Summary:
The Diamba Sud Project is located within the West African Craton (WAC), in the Loulo Mining district within the Kofi series.
Mineralization at Diamba Sud is classified as Birimian style mesothermal orogenic gold deposits.
Exploration has identified seven gold deposits and several prospects located in the DS1 block. These include the deposits of Area A, Area D, Karakara, Kassassoko, Western Splay, Moungoundi, and Southern Arc, as well as the Gamba Gamba North, Area A North, Area D South, and Kouroudiako prospects. These deposits all form part of a single mineralizing system with local variability influenced mainly by intensity of brecciation, alteration and later supergene processes. The Bougouda prospect is located in the DS2 block.
Gold mineralization (>1 g/t Au) hosted in most rock types, except for weakly altered fine grained sedimentary rocks. Most of the mineralization is hosted in a combination of disseminated pyrite, minor veinlets and hydrothermal breccia cement.
Gold mineralization is both structurally and lithologically controlled and can occur within granites, argillites, conglomerates, marls and carbonates. Supergene enrichment of the orogenic gold deposits (saprolitic) has also taken place within the permit, with significant mineralization of this style present within Area D.
Most of the mineralization at Diamba Sud is hosted within sedimentary units. Hydrothermal breccia zones within Area A host some of the highest grades within the hypogene mineralized zones from Diamba Sud.
Mineralized structures also occur throughout the intrusions in the area, with auriferous pyrite ± carbonate veins exploiting shear zones that cut through the granitoids.
Area A
Area A consists of volcano-sedimentary rocks and hydrothermal breccias folded into an antiform between granodioritic intrusions. It is located south of a northeast-southwest splay of the Senegal-Mali Shear Zone (SMSZ).
Gold mineralization coincides with the breccia–carbonate and breccia–intrusive contact zones. The mineralization trends north–south and at depth is moderately dipping (40–50°) to the west. Near surface, the antiform is refolded towards the east and the mineralized zones are more shallow dipping towards the west.
Mineralization is largely represented by pods and agglomerations of pyrite–gold with occasional chalcopyrite–galena, hosted in strongly albite–hematite ± potassic feldspar– quartz-altered hydrothermal breccias. Although there is a strong geochemical anomaly above Area A, most of the mineralization is seen at depth in fresh rock and there is very little oxide mineralization.
Area D
The Area D deposit is dominated by carbonates (marls, limestone), sandstones, greywackes, tectonic and hydrothermal breccias with granodioritic intrusions to the immediate southeast.
These rocks dip gently (30–45°) to the northwest, but some localized folding is noted. Granodiorite lithologies are seen at depth to the east of the zone where it merges with the western extension of Area A. Locally the rocks appear less fractured and deformed than at Area A, however Area D is notable for the depth of weathering which reaches 70 m in places.
Gold mineralization coincides with the hydrothermal and tectonic breccia-carbonate zones. Mineralization is largely represented by pods and agglomerations of pyrite–gold, hosted in strongly albite-hematite ± potassic feldspar-silica altered hydrothermal breccias, although the extensive oxidation and supergene enhancement to a depth of up to 70 m makes identification of the host lithology and original sulfide species difficult.
Mineralization is continuous as a series of lenticular zones across several drill sections, for 50 to 150 m and has been defined along a 500- m strike with a cumulative cross- strike width of 500 m. Mineralization occurs at depth within the fresh rock, but it is more sporadic and lower grade.
Karakara
The Karakara deposit is located 1.2 km southwest of Area D coincident with the interpreted northeast–southwest-trending structure associated with Area A and Area D.
The geology of Karakara is a series of intercalated carbonate sediments, sandstones and volcaniclastic rocks with a variable dip to the east, and sandwiched to the east and west by granitic intrusions. Folding of the sediments is observed and this may be a control on the mineralization. The weathering profile is shallow at generally less than 5 m.
Gold mineralization is predominantly associated with quartz-carbonate-hematite-albite-pyrite alteration within hydrothermally-altered and brecciated sedimentary rocks near intrusive contacts. Some mineralization in the granites has also been observed as small scale shear zones. Pyrite is the dominant sulfide species with minor associated pyrrhotite.
Mineralization at Karakara has been defined along a 400 m by 50 m zone and remains partially open at depth.
Kassassoko
The Kassassoko deposit is located 2.5 km south of Karakara. Weathering is shallow at less than 5 m below surface.
The geology at Kassassoko is characterized by a series of late-stage northeast–south-west-oriented aphanitic diorite dykes. These dykes intrude near-vertically into the granite host. There is also an amorphous porphyritic diorite and an extensive carbonate sequence is noted to the west.
Mineralization is hosted within the granite, which has undergone alteration to varying degrees of intensity by albite-hematite-pyrite-silica alteration minerals.
Mineralization has been defined along a 600 m strike and 150 m across strike and remains open at depth.
Western Splay
The Western Splay deposit is located approximately 5 km to the southwest of Area A.
Geology is dominated by granite and diorite/gabbro rocks intruding a suite of volcanoclastic tectonic breccias and sedimentary rocks including carbonates, all crosscut by late-phase porphyritic diorite. Gold mineralization is associated with the granite/metasediment contact and hosted in silica-hematite-albite-carbonate-altered limestones and hydrothermal breccias.
Mineralization is largely represented by pods and agglomerations of pyrite-gold hosted in strongly albite-hematite ± potassic feldspar-quartz-altered hydrothermal breccias. Continuity is evident over 350 m along strike, with an extension of up to 250 m across strike. Several sections remain open at depth beyond the deepest drilling to 150 m.
Moungoundi
The Moungoundi deposit is located approximately 1.7 km to the southwest of Karakara.
The main lithologies encountered are carbonates, often associated with magnetized ferrous skarn, tectonic breccias, sandstones and hydrothermal breccia, and granite. These assemblages are crosscut by later sub-horizontal diorite dykes.
Gold mineralization strikes to the northeast and dips to the northwest, becoming subvertical in the east. Mineralization is associated with strong silica-carbonate-hematite-albite alteration, accompanied by pyrite, and is mostly hosted by tectonic breccias, carbonates and hydrothermal breccias along the contact zones of the intrusive bodies.
Southern Arc
Located approximately 4 km south of Area A.
The main lithologies comprises an intercalated sequence of variably porphyritic diorite, volcaniclastics and carbonate/limestone units with extensive tectonic and hydrothermal breccia development, and extensive metasomatism and hematitic alteration. Weathering is shallow to generally less than 5 m depth.
Gold mineralization is interpreted to strike northeast and dip 30–50° to the northwest, in the east. Mineralization is associated with strong silica-carbonate-hematite-albite alteration, accompanied by pyrite, and is mostly hosted by tectonic breccias, carbonates and hydrothermal breccias.
Mineralization has been defined over an area of 750 x 300 m to a depth of approximately 150 m where it remains open at depth and along strike.