Ore Deposit Information

Nalesbitan Hill, the site of GFPC's ill-fated open-pit mining operation, forms the western sector of  1,300m long, up to 150m wide, zone of argillic-silica altered hydrothermal breccias. The breccias are confined within the Nalesbitan Shear Zone, which is defined by an anastomosing set of WNWESE- striking faults. The mapped faults are zones of intense argillic alteration (pug). It is notable that major gold mineralisation is confined to the significantly more rugged, higher western sector of the breccia zone. A sharp topographic break between the western and eastern sectors may be the location of a NE-trending fault zone parallel to significant basement faulting ( Figure 3 ).

RGC classified the gold mineralisation as an acid-sulphate epithermal system, based on the high oxidized sulphide content of the silica breccia lodes (which can be clearly recognised in the field), the alteration mineralogy, and association of minor arsenical copper mineralisation (enargite) with arsenic and molybdenum soil anomalies. This data is indicative of a high-level, phreatic breccia system of meteoric-magmatic origin.

There is a high gold:silver ratio of 1:2 at Nalesbitan Hill. Significantly, the gold-copper mineralisation at Millsite-Singko is silver-rich, with a gold:silver ratio of at least 1:5.

It was also recognized by RGC that this high level, i.e. near surface, epithermal type of gold mineralisation is characteristic of copper-porphyry environments. However, district geological mapping and petrographic data of the very widespread argillitic-siliceous-pyritic alteration failed to provide evidence of potassic alteration typical of an associated porphyry system.

Recent reviews of exploration data, focussing particularly on district geochemical associations, and supported by recent data in drill hole ND1, suggest that the Nalesbitan Hill gold mineralisation could be significantly younger in age, probably post-dating the collapse of the Susungdalaga volcanic edifice.

In 1995, Triarx's consultants estimated that the gold resource remaining after limited mining by GFPC to be 1.185 million tonnes at a grade of 2.53 g/t gold, with a 1.25 g/t cut-off (96,400 oz gold). A specialist review is currently being undertaken to define the extra drilling that may be required to update categorisation to the present-day JORC resources code.

The southeastern extension of the hill is a broad ridge, and as noted above, at a significantly lower elevation, bounded to the north by the Millsite-Singko lode system and the Central Fault to the south. Recent drilling (ND1) suggests that a NE-trending fault may separate the eastern ridge from the more rugged and more strongly gold-mineralised western, Nalesbitan Hill, sector.

RGC undertook limited drilling along the eastern zone, with 5 drill holes along a strike extent of 400m ( Figure 9 ). Two gold lodes can be inferred from this drilling, with the best diamond cored intersection of 18m at 1.9 g/t gold and 0.3% copper. This copper-mineralised intersection and high copper values locally associated with gold in samples from gold workings in the breccias further west, provide evidence that Millsite-Singko-type mineralisation has been brecciated and reworked along the Nalesbitan Shear Zone.

It is notable that a group of old gold workings at the eastern end, closely associated with a splay of the Central Fault and an 80m long lens of siliceous-sulphide (copper) mineralisation, has never been drill-tested.

Photos, Diagrams & Map of Mine Site

Figure 3 - Geology of the Northern Bicol Peninsula, Philippines

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Figure 9 - Bagong Dose Proposed Drilling Program

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