This study area is located on the boundaries of three perimeters operating independent Gold operations referred to respectively ‘ NGARI, ‘ NGARI – SEEKOTO ‘ and ‘ TINKOTO-SOU. These three sites are located at approximately 15 km to the Northwest of Kedougou and cover a total area of 150 HA divided into 50 hectors each. They are defined by the points of coordinates, of UTM WGS 84 28 ,
Geological and Tectonic Context
Work of BALOCH (1963, 1966, 1987) have permit to subdivide the training birrimiennes of Eastern Senegal in two super groups willing in bands elongated NNE – SSW with West in is (Fig.4, 5):
- Super Group of Mako with dominant volcanic associated with plutonic and hypo volcanic and inter laminates together with a volcano – detrital to sedimentary ;
- Super Group of world Dalema to dominant sedimentary formed from training detrital and sillico-carbonate, cut by a volcanic intermediate very developed.
These formations are associates of the granite supracrustal flush under form of batholiths composites. It is batholiths of Kakadian and from Saraya, put in place respectively in the of super groups of Mako and training World – Dalema. An importance aspect is the presence of granites post-tectonic Calc – alkaline (Tinkoto, Sambarabougou, Mamakhono, Soukouta, etc.), with their processions dykes , which the development place seems intimately related to the process hydrothermal of training the mineralization Gold primary. Perimeters are found in outskirts is of Super Group of Mako. It constitutes the Western part of the button half of Kedougou – Kéniéba region.
Table 4 : estate of sequences litho-structural of super Group of Mako, from the mission Soviet (1972 – 1973).
|G ROUP Of K HOSSANTO (1800M )||G ROUP From B EROLA (1300 – (1400 M )||G ROUP Of O UASSA (1600 M )|
|Serito-shale with alternation of stoneware quartz o - feldspathic and stoneware tuffaceous||Rocks volcano - sediment, sandstone and shale tuffaceous||Flows and sills of basalts amphibolitized, dykes of gabbro, diabase with local of andesites|
|Flows diabase (little developed), andesites with of rare acid volcanics||Flows and sills of diabase, andesite, gabbros, rocks acid (rare)||Lava acid little represented
|Conglomerates inter laminated.||Rocks volcanic dominant pres - |
|Stoneware coarse and stoneware tuffaceous.|
Fig. 4: Geological Map and Diouras, Pasmi 2008.
The area of exploration is set in the limit of the anticlinorium from Mako. The limits of this anticlinorium are set to go in areas of faults abyssal :
- West is the area of faults deep bordering the shear area of Sabodala where anticlinorium of Mako has a contact tectonics with the batholith of Kakadian.
- The East, is the area of faults abyssal that fixed the edge West of synclinorium world. The width total of the anticlinorium is estimated at more than 25 Km; its length, after the outcrops of the series of Mako on the geological map, fact more of 60 Km.
Fig. 5 : Context geological perimeters of prospecting, extract of the map to the 1 : 200 000.
This sector distinguishes three main groups faults:
The faults syntectonic birrimiennes that border main megastructures folded such that the fault components corridors of deformations of Sabodala, Khossanto and World ; These faults are often staked by a dykes of Gabbro, Diorite, porphyry quartz or albitite. The faults post tectonic (post orogenic) sublatitudinales or NW (120 – 160 °), often met by of breccia silicified and sulphurized (oxidized en surface) and of quartz Lode. These areas of faults are very visible on the aerial, photos than that on the ground. Morphologically, they represent a series of sub-parallel faults of shear and opening, which the extensions individual vary of some hundreds of meters to 6 Km in general. The concentration (density) of these faults is much more forte in the areas d’ expansion ofs granite post – tectonic (Mako, Tinkoto, Falombo, Mamakhono, Dendifa, Sambarabougou, etc.), link genetics likely between these structures tectonic and magmatic with the mineralization gold.In effect, in the limits of area influence of faults post – orogenic NW, especially in limit of the rocks competent such that the diorites, on note very often the development network relatively dense of vein metric to UHF of quartz, quartz – tourmaline, quartz-carbonate accompanied by their processions of Stringer centimetre to millimetre directions and from dips, that can be assimilated to real shears areas or stock works. The faults relatively recent and local, scope limited, which in the most of time complicate the structures cited, in the winning. The long of these accidents tectonic is observed often an amplification of process of remobilization secondary oxidation, and of leaching in the parties little deep of the under – floor.