GEOCHEMICAL CHARACTERISTICS OF HYDRATED IRON-ORE DEPOSIT IN DELA, SRI LANKA

Abstract

Sri Lanka is well known for different kind of iron-ore deposits in the Precambrian basement. Among them, hydrated iron ores are predominant in the south-west region. This study describes geochemistry, weathering, alteration and provenance of hydrated iron-ore deposit in order to examine different chemical processes association with iron-ore generation. A field survey was carried out in forty four (44) localities around Dela and X-ray Fluorescence Spectroscopy (XRF) was used to obtain concentrations of forty (40) major and trace elements from ore samples. Fourier Transform Infra Red Spectrometer (FTIR) was used to analyse several samples in order to study weathering and alteration of the ore. Average Fe2O3 concentration of 88 wt% reflects high grade iron-ore. Conversely, all the other major oxides (MgO, Al2O3, SiO2, P2O5, MnO, CaO and TiO2) concentrations are not significant. Based on geochemical discrimination the deposit falls in to Phanerozoic iron stones indicating igneous intrutions to the Precambrian basement. The deposit can be conceded as detritus-free when originated since minute concentrations of trace elements are reflected in the samples. Major oxides of the study show residual enrichment of Fe2O3 due to effective leaching of mobile phase. Lower abundances of immobile trace elements may reveal lack of commonly known heavy minerals within the iron bearing formation. The FTIR spectrum of the iron-ore samples clearly demarcate chemical weathering processes as imposed by the deposit such as formation of secondary minerals (limonite), silicate oxidation and phosphorous decomposition.