TITLE:
Petrographic and Geochemical Characterization of Metaluminous to Peraluminous Granitoids from Goueygoudoum-Fianga (Southwestern Chad): Insights into Magma Sources and Tectonic Setting
AUTHORS:
Mbaguedje Diondoh, Félix Nenadji Djerossem, Gustave Ronang Baïssemia, Moussa Ngarena Klamadji
KEYWORDS:
Goueygoudoum-Fianga, Mayo Kebbi Massif, I-A-Type Granitoids, Partial Melting, Fractional Crystallization
JOURNAL NAME:
Open Journal of Geology,
Vol.15 No.11,
November
28,
2025
ABSTRACT: The Goueygoudoum-Fianga localities, situated within the Central African Orogenic Belt to the east of the Mayo Kebbi massif (Chad), are dominated by various granitoid types: granodiorite, biotite granite (either deformed or undeformed), and microgranite. These intrusive rocks were emplaced within a greenstone belt and are geochemically divided into two major peraluminous series. The first series, classified as I-type, exhibits a weakly potassic calc-alkaline affinity with a ferro-magnesian composition. It is characterized by low concentrations of V, Cr, Co, Ni, Mg#, Nb/U, and Ce/Pb, along with high levels of alkalis and light rare earth elements (LREE), and positive Eu anomalies. These features suggest an origin related to partial melting of the continental crust, typical of volcanic arc settings. However, elevated Br and Sr contents, combined with low ratios (Rb/Sr, La/Sm, and (Ta/La)N, high Rb/Th values, and negative anomalies in Nb, Ta and Ti, point to the influence of a metasomatized mantle. The second series, identified as A-type, is distinguished by high concentrations of SiO2, K2O, FeO, and incompatible elements, as well as negative anomalies in Sr, Eu, and Ti. This series is derived from partial melting of metagreywackes, métapelites and metabasic to tonalitic in an intraplate tectonic setting. Its geochemical signature also reflects mantle influence associated with a subduction-related environment. The evolution of these granitoids is predominantly by the fractional crystallization processes, with possible crustal contamination during emplacement.