Abstract
The Tikar plain is located on the Cameroon Central Shear Zone. It is also part of the North Equatorial Pan-African Belt. It is formed of granitoids intruded in places by mafic and intermediate dykes. The mafic dykes are essentially banded gabbros composed of plagioclases, pyroxenes, amphiboles, biotites and opaques. Their textures range from porphyroblastic to porphyritic. The intermediate dykes are monzonites and monzodiorites and are characterized, respectively, by cataclastic and mylonitic textures. The minerals identified are amphiboles, potassium feldspar, pyroxenes, epidotes, sphenes and opaques. Seritization reaction is mostly present on the mafic and intermediate dykes, while chloritization is much more pronounced on the intermediate dykes. The Tikar plain dykes are high-k calc-alkaline to shoshonitic. They are characterized by low to moderate SiO2 content (42.08–61.96 wt%), low to high TiO2 (0.47–2 wt%) and low Ni (1.48–99.18 ppm) contents. The mafic dykes show fractional trends with negative anomalies of Zr, U and P and positive Rb, Ba, Ta, Pb and Sr in multi-element diagrams, while the intermediate dykes present negative anomalies of Nb, Ta, Zr, Sr P and Ti and relative positive anomalies of Rb, Ba and Pb. The rare-earth elements (REE) patterns show positive Eu anomalies for the mafic dykes and negative anomalies for the intermediate dykes. The REE spectrum of all the dykes shows enrichment in LREE with relatively flat HREE, which can indicate arc magmatism. In the Zr–Ti/100–Sr/2 diagram, the mafic dykes plot in the island arc tholeiite and calc-alkaline basalt fields. The Th, Nb and LREE concentrations indicate that the subducted lithosphere with crustal component contributed to generation of the intermediate dykes of the Tikar plain. The geochemical characteristics of the mafic to intermediate dykes suggest their derivation from a various degree of partial melting in the garnet spinel facies, probably between depths of 80 and 100 km. The collision between the Central African Fold Belt and the northern edge of the Congo craton resulting in crustal thickening, sub-crustal lithospheric delamination and upwelling of the asthenosphere may have been the principal process in the generation of the intermediate dykes in the Tikar plain. The magma for the mafic and intermediate dyke would have migrated through the faults network of the Central Cameroon Shear Zone before crystallizing in the granito-gneissic basement rocks.
Highlights
Precambrian rocks in Cameroon are divided into two lithotectonic groups, namely the Ntem group and the Pan-African North Equatorial Folded Belt (PANEFB) [1,2,3]
Owing the fact that the mafic to intermediate dykes are of great interest for the understanding of the tectonic evolution of a given area, we present in this article, the field, petrographic and whole rock geochemical data of mafic to intermediate dykes of the Tikar plain and discuss the petrogenesis, magmatic evolution, mantle source as well as the tectonic settings of the dykes in order to deduce the tectonic evolution of the Tikar plain in particular and PANEFB in Cameroon in general
Banded-gabbros outcrops are exposed in the form of dykes or slabs
Summary
Precambrian rocks in Cameroon are divided into two lithotectonic groups, namely the Ntem group and the Pan-African North Equatorial Folded Belt (PANEFB) [1,2,3]. PANEFB evolutionary geotectonic models in Cameroon show an early extension that led to the formation of Early Neoproterozoic sedimentary basins followed by subduction and collision between the Saharan metacraton and the Congo craton at 0.6 Ga [8]. In Cameroon, this extensive tectonic regime led to the formation of intracratonic basins or graben covered with Cretaceous sedimentary deposits, accompanied by Mesozoic to Lower Cenozoic magmatism that favored the formation of granitic or gabbroic plutons and some dykes swams and volcanic deposits [9]. Owing the fact that the mafic to intermediate dykes are of great interest for the understanding of the tectonic evolution of a given area, we present in this article, the field, petrographic and whole rock geochemical data of mafic to intermediate dykes of the Tikar plain and discuss the petrogenesis, magmatic evolution, mantle source as well as the tectonic settings of the dykes in order to deduce the tectonic evolution of the Tikar plain in particular and PANEFB in Cameroon in general
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.