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File Created: 24-Jul-85 by BC Geological Survey (BCGS)
Last Edit:  21-May-14 by Nicole Barlow(NB)

Summary Help Help

NMI 092O2 Au1
Name ROBSON, BONANZA, PEARSON Mining Division Lillooet
BCGS Map 092O006
Status Past Producer NTS Map 092O02W
Latitude 51º 01' 23" N UTM 10 (NAD 83)
Longitude 122º 53' 20" W Northing 5652395
Easting 507793
Commodities Gold, Silver, Lead, Zinc, Copper Deposit Types I05 : Polymetallic veins Ag-Pb-Zn+/-Au
Tectonic Belt Intermontane Terrane Cadwallader
Capsule Geology

The Robson polymetallic vein prospect is situated 3.5 kilometres northwest of Eldorado Mountain, approximately 17 kilometres north of Gold Bridge and 11 kilometres northwest of Tyaughton Lake.

The area is underlain by thick siltstone to sandstone turbidite sequences of the Upper Triassic Hurley Formation. The Hurley turbidites are juxtaposed against Lower Cretaceous Taylor Creek Group conglomerates and interbedded fine sandstone to shales. A diorite to quartz diorite Upper Cretaceous Coast Crystalline Complex intrusion, measuring approximately 5 by 4 kilometres, dominates the centre of the Eldorado property and Robson showing.

The showing lies within hornfelsed and altered sedimentary rocks (including calcarenite, sandstone and shale) of the Upper Triassic Hurley Formation occurring along the northwest margin of an apophysis of the Paleocene Eldorado granodiorite pluton.

Mineralization in the immediate area is dominated by visible arsenopyrite, pyrite, minor chalcopyrite, sphalerite and stibnite, and occurs within and along the margins of quartz ± carbonate veins as disseminations and along fractures in quartz diorite and turbiditic, hornfelsed sediments. Gold is common throughout and likely associated with arsenopyrite, pyrite and/or stibnite mineralization. The Robson prospect consists of seams and veins of predominantly auriferous arsenopyrite and quartz along a southwest-trending and steeply dipping shear zone that seems to be part of a set of fractures radiating from the pluton. The vein seems to partly grade into the decomposed and altered granodiorite and related porphyritic dikes. Other metallic minerals present include pyrite, jamesonite, sphalerite, chalcopyrite, stibnite, boulangerite, pyrrhotite and pyrargyrite. Silica, carbonate and chlorite alteration are associated with the mine.

Sometime prior to 1912, numerous gold-bearing sulphide veins in the Eldorado Mountain and Bonanza Basin areas were prospected by sluicing and open trenching. In 1912, a Mr. Pearson explored small arsenopyrite veins on the Bonanza Creek claims. Exploration continued to increase in the area and, by the 1930s, numerous adits had been driven along arsenopyrite veins in the Taylor, Eldorado and Bonanza basins. Prior to 1939, a 6.1-metre-long adit had been excavated and the claim owners were reportedly shipping approximately 1.8 tonnes of ore per day (Geological Survey of Canada, Paper 43-15, pages 27 to 28).

The first official record of work on the Robson vein was from 1940 by the J.G. Mining Company. Bralorne Mines later optioned the property. Work completed by Bralorne included repairing an old 21.3-metre-long adit and extending it 39.6 metres, facing a second adit and advancing it 12.2 metres and diamond drilling a total of 213.4 metres, as well as considerable open-cut work.

Between 1967 and 1969, Bridge River United Mines Limited carried out an exploration program of geological mapping, geochemical sampling, trenching and electromagnetic geophysical surveying. Exploration continued from 1975 to 1976, when Chevron Standard Limited completed a program of geological mapping and soil grid sampling.

The property was later acquired by Mutual Resources Incorporated in 1979. The company began extensive road building and trenching, though the location of the trenches is unknown because they were never properly marked on maps included in the assessment reports. In 1985, Mutual Resources optioned the property to Cinnabar Resources Limited. Exploration that year consisted of detailed geophysical and geochemical surveying over areas with anomalous gold, silver, arsenic and stibnite values. Three short 0.3-metre channel samples were taken from the Robson trench. The following year, Mutual Resources drilled five diamond drill holes totalling 152 metres. Three of the five holes intersected the Robson veins.

The property was later acquired by Ken Shannon in 1999. In 2005, Rudi Durfield conducted prospecting and silt sampling over the Bonanza Gold project area, including the Robson claim. The follow year, Durfield carried out geological mapping, hand trenching and rock sampling in the Robson trench and adit area as part of an exploration program on the surrounding Bonanza Finger property. The Bonanza Finger property then became known as the Eldorado Gold project and, in 2008, Mel Stewart and Rudi Durfield collected silt and rock samples over the project area and the Robson claim.

In 2009, J. Drobe completed a geological and geochemical evaluation of the Robson Gold property on behalf of Ken Shannon. Work that year consisted of geological mapping, prospecting and rock-chip sampling.

In 2011, GFE Exploration Corporation, a subsidiary of Gold Fields Limited, optioned the property from Ken Shannon. Exploration that year consisted of geological mapping, prospecting, talus fine- and stream-sediment sampling and diamond drilling. One NQ2 diamond drill hole totalling 367.89 metres was drilled to test the validity of surface gold geochemical anomalies.

In 2012, Mel Stewart and Rudi Durfield conducted a program of geological mapping, prospecting and geochemical sampling on the surrounding Eldorado property.

The deposit was mined in 1939 and 1940, producing a total of 34 tonnes of ore that yielded 18 kilograms of silver, 2.2 kilograms of gold, 193 kilograms of copper and 2640 kilograms of lead (Assessment Report 14428).

In 1986, a 0.79-metre diamond drill interval assayed 468.95 grams per tonne silver and 45.24 grams per tonne gold (Assessment Report 15119).

From the 2011 drill program, drillhole ELD11-03 intersected 31.7 metres of 0.741 gram per tonne gold (Assessment Report 32974, page 26).

Bibliography
EMPR AR 1933-A269; 1940-A59; 1967-129; 1968-161
EMPR ASS RPT 5659, *6002, *9062, *14428, *15119, 28124, 28825, 30065, 31402, 32974, 34118
EMPR BC METAL MM00248
EMPR EXPL 1975-E118, E119; 1976-E130, E131; 1979-194; 1986-C283, C284
EMPR FIELDWORK *1988, pp. 115–130; 1987, pp. 105–123; 1986, pp. 23–29
EMPR GEM 1969-185,186
EMPR OF *1989-3; *1988-9; 1988-16
EMPR PF (Property description by B.N. Church, 1990)
EMR MP CORPFILE (International Space Modules Ltd.)
GSC MAP 29-1963
GSC MEM 130 (Map 1882)
GSC OF 534; 2207
GSC P 43-15, pp. 27, 28
GSC SUM RPT 1912, pp. 206, 207

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