The Ferensola Gold Project – JORC Exploration Target
For a visual summary of the Ferensola gold project, please watch the video located below.
The independent technical presentation produced by SRK in support of the Exploration Target can be found under the following link: http://www.sulaironandgold.com/srk-presentation-2015-dalakuru-exploration-target/
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 recently announced Ferensola gold project.
Historically, the Ferensola gold project had been termed the Yanfaran Dalakuru Sende Zone (YDS) with previous operators completing extensive soil sampling, RAB drilling and 5,392m of diamond drilling at three prospects considered prospective for gold. In total, 34 diamond drillholes were completed by previous operators who intercepted significant quartz-sulphide breccias:
- 2.00m @ 8.76g/t Au and 8.72 m @ 10.46g/t Au from drillhole SDD004
- 1.55m @ 11.68g/t Au from drillhole SDD016; and
- 9.03m @ 6.63g/t Au from drillhole SDD033
The YDS was interpreted as being a 5km long northwest-southeast trending structure with mineralisation being controlled by faulting.
Since Sula acquired the licence, extensive exploration activities undertaken have included:
- Ground magnetic geophysical surveys
- Extensive soil sampling
- Field mapping and sampling of key locations; and
- Re-logging and re-sampling of the historic drill core
The work undertaken by Sula has resulted in the generation of 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 2km portion of a fold belt with evidence for high grade mineralisation over a distance in excess of 10km. In defining the Exploration Target, SRK used the magnetic anomaly data to define a fold structure and to establish a trace length for the mineralisation which approximated to 2km and with a dip extent of 300m. Mineralisation is assumed to comprise discontinuous sheets of massive sulphide of between 2 and 5m in width, with nominal strike extents of between 100m and 300m. The most significant accumulations of mineralisation are assumed to be contained in fold-hosted shoots akin to ‘saddle reefs’.
SRK defined an Exploration Target for the Ferensola Project with 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|
The Exploration Target was generated after all data existing for the project was reinterpreted along with field observations and extensive sampling was undertaken on key locations and on the existing drill core. The results of the reinterpretation resulted in the identification of a regional fold structure trending northeast-southwest that is on a similar geological trend to the Ferensola iron project and the neighbouring Tonkolili iron ore project as well as the regional trend of the Sula Kangari greenstone belt. Significantly, the work completed has advanced the geological understanding of the project and has advanced the project beyond the previous interpretation of the northwest-southeast trending YDS.
Figure 1: Location of the SRK defined Exploration Target (white oval) and regional fold trace interpreted through a review of the ground magnetic data and the collation of the historical and recent sampling programmes undertaken.
Within the hard duricrust oxide cover, mineralisation is observed as being hosted within iron oxide nodules of hematite / goethite. Sampling of the trenches from within the Exploration Target area returned assay results of 2.3g/t over a 20m zone, including 4m at 3.4g/t and 8m at 4g/t from Trench number 2. Trench number 5 returned assay results of 1g/t over 24m including 4m at 1.3g/t and 4m at 3.9g/t. Trench 11, located outside of the current Exploration Target area returned assay results of 4m at 3.3g/t and 4m at 2.5g/t.
Figure 2: Gold bearing hematite / goethite nodules within the duricrust
Figure 3: Trench 2 and Trench 5 location showing magnetic anomaly and historic diamond drilling
Goldstone / Sulphide Stone Mineralisation
Due to limited outcrop within the licence, river traverses have been undertaken in an attempt to locate mineralised samples associated with the fold belt. Of note was a location lying just south of trench number 5. From this location, samples of artisanal goldstones and partially weathered sulphide stones were located. The goldstones represent material targeted by the artisanal miners being similar to the iron oxide rich nodules observed in the trenches. The sulphide stones are believed to represent partially weathered derivatives of the underlying primary ore, with the goldstones representing the fully weathered derivative. The goldstones are targeted by the artisanal miners due to the fact that all gold has been liberated from the degraded sulphides, being predominantly pyrite as observed in the sulphide stones. It is worth commenting that it is believed that the samples located represent near source samples as they were recovered from dumps surrounding the artisanal pits in this area.
In total 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.
Two sulphide stones were submitted for assay returning grades of 7.5g/t and 4.2g/t.
Figure 4: Goldstones and Sulphide Stones
In addition to the goldstones and sulphide stones recovered from this location, a sample of major significance was also recovered. The partially weathered pyrite dominant massive sulphide sample shows clear folding with sulphides being present along with quartz tourmaline vein material. Common fold fabrics are observed within the sulphides and the host lithology suggesting that sulphide mineralisation took place before or during the folding event. The folding observed is considered significant as it possibly represents classic saddle reef gold traps that can be related to major high grade gold deposits.
This sample, along with the other evidence observed and recorded has helped advance the understanding of the Ferensola gold project enormously and plays an important role in the exploration strategy going forward.
This sample has not been assayed due to its geological significance.
Figure 5: Folded massive pyrite sample with quartz-tourmaline veining
The historic drill core has been resampled and relogged with gold mineralisation relating to pyrite-dominated massive sulphide mineralisation occurring as the matrix to a breccia containing fragmented quartz-tourmaline vein material, flanked by sub-ordinate vein mineralisation. In total 15 samples were taken from holes SDD004, SDD016 and SDD033. SDD004 returned 19.5m grading 9.2g/t. This included 6.1m at 14.8g/t and 5m at 17.4g/t. Hole SDD016 returned 4.3m at 5.2g/t including 0.5m at 21g/t and SDD033 returned 5.3m grading 3.4g/t including 1.1m at 12.3g/t.
Figure 6: High grade massive sulphide mineralisation from the historic drill core
A further significant observation made was that the mineralised zones show a strong magnetite alteration. Magnetite is a highly magnetic iron oxide that upon weathering, converts to the iron oxides haematite and goethite. It is therefore concluded that the haematite and goethite observed in connection with the surficial goldstones is a direct result of the weathering of the primary ore. In addition, it is concluded that the magnetic anomaly observed from the ground magnetics is a result of the magnetite alteration connected with the primary ore zones.
The genetic model postulated relates to fold hosted gold mineralisation where hinge regions control the ore shoots. It is further postulated that the mineralisation is related to shear zones associated with the folding event and that the gold mineralisation phase occurred before or during the folding event.
The re-logging by SRK concluded that a conjectured northwest dipping mineralised structure could exist, highlighting the sub optimal orientation of the historic west inclined drillholes. Of the 34 drillholes completed historically, 33 or 97% were drilled to the west and this may explain the lack of successful drilling, particularly in the northern target covered by the current Exploration Target defined by SRK.