Evolutionary trend of the Jarawa younger granites ring complex, Jos plateau, central Nigeria

Abstract

The Jarawa Younger Granites Ring Complex which occupies the eastern flank of the popular Jos-Bukuru Ring Complex in Central Nigeria was geologically and geochemically investigated in order to identify the different lithologic units that make up the formation, as well as understand its geochemistry. These were used to unravel its mode of emplacement. Geological field studies revealed that the Jarawa Younger Granites evolved from two major phases of intrusions, the Hornblende Porphyry phase that was accompanied by the Hornblende Biotite Granites and the coarse grained Biotite Granite phase associated with the Biotite Microgranites. Results from geochemical studies supports the above findings, indicating high CaO and MgO content that decreases from the Hornblende Porphyry through the Hornblende Biotites to the coarsed grained Biotite Granites and the Microgranites respectively. Also, all the lithologic units exhibited high alkali content (Na2O + K2O) suggesting secondary magma source for the Jarawa Younger Granites Ring Complex.

Key words: Geology, Lithology, Granites, Akali, geochemistry, Grain sizes