Rockwell tables Pedra Branca results

Vancouver — The initial results from an ongoing drill program by Rockwell Ventures (RCW-V) have confirmed the structural complexities of the Pedra Branca platinum-palladium-bearing layered mafic intrusive in northeastern Brazil.

Local government geologists discovered the complex in the 1960s and, eyeing its chromite potential, drilled three holes at the Esbarro zone in 1967. This led to a combined estimate of 43,000 tons grading between 10% and 28% chromite. Five additional holes were drilled in 1969, but the zone was not expanded.

The project sat until 1985, when South African-based Gencor and mining powerhouse Rio Tinto (RTP-N) identified platinum-palladium mineralization associated with the chromite bands. Targeting separate areas on the ultramafic belt, they completed airborne magnetic and radiometric surveys, mapping, soil-sampling and trenching. This revealed 10-15 scattered showings of chromitite and copper-nickel soil geochemical anomalies.

Rio focused on the most northerly chromite occurrences — Esbarro 1 and 2. Located only 15 km from the village of Capitao Mor, the showings lie within 400 metres of each other. The major punched 42 holes over an 800-metre strike length and 13 of the holes cut the favourable chromite horizon. Using a cutoff grade of 1 gram combined platinum-palladium, the 13 holes returned an average of 2.5 grams combined platinum-palladium over 6.1 metres, including a higher-grade zone averaging 6 grams combined platinum-palladium over 2.1 metres.

Gencor targeted the central and southern portions of the ultramafic belt. The company completed a trenching program and drilled eight holes on the Traipia 1 and Trapia 2 showings. The holes returned an average width of 16 metres with an average grade of nearly 7 grams combined platinum-palladium-gold.

With the price of palladium trading at between US$100 and US$120 per oz. in 1987, both programs were terminated without an economical conclusion.

As the price of palladium started to soar in the late 1990s, Vancouver-based Altoro Gold, which recently merged with Denver-based Solitario Resources (SLR-T), set its sights on the project.

In late 1999, Altoro tested Pedra Branca with an 18-hole, 1,200-metre drill program. Seven of the holes targeted the Trapia West zone, one tested Trapia 1, eight tested Esbarro, and two tested Ipueiras. The results yielded some impressive intercepts, but many holes failed to cut the favourable ultramafic horizon.

Short on cash and with inconclusive drill results, Altoro inked a deal allowing Hunter Dickinson to earn a 60% stake in the project. Hunter Dickinson, with a stable of junior exploration companies, vended it into Rockwell Ventures.

Covering an area measuring 40-by-20 km, the ultramafic complex exhibits many similarities to the largest repository of platinum group metal, the Bushveld complex in South Africa. Initial mapping and sampling by Rockwell has led the junior to compare the chromite-bearing zones to the high-grade UG2 horizon at Bushveld.

However, unlike its relatively pristine South African counterpart, Pedra Branca has been subject to significant metamorphism and structural impact. This makes exploration much more challenging.

Late last year, Rockwell launched a property-wide mapping and sampling program aimed at outlining drill targets.

The first 14 holes of this year’s drill program tested the continuity of mineralization at Esbarro.

Hole1 tested the downdip extension of mineralization hit in Altoro drill hole 4 (22.3 metres grading 1.81 grams palladium and 1.08 grams platinum from 11 metres down-hole). It returned 10.8 metres averaging 1.7 grams palladium and 0.36 gram platinum from 33.2 metres down-hole.

Fifty metres to the east, hole 2 returned 3.8 metres grading 2.24 grams palladium and 0.58 gram platinum from 59.6 metres down-hole.

Hole 3 was collared 100 metres to the north and east of hole 2. It returned 0.34 gram palladium and 0.73 gram platinum over 1 metre from 43 metres down-hole.

A further 200 metres to the east, hole 4 tested the mineralization south of Altoro hole 8 (6.7 metres grading 2.24 grams palladium and 1.42 grams platinum from 20.6 metres down-hole). It hit two zones. The first returned 2.05 grams palladium and 0.5 gram platinum over 4.9 metres from 22.4 metres down-hole. The second returned 13 metres grading 1.49 grams palladium and 0.58 gram platinum from 43 metres down-hole.

A hundred metres north-northeast, hole 5 cut five mineralized lenses, including 4.14 grams palladium and 4.75 grams platinum over 2.9 metres from surface. The broadest zone cut 1.73 grams palladium and 0.58 gram platinum over 20.1 metres from 14.7 metres down-hole.

Hole 6 was drilled 100 metres west of hole 4 and hit 0.46 gram palladium and 0.49 gram platinum over 1.3 metres from 77 metres down-hole.

Holes 7, 8, 9, 10, 12 and 13 were collared along the southwest margin of the Esbarro zone. They covered 450 metres of strike length, but failed to hit the favourable ultramafic horizon.

Holes 11 and 14 were collared 50 metres northeast and northwest of Altoro hole 8, respectively. They reportedly hit wide intervals of the favourable horizon. Assay results are pending.

Based on the latest round of drilling, the Esbarro zones cover a continuous mass of ultramafic host rocks measuring 1 km long and 300-400 metres wide. According to Rockwell, the mineralization may represent a large-scale boudin produced by flattening and structural extension occurring during the main metamorphic event. Alternatively, it may be a result of irregular intrusive contacts produced by the intrusion of the younger granite body.

The company expects that the mineralized pods and troughs will be repeated throughout the 1,000-sq.-km Pedra Branca property.