Geological And Petrographic Study Of Limestone Deposit At Kalambaina Sokoto Basin Northwest Nigeria

The Kalambaina Formation Limestone deposit in northwest Nigeria is the largest limestone deposit in Nigeria.The ore body extends for tens of kilometers and the thickness of the ore body is about 5-20 meters.It is the main raw material of the local cement industry.This paper carried out the detailed field investigation of the deposit,the indoor identification of rock and minerals,petrography and elemental geochemistry analysis,and obtained the following main understanding:(1)Field investigation confirmed the existence of two obviously different types of ores in this deposit,namely,high-grade limestone ore and low-grade limestone.The two types of limestones are considered as conformable contact in the field.(2)Identifications of rock and minerals show that the major minerals and their proportions in high-grade limestone ores are calcite(55%),clay minerals(30%),quartz(5%),other opaque minerals(such as organic carbon,pyrite,etc.,10%).The main minerals and their proportions in low-grade limestone ores are: calcite(40%),clay minerals(30%),quartz(10%),other opaque minerals(such as organic carbon,pyrite,etc.,20%).(3)The contents of other major oxide(Si O2,Mg O,Ti O2,Fe2O3,Al2O3)were significantly lower than that of low-grade limestone ores,except for the CaO content(53.03%-54.10%)which was significantly higher than that of low-grade limestone ores(40.60%-43.09%).(4)The chemical classification of limestone and interpretation of the paleoenvironmental characteristics of the occurrence of calcium deposition indicate that the limestones were deposited in a protected marginal neritic environment with argillaceous sediment flux derived from a continental crust.Presence of marine gastropods and foraminifera fossils,calcite crystals exhibiting spherulitic texture observed in the thin section and higher concentration of strontium(Sr)in the studied Limestone rocks suggest relatively shallow marine environment of deposition during the Eocene sedimentation.The high grade limestone shows extinct cemented microcrystalline quartz indicating precipitation from solutions that are undersaturated and a more stable single crystals of Calcite.