Some geochemical considerations in the petrogenesis of Madagali granitoids, northeastern Nigeria

Abstract

Major and trace element geochemical data on granitoids of Madagali area of northeastern Nigeria show a series that ranges from K-calc-alkaline, through granodiorite-monzogranite to granite. They are characterized as mildly peraluminous to metaluminous and I-type based on alumina saturation index (ASI). Trace element contents preclude the possibility of entire mantle origin and indicate significant crustal involvement in the evolution of the granitoids. The enrichment in LREE ( La, Ce and, Nd), depletion in HREE (Ho, Er, Yb and Lu) and a pronounced negative Eu anomaly with (La/Yb)N suggest that the granitoids must have evolved by partial fractionation or partial melting of the pre-existing crust in which plagioclase feldspar was retained. Furthermore, the enrichments in some large-ionlithophile elements (LILE) such as Rb, Ba, Th and K and depletion in some high field strength (HFS) elements such as
Nb, P, and Ti as well as some transitional elements Cr and Ni are supportive of crustal involvement in their genesis