Ongoing drilling by Ivanhoe Mines (IVN-T) has expanded the company’s discovery of gold, copper and molybdenum porphyry mineralization at the Turquoise Hill project in southern Mongolia.
Final gold and copper assay results from two recently completed diamond drill holes, nos. 162 and 166, have increased the surface dimensions of the Discovery zone, a high-grade gold-and-copper-rich porphyry body at the north eastern edge of Southwest Oyu to about 315 by 350 metres. The mineralization extends to about 500 metres below surface.
Hole 162 was highlighted by a 130-metre interval (starting at 110 metres below surface) running 2.25 grams gold per tonne plus 0.85% copper. The final 22 metres of the hole, which bottomed at 314 metres, averaged 0.97 gram gold and 0.64% copper.
Hole 166 averaged 1.38 grams gold and 0.74% copper over 478 metres beginning at 60 metres below surface, including 366 metres (from 172 m) of 1.69 grams gold and 0.86 % copper, which in turn included 108 metres (from 172 m) of 2.59 grams gold and 0.99% copper.
Assay results are pending for holes 169 and 171, which tested the Discovery zone to downhole depths of 751 and 614 metres, respectively. Both holes cut strong copper porphyry mineralization similar to that encountered in previously reported holes, including hole 150 (508 metres of 1.17 grams gold, plus 0.81% copper and 0.01% molybdenum).
Hole 171, a 120-metre step-back from hole 162 cut strong zones of copper porphyry mineralization between downhole depths of 87 and 572 metres.
Hole 169, a re-drill collared 5 metres away from previously drilled hole 163 (which failed to reach the Discovery zone’s mineralized) encountered strong copper porphyry mineralization between downhole depths of 480 and 600 metres. Hole 163 returned 164 metres (from 262 m) of 1.05 grams gold and 0.67% copper.
Drilling of three additional 120-metre, step-back holes aimed at further delineating the Discovery zone has begun.
Preliminary flotation test work conducted by Lakefield Research on About 400 kg of mineralized drill core from Turquoise Hill has indicated gold recovery rates of 90% and 95% for copper in the rougher concentrate. Bottle roll tests on the chalcocite blanket material showed good leachability.
The Discovery Zone is coincident with one of several magnetic anomalies identified in Southwest Oyu. Drill testing of other anomalies is underway. The company plans to test other targets as it completes infill drilling on the Discovery zone.
The Turquoise Hill project contains four known porphyry zones covering an area measuring 3 by 2 km. The other zones are South, Central and North Oyu.
Based on a preliminary extrapolation of all drilling to date, Ivanhoe believes that the Turquoise Hill porphyry system has the potential to host more than 1 billion tonnes of copper, gold and molybdenum mineralization. The company says that Southwest Oyu alone may contain more than 500 million tonnes of copper and gold mineralization.
Ivanhoe has the conditional right to acquire the Turquoise Hill project by spending US$6 million on exploration and paying BHP-Billiton (BHP-N) US$5 million. The project contains four other known porphyry zones covering an area measuring 3 by 2 km.
Encouraged by recent results, Ivanhoe recently acquired four more copper-gold properties in the mineral belt that hosts the Turquoise Hill porphyry system. The latest acquisitions — Oyut Ulaan, Chandman Uul, Oyut Ovoo and Saran Uul have returned encouraging values in rock samples. Systematic mapping, geochemical sampling and geophysical surveying are under way.
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