The Joanna Gold occurrence is located at an elevation of approximately 1850 metres on a west-trending ridge, approximately 1.5 kilometres southeast of Mount Gordonia. The prospect is 290 kilometres north of Smithers. It lies within the Omineca-Cassiar mountains in the north-central portion of the Toodoggone gold camp.

The Joanna Gold prospect 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.

The oldest rocks observed at the prospect 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). One small quartz monzonite outcrop, of probable Early to Middle Jurassic age, is located just to the north of the Joanna Gold prospect. Toodoggone volcanics are exposed on the southwest and west ridges of Mount Gordonia, immediately to the north.

Propylitic alteration is widespread throughout the area surrounding the Joanna Gold prospect, 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).

A 20-centimetre wide by 250-metre long quartz vein, hosting fine pyrite and malachite staining comprises the Joanna Gold prospect.

In 1985, a rock sample, taken approximately 250 metres to the northwest, assayed 3.00 grams per tonne gold, 10.3 grams per tonne silver and 2.63 per cent copper (Assessment Report 14765).

In 1986, a chip sample (JS-86-0009) from an outcrop of massive specular hematite, located approximately 300 metres to the west, assayed 23.4 grams per tonne silver, 6.09 per cent zinc and 0.44 per cent copper over 1.0 metre, whereas a nearby sample (TA-86-003) assayed 7.3 grams per tonne silver, 0.37 per cent zinc and 0.65 per cent copper (Assessment Report 15338). Also at this time, a sample (TA-86-0001) of frost-heaved quartz with malachite, located approximately 300 metres to the southwest of the previous samples, assayed 42.1 grams per tonne silver, 2.42 per cent zinc and 0.41 per cent copper (Assessment Report 15338).

In 1988, a chip sample (18440) of quartz-veined andesite with malachite and pyrite assayed 0.571 per cent copper, 2.9 grams per tonne silver and 4.31 grams per tonne gold over 1.00 metre, whereas another chip sample (18447) of porphyry hosting a 3-centimetre wide quartz vein, located approximately 250 metres to east-southeast, yielded 0.13 gram per tonne gold, 7.6 grams per tonne silver and 0.521 per cent copper (Assessment Report 18536).

In 1990, a grab sample (DMH-003) of limonite-malachite-azurite–altered quartz veining with chalcopyrite and pyrite assayed 4.235 grams per tonne gold, 6.5 grams per tonne silver and 0.366 per cent copper, whereas a 1.0-metre chip sample (DMH-004) yielded 0.105 gram per tonne gold, 3.3 grams per tonne silver and 0.841 per cent copper (Assessment Report 20671). These samples were taken on strike to the south of the previous chip sample 18440.

Also at this time, a grab sample (JD-038) of gossanous and propylitic-altered andesite with quartz veinlets hosting disseminated chalcopyrite and pyrite, located approximately 450 metres to the northeast, yielded 0.330 gram per tonne gold, 10.9 grams per tonne silver and 0.179 per cent copper over 0.40 metre, whereas a scree sample (DAR-001) of propylitic-altered andesite with 80 per cent hematite and minor malachite, azurite, chalcopyrite, pyrite, arsenopyrite and quartz-carbonate veining, located downslope to the southwest, yielded 0.075 gram per tonne gold, 17.6 grams per tonne silver, 0.298 per cent copper and greater than 2.00 per cent zinc (Assessment Report 20671).

Work History

The area has been explored on conjunction with the Joanna West (MINFILE 094E 175) occurrence and a completed exploration history for the Joanna property can be found there.