Browsing by Author "Weerakoon, W.A.P."

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    Structural and Geochemical Characteristics of Limonite ore in Dela Sri Lanka
    (Uva Wellassa University of Sri Lanka, 2013) Weerakoon, W.A.P.; Balasooriya, N.W.B.; Jayawardana, D.T.
    Limonite (FeO.OH (H2O)) is hydrated, amorphous, and non-crystalline form of iron oxide. Limonite contains around 52.86% of iron. In Sri Lanka hydrated iron oxide is present as boulders, hill capping and near-surface deposits, classified as supergene deposits, around Dela- Noragolla (Jayawardena, 1984). The objective of this research is to identify the chemical compositions, weathering grade, weathering pattern, decomposition, and provenance of Dela Limonite. There are only a limited number of detailed geochemical and mineralogical studies carried out up to date. Therefore, present research focuses on filling the gap in knowledge by identifying geochemistry with mineralogical characteristics of the limonite deposit. Each sample was homogeneously crushed. Fresh crushed samples were powdered using mortar and pestle and sieved into < 63 µm size. wave number. The most representative limonite sample (SLDL 01) was analyzed at 25 °C room temperature, obtained with 2Th/Th radiation, operating at 40 kV, 30 mA and diffraction data were compared with references. XRF analysis was carried out using Brucker hand held XRF S1 TITAN instrument for forty (40) selected major and trace elements by having 0.4008 average errors. Results and Discussions , 1100 cm , and 800 cm wave numbers showing water group, P-H bond, organic sulfate, P=O and silicate iron (Coates, 2000; Stringfellow et al, 1993). In XRD analysis minerals were verified as limonite, goethite, quartz and hematite present in the deposit. Measured XRF data are summarized in Figure 2. By comparing with UCC value, it was clearly identified that the Fe2O3, P2O5, and MnO are enriched in this deposit (Figure 3). MgO, TiO2, Cl, Co, and Ce slightly deviate from the UCC value. Al2O3, SiO2, K2O, CaO, S, V, Cr, Cu, Zn, Rb, Sr, Y, Sn have fewer amounts compared to the UCC value. Less amounts of Al2O3, SiO2, K2O, and CaO represent that insignificant amount of feldspar. Low percentage of silica in the deposit revealed that the rock formation was in mafic environments. Having very fewer amount of S and Chalcophile elements trace elements represent that there is no sulphide mineral is a source to form this deposit. Geochemically Ce, and Y are the traces, which were representing formation of apatite as a heavy mineral. By enrichment of P2O5, and fewer amount of Ca, Cl, OH, Ce and Y indicated that the apatite was present as a gangue mineral in this deposit. ‎
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    Structural and Geochemical Characteristics of Limonite ore in Dela, Sri Lanka
    (Uva Wellassa University of Sri Lanka, 2013) Weerakoon, W.A.P.
    Iron ore is a natural abundant mineral commodity, including oxides, hydroxides, silicates, carbonates, and sulfides. Goethite (FeO.OH) and Limonite (FeO.OH (H2O)) are hydrated form of iron and amorphous and non-crystalizing form of iron containing around 52.86% of iron. In Sri Lanka hydrated iron oxide- present as boulders and near surface deposits. This is classified as Supergene Deposits of Dela-Noragolla type present in Highland Complex. Main objectives of this research are to identify the chemical compositions, provenance, weathering grade, weathering pattern, and decomposition of Dela limonite during Holocene period by identifying geochemistry with mineralogical characteristics of the deposit. For that fresh 26 limonite samples were collected. Powders of the samples were analyzed using FTIR, XRD and XRF. Develop the base map for the deposit. FTIR analysis revealed several peaks in 3570 cm- 1, 2360 cm-1, 1420 cm-1, 1350 cm-1, 1100 cm-1 , and 800 cm-11 wavenumbers showing water group, P-H bond, Organic sulfate,P=O and silicate iron. In XRD analyzing minerals were verified as limonite, goethite, quartz and hematite represent in the deposit. Geochemically enrichment of Fe2O3, MnO, P2O5, low amount of silica, S, trace elements and Chalcophile elements in the deposit identified that the initial rock formation in mafic or ultramafic source environments. Geochemical analyzed revealed that apatite is present as the gangue. Then metasedimentary processes were taken place to evolve the deposit. Base rock of the area is khondalites. Sr, Rb traces show deposit was exposed to weathering and digenesis. SiO2, A1203, MnO, P2O5, CaO, and S is depleted with in past 50 years and Fe percentage is increased about 10% because other elements were leached out and form laterite in certain areas of the deposit. The trace elements in sediments are positively correlated with A1203 because they are readily adsorbed on to clays during weathering, transport and depreciation. Key words: Limonite, hydrated iron oxide, Supergene Deposit, provenance, weathering, decomposition, Holocene, geochemistry, .FTIR, XRD and XRF, khondalite, apatite, mafic, metasedimentary, and laterite.