Geological Settings and Geochemistry of Younger Granitic Rocks from Kuba Area, Ropp Complex, North-Central Nigeria

Abstract

Kuba area is located in the Ropp complex of Younger Granite Province in northcentral Nigeria. Granitic rocks samples were studied geologically and geochemically using ICP-MS analysis for major oxides, trace and rare earth elements. The present study focuses on the determination of geological settings and geochemistry of granitic rocks in Kuba area. In the SiO2 versus total alkali diagram (TAS) of granitic rocks for Kuba area, the granitic rocks predominantly plot in the alkaline field. Based on the A/CNK ratio (Al2O3/CaO+Na2O+K2O) which is >1, the younger granitic rocks are peraluminous in composition. The granitic rocks from Kuba area can be classified as A-type based on the classification of granites because of their alkalinity, anhydrous characteristic and presumed anorogenic tectonic settings. The normalized ratios of LaN/YbN for granite porphyry ranges from 27.11 to 28.33 and biotite granite ranges from 8.69 to 9.01. The normalized ratio of CeN/YbN for granite porphyry varies from 19.63 to 20.85 and biotite granite varies from 4.85 to 5.48. The normalized ratio LaN/SmN for granite porphyry ranges from 5.86 to 6.12 and biotite granite ranges from 2.88 to 2.91. The high values of the normalized ratios of La to Yb, Ce to Yb and La to Sm are evidence of high degree of fractionation, which show that the REE patterns are LREE enriched with the higher values recorded in the more fractionated granite porphyry than the biotite granite. The negative Eu anomalies in the granitic rocks show that high amount of plagioclase was removed from the felsic magma during fractional crystallization