TITLE:
Petro-Structural Study of the Paleoproterozoic Formations of the Faboula Gold Deposit (Bougouni-Kékoro Basin, Leo-Man Shield)
AUTHORS:
Ousmane Wane, Amadou Baby Ouologuem, Ismaïla N’diaye, Ousmane Dao, Mamadou Yossi
KEYWORDS:
Faboula, Gold, Deposit, Metavolcano-Sedimentary Rocks, Deformation, Paleoproterozoic, Transpression, Drill Cores, Southern Mali, Leo-Man Shield
JOURNAL NAME:
Open Journal of Geology,
Vol.11 No.4,
April
26,
2021
ABSTRACT: Recent
petro-structural investigations on the Faboula gold deposit located in the
Bougouni-Kékoro basin, in southern Mali, north-west of the Leo-Man Shield, have
provided new data on the nature and spatial organization of the
lithostratigraphic units as well as their deformation style. The deposit is covered
by a thick lateritic layer and is hosted by a metavolcano-sedimentary sequence
of Paleoproterozoic age intersected by intrusive bodies and filled fractures of
various shapes and types.
The lithostratigraphic units consist of metagreywackes, metasiltstones,
meta-argillites, slates and schists. Metagreywackes and metasiltstones are
generally feldspathic, both may contain biotite and locally amphibole, just as
slates may contain andalusite which is locally stretched. Plutonic units most
often occur as stocks or as dikes on the drill core, up to 1 m. The
metavolcano-sedimentary rocks are schistose and deformed under greenschist
facies conditions, and locally
they reach the epidote-amphibolite facies. The structural study revealed that
the deposit is affected by several stages of deformation evolving from a
ductile type to a brittle type via a ductile-brittle type. The dominant ductile
and brittle-ductile deformations show a
combination of isoclinal folding and strike-slip faults. Both the isoclinal folding and the strike-slip
faults whose sigmoidal en-echelon tension gashes indicate a dextral movement
in the NNE-SSW direction are the result of the same ENE-WSW regional
shortening. Consequently, they highlight a transpressive deformation. This
deformation noted here D2Fb, could be equivalent to the regional D2 or D3 deformations identified at the scale of the Leo-Man Shield if
we refer to the style of deformation. There is an abundance of quartz veins
networks. Their relation within the structural features indicates that the
mineralization is structurally controlled during a hydrothermal event linked
certainly to the circulations of fluids during the transpressive event D2Fb.