TITLE:
Lithostructural and Geochemical Characterization of the Metavolcanic and Granitoid Formations of the Birimian Belt of East Boromo (Burkina Faso): Their Relationship with the Lawra Belt (Ghana)
AUTHORS:
Souleymane Sampegbo, Saga Sawadogo, Abraham Seydoux Traore, Séta Naba
KEYWORDS:
Granitoid, Birimian Belt, Burkina Faso, Lawra Belt
JOURNAL NAME:
International Journal of Geosciences,
Vol.17 No.10,
October
14,
2026
ABSTRACT: The Boromo-East belt, located south of the Man ridge, runs generally NE-SW to N-S and consists of a belt of green rocks (volcanic and volcano-sedimentary) and various types of granitoids. Petrographic observations have shown that the volcanics generally contain large crystals of plagioclase and amphibole, newly formed in places, with garnet present exclusively within the metabasalt. The diverse nature of the granitoids reflects the fact that different subduction phenomena have produced several types of magma, which in turn have generated diverse rock formations. Deformation within the Boromo-East belt is generally ductile-brittle to brittle, evidence that the structural level was much higher at the time of deformation. Interpretation of the shear zones in the Boromo-East belt has revealed a major shear zone called the AMDSZ (Amélé-Dibon Shear Zone), which is the continuation of the Jirapa shear zone (Jirapa shz) recognized within the Lawra belt. Geochemical data reveal negative anomalies in Nb, Ta, and Ti within the volcanic and granitoid formations of the Boromo-East and Lawra belts. However, the Boromo-East belt shows variability in the coexistence of IAT + CAB magmas, while the Lawra belt shows a more tholeiitic composition. The different collision implications affecting the more calc-alkaline and less tholeiitic Lawra belts suggest that the collision and the location of the shears led to a modification of magmatic differentiation on either side of the orogenic suture. In the Boromo-East belt, it appears that the collision with the Lawra belt could be interpreted as the result of late convergence between two crustal blocks of volcanic arcs of different ages and histories. However, the Boromo-East belt shows variability in the coexistence of IAT + CAB magmas, while the Lawra belt shows a more tholeiitic composition. The different collision implications affecting the more calc-alkaline and less tholeiitic Lawra belts suggest that the collision and the location of the shears led to a modification of magmatic differentiation on either side of the orogenic suture. In the Boromo-East belt, it appears that the collision with the Lawra belt could be interpreted as the result of late convergence between two crustal blocks of volcanic arcs of different ages and histories.