The Extra mineral showings are located on Extravagant Creek, approximately 2.3 kilometres northwest of Tahsis.
Regionally, the Extra showings are located in a broad, northwest trending belt of sedimentary and volcanic rocks of the upper Triassic Vancouver Group. This is comprised of the Karmutsen Formation, the Quatsino Formation and the Parsons Bay Formation. The Karmutsen is a thick package of regionally extensive pillow basalt, flows and breccias. The overlying Quatsino Formation is comprised of massive to thickly bedded limestone. Where intruded, it is often altered to coarse white marble. The uppermost unit of the Vancouver Group is the Parson's Bay Formation. This is comprised of interbedded calcareous sediments and limestone. Intruded into the sequence are intermediate plugs and stocks of the Jurassic Island Intrusive Suite (Catface Intrusions). In the Tahsis area the Vancouver Group rocks are intruded by medium to coarse-grained diorite of the Extravagant Stock. This is a northwest trending, elongate body that extends from tidewater just north of Tahsis, is 1 to 2 kilometres wide, and terminates about one kilometre northwest of the showings.
At the Extra showings, the regional section is present at a smaller scale. The sedimentary and volcanic units dip moderately to the southwest exposing Karmutsen basalt to the northwest, Quatsino Formation limestone, and then Parson's Bay Formation calcareous sediments in the southwest. A body of diorite, probably related to the Extravagant stock, ranging from 200 to 400 metres across, cuts northwest through the middle of the Quatsino Formation Limestone. The full length of the body is not known but is seen to extend for at least 1800 metres. On the west side, a zone of skarn-altered rock extends from the showings for 900 metres to the southeast. The main showings are at the north end of the skarn. Associated alteration includes extensive hornfelsing of the sediments and recrystallization of limestone to marble.
Mineralization is located within both exo- and endo- skarn at the contact with the intrusion. In general, exoskarn is comprised of garnet, actinolite and diopside. Endoskarn, primarily garnet with minor clinopyroxene (?) is developed at the adit zone.
North of the Adit zone are two arms of coarse, white marble with associated exoskarn that 'penetrate' the intrusion. Mineralization consists of sulphides up to 10 per cent by volume, comprised of chalcopyrite with lesser, variable amounts of pyrite and pyrrhotite.
Work History
The occurrences were originally discovered and explored by Wm. Poole in 1922. There is no specific information regarding development at that time. Evidence of work from around that time is one adit, several hand trenches and prospect pits. Circa 1922 there was a lot of development and exploration related to the Star of the West occurrence (092E 010) just north of Tahsis. Modern work in the area began in 1955 and continued sporadically through to 1970, centred on the Star of the West. General geophysics, prospecting and mapping were done but the information has been lost and it is not known if the work extended as far as the Extra showings.
The Extra claims were located in 1990 by prospectors David Nelles and Hamish MacFarlane. In 1991, the claims were optioned to Langdon Resources and a geological, geophysical and drilling program was carried out that year. The option was dropped the following year. In 2006, G. Diakow completed a prospecting program on the claims which identified five areas of sulphide mineralization, including the former adit. In 2007, Grande Portage Resources completed a regional geochemical program on the area as the Cherry Property. In 2011, Gold Ridge Exploration completed a regional geochemical sampling program on the Tahsis Property.
A best assay of chalcopyrite-rich skarn yielded 3.57 grams per tonne gold, 38.7 grams per tonne silver and 14.1 per cent copper (X90-D007, PF Langdon Prospectus). This is similar to historical "high grade" or select samples. Other mineralized rock and float samples taken in 1990 had ranges from trace gold, silver and copper to 10.8 grams per tonne gold, 20.0 grams per tonne silver and 7.97 per cent copper. Grades are erratic and scattered through the skarn. Two diamond drill holes were placed to test IP anomalies near the surface mineralization. The results were poor compared to the mineralized surface samples. Both holes hit intercalated limestone and intrusion with skarn but the few assay samples taken returned low values. Best values from different sections in hole one were 75 parts per billion gold, 0.2 parts per million silver and 580 parts per million copper. Hole two had lower results (Assessment Report 20664). In 2006, a sample from a diorite plug enclosed in limestone, 300 metres to the southeast of the former adit, yielded 0.488 grams per tonne gold, 13.7 grams per tonne silver and greater than 10,000 parts per million copper (Assessment Report 28652).
In 2013 and 2015, Mammoth Geological Ltd. completed programs of prospecting, geological mapping and geochemical (rock, stream sediment and soil) sampling on the North Block (including the Extra) and South Block of the Tahsis property for Sojourn Ventures Inc. A sample from a rusty shear zone, located in the general area of the Extra occurrence, assayed 0.338 per cent copper (Henneberry, R.T. (2018-02-05): 43-101 Techincal Report – Tahsis Property).
In 2017, Qualitas Holdings Corp. completed a minor program of rock sampling on the Tahsis property and Mammoth Geological Ltd. completed a NI43-101 Technical Report for the Tahsis property. In 2018 and 2019, Cross River Ventures Corp. completed a program of soil sampling and a 5.5 line-kilometre induced polarization survey on the Tahsis property. Soil geochemical surveys returned scattered anomalous gold and copper values. One road soil sample collected approximately 900 metres southeast of the Extra showing, returned values of 0.174 gram per tonne gold and 0.27 per cent copper.
