The Joanna East mineral showing is located along the southwest ridge of Mount Gordonia, 550 metres from the summit. The showing is 290 kilometres north of Smithers. It lies within the Omineca-Cassiar mountains in the north-central portion of the Toodoggone gold camp.
The showing 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 Tertiary 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 Takla Group andesite flows and pyroclastic rocks. These Takla 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 calcalkaline volcanics of the Toodoggone Formation, Hazelton Group.
The dominant structures in the area are steeply dipping faults which 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.
Toodoggone volcanics, observed at the Joanna East showing, are described as purple agglomerates, grey to purple tuffs, rhyolites and orange lithic to crystal tuffs (Assessment Report 20671). The oldest rocks are light to dark green porphyritic or massive andesitic flows and pyroclastics of the Takla Group (Assessment Report 20671). These have been summarized as basaltic and andesitic flows and breccia, with minor limestone and argillite (Bulletin 86).
Propylitic alteration is widespread throughout the area surrounding the Joanna East showing, predominantly affecting andesitic flows and tuffs. These zones are characterized by chlorite alteration of plagioclase, biotite and hornblende phenocrysts, accompanied by a strong increase in epidote and/or carbonate, pyrite and magnetite in the groundmass (Assessment Report 20671).
The southwest ridge of Mount Gordonia is crossed by numerous north and northwest-trending, steeply dipping faults, with which numerous quartz veins and zones of silicification are associated. The veins are commonly mineralized with gold, silver and copper. One of these veins comprises the Joanna East showing. The quartz vein is rusty weathering and exhibits minor propylitic alteration. Sulphides comprise up to 7 per cent, consisting of chalcopyrite and lesser pyrite; oxides comprise 2 per cent consisting of limonite and malachite (Assessment Report 20671).
In 1986, a grab sample (JS-86-006) of quartz with malachite assayed 9.50 grams per tonne gold, 6.9 grams per tonne silver and 0.581 per cent copper (Assessment Report 15338).
In 1988, two chip samples (33218 and 33222) of quartz veining with malachite, pyrite and chalcopyrite hosted by volcanic tuff and breccia near its contact with an andesitic porphyry yielded 7.80 and 3.50 grams per tonne gold, 7.6 and 90.0 grams per tonne silver with 0.378 and 1.130 per cent copper, respectively, over 0.15 metre each (Assessment Report 18536).
Two samples taken from this showing in 1990 yielded elevated assay results. Grab sample JD-046 analysed 0.11 gram per tonne gold, 1.3 grams per tonne silver and 1.61 per cent copper (Assessment Report 20671). Grab sample JD-047, a frost-heave sample, presumably from the same vein as sample JD-046, analysed 3.77 grams per tonne gold, 7.2 grams per tonne silver and 1.64 per cent copper (Assessment Report 20671).
Also at this time, a chip sample (JD-010) from a silicified shear zone in a propylitic-altered andesite with chalcopyrite and pyrite, located approximately 150 metres to the southwest, yielded 0.465 gram per tonne gold, 5.2 grams per tonne silver and 0.195 per cent copper, whereas a grab and chip samples (DO-106, DO-121 through -130) of a quartz-veined andesitic volcanic with pyrite and chalcopyrite, located approximately 200 to 350 metres to the northeast, yielded values of up to 0.485 gram per tonne gold, 19.5 grams per tonne silver, 0.887 per cent lead and 1.398 per cent copper (Assessment Report 20671).
In 2004, a 0.1-metre chip sample (148902) from a brecciated quartz vein with chalcopyrite and malachite assayed 22.61 grams per tonne gold, 16.6 grams per tonne silver and 0.723 per cent copper (Assessment Report 27638).
In 2005, a 0.9-metre chip sample (64641) from a quartz vein with pyrite, trending 320 to 340 degrees and traced for greater than 400 metres along strike, yielded 13.00 grams per tonne gold, 13.6 grams per tonne silver and 0.129 per cent copper, whereas three other chip samples (64639, 64640 and 64642) yielded from 1.36 to 12.10 grams per tonne gold, 5.1 to 27.6 grams per tonne silver and 0.236 to 0.687 per cent copper (Assessment Report 28039).
Work History
A number of samples were taken in the vicinity of the Joanna East showing by Stealth Minerals in 2004. Stealth held these occurrences within Gordo group of claims which stretched to the east over the Joanna and Falcon occurrences. See Joanna West (094E 175) for further details of the Stealth work and for work done on the Joanna property in the 1980s.
