Anglo hits elusive second porphyry

Vancouver – Perseverance and a good sized exploration budget has paid off with the discovery of a second mineralized copper-gold porphyry body near the high-grade Boyongan deposit on the North property in the Philippines.

So far, partners Anglo American (AAUK-Q) and Philex Gold (PGI-V) have hit the new discovery with seven holes.

The best results came from an area some 650 metres northwest of the Boyongan deposit, where hole 23 returned an impressive 0.9% copper and 1.1 grams gold per tonne over 260 metres from 363 metres downhole. Included in this section was a higher-grade portion running 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 with cuprite, azurite and malchite the main copper minerals. Sulphide mineralization comprises disseminated pyrite, chalcocite, minor chalcopyrite and traces of bornite.

Holes 73 and 77 were collared 250 metres northwest of the original find, cutting 286 metres grading 0.42% copper and 0.67 grams 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 north northeast, returning 508 metres grading 0.33% copper and 0.44 grams gold from 374 metres, while hole 15 was drilled 200 metres to the south southwest, yielding 591 metres grading 0.32% copper and 0.3 gram gold from 410 metres. Included is a 131 metre section running 0.52% copper and 0.48 gram gold

“The system, termed the Bayugo prospect, appears to be deep-seated and may continue further west within the joint venture’s exploration permit area, and north beyond the joint venture’s tenements,” says Philex’s Chief Executive Officer, Gerard Brimo.

Two rigs are currently turning, with hole 24 drilling from the same site as 23 and angled 60 degrees in the easterly direction. The hole hit the desired porphyry at 376 metres and is currently drilling at 420 metres. Hole 78 is being drilled 100metres west of hole 73. This hole hit, 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 back in Sept. 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.

Dubbed Boyongan, the deposit is hosted by a composite diorite stock that was locally affected by a later argillic event, which results 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

“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,” says Brimo.

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 with the new discovery prompting the partners to look at tying up addition ground.

“Discussions with the claim holder to the north have reached an impasse, negotiations to acquire other tenements elsewhere that are prospective for copper-gold mineralization are on-going,” adds Brimo. “We expect to announce the results of these negotiations, as well as the official resource estimates on the Boyongan deposit, in due course.”

Late in 2001, Anglo American purchased 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.