The Ferensola Gold Project – Maiden Drilling Campaign
The Ferensola gold project is located in northeast Sierra Leone, approximately 200 km east-northeast of the capital Freetown. The licence, registered under Sula’s 100% owned subsidiary Blue Horizon, totals 153km2 and is host to the Ferensola iron project and the Ferensola gold project.
For a summary of the history of the Ferensola gold project, click here.
Ferensola Gold JORC Compliant Exploration Target
In mid-2015, after a detailed review of the data and a resampling programme of historic core, Sula released a JORC compliant Exploration Target for the Ferensola gold project, being authored by independent consultants SRK Consulting (UK) Ltd (SRK). The Exploration Target covers a 2 km portion of a regional fold belt with evidence for high grade mineralisation over a distance in excess of 10 km. In defining the Exploration Target, SRK used the magnetic anomaly data to define the regional fold structure and to establish a trace length for the mineralisation which approximated to 2 km and with a dip extent of 300 m. Mineralisation was assumed to comprise discontinuous sheets of massive sulphide of between 2 and 5 m in width, with nominal strike extents of between 100 m and 300 m. The most significant accumulations of mineralisation were assumed to be contained in fold-hosted shoots akin to ‘saddle reefs’. The SRK defined Exploration Target for the Ferensola Project has a tonnage range of between 5 and 7 million tonnes (“Mt”) at a grade range of between 4 and 8 grammes per tonne (“g/t”). This equates to between 0.8 and 1.5 million ounces (“Moz”) Au.
Table 1: Ferensola Gold JORC Compliant Exploration Target
|Tonnage Range (Mt)||Au Grade Range (g/t)||Contained Gold Range (Moz)|
|5 - 7||4 - 8||0.8 – 1.5|
Maiden Drilling Campaign
Following on from the generation of the Exploration Target, in November 2015 Sula completed its maiden drilling campaign within a portion of the Exploration Target defined by SRK. Sula completed 10 diamond drillholes for a campaign total of 1,556.2 m. All drilling was supervised by Senior Structural Geologist, Dr Paul Stenhouse of SRK and Mr Howard Baker, Sula’s Non Executive Technical Director.
The collar coordinates and collar dip and azimuth are set out in Table 2. Drillhole locations are also shown on the map in Figure 1, where they are overlain on the regional structural interpretation and magnetic data which has previously been used in the definition of the Exploration Target.
Table 2: Drillhole Collar Information
|Batch||Hole ID||Easting||Northing||Elevation||Collar Dip||Collar Azimuth||Depth (m)|
Figure 1: Drillhole location map
Figure 2 shows the assay intervals returned from the drilling campaign with a 0.5 g/t Au cut-off applied to filter the data.
Figure 2: Significant intersections
Table 3 shows the assay intervals and total length-weighted grade of the significant intersections when applying a 0.5 g/t Au cut-off to the upper and lower contacts (internal dilution below the cut-off grade of up to 1.9 m has been allowed to achieve continuity downhole).
The length-weighted average grade equates to 4.48 g/t Au and the calculation includes the resampled historic drillholes, SDD004, SDD016 and SDD033, the results of which were utilised in the generation of the Exploration Target. These historic intersections were targeted in drillholes FDD001 to FDD004, with the intersected mineralisation in both sets of holes lying within the same mineralised shears and being in close proximity to one another.
The true thickness has been calculated using the drilling angle and the dip of the mineralised structures as defined by structural logging. The true thickness is on average approximately 65% of the apparent thickness across all drillholes.
Table 3: Significant intersections from holes FDD001 to FDD010 and historic drillholes SDD004, SDD016 and SDD033 (0.5 g/t Au cut-off grade applied)
|Hole ID||From (m)||To (m)||Apparent Thickness (m)||True Thickness (m)||Au (g/t)|
|FDD006||No intersections above 0.5 g/t Au recorded|
|FDD007||No intersections above 0.5 g/t Au recorded|
|FDD010||No intersections above 0.5 g/t Au recorded|
|Total Length-Weighted Grade (g/t Au)||4.48|
The location of the resampled historic drillholes in relation to the recent drilling campaign is shown in Figure 3.
Figure 3: Resampled historic intersections
Interpretation of Drilling Results
Mineralisation is hosted by a complex, north-northeast striking and steeply west-northwest dipping shear zone within mafic volcanics. The shear zone consists of multiple, discrete, biotite-altered shears and a peripheral zone of veining, with several phases of overprinting deformation and sulphide deposition. Gold is primarily associated with late-stage, massive pyrite breccias that form within the highly sheared intervals and to a lesser extent with distributed veining in the adjacent wall rock.
Figure 4: Pyrite-matrix breccia from FDD006
A preliminary interpretation of the logging and assay data, utilising the structural measurements recorded by SRK shows that the overall shear zone, covering a strike length of approximately 350 m, comprises multiple sub-parallel strands that dip at an average of 75° to the west-northwest and that display individual continuity over distances in the order of 100 to 200 m. Mineralisation is currently open at depth. Figure 5 shows the preliminary interpretation of the mineralised structures from the current data which highlights that mineralisation is not limited to a single, steeply dipping, sub-planar zone. The interpretation is also shown in the associated video shown below.
Figure 5: Preliminary interpretation of mineralised structures
Watch the JORC Exploration Target – Preliminary Interpretation Video:
Drilled Area Approximately 25% of the Exploration Target Area
The drilling undertaken in November 2015 focussed on known areas of historic mineralisation with step out holes targeting mineralisation along strike from the initial FDD01 to FDD004 drillholes. The full extent of the Exploration Target area defined by SRK has not been tested by the drilling programme with approximately 25% of the 2 km strike length tested to date. Figure 6 shows the area defined by SRK as the Exploration Target and highlights the mineralisation data currently available that has not been tested by drilling. This includes significant mineralisation within the Sula trenches, the presence of previously reported high grade massive sulphides and artisanal goldstones and artisanal mining activities, further highlighting the potential for additional discoveries.
Goldstone is a colloquial term for material believed to represent weathered sulphide mineralisation and is one of the target material types of local artisanal miners in the area.
Figure 6: Exploration Target area (dashed lines) showing mineralisation targets outside of the drilled area
November 2015 Grab Sample Results
In addition to the November drilling activities completed, sulphide and goldstone samples were collected during a regional sampling programme. Seven samples were collected from an area approximately 2 km to the south of the Exploration Target, including six artisanal goldstones and one quartz-pyrite sample. An additional sample was collected from the far west of the licence area with a returned grade of 0.02 g/t Au. All samples reported are interpreted by Sula to be from or close to their primary source and were collected from areas that coincide with the regional fold interpretation that covers an approximate 10 km strike length. High grade results were returned from six of the goldstone samples, with an average grade of 8.3 g/t Au. The single quartz-pyrite sample returned the highest grade recorded on the licence to date of 69.2 g/t Au.
Table 3 shows the results of the samples collected and Figure 7 shows the locations of the samples collected, where it is clear that the locations are aligned with the regional fold belt identified within the licence. During the field programme leading up to the generation of the Exploration Target, eight near source goldstone samples were submitted for assay with an average returned grade of 5g/t, with a minimum returned grade of 0.2g/t and a maximum of 12.4g/t. In addition, two sulphide stones were submitted for assay returning grades of 7.5g/t and 4.2g/t.
Table 4: Goldstone and Quartz-Pyrite sample assay results from samples taken during the November drilling campaign
|Sample No.||X||Y||Z||Weight (kg)||Sample Type||Au (g/t)|
|6035||220807||1015518||548||3.1||Quartz - Pyrite||69.2|
Figure 7: Goldstone / Quartz-Pyrite sample locations
Figure 8 shows examples of the goldstones from the area around where several goldstone samples (6028, 6029 and 6030) and the quartz-pyrite sample (6035) were collected.
Figure 8: (a) Typical goldstone (b) Goldstone and artisanal grinding hole (c) 69.2 g/t Au Quartz-Pyrite sample
Samples 6031 and 6032 are located to the south of drillhole FDD007 where goldstones showing a massive pyrite core and quartz veining are prominent within a river bank exposure. A selection of photographs from this area are shown in Figure 9.
Figure 9: (a,c,d) Goldstone sample showing a massive pyrite Core (b) Quartz-Pyrite sample (e) Goldstone boulder being actively exploited
As previously documented, it was believed by Sula and SRK that historic drilling, being to the west, was sub optimal in orientation with the mineralised structures also exhibiting a westerly dipping trend. The November drilling has now confirmed this and the structural logging undertaken shows that multiple high grade shear zones are present within the area tested by drilling with an easterly orientation to the drilling being the optimum direction in this part of the licence.