Bangaba, Burkina Faso
The Bangaba Project in Eastern Burkina Faso (Figure 1) covers areas of extensive artisanal mining. PDI is earning a 95% interest in the 128 km2 Bangaba exploration permit by making a series of staged payments in cash and shares.
PDI estimates that artisanal miners have produced several tonnes of gold at Bangaba over the past 30 years. Artisanal workings are located on two structures on the north-west and south-east contacts of a granodiorite-diorite body (Figure 2). A large artisanal mining site is located at Solna.
RC and diamond drilling programs at the two major sites of artisanal mining, Solna and Tambiri, have encountered a series of high grade intercepts in primary mineralisation including: 6m at 20g/t Au, 2m at 56g/t Au, 5m at 17g/t Au, 7m at 13g/t Au and 5.6m at 16g/t Au. No supergene enrichment is evident in the near surface so the high gold grades may persist to considerable depths.
Figure 1: Locality Plan - PDI permits in Eastern Burkina Faso
Figure 2: Bangaba Permit showing location of Tambiri, Tambiri South and Solna Prospects. Approximate location of bedrock geochemical anomalies is outlined in pink ellipses.
The Tambiri Prospect is an open pit target with underground potential.The gold mineralisation consists of a quartz vein system hosted in mafic volcanic rocks, which is typically between 5 and 20m thick. The mineralisation dips steeply to the south-east and all intercepts correlate well together. Higher gold grades are associated with a flat plunging shoot (Figure 3). Anomalous gold results have been found over more than 3km of strike both to the north-east and south-west of Tambiri indicating that there is significantly more potential to discover more of the same kind of mineralisation including high grade ore shoots alongt he same structure.
Indications of along strike potential have already been found at Tambiri South 1.5km SW of Tambiri (Figure 2). A small RC drillhole program in December 2012 obtained up to 4m at 6.1g/t Au from 83m including 1m at 14g/t Au.
Figure 3:Longitudinal Projection - Tambiri drilling results
Like Tambiri, the Solna Prospect is an open pit target with underground potential.The gold mineralisation consists of shear hosted mineralisation within a granodiorite body. Gold is found in a series of shoots within sub-parallel structures, which have been named the A, B and C Lodes.While ore widths are relatively narrow (generally around 2-3m), average gold grades are quite high, with values of up to 111g/tAu in individual 1m intervals.
While drilling at this prospect has generated good gold intersections, the geological controls on mineralisation are not well understood. Potential still exists to discover a significant amount of high grade gold mineralisation, however PDI’s immediate focus is on targets with greater potential to discover high grades and widths with good continuity such as at Bongou.
Figure 4: Solna drill results – plan view
A program of preliminary metallurgical test work was carried out with the aim of obtaining an initial indication of gold recoveries by standard CIL treatment of gold mineralisation from the Solna and Tambiri Prospects. Two samples were submitted for metallurgical test work, one from each prospect, each weighing 20kg. All samples were obtained from RC drill holes.The test work was carried out at SGS’s Perth laboratories under the supervision of Coffey Mining. A mineralogical study was also carried out by Roger Townend and Associates.
The composite sample consisted of primary mineralisation containing minor sulphides. A 500g screen fire assay of the composite sample at SGS in Perth gave a head grade of 7.65g/t Au and a multi-element ICP analysis indicated low levels of potentially deleterious elements. The sample was ground to 75 microns and subjected to a standard cyanide leach test over 72 hours. Gold recovery was 96% at the end of the test with 91% recovered in the first four hours. Cyanide and lime consumption were 1.9kg/t and 0.3kg/t respectively. Cyanide consumption was not optimised and is expected to decrease considerably in future test work.
Figure 5: Polished section of RC chips from the Solna Prospect at high magnification showing a composite grain of pyrite (grey) and gold (buff-yellow).
As at Solna, the sample consisted of primary mineralisation. A 500g screen fire assay of the composite sample at SGS in Perth gave a head grade of 3.55g/t Au and a multi-element ICP analysis indicated low levels of potentially deleterious elements. The sample was ground to 75 microns and subjected to a standard cyanide leach test over 72 hours. Gold recovery was 93% at the end of the test with 85% recovered in the first four hours. Cyanide and lime consumption were 2.0kg/t and 0.3kg/t respectively. Again, cyanide consumption was not optimised and is expected to decrease in future test work.