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File Created: 19-Jan-90 by Steve B. Butrenchuk(SBB)
Last Edit:  20-Oct-94 by Chris J. Rees(CRE)

Summary Help Help

NMI
Name MO Mining Division Liard
BCGS Map 094N002
Status Developed Prospect NTS Map 094N04E
Latitude 59º 05' 56" N UTM 10 (NAD 83)
Longitude 125º 41' 15" W Northing 6554162
Easting 346067
Commodities Barite Deposit Types E10 : Carbonate-hosted barite
Tectonic Belt Foreland Terrane Ancestral North America
Capsule Geology

The Mo developed prospect is a stratabound barite deposit, situated at the headwaters of a tributary of Sulphur Creek in the Sentinel Range of the Northern Rocky Mountains. It is 8.5 kilometres northeast of the northern end of Muncho Lake, which is on the Alaska Highway.

The rocks in the area are predominantly Lower to Upper Devonian carbonates and shales belonging to Ancestral North America (Geological Survey of Canada Map 1713A). The regional trend is north-northwest, and the rocks have been deformed into broad folds, cut by thrust faults.

The Mo claims are underlain by the Middle Devonian Stone and Dunedin formations (Geological Survey of Canada Open File 673, Assessment Report 7359). The Stone Formation consists of pale grey, very fine grained dolostone, dolostone breccia and dolomitic quartz sandstone. The Dunedin Formation comprises grey, well-bedded limestone and argillaceous limestone, and minor calcarenite and dolostone. Immediately to the east of the claims, a northeast-verging thrust places these rocks on Upper Devonian to Mississippian Besa River Formation black shale.

The Mo deposit consists of a lower, bedded barite zone, and an overlying baritic breccia zone; both are hosted by undivided Stone and Dunedin formation dolostones, probably mainly the former (Assessment Report 7359). The rocks strike north to north-northwest and dip west between 30 and 60 degrees, averaging 35 degrees. A thrust passing through the centre of the claims probably repeats the units, but apparently not the mineralization.

The bedded zone is up to 15 metres thick, and is exposed for approximately 650 metres from the north side of the tributary creek to a point high on the south side; both ends of the zone are cut off by faults. The more important segment is from the creek southwards, a strike length of 350 metres. Individual beds of barite are several centimetres to over 2 metres thick, and are separated by interbeds of mostly non-baritic dolostone. The barite is white, fine grained and laminated. Petrographic study reveals bands of radiating, relatively coarse-grained blades of barite with interstitial secondary calcite, and thin intercalations of green calcareous mudstone. The dolostone interbeds consist of dolomite and interstitial calcite and minor barite, cut by coarsely crystalline calcite-barite veinlets.

The bedded barite is overlain by a much thicker (up to 75 metres thick) and more extensive zone of baritic breccia. The breccia is irregular and consists of angular fragments of dolostone from a few centimetres to over 2 metres across. The matrix is barite and calcite. The breccia is generally coarser and less chaotic towards the base of the zone where it is described as a mosaic breccia.

Samples have been analysed for barite content, presence of contaminating elements, and specific gravity. Samples from the bedded zone range from 3 to 87 per cent barite (BaSO4) (Assessment Report 7359). The breccia zone has sections (in the northern half of the occurrence) ranging from about 4 to 54 per cent BaSO4, reflecting the more erratic nature of the mineralization. This feature was judged to make the breccia not viable for mining, at least south of the creek where the stripping ratio is excessive (Assessment Report 7359).

Preliminary estimates of grade and tonnage potential and stripping ratios have been made for the bedded barite zone (Assessment Report 7359). Potential reserves of barite were estimated at 2.85 million tonnes grading 50.72 per cent BaSO4, assuming continuity of the deposit down dip for 150 metres. North of the creek, and combining the barite breccia with the bedded barite, the estimate was 3.4 million tonnes grading 34.7 per cent BaSO4, assuming a down dip extension of 75 metres. It was considered that only this segment could be exploited by open pit mining because it is more accessible and the stripping ratio is lower here.

Similar deposits in the region, such as the BV developed prospect (094N 002) 3.5 kilometres to the south, have been interpreted as of replacement origin.

Bibliography
EMPR ASS RPT *7359
EMPR EXPL 1979-330
EMPR OF 1997-16
GSC BULL 186
GSC MAP 1713A
GSC OF 673

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