Big Bull
The Big Bull deposit is located approximately 9 km to the south of the Tulsequah Chief deposit and was staked by V. Manville of Juneau in 1929. Massive sulphide ore outcropped in a small creek bed over a width of 2 to 8 metres, and a strike length of about 140 metres. Sporadic drilling and underground work were carried out by various parties until 1946, when Cominco Ltd. acquired the property. Big Bull went into production in August, 1951, and continued until December, 1955, with a total production of 326 658 tonnes grading 1.2% Cu, 1.9% Pb, 7.3% Zn, 5.14 g/t Au and 154 g/t Ag. Tulsequah Chief and Big Bull ores were processed at a common mill.
In 2006 drilling at the Big Bull deposit passed two major milestones: a discovery of a potential new zone of high grade massive sulphide mineralization, dubbed the “60-62” zone and the first NI 43-101 compliant resource estimate on the deposit.
This resource estimate was released on April 2nd, 2007, and was completed by Wardrop Engineering.
Big Bull Resource Estimate(1) (@ CAD $86 NSR cutoff, Wardrop, 2007)
| Resource |
| Category |
Zone(s) |
Tonnes |
Cu (%) |
Pb (%) |
Zn (%) |
Au (g/t) |
Ag (g/t) |
| Indicated |
Main |
211,000 |
0.40 |
1.25 |
3.33 |
3.04 |
161.67 |
| Inferred |
Main |
482,000 |
0.37 |
1.50 |
3.42 |
2.89 |
212.89 |
| |
"60-62" |
187,000 |
0.31 |
5.41 |
12.57 |
7.39 |
148.23 |
| Total Indicated |
All |
211,000 |
0.40 |
1.25 |
3.33 |
3.04 |
161.67 |
| Total Inferred |
All |
669,000 |
0.35 |
2.59 |
5.97 |
4.14 |
194.83 |
| Resource |
NSR(2) |
| Category |
Zone(s) |
$US |
$CDN(3) |
| Indicated |
Main |
144 |
169 |
| Inferred |
Main |
157 |
185 |
| |
"60-62" |
324 |
381 |
| Total Indicated |
All |
144 |
169 |
| Total Inferred |
All |
204 |
240 |
(1) The resource estimate was prepared by Gilles Arseneau, Ph.D., P. Geo of Wardrop Engineering Ltd. The estimate was prepared on March 26, 2007 using Gems Version 6.04, a 3-D block modelling software. Block grades were interpolated using inverse distance weighted to the second power. Resources were classified as indicated mineral resource if the average distance of at least three drill holes was 40 metres or less from the block and mineral resources were classified as inferred if the average distance of at least 3 drill holes was greater than 40 but less than 80 metres of an interpolated block.
(2) NSR was calculated using the same methods and assumptions for metallurgical response as used in the Tulsequah Chief Feasibility Study announced on January 29, 2007.
(3) An exchange rate of $1 USD = $0.85 CDN was applied.
The Big Bull deposit is a polymetallic volcanogenic massive sulphide body hosted by a variably altered sequence of mafic and felsic volcanic flows, sills and volcaniclastic rocks, which together form part of the upper Paleozoic Stikine assemblage. The stratigraphy at Big Bull includes a mafic footwall that is overlain by an altered felsic package which is in turn overlain by second package of mafic rocks. The altered felsic package is the host to the massive sulphide mineralization. This overall sequence of lithologies is similar to the stratigraphy at the Tulsequah Chief deposit, which is hosted by this same suite of felsic-mafic volcanic rocks. |
