Geochemical and Isotope Sr-Nd Character of Dschang Biotite Granite: Implications for the Pan-African Continental Crust Evolution in West-Cameroon (Central Africa)

Abstract

The biotite granite of Dschang composing of quartz, feldspar and biotite, is a haplogranite I-type calc-alkalinegranitoid. It is weakly peraluminous with a ferroan affinity and exhibits fractionated feature. This granite wasgenerated at the minimum temperature and pressure of crystallization of 650°C/4 Kb. Its emplacement issyn-central Cameroon shear zone like most of post-collisional granitoids of the Pan-African fold belt in centralAfrica, and it displays N-S to NNE-SSW magmatic foliation dipping 30° to 60° towards W or WNW. Theevolution of the major elements shows a generalized decrease correlation trends look firstly like fractionalcrystallization. The depleted Sr content related to decreasing Al2O3 and CaO concentrations, indicate the roleplayed by plagioclase during differentiation. The trace elements normalized to the primitive mantle, shownegative anomalies out of Nb, Ta, Sr and Ti, and positive anomalies out of Ba, Rb, Th, comparable with those ofthe continental crust. The isotopic data Sr-Nd are rather homogeneous suggesting a single source for the biotitegranite of Dschang. ?Nd600Ma (- 16 to -18) and TDM (1.9 to 2.1 Ga) confirm the formation of the magma of thebiotite granite of Dschang starting from an old Paleoproterozoic crust by partial melting around 600 Ma. Thismelting which seems to have spread in the area and at several levels of the continental lithosphere, hencemagmas were mixing throughout their evolution, considering the diversity of the granites and their sources, iscertainly caused by great movements along CCSZ, at the post-collisional period of Pan-African orogenesis incentral Africa.