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File Created: 24-Jul-1985 by BC Geological Survey (BCGS)
Last Edit:  26-Mar-2022 by Nicole Barlow (NB)

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NMI 092J15 Au6
Name FORTY THIEVES (L.443), BRIDGE RIVER CONSOLIDATED, URAL (L.442), ELEPHANT (L.444) Mining Division Lillooet
BCGS Map 092J086
Status Developed Prospect NTS Map 092J15W
Latitude 050º 49' 55'' UTM 10 (NAD 83)
Longitude 122º 50' 15'' Northing 5631149
Easting 511444
Commodities Gold, Silver, Copper Deposit Types I01 : Au-quartz veins
Tectonic Belt Coast Crystalline Terrane Bridge River, Cadwallader
Capsule Geology

The Forty Thieves vein is hosted in andesites of the Upper Triassic Pioneer Formation, Cadwallader Group which is closely associated with diorite of the Permian Bralorne Igneous Complex; the rocks interfinger complexly and the diorite is suggested to be replacing the andesite rather than intruding it. The indistinct boundary between andesite-diorite is intruded by a Late Tertiary (?) 30 metre wide dacite porphyry dyke. The western boundary of the andesite-diorite is a west-dipping fault contact with a narrow belt of serpentinized peridotite of the President Ultramafics (correlative with the Permian and older Shulaps Ultramafic Complex).

The vein follows the main structural trend, striking northwest and dipping northeast along a 600-metre-long fissure (reverse fault) through the andesite, diorite and dacite porphyry. The vein consists of long lenses of quartz with a width of about 1 metre averaged along the shear. Pyrite, tetrahedrite and lesser chalcopyrite occur as streaks and disseminations, with malachite and azurite staining. In other parts, cloudy grey quartz surrounds altered wallrock inclusions containing stockworks of ankerite, sericite, chlorite and pyrite. The average assay obtained from vein quartz assays less than 0.34 gram gold per tonne, with similar values for wallrock samples (Minister of Mines Annual Report 1946, page 111). The Forty Thieves vein is reported to be very similar to the Arizona vein located nearby (see 092JNE024).

EMPR AR 1897-556; 1898-1194; 1899-726; 1900-908; 1903-189; 1913-K262; 1916-268; 1928-218; 1931-112; 1932-219; 1933-267; 1944-55; 1945-86; *1946-106; 1959-28; 1960-23; 1961-27
EMPR ASS RPT 12305, 14664, 14665
EMPR BULL 1, p. 77; 3, p. 35
EMPR EXPL 1977-E169; 1978-E178; 1979-185; 1980-260
EMPR FIELDWORK 1974, p. 35; 1985, pp. 303-310; 1986, pp. 23-29; 1987, pp. 93-130; 1988, pp. 105-152; 1989, pp. 45-72; 1990, pp. 75-83
EMPR Inspections Branch File #60160
EMPR OF 1987-11; 1988-3; 1989-4; 1990-10
EMPR PF (Report by S.F. Kelly, 1977)
GSC MEM 130, p. 84; 213, pp. 88,91
GSC OF 482
GSC P 43-15; 73-17
GSC SUM RPT 1915, p. 82
CJES 1987, Vol. 24, pp. 2279-2291
GCNL #25, 1985
Talisker Resources Ltd. (2020-09-02): NI 43-101 Technical Report, Bralorne Gold Project, Bralorne, British Columbia, Canada