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File Created: 09-Mar-1986 by John Bradford (JB)
Last Edit:  06-Jun-2023 by Karl A. Flower (KAF)

Summary Help Help

Name MCDAME, CASSIAR (MCDAME) Mining Division Liard
BCGS Map 104P031
Status Past Producer NTS Map 104P05W
Latitude 059º 19' 19'' UTM 09 (NAD 83)
Longitude 129º 48' 56'' Northing 6576186
Easting 453583
Commodities Asbestos Deposit Types M06 : Ultramafic-hosted asbestos
Tectonic Belt Omineca Terrane Cassiar, Slide Mountain
Capsule Geology

The McDame deposit is located approximately 1 kilometre from the Cassiar deposit (MINFILE 104P 005), north-northeast of the Cassiar town site and 100 kilometres north of the community of Dease Lake.

The area is underlain by four major thrust sheets, distinguished on McDame Mountain, of the Devonian to Triassic Sylvester Allochthon. These comprise greenstones, argillites, limestones, ultramafites and ultramafic bodies of variable size, shape and form. Bodies of serpentinized peridotites occur along at least three distinct horizons that are probably major thrust fault surfaces. The lowest horizon occurs just above the Sylvester basal thrust fault, and contains a serpentinite thrust slice that hosts the Cassiar (MINFILE 104P 005) and McDame deposits. The ultramafite sheet dips 32 to 50 degrees east under McDame Mountain, where it attains a thickness of 300 metres. There are two episodes of faulting postulated, with asbestos thought to have formed during the change from normal to dextral motion on a north-trending fault that transects the serpentinite (45 degree shear).

The hangingwall of the McDame ultramafite is marked by shearing, serpentinization, chloritization, pods of schistose tremolite, talc soapstone, zoisite, epidote and clay. The footwall is characterized by sheared carbonaceous argillite and gouge. Pyrite and magnetite are disseminated throughout.

Chrysotile veining is controlled primarily by the joint system. Joint sets in the serpentinite strike east-northeast and south-southeast. Normal faulting is prominent in an east and northeast direction. The McDame deposit is the downward extension of the Cassiar deposit.

Drilling has outlined an east-dipping body of crossfibre chrysotile ore that thickens towards the east. Reserves have been calculated for a deposit having the approximate dimensions of 540 metres dip length (east-west), 320 metres width (north-south), and 15 to 150 metres thickness. Measured geological reserves are 19.94 million tonnes with a 6.21 per cent mill yield of asbestos (Princeton Mining Corp. Annual Report 1990).

Production at the McDame deposit began in February 1991 after three years of underground development, prompted by declining reserves from open pit operations at the adjoining Cassiar asbestos mine. Production up to October 1991 totalled 40,000 tonnes (George Cross News Letter No.200, 1991). The ore averaged 9.2 per cent asbestos fibre, suggesting a higher overall grade than expected (Northern Miner - February 11, 1991).

In 1989, high quality asbestos underground reserves in the McDame deposit were estimated at 16 million tonnes (10 years of production; P. Wojdak, personal communication, 1994).

Work History

The area has been explored in conjunction with the adjacent Cassiar Asbestos Mine (MINFILE 104P 005) and a complete exploration history can be found there.

EMPR ASS RPT 91, 9525, 10655, 13628, 13820, 15702, 16776
EMPR ENG INSP Annual Report 1989, 1990
EMPR EXPL 1988-B173-176
EMPR FIELDWORK 1979, pp. 80-88; 1987, pp. 245-248; 1988, pp. 323-337
EMPR INF CIRC 1986-1, pp. 26,87; 1987-1, pp. 9,75; 1988-1, p. 73; 1989-1, p. 18; 1990-1, pp. 25,28; 1991-1, p. 40
EMPR MINING 1975-1980, p. 41; 1981-1985, p. 52; 1986-1987, p. 78; 1988, p. 78
EMPR MP MAP 1992-13
EMPR OF 1989-9; 1992-1; 1992-3; 1992-9; 1995-25; 1996-11
EMPF PF (Notice of Annual Meeting of Shareholders, March 1988; Cassiar Mining Corporation, date unknown; Cassiar Mining Corp. Annual Report 1987; Press Releases, Mar.17,21, Apr.25, May 30, June 16, Jul.19,27, 1988; First Quarter Report to Shareholders, May 1988, Cassiar Mining Corp.; Cassiar Mining Corporation Annual Reports 1986, 1987, 1988, 1989, 1990 (excerpts) in 104P 005 - Cassiar File)
GSC MEM 194; 319
GSC MAP 381A; 1110A
GSC OF 2779
GCNL #174, 1984; #26,#78,#158, 1985; #37, #125, #217, 1986; #230, 1989; *#14, #200, 1991
N MINER Sept.13, 1984; Apr.25, 1985; June 16, Nov.24, 1986; Jan.2, 1989; Jan.15,22, May 14, Aug.30, 1990; Feb.11, Mar.18,25, Apr.1, May 13, Oct.7,28, 1991; Feb. 1,17, Mar.30, 1992
N MINER MAGAZINE Vol.4, No.11 (Nov. 1990)
MINING IN BRITISH COLUMBIA Jan/Feb 1991, Vol. 2, No. 1, pp. 8-11
Burgoyne, A.A. (1985): CIM Annual General Meeting, April 22, 1985 Geology and Exploration, McDame Asbestos Deposit, Cassiar, B.C. (also in Property File)
Harms, T.A. (1986): Structural and Tectonic analysis of the Sylvester Allochthon, Northern British Columbia: Implications for Paleogeography Accretion, Ph.D. Thesis, University of Arizona
Falconbridge File