IOSR Journal of Applied Geology and Geophysics (IOSR-JAGG) e-ISSN: 2321–0990, p-ISSN: 2321–0982.Volume 9, Issue 5 Ser. I (Sep. – Oct. 2021), PP 01-12 www.iosrjournals.org DOI: 10.9790/0990-0905010112 www.iosrjournals.org 1 | Page Geology, Petrography and Geochemistry of Diatexites around Firo, Northeastern Nigeria Obodumu A. Lucy 1 , A. I. Haruna 1 , A.S. Maigari 1 , Isah Bunyaminu 2 1 Applied Geology Department, Abubakar Tafawa Balewa University, Bauchi, Nigeria 2 Department of Geology, University of Jos, Jos Abstract: The Study area is located in Firo, in Ganjuwa Local Government Area of Bauchi State. Bounded by latitude N10 0 25’00’’ and N10 0 28’.00’’ and longitude E9 0 51’.00’’ and E9 0 55’ 00’’, it forms part of Bauchi sheet 149NE. The study addressed the geology and geochemistry of the study area. The geological mapping indicated three (3) morphological units of migmatite;Metatexite, diatexite and Leucosome band. Petrographic studies showed the presence of the various rock forming minerals which include - plagioclase, quartz, biotite, microcline and orthopyroxene as observed within the field of view under plane and crossed polarized light. Variation diagrams show negative correlation between MgO, CaO, TiO 2 , FeO t and SiO 2 but positive correlation with Na 2 O, K 2 O indicating the normal magma crystallization trends. Careful correlation of the geochemical dataand their field occurrence reflects that the leucosome band has highest amount of added fluid. The geochemical variations observed for the migmatites they were formed within the syn-collisional/Volcanic arc granite tectonic setting with fractional crystallization as the dominant process in their petrogenetic evolution. Key Word: Metatexite, Diatexite, Leucosome band, Microcline,Firo, --------------------------------------------------------------------------------------------------------------------------------------- Date of Submission: 03-09-2021 Date of Acceptance: 16-09-2021 --------------------------------------------------------------------------------------------------------------------------------------- I. Introduction The study area is located in the north-eastern part of Bauchi sheet 149NE and lies between latitudes N10 0 25’00’’ to N10 0 28’.00’’ and longitude E9 0 51’.00’’ to E9 0 55’ 00’’. It covers an area of about 36.75 square kilometers on a scale of 1:25,000 and rise to the height of approximately 556m above mean sea level in some areas, it also hosts a large body of water called ―Gubi /Firo Dam‖ which flows in an E-W direction(Fig. 1 and Fig.2). Geographically, the area is located along the Bauchi – Firo road around in Ganjuwa local Government area of Bauchi State. However, it is mainly accessible through the Bauchi – Firo road and some un-tarred roads with other major and minor footpaths linking hamlet to hamlet and farm lands within the area. This study is aimed at understanding the field relationship, petrography and geochemical signatures of the rock units in the study area with a view tounravel the process by which they were formed. Figure 1. Location of the Study Area (Global mapper).