Transpressional granite-emplacement model: Structural and magnetic study of the Pan-African Bandja granitic pluton (West Cameroon)

• Published in: Journal of Earth System Science Vol. 125; no. 1; pp. 179 - 202
• Main Authors: Sandjo, A F Yakeu, Njanko, T, Njonfang, E, Errami, E, Rochette, P, Fozing, E
• Format: Journal Article
• Language: English
• Published: New Delhi Springer India 01.02.2016; Springer Nature B.V; Indian Academy of Sciences
• Subjects: Belts; Deformation; Earth and Environmental Science; Earth Sciences; Feldspars; Ferromagnetism; Gneiss; Granite; Igneous rocks; Magma; Magnetic fields; Magnetic studies; Magnetite; Metamorphism; Minerals; Plutons; Rocks; Sciences of the Universe; Space Exploration and Astronautics; Space Sciences (including Extraterrestrial Physics; Cameroon; Cameroon; Bandja; AMS; Pan-African; Granite
• ISSN: 0253-4126; 0973-774X; 0253-2143
• DOI: 10.1007/s12040-015-0654-x

The Pan-African NE–SW elongated Bandja granitic pluton, located at the western part of the Pan-African belt in Cameroon, is a K-feldspar megacryst granite. It is emplaced in banded gneiss and its NW border underwent mylonitization. The magmatic foliation shows NE–SW and NNE–SSW strike directions with moderate to strong dip respectively in its northern and central parts. This mostly, ferromagnetic granite displays magnetic fabrics carried by magnetite and characterized by (i) magnetic foliation with best poles at 295/34, 283/33 and 35/59 respectively in its northern, central and southern parts and (ii) a subhorizontal magnetic lineation with best line at 37/8, 191/9 and 267/22 respectively in the northern, central and southern parts. Magnetic lineation shows an ‘S’ shape trend that allows to (1) consider the complete emplacement and deformation of the pluton during the Pan-African D 2 and D 3 events which occurred in the Pan-African belt in Cameroon and (2) reorganize Pan-African ages from Nguiessi Tchakam et al . ( 1997 ) compared with those of the other granitic plutons in the belt as: 686 ±17 Ma (Rb/Sr) for D 1 age of metamorphism recorded in gneiss; and the period between 604–557 Ma for D 2 –D 3 emplacement and deformation age of the granitic pluton in a dextral ENE–WSW shear movement.