Journal of Geosciences and Geomatics, 2020, Vol. 8, No. 2, 94-109 Available online at http://pubs.sciepub.com/jgg/8/2/5 Published by Science and Education Publishing DOI:10.12691/jgg-8-2-5 Geochemistry of the Neoproterozoic Mbondo-Ngazi Tina Metasediments, Adamawa Area, Central Cameroon: Source Provenance and Tectonic Setting Alexis Hamdja Ngoniri 1 , Timoleon Ngnotue 1,* , Evine Laure Tanko Njiosseu 1 , Patrick Ayonta Kenne 1 , Sylvestre Ganno 2,* , Jean Paul Nzenti 2 1 Department of Earth Sciences, University of Dschang, P.O. Box. 67 Dschang, Cameroon 2 Department of Earth Sciences, University of Yaoundé I, P.O. Box 812 Yaounde, Cameroon *Corresponding authors: Received October 09, 2020; Revised November 10, 2020; Accepted November 17, 2020 Abstract The Mbondo-Ngazi Tina area belongs to the Adamawa-Yade domain within the Pan-African Central Africa Fold Belt in Cameroon (CAFB). The basement of this area is dominated by metasedimentary rocks composed of sericite schist, chlorite schist and muscovite schist. Whole-rock geochemical compositions of these rocks were investigated in order to determine their provenance and tectonic setting. The studied metasedimentary rocks have SiO 2 and Al 2 O 3 contents comparable to the average composition of the Neoproterozoic upper continental crust (UCC). These rocks are strongly depleted in CaO, MgO, and enriched in K 2 O, Ba and Rb with respect to UCC, reflecting K addition during diagenesis. The CIA, CIW, PIA and the SiO 2 /Al 2 O 3 and Th/U ratios indicated that these rocks had suffered varying degrees of weathering as the source rocks underwent mild to moderate chemical weathering. The PAAS-normalized REE patterns are almost flat with slightly LREE depletion with respect to HREE and null to weakly positive Eu anomalies. Their chondrite-normalized REE patterns are parallel to sub-parallel, LREE-enriched, and display distinct negative Eu anomalies and weakly fractionated HREE segments. Overall, they are geochemically mature and have suffered sedimentary recycling. They derived mainy from felsic to intermediate rocks with minor contamination of mafic rocks. The Mbondo-Ngazi Tina metasedimentary rocks show REE and trace element compositions similar to those of Archean sediments, suggesting that the continental crust of the study area during the early Proterozoic had chemical compositions similar to those of the Archean crust and were probably deposited in active to passive continental margin settings. Keywords: Metasediments, UCC, chemical weathering, Archean crust, Adamawa-Yade Cite This Article: Alexis Hamdja Ngoniri, Timoleon Ngnotue, Evine Laure Tanko Njiosseu, Patrick Ayonta Kenne, Sylvestre Ganno, and Jean Paul Nzenti, “Geochemistry of the Neoproterozoic Mbondo-Ngazi Tina Metasediments, Adamawa Area, Central Cameroon: Source Provenance and Tectonic Setting.” Journal of Geosciences and Geomatics, vol. 8, no. 2 (2020): 94-109. doi: 10.12691/jgg-8-2-5. 1. Introduction The Neoproterozoic crustal evolution of central Africa is characterized by the Pan-African orogeny [1,2,3,4]. This crustal evolution comprises the development of basins filled by volcano-sedimentary rocks, metamorphic rocks and by granitic intrusions. In Cameroon the Pan-African basement also known as Pan-African North Equatorial Fold Belt (PANEFB, [5,6]) or Central Africa Fold Belt (CAFB, [4]), is subdivided into three geodynamic domains that are disrupted and isolated from each other by transcurrent faults (Figure 1). Of these three domains, the central domain or Adamawa-Yade Domain (AYD) has been widely investigated for the past two decades, but their geodynamic evolution remains controversial and/or unrevealed. Many studies have been mainly concentrated on petrogenesis of granitoids which are widespread in the central domain [7-15] and only few works on the metamorphic rocks [7,16,17,18,19] In comparison to the granitoids, the metamorphic rocks, especially metasedimentary rocks from the central domain have received very little attention even though sedimentary rocks contain a wealth of information about provenance and crustal evolution [20,21]. It is now well established that detrital sediments contains part of a record of geologic history. Petrographic study has traditionally been an important method in extracting this information [22,23], but is not very useful for metamorphosed sediments. Geochemical investigations, particularly rare earth elements (REE) behaviors is a more suitable approach and can be effectively used for all types of clastic sediments, including metasediments, to evaluate the nature, the provenance and depositional setting [20]. In this paper, we examine the geochemistry of the Mbondo-Ngazi-Tina metasedimentary rocks located in the central domain of the Pan-African belt (Figure 1 and