POTASH METASOMATISM ENRICHMENT OF THE NINGI YOUNGER GRANITE COMPLEX BAUCHI, NORTH-EAST NIGERIA. IMPLICATION FOR FLUID CRYSTALLIZATION AT HIGH TEMPERATURE.

The geochemical classification of Ningi younger granite complex indicates that it is composed of suites of granite- monzogranite-syenogranite-rhyolite-rhyodacite. The liquid line of descent in the harkrer variation diagrams, indicate that the magma that crystallized to give the Ningi complex is of mantle origin with one or more levels of contamination. The plot of Fe2O3 and TiO2 against SiO2 gives a trend showing instant initial decrease probably indicating fractional crystallization of earlier formed crystals, like Titano-magnetite at higher temperature. The younger granite complex emplacement was accompanied by alteration and enrichment with some elements of interest. The complex shows potash metasomatism which is not uniform across the complex. It is more prominent towards the north-western part of the complex, around Zidangan Fulani area. The plots of K2O against SiO2, SiO2-Na2O-K2O and Al2O3-CaO-K2O also indicate potash enrichment. This suggests that, the crystallizing fluid towards that area interact with the country rocks at higher temperature. The alteration process came along with the deposition of Pb, Zn and Mn.