Kalana Holdings (formerly known as Avnel Gold Ltd.), a wholly-owned subsidiary of Endeavour Mining, has an 80% interest in Société des Mines d'Or de Kalana S.A. (SOMIKA), the holder of the Permit. The Government of Mali holds the remaining 20% beneficial interest in SOMIKA.
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Summary:
Kalana and Kalanako are orogenic gold deposits lying within a Birimian-aged volcano-sedimentary sequence of rocks.
The Kalana Project area lies along the western margin of the Bagoé Basin toward the southern extremity of the Yanfolila-Kalana volcano-sedimentary belt which forms the border with the Siguirri Basin in Guinea. Volcanic rocks, primarily basalt, are found in small domains in the eastern and westerns parts of the Basin, pinched along orogenic shear zones. A large Eburnean felsic intrusion, the Bougouni Batholith, occupies the central part of the Bagoé Basin. Small intermediate intrusions, commonly diorite and granodiorite, are mainly found in the eastern part of this area, as well as in the Kalana area. All rock types in the Basin are cut by (Neoproterozoic or potentially Jurrassic) dolerite dykes that are dominated by easterly, northeasterly, and north-northwesterly trends.
Gold mineralisation in the southern portion of the Bagoé Basin appears to be controlled by basinmargin parallel faults that generally trend northwest to north. The Bagoé Basin is host to the multimillion-ounce gold deposits at Morila and Syama.
The Kalana Project Area is covered by an extensive lateritic profile, characteristic of the Guinea Savannah climatic zone, obscuring the bedrock. The depth of weathering ranges from 30 m to 130 m.
The Kalana Project gold deposits are hosted by volcano-sedimentary rocks of the lower part of the Upper Birimian Group. The (meta)-sediments consist of turbidite sandstone-siltstone (+/- tuff) sequences. The sandstone is fairly massive and medium-grained and the siltstone is finely laminated and locally graphitic. They are situated on the steeply dipping western limb of a regional syncline with folds plunging steeply to the north.
The Kalana gold deposit is composed of mesothermal gold mineralisation hosted mainly in quartz veins following shallow dipping and vertical dykes adjacent to small intrusions emplaced in a subvolcanic environment. The mafic intrusions played a key role as a source of heat flow driving the hydrothermal cell at the origin of local deuteric alteration and sulphide-carbonate metallotects (i.e. arsenopyrite, pyrrhotite, pyrite, chalocopyrite, ankerite and scheelite). The Kalana deposit can be subdivided into four geographical areas:
- Dynamite Trend – Located northeast of the main Kalana deposit. Does not host significant gold mineralisation.
- Kalana North – Hosts 1st, 2nd and 3rd Order Veins. Significant amount of historical underground workings on 1st and 2nd Order veins.
- Kalana Southwest – Hosts 1st Order Veins only and the majority of the historical underground workings.
- Kalana Southeast - Hosts 1st Order Veins only.
The Kalana deposit hosts an east-west sigmoidal elongated diorite dyke with two major bodies that have been traced to a depth of 600 m intruding the Birimian rocks. The intrusion is approximately 180 m by 250 m in the main body and 150 m by 750 m to the east (Kalana Southeast). The two parts of the intrusion are surrounded by a contact metamorphic aureole (hornfels) up to 30 m wide.
The Kalana gold mineralisation occurs within stacked quartz veins and stockworks hosted by the Birimian age metasediments and the intrusive diorite stock. The northwest-southeast trending mineralised vein system extends over an area of approximately 1,200 m east by 1,000 m north. Mineralisation is restricted to a block bound by northwest and northeast trending faults. Mineralisation has been identified to a depth of 600 m, the limit of current drilling.
Kalana hosts four types of gold mineralisation:
- 1st Order Veins - The flat dipping quartz veins account for approximately 75% of the mineralisation identified at Kalana. Generally, these veins are controlled within a system of sub-parallel, en-echelon fractures that dip predominantly to the east or southeast. These veins pinch and swell significantly - the average vein thicknesses ranges from 0.1 m to more than three metres.
- 2nd Order Veins – The 2nd Order Veins are found north of the diorite stock, dipping 45o to the south striking N60 in the north and N40 in the south of Kalana North. They are also present in Kalana Northeast. The 2nd Order Veins partially overprint the 1st Order Veins. These veins are regarded as “relay structures” sandwiched between upper and lower 1st Order Veins (i.e. mineralised Riedel structures). The junction of 1st and 2nd Order Veins are typically enriched in gold (normally modelled / attributed to the 1st Order Vein).
- 3rd Order Veins – The thin 3rd Order Vertical Veins have only been identified in diamond drill holes and underground workings in Kalana North. Six sub-vertical cylindrical zones approximately 50 m in diameter and 150 m deep have been delineated to represent zones with 3rd Order Veins. The 3rd Order sub-vertical vein zones appear to be aligned northwest-southeast and northeast-southwest in an “X” shape.
- Stockwork mineralisation at the contact of the diorite.
Kalanako is located approximately three kilometres northeast of Kalana. Several mineralised trends have been established that form a northwest-southeast explored corridor of 1,500 m by 250 m. The deposit occurs along a mineralised geophysical structure (aeromagnetic and ground IP), which remains open along strike. The depth of saprolite and saprock is between 70 m and 130 m, much deeper than that observed at Kalana. Drilling at Kalanako intersected numerous high strain zones, packets of densely laminated quartz veins with sulphides and locally highly altered and mineralised felsic intrusive rocks. The volcano-sediments, shear zones and felsic intrusions are cut by flat dioritic dykes (0° to 20° dipping) that are comparable to those at Kalana.
Kalanako mineralisation is associated with the felsic intrusive rocks and the quartz stockworks that occur along northwest-southeast striking shear zones. Thirty-four veins have been modelled, six of which account for two-thirds of the mineralised volumes (referred to as “major veins”). The veins have an average thickness of 7.2 m down the hole. The sub-parallel mineralised zones are typically five metres to 15 m wide, with strike lengths of 250 m to 500 m, and are steeply dipping to the east. Kalanako typically has high-grade intercepts in the oxide part of the deposit.
Djirila lies approximately 22 km southeast of Kalana. It was discovered by SONAREM in the 1960’s, explored by Avnel Gold in 2004. The saprolite depth is over 70 m, much deeper than Kalana. Mineralisation is associated with high strain zones rich in quartz and quartz veins. Local dioritic dykes can be found.
The majority of the gold in the quartz veins at Kalana is present as free gold with the gold commonly occurring as grains and small nuggets. Fine grained gold is also associated with arsenopyrite in the quartz veins. There is no disseminated gold in the hangingwall (HW) and footwall (FW) of the veins. In the HW and FW of the main veins of a package, there are millimetric veins.