Mineralization
The mineralized zones at Red Mountain consist of crudely tabular, northwesterly trending, and moderately to steeply southwesterly dipping gold bearing iron sulphide stockworks.
Four important mineralized zones exist at Red Mountain, which include the Marc, AV, JW, and 141 Zones.
The Marc Zone outcrops at an approximate elevation of 1900m, located 300m southeast of the summit of Red Mountain. The Marc Zone dips moderately to steeply to the southwest and is primarily restricted to the altered Hillside Porphyry unit. The Marc Zone ranges from 5m to 40m in width, is approximately 80m in height, and is 200m in strike length.
The AV Zone is northwest of the Marc Zone and represents a displaced continuation of the Marc Zone across the steep, northwest dipping semi-brittle Rick fault. Total displacement is approximately 100m. The AV Zone exhibits similar grades, characteristics, and lithological setting as the Marc Zone. The AV Zone ranges from 5m to 30m in width, is approximately 70m in height, and is 185m in strike length.
The JW Zone is the most northwesterly of the ore zones at Red Mountain. Its southeastern end starts to develop where the gold values in the AV Zone diminish and is located approximately 50m below the AV Zone. The Goldslide Porphyry appears to step down at this point causing the AV Zone gold values to abate and concentrate in the JW Zone at a lower elevation. The JW Zone is distinctly different from the AV and Marc Zones with lower gold grades in general and a tabular, narrower, and shallower dipping shape. The JW Zone dips at approximately 43⁰ to the southwest, is approximately 10m in width, 200m in height, and 120m in strike length.
The 141 Zone is located 200m southwest of the Marc and AV Zones at approximately the same elevation. The 141 Zone is primarily hosted by altered sediments and sits within an embayment of the Hillside Porphyry. Based on drilling to date, the 141 Zone is approximately 30m in width, 60m in height, and 75m in strike length.
The stockwork zones are developed primarily within the Hillside porphyry and to a lesser extent in rafts of sedimentary and volcaniclastic rocks. Although locally anomalous gold values are present within the Goldslide porphyry, significant auriferous sulphide stockwork zones have not been located in this rock unit, which generally lies less than 100 meters below the mineralized zones.
The stockwork zones consist of pyrite microveins, coarse-grained pyrite veins, irregular coarse-grained pyrite masses, and breccia matrix pyrite hosted in the Hillside porphyry. Pyrite is the predominant sulphide; however, pyrrhotite is locally important. Vein widths vary from 0.1cm to approximately 80cm, and widths of 1cm to 3cm are most common. The veins are variably spaced, average 2 to 10 per meter, and are often heavily fractured or brecciated with infillings of fibrous quartz and calcite (Craig, 2002).
The pyrite veins typically carry gold grades ranging from 3 gpt to greater than 100 gpt. Gold occurs in grains of native gold, electrum, petzite, and a variety of gold tellurides and sulphosalts (Barnett, 1991). These mineral grains, which are typically 0.5 to 15 microns in size, occur along cracks in pyrite grains within quartz and calcite filled fractures in pyrite veins and to a lesser extent as inclusions within pyrite grains (Craig, 2002).
Sericite-pyrite-carbonate-quartz alteration is intimately associated with the gold enriched mineralized zones. The mineralized zones are typically bleached due to extensive sericite development.
The stockwork zones are surrounded by a widespread zone of disseminated pyrite and pyrrhotite alteration which is responsible for the extensive gossan for which Red Mountain is noted. The zones are also partially surrounded by a halo of light red-colored sphalerite. Sphalerite comprises 0.5% to 4.0% of the rock and generally is more abundant in the footwall portions of the zones. The relationship between this sphalerite and the gold bearing pyrite stockworks is unclear (Craig, 2002).
