PETROGRAPHIC AND MINERALOGICAL CHARACTERIZATION OF GRANITOIDS AND PEGMATITES IN THE PAN-AFRICAN HARAZE DJOMBO MASSIF (BATHA, CENTRAL CHAD)

Abstract

The Batha Massif, located in central Chad, occupies a key position at the transition between the Saharan Metacraton and the Pan-African Central African Fold Belt. The geodynamic evolution and metallogenic potential of this area remain poorly understood due to the scarcity of modern petrographic and mineralogical data. This study is based on a combined approach involving field surveys in the Djombo and Gleb sectors(Haraze Djombo department), optical microscopy for petrographic characterization, and high-resolution powder X-ray diffraction (XRD) for mineralogical analysis. The observations highlight two main facies: a peraluminous biotite-muscovite granite (Djombo) and a strongly altered amphibole-biotite granite (Gleb). XRD analysis of the Djombo granite reveals an assemblage dominated by quartz,microcline, albite, biotite, and tremolite. The Gleb pegmatite sample displays a monophasic signature of extremely pure and highly crystalline quartz, associated with a cataclastic texture. These data evidence post collisional felsic magmatism emplaced during a period of crustal relaxation (~570-560 Ma). The massive quartz veins reflect an intense circulation of late- to post-orogenic hydrothermal fluids, controlled by shear zones, thereby confirming the strong metallogenic (particularly gold) potential of the area.