Deba concession located in the Liptako area of Niger is at the northeastern tip of the major West African gold belt extending from the Atlantic coast in Ghana to the Niger River. The Liptako area is within the Main Shield, itself part of the Western African craton and consists predominantly of Lower Protorozoic Birimian formations composed of volcano-sedimentary belts that have been intruded by granitic rocks, fig.1. The Deba concession is within the Sirba Belt and currently covers an area of 275 km².
The area can be reached via the RN6 paved road Niamey-Torodi (60 km) and from there by a bush trail (90 km) up to the village of Kakou located in the middle of the concession. The travel time is about three hours and a four wheels drive vehicle is required.
Canadian International Development Agency (CIDA) (1977-78)
An airborne magnetic/radiometric survey over the whole Liptako area has been funded by CIDA. Survair Ltd carried out the survey in 1970 and Tera Surveys did the data interpretation.
United Nations Development Program (UNDP) (1990-91)
An airborne electromagnetic/magnetic Geotem survey over the Sirba and Tera belts has been funded by UNDP. The ‘Compagnie Générale de Géophysique’ (CGG) flew the survey and has presented an interpretation report with ground follow up recommendations. Maps produced are for the electromagnetic anomalies, the residual magnetic field, the decay rate amplitude, the channel 8 amplitude and the data interpretation.
Onarem - CIDA (1984-89)
A CIDA project has enabled Onarem to carry out geological mapping at 1:25 000 in the area located between the Sirba River and the western border of the Deba concession, soil samples at a grid of 200m x 250 m and termite mounds samples were also collected.
An artisan mining site near the Kokolougou village has been evaluated by twenty drill holes totaling 2287 meters, the quartz vein one meter wide and 425 meters long is not economic.
Japanese International Cooperation Agency (JICA) (1990-94) March 1995 Report
JICA has collected soil samples at a grid of 500m x 500m over almost all the perimeter of the Deba permit, the area not covered is in the SE corner of the permit. The main clusters of gold anomalies are in Deba, Kokolougou, Sefa Nangue, Alfassi and Bolsi areas.
Core drilling over 5126m has been executed over the Sefa Nangue prospect, the resource evaluation by JICA is the following:
Depth Tons Metal content Average grade
Au (kg) Ag (kg) Au (g/t) Ag (g/t)
100m 1.3 Mt 2592 240 2.00 0.19
150m 1.9 Mt 3847 325 2.03 0.17
200M 2.4 Mt 4862 457 2.06 0.19
Pioneer Goldfields (1996-99)
Work carried out includes an aerial photographic survey over the whole permit, geological and structural mapping with maps at 1:50 000, 1:20 000 and 1:5000, a photo-geologic interpretation, collection of soils and rocks samples and 28 trenches totaling 6299m.
The regional geochemistry at a grid of 100m x 500m has been done over an area of 365 km², 9052 soil samples and 1180 rock samples have been collected. Soil geochemistry at a grid of 50m x 100m has been carried out over Deba, Wadata, Sefa Nangue, Kokolougou, Alfassi, Kakou, Tanderia, Torse, Goro, Bilabe and Dogona areas.
The main gold intersections in the trenches were :
Deba Trench 1 1.11 g/t – 6m, 0.91 g/t – 15m
Sefa Lame Trench 6 2.13 g/t – 6m
Trench 14 0.42 g/t – 11m, 0.36 g/t – 10m, 0.44 g/t – 17m
Tanderia Trench 63 1.71 g/t – 10m
Sefa Nangue Trench 74 1.04 g/t – 4m, 4.62 g/t – 5m, 1.29 g/t – 7m
‘Fond d’Aide et de Coopération’ (FAC), 1989-92
The area between the Sirba River and the eastern border of the Deba permit has been covered by geological mapping at 1:50 000, hammer prospecting, geochemistry and geophysics. This work has been carried out by French geologists with the participation of local geologists from the Ministry of Mines.
The base metal showings at Kakou, Kakou East and Bolsi have been identified during the hammer prospecting of 1991/92. The three vertical holes drilled over the Kakou prospect totaling 145m did not yield any significant results.
Ashanti Gold (2000-01)
Ashanti has completed 239 drill holes (RAB) totaling 6511m, the average depth is 27m (5m to 38m) along an inclination of 50°. Fire assays were done on 4m composite samples, appendices 1-2. The main gold values detected in the drill holes (S) along profiles (P) are:
P1-15 S7 20-24m (3288 ppb) 24-28m (897 ppb)
S8 >100 ppb
P16-30 S20-21 >100 ppb
P39-46 S43-45 >100 ppb
P129-143 S 135 >100 ppb
P147-163 S153-162 >100 ppb
S154 26-30m (5979 ppb)
S161 22-26m (81720 ppb) 26-30m (3395 ppb) 30-34m (130 ppb) 34-38m (1231 ppb)
P180-194 S182, 186 >100 ppb
P195-214 S201-202 >100 ppb
S203 12-16m (3794 ppb) 16-20m (799 ppb) 20-24m (151 ppb) 24-28m (855 ppb) 28-30m (1299 ppb)
P221-229 S228 >100 ppb
The interesting zones are S7-S8, S153-S162 and S201-203, the potential width of these zones reaches 900m along S153-S162 where hole spacing is 100m.
Summary of the Geology, Deba permit
The Deba permit is located on the southeast flank of the Sirba volcano-sedimentary belt, one of the three belts of Lower Proterozoic Birimian (1.9 to 2.1 My) greenstone formations to the SW of Niger. The two main geological units are the block of granites to the SE and the block of volcanics to the NW.
The block of volcanics is characterized by folded formations composed of an alternation of predominant metavolcanics and metasedimentary rocks that are crossed by several syntonic and postectonic intrusions (postectonic intrusions being more favorable to gold mineralization). Several subvolcanic intrusions and basic sills (gabbro, dolerite, basalte) are present in this block.
The Lower Birimian is characterized by greenstone formations, olistostromes, black schists and chemical rocks. The black schists could have had a metallogenic importance as a chemical trap favorable to the gold precipitation from mineralized fluids.
The Higher Birimian consists of two formations, one of flysch composed of an alternation of sandstone and siltstones and one of black aleuronites and sandstone.
Tarkwaians deposits of sandstones and conglomerat along narrow structures 20 to 30 meters wide and associated to NNE-SSW shear zones, particularly along the Samira-Bolsi fault corridor.
The intrusions are early syncinematic such as the gabbroic complex of Dogona and the granitic complex of Kodiaga located in the SE corner of the permit. The late postectonic intrusions are subdivided in two units ; the granodiorite/granitic complex of Kakou and the monzonitoid complex of Sefa-Seyni particularly favorable to gold mineralization
Two main grids have been established on the Deba license.
Kokoloko –Sefa Nangue
The South and North western corner of Kokoloko Sefa Nangue grid show two low to medium anomalies not well trended but seem to be N50 varying from 400 to 600 meters long.
Deba grid shows two anomalies. The first one trending N60 along the baseline orientation is a very low anomaly (22 to 33 ppb) about 2000 meters long and 200 to 400 meters wide. This anomaly was tested at the eastern portion by both Pioneer and St. Jude with little success, however their remains a 1000 meter untested portion.
The second trend is orientated EW to N120 for over 1000 meters. This anomaly was also tested by St. Jude and Pioneer at the eastern end, with approximately 600 to 800 meters remaining untested. This trend seems very interesting as it suggests a structural control of the mineralization.