to 10% pyrite, with accessory arsenopyrite, pyrrhotite, chalcopyrite, and minor quartz veins and veinlets. Approximately 90% of the gold is associated with the disseminated sulphides that occur in association with altered quartz-carbonate-sericite-sulphide zones that range from 0.5m to 7m in width. Lenses that are approximately 100m in length and 200m in vertical extent strike west-east and plunge steeply to the east.
Multiple mineralized zones are identified along a one km strike length of the mafic/ultramafic metavolcanic contact, which runs across the southern part of the mine. Active carbon occurs in some of the mineralized pods in the form of sheared graphitic interflow sediments. The presence of the active carbon has a deleterious effect on gold recovery; consequently, mining is not planned where this is encountered (Kent, 1990). Only a small portion of these zones were mined in the upper levels of the mine prior to 1992.
North Zones
The North Zones at Bell Creek were intersected in 1981 while targeting IP anomalies. The vein system consists of two main sub-parallel horizons, roughly 40 to 60m apart, historically referred to as the North A (“NA”) and North B (“NB”) zones. They occur within mafic volcanic rocks, approximately 200m north of an ultramafic contact and north of the Bell Creek headframe. Mineralization within the zones trends east west to west-northwest and dips steeply to the south or southwest. The mineralization is locally deflected as it intersects and exploits a 0.5 to 10 m wide band of carbonaceous interflow sediments. Mineralization forms vein-replacement networks along probable minor shear zones which are approximately parallel to the S3 foliation, although S3 locally trends slightly more northeasterly than the zone, especially where the zone rotates to the northwest (Rhys 2012).
Collectively, the North Zones extend up to 500m along strike, have an overall plunge which is steep to the east and has been traced continuously by drilling below 1,800m vertical depth, and remain open at depth. Overall plunge of the system is approximately parallel to the L4 lineation. Internally, steeper plunges to the west of thicker, high grade segments of the zone are apparent, forming more local, stope scale ore shoot plunges at bends in the structures (Rhys 2012).
The NA and NB Zones locally branch or break into strands which define multiple domains of gold mineralization and contain the majority of the total mineral resources.
North A Zone
The NA zone outcrops approximately 200m north of the Bell Creek headframe and consists of a marker quartz vein that varies from 0.1m to 2m in width with an associated alteration halo. Approximately 0.5m in average width, the vein parallels the regional schistosity and cross-cuts lithology. Bright green hydromuscovite occurs as fractures and slip coatings in the vein, with visible gold (“VG”) occurring with the mica. Brown tourmaline (dravite) is ubiquitous. The NA Zone can typically average 6 g/t Au to 10 g/t Au over 2 to 10 m widths. Adjacent to the quartz marker vein is a pale grey to buff colored altered zone (carbonate-albite+/-sericite – Hicks 1986) which contains 5% to 15% pyrite and pyrrhotite, with accessory chalcopyrite and arsenopyrite. Trace amounts of pentlandite, arsenopyrite and cobaltite have also been reported (Miller 2011). Up to 30% of the gold in the NA Zone occurs within the alteration halo, in discrete sulphide zones and in vein-brecciated wall rock zones that extend up to 5m from the margin of the core vein.
North B Zone
The NB zone occurs 40m to 60m further north and runs sub-parallel to the NA zone. The NB zone is predominantly hosted by the same interflow carbonaceous sediment which is locally transected by the NA zone. Brittle faulting exploits the carbonaceous unit, forming east-west to west-northwest trending fault surfaces with thin seams of black carbonaceous gouge that run parallel to the zone (Rhys 2012). Historically, portions of the wall rocks were thought to contain active carbon, which was determined to be detrimental to gold recovery (Kent, 1990). Overall, mineralization is narrower, quartz vein abundance is higher, and grades are lower than in the NA zone.