Origin and morphodynamic characterization of river sands, southwestern coast Cameroon: evidence from grain size, heavy minerals, and ilmenite chemistry

For the purpose of characterizing the chemical composition indices of ilmenites from the fluvial system in southwestern Cameroon, electron probe microanalysis of mineral chemistry was carried out on ilmenite grains selected from the collected sediment samples. Previously, various particle size parameters (mean size, standard deviation, kurtosis, and skewness) were applied to the sand fraction to describe textural characteristics and heavy minerals. The study reveals sands with a coarse to medium size trend, with a predominance of coarse, poorly to moderately sorted. These traits point to a high - energy setting. The 0.125–0.063 mm grain size fractions of the sands were used for the recovery of heavy minerals. The occurrence of unstable heavy minerals, such as hornblende, zoisite, garnet, and augite, in these sands denote immature sediments. According to a quantitative evaluation, the main accompanying opaque heavy minerals that may contain ilmenite are zircon and zoisite. The major and minor element compositions of ilmenite, TiO 2 (43.75–56.98%; average 48.41%) and FeO (34.31–48.86% (average 43.89%), with MnO (3.06%), V 2 O 5 (2.15%), and Nb 2 O 5 (0.29%) including, indicate composite igneous rock. The Ti/(Ti + Fe) ratio values (0.42 to 0.52) of the samples are characteristic of ferri - ilmenites and hydrated ilmenites which have favorable to the sulfate process for the manufacture of ferrotitanium pigment.