The AT991 (Atty Gossan East) occurrence is located at an elevation of approximately 1750 metres on a northeast-trending ridge, approximately 1.5 kilometres south of Attycelley Creek and 4.5 kilometres east of Duncan Lake, about 191 kilometres north-northwest of the community of Germansen Landing.
The Toodoggone district lies within the eastern margin of the Intermontane Belt and is underlain by a northwest trending belt of Paleozoic to Paleogene sediments, volcanics and intrusions covering an area of 90 by 25 kilometres. The basement rocks are Proterozoic metasedimentary equivalents of the Hadrynian Ingenika Group. These rocks are unconformably overlain by volcanic and sedimentary units of the Devonian to Permian Asitka Group, which are in turn overlain by Upper Triassic basaltic to andesitic flows, volcaniclastics and minor limestone of the Stuhini Group. Volcaniclastic rocks of the Lower Jurassic Hazelton Group and rhyolitic to dacitic flows, intrusions and volcaniclastics of the Lower Jurassic Toodoggone Formation (Hazelton Group) overlie the Stuhini Group. Further to the west, nonmarine sediments of the Cretaceous Sustut Group overlie the volcanic strata and form the western margin of the district.
The Early Jurassic Black Lake Suite, of quartz monzonitic to granodioritic composition, has intruded the older strata in the central and eastern parts of the region and forms the eastern margin of the Toodoggone district. Within the district, syenomonzonitic and quartz feldspar porphyritic dikes may be feeders to the Toodoggone Formation.
The dominant structures in the area are steeply dipping faults that define a prominent regional northwest structural fabric trending 140 to 170 degrees. 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 augite porphyry basalt, dacite and andesite crystal and lapilli tuffs and flows, and augite crystal tuffs and ash tuffs of the Stuhini Group. To the northeast and east lie dacite lapilli and crystal tuffs and breccias, and andesite crystal tuffs of the Toodoggone Formation, which are interbedded with conglomerate, sandstone and siltstone. The Early Jurassic Kemess pluton, a monzonite intrusive body that is part of the Black Lake Suite, outcrops to the south.
At the AT991 occurrence, silicified gossanous (limonite, jarosite and goethite) zones in andesitic to basaltic volcanics, siltstone-wacke and monzonite to syenite dikes host quartz-carbonate±barite veins, up to 20 centimetres wide, and shears with disseminations, blobs, fracture fillings and small veins of massive pyrite, chalcopyrite and sphalerite mineralization. Malachite, azurite, epidote, sericite, magnetite, hematite and chlorite alteration minerals are also reported. The shears are braided and typically vary from 20 to 50 metres in length, however, one shear has been traced for greater than 600 metres, with associated lenses of mineralization.
In 1999, a rock sample (ATR-7) assayed 2.55 per cent copper, 16.0 grams per tonne silver and 7.04 grams per tonne gold, whereas two other samples (ATR-19 and -20), taken approximately 500 metres to the west in a north-facing cirque, yielded up to 0.392 per cent copper, 0.265 per cent lead, 1.00 per cent zinc, 46.8 grams per tonne silver and 0.12 gram per tonne gold (Assessment Report 26166).
In 2018, a rock sample (32229951) of polymetallic veining near a gossanous contact zone from the western side of the north-facing cirque assayed 0.08 gram per tonne gold, 25.4 grams per tonne silver, 0.082 per cent cadmium, 0.220 per cent lead and 7.708 per cent zinc (Assessment Report 37748).
The area was originally staked by D.W. Chisholm in 1929 as the Fokker mineral claim.
During 1969 through 1973, Kennco Explorations Ltd. completed programs of prospecting and soil sampling on the area as the Attycelley 1-6 claims. In 1977, Bishop Mines Ltd. completed a program of rock and soil sampling and a 2.0 line kilometre ground magnetic and electromagnetic survey on the area as the Audrey property.
In 1980, ABM Mining Corp. completed a 69.8 line kilometre airborne magnetic and electromagnetic survey on the area as the Audrey 1, 2, East and West claims and Kem 1-9 claims. Also, at this time, Inca Resources Inc. completed a program of soil sampling and a ground electromagnetic survey on the claims. In 1981, Texasgulf Inc. completed a program of geological mapping and rock sampling on the Audrey and Kem claims on the behalf of Inca Resources. In 1982, Kidd Creek Mines Ltd. completed a program of geological mapping, trenching and rock sampling.
During 1990 through 1999, Electrum Resource Corp. conducted programs of prospecting, geochemical (rock, silt and soil) sampling, geological mapping and a 4.7 line kilometre ground magnetic and electromagnetic (VLF) survey on the area as the At 1-2 and Atty 3-7 claims.
During 2000 through 2004, Finlay Minerals Ltd. conducted programs of rock, silt and soil sampling, geological mapping and ground induced polarization and magnetic surveys on the area.
During 2013 through 2016, Finlay Minerals conducted further programs of prospecting, geochemical (rock and soil) sampling and a LiDAR survey on the Atty property. In 2018, Serengeti Resources Inc. conducted a program of rock sampling, core re-logging and sampling, geological mapping and a 20.0 line kilometre ground induced polarization survey on the area as the ATTY-ATG property.
