Summary:
Sanankoro is located on the leading western edge of the Yanfolila-Kalana Volcanic Belt, which is the western-most expression of the cratonic Baoulé-Mossi domain, on the major transcrustal margin with the Siguiri Basin. There is major deep-seated architecture across the district which links the major gold mines at Siguiri, Lero, Tri-K, Kalana and Yanfolila.
On a project scale, Sanankoro is characterised by the 2 km wide Sanankoro Shear Zone, which can be traced over 30 km from Kabaya South in the western Yanfolila Mine to north of the Niger River beyond Selin and onto Karan. Within the project area, each of the prospects are underpinned by a strong linear parallel, and where strong mineralisation is developed, a pronounced localised northeast-southwest focused zone of en-echelon veining and associated sulphide development.
There are five main areas which currently define the Sanankoro Gold project, which in order of significance are Selin, Zone A, Zone B, Zone B North, and Zone C.
Selin is hosted on the eastern margin of the Sanankoro Shear Zone in the north-eastern corner of the Sanankoro permit. The Selin deposit has a typical interference node control but with the additional positive impact of a strong, rheological diorite intrusive host. The gold geology at Selin is anchored along this linear, en-echelon or possibly folded, diorite igneous intrusive which cores the volcaniclastic thrust assemblage and focuses the gold deposition.
Recent core drilling into Selin has enlightened the genetic model for the deposit by discovering four to six multiple early/pre-D3 dykes of diorite intruding the 65-80° west dipping axial trace of a western hangingwall F3 anti-form on this major reactivated D2 east-verging thrust. The >100 m wide Selin Shear Zone may be a regional back-thrust and the dominant eastern margin of the regional west-verging Sanankoro Thrust. The largest diorite unit is demonstrably discordant and sits immediately west and adjacent to a major early ductile, 10-30 m wide footwall carbonaceous shear. Progressive deformation has folded, warped and possibly cross-faulted the diorite units prior to gold deposition. The early footwall shear fabrics are overprinted by later semi-brittle to brittle graphitic faults which locally convert all protolith to graphitic schist on sub-metre scale. The diorite units exhibit multi-phase veining interference and sulphide development. The dominant sulphide is pyrite with occasional arsenopyrite and a scattering of chalcopyrite. Alteration minerals are predominantly sericite, silica, fuchsite, ankerite, graphite and calcite.
Zone A is located at the southern limit of the 11.5 km mineralised corridor, which forms the Sanankoro Project. Zone A is the southern-most expression of the 010° trending central axis of the Sanankoro Shear Zone, which sits 900 m west of the Selin Boundary Shear and hosts the 5.8 km chain of open pit resources from Zone A through Zone B1, B2, B3 to Target 3. The deposits of this central trend verge westward mimicking the regional sense of thrusting.
Zone B is the strike extension of Zone A, located 800 m to the north. The Sanankoro Main Trend runs for 6 km from south end of Zone A to the north end of Target 3. Detailed sectional drilling is required along the length of this major generative gold system. The local structural facing and stratigraphy of Zone B is very similar to Zone A with the western footwall sequences hosting more crystalline volcanic tuffaceous units and the eastern, hangingwall assemblages being more basinal sediments. Zone B hosts an impressive scale of hydrothermal activity and the broad horizontal widths of mineralisation observed in the recent drilling bodes well for future discovery potential along the central and southern sections of the Sanankoro Main Shear Zone.
Zone C is located 650 m southwest of Zone A on the parallel, >7 km long Sanankoro West Shear Zone (SWSZ) which can be traced along a chain of surface workings to the Excavator Prospect, 1.5 km north-northwest of Target 3. The SWSZ is high in the priority list for drilling in the 2022 program and a number of SWSZ targets, beyond Zone C, will be tested for surface potential.
Zones A, B and C deposits are identical in style and typical of Siguiri Basin deposits, fold-thrust controlled within pelitic and psammitic sediments and very deeply weathered (>120 m from surface). There is a highly evolved weathering profile with a pronounced 8-10 m thick duricrust-laterite ferro-cap, grading downward into a well-developed mottled zone to 20-25 m depth and remains highly weathered until beyond 140 m vertically within the central mineralised fault zone. Zone B1 has extremely deep weathering with shallow oxide densities measured to depths of 190 m down-dip within the ore zone trough.
All the host oxide lithologies are weathered to kaolin with only highly corroded quartz vein material remaining in-situ to mark the main gold faults. Diamond core shows the host lithologies to be predominantly variably grained basinal pelites and sandstones with minor horizons of small quartz clast, matrix-supported greywacke inter-bedded within the sequence. A minor intercept of diorite has been identified but does not form an important control to the mineralisation currently drill tested at Zone A or C. The primary sulphide is pyrite disseminated around central vein networks and enveloped by a broader hydrothermal halo of silica flooding, sericite and ankerite.
Dimensions
The Selin mineralisation model is 2.8 km in length along strike, a maximum of 270 m in depth, and is anything from a few to 50 m wide. Selin is reported to a maximum depth of 220 m below surface.
The Zone A mineralisation model is 1.2 km in length along strike, a maximum of 245 m in depth, and is anything from a few to 50 m wide. Zone A is reported to a maximum depth of 190 m below surface.
The Zone B mineralisation model is 1.7 km in length along strike, a maximum of 215 m in depth, and is anything from a few to 50 m wide. Zone B is reported to a maximum depth of 180 m below surface.
The Zone C mineralisation model is 750 m in length along strike, a maximum of 160 m in depth, and is anything from a few to 50 m wide. Zone C is reported to a maximum depth of 120 m below surface.
The Zone B North mineralisation model is 1 km in length along strike, a maximum of 130 m in depth, and is anything from a few to 50 m wide. Zone B North is reported to a maximum depth of 110 m below surface.