Petrography and Mineralogy of the Quartz and Quartz-Feldspar Sulphide Veins in the Pan-African Syenitic Massif of Guider (North Cameroon)

Marguerite Boyabe,Rigobert Tchameni,Daouda Dawai,Periclex Martial Fosso Tchunte

doi:10.4236/ojg.2020.103013

Marguerite Boyabe, Rigobert Tchameni + Show 2 more

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https://doi.org/10.4236/ojg.2020.103013

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Abstract

In the syenitic pluton of Guider (593 ± 4 Ma) in the North-West Cameroon domain of Central African Fold Belt, mineralized N-S to NE-SW vertical or sub-vertical quartz and quartz feldspar veins has been recently identified. In this contribution, we present petrography and mineralogy of these veins, in order to constrain their genesis and emplacement mechanisms based on detailed field work, petrographic studies and chemical characterization of minerals by using an electron probe microanalyser (EPMA). Field observations and vein microstructures show that the emplacement of the veins has been controlled by the dextral N-S trending strike-slip shear zones related to the regional D2 deformation phase. The results of mineralogical analysis reveal the co-presence of silicates and metallic minerals that include magnetite, ilmenite, pyrite, bismuthite, galena (very rare) and sulphide complexes (BiPbS, BiAgPbS, FeBiPbCuS, BiFe(TeS), FeBiPbS, BiPbCuS). The gangue is represented by quartz (quartz 1, quartz 2 and quartz 3), feldspars, sericite, chlorite, yellowish brown clay minerals, and hematite. The textural relationships between sulphides, quartz and alteration products show that the mineralization is essentially syn- to late-D2 and suggest that syenitic country rock and dextral shear zones have played an important role in the metallogenesis of these veins. This mineralization shows characteristics for copper-bearing calc-alkaline deposits, but differs from these by its more extensive alteration and its abundance in hematite. Substitutions of Al(IV) by Si(IV) in sericite associated with the sulphide mineralization and cataclastic deformation suggest that the temperature of trapping of the fluids is between 230°C and 275°C.

Highlights

Mineralization associated with more or less differentiated plutonic rocks and that associated with the concentration of hydrothermal fluids are the main primary sources of mineral resources on our planet [1] [2] [3]
We present petrography and mineralogy of these veins, in order to constrain their genesis and emplacement mechanisms based on detailed field work, petrographic studies and chemical characterization of minerals by using an electron probe microanalyser (EPMA)
The textural relationships between sulphides, quartz and alteration products show that the mineralization is essentially syn- to late-D2 and suggest that syenitic country rock and dextral shear zones have played an important role in the metallogenesis of these veins

Summary

Introduction

Mineralization associated with more or less differentiated plutonic rocks and that associated with the concentration of hydrothermal fluids are the main primary sources of mineral resources on our planet [1] [2] [3]. Prospecting missions carried out on the Garoua East geological reconnaissance map in the North Cameroon region by the Bureau de Recherches Géologiques et Minières (BRGM) report gold, cassiterite, copper, galene-blende, rutile, ilmenite and monazite occurrences in sediments of several “mayo” or temporary watercourses [6] [7] [8]. The origin of these metals remains undetermined, especially for those located north of the Benue trough, where no metallogenic studies are carried out, compared to the Poli sector (south of the Benue trough), which has been the subject of several metallogenic studies [9] [10] [11].

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