Browsing by Author "Subasinghe, N.D."

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    Confirmation of Newly Discovered Area in Eppawala Phosphate Deposit Using Geological, Geochemical and Geophysical Methods
    (Uva Wellassa University of Sri Lanka, 2018) Kumari, M.M.T.D.M.; Subasinghe, N.D.; Attanayake, A.N.B.; Samaranayake, S.A.
    Parent rock of the Eppawala apatite deposit is suggested to be a carbonatite in origin and one of the associated minerals of apatite is magnetite. A high concentration of magnetite has been seen within the deposit. A regional ground magnetic survey concluded that the deposit extends to the North further than the formally known boundaries. Also, the studies indicate that the deposit runs along the E-W direction as two ore bodies. Appear in this study, the newly discovered area in Eppawala phosphate deposit was demarcated using geological, geochemical and geophysical methods. Geological studies revealed the presence of carbonatite and apatite outcrops along E-W direction. Representative soil samples were collected during field work for chemical analysis. As the carbonatite is highly weathered anomalous peak of calcium and magnesium should be recorded in the samples collected along the magnetic anomaly, which in turn help to identify the presence of carbonatite bodies within the subsurface. In deeper horizons along E-W direction, the elemental availability is relatively high (High peak values of Ca, Mg in anomalous area is 5000 mg kg-1, 1655 mg kg-1 and in background it is 890 mg kg-1, 720 mg kg-1, respectively) which indicates the possible presence of subsurface carbonatite bodies. Resistivity surveys were carried out in the study area and resulted resistivity signatures show similarity to the known phosphate deposit. Detailed magnetic map resulted from the magnetic survey done by early workers confirmed the boundary indicated in the magnetic anomaly map. Hence existence of the newly discovered deposit in Eppawala along E-W direction was verified by using integrated geological, geochemical and geophysical study.
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    Estimating the magnetite content of the Southern part of Eppawala Phosphate Deposit and its parent rock
    (Uva Wellassa University of Sri Lanka, 2015) Erandi, H.P.V.H.; Aththenayake, A.N.B.; Subasinghe, N.D.; Prame, W.K.B.N.
    Phosphorus is one of most important plant nutrients because its function cannot be performed by any other nutrient. Phosphate fertilizer is mainly produced from the natural phosphate rocks worldwide. Phosphate deposit at Eppawala is one of the most economically valuable mineral deposits in Sri Lanka. It contains up to 42% of P2O5 while the citric acid solubility of various components varies from 4% to 6%. Due to strong weathering of apatite-bearing parent carbonatite rock, an economically valuable secondary phosphate deposit has formed (Subasinghe, 2013). Former studies revealed that iron leaching from weathering parent rock played an important role in fixing phosphate and formation of secondary deposit through in-situ diagenesis (Subasinghe, 2012). Source of iron is assumed to be magnetite and other iron bearing minerals. To reap grater benefits from the deposit it is necessary to produce value added products such as triple super phosphates. Due to considerable amount of iron impurities from magnetite and other iron baring minerals, the production of super phosphate may pose some difficulties at industrial level. The objective of this study is to develop a methodology to estimate the magnetite, the main iron- bearing mineral, in the phosphate ore.
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    Identification of Near Surface Water Flow Path in Kanniya Hot Water Spring
    (Uva Wellassa University of Sri Lanka, 2018) Chathuranga, H.D.N.; Subasinghe, N.D.; Premachandra, N.P.; De Silva, S.N.; Samaranayake, S.A.; Bandara, H.M.D.A.H.
    Although Sri Lanka is not located in an active volcanic region or in the vicinity of an active plate margin, the country possesses unexplored geothermal resources with potential for development as a source of renewable energy. As the present trend for geothermal prospects of low-enthalpy metamorphic terrains become a focus overriding conventional magmatic provenances, Sri Lanka is well placed to explore the same. Prospects for low to medium temperature geothermal resources can be expected to spread across the hot springs belt of Sri Lanka. Low to medium temperature geothermal resources have direct applications in food processing, fruit drying, refrigeration and recreational activities. Delineating the source characters of prospective geothermal fields in geological perspectives would be the initial step towards addressing this untapped energy source. Thorough geological mapping along with geophysical applications would pave the way for such source characterization. Geochemical analysis further provides necessary clues on the potential of the source, its provenance and temperatures. Among many geothermal fields that are scattered in the SE to eastern region of the island, Kanniya site was selected for this study. Objective of this study was to identify the near surface water flow path in Kanniya hot water spring which is one of the major hot spring fields located in Sri Lanka near Trincomalee. One-Dimensional and TwoDimensional resistivity survey and magnetic survey were used for subsurface layer mapping of the area and the results were synchronized with the elevation model. The results showed that the flow path is in Northeast - Southwest direction line receiving from beneath a quartz hump. According to the topography of the area, water flow is towards the sea in Northeast direction. Therefore, it is possible to conclude that the near surface water flow path in Kanniya hot water spring is towards the Northeast direction. Presumably the quartz layer acts as a conduit for such flow, due to its high permeability character.