The Jo (Nub West) occurrence is located at an elevation of approximately 1700 metres on a southeast-facing slope, north of the Finlay River and approximately 8.7 kilometres west-northwest of Budd Lake.
Regionally, the area is situated within a Mesozoic volcanic arc assemblage, which lies along the eastern margin of the Intermontane Belt, a northwest-trending belt of Paleozoic to Paleogene sediments, volcanics and intrusions bounded to the east by the Omineca Belt and to the west and southwest by the Sustut and Bowser basins.
Permian Asitka Group crystalline limestones are the oldest rocks exposed in the region. They are commonly in thrust contact with Upper Triassic Stuhini Group andesite flows and pyroclastic rocks, and marine sedimentary and volcanic rocks of the Lower to Middle Jurassic Hazelton Group. These rocks have been intruded by plutons and other bodies of the mainly granodiorite to quartz monzonite Early Jurassic Black Lake Suite and are in turn unconformably overlain by or faulted against Lower Jurassic calc-alkaline volcanics of the Toodoggone Formation (Hazelton Group).
The dominant structures in the area are steeply dipping faults that define a prominent regional northwest structural fabric trending 140 to 170 degrees. In turn, high-angle, northeast-striking faults (approximately 060 degrees) appear to truncate and displace northwest-striking faults. Collectively these faults form a boundary for variably rotated and tilted blocks underlain by monoclinal strata.
The area is underlain by undivided Lower to Middle Jurassic Hazelton Group volcanic rocks cut by feldspar porphyry dikes. Strong regional structures trend north-northwest and are accompanied by propylitic and argillic to advanced argillic alteration. A zone of argillic to advanced argillic alteration is largely exposed for approximately 1 kilometre in width and 5 to 6 kilometres in length between the Jo (Nub West) quartz-alunite zone and the NWB (MINFILE 094E 241) occurrence to the south.
Locally, an approximately 500- by 500-metre area of dominantly advanced argillic alteration containing quartz, alunite, dickite and pyrophyllite hosts an approximately 200-metre-wide zone of highly anomalous gold values occurring approximately 500 metres west of the Black fault. Illite, montmorillonite and chlorite occur locally within and on the outer edges of the area. Rock samples from this zone were extremely altered and oxidized with limonitic staining making it difficult to determine the hostrock. Less altered hostrocks in the vicinity are described as Lower Jurassic Toodoggone crystal tuffs of the Hazelton Group. Monzonite and feldspar porphyry dikes strike northwest through the area and are probably related to nearby Early Jurassic plutons.
In 2003, samples from the area yielded up to 0.220 per cent copper (Assessment Report 27429).
In 2004, rock samples yielded from 0.50 to 12.87 grams per tonne gold from highly altered volcanic rocks located approximately 150 metres in elevation below the Nub West alunite cap, whereas two 1.0-metre-long chip samples from the same area assayed 1 and 0.92 gram per tonne gold, respectively, with lead values in excess of 1 per cent (Assessment Report 27634).
Work History
In 1980 and 1981, Serem Ltd. completed programs of prospecting; geological mapping and rock, silt and soil sampling on the area as the Nub Mountain 1-5 claims. During 1987 through 1989, Toodoggone Gold Inc. completed programs of geological mapping, geochemical (heavy mineral, rock, silt and soil) sampling, trenching and a 248.0 line-kilometre airborne magnetic and electromagnetic survey on the area as the Fine 1-4 claims.
During 1999 through 2004, Stealth Minerals Ltd. completed programs of prospecting; geological mapping and rock, silt and soil sampling on the area as the Nub claims.
During 2016 through 2018, Amarc Resources Ltd. completed programs of soil and rock sampling, geological mapping, 115.0 line-kilometres of ground induced polarization surveying and 1940.0 line-kilometres of airborne magnetic surveying on the area as the Joy property.
