The immediate area of Red Cap prospects are underlain by volcanic flows, pyroclastic rock units, and sedimentary rocks. Volcanic rock units of the Laberge group consist of rhyolitic(?) to basaltic flows, volcanic breccia, agglomerate, tuffs, and minor volcanic sandstone. Later petrographic analysis of rock mapped in the field as rhyolite indicated that they were in fact a bleached and silicified intermediate rock. The volcanic units are underlain by sedimentary rock units or the Stuhini Group consisting of thick-bedded, dark greywacke, conglomerate, mudstone, siltstone, and shale with minor volcanic flows, tuffs, breccia, limy shale, and limestone. Laberge Group sediments are reported along the southern margin of the prospect area and are composed of conglomerate, sandstone, shale, and greywacke. Hornblende-biotite granodiorite stocks and associated feldspar porphyry dikes intrude the strata and are assigned to the Windy Table Complex. In the prospect area, these intrusive rocks consist of light grey, medium crystalline granodiorite and a darker grey diorite or quartz diorite.
There are three main structural components in the Red Cap prospect area. The most pronounced of these is an east-northeast trending fault, located on the the north. The second major structure strikes in a northeast direction and runs through the core of the porphyry intrusion. The third structure cuts through the northeast. This system of east-west and northeast-southwest faults and fractures form the basic fabric of the area and their presence is thought to have controlled subsequent development of stockworks within the porphyry system and appear to have influenced the distribution of the associated mineralization (Assessment Report 25970).
The Ridge, Ridge Extension and North Face zones occur to the northeast of the Slope zone and are characterized by more felsic volcanic rocks, lapilli tuffs and agglomerates than granodiorite. Mineralization consists of vuggy, sheeted, euhedral quartz-sulphide veins up to 15 centimetres wide which strike in east and northeast directions and are associated with very gossanous quartz-carbonate-pyrite alteration zones which trend northeast. Sulphides include pyrite, arsenopyrite, pyrrhotite, chalcopyrite, sphalerite and galena.
In 1981, a series of seven NQ diamond-drill holes totaling 1203.6 metres were drilled by Omni Resources from four drill sites and varied in depth from 132.3 to 260.0 metres (Assessment Report 10452). The holes were designed to test the Ridge zone and a large molybdenum soil geochemical anomaly called the Slope zone. The Ridge zone was defined by re-analysis of soil samples collected in 1980 for gold. The best hole in this series was RC8l-l that tested a copper-molybdenum-silver anomaly. This hole intersected 9.2 metres grading 1.59 per cent copper and 59.65 grams per tonne silver (Assessment Report 10452).
Drilling in 1982 on the Ridge zone intersected 2.15 metres of massive sulphide mineralization that assayed 96.04 grams per tonne silver and 1.84 per cent copper (Rayner, 1983). This massive sulphide has been interpreted as both a conformable deposit of possible volcanogenic origin and as a vein. Rayner (Assessment Report 11089) plots the drillhole just above the Bergie showing of the East Cirque zone but Wilkins and MacKinnon (Assessment Report 18803, Figure 4) show the drillhole at the Ridge zone to the east.
The Slope, Ridge and East Cirque zones are considered by Wilkins and MacKinnon (Assessment Report 18803) to be part of one large porphyry system with the Slope (104K 010) representing the stockwork and sheeted vein-hosted copper and molybdenum mineralized core. The Ridge and East Cirque zones to the northeast and possibly Moly and Copper creeks to the southwest may represent structurally controlled conduits for sulphide bearing hydrothermal solutions. These are characterized by massive sulphide veins up to 2 metres in size with associated precious metals. Gold and silver mineralization occurs throughout the system with higher grades concentrated away from the copper-molybdenum core.
A complete history of the Red Cap property, including the Ridge zone, is given in Red Cap – Slope zone (104K 010).
