Interest in the Côte d’Ivoire sedimentary basin has led to numerous investigations. All these investigations are aimed at understanding the functioning of the basin and a paleogeographic approach including sedim...Interest in the Côte d’Ivoire sedimentary basin has led to numerous investigations. All these investigations are aimed at understanding the functioning of the basin and a paleogeographic approach including sediment transport dynamics. However, the use of exoscopy and semi-quantitative mineralogy has been little developed. This study was carried out to compensate for this lack of interest in these methods. Its aim is to understand the transformation of quartz into hematite using exoscopy and semi-quantitative mineralogy in the Adiaké locality, in the eastern onshore basin of Côte d’Ivoire. Two methods were applied to 250 μm-diameter quartz grains from the 40 m coasts. Exoscopy provides information on microscopic texture, surface and corrosion, as well as determining the transport mechanism and deposition phases of quartz grains. Semi-quantitative mineralogy provides an estimate of the weight percentages of major element oxides and the ultrastructure of quartz grains. Exoscopy showed that these grains had been subjected to torrential fluvial transport. They were marked by mechanical and chemical traces during this transport and evolved in different environments. Semi-quantitative mineralogy shows the existence of negative and positive correlations between oxides. Negative correlations indicate a substitution, in order of importance, of silicon by iron, phosphorus and aluminum in these quartz. Positive correlations show that there is no substitution between the oxides concerned in these quartz grains. Divo’s quartz grains have recorded several mechanical and chemical microstructures of their sedimentary episodes, with the appearance of iron nodules in the ports left by silica.展开更多
文摘Interest in the Côte d’Ivoire sedimentary basin has led to numerous investigations. All these investigations are aimed at understanding the functioning of the basin and a paleogeographic approach including sediment transport dynamics. However, the use of exoscopy and semi-quantitative mineralogy has been little developed. This study was carried out to compensate for this lack of interest in these methods. Its aim is to understand the transformation of quartz into hematite using exoscopy and semi-quantitative mineralogy in the Adiaké locality, in the eastern onshore basin of Côte d’Ivoire. Two methods were applied to 250 μm-diameter quartz grains from the 40 m coasts. Exoscopy provides information on microscopic texture, surface and corrosion, as well as determining the transport mechanism and deposition phases of quartz grains. Semi-quantitative mineralogy provides an estimate of the weight percentages of major element oxides and the ultrastructure of quartz grains. Exoscopy showed that these grains had been subjected to torrential fluvial transport. They were marked by mechanical and chemical traces during this transport and evolved in different environments. Semi-quantitative mineralogy shows the existence of negative and positive correlations between oxides. Negative correlations indicate a substitution, in order of importance, of silicon by iron, phosphorus and aluminum in these quartz. Positive correlations show that there is no substitution between the oxides concerned in these quartz grains. Divo’s quartz grains have recorded several mechanical and chemical microstructures of their sedimentary episodes, with the appearance of iron nodules in the ports left by silica.
