The Nub 4 (Zorro) occurrence is located 11.0 kilometres south-southwest of Bend Mountain, 6.5 kilometres northwest of Budd Lake and west of the Finlay River.
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.
Locally, the area is underlain by volcanics and derived sediments of the Toodoggone Formation and regionally undivided, Lower to Middle Jurassic rocks of the Hazelton Group. These are intruded by multiphase granodiorite and quartz-monzonite plutons of the Black Lake Suite (formerly part of the Omineca Intrusions). Hazelton Group volcanics consist of green to grey plagioclase and pyroxene porphyry andesite flows, subaqueous tuffs, greywacke and conglomerate. Toodoggone volcanics are divided into quartz-bearing and non-quartz–bearing units; the former contains 2 to 20 per cent quartz phenocrysts and is more common than the later. Both contain 10 to 35 per cent plagioclase and rare potassium feldspar phenocrysts in unwelded and welded crystal tuffs and crystal lapilli tuffs, volcaniclastics and rare pyroclastic breccias. A large multiphase pluton is exposed to the east and is composed of biotite and hornblende granodiorite cut by plagioclase feldspar porphyry quartz monzonite. The rocks are highly fractured due to faulting and the intrusion of plutons. The dominant trend of faulting is 150 and 120 degrees. Small monzonite stocks and dikes are common.
Propylitic alteration is ubiquitous in the area and consists of chlorite, epidote, calcite and pyrite. Exceptions are in areas of intense hematization. Potassic alteration occurs in fractured volcanics immediately adjacent to intrusions. Hazleton Group volcanics tend to be skarn altered with magnetite, actinolite, epidote, and pyrrhotite. Extensive areas of volcanics have been pyrite-altered, with subsequent leaching resulting in pronounced gossans. Quartz-sericite-pyrite, zeolite and argillic (kaolinite) alteration occur along fault structures.
Quartz vein breccia and stockwork occur within Toodoggone crystal to lapilli tuffs and altered intrusive rocks. Quartz is massive to cockscomb-textured and contains disseminated pyrite, galena, chalcopyrite, sphalerite and rarely bornite. Gangue minerals include calcite, epidote, chlorite, barite, specularite and manganese oxides. Gold and silver values are associated with both sulphide-bearing and non-sulphide–bearing veins and are extremely erratic.
The Nub 4 occurrence consists of a zone of grey quartz veins with or without bornite and pyrite hosted in a moderately pronounced gossan within Toodoggone volcanic rocks, primarily chloritized andesite and chloritic andesite feldspar porphyry, west of a major north-northwest–striking fault. Hydrozincite and malachite are also reported in the area.
In 1981, a sample (CC-17-81-1) from a quartz vein analyzed 4.7 grams per tonne gold and 15.0 grams per tonne silver, whereas a sample (SC-44-80-11) from a grey quartz vein in volcanics yielded 10.7 grams per tonne gold, 409.7 grams per tonne silver, 0.10 per cent zinc, 0.05 per cent lead and 0.004 per cent copper (Assessment Report 9747).
In 1988, a sample (no. 2) assayed 1.15 grams per tonne gold, 70 grams per tonne silver and 0.55 per cent lead (Assessment Report 18161).
In 1989, a rock chip sample (106184) from trench 4 yielded 1.03 grams per tonne gold and 10.2 grams per tonne silver over 2.0 metres, whereas chip sampling of trench 1 averaged 0.11 gram per tonne gold with 12.4 grams per tonne silver over 8.0 metres (Assessment Report 19998).
In 2003, rock samples from the area yielded up to 3 grams per tonne gold, 37.1 grams per tonne silver, 1.00 per cent lead and 10.00 per cent zinc (Assessment Report 27429).
In 2004, a sample (185963) of vein material from the Zorro trench yielded 2.83 grams per tonne gold, 22.1 grams per tonne silver and 0.596 per cent lead (Assessment Report 27634).
In 2017, a rock sample (952372) assayed 0.192 gram per tonne gold and 74.2 grams per tonne silver (Assessment Report 37516).
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.
