The Eburnean granitoids of the Zam area are located in the Boulsa square degree, in central-eastern Burkina Faso, approximately 80 km south of Ouagadougou.
It is a group of granitic rocks (s.l.), of variable composition, calc-alkaline to alkaline, belonging to the Baoulé-Mossi domain of the West African craton.
The petrography of the rocks that compose it reveals a range of facies. The lithological units observed show: i) a frequent association of gneissified tonalite-granodiorite; ii) biotite granites, sometimes muscovite granites, with passages of circumscribed porphyroid facies; iii) quartz-rich syenite massifs with felsic to neutral porphyritic veins at the western and eastern edges.
Geochemical signatures, like petrographic studies, reveal contrasts in composition. The major elements, based on their silica content, show two groups: neutral rocks, with SiO2 < 65, and acidic rocks with SiO2 > 65. The analysis of rare earths and trace elements is telling. The various diagrams define an orogenic setting with varied sources (crustal, mantle, and mixed).
Geochronological data from previous studies, combined with geochemical and petrographic data, show a sequential emplacement of these granitoids: i) Stage I: emplacement of tonalite-granodiorites; ii) Stage II: emplacement of granitic plutons; iii) Stage III: emplacement of the syenitic massif. (crustal, mantellic, and mixed).