Ivanhoe reports hot hole at Turquoise Hill (September 30, 2002)

The Turquoise Hill copper-gold project of Ivanhoe Mines (IVN-T) in Mongolia’s South Gobi region just got bigger.

A hole drilled at the virgin Far North zone returned 638 metres averaging 1.61% copper and 0.07 gram gold per tonne, beginning at 222 metres down-hole (or 190 metres below surface).

A higher-grade section of hole 270, which was angled at minus 60 to the north, ran 3.58% copper and 0.23 gram gold across 114 metres at a down-hole depth of 576-690 metres. The rig bottomed out in mineralization at 860 metres down-hole, with the final 8.9 metres grading 0.71% copper.

In early August, Ivanhoe intersected wide intercepts of chalcopyrite mineralization while drill-testing an induced-polarization (IP) target on the Far North Oyu zone, some 2.5 km north of the Southwest discovery zone.

At the Southwest zone, Ivanhoe has outlined an inferred mineral resource of 821 million tonnes grading 0.38% copper and 0.52 gram gold per tonne, based on a cutoff grade of 0.3% copper-equivalent. Southwest contains a higher-grade core of 120 million tonnes grading 0.7% copper and 1.55 grams gold, equivalent to 817,200 tonnes copper and 6 million oz. gold.

The first two holes on the Far North zone were drilled 200 metres apart in the eastern half of a broad IP anomaly measuring 1,000 by 500 metres. Discovery hole 244 cut 284 metres grading 0.66% copper and 0.04 gram gold between 296 and 580 metres down-hole. The hole ended prematurely in copper mineralization when the rig reached its maximum depth capability.

The second hole, 246, was collared a further 200 metres to the west, cutting 136 metres of 0.58% copper and 0.05 gram gold at a down-hole depth of 170-306 metres. Hole 246 was drilled to a total depth of 500 metres.

Ivanhoe continued to step out to the west and completed four other holes, picking up sniffs of high-grade mineralization before making a significant intersection with hole 270, about 200 metres east of the discovery hole.

Ivanhoe has since tested the updip and downdip extensions of the mineralization in holes 270, 244 and 246, with results pending. “There is a distinct possibility that Far North could prove to be the most important copper system in the Oyu Tolgoi district,” says Douglas Kirwin, Ivanhoe’s executive vice-president exploration.

The Far North zone occurs on the northern portion of a large circular IP feature that appears to ring the Oyu Tolgoi hydrothermal system. The Central Oyu system sits on the southern margin of the IP anomaly. Recent drilling on the Central zone has encountered intrusive and volcanic-hosted hypogene, gold-rich chalcopyrite mineralization, similar to that found in the Southwest discovery zone, 1 km to the south. The primary zone appears to surround a core of secondary copper-rich covellite and chalcocite mineralization that lies directly beneath a near-surface supergene-enriched blanket.

At last report, 10 widely spaced holes into the Central zone had encountered primary chalcopyrite mineralization over a distance of 1,000 metres east-west and up to 800 metres north-south.

Unlike the Central or Southwest zones, mineralization in the Far North zone is primarily hosted by tuffs and basaltic volcanics. The mineralized quartz monzodiorite porphyry intrusion has not yet been encountered in the Far North zone. Three rigs continue to turn on the Far North discovery area.