Anglo, Philex hit second porphyry

Vancouver — Perseverance and a good-sized exploration budget have enabled partners Anglo American (AAUK-Q) and Philex Gold (PGI-V) to find a second mineralized copper-gold porphyry body near the high-grade Boyongan deposit on the North property in the Philippines.

So far, seven holes have intersected the porphyry body, and the best results are from holes drilled 650 metres northwest of the Boyongan deposit. Hole 23 returned an impressive 0.9% copper and 1.1 grams gold per tonne over 260 metres at a down-hole depth of 363 metres. Included in this section was a higher-grade portion grading 1.44% copper and 1.85 grams gold over 132 metres. Mineralization is hosted in potassic-altered medium-grained diorite with a strong argillic overprint. The base of oxidation was hit at 426 metres, the main copper minerals being cuprite, azurite and malachite. Sulphide mineralization comprises disseminated pyrite, chalcocite, minor chalcopyrite and trace bornite.

Holes 73 and 77 were collared 250 metres northwest of the original find, cutting 286 metres grading 0.42% copper and 0.67 gram gold from 514 metres and 326 metres grading 0.26% copper and 0.31 gram gold from 373 metres, respectively.

Hole 75 was drilled 200 metres to the northeast and returned 508 metres grading 0.33% copper and 0.44 gram gold at 374 metres down-hole, while hole 15 was sunk 200 metres to the southwest and yielded 591 metres of 0.32% copper and 0.3 gram gold at 410 metres down-hole. Included is a 131-metre section grading 0.52% copper and 0.48 gram gold

“The prospect appears to be deep-seated and may continue farther west within the joint venture’s exploration permit area, and north beyond the joint venture’s tenements,” says Philex CEO Gerard Brimo.

Two rigs are operating, with hole 24 being drilled from the same site as hole 23 and angled 60 in an easterly direction. The hole hit the desired porphyry at 376 metres and is drilling at 420 metres. Hole 78 is being drilled 100 metres west of hole 73. This hole intersected intensely stockworked, potassic-altered diorite porphyry hosting veinlet and disseminated chalcopyrite, pyrite and rare bornite at 570 metres down to its last reported depth of 676 metres.

Anglo American first sparked interest in the property in September 2000, when hole 6 returned a 365-metre intercept grading 0.7% copper and 1.9 grams per tonne gold. Subsequent drilling throughout 2001 and 2002 continued to yield impressive numbers, including 393 metres grading 1.58% copper and 2.39 grams gold in hole 15 and 896 metres grading 0.49% copper and 1.57 grams gold in hole 18.

The Boyongan deposit is hosted by a composite diorite stock that was locally affected by a later argillic event, resulting in some high grades. The prospect hosts unusually deep supergene oxidation (more than 400 metres locally), which was preserved as a result of being capped by Quaternary sediments and lavas. Malachite, azurite, cuprite and native copper define the oxide zone. Chalcopyrite and bornite dominate the primary copper sulphides.

At last report, Anglo had outlined a 600-by-300-metre area of mineralization grading 1% copper-equivalent within a larger, 1,000-by-500-metre area averaging 0.5% copper-equivalent.

Says Brimo: “According to Anglo, while the Boyongan deposit contains high grades in part, the tonnage anticipated from the oxide zone is unlikely to be sufficient to support a large-scale, long-life operation, while the deep-seated sulphide mineralization currently appears to have an erratic grade distribution.”

Failing to meet the mining giants’ tonnage standards, Anglo decided to look for additional mineralized porphyries on the property. The efforts appear to have paid off: the new discovery is prompting the partners to stake additional ground.

“Discussions with the claim-holder to the north have reached an impasse and negotiations to acquire other tenements elsewhere that are prospective for copper-gold mineralization are ongoing,” says Brimo.

Late in 2001, Anglo American bought an additional 10% equity stake in the project and surrounding ground from Philex for US$20 million. Additional payments of up to US$5 million will be required should the metal content of the deposit, or of any other discovery in the surrounding claims, contain more than 3.6 million tonnes copper-equivalent. Currently, Philex and Anglo American each hold a half-stake in the project. The major can then earn an additional 30% interest by completing a bankable feasibility study.