Related Structures Linked to the Emplacement of the Dianfla Granodiorite Pluton (Central Cote dIvoire): Contribution to the Understanding of Gold Mineralization in the Birimian Area of West Africa - TI Journals

Abstract: The Dianfla granodiorite is intrusive in metasediments and metamorphosed volcano-sediments in the gold prospect of Bouafle-Centre (Cote d\Ivoire). Using field data, thin sections, satellite imagery and oriented drill cores data permit to determine the lithology of the different formations and geological structures that affect them. It also helped provide some answers as the emplacement of the pluton, its contribution to the structuration and the origin of the gold mineralization. The Dianfla pluton is an undeformed granodiorite with two facies (fine-grained leucocratic and a medium-grained mesocratic facies). However, on its eastern border, in contact with its host rocks (chlorite schists, sericite schists, graphitic schists, sandstones and greywackes), the pluton is highly distorted, with the appearance of a mylonitic facies. Geological structures are cleavages and schistosity with average direction N35° to N40°W, faults and fractures of varying directions (N-S, NE-SW, E-W and NW-SE), lithological contacts for most NNE-SSW to N-S, quartz veins and tension gashes filled with quartz and sulphides with N120° to N140°, E-W and NE-SW directions. The model of mineralization that we propose is the following: Before the emplacement of the Dianfla pluton, sinistral submeridional shear zones (Danangoro fault in the west and Okabo faults in the East) are crosscuted by sinistral N50° to N60° faults. These allow openings for the rising of the magma. The emplacement in the form of forced intrusion (diapiric pluton) causes several stresses on its borders. This creates a mylonitic shear zone in the contact with the host rocks. The hydrothermal fluids were injected into the cleavages planes to give a N40° mineralization (M1). The final Eburnean NW-SE shortening causes the opening of N120° to N140° tension gashes. The latter will undergo a strong hydrothermal alteration accompanied by sulphides, what will be a second phase of mineralization (M2).