Browsing by Author "Dushyantha, NP"

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item: Conference-Full-text
Applicability of a neural network model for forecasting ground vibrations in opencast mining
(Department of Earth Resources Engineering, 2018-08) Dassanayake, SM; Dushyantha, NP; Jayawardena, CL; Abeysinghe, AMKB; Samaradivakara, GVI
Ground vibration and air-blast over pressure are two significant undesirables, among many environmental risks, in open-pit mining . Gaining control over the ground vibrations generated by rock blasts had been difficult mainly due to the complexities involved with local geology and properties of the blast. Accordingly, existing empirical equations are only capable of making vague approximations on the vibration frequencies based on site-specific parameters and attenuation factor. Therefore, the available models cannot be generalized to different geo-mining environments to obtain sufficiently reliable forecasts for ground vibration and airblast overpressure. Hence, this study attempts to employ an Artificial Neural Network (ANN) based feed-forward back-propagation algorithm to train a model, using a supervised learning technique to forecast possible ground v i b r a t i on frequencies. The main in-put parameters included in the model are noise level, number of boreholes per single blast, depth and diameter of a borehole, charge per hole, number of delays of the Electric Detonators (ED) in a single blast, burden and spacing. Airblast overpressure and the ground vibration levels will be the output by ANN model. The model was validated using 50 datasets, which were obtained from a quarry site. After adequate training, the model can determine Peak Particle Velocity (PPV) and frequency of Ground Vibrations (GV) for new input parameters with a statistically significant confidence level.
item: Conference-Full-text
Assessment of rare earth element potential in intrusive rocks special reference to massenna zircon granite
(Department of Earth Resources Engineering, University of Moratuwa, 2020-12) Jayasuriya, JHAATS; Jayathilake, RGMA; Jeyakumar, J; Batapola, NM; Dushyantha, NP; Abeysinghe, AMKB; Premasiri, HMR; Dissanayake, DMDOK; Dassanayake, ABN
Sri Lanka has a geological setting that favors the presence of rare earth elements (REEs), which are currently identified as the most critical and strategic elements in the world. Previous geochemical studies show that intrusive rocks, such as carbonatites, pegmatites and granitoid rocks could be enriched of REEs. Therefore, this research is focused on assessing the REE potential in pegmatites with special reference to the zircon granite in Massenna. The collected samples from the focused areas were subjected for XRD analysis and monazite, apatite, allanite, bastnaesite, and loparite were found as the major RE minerals. Moreover, Massenna zircon granite has the highest REE potential, particularly LREEs and Y, compared to other pegmatites. The presence of REEs in the in-situ soil and sediment samples indicate that, REEs have been transported through weathering and erosion processes of the zircon granite, thus proving the REE potential in the source rock. Furthermore, REEs are mostly associated with felsic minerals rather than mafic minerals. Therefore, this research clearly provides insights of REE potential in the pegmatite bodies in Sri Lanka and more REE explorations need to be carried out in these prospects.
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A comparison of global rare earth element (REE) resources and their mineralogy with REE prospects in Sri Lanka
(Elsevier, 2020) Batapola, NM; Dushyantha, NP; Premasiri, HMR; Abeysinghe, AMKB; Rohitha, LPS; Ratnayake, NP; Dissanayake, DMDOK; Ilankoon, IMSK; Dharmaratne, PGR
Rare earth elements (REEs), a group of 17 elements comprises 15 lanthanides, scandium and yttrium, are largely attracting the world’s attention due to their importance in a wide variety of advanced technological applications. Global REEs production is mainly sourced from resources, such as carbonatites, alkaline igneous rocks, placers, laterites, and ion-adsorption clays. Recently, REE demand has been escalating, especially due to the REE applications in renewable energy and defense sectors, expecting a worldwide shortage of REE supply in the future. Therefore, REEs have been widely accepted as strategic elements in the world, which compels to prospect for new and alternative REE resources. In this context, Sri Lanka has a favorable geological setting which implies the presence of REE mineralization. Previous geochemical studies in Sri Lanka have reported significant concentrations of REEs in different geological formations and mineral resources. Accordingly, Pulmoddai and other beach placer deposits, Eppawala carbonatite, alluvial placer deposits, and pegmatites have been identified as potential REE resources in Sri Lanka. Monazite, apatite, allanite, and zircon are the primary rare earth (RE) minerals found in the preceding resources. The Pulmoddai mineral sand deposit is considered as the most potential REE resource in the island, which is enriched in monazite containing more than 61% of light rare earth elements (LREEs). Similarly, Eppawala carbonatite contains high concentrations of LREEs. However, despite their significant REE enrichments, to date, no attempt has been made to recover these REE prospects, which essentially conceals their potential of catering for both local and global REE supply chains.
item: Conference-Full-text
Exploration and characterization of potential iron ore occurrence in Pelpitigoda, Sri Lanka
(Division of Sustainable Resources Engineering, Hokkaido University, Japan, 2024) Wijethunge, HP; Appuhamy, RPMC; Vilojan, M; Ratnayake, NP; Abeysinghe, AMKB; Premasiri, HMR; Rohitha, LPS; Dushyantha, NP; Batapola, NM; Dilshara, RMP; Iresha, H; Elakneswaran, Y; Dassanayake, A; Jayawardena, C
Iron is widely used across industries in worldwide, with an annual usage of over 1.8 billion tonnes, steadily increasing over decades. Due to this high consumption of iron, it is crucial to find new sources of iron. Therefore, this research project was designed with the objectives of exploring the potential iron occurrence and characterize the mineralogy and geochemistry of the Pelpitigoda area. The methodology comprises two phases. In the initial phase, geological settings were studied to understand the rock formations and structures surrounding the area. It was followed by a magnetic susceptibility survey to identify variations and anomalies, along with systematic sample collection across the deposit. The phase two was completed with laboratory analysis, including sample preparation, colorimetry, X-ray Diffraction (XRD), X-ray Fluorescence (XRF), and Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Notably, colorimetry results from phase two indicated iron content ranging between 40-60 wt% in the samples, with XRD analysis identifying goethite as the predominant mineral, alongside magnetite, hematite, and gibbsite. XRF results revealed an average iron content of 38.47 wt%. Furthermore, ICP-MS analysis showed lower potential for valuable metals like V, Cr, Co, Ni, and Zn in the area. The significance of this research lies in its potential to identify a new iron ore occurrence in the Pelpitigoda area. The comprehensive characterization of the mineralogy and geochemistry provides valuable insights into the composition and distribution of iron-bearing minerals in the area. Future work entails completing the last phase of roasting the samples to extract iron oxide, followed by comprehensive laboratory testing of the prepared samples.
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Exploration for potential sources of rare earth elements in Sri Lanka
(Department of Earth Resources Engineering, University of Moratuwa, 2021-12) Batapola, NM; Ratnayake, NP; Abeysinghe, AMKB; Premasiri, HMR; Rohitha, LPS; Dushyantha, NP; Ilankoon, IMSK; Dissanayake, DMDOK; Dharmaratne, PGR; Dissanayake, DMDOK; Jayawardena, CL
The global demand for rare earth elements (REEs) has been skyrocketing lately due to their excessive usage in numerous high-technologies. Therefore, the current study explores the REE potential in different geological formations of Sri Lanka. Accordingly, REE geochemistry and mineralogy of granites at Massenna (n=10), Arangala (n=6), and Thonigala (n=16); Eppawala phosphate deposit (EPD) (n=20); Ratthota pegmatite (n=6); southwest beach placers (n=18); and Walave alluvial placers (n=20) were analysed by the Inductively- Coupled-Plasma Mass-Spectrometer (ICP-MS) and X-ray Diffractometer (XRD), respectively. Based on the results, only EPD (2676.0-6486.3 mg/kg), Arangala (1634.9-4031.6 mg/kg), and Massenna (65.3-2153.4 mg/kg) showed high total REE (TREE) contents, and they contained REE minerals, such as apatite, monazite, rinkite, mosandrite, and eudialyte. Currently, carbonatites and ion-adsorption clays are the dominant REE sources in the world, and commercial REE extractions are only focused on the minerals: bastnaesite, monazite, and xenotime. In this context, the EPD is the most potential REE source in Sri Lanka (0.46% REO), especially for light rare earth elements considering not only its high TREE content but also the carbonatitic origin and the mineralisation of apatite and monazite. However, the EPD should be further explored for mineralogy, composition, and impurities to assess its viability as a future REE source in Sri Lanka.
item: Conference-Abstract
Exploration of potential sources for extraction of rare earth elements (REEs) in Sri Lanka
(Department of Earth Resources Engineering, 2019-08) Dushyantha, NP; Batapola, NM; Premasiri, HMR; Abeysinghe, AMKB; Rohitha, LPS; Ratnayake, NP; Dissanayake, DMDOK; Ilankoon, IMSK; Dissanayake, DMDOK; Samaradivakara, GVI
Rare Earth Elements (REEs) are a set of seventeen chemically similar elements in the periodic table, including fifteen metallic elements of the lanthanide series. Yttrium and Scandium. REEs are significantly used in numerous high-tech applications in sectors, such as metallurgy, military, petroleum and agriculture. Therefore, REEs are considered as critical and strategic elements i n the industrial revolution towards a green economy i n the future. However, China is the world's largest producer, consumer and exporter of REEs, currently controlling more than 90% of the global supply. According to the recent Chinese industrial policies, they have reduced their REEs export in 2010 in order to build up a REEs stockpile for future domestic uses. As a result, currently, REEs supply is at a risk of disrupting i n the world market, which has created many concerns among REEs stakeholders. Thus, worldwide explorations for REEs are carried out to prospect new potential sources. In this context, Sri Lanka is a country, which has geological settings implying the presence of probable primary REEs sources (e.g. apatite in carbonatites, granitic and synitic pegmatites, granitic rocks and hydrothermal veins) and secondary REEs sources (e.g. mineral sand, gem gravel, stream sediments, clay deposits and laterite deposits). According to previous studies in Sri Lanka, considerable contents of REEs have already been identified in a few locations of the country, such as well-known monazite deposit in Pulmoddai containing Cerium (28%), Lanthanum (15%), Neodymium (10%), Promethium (3%), Samarium (2%), Gadolinium (2%) and Yttrium (1%).Therefore, aforesaid potential sources will be explored as a worthwhile approach to address the impending REEs problems i n both local and global context. However, available resources on land w i l l not be enough to cater the future demand, and therefore, offshore sources, including upwelling areas in southern coast of Sri Lanka are also needed to be investigated as a promising solution for future REEs scarcity. However, effectiveness of extraction of REEs depends on the quality of the resources and the degree to which the resources have been explored. Based on the REE concentrations in aforesaid sources, novel extraction technologies will be developed to get the maximum benefits to the Sri Lankan mineral industry and ultimately to the national economy of the country.
item: Conference-Abstract
Extraction potential of nickel from native hyperaccumulator plants from Ginigalpelessa serpentinite deposit
(Department of Architecture University of Moratuwa, 2024) Dilshara, RMP; Abeysinghe, AMKB; Premasiri, HMR; Ratnayake, NP; Senarath, WTPSK; Ratnayake, AS; Dushyantha, NP; Batapola, NM; Iresha, H; Elakneswaran, Y; Dassanayake, A; Jayawardena, C
Serpentine soils are low-grade Ni resources that have been utilized widely to extract Ni to meet its burgeoning demand in the renewable energy sector. However, the economic impracticability of Ni recovery by conventional mining techniques has been directed towards Ni phytomining, in which native hyperaccumulators grown in serpentine soils are used for commercial Ni recovery. In this context, the Ginigalpelessa serpentinite deposit in Sri Lanka harbors a wide variety of plants that can accumulate high Ni concentrations from the soil. Despite the promising Ni potential (0.4-1.7%) in the Ginigalpelessa serpentinite deposit, the lack of detailed studies on the hyperaccumulation ability of native plant species and proper extraction methods retards the commercial application of Ni phytomining in this deposit. Therefore, the present study carried out ex-situ phytomining trials using two native hyperaccumulator species namely, Crotalaria verrucosa and Apluda mutica. The harvested biomasses were then incinerated to produce Ni-rich bio-ores, which were analyzed for Ni concentration using Inductively Coupled Plasma Mass Spectrometer (ICP-MS). The bio-ore of C. verrucosa contained 7,279 ± 106 mg/kg of Ni whereas the bio-ore of A. mutica showed 3,867 ± 39 mg/kg of Ni. The bio-ore of A. mutica was used for the leaching experiments due to its highest abundance in the deposit. The leaching assays were carried out with A. mutica bio-ore under different pulp densities (100 g/L and 200 g/L) and H2SO4 concentrations (1 mol/L and 5 mol/L). The bio-ores used in leaching experiments were produced from an open flame and muffle furnace (at 550 ⁰C). The highest leaching efficiency was observed as 59% in open burnt samples (leachate Ni concentration = 649 mg/kg and total Ni concentration = 1,098 mg/kg) under 100 g/L pulp density and 5 mol/L H2SO4 concentration. The overall low leaching efficiency of bio-ore can be attributed to the formation of an aluminum silicate matrix (Al2O3.2SiO2) during leaching experiments which inhibits the Ni leaching. Therefore, the present study requires further investigations to optimize the leaching efficiency to implement a sustainable Ni extraction method for the local serpentinite bodies. Financial assistance from the Senate Research Committee, University of Moratuwa (Grant no: SRC/LT/2021/15) is acknowledged.
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Feasibility of extraction of cerium dioxide (CeO2) from monazite at Pulmoddai
(Department of Earth Resources Engineering, University of Moratuwa, 2020-12) Rasanjalee, PHAU; Delaksana, S; Sampath, MD; Dushyantha, NP; Batapola, NM; Dissanayake, DMDOK; Rohitha, LPS; Dissanayake, DMDOK; Dassanayake, ABN
Monazite concentration in Pulmoddai mineral sand deposit in Sri Lanka is 1.38%. Its Rare Earth Elements (REE) composition is about 61%. Currently, only heavy minerals are separated and cerium rich monazite is discarded. Therefore, the study is focused on finding feasibility of extraction of CeO2 from Pulmoddai monazite. The research was conducted under four stages, removal of phosphate ions, removal of radioactive elements, purified Rare Earth oxide (REO) preparation and selective separation of CeO2. The optimum concentration of NaOH solution is found as 80% (w/v)/ 20M. Alkaline digestion was done for 4hrs at 150oC by adding 25 ml of NaOH to 25 g of monazite, followed by acid leaching with 50 ml of 60%(w/v) HCl at 90°C for 1hr. Concentration of 20 g/L (0.22M) oxalic acid should be added to the RE chloride mixture until the complete precipitation of RE oxalates. Purified REO was obtained by calcination at 900°C for 2hrs using RE oxalate precipitated. Purified REO was used to recover CeO2 by subjecting to selective precipitation. Selective precipitation of CeO2 was carried out using solid form of KMnO4 and (15wt%) Na2CO3 solution with maintaining average pH value 4 by manual addition of Na2CO3 solution ([15 g /100 L]/0.001M).
item: Conference-Abstract
Geochemical approach of phosphate mineral exploration in lake sediments around Eppawala phosphate deposit, Sri Lanka
(Department of Earth Resources Engineering, 2018-08) Dushyantha, NP; Hemalal, PVA; Jayawardena, CL; Ratnayake, AS; Ratnayake, NP; Abeysinghe, AMKB; Samaradivakara, GVI
Mineral exploration is a stochastic process of finding and locating commercially viable mineral resources. In this regard, lake sediment is an important material in exploration as it contains three distinct types of minerals i.e. allogenic or detrital minerals (minerals brought into the lake from outside of the lake), endogenic minerals (minerals originated within the lake) and authigenic minerals (minerals formed during the diagenetic alteration of sediments). Koon-wewa, Ihalahalmillawewa and Kiralogama-wewa are three lakes connected with a man-made water canal, namely Jaya-Ganga flowing across the Eppawala Phosphate Deposit (EPD). Kiralogama-wewa is located downstream of the EPD whereas other two lakes are located upstream. Thus, lake sediments in the downstream lake could be influenced by the phosphate-bearing minerals derived from the EPD. The bulk chemical analyses of surface lake sediments showed that average P2O5 concentrations were 0.80% and 0.45% in downstream and upstream, respectively. Further, in downstream, P2O5 significantly and positively correlated with AI2O3, CaO, Fe203, K2O and MnO whereas no such correlations were observed in upstream sediments. Presence of calcium-iron-aluminum phosphate minerals such as fluorapatite, crandallite, millisite and strengite in downstream sediments, revealed via mineralogical analyses, delineated the above correlations. Moreover, high Chemical Index of Alteration (CIA) values were observed in the downstream sediments which indicate intense chemical weathering conditions in the source area. It is justified by the presence of weathering products of the EPD such as crandallite and millisite in the downstream sediments. Grain size analyses displayed a dominant silt fraction in both upstream and downstream areas. Textural analyses in downstream revealed the relative proximity of the source and nature of the material deposition through solid suspension. Presence of fluorapatite (detrital mineral) in downstream is corrobarated the conclusion in textural analyses. Four representative core samples were obtained from both the upstream and downstream lakes. In upstream core samples, P2O5 concentrations varied from 0.03% to 1.81% whereas P2O5 concentrations in downstream core samples varied f r om 0.26% to 2.22%. Continuous sediment supply via Jaya-Ganga can also improve the fertilizing capacity of downstream lake sediments, eventually; becoming a commercially viable phosphate mineral resource.
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Geochemical distribution of selected elements in serpentinite deposit in ginigalpelessa, Sri Lanka
(Department of Earth Resources Engineering, University of Moratuwa, Sri Lanka, 2022-12-23) Dilshan, RADP; Sageenthan, A; Weerangana, NGN; Premasiri, HMR; Ratnayake, NP; Abeysinghe, AMKB; Dushyantha, NP; Batapola, NM; Dilshara, RMP; Jayawardena, CL
Serpentinite deposits are well known for their natural enrichments of heavy metals (Ni, Cr, Co) and depletions of macro nutrients (Ca, Mg), which have caused different ecological and health impacts in the surrounding areas. In addition, they are considered as potential sources for rare earth elements (REEs). While Ginigalpelessa, the largest serpentinite deposit in Sri Lanka, has been the focus of several toxicological studies, to date, there have been no significant studies related to geochemical distribution of heavy metals, macro nutrients, and REEs in the deposit. Therefore, the present study is focused on the assessment of geochemical distribution of selected elements (Ni, Cr, Co, Ca, Mg, and REEs) in the deposit. Accordingly, concentrations of these elements in 30 rock and soil samples were analyzed and their geochemical distributions were studied using the results of the present study and literature. Ni (6629 ppm) and Cr (35875 ppm) showed the highest enrichments in the deposit, whereas all the studied heavy metals have exceeded the permissible levels of the World Health Organization. In addition, a low Ca/Mg ratio was observed in the deposit, which explains the inhibition of plant growth in the deposit. Moreover, the identified areas with high enrichments of Ni, Cr, and Co using the prepared geochemical distribution maps will be useful in the spot remediation for toxicity in the deposit. Since serpentine soil is recognized as a low-grade source for Ni, low-grade extraction techniques such as phytomining and bioleaching are recommended to extract valuable metals from the Ginigalpelessa deposit.
item: Conference-Full-text
Hydrometallurgical approach to investigate the recovery potential of gold available in waste PCBS
(2021-12) Munagamage, SP; Wickramasinghe, BGWMDHK; Asvini, I; Dissanayake, DMDOK; Rohitha, LPS; Dushyantha, NP; Dissanayake, DMDOK; Jayawardena, CL
Gold is one of the highly demanded precious metals which have applications in jewellery, investment, electronic and medical industries due to its unique chemical and physical characteristics. Although the demand for gold is continuously increasing, gold producers have failed to meet the existing demand for gold through gold mining. Therefore, seeking out secondary sources of gold is vital. Since gold is one of the major metals used in the electronic industry, e-waste has enormous potential as a secondary source of gold. This study outlines the recovery potential of gold and several other valuable metals quantitatively in Printed Circuit Board (PCB) components of end-of-life computers, namely, microprocessors and Integrated Circuits (ICs), plated connectors in network cards, and plated metallic pins. The research workflow consists of a sample pre-processing and an acid leaching (digestion) process followed by a sample analysis process using an Inductively Coupled Plasma - Mass Spectrometer (ICP-MS). According to the results, the recovery potential of gold is significant in every e-waste component tested under this study.
item: Conference-Abstract
Identification of potential minerals/rocks in Sri Lankan geological terrain as source of potassium (K) fertilizer
(Department of Earth Resources Engineering, University of Moratuwa, Sri Lanka, 2022-12-23) Nivethithan, T; Ariyawansha, KAPM; Dahlan, ACA; Abeysinghe, AMKB; Ratnayake, NP; Premasiri, HMR; Dushyantha, NP; Batapola, NM; Dilshara, RMP; Jayawardena, CL
Due to the agricultural intensification in Sri Lanka, there is a high demand for potassium (K)-fertilizer inputs. However, in the Sri Lankan geological setting, the presence of major potash sources is minimum though the K- bearing minerals and rocks are abundant. Therefore, exploration of K-bearing mineral deposits is essential to cater the demand of K-fertilizer in the country. In this regard, this research is focused on investigating the K-bearing minerals and rocks in Sri Lankan geological terrain which can be used as K-fertilizers directly or as alternatives for currently available K-fertilizers. During sample collection, K-bearing minerals, such as feldspar and mica and K-bearing gneiss rock samples were collected from Matale, Kaikawala and Kadugannawa areas. Processed samples were subjected to analyse major oxide concentrations and K concentrations and surface topography. Analyses revealed that the highest actual potassium concentrations were presented in orthoclase feldspar (10.35 w/w%) and then biotite mica (9.95 w/w%) whereas other rocks showed the lowest. Based on the results, biotite mica (Kaikawala) and biotite gneiss (Matale) displayed the highest potential for K recovery, whilst the least potential for K recovery was shown in orthoclase feldspar (Kaikawala). However, further studies are recommended to develop this K-fertilizer and to assess whether its application is economically viable.
item: Conference-Full-text
Investigation of rare earth element potential in granitic rocks of Sri Lanka special reference to Thonigala granite
(Department of Earth Resources Engineering, University of Moratuwa, 2021-12) Vinoj, PKL; Kapilarathna, MWCS; Samarakoon, SMPS; Dushyantha, NP; Batapola, NM; Abeysinghe, AMKB; Premasiri, HMR; Ratnayake, NP; Dissanayake, DMDOK; Jayawardena, CL
Rare earth elements include lanthanide series elements plus Sc and Y. These 17 elements are characterised by the European Union (EU) as critical raw materials with significant supply risk due to their broad of emerging technological applications. Due to this ever-increasing demand for rare earth element (REE) related products, new REE-bearing mineral deposits need to be identified and evaluated for the purpose of filling the supply scarcity in the world. Therefore, this research is focused on investigating REE potential in granitic rocks of Sri Lanka, with special reference to Thonigala granitic intrusions. Thonigala granite is enriched with REEs, relatively with high light REE (LREE) concentration. In the rock samples, the average total rare earth element (TREE), LREE, and heavy REE (HREE) concentrations were 328, 285, and 43.1 mg/kg, respectively. The corresponding sediment values were 619, 472, 147 mg/kg, respectively. The presence of REEs in both insitu rock and sediment samples indicated that significant weathering and erosion occurred in the area. Therefore, this research provides insights into REE potential in granitic rocks of Sri Lanka, focusing on Thonigala granite. More geochemical analysis followed by mineralogical and compositional analysis needs to be carried out for future benefit.
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Investigation of rare earth elements potential in iron ore deposits in Sri Lanka
(Department of Earth Resources Engineering, 2021-12) Samarakoon, KGAU; Chamilka, WTH; Areekaran, T; Dushyantha, NP; Batapola, NM; Premasiri, HMR; Ratnayake, NP; Abeysinghe, AMKB; Dissanayake, DMDOK; Jayawardena, CL
Sri Lankan geological terrain is mainly comprised of three different types of Iron ore deposits, which are not in the scale for economic extraction. When we consider the iron deposits on a global scale, most of them are associated with high concentrations of rare earth elements (REE). This research is focused on investigating the potential for REEs of the Sri Lankan iron ore deposits. Three major iron ore deposits of different genesis were selected for sampling, and collected samples were subjected to inductively coupled plasma mass spectrometry (ICP-MS) analysis. Analysis revealed a high potential for REE in Panirendawa and Buttala deposits, while Dela deposits showed the least potential. Although high concentrations were shown in a few samples collected from magnetite deposits, it also contains high variation within a few (10–100) meter distances. This variation was due to different degrees of weathering and transportation of iron ore materials. The highest REE potential was associated with the heavily weathered and transported material rather than the fresh iron ore. If the explored potential for REEs is consistent with the associated geological profile of these iron ore bodies, they could present a mineable REE source for Sri Lanka.
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Mineralogical exploration for rare earth element potential in Kalutara coastal areas
(Department of Earth Resources Engineering, University of Moratuwa, 2020-12) Jayasinghe, HGH; Jayasinghe, SMNM; Mohomad, HH; Ratnayake, NP; Abeysinghe, AMKB; Dushyantha, NP; Dissanayake, DMDOK; Dassanayake, ABN
Rare Earth Element (REE) quantity is a main factor that determines the wealth of a country. The main aim of this study is to discover a new REE deposit that can contribute to the Sri Lankan economy. Calido Beach is a coastal region where Kalu-river joins the sea in Kalutara, Sri Lanka. In this study, this coastal region is divided into four divisions as Kalutara North (KN), Kalutara South (KS), Sand Spit (SS) and river delta. Beach sand (n=5) and river sediment (n=30) samples were collected covering all four divisions and analyzed for mineralogy, grain size distribution and microscopic observation for prospecting unconventional Rare Earth Mineral (REM) sources. Analysis for mineralogy of samples via X-ray Diffraction (XRD) test revealed positive availability of REMs such as Monazite (Ce), Monazite (Nd), Xenotime and Bastnasite. According to grain size distribution (GSD) test results, it was found that sediments in delta had a lesser time for sorting before deposition with relevance to beach sand. Nourishment of REMs into the shore by sea waves and other sources (Beruwala placer deposit, offshore sources) increases the amount of REM content in the study area and the minable quality of beach sand as an economically viable REE source.
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Monitoring beach profile changes and modelling nourishment scenarios for Ratmalana beach
(Department of Earth Resources Engineering, University of Moratuwa, 2020-12) Gunasekara, MP; Madushani, EK; Govinath, J; Ratnayake, NP; Samaradivakara, GVI; Dushyantha, NP; Gunasinghe, GP; Silva, KBA; Dissanayake, DMDOK; Dassanayake, ABN
Sri Lanka is an island nation endowed with a wide range of coastal resources, greatly contributing to the Gross Domestic Product. Coastal erosion is a major issue related to the beaches in Sri Lanka. In this regard, Ratmalana beach is critically important as a potential tourism destination due to its proximity to the capital city and the accessibility to a coastal railway station. To develop a beach as a tourist destination, it is importance to monitor the beach profile changes and find out the remedial measures for erosion prevention. For such a management plan, either hard or soft engineering solutions can be utilized. Out of the soft engineering solutions, the most reliable solution is beach nourishment. In this research, Ratmalana beach was regularly monitored and a numerical model was built by utilizing the public domain of XBeach to model the hydrodynamics in the area. Finally, two nourishment scenarios were modelled, and the optimum nourishment scenario is determined. Beach profile monitoring and calculated sand budget indicates that there is significant erosion during the stormy weather season. Based on grain size analysis, Ratmalana beach has a broad grain size distribution. According to the modelled nourishment scenarios, profile nourishment has shown better performance.
item: Conference-Abstract
Prospecting for unconventional phosphate sources in lake sediments around Eppawala phosphate deposit, Sri Lanka
Dushyantha, NP; Hemalal, PVA; Jayawardena, CL; Ratnayake, AS; Ratnayake, NP
Phosphate fertilizer is an important input in agriculture, in the scenario of increasing food demand with the population increase. Global rock phosphate reserves are finite and exhaustible. This leads to the search for unconventional forms of phosphate. In Sri Lankan conditions, this aspect leads to a systematic study of lake sediments for locating secondary phosphate deposition in the area around Eppawala Phosphate Deposit. A total of 41 sediment samples from lake sediments upstream and downstream of the Eppawala Phosphate Deposit was analyzed to determine the respective phosphate content. Average concentrations of P2O5, CaO and K2O in downstream lake were respectively 0.80%, 0.44% and 0.25%. In upstream lake sediments, the respective values were 0.45%, 0.26% and 0.12%. Correlation analysis of downstream sediments shows a significant positive correlation (r ≥ 0.70) between P2O5 and CaO. Environmentally hazardous elements such as Cd and As were also analyzed in each sample to assess the impact of the excessive and long term usage of fertilizers in the area. Average concentrations of Cd and As in the downstream lake were 76.2 ppb and 28.8 ppb respectively and in the upstream lakes, the values were 396.8 ppb and 845.2 ppb, respectively. Each sample was analyzed to determine the 2% citric acid solubility. Results show that 29% from available total P2O5 in the upstream lake sediments and 44% from available total P2O5 from downstream lake sediments were soluble in 2% citric acid. The study reveals that the lake sediments especially in downstream have more soluble phosphate than in the Eppawala Rock Phosphate. This leads to the fact that downstream sediments have relatively higher amount of phosphate which is more soluble than in the Eppawala Rock Phosphate. Therefore, downstream lake sediments can be used as phosphate fertilizer for short term farming. Further studies on agronomic efficiency of downstream sediments are recommended.
item: Conference-Full-text
Rare earth elements exploration in river sediments (Belihul oya and Samanala wewa areas, Sri Lanka)
(Department of Earth Resources Engineering, University of Moratuwa, 2020-12) Dilshan, MWRR; Prabhashan, HPM; Kalaishanthan, K; Dushyantha, NP; Batapola, NM; Premasiri, HMR; Abeysinghe, AMKB; Dissanayake, DMDOK; Dassanayake, ABN
The global REE deposits are mostly associated with carbonatites, alkaline igneous rocks, ion adsorption clay deposits and placers. In this context, previous geochemical studies of alluvial beds in Sri Lanka have disclosed significant concentrations of REEs. Moreover, the Walawe river basin is located at the boundary between Highland Complex and Vijayan Complex, which is a highly mineralized belt. Therefore, this study is focused on assessing the REE potential of stream sediments in Samanala-wewa reservoir and its upstream and downstream areas (i.e. Walawe river basin). The collected samples (n=26, covering 9 locations associated with Walawe river, Belihul Oya, Hiriketi Oya and Denagan Oya) were processed (< 63 μm grain size) and analyzed using XRD to identify their mineralogy. Monazite, bastnaesite, loparite and xenotime are the major RE minerals found in these samples. Additionally, the sampling locations were confined to six stream paths and a correlation was found between the stream order, and the number of REEs present at the location. Overall, this study provides a qualitative interpretation of the REEs present in the stream sediments of the study area. However, detailed quantitative analyses are required to further assess the true REE potential in this prospect.
item: Conference-Abstract
REE Potential in carbonatite deposits: a case study of Eppawala carbonatite
(Department of Earth Resources Engineering, University of Moratuwa, 2020-12) Batapola, NM; Dushyantha, NP; Premasiri, HMR; Abeysinghe, AMKB; Rohitha, LPS; Ratnayake, NP; Dissanayake, DMDOK; Ilankoon, IMSK; Dharmaratne, PGR; Dissanayake, DMDOK; Dassanayake, ABN
Rare earth elements (REEs) are currently the most strategic elements in the world due to their significance in the diversified technological applications. Currently, a total of 478 million tonnes of REE resources is disseminated across the world, which is dominated by the carbonatite deposits. The most common REE-bearing minerals found in carbonatites are bastnaesite, apatite, monazite, allanite and parisite. In this regard, the Eppawala carbonatite in Sri Lanka could be considered as a potential REE resource. The Eppawala carbonatite occurs in high-grade meta-sedimentary and igneous rocks of the Precambrian Wanni Complex as massive intrusions. In the Eppawala carbonatite, bed rock is mainly composed of calcite (~90%), dolomite (5-9%) and magnesite (accessory carbonate mineral), whereas chloro-fluor-hydroxyapatite, fluorapatite and carbonate-fluorapatite are present in a secondarily developed phosphate-rich regolith. The Eppawala carbonatite is enriched of REEs (~291-1962 ppm) with higher concentrations of LREEs. However, despite these evidences, only a few REE prospecting studies have been carried out in the Eppawala carbonatite. Therefore, detailed REE prospecting studies are recommended to discover the full potential of this prospect, followed by development of suitable REE extraction processes.
item: Conference-Abstract
Spatial distribution of heavy metals in sediments of the Negombo Lagoon, Sri Lanka
(Department of Earth Resources Engineering, University of Moratuwa, Sri Lanka, 2022-12-23) Nanayakkara, CJ; Partheepan, N; Kumarapperuma, MY; Ratnayake, NP; Premasiri, HMR; Abeysinghe, AMKB; Dushyantha, NP; Batapola, NM; Dilshara, RMP; Jayawardena, CL
Heavy metals accumulate in the sediments of aquatic environments due to poor water solubility. Their toxic effect poses a significant threat to living organisms. Negombo Lagoon, a vital aquatic ecosystem in Sri Lanka, has become vulnerable to heavy metals mainly from urbanization-related anthropogenic activities. Previous research in this respect has sampling points restricted to the boundary area. Since the heavy metal concentration is a static parameter, continuous research needs to keep the data updated. This study aims to investigate the spatial distribution of several heavy metals (Cr, Ni, Co, Cu, As, Cd, and Pb) in the surficial sediment of the Negombo Lagoon. Fifteen grab sediment samples were collected from the lagoon and analyzed for heavy metal concentration and grain size. The range of concentrations of each metal in test samples were between (78.07 - 222.68 mg/kg) Cr, (376.7-1298.05 mg/kg) Ni, (15.875-43.74 mg/kg) Co, (32.45-112.79 mg/kg) Cu, (20.17-55.81 mg/kg) As, (0.30-1.4 mg/kg) Cd, and (16.57-70.97 mg/kg) Pb. Heavy metal concentrations and sediment grain sizes show significant spatial variation over the Negombo lagoon area. Heavy metals were highly concentrated in locations, where finer sediments are accumulated (i.e., towards the eastern and southern part of the lagoon). Heavy metal concentrations were found to be increased with the decreasing grain size. High heavy metal concentrations are also found at places where there is a river discharge. Among the sources which feed heavy metals into Negombo Lagoon anthropogenic activities such as municipal and industrial waste disposal, rapid urbanization, shipping, and naval activities etc. have a significant impact.