The Cumberland area is underlain by a series of north to northwest trending Hazelton Group intermediate (dacite/andesite) composition volcanic flows, pyroclastics and pillow lavas interpreted to be part of the Middle Jurassic Salmon River Formation. Locally, they consist of red, green and purple volcanic breccia, conglomerate, sandstone, argillaceous siltstone with intercalated crystal and lithic tuffs. The stratigraphic and structural relationships are not well defined but the regional strike is to the northeast with an east dip.
Locally, andesite, tuff-volcanic breccia, argillite and conglomerate are the most common rock types. The eastern part of the claim is underlain by pillowed andesite, dark grey to green in color, and forms a massive cliff 30 to 40 metres in height. The tuff is grey to green in color with poorly sorted angular fragments with some flow banding. The volcanic breccia is similar to the tuff with larger unsorted angular fragments. Sediments in contact with the volcanics include a dark green-grey, massive chert and argillic conglomerate, which is characterized by a sandy matrix with rounded cobbles to boulders.
The Cumberland prospect, discovered in 1898 and explored by underground drifting, is a true polymetallic, volcanogenic massive sulfide within a mafic host. It has grades of 9.80 per cent zinc, 2.70 per cent lead, 0.45 per cent copper, 9.33 grams per tonne gold and 91.5 grams per tonne silver (Assessment Report 30131). This area contains occurrences of massive sulfides, barite, base and precious metal mineralization plus anomalous zones enriched in Eskay Mine “pathfinder” elements and base metals.
Two adits were excavated on the Cumberland during the 1890's and a very small shipment of hand-sorted ore was reported. The prospect appears to have volcanogenic massive sulphide attributes, and has been frequently examined and partially explored by diamond drilling and geological mapping and geophysics. During the 1993 field program, a limited amount of time was spent re-examining the Placer Dome geological map. As well, several contour soil geochemical lines were completed up hill, south of the showing area. In 1995, preliminary mapping around the showing recognized Salmon River stratigraphy. In 1996, the property was mapped in detail with the discovery of bedded barite mineralization. The showings were trenched and drilled. Drilling demonstrated that these showings are not structurally controlled but are probably stratiform in nature. Two holes were drilled under the main Cumberland Showing demonstrating that the mineralization is continuous and is not cut off by faulting. During the 1997 field season, Homestake Canada cut 15.6 km of grid at the Cumberland prospect.
Mineralization at the Cumberland occurs in mafic volcanic units, possibly pillow basalt and breccia and thin mudstone horizons. Mineralization is composed of lenses 0.5 to 3.0 metres wide of massive sphalerite, barite, galena and pyrite. Sampling of this material has returned assay values as high as 9.4 grams per tonne gold, 93 grams per tonne silver, 0.45 per cent copper, 2.70 per cent lead and 9.80 per cent zinc. The zone of mineralization is highly sheared and disrupted and both the mineralization and host rocks have a pronounced mylonitic fabric and a steep plunge. A re-examination of rocks mapped by Placer as conglomerate and mudstone revealed rhyolite breccia and tuffaceous mudstone. The rhyolite is aphyric, cream to white coloured, with flow-banded to massive fragments in a dark gray, siliceous matrix. These rhyolite units possibly lie in the structural footwall of the Cumberland showing. Prospecting and soil geochemical traverses 1000 metres south of the showing (at 800 metres elevation) identified two possible extensions of the rhyolite horizons. In 1997, three outcrops of massive barite mineralization containing galena, sphalerite and associated silver mineralization were discovered and sampled returning assays up to 12,171 grams per tonne silver in grab samples and 4046 grams per tonne silver in a one-metre channel sample site (WWW http://www.kenrichmining.com, June 1998).
A 5-centimetre chip sample taken along Silver Creek (from Ougma, Lot 269) assayed 3502.2 grams per tonne silver (Assessment Report 16318). The sample was from a silicified carbonate rich shear zone which was reported to host possible ruby silver (pyrargyrite).
Two adits were excavated on the Cumberland during the 1890's and a very small shipment of hand-sorted ore was reported.
Minor mineralization consisting of disseminated pyrite is ubiquitous throughout the volcanics and argillite. Two mineral deposits were reported to have been developed by constructing two short adits close to the contact between the sediments and volcanics in 1935.
At an elevation of about 370 metres, a sheared and brecciated zone in the volcanics, striking northwest and dipping steeply northeast, contains small, irregular lenses and stringers of quartz, barite and calcite. In an adit driven along the north side of a dyke that cuts the shear zone, is a vein of quartz, calcite and barite which hosts pyrite, galena, sphalerite, tetrahedrite, stibnite and some argentite. In 1935, a grab sample taken from an old dump of these workings assayed 0.69 grams per tonne gold, 3586.2 grams per tonne silver, 0.5 per cent copper, 8.0 per cent lead and 4.0 per cent zinc. A reported 18 tonnes of similar material was mined but never located (Minister of Mines, Annual Report 1935, page B12).
To the northeast of this adit, at an elevation of about 412 metres, is a quartz replacement zone that is reported to consist of veinlets and lenses of quartz with stringers and blebs of chalcopyrite, pyrrhotite, pyrite, sphalerite and galena. The zone strikes about 345 degrees and dips 70 degrees east. Apparently 14 tonnes of this material was mined and left at the portal to the adit. In 1935, a representative sample from this dump assayed 8.9 grams per tonne gold, 82.28 grams per tonne silver, 0.3 per cent copper, 3.0 per cent lead and 10.0 per cent zinc (Minister of Mines, Annual Report 1935, page B12).
In 1986, Catear Resources Ltd. staked eight claims (Corey 1-8) in the Mount Madge area and conducted a regional rock and stream sediment geochemical program. This work resulted in the discovery of the C-10 Zone, a large, structurally controlled alteration zone containing gold and silver. In 1987, Bighorn Development Corporation, a sister company to Catear conducted a widespread stream sediment, soil and rock geochemical surveys along with prospecting over the property. Bighorn conducted detailed work on the Cumberland prospect consisting of 49 metres of trenching and 590 metres of diamond drilling in six holes. In 1988, they drilled six holes on the C-10 zone totaling 647 metres.
In 1986, Kenrich Mining Corporation along with Ambergate Explorations Ltd. acquired the Sul and Nica Claims and by 1990, acquired much of the Corey package of claims that they presently hold. In 1994, Kenrich and Ambergate amalgamated under the one company, Kenrich Mining Corp.
In 1987, a 0.5 to 0.75 metre zone was mapped at the Cumberland adit entrance. The host rock in the vicinity of the showing consists of highly fractured andesite with thin quartz-pyrite fracture fillings. Other sulphides include chalcopyrite, sphalerite and traces of galena. The heavily mineralized zone strikes between 140 to 150 degrees and dips 85 degrees northeast. A grab sample from this massive sulphide zone assayed 4.32 grams per tonne gold and 169.37 grams per tonne silver (Assessment Report 16318).
In 1989 and 1990, Kenrich and Ambergate performed basic assessment work consisting of geological mapping, surface geochemistry and geophysics and diamond drilling of geophysical anomalies on the Sul and Nica claims.
The Silver Creek and Devils Club Creek (Daly) showing in the Cumberland vicinity investigated in 1987 (Assessment Report 17205). In
In 1991, Placer Dome optioned the Sul and Nica claims adjacent to their Kerr Property, and proceeded over the next two years to perform detailed soil geochemical and ground geophysical surveys followed by diamond drilling on the Sul 1 claim. Along with this detailed work, Placer also reanalyzed all of the regional stream sediment samples taken by Bighorn in 1987. No evaluation was done on this multielement analysis until 1996. Placer did some detailed mapping, soil sampling and ground geophysics over the Cumberland showing (Star) and over the C-10 shear zone. None of this work was followed up and the property was returned to Kenrich and Ambergate in 1992.
In 1993, Kenrich did a regional, mapping, geochemical and prospecting program over the northwestern third of the property. This program located the high grade gold mineralization over what is now referred to as the TV Zone.
In 1994, Kenrich concentrated geological mapping and grid soil geochemistry and trenching over the TV Zone in preparation foi drilling in 1995. They also did grid geochemistry and geophysics over the Bench and Battlement Zones.
In 1995, Kenrich drilled 22 diamond drill holes totaling 3,863.63 metres over the TV Zone. They also did detailed geological mapping and soil geochemistry over this zone. They did some cursory regional work over the Cumberland and C-10 zones.
In 1996, Kenrich did an extensive regional geological and geochemical survey on the property as well as detailed geology, geochemistry and drilling of 11 holes (1559 m)on the TV Zone and 9 holes (1383 m) on the Bench Zone. Further detailed geology along with drilling of five holes (634 m) was completed on the Cumberland Zone. An airborne magnetic and radiometric survey was completed over the western half of the property.
In 1997, Kenrich optioned the Bench, Battlement and Cumberland Zones, approximately 30% of the property to Prime Resources. Prime did a limited surface sampling and mapping program over this block of land referred to as the PRU Block. On the remaining area, Kenrich completed soil sampling and geological mapping on the HSOV, TM and Nica 1 Zones.
In 1998, Kenrich improved and extended the soil grid over the HSOV zone to the north and over the NICA 1 claim. A total of 10 km of line was recovered or located and 102 soil samples were taken.. Minor hand trenching was performed on the HSOV and NICA 1. A total of 168 rock samples were taken for petrographic studies lithogeochemistry and trace element geochemistry. Moss mat sampling~(20 samples) and silt sampling (1 sample) were taken over areas extending the anomalous area. A VLF EM and magnetometer survey was completed over the HSOV grid which helped in mapping the structure and stratigraphy of the area.
In 2003, lithogeochemical samples were taken from four drill holes on different parts of the Corey property that were drilled during previous programs in the 1990s including from those drilled on the Bench zone in 1996 and 1997 (Assessment Reports 24965 and 25384); Cumberland zone in 1996 and 1998 (Assessment Report 24965) and South Unuk in 1998 (no previous assessment report).
In 2004, Geological mapping by Kenrich-Eskay Mining Corp was focused on the two main areas: the western flank of Mount Madge, namely the Cumberland and South Unuk grids, and the C10 Zone on the eastern flank of Mount Madge (as reported in Assessment Report 30131). These areas were known to contain some of the best examples of Eskay Mine-equivalent stratigraphy and extensive hydrothermal alteration on the Corey property. Preliminary geological examinations were carried out in the vicinity of the HSOV Showing east of the C10 Zone and in the Virginia Lake area in the northwest portion of the claim block Mapping was conducted at 1:2000 scale in the field and compiled onto 1:10,000 and 1:20,000 maps. Mapping was complimented by a large program of lithogeochemical sampling which allowed for an important refining of the Corey stratigraphy. Mapping in 2005 and 2006 expanded to include the Battlement-Virginia Lake area, the southwestern flanks of John Peaks (now termed the Golfcourse area) and the eastern portions of the property (including the new Spearhead Showing) (as reported in Assessment Report 30131). More detail was also added to the previous mapping in the Cumberland and South Unuk areas. Results of the 2005 Cumberland Zone drill holes clearly illustrated the high grade, poly metallic (Au-Ag-Cu-Pb-Zn) nature these Eskay-style base and precious metal-rich massive sulphides. Tonnage potential was limited and a total of 8 drill holes were completed in 2007, seeking an expansion to the northwest and southeast of the zone. The 2007 drilling did not intersect any new mineralization.
In 2006, a helicopter-borne geophysical (magnetic and electromagnetic) survey was carried out on behalf of Kenrich-Eskay Minng Corp on the Corey Property (Assessment Report 28538). The total line-kilometres amounted to 1191 kilometres within the project area.
In 2007, kenrich-Eskay continued mapping in the Battlement, Lower Cumberland/Smitty and Eastern Mandy Valley (HSOV-Spearhead-Red Lightning trend) areas (Assessment Report 30131). A two-man prospecting crew was active on the property for most of the 2007 season; they explored for possible bedrock sources of stream geochemical anomalies and examined other areas of interest, focusing on the Battlement North and the “Eastern Belt” areas. 115 rock, 236 lithogeochemical and 34 sieved silt samples were collected. Twenty-one drillholes were completed in 2007 for 5787 metres of drilling. Target areas were the Battlement, Cumberland, Smitty, South Unuk and Red Lightning areas. Some resampling of 2005-06 drillcores from the C10 zone occurred. No massive sulfide mineralization was intersected in any of the Cumberland holes, though the sulphidic clasts and disseminated pyrite in mudstone present in hole 22 are notable.
Work on the Corey Project in 2008 concentrated on drill-testing the Red Lightning Showing. The drilling program comprised 1749.4 metres of diamond drilling in 7 drillholes (CR08-83 to CR08-89) from three drillpads. Results identified a new Ni-Cu-Co-rich massive sulphide zone (Kenrich-Eskay Mining Website: 2009 report by McKinley, Tennant and Nelles).
In 2020, Eskay Mining Corp. completed a program of prospecting, rock sampling, ground and airborne geophysical surveys and 4335 metres of diamond drilling in 20 holes on the area as part of the Sib-Corey-North Mitchell property. The geophysical surveys consisted of a 911.7 line-kilometre airborne electromagnetic survey, a 55.85 line-kilometre induced polarization survey and a 43.19 line-kilometre magnetotelluric survey. Drilling was performed on the TV (MINFILE 104B 385) and Jeff (MINFILE 104B 525) occurrences.