TITLE:
Geological, Mineralogical and Geochemical Studies of Pyrite Deposits in the Eastern Part of Douala Sub-Basin (Cameroon, Central Africa)
AUTHORS:
Gilbert François Ngon Ngon, Pierre Stève Abomo, Michel Bertrand Mbog, André Mbabi Bitchong, Joël Simon Mbaï, Thérèse Valérie Ngonlep Minyemeck, Rose Yongue Fouateu
KEYWORDS:
Douala Sub-Basin, Geochemical, Geological, Mineralogical, Pyrite Deposits
JOURNAL NAME:
International Journal of Geosciences,
Vol.6 No.8,
August
28,
2015
ABSTRACT: Pyrite deposit of pK27,
Douala sub-basin (Cameroon, Central Africa) was studied in a tropical forest
setting physically and using X-ray diffraction and X-ray fluorescence
spectrometry (XRF) in order to characterize the mineralization for his
industrial utilization. The sedimentary materials from the pyrite deposit were
grouped into five (05) main lithofacies, including four claystone facies and
one conglomeratic facies. The mineralization occurs along the low slopes of
valleys inlight grey claystone
facies situated on the bottom of outcrops with 80 to 200 cm thickness. Theparticle size distribution of clayey
materials host rocks shows that they are essentially constituted of clay and
silts fractions. However, their Sorting index (So) more than 4.5 corresponds to
poorly sorted sediments and the torrential type; whereas their Coefficient of
asymmetry (A) more than 1indicates
that the sorting is carried out towards fine particles. Macroscopically, pyrite
in thesematerials is in crumbly
and consolidated piles with aggregate pyrites in oolithic concretions, andglobular, cubic, octaedric, massive
and fossiliferous forms. The mineralogical compositions ofthese clayey materials indicate that
they are essentially kaolinitic and illitic, followed by goethite, quartz,
pyrite, halloysite, anatase and rutile with hematite as accessory minerals.
Pyrite in sand fractions is associated with kyanite, grenat, rutile, diopside,
muscovite and tourmaline the minerals whichrecognize
the regional metamorphism. However, the specific chemical signature of SO3contenthigh in clayey materials and abundant (50.86%
- 57.64% SO3) in pyrite is characteristic of the pK27 pyritic
formations in the eastern part of Douala sub-basin. Moreover, the Co:Ni ratios
of pyrites approximately 0.25 to 0.8 are characteristic of sedimentary pyrites
and also suggest an anoxic environment.