Origin and intraplate tectonic setting of mafic magmatic enclaves from the Ngaoundal area, Adamawa-Cameroon: Insights from petrography and geochemistry

Abstract

In this contribution, detailed field descriptions together with petrographic and bulk-rock major, trace and rare earth elements (REE) data are used to constrain the origin and geodynamic setting of the mafic magmatic enclaves (MMEs) recently discovered within the Pan-African Ngaoundal pluton, Adamawa area, central Cameroon. The investigated MMEs are dark-colored with chilled margins, and display medium to coarse-grain igneous textures. The mineral assemblage is either dominated by K-feldspar and carbonate (group I), or by amphibole and plagioclase (group II), though the overall mineral phases made of amphibole, plagioclase, K-feldspar, and biotite are similar to that of their host syenite but in different proportions. The MMEs in Ngaoundal area are foid-gabbro in composition with SiO2 contents ranging between 41.52% and 43.74% and are contiguous with their host granitoids of intermediate composition (SiO2=57.52% to 58.98%). The host granitoid rocks are metaluminous, and belong to the shoshonitic series. Petrographic and geochemical data have revealed that the Ngaoundal MMEs derived from rapid cooling of hot injected lithospheric mantle-derived magma within cooler host granitoids magma and were emplaced in the intraplate geodynamic setting.©2022 China Geology Editorial Office.