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File Created: 24-Jul-85 by BC Geological Survey (BCGS)
Last Edit:  05-Dec-13 by Karl A. Flower(KAF)

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NMI 092F14 Au1, Cu1
Name DOMINEER (MOUNT WASHINGTON), MOUNT WASHINGTON (DOMINEER), DOMINEER, LAKEVIEW, MWC, DJV, WEST GRID Mining Division Nanaimo
BCGS Map 092F074
Status Developed Prospect NTS Map 092F14W
Latitude 49º 45' 30" N UTM 10 (NAD 83)
Longitude 125º 18' 00" W Northing 5514300
Easting 334348
Commodities Gold, Silver, Copper, Lead, Zinc, Molybdenum Deposit Types H04 : Epithermal Au-Ag-Cu: high sulphidation
L04 : Porphyry Cu +/- Mo +/- Au
Tectonic Belt Insular Terrane Wrangell, Plutonic Rocks
Capsule Geology

The Domineer epithermal deposit comprises the Domineer, Lakeview and West Grid zones. The deposit lies 400 metres south of the Mount Washington Copper open pit (see 092F 117). The centre of the Lakeview zone is located 510 metres to the west of the Domineer zone, and the West Grid zone lies about 200 metres northwest of the Lakeview. The zones form a continuous shallow-dipping tabular body of argillic alteration containing discontinuous, en echelon or stacked lenses of mineralization.

A complete exploration history of the area and associated occurrences can be found Assessment Report 30010.

The mineralized zone occurs within a sub-horizontal package of Tertiary pyroclastics and underlying clastic sediments of the Upper Cretaceous Nanaimo Group (Comox Formation), which unconformably overlie mafic volcanic rocks of the Upper Triassic Vancouver Group (Karmutsen Formation). Intruding both formations is a Late Eocene to Early Oligocene quartz diorite stock of the Mount Washington Intrusive Suite (formerly Catface Intrusions - Nick Massey, Personal Communication, May 1990), dated at 35 million years (+/- 6 million years) (Carson, 1960). Several later breccia events are imposed on all other rock types locally.

The Karmutsen Formation comprises basaltic massive and pillow lavas that are commonly porphyritic. The lavas grade into pillow breccias and aquagene tuffs. The overlying Comox Formation comprises fine-grained sandstone and greywacke, with interbedded siltstone, carbonaceous shale and minor coal. A basal conglomerate of rounded clasts separates the formations.

The Tertiary quartz diorite stock is variably porphyritic and is centred on McKay Lake northeast of the summit of Mount Washington. Several sills and dykes of quartz diorite and quartz diorite porphyry are related to the stock.

Late breccia events include the Washington, Murray, Glacier, Murex (092F 206) and Oyster (092F 365) breccias; others may also be present. Of these, the Washington breccia is the youngest and is located near the Domineer zone on a ridge north of Mount Washington. The Murex breccia, located east of the Domineer deposit, is the largest and most complicated of the breccias. Other breccias and diatremes are located 2 kilometres north and 2 kilometres east of Mount Washington.

Contact relationships of the Washington breccia with the Murray breccia, the Glacier breccia and quartz diorite are crosscutting but gradational, and are often characterized by vertically oriented crackle breccia zones. Within the Washington breccia, large angular clasts dominate over a matrix of finely pulverized rock flour, which has locally been replaced by magnetite and actinolite. Slab-like fragments, with length to width ratios of 10:1 are common, and suggest that subvolcanic collapse may have been the operative process.

Capping the west arm of Mount Washington is the tabular Murray breccia which generally contains a much higher matrix component than the other breccias, although considerable variability exists. Clasts are generally subrounded to subangular and range in size from 1 to 10 centimetres, averaging about 2 centimetres. The composition of clasts is mixed and consists of varieties of quartz diorite, sandstone, siltstone and mafic volcanics. Overlying, and in places adjacent to the Murray breccia, is a crackle breccia. The Murray breccia, which is bedded and locally displays shrinkage cracks and slump folds, has recently been identified as a coarse pyroclastic deposit with associated thinner beds of fine-grained tuff (Dahl, 1989).

Mineralization at the Domineer deposit has a defined strike length of 1.5 kilometres and an average width of 61 metres. Diamond drilling indicates that mineralization extends from the Domineer zone to the Lakeview-West Grid area. Mineralization consists of a tabular zone of alteration containing a stockwork of auriferous quartz- pyrite-arsenopyrite veins and lenses. The zone occurs within one of several subhorizontal fractures and breccias which post-date the Tertiary intrusions and volcanic activity, and may represent either thrust faults or decollements (Muller, 1989).

Enveloping the quartz-sulphide veins and lenses, is a zone of pervasive kaolinite alteration. A 2 to 5 metre wide zone of hydrothermal breccia usually lies at the centre of the alteration zone. This breccia consists of angular clasts of altered wallrock in a matrix of quartz and sulphides. Locally, the sulphides envelop these clasts and exhibit a banded appearance. Away from the central alteration zone is a stockwork of smaller quartz-sulphide veins. With increasing distance the veins decrease in size and frequency, alteration becomes limited to vein selvages and chlorite becomes the dominant alteration mineral.

The dominant sulphide minerals within the gold zone are pyrite and arsenopyrite. Chalcopyrite, covellite, sphalerite, galena, bornite, tennantite, wehrlite, hessite, chalcocite, realgar and orpiment are also present in varying amounts. Pyrrhotite, molybdenite and magnetite are present in the general vicinity but appear to be unrelated to the gold-bearing mineralization.

Two high grade pods have been identified. A northern pod, centred on the Domineer showing, averaged 6.99 grams per tonne gold and 58.63 grams per tonne silver over an average thickness of 1.6 metres. The southern pod, centred 180 metres to the south of the northern pod, averaged 7.06 grams per tonne gold and 45.26 grams per tonne silver over an average thickness of 2.56 metres (Assessment Report 18472).

Underground exploration and surface diamond drilling to August 1989 have established drill indicated reserves of 550,298 tonnes grading 6.75 grams per tonne gold and 32.23 grams per tonne silver and 0.57 per cent copper (Open File 1992-1; George Cross News Letter - August 3, 1989).

In 1991, Better Resources completed a program of geochemical sampling and six diamond drill holes, totalling 602 metres, to test the extensions of the mineral zone intersected by Noranda in 1989. In 1992, Better Resources closed the adit in the Lakeview-Domineer Zone and reclaimed the waste dumps outside. In 2008, Blue Rock Resources completed a geological mapping and prospecting program. In 2011, Clibetre Exploration completed a program of geochemical sampling and fifteen holes, totalling 64.8 metres, of overburden drilling on former tailings located 6 kilometres to the east.

Bibliography
EMPR AR 1956-119; 1957-69; 1959-135; 1960-111; 1961-102; 1962-105;
1963-103; 1964-155,157; 1965-235; 1966-71; 1968-101
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*12605, 14085, *14705, 15228, *15395, 15526, 15776, 15825, 15826,
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1987; Jan.19, 1988; Aug.3, Sept.12, 1989
W MINER Nov. 1965, p. 35; Nov. 1967, pp.35-40
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