Industrial suitability of upper cretaceous limestone in Mbalangi, Ediki, Kendonge and Mungo River, Mungo River Formation, Northwestern Douala basin, Cameroon (West Africa): A geochemical approach

Abstract

The geochemistry of limestone deposits in the Mungo River Formation, Northwestern Douala Basin, Cameroon was studied through field geologic mapping and geochemical analysis to evaluate the suitability of limestone for the production of Portland cement and other industrial applications. Field studies reveal four types of limestone deposits: the Mbalangi series, the Kendonge River series, the Ediki River series, and the Mungo River series. The limestones are thinly to thickly bedded (5.0 to 15.6 m), highly indurated, and show crystalline structure with a very fine-grained texture and are associated with shales. Geochemical analyses of limestones from Mungo River Formation (MRF) indicate that the Mbalangi limestone series has the best grade, followed by limestones from the Mungo River series, and the Ediki limestone series. These limestones, according to the CaO/MgO and CaCO₃ scheme, are classified as pure limestones with medium to very high purity, which are all suitable for Portland cement production with less than 0.52 wt% MgO, less than 1.89 wt% FeO, less than 5 wt% total alkalis, and CaCO₃ ranging from 88.86 to 99.80 wt%. These deposits also qualify for use as flux in the steel industry for their high CaCO₃ content and less than 5 wt% SiO₂ content. In addition, the deposits also meet specifications for use in ceramics with >79 wt% of CaCO₃. Furthermore, the Mbalangi limestone series (88.70 to 99.77 wt% of CaCO₃), the Ediki River limestone series (90.05 to 94.55 wt% of CaCO₃), and the Mungo River limestone series (97 to 99.89 wt% of CaCO₃) are suitable for glass manufacture, refractories, chemical production, sugar refining, textiles, agriculture, and soda ash manufacture. The Kendonge limestone series shows low grade with CaO (43.31 wt%), CaO/MgO (28.44), and MgO/CaO (0.04), suggesting magnesian limestone (limey marlstone), which is not suitable for Portland cement production. The negative correlation of calcium oxide with iron (III) oxide and magnesium oxide in these limestone deposits signifies an increase in the leaching of CaO solution in the environment, which, in turn, increases the purity of the limestone, making it suitable for the production of Portland cement.