Summary:
The Bralorne deposit is considered to belong to a well-recognized group of deposits referred to as mesothermal, orogenic, or greenstone-hosted quartz-carbonate gold vein deposits.
The Property is situated within the Bridge River mining district in southwestern British Columbia. On the Property, the historical producing mines are hosted within the Bralorne-East Liza Complex. This consists of a structurally complex zone between the northwest to southeast striking Cadwallader and Fergusson faults, composed of metavolcanics, Pioneer greenstones, gabbro, and sheared serpentinite of the President ultramafic complex, which are intruded by diorite and granite of the early Permian Bralorne Suite. This complex assemblage correlates with rocks of the eastern Shulaps range (Calon et al. 1990). Locally the tectonostratigraphic wedge between the Cadwallader and Fergusson faults that hosts the major past-producing gold mines is referred to as the Bralorne Mine Block. The Bralorne Mine Block occurs as a steeply dipping fault-bounded lens forming a horst-like block. Its area is approximately 5 km in strike length, 600 m wide at surface and widening with depth. The block remains open at depth below 2 km. The vein system is controlled by second- and third-order fault structures relative to the Cadwallader and Fergusson faults. The main lithological units hosting the mineralization are the Bralorne intrusive suite (diorite, tonalite and gabbro) and the Pioneer basalt. Minor sedimentary units are found in the northwest of the Bralorne Mine Block, within the King mine area.
The Permian Bralorne intrusive suite includes “augite-diorite” and “soda-granite”, which commonly occur together. These phases locally are termed the Bralorne Diorite and Bralorne Granite, respectively, and combined with the Pioneer volcanics, host the Bralorne deposits. All three occur between the bounding Fergusson and Cadwallader faults.
Although mostly dioritic, the Bralorne Diorite varies from quartz-diorite to gabbro in composition. Several intrusive phases of diorite are present and are identified based on their composition and grain size variability. The Bralorne Diorite is intruded by the Bralorne Granite with complex intrusive relationships.
Typically, the Bralorne Granite is a leucocratic, coarse-grained intrusive body varying from trondhjemite to albite tonalite in composition. The main body of granite is found along the northeast side of the Bralorne Diorite, forming an elongate body approximately 2 km long x 250 m wide and also forms many dykes intruding the diorite. Five Cretaceous-Tertiary dyke phases, including grey plagioclase porphyry, albitite, green hornblende porphyry, Bendor porphyry and late unaltered lamprophyre, intrude the Bralorne Mine Block. The Bralorne intrusive suite forms the main host rock of the mineralization due to its favourable rheology.
The Pioneer Formation represents a smaller proportion of the Bralorne Mine Block compared to the Bralorne intrusive suite and consists of a steeply dipping pinching basalt body situated in the southeast of the Pioneer mine area. It comprises volcanic flows, pillow lava, volcanic breccia and fine- to medium-grained feeder dykes and sills. It is affected by widespread greenschist and sub-greenschist regional metamorphism, partially altering its original volcanic texture.
Within the Bralorne Mine Block, ultramafic rocks are typically sheared elongated bodies associated with the Cadwallader fault. Their gold hosting potential is low due to their ductile deformation style and low susceptibility to fracture and thus are considered to constrain the deposit to the southwest.
The Fergusson fault is characterized by a narrow band of strongly deformed and hydrothermally altered rocks representing the contact of the Bralorne intrusive suite with the adjacent sediments of the Fergusson Formation. This structure and rheological contrast constrain the deposit on the northeast side of the Bralorne Mine Block.
Throughout the Bralorne Mine Block, quartz veins are preferentially hosted in the more competent Bralorne intrusive rocks, less commonly in meta-basalt and meta-sediments, and rarely in ultramafic rocks (Cairnes, 1937; Ash, 2001). The deposit is crosscut by the late north-south trending Empire fault, which locally offsets the vein system in the Bralorne mine in an apparent dextral strike separation. Vein mineralization was interpreted by Leitch (1990) as synkinematic and structurally controlled by secondary fault sets related to westerly-directed, sinistral transpressional movement along faults bounding the Bralorne ophiolite.
Mineralization
The Bralorne gold mineralization is part of an orogenic mesothermal quartz-gold vein system hosted by second- and third-order fault structures in relation to the bounding Cadwallader and Ferguson faults. The quartz-gold veins are preferentially hosted in the more competent units and tend to sharply terminate at the contact with the softer ultramafic rocks associated with the Cadwallader fault to the south-west and with the Fergusson formation sediments juxtaposed by the Fergusson fault to the north-east.
The Bralorne Gold Project mineralization consists of quartz-gold veins forming an en-echelon array. From these quartz-gold veins, 112 high-grade quartz vein bodies were modelled as high-grade subsets, themselves grouped into four domains: King, Charlotte, Bralorne and Pioneer. Individual veins have varying strike and dip extents, while the collective vein network they comprise extends over 5 km by 600 m laterally within the Bralorne Mine Block and extends to at least 2,000 m in depth. Three types of veins are recognized on the property: Shear, Linking, and Transverse veins. Shear veins are dominantly more strike extensive, heavily banded, and dip moderately to the NNE. Linking veins form between adjacent Shear veins, are banded to massive, are less strike extensive and more variable in dip angle with steep to moderate dips towards the north. A third set of Transverse veins are late and cut both the Shear and Linking veins. They have extensive strikes, dip moderately to both the west and NNE, and tend to be dominated by brittle fault gouge, unconsolidated breccia, and quartz vein material. Vein widths generally range from tens of centimetres to 3 m, with the largest veins widening to 6 m.
Shear veins have been traced continuously for up to 1,500 m along a 110° to 145° strike, dip moderately to the NNE and are open at depth. They range from tens of centimetres to 3 m wide, and they pinch and swell along strike. Linking veins are generally less strike extensive than the Shear veins, with maximum strike lengths of 500 m and similar dip extensions. They are hosted in fault sets that strike roughly 700 m and dip about 75° northwest with widths ranging from tens of centimetres to 6 m. These more tensional veins form oblique splays off of the shear veins, commonly display sigmoidal geometries in both the horizontal and vertical planes and are generally the widest at the midpoints between the bounding Shear veins that confine them. A less well-known system of transverse mineralized structures that cross-cuts the other vein types is less dominant and more variably oriented. A good example of these veins located west of and parallel to the Empire fault (north-northwest-south-southeast orientation) has been identified in the Issuer’s drill holes and named the Charlotte Zone. It consists of at least four planes of brittle faults affecting west-dipping quartz veins hosting consistent anomalous gold grades along with sporadic high grades. The veins are typically massive to banded, hosting minor pyrite, arsenopyrite and/or pyrrhotite, with both margins and veins affected by varying degrees of brittle faulting evidenced by fault gouge and unconsolidated breccia.