5:15 PM - 6:45 PM
[SMP22-P05] Fluid inclusion studies in auriferous quartz veins from Kwaka, Niger state, Nigeria
Occurrence of gold-bearing quartz veins have been reported in several regions of Niger State, Nigeria. In this study we have conducted a detailed fluid inclusion study of mineralized quartz veins in Kwaka region of Niger state. Geology of Nigeria is dominated by crystalline and sedimentary rocks both occurring approximately in equal proportions. The Nigerian basement, which lies within the Pan-African mobile belt to the east of the West African Craton, can be divided into two provinces; (1) The Western Province, approximately west of latitude 8°E, is characterized by narrow, sediment-dominated, N-S trending, low-grade schist belts in a predominantly migmatite- gneiss older basement, and the whole region is intruded by Pan-African granitic plutons, and 2) The Eastern Province comprises mainly a migmatite-gneiss complex intruded by larger volumes of Pan-African granites and the Mesozoic ring complexes of Central Nigeria. Geochronological work has demonstrated that the Nigerian basement includes rocks of Liberian (Archean), Eburnean (early Proterozoic), middle Proterozoic and Pan-African (late Proterozoic) ages. The Pan-African Belt in Nigeria forms part of the Benin-Nigeria (Dahomeyan) shield which is regarded as the southern prolongation of the circumcratonic Pan-African belt of the West African Craton.
Kwaka area of Niger State in North Central Nigeria falls within the Pan-African tectothermal event which occurred in Nigeria similar to other parts of West Africa with widespread effect on the mineralization of rejuvenated basement. The study area forms part of the Zungeru - Birnin Gwari schist belt, which is one of the 11 Precambrian to early Proterozoic schist belts in Nigeria. Structurally controlled, gold-bearing quartz veins were investigated. Field and petrographic studies indicate that the major rocks constitute gneisses, granites, amphibolite and migmatites. The associated quartz veins are generally concordant with the main N-S regional structural trend. The lithological and structural studies carried out in these areas have demonstrated that the auriferous quartz veins cut across the regional structures. The main characteristics of the gold mineralization in the area appear to indicate hydrothermal mineralization in connection with shear zones.
Fluid inclusions are abundant in quartz veins. Both primary and secondary inclusion are present, where biphase inclusions are common. The temperature of final melting values obtained so far from fluid inclusion microthermometry indicate various fluid compositions such as CO2, CO2 + H2O rich, with freezing point depression indicating the presence of salt (NaCl or HCl). Homogenization temperatures of inclusions indicate high temperature of crystallization of quartz. Further laboratory analysis of fluid inclusion studies are currently ongoing on the rock samples and quartz veins from Kwaka, with the aim to understand their mineralogy and to use the fluid inclusion data to provide information related to temperature conditions and composition of fluids involved during or after the crystallization processes.
Kwaka area of Niger State in North Central Nigeria falls within the Pan-African tectothermal event which occurred in Nigeria similar to other parts of West Africa with widespread effect on the mineralization of rejuvenated basement. The study area forms part of the Zungeru - Birnin Gwari schist belt, which is one of the 11 Precambrian to early Proterozoic schist belts in Nigeria. Structurally controlled, gold-bearing quartz veins were investigated. Field and petrographic studies indicate that the major rocks constitute gneisses, granites, amphibolite and migmatites. The associated quartz veins are generally concordant with the main N-S regional structural trend. The lithological and structural studies carried out in these areas have demonstrated that the auriferous quartz veins cut across the regional structures. The main characteristics of the gold mineralization in the area appear to indicate hydrothermal mineralization in connection with shear zones.
Fluid inclusions are abundant in quartz veins. Both primary and secondary inclusion are present, where biphase inclusions are common. The temperature of final melting values obtained so far from fluid inclusion microthermometry indicate various fluid compositions such as CO2, CO2 + H2O rich, with freezing point depression indicating the presence of salt (NaCl or HCl). Homogenization temperatures of inclusions indicate high temperature of crystallization of quartz. Further laboratory analysis of fluid inclusion studies are currently ongoing on the rock samples and quartz veins from Kwaka, with the aim to understand their mineralogy and to use the fluid inclusion data to provide information related to temperature conditions and composition of fluids involved during or after the crystallization processes.