The Boni Shear Zone (BoSZ) has garnered significant interest from the geological exploration community following the Siou gold deposit discovery in the Mana gold district, southwestern Burkina Faso. The BoSZ represents a sheared contact separating the “Tarkwaian-type” metasedimentary sequences and the “Birimian-type” metavolcanic and metavolcano-sedimentary assemblages of the Houndé belt. The primary objective of this work is to elucidate the structural setting of the BoSZ and its control on gold mineralization. To achieve this, field work data, airborne geophysical data and satellite images have been interpreted and integrated. The initial deformation phase (D1) occurred as an E-W directed regional shortening. Subsequent phase (D2) developed transpressional dynamics under a NNW-SSE shortening, which is mainly documented within shear-zone-hosted coarse-clastic metasedimentary rocks. The last and minor phase (D3) developed a minor crenulation cleavage. Several sets of shear zones formed during D2: the older set is the NE-trending dextral strike-slip Bagassi shear zones (BaSZ). The main set, of regional extent, corresponds to the N-S trending sinistral transpressive Boni shear zones (BoSZ). It includes an anastomosing network of mylonite alternating with undeformed macro/microlithons. The last set, possible conjugate with the BoSZ, is localized nearby the Bagassi pluton and consists of the brittle-ductile NW-trending sinistral Yaramoko shear zones (YaSZ). All sets hosts gold mineralization.

Boni shear zone - Yaramoko shear zone - Bagassi gold district - Birimian - Tarkwaian