Since the announcement of its discovery in February,
The zone extends roughly 300 metres vertically between a depth of 300 and 600 metres from surface. It is closed off to the south, whereas further drilling to the north and downdip has intersected thinning and lower-grade sulphide mineralization.
The massive sulphide horizon dips 80 to the west, with core intersections averaging 4-5 metres true width. The sulphide intercepts average 14.6% zinc, 3.6% copper and 1% lead, plus 142 grams silver and 0.15 gram gold per tonne.
Drilling was suspended toward the end of July so that Inmet could thoroughly evaluate all of the data generated to date and complete a mineral resource estimate.
According to Frank Balint, Inmet’s vice-president corporate development, “we’ve really just been following our noses and stepping out on massive sulphides to date and not necessarily appreciating all of the data we’ve been collecting as much as we would like to. We expect to be back this fall with the objective of adding more tonnes by drilling extensions to the massive sulphides as we know them and drilling more holes along strike on the Jaguar conductor itself.”
So far, drilling has tested a little more than 500 metres of the 1,800-metre-long electromagnetic (EM) conductor.
The Jaguar discovery was made on the Teutonic Bore joint venture project, 260 km north of Kalgoorlie and 60 km north of Leonora. Inmet can earn a 70% interest in the project from Australian-listed
The Teutonic Bore project comprises the past-producing Teutonic Bore base metal mine plus 500 sq. km of surrounding exploration tenements, which extend some 40 km north to south. Teutonic Bore operated as an open-pit and underground mine between 1980 and 1985 under a joint venture between Seltrust Mining and Mt. Isa Mines. A total of 1.5 million tonnes grading 11.4% zinc, 3.61% copper and 167 grams silver were treated during this period.
In 1997, Pilbara acquired the Teutonic Bore mine lease from MIM, and subsequently accumulated an adjoining land package from MIM and Goldfields of Australia. Inmet optioned the property package from Pilbara in October 2000. The option agreement excludes all surface resources to a depth of 35 metres, and all mineral resources to a depth of 200 metres immediately below the old mine site, including tailings and stockpiles. Pilbara, on its own, has pursued the possibility of using bacterial oxidation to leach sulphide concentrates from the tailings resource.
Under the Inmet joint-venture agreement, Pilbara retains the right to explore for gold on the Teutonic Bore tenements. Should Pilbara outline a gold resource of more than 250,000 oz., Inmet has the right to earn a 70% interest by conducting further exploration to increase it to 1 million oz. within 12 months.
The Teutonic Bore concessions lie at the southern end of the Yandal greenstone belt, roughly halfway between
Pilbara has budgeted A$1 million for gold exploration during the 2002-2003 financial year. In early June, the Aussie junior kicked off a regional program of gold exploration on the Teutonic Bore project following a review of the historical database. The area had seen limited exploration for gold by Pancontinental and Goldfields. Drilling by Pilbara in late 2001 yielded some anomalous intercepts of up to 0.51 gram gold. A 17,000-metre air-core drilling program got under way at the start of the summer.
Base metal potential
Inmet’s first task after optioning Teutonic Bore was to complete a ground electromagnetic (EM) survey using the Crone “deep EM” system over 21 km of favourable strike south of the original mine. Inmet was targeting possible repetitions of the massive sulphide mineralization in the same stratigraphic package of mafic and hydrothermally altered felsic volcanics as the Teutonic Bore mine. The ground survey outlined conductors at depths not tested by previous geophysical surveys.
Drilling, originally scheduled to begin in June 2001, was delayed while Pilbara awaited formal approval of the exploration licence under the Native Title Act. Title was finally granted in mid-December 2001. Inmet wasted little time and began a first pass of drilling in January 2002.
The first two holes were drilled 600 metres apart on a 1,800-metre-long EM conductor, some 4 km south of the old mine site. The first hole, collared at 72, intersected a 5.8-metre-thick sequence of interbedded mafic volcanic and graphitic shale containing anomalous copper and zinc values at a down-hole depth of 434 metres.
The second hole turned out to be the Jaguar discovery hole. Drilled at 70, hole 2 intersected 7.7 metres (5 metres estimated true width) of massive sulphides grading 16.1% zinc, 4.3% copper and 0.8% lead, plus 173 grams silver and 0.24 gram gold, starting at 485 metres down-hole or 450 metres vertically.
Says Pilbara’s managing director, John Davis: “The Jaguar discovery was the result of a classic exploration exercise by Inmet based on geological theory and experience which suggests that massive sulphide deposits such as Teutonic Bore tend to occur in clusters, and drawing on the latest geophysical survey technology.”
Graphitic argillite
As Balint explains, crews were not faced with any difficulty in terms of conductive overburden or ground water using the transient EM geophysics. “We can see through, and that has really been the trick in finding this conductor at depth.” A graphitic argillite overlies the sulphide zone, which is contributing to the conductor. Borehole geophysics were done in an attempt to find the better sulphides.
“So far, every hole has an in-hole conductor,” says Balint. “In effect, it is causing us to be somewhat blind in terms of the borehole geophysics, because we are in conductor everywhere, and that poses a challenge. We pretty well have to step out on some sort of grid pattern within the conductor because the good massive sulphides could be anywhere.”
A preliminary examination of the sulphide mineralization indicates it is typical Archean run-of-the-mill sphalerite and chalcopyrite. “We don’t see any major challenges with respect to metallurgy at this time,” says Balint. However, more tonnes are needed before Inmet starts considering going underground. “We are going to go back and drill some more holes,” Balint said.
A second EM target, 10 km south of the Jaguar discovery, was unsuccessfully tested with a single hole during the first round of drilling. No mineralization was intersected, and the anomaly remains unexplained.
A summary of the high-grade massive sulphide intercepts reported from the Jaguar discovery is provided in the accompanying table.
HoleDepthWidthTrue WidthZnCuPbAgAu
(m)(m)(m)(%)(%)(%)(g/t)(g/t)
202485.45-493.157.75.016.14.30.81730.24
205465.15-467.902.751.917.02.70.41230.09
467.90-479.5011.67.8
dyke479.50-483.003.52.410.65.71.21200.12
207481.70-493.7012.08.014.95.00.61470.04
208595.02-595.370.350.314.35.00.41240.20
209536.85-541.754.93.39.33.20.71550.24
210397.75-406.859.16.916.61.90.7930.02
212521.85-527.405.553.413.92.91.01730.23
213561.25-565.454.22.612.27.50.82090.18
214422.20-422.400.20.216.52.80.91000.12
217670.20-672.402.21.5
9.04.30.8830.23
218643.23-650.587.355.38.33.81.01140.50
219540.90-547.006.14.012.54.10.91530.08
220742.40-742.550.150.13.80.80.4600.09
221458.60-468.359.757.523.30.62.31490.02
222614.70-615.400.70.55.00.70.4480.17
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