Geochemistry of Sandstone Type Uranium Deposit in Tarat Formation from Tim-Mersoi Basin in Northern Niger (West Africa): Implication on Provenance, Paleo-Redox and Tectonic Setting ()
ABSTRACT
The study aimed at investigating the geochemistry of a sandstone-type uranium
deposit in Tarat formation for provenance, paleo-redox, tectonic setting
in order to propose a geological model of uranium. X-Ray Fluorescence
(XRF) and Induced Coupled Plasma Mass Spectrometry (ICP-MS) analyses
were used to determine the sandstone composition. Major, trace and rare
earth element compositions of the sandstones have been investigated to determine
their provenance, tectonic setting and the influence of weathering
conditions. Field studies of Tarat formation revealed that a major accident
N30° that can be interpreted as an extension of the Austriche accident ensures
the controls of Tarat sedimentation and mineralization deposits and the
presence oxidized zone and reduced zone indicate the direction of circulation
of the mineralized fluids from West to East. The uranium mineralization is
disseminated as pitchblende that gives a yellow color to the sandstone while,
molybdenum mineralization gives a blue color to the sandstone. Results of
the Geochemical analysis indicate that the sandstone-type uranium deposit of
Taratis classified into Protoquarzite (i.e. lithearenite and sublitharenite), arkose,
subarkose, wacke and quartz arenite and varied in their maturity. Their
Rare Earth Elements (REE) pattern displays high light REE over heavy REE,
flat HREE and a significant negative Eu and Ce anomalies and in general
correlated well with the NASC and PAAS average composition. The source
area may have contained quartzose sedimentary rocks. The geochemical data
support deposition in reducing environment of arid to humid climatic conditions rich in organic matter affected by passive margin (PM) tectonic setting
and the sediments are derived from felsic and mafic source rocks. Trace and
REE data as well as the high values of the weathering indices: Chemical Index
of Alteration (CIA), Plagioclase Index of Alteration (PIA) and Chemical Index
of Weathering (CIW) suggest intermediate to extreme weathering conditions
in the source area or during transportation. The studied sandstones are
inferred as highly mature sediments evidenced from their high SiO2/Al2O3 >
1 and the presence of the ultra-stable clay minerals, smectite, kaolinite,
chlorite and illite. Also the Th/U < 3 ratio suggests high uranium enrichment
of Tarat sandstones over crust average composition. From the factor
analysis of the analyzed sandstone, there is no direct relationship between
organic carbon and uranium, indicating the absence of organo-uraniferous
composite and a major source derived from felsic to the mafic rock of Air
Massif. The mineralized fluids of circulating from west to east are usually
capped and underlain by impermeable mudstone or clay-rich units and
uranium mineralization occurs in the association U-Mo-Pb or U-Zn-Ni-Pb
structurally controlled by the major fault in Azaoua lineament fault NS of
Arlit in the West, the N70° Tin Adrar “faisceau” in the North, the N30°
Mouron accident in the Southeast, N30 Autriche accident in the West and
precipitated in areas of suitable reducing environment of arid to humid
climatic conditions rich in organic matter affected by passive margin (PM)
tectonic setting. The negative correlation of U-Th and U-Na in our samples
indicates intense remobilization of uranium in Tarat formation.
Share and Cite:
Bohari, A. , Harouna, M. and Mosaad, A. (2018) Geochemistry of Sandstone Type Uranium Deposit in Tarat Formation from Tim-Mersoi Basin in Northern Niger (West Africa): Implication on Provenance, Paleo-Redox and Tectonic Setting.
Journal of Geoscience and Environment Protection,
6, 185-225. doi:
10.4236/gep.2018.68014.