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File Created: 24-Jul-85 by BC Geological Survey (BCGS)
Last Edit:  20-Jul-07 by Sarah Meredith-Jones(SMJ)

Summary Help Help

NMI 094N4 Ba 1
Name BV, MUNCHO LAKE BARITE, AV, BV 9, SULPHUR CREEK Mining Division Liard
BCGS Map 094N002
Status Developed Prospect NTS Map 094N04E
Latitude 59º 04' 04" N UTM 10 (NAD 83)
Longitude 125º 41' 31" W Northing 6550710
Easting 345672
Commodities Barite Deposit Types E10 : Carbonate-hosted barite
Tectonic Belt Foreland Terrane Ancestral North America
Capsule Geology

The BV prospect is a large, high grade stratiform barite deposit in the Sentinel Range of the Northern Rocky Mountains, 6 kilometres east-northeast of the northern end of Muncho Lake, which is on the Alaska Highway. The deposit was first mapped and sampled by Delta Explorations Limited in 1967. Teslin Exploration Limited conducted detailed engineering and economic studies in 1970.

The region is underlain by Proterozoic to Middle Devonian sedimentary rocks belonging to Ancestral North America (Geological Survey of Canada Open File 673, Map 1713A). The BV claims are underlain mainly by the Devonian Wokkpash, Stone and Dunedin formations. The rocks are designated differently in Assessment Report 1682.

The Lower Devonian Wokkpash Formation (mostly equivalent to the Yellow unit in Assessment Report 1682) is composed of yellow-weathering, fine-grained dolostone and limestone, dolomitic quartz sandstone and siltstone, and minor solution breccia. The uppermost part is distinctly red-weathering. The overlying Middle Devonian Stone Formation (equivalent to the Arnica Formation in Assessment Report 1682) is pale grey-weathering, very fine-grained dolostone and dolostone breccia. It is about 640 metres thick in the region. This unit is overlain by the Middle Devonian Dunedin Formation (probably equivalent to the Nahanni Formation in Assessment Report 1682), comprising well-bedded fossiliferous limestone.

A few broad folds and gently west-dipping thrusts characterize the structure of the area (Assessment Report 1682). The area around the BV occurrence is dominated by two north-northwest striking thrusts. The McMechan Creek thrust carries a panel of mainly Wokkpash and Stone formation rocks. The footwall comprises the same units. Two kilometres to the east, these rocks are emplaced on the Dunedin Formation by the Barite Creek thrust. Bedding varies but generally strikes north, with gentle to moderate westerly dips.

The barite deposit is well-defined stratigraphically. Applying the stratigraphic terminology given above to the available information, bedded, stratiform barite apparently occurs at the base of the Stone Formation, immediately above the Wokkpash Formation. The deposit has a lensoidal, plano-convex shape, dipping about 30 degrees west, with a flat base and a convex upper surface. The deposit is well exposed on a southeast-facing slope, the largest mappable dimension, along the strike, being about 4000 metres. The barite beds, up to 4.75 metres thick, are separated by beds of grey dolostone which locally contain blebs of barite. Overall, the deposit is about 32 metres thick in the centre of the lens, about 60 per cent of which is high grade barite. The barite is most commonly massive, white and coarse grained. Some layers consist of fibrous barite which grew as an array into open space on corroded dolostone (National Mineral Inventory). Very coarse-grained calcite is associated with barite in the interstices of solution breccias.

The barite was considered to be formed by a secondary replacement of the host rocks, primarily because of sharp lateral changes from grey dolostone to massive white barite (Assessment Report 1682). Other, minor forms of barite, namely as a cement in dolostone breccia and as veins in dolostone, also indicate a secondary origin.

Barite deposits are present in both the McMechan Creek and Barite Creek thrust sheets. Claims BV 14 and 15 are in the former; claims BV 1 to 13 are in the latter. It is speculated that the deposit was originally continuous before being offset by the McMechan Creek thrust (Assessment Report 1682).

The barite content of the deposit has been evaluated in part of claim BV 9. Results showed that one zone assayed 80 per cent barite (BaSO4) over 3 metres, and another, 18-metre wide zone averaged 65 per cent BaSO4 (Assessment Report 1682). Based on these results, and assumptions regarding the shape of the deposit and minimum mining width, an inferred "tonnage" or resource of 100 million tonnes was derived, with an indicated grade of 65 per cent BaSO4 (Assessment Report 1682, pages 22, 23). A more detailed mining feasibility study was done in 1970 (Assessment Report 3078).

Bibliography
EMPR ASS RPT *1682, 3078
EMPR OF 1997-16
GSC BULL 186
GSC MAP 1713A
GSC OF 673

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