Influence of nearshore sediment dynamics on the distribution of heavy mineral placer deposits in Sri Lanka

Amalan, Kananathan; Ratnayake, Amila Sandaruwan; Ratnayake, Nalin Prasanna; Weththasinghe, Shanaka Maduranga; Dushyantha, Nimila; Lakmali, Nalika; Premasiri, Ranjith

doi:10.1007/s12665-018-7914-4

Cited by 42 publications

(18 citation statements)

References 39 publications

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“…1 ). Almost all of these deposits are mainly composed of ilmenite, and exploitable amounts of leucoxene, rutile, garnet, monazite, zircon, and sillimanite as well as minor amounts of magnetite (Amalan et al 2018 ). Interestingly, these deposits are naturally conserved due to annual partial replenishment during the northeast monsoon.…”

Section: Resultsmentioning

confidence: 99%

State-of-the-art and perspectives in the heavy mineral industry of Sri Lanka

2021

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Heavy minerals have become an essential commodity in modern-day technology. The objective of this study is to examine the current status of the heavy mineral industry of Sri Lanka. The present study also examines the economic viability of potential heavy mineral placer deposits, based on geochemical data. Field investigations suggested the occurrence of heavy minerals as beach-placers, and inland/raised beach deposits along the coastline of Sri Lanka. Geochemical results showed the enrichment of TiO 2 , Fe 2 O 3 , Al 2 O 3 , and trace elements, and depletion of other major oxides such as Na 2 O, K 2 O, MnO, MgO, CaO, and P 2 O 5 . Consequently, it suggests the abundance of ilmenite, leucoxene, rutile, sillimanite, garnet, and rare earth element (REE)-bearing heavy minerals in potential placer deposits. In contrast, this study illustrates the exported quantity (in the weight ratio of 35:3:1) of ilmenite, rutile, and zircon minerals during the last decade. Ilmenite is the dominant heavy mineral in Sri Lanka, and thus, its production and price volatilisations are essential to understand the current status and predict the future behaviour of the heavy mineral industry. Statistical observations suggest that the global production and unit price variations of ilmenite have increased gradually from 1950 to 2015. Besides, the forecasted variations in annual global production and unit price changes of ilmenite indicate healthy compound annual growth rates of 1.27% and 1.43%, respectively. However, Sri Lanka has less contribution (< 1%) to global ilmenite production. Consequently, the value addition of ilmenite must be highly encouraged with at least an immediate stage (e.g. synthetic rutile). The present study also highlights possible value addition stages of available heavy mineral resources (low-, intermediate-, or high-level value addition), and discusses action plans to improve the quality of the heavy mineral industry of Sri Lanka. In recommendations, imposing sustainable regulations and policies would uplift the heavy mineral industry of Sri Lanka. For example, value addition to local heavy minerals and terminating raw commodity export are highly recommended.

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Section: Resultsmentioning

confidence: 99%

State-of-the-art and perspectives in the heavy mineral industry of Sri Lanka

2021

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“…grasses) in muddy sediment of the shallow area of Negombo Lagoon. However, the bottom of the lagoon mouth (Figure 1) is mainly composed of sandy sediments that are transported by longshore currents along the western coast of Sri Lanka (Amalan et al, 2018;Ratnayake et al, 2019b). Table 1 shows the results of the accelerated mass spectrometry (AMS) 14 C analysis.…”

Section: Lithology and Geomorphologymentioning

confidence: 99%

Geochemistry of Negombo Lagoon sediments in Sri Lanka: implications for environmental monitoring

Wijesinghe

Ratnayake

2021

J. Natn. Sci. Foundation Sri Lanka

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Negombo Lagoon is one of the largest lagoons in Sri Lanka. This study focused on the geochemical evaluation of poorly understood tropical subtidal sediments of the western coast, Sri Lanka. Geochemical characteristics of sediments were examined using δ 13 C and δ 15 N stable isotopes, X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR) analyses. The chronology was determined using accelerated mass spectrometry (AMS) 14 C dates for undamaged two shells. Stratigraphic observations suggested grey to blackish finegrained muddy clay sediments in the subtidal mudflat. The calculated organic matter and carbonate contents decrease slightly from bottom to surface sediments. Bulk C/N ratios and δ 13 C values suggested terrestrial organic matter dominant sediments such as from mangrove swamps mixed with marine dissolved organic carbon. XRD identified the crystalline phases present in sediments and thereby chemical composition was identified by the software as illite, montmorillonite, and quartz. It indicates the deposition of limited chemical weathering materials from near distance sources. FTIR identified several functional groups such as carboxylic, polysaccharide, carboxylate ions, and aliphatic substances in the lagoon sediments. The variations of carboxylic groups/carboxylate ions indicate a slow rate of decomposition of organic matter during early diagenesis. Humification and decomposition proxies also indicate slow rates of decomposition under the anoxic condition. However, Negombo Lagoon still acts as a healthy ecosystem under the minor influence of sewage/ agricultural nutrient contamination.

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“…Significant amounts of suspended sediments can be taken away from shoreline, implying the occurrence of coastal erosion. Sediment movement also varies seasonally, depending on incoming wave and water current characteristics, as well as monsoons (Amalan et al, 2018;Ratnayake et al, 2018;Ismail et al, 2020;Shetty and Jayappa, 2020;Zulfakar et al, 2021). Based on the theory of sediment budget (Kamphuis, 2010), coastal erosion can occur when the quantity of incoming sediment is less than the quantity of sediment leaving a certain coastal cell.…”

Section: Introductionmentioning

confidence: 99%

Intertidal intercepted sediment at jetties along the Gulf of Thailand

et al. 2022

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Sand bypassing is one of the promising solutions to rectify jetty-induced coastal erosion. Estimating alongshore sediment transport rate and understanding hydrodynamic conditions at a jetty are crucial for successful downdrift erosion management. This research investigated three major jetties in Thailand (Cha Am jetty, Krai jetty, and Na Saton jetty) that protrude across the surf zone and completely intercept alongshore sediment transport. Sub-aerial and inter-tidal field surveys by Real Time Kinematic (RTK) technique were undertaken in 2019 and 2020. The collected data was processed and overlaid to calculate the amount of sediment deposition at the updrift jetty. Numerical simulations using MIKE21 SW and MIKE21 HD were carried out in order to understand how waves and water currents interacted with the jetties. From the results, we found that the Cha Am jetty trapped approximately 38,187 cu.m/yr of the alongshore sediment. While the Krai jetty intercepted approximately 34,170 cu.m/yr of the alongshore drift, and approximately 65,951 cu.m/yr of longshore sediment transport was blocked by the Na Saton jetty. Such estimated amounts of deposited sediment are the quantities that should be bypassed at each jetty. Budgets and implementation plans for sand bypassing can be prepared. Decision makers can decide how to manage updrift deposition and downdrift erosion.

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Influence of nearshore sediment dynamics on the distribution of heavy mineral placer deposits in Sri Lanka

Cited by 42 publications

References 39 publications

State-of-the-art and perspectives in the heavy mineral industry of Sri Lanka

State-of-the-art and perspectives in the heavy mineral industry of Sri Lanka

Geochemistry of Negombo Lagoon sediments in Sri Lanka: implications for environmental monitoring

Intertidal intercepted sediment at jetties along the Gulf of Thailand

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