The Bishop occurrence is located at an elevation of approximately 1610 metres in a northeast-facing valley, southwest of the Toodoggone River and approximately 5.5 kilometres southwest of Toodoggone 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 occurrence area is underlain by reasonably undivided volcanics of the Hazelton Group. On a property scale, four units have been delineated from the volcanic stratigraphy. These consist of light-grey to green plagioclase and hornblende plagioclase tuffs and breccias; grey-green, orange and brown, fine to coarse-grained plagioclase porphyry, including minor quartz-eye porphyry; felsic tuffs and breccias; and thin-bedded, well-cleaved rhyolite. Indications are that this stratigraphy is continuous with the Toodoggone Formation rocks immediately to the west. These rocks have been intruded by three varieties of plutonic rocks: syenite to syenodiorite, granodiorite and quartz diorite, that has been subject to moderate to intense kaolinite and pyrite alteration (up to 40 per cent) and silicification. The silicification is commonly so intense that all primary textures are obliterated. Three major fault systems intersect just north of the occurrence.
The Bishop showing is composed of four separate zones—East Ridge, Cirque, Upper Creek and Lower Creek — that form a large silicified stockwork with pyrite alteration.
The East Ridge zone consists of a silicified stockwork, a feeder system and three multiple gossans, hosted in medium- to coarse-grained feldspar porphyry. The stockwork consists of an area of intense silicified blue-grey dacite. The margins are marked by a transition through lesser degrees of silicification to a medium-grained, unaltered feldspar porphyry. The zone trends 170 degrees and spans an area of roughly 30 square metres.
The Cirque zone is separated from the East Ridge zone by a north-northeast–striking fault. The gossan consists of a series of oxidized outcrops, 3 to 5 metres apart and trending 280 degrees at an elevation of approximately 1860 metres. These rocks are silicified dacitic feldspar porphyry grading to rhyodacite at the upper contact with a thin, well-fractured felsic unit. The gossans range in exposed thickness from 3 to 5 metres. Mineralization includes up to 25 per cent pyrite and 1 per cent arsenopyrite.
The Upper Creek zone is located downslope of the Cirque zone at an elevation of approximately 1610 metres and is hosted in medium-grained feldspar porphyry with up to 1 per cent of an unidentified silver mineral. The siliceous alteration may form a continuous gossan with the Lower Creek zone.
The Lower Creek zone, located downslope of the Upper Creek zone at an elevation of approximately 1590 metres, consists of pervasively silicified feldspar porphyry containing up to 25 per cent pyrite and 1 to 2 per cent arsenopyrite and chalcopyrite. No samples from this zone are known.
In 1986, a sample (JS-86-P3007) from the East Ridge zone yielded 1.8 grams per tonne silver and 0.14 per cent lead, and a sample (JS-86-P3012) from the Cirque zone yielded 1.3 grams per tonne silver and 0.162 gram per tonne gold (Assessment Report 15599). Also at this time, two samples (JS-86-P3015 and P3016) from the Upper Creek zone yielded up to 1.4 grams per tonne silver (Assessment Report 15599).
In 1988, a grab sample (18469) of rusty feldspar porphyry from the East Ridge zone assayed 3.2 grams per tonne silver and 0.162 gram per tonne gold, and a rock sample (18456) of feldspar porphyry with quartz stringers over 0.50 metre from the Cirque zone yielded 4.4 grams per tonne silver and 0.219 gram per tonne gold (Assessment Report 18535).
In 1997, an outcrop sample (24739) of quartz vein cutting an intensely silicified intermediate volcanic rock yielded 0.111 gram per tonne gold and 2.5 grams per tonne silver (Assessment Report 25572).
Work History
In 1982, Newmont Exploration of Canada completed a program of geological mapping and rock, silt and soil sampling on the area immediately west as the Sun 1-2 claims.
In February 1986, an airborne VLF-EM and magnetometer survey was flown over the claims by Western Geophysical Aero Data Ltd. on behalf of Peralto Resources Corp. The close association of magnetometer highs and lows was interpreted as fault related.
In October 1986, Hi-Tec Resource Management Ltd., on behalf of Peralto Resources, carried out a program of soil, rock, and silt sampling; geological mapping; prospecting and a ground geophysical survey on the Bishop, Castle, Kevin and Knight claims. They collected 89 rock, 30 silt and 522 soil samples and conducted an 8.5-kilometre ground VLF survey and a 6.2-kilometre magnetic survey. Several zones of silicification and pyritization were identified on the property. Geochemical and geophysical surveys have delineated a northwest-trending structure with zones of secondary silicification and faulting.
In 1988, Peralto Resources Corp. completed a geochemical sampling program, primarily on the Bishop and Knight claims. The work consisted of two contour soil sampling lines at approximately 1700 and 1900 metres above sea level, one downhill soil traverse, one silt sampling line and rock sampling. A total of 58 rock chip and grab samples were collected.
During 1997 through 1999, Electrum Resources Corp. completed programs of rock, silt and soil sampling and a 2.5 line-kilometre ground magnetic and electromagnetic (VLF) survey on the area as the Spruce claim.
In 1999, Stealth Minerals staked the initial claims in the area of what is now known as the Sickle-Sofia property and, later that year, Standard Metals conducted a small-scale geochemical program on the area on behalf of Stealth Minerals.
In 2004, Stealth Minerals expanded the Sickle-Sofia property package by staking additional claims in the area, conducted a grid-based soil survey over 27 square kilometres and collected 728 rock samples. Also at this time, sampling by Finlay Minerals Ltd. occurred on their Spruce claims in the vicinity of the occurrence.
In 2005, a program of geological mapping and a 21 line-kilometre induced polarization and ground magnetic geophysical survey was completed over the lower, glacial-fluvial–covered portion of the Sofia (MINFILE 094E 238) copper-gold porphyry target.
In 2006, Stealth Minerals completed further programs of rock sampling, geological mapping and ground geophysical surveys on the area.
In 2015, a program of geophysical review completed for Cazador Resources Ltd. on the Sofia property identified five target areas.
See Sickle Creek (MINFILE 094E 237) occurrence for further details of the Stealth Minerals Limited Sickle-Sophia property.
