Geological Setting

The area is located within the boundaries of a wide corridor of deformation, birimian, parallel to that of the Sabodala deep fault zones. The Interior of this corridor, developed shears-areas, made up of veins and veins of quartz, of different sizes and directions. The perimeter of Tinkoto Sou, occupies an area laterite eluvionnaire, where you can watch pieces and blocks of veins and veins dismantled and decayed. The Mineralogical study, performed on this ore by PASMI (Mining Sector Support Program) for gold panning and the Director of Mines and Geology Laboratory (Senegal), had enabled us to obtain the following results:

  • The gold ore is of nature per, greyish, bluish to brownish; eye is composed mainly of quartz, plagioclase, chlorite, oxides and iron hydroxides and carbonates.
  • The content of total gold for the sample analyzed is 4.82 g/t, while that of the different fractions, varies between 1.99 and 15,22 g/t; (See Figure 4.0.A & 4.0.B).
  • Crushing and quartz ore spraying occurred without noticeable strain. Although the quartz is generally hard and abrasive, the development of systems of cracks (micro-tectonic) in the ore, significantly reduces grinding efforts. The gold quality and weight is 22/ 23 carats.

The substratum of the Senegalese territory is made up of two major geological domains: the Sedimentary Basin, which occupies more than 75% of the territory, and the Precambrian basement, representing the country’s south east.

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SEDIMENTARY BASIN

The Senegal Basin occupies the central part of the Northwest African Coastal Basin (MSGBC Basin), which extends from the Reguibat ridge at the north end of the Guinean fault. It is typical passive margin opening westward to the Atlantic Ocean and whose eastern limit is represented by the Mauritanides chains. The Senegal Sedimentary Basin is a Mesozoic Basin. It has gone through a complex history in relation to the pre-rift (Upper Proterozoic to Paleozoic), the Syn-rift (Permian to Triassic) and the Post-rift (Central Jurassic to Holocene) at different stages of development of the Basin. Most of the outcrops of the basin are composed of recent sandy covers. Maestrichian and Eocene formations outcrop, however, in the peninsula of Cape Verde while Eocene outcrop in the valley of Senegal River. The description and knowledge of the Basin have been made possible largely thanks to hydraulic and oil drilling data. The Secondary formations include Palaeocene zoogenic limestone exploited at Bandia and Pout by cement plants and aggregates producers. They include also Maestrichian sands, clays and sandstones. Paleocene and Maestrichian formations are also known to be major aquifers that contribute significantly to the water supply for cities and villages in the basin. Tertiary formations hold into the Eocene compartment, significant resources of phosphates, limestone, attapulgite, clay and ceramics, solid fuels, etc. A major part of the basin is covered with superficial Quaternary formations, which in the middle and recent parts are characterised by fixed red sand dunes, semi-fixed or alive yellow and white dunes. These dunes, often exploited as building materials around urban centres, constitute also important reservoirs of heavy minerals.

PRECAMBRIAN BASEMENT

The Precambrian basement formations are constituted at the west by the Mauritanides range bordering the eastern part of the Sedimentary Basin and in the east by the Palaeoproterozoic volcano-sedimentary sequences of the Kedougou- Kenieba inlier. The formations of the Mauritanides chain are Herycian age and constitute one of the mobile areas of the West African craton. They are known for their numerous copper and chromium occurrences which, in Mauritania, constitute the important copper deposits of the Akjout Region. The Palaeoproterozoic volcano-sedimentary sequences, mostly known as Birimian formations, are of great metallogenic importance, as far as they contain the major ore deposits discovered in the region. The Kedougou-Kenieba inlier is limited to the west by the Mauritanides chain, and on all other sides by the Upper Proterozoic and Cambrian sediments of the Basin of Taoudenni. The Kedougou-Kenieba inlier is interpreted as an accretion of north-easterly trending Birimian age volcanic terrains. It includes two major geological structures, the Senegal-omalian Fault and the Main Trans-current Zone (MTZ) to which gold mineralization is associated. Recent combination of geological studies including field work, and structural modelling and of detailed core logging have improved the understanding of the geological structure of the MTZ. Two main zones of mineralization have been further refined based on the latest geological model. Geological studies suggest that mineralization in the prospective Sabodala volcano-sedimentary belt and the Senegal-Malian shear zone is associated with an altered and sulphidised gabbro, which has intruded along the main structure, and a typical shear zone hosted, where a structure has developed at the contact between a package of volcaniclastics and sediments. A lapilli tuff acts as a prominent marker horizon in the hangingwall of mineralisation. The inlier is divided into three main stratigraphic units from west to east: the Mako Super group, the Diale Super group and the Daléma Super group.

  • The Mako super group hosts Sabodala deposits located in an area of intense shearing and silicification associated with pyrite gold mineralization. It forms a north-east tectonic structure, turning to north-west near the border with Mali, in the north. Typical lithologies include basalt flows; often carbonate alterations and minor volcaniclastic intercalations, magnesium basalt or komatiites, ultramafic sub-volcanic intrusions (pyroxenites) and numerous massive biotite and amphibole granitoids. These granitoid intrusions are suspected to have been ‘heat engines’ which sparked off the deep mineralized magmatic fluids related to the belated mineralisation in the Kédougou-Kéniéba inlier.
  • The Diale Super group, located between the Mako Super group and the western edge of the Saraya granite is weakly metamorphic. It includes extensively folded formations, deposited after those of the Mako Super group and consisting of shale, greywacke, quartzite and volcano détritic rocks.
  • The Dalema Super group, located between the Saraya granite and the Faleme river, continues to Mali in its eastern part but disappears in the South under the Segou Madina Kouta the series. It is composed of volcano-sedimentary schist and grauwacke rocks. These Birimian formations are affected by syn, late and post-tectonic granite intrusions.

senegalThe Precambrian basement is a metallogenic province of major importance for Senegal, which hosts numerous deposits and anomalies of gold, iron, uranium, lithium, tin, molybdenum and nickel in Birimian formations, and copper and chromium in the Mauritanides range. In addition to these metal resources, there are large marble and other ornamental rocks deposits, but also non metallic indices and deposits of barytes, kaolin.

fig4-dNational mineral database

Under PASMI (from April 2007 to December 2008) the government created a Mineral Documentation and Mining Cadastre Centre (CDCM). The project helped set up an archive center for the mining industry and reinforce Senegal’s capacity to implement a mineral title management system using a new mining cadastre. Since the official inauguration on December 17, 2008, the cadastre has operated efficiently. The project also helped implement a geographical information system for data management of the country’s mineral resources, and a survey was successfully carried out to approve basic norms of environmental management for mining operations.

Geological Mapping: sedimentary basin

carteThe Senegal Basin is the central part of the Mauritania-Senegal-Gambia-Bissau-Conarky (MSGBC) basin which stretches from Mauritania to Guinea Bissau along the coast of West Africa. Under the EU funded PASMI, the government of Senegal is presently undergoing detailed geological mapping of this basin. This mapping project aims to produce a standard, print-on-demand geological map of this geologically complex and highly prospective Palaeozoic basin. Maps will be available in 1:500,000 for the whole basin, in 1:200,000 for the northern part and for the Cap Vert peninsula, in 1:50,000 multi-layers map sheets for the west of the meridian 16°40’W and in 1:20,000 multilayers map sheets for the west of the meridian 17°10’W. Midway reports indicate many significant changes and enhancements to the understanding of local and regional geology. This very ambitious geological mapping program, from data collection to providing several final deliverable map quadrangles, will take about 24 months and is scheduled to deliver final products by end-March 2009.

sensgal1Geological mapping: SE Senegal

This important project started in May 2008, and aims to update, through a geographical information system, the geologic and metalogenic cartography of south-eastern Senegal (last updated in 1960). This revision will take into account the numerous and important data accumulated through mineral exploration programs and works carried out by researchers and academics since then. At the end of the project in 2010, geological and structural maps will be available in a 1:200,000 map sheet covering the whole Precambrian basement, and in 1:500,000 metalrgenic map sheet for the same terrains. These maps to which will be annexed the explanatory notes will be of a certain contribution for the mining exploration of south-eastern Senegal.

Artisanal Mining

This project focuses on gold artisanal miners in the Kedougou region. With government support, the project provides direct support to artisanal miners, particularly to the more vulnerable children, women and elderly. This project aims to integrate artisanal miners into the formalized mining sector, to improve techniques and livelihoods.

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