Vancouver — Drilling by
Six holes spaced 100-120 metres apart have cut long intercepts that average more than 2% copper and up to 0.3 gram gold per tonne. The results extend the high-grade mineralized core 600 metres to the northeast and 200-300 metres in width. The core extends down to a depth of 500 metres and hosts mineralization in excess of 1% copper; it remains open in all directions.
“The new results from the Far North zone contain the most impressive mineral intercepts we have encountered at Oyu Tolgoi [also known as the Turquoise Hill project],” says Exploration Vice-President Douglas Kirwin. “This expanding discovery opens the door to a number of development options that could see the Far North zone developed concurrently with the gold-rich Southwest zone, and we have yet to locate the mineralizing intrusive responsible for the high concentration of copper mineralization.”
Ivanhoe now believes it has identified enough mineralized material to allow its engineering group to begin economic and operational studies.
Drilling at the Far North zone has defined a mushroom-shaped body with mineralization spreading north and south. The mineralization is hosted in porous, volcaniclastic rock. Drilling has not yet encountered quartz monzodiorite intrusive rocks, which are known to host high-grade gold and copper mineralization at the nearby Southwest and Central zones.
Highlights from recent drilling at the Far North zone include:
r Hole 273 — 444 metres grading 1.37% copper and 0.04 gram gold per tonne starting at a vertical depth of 170 metres.
r Hole 282 — 304 metres of 1.28% copper and 0.05 gram gold starting at a vertical depth of 140 metres.
r Hole 286 — 532 metres of 1.63% copper and 0.05 gram gold starting at a vertical depth of 260 metres, including a 208 metre-section averaging 2.41% copper and 0.07 gram gold.
r Hole 289 — 368 metres of 1.91% copper and 0.09 gram gold beginning at a vertical depth of 298 metres, including a 170-metre section of 2.41% copper and 0.15 gram gold.
r Hole 270 — 638 metres of 1.61% copper and 0.07 gram gold starting at a vertical depth of 190 metres, including a 114-metre intercept of 3.58% copper and 0.23 gram gold.
Results from five other holes have yet to be reported, though Ivanhoe confirms that they’ve all cut thick intervals of similar chalcopyrite and bornite copper mineralization.
Drilling at the Central zone has intersected more wide intervals of gold and copper mineralization. Ivanhoe says the results significantly expand the known dimensions of the zone.
The development plan, is its current form, envisions open-pit development of the Southwest and Central zones in conjunction with large-scale open-pit or underground development of the Far North zone. Various production proposals, with rates ranging between 50,000 and 100,000 tonnes per day, are being evaluated.
At last report, the Southwest zone hosted a porphyry gold-copper deposit containing 13.8 million oz. gold and 3.1 million tonnes copper in an inferred mineral resource of 821 million tonnes grading 0.52 gram gold per tonne and 0.38% copper. This was based on a cutoff grade of 0.3% copper-equivalent. This estimate was prepared by AMEC E&C Services in accordance with Canadian regulatory requirements.
“The past six months have seen Turquoise Hill project transform itself from an exciting gold-copper play to a large-scale development project focused on mine planning, scoping and infrastructure studies,” says Kirwin. “In part, the continuity and scale of the deposits being drilled have made this rapid growth possible. When you are drilling 400- and 500-metre intervals of mineralization, the tonnes add up quickly.”
The recent drilling has demonstrated continuity within the covellite-chalcocite-dominated core of the system, while expanding the gold-rich copper mineralization to the northern side of Central Oyu. Highlights of the recent drilling at the Southwest zone are as follows:
r Hole 280 — 84 metres grading 1.24% copper and 1.31 grams gold per tonne, starting at 348 metres down-hole, plus 54 metres of 0.65% copper and 0.7 gram gold starting at 258 metres down-hole.
r Hole 284 — 136 metres of 1.19% copper and 0.49 gram gold starting at 258 metres down-hole.
r Hole 262 — 78 metres of 1.51% copper and 0.12 gram gold starting at 342 metres down-hole, plus 88 metres of 0.6% copper and 0.5 gram gold starting at 254 metres down-hole.
r Hole 258 — 440 metres of 0.96% copper and 0.21 gram gold starting 204 metres down-hole, including a 194-metre section of 1.25% copper and 0.26 gram gold.
In addition to expanding the gold-rich chalcopyrite mineralization, drilling continues to delineate and expand the copper-rich covellite-chalcocite mineralization in the Central zone. The overlying blanket of chalcocite mineralization could also provide a source of near-surface, high-grade copper mineralization for a concentrator complex at the initial stages of development.
The Central zone is delineated by an induced-polarization anomaly measuring 1,000 by 500 metres. Drilling to date has outlined an ovoid body of hypogene covellite and chalcocite mineralization that overprints a surrounding body of gold-rich chalcopyrite mineralization. Gold grades appear to be increasing with depth in the Central zone, a phenomenon also evident in the Southwest zone.
Primary mineralization remains open to the north, east and at depth. The mineralized zone is 600 metres long, 300-400 metres wide, and extends to a depth of 400-500 metres.
The Central zone is situated midway between the Southwest zone and the new high-grade copper discovery at the Far North zone.
Four rigs are drilling the Far North target in an effort to define it more accurately, while infill and resource-definition drilling at the Southwest, South and Central zones are endeavouring to expand the resource before year-end.
Ivanhoe has drilled more than 50,000 metres at Turquoise Hill this past year. In total, 12 rigs are on site, and two more are due to arrive.
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