Platexco hits PGM at Winnaarshoek

A drill program by Platexco (PGMI-C) at its Winnaarshoek property in South Africa’s Bushveld complex has returned numerous intercepts bearing platinum group metals (PGM).

The 9-hole program was undertaken at the UG-2 reef, a PGM-bearing chromitite reef parallel with, and 400 metres vertically below, the recently-drilled Merensky reef (T.N.M., Dec. 1/97). The UG-2 reef outcrops about 2 km east of the Merensky, and both reefs dip 13 west.

Holes U1, U2 and U3 were drilled in the northeastern corner of the property to intersect the UG-2 reef at 60 metres below surface, its shallowest depth.

Holes U4 and U5 are part of a line of seven holes, collared at 200-metre intervals, designed to intersect the UG-2 at a depth of about 200 metres.

Holes U7 to U10 have been completed, and assays are pending. Hole U6, which intersected a fault, is being redrilled.

Assay results (the PGMs are platinum, palladium, rhodium and gold concentrations) include: 12.87 grams PGM per tonne over 0.62 in hole U1; 9.23 grams over 0.73 metre in hole U2; 10.65 grams over 0.72 metre in hole U3; 5.06 grams over 1.08 metres in hole U4; and 9.22 grams over 0.66 metre in hole U5.

Previously reported holes 1, 5, 9 and 15, which reached preliminary depths of 50 metres in the Merensky reef, have been deepened to intersect the UG-2 reef at a depth of about 450 metres.

Assays from the UG-2 portion include: 6.5 grams over 0.87 metre in hole 1; 7.53 grams over 0.62 metre in hole 5; 53.4 grams over 0.16 metre in hole 9 (an intersection that may represent a depression, or “pothole” in the UG-2 reef); and 7.08 grams over 0.69 metre in hole 15.

Excluding hole 9, the average for the eight holes was 8.2 grams over 0.75 metre. Assay results for the UG-2 reef have been presented differently than those for the Merensky reef because, according to the company, UG-2 is a chromitite layer bounded by a hangingwall pyroxenite and a visually and physically distinct footwall pegmatoid.

Although the grade and thickness of the chromitite layer form the basis of UG-2’s main PGM resource, the company says the overall grade at Winnaarshoek will likely be diluted by a 1-cm-thick chromitite “leader” layer. That stratum is separated from the main chromitite by a 6-cm-think pyroxenite parting that forms a natural break in the hangingwall.

If the leader and parting are included, the average grade of the aforementioned chromitite layer in the same eight holes slips to 7.62 grams over 0.82 metre.

The average grade of the leader and pyroxenite parting in the eight holes is 1.41 grams over 7 cm, which dilutes the overall grade at UG-2 by 7%. If the combined thickness of the UG-2 chromitite, parting and leader is less than 0.8 metre, dilution may also result from the inclusion of the footwall pegmatoid, which has an average grade of 1.54 grams over 0.19 metre.

According to Platexco, the footwall pegmatoid and hangingwall pyroxenite can be readily separated in the plant, such that the mill-feed grade will not be diluted significantly from the grade of the chromitite layer.

Assays for individual PGMs, as well as for ruthenium, iridium, nickel and copper, are being performed.

Platexco also reports that a second line of 10 diamond drill holes has been completed. Those holes were designed to intersect the Merensky reef at a depth of 100 metres, and assay results are expected in early 1998.

A third line of holes drilled to intersect the Merensky reef at 200 metres is under way. The company also plans to drill a deep hole into the reef, from the western portion of the property.