Author(s)

Koffi Germain Tchokpon^1*, Christophe Kaki², Glodji Luc Adissin², Soulémana Yessoufou², Mory Kourouma³

¹Graduate School of Life and Earth Sciences, Faculty of Sciences and Technology (FAST), University of Abomey-Calavi (UAC), Abomey-Calavi, Benin.
²Department of Earth Sciences, Faculty of Sciences and Technology (FAST), University of Abomey-Calavi (UAC), Abomey-Calavi, Benin.
³HSSE Department, Higher Institute of Mines and Geology of Boke (ISMG), Boke, Guinea.

The Alahina sector is located in the North-East of Guinea, precisely in the Siguiri volcano-sedimentary basin. It consists mainly of meta-sediments traversed by Paleoproterozoic pyroclastite, granite, monzogranite and granodiorite veins as well as Mesozoic dolerite and gabbros veins. This article presents new data, on the one hand, on the geochemical petrographic features and the origin of the metasediments of this zone, and on the other hand, on the genetic model of the gold mineralization that they contain. Field observations, as well as petrographic and geochemical studies reveal that the meta-sediments consist of sericite and chlorite schists. They belong to the groups of shales and grauwackes. Their protholites are moderately altered (60 < CIA < 80) andesitic, basaltic and granodioritic rocks emplaced in a geotectonic oceanic island arc and/or active continental margin. Their chondrite normalized REE patterns show a moderate LREE enrichment (La_N/Yb_N = 6.31 - 13.24) and a flat heavy rare earth patterns (HREE). This spectrum is almost identical to those of the “Post-Archean average Australian Shale” and Early Proterozoic Greywackes. Two types of polyphase gold mineralization occur in the Alahina sector: disseminated and veined. They consist of particular of grains and nanoparticles pyrite associated with gold, magnetite, hematite, ilmenite. The hydrothermal alteration accompanying this mineralization consists of silica, microcline, chlorite-epidote-sericite-carbonates.

Metasediment, Schist, Sericite, Chlorite, Vein, Quartz, Gold, Alahina, Siguiri Basin

Tchokpon, K. , Kaki, C. , Adissin, G. , Yessoufou, S. and Kourouma, M. (2019) Metasediments in the Alahina Sector and Associated Mineralization (North-Eastern Guinea). Open Journal of Geology, 9, 897-918. doi: 10.4236/ojg.2019.912097.