IAEA World Distribution of Uranium Deposits (UDEPO)

Uranium Deposit Report

Deposit :	Ebba Sud
Country :	Niger

General Information
Geological District	Arlit
Geological Region	Arlit
Political/Geographical Province	Agadez
Last Data Update	2009-01-01
Owner(s)	33 %, COGEMA
	33 %, OURD
	33 %, ONAREM
Operator	COGEMA
Synonym Name(s)	Afasto Sud

Technical Information
Tonnage Range (t U)	5,000 - 10,000
Grade Range (% U)	0.20 - 0.50
Deposit Status	Development
Current Processing Plant
Cumulative Production (t U)	0
Production Period
Produced Grade (% U)	0
General Remarks

Geological Information
Deposit Type	Sandstone - Tabular
Geological Setting	Uranium deposits from the Arlit-Akouta district are located along the eastern margin of the Tim Mersoi intra-cratonic Basin, near the volcanic Air massif. The sedimentary cover, unconformable on Precambrian granites, comprises : - at the base, three carboniferous units, Terada (Lower Visean) and Lower and Upper Tagora (Upper Visean). All the COMINAK deposits are situated in the Guezouman Formation of the Lower Tagora and all the SOMAIR deposits are located in the Tarat Formation of the Upper Tagora, - the Izegouandane unit (Permian) divided into four formations. The Moradi deposit is located in the Moradi upper formation, - the Aguelal and Goufat units (Trias), - the Wagadi unit (Jurassic), with the Imouraren deposit, - the Dabla unit on top (Lower Cretaceous). The total thickness of the sedimentary formations is around 1500 m. The Guezouman Formation (0-180 m) starts with a polymict conglomerate (2 m) and consists of medium to fine-grained isogranular quartz sandstone beds. Argillaceous breaks are very rare. The Guezouman sedimentation was mainly controled by basement structures consisting of N 80° E and N 130° E faults and N 40° E folds.
Age of Mineralization	Pb-Pb age = 338 +/- 5 My (Devillers & Menez, 1977) U-Pb age = 193 Ma (Forbes, 1988) U-Pb age (207/206) = 144 +/- 15 My (Turpin et al., 1991)
Mineralization	Ore Mineralogy: pitchblende, coffinite, V-rich chlorite, montroseite, jordisite, pyrite, chalcopyrite, blende Ore Controls: Pyrite and organic matter rich layers in basal sandstones channels
MetallogenicAspects	A small amount of uranium may have been derived from the erosion and leaching of the Air crystalline basement, but the major part probably resulted from the volcanic activity. Major preconcentrations were certainly penecontemporaneous with the sedimentation with uranium precipitation within the fluvio-deltaic environment in the favorable areas with a high organic matter content. Uranium remobilisation by oxidizing waters penetrating the sandstones both from the east and from the west (the Arlit fault) contributed to give the deposit its present shape, partly of stratiform type and partly of roll front type. No particular concentration of uranium minerals along faults has been identified.
Age of Mineralization	Pb-Pb age = 338 +/- 5 My (Devillers & Menez, 1977) U-Pb age = 193 Ma (Forbes, 1988) U-Pb age (207/206) = 144 +/- 15 My (Turpin et al., 1991)
DepositShape	While the channel determines the general shape of the uranium deposit (tabular, elongate lenses), the sedimentary structures and the lithology affect its detailed distribution.
DepositDimensions	Deposit Depth Top: 200 m Deposit Depth Bottom: 300 m
GeologicalRemarks	Eastern Tim Mersoï Basin, foothills of the Aïr basement. Cambro Silurian to Miocene sediments : Terada group Tagora group “Continental intercalaire”
Metallogenic Aspects	A small amount of uranium may have been derived from the erosion and leaching of the Air crystalline basement, but the major part probably resulted from the volcanic activity. Major preconcentrations were certainly penecontemporaneous with the sedimentation with uranium precipitation within the fluvio-deltaic environment in the favorable areas with a high organic matter content. Uranium remobilisation by oxidizing waters penetrating the sandstones both from the east and from the west (the Arlit fault) contributed to give the deposit its present shape, partly of stratiform type and partly of roll front type. No particular concentration of uranium minerals along faults has been identified.

Uranium Deposit Report

Deposit :	Ebba Sud
Country :	Niger

General Information
Geological District	Arlit
Geological Region	Arlit
Political/Geographical Province	Agadez
Last Data Update	2009-01-01
Owner(s)	33 %, ONAREM
Operator	COGEMA

Technical Information
Tonnage Range (t U)	5,000 - 10,000
Grade Range (% U)	0.20 - 0.50
Deposit Status	Development
Current Processing Plant
Cumulative Production (t U)	0
Production Period
Produced Grade (% U)	0
General Remarks

Uranium Deposit Report

Deposit :	Ebba Sud
Country :	Niger

Geological Information
Deposit Type	Sandstone - Tabular
Lithology	At the base of the Guezouman formation, Teleflak polymict conglomerate (<2m) is composed of rhyolites pebbles, sandstones, quartzites and phosphorous gravels cemented by pyrite and with a primary sandy-clayey and carbonated matrix. This level is erosive through the Akokan unit (UA/UL) (Lower Terada serie). At the top of this conglomerate, Guezouman sandstones (15-35m) are coarse-grained with oblique stratifications at the bottom. In the upper part, they are medium to fine-grained, isogranular, grayish white. The interstitial phase is enriched in calcite and pyrite. This upper part can be divided in 2 main units U1 (with 4 sequences N1-N2-N3-N4) and U2 (with 2 sequences). Guezouman alternances (or unit U3, 10-15m) correspond to the last Guezouman unit, with fine-grained, grayish or bluish white sandstones ans grayish black clayey siltstones.
Tectonics	Arlit – In Azaoua “lineament” and N30E structures. Left lateral transtension model active from Carboniferous to Mesozoic Compressional episode Paleogeography = marine to deltaic and continental
Alteration	Kaolinization, Hematisation, Chloritisation
Host Rock Age	Upper Visean TAGORA serie GUEZOUMAN formation
Age of Mineralization	Pb-Pb age = 338 +/- 5 My (Devillers & Menez, 1977) U-Pb age = 193 Ma (Forbes, 1988) U-Pb age (207/206) = 144 +/- 15 My (Turpin et al., 1991)
Ore Mineralogy	pitchblende, coffinite, V-rich chlorite, montroseite, jordisite, pyrite, chalcopyrite, blende
Mineralization Description
Ore Controls	Pyrite and organic matter rich layers in basal sandstones channels
Metallogenic Aspects	A small amount of uranium may have been derived from the erosion and leaching of the Air crystalline basement, but the major part probably resulted from the volcanic activity. Major preconcentrations were certainly penecontemporaneous with the sedimentation with uranium precipitation within the fluvio-deltaic environment in the favorable areas with a high organic matter content. Uranium remobilisation by oxidizing waters penetrating the sandstones both from the east and from the west (the Arlit fault) contributed to give the deposit its present shape, partly of stratiform type and partly of roll front type. No particular concentration of uranium minerals along faults has been identified.
Deposit Shape	While the channel determines the general shape of the uranium deposit (tabular, elongate lenses), the sedimentary structures and the lithology affect its detailed distribution.
Deposit Width
Deposit Length
Deposit Thickness
Deposit Depth	Top = 200 m ; Bottom = 300 m
Geological Remarks	Eastern Tim Mersoï Basin, foothills of the Aïr basement. Cambro Silurian to Miocene sediments : Terada group Tagora group “Continental intercalaire”