Abstract

Mineralization at the Nassara and Torkera gold deposits is situated at the contact between volcanic rocks (basalt-andesite) and volcanosedimentary rocks (pyroclastite, black shale) within the echelon faults of the large West Batié shear zone (WBZ). Along the mineralized body, shear deformation is intense, accompanied by significant hydrothermal fluid circulation. The objective of this study is to determine the direction of hydrothermal fluid creep in the Nassara-Torkera shear zone. To achieve this, we have integrated direct field measurements with Anisotropy of Magnetic Susceptibility (AMS) measurements and microstructure analysis. Magnetic foliation data align with direct field measurements. Additionally, the lineation data indicate that, during the deformation phase, the material or mineralizing fluids exhibit a southeastward creep, following the contemporaneous structures of deformation. These structures are observed to govern the gold mineralization. Furthermore, the gold content increases in the vicinity of lamprophyre, dacite, and diorite dykes. This observation suggests that the mineralizing fluid and the dykes were emplaced along the same structures of deformation. The drainage of the mineralizing fluid to the southeast explains the occurrence of the seven gold deposits (Djikando, Poni, Nassara, Torkera, Wadaradoo, Konkera and Napelepera) identified along the shear corridor. Identifying the direction of material creep in shear zones serves as a potent prospecting guide for mining explorers, enabling them to strategically position various drill holes efficiently.

Key words: Nassara-Torkera, gold deposit, material creep direction, Anisotropy of Magnetic Susceptibility (AMS), dykes.