TITLE:
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
AUTHORS:
Abdou Dodo Bohari, Moussa Harouna, Ali Mosaad
KEYWORDS:
Uranium, Genesis, Geochemistry, Tarat Formation, Tim-Mersoi Basin
JOURNAL NAME:
Journal of Geoscience and Environment Protection,
Vol.6 No.8,
August
30,
2018
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