Parallel Session 2B

The seasonal variations of heavy mineral concentrations in coastal sediments affect nearshore sediment dynamics, mineral resource potential, and depositional processes. This study investigates the influence of monsoonal wave dynamics on the heavy mineral distribution along the Kaluthara coast in southwest Sri Lanka, which is an active sedimentary environment shaped by the discharge of the Kalu river and is influenced by both Southwest (SW) and Northeast (NE) monsoons. Sediment samples were collected from 10 locations post-SW and post-NE monsoons from the beach face. Bromoform (SG = 2.89 g/cm3) was used for the separation of heavy minerals from the sediment samples. The results showed significantly higher Total Heavy Mineral concentrations during the post-NE monsoon season, in contrast to the post-SW monsoon season, which is associated with high-energy wave activity, possibly due to erosion and sediment reworking. This highlights the dynamic relationship between seasonal hydrodynamics and heavy mineral enrichment. This study contributes valuable insight to the temporal behavior of heavy mineral accumulation, which can be helpful in mine planning and exploration.

Abandoned quarry sites require suitable rehabilitation approaches based on comprehensive assessments. Site characterization based on rock properties, weathering, geological and hydrological information are common for such purposes, whereas this study attempts to integrate both in-situ and ex-situ radioactivity measurements of gamma ray spectrometry analysis of representative soil and rock samples collected from the site. Field observations documented rock properties including color, weathering, and rock type. The mean values of activity concentrations of K-40, U-238, and Th-232 in rock samples were 694.38 Bq/kg, 38.70 Bq/kg, and 60.63 Bq/kg respectively. In soil samples, the mean values of activity concentrations were 637.04 Bq/kg for K-40, 23.73 Bq/kg for U-238, and 90.52 Bq/kg for Th-232. All these values except U-238 in soil exceed global average concentrations for soil radiation, indicating a significant radiological impact. Higher radioactivity correlated with less weathered, light-colored rocks like feldspathic gneiss, while relatively lower levels were found in highly weathered, dark-colored rocks like biotite gneiss. The findings highlight the importance of assessing radioactivity alongside rock property characteristics to develop effective and safe rehabilitation strategies for this quarry site.

Sri Lanka, mainly depends on non-renewable energy sources. It is essential to meet the country’s energy demand by developing and adopting renewable sources. This study was conducted to assess the geothermal potential of Wahawa geothermal field through integrated geophysical and geochemical methods. The water samples collected from 12 locations of the field were used for the geochemical characterization. The geochemical characterization to calculate the reservoir temperature included in-situ measurements such as pH, electrical conductivity, and wellhead temperatures along with major anion and cation analysis using Ion Chromatography and Microwave Plasma-Atomic Emission Spectroscopy respectively. The gravity, magnetic and resistivity data obtained from the geophysical measurements were used in determining the geometry and the location of the heat source. Gravity, resistivity and magnetic results collectively supports the presence of a geothermal reservoir associated with the dolerite dyke intrusions. A hypothetical model was developed for the geothermal field using the geochemical and geophysical data obtained. The geothermometric calculations estimate the maximum reservoir temperature to be 186 °C, corresponding to an energy input of 697.2 kJ/mol. The Monte Carlo volumetric assessment shows with a 90% probability that the reservoir could produce 2.6 MWe over a period of 30 years.

Sri Lanka hosts historically significant thorianite deposit in the Neluwa region, which may still contain valuable thorium-bearing minerals. Renewed global interest in thorium for advanced clean energy technologies, higher technological applications, and national economic development underscores the importance of this study. This research investigates the presence and distribution of thorium through mineralogical and geochemical analyses of the abandoned mine. Sampling involves surface samples, pegmatitic rock, subsurface sediments, and plants. A multidisciplinary approach for field inspections including radiometric surveys, heavy mineral separation using bromoform, microscopic analysis to identify thorianite crystals and elemental analysis using Inductively Coupled Mass Spectrometry (ICP-MS) to quantify targeting thorium. The results provide insight into zones with potential for thorium, significant surface sediments, subsurface sediments, rock, and plants. The findings suggest that the Neluwa abandoned mine represents a significant natural trap for thorium-bearing heavy minerals, particularly in subsurface sediments. While mineralogical and geochemical evidence supports resource potential, the observed bioaccumulation underscores environmental and health risks. This study highlights the value of integrated geochemical and mineralogical approaches in evaluating radioactive mineral anomalies.

This research introduces an integrated strategy to the investigation of alluvial gem deposits in the point bar settings of the Mahaweli River in Nawalapitiya, Sri Lanka, through the synthesis of systematic drilling and geochemical methods. Over the shortcomings of conventional surface prospecting, five boreholes were investigated through core logging, sieve-based heavy mineral separation, and ICP-MS analysis to trace subsurface gem-bearing horizons. The highest concentrations of gems occurred in the upstream sections of the point bars, specifically within the Blackish Gray Fine to Medium Sands, which showed high levels of aluminum, chromium, and light rare earth elements. The stratigraphic study revealed a downstream fining trend with a corresponding decrease in gem and heavy mineral concentration. Geochemical ratios Rb/Sr, Ba/Sr, and (Rb×Ba)/Sr² were effective in demarcating zones of high potential. The results illustrate that the synthesis of stratigraphy-oriented drilling with selective geochemical profiling improves the accuracy and efficiency of resource identification. The methodology introduced is a cost-effective and robust framework for sustainable gem exploration in fluvial environments and has applicability to analogous depositional settings worldwide.

The concept of Nature Positive (NP), which emphasizes the restoration of natural ecosystems, has gained increasing attention in recent years. In the context of closed mines, achieving a balance between the assessment and restoration of natural capital has become an urgent challenge. However, it has been difficult to maintain an accurate and continuous understanding of on-site conditions at these sites due to the extensive spatial scale of mine sites. This study investigates the application of digital twin technology, which replicates physical environments in cyberspace, to support NP-aligned assessments of natural capital in closed mine management. The research focuses on tailings storage areas at a closed mine in Hokkaido, Japan, where aerial imagery acquired by drones was processed using Structure from Motion (SfM) to generate point cloud data and construct 3D models. Orthophotos were also produced through orthorectification. In addition, photorealistic images were rendered using 3D Gaussian Splatting, which enables free-viewpoint observation and supports the assessment of natural capital. The results demonstrate the potential of these technologies as effective alternatives to conventional on-site visual inspections. By integrating 3D visualization and spatial data, this study establishes a technological foundation for the objective assessment of environmental conditions at closed mine sites, contributing to the realization of Nature Positive mining practices.

Rare Earth Element (REEs) are essential to diverse industries, including telecommunication, advanced manufacturing to green energy technology. Heavy mineral sand deposits often contain REE-bearing minerals such as monazite, xenotime and zircon, making their accurate identification crucial for efficient resource extraction. Monazite, in particular, exhibits distinct and consistent absorption features associated with the trivalent neodymium (Nd3+) ions at 580, 740, 800 and 870 nm and samarium (Sm3+) between 700 and 900 nm. This study investigates the spectral behaviour of monazite and its potential as a diagnostic indicator of REE presence using hyperspectral imaging in the visible and near-infrared (VNIR) range, combined with machine learning algorithms. Neighbourhood component analysis (NCA) was computed to identify the most informative wavelengths, revealing key bands at 472.59 nm, 522.18 nm, 525.1 nm, 577.96 nm, 625.22 nm, 678.71 nm, 744.53 nm, 798.77 nm, 801.79 nm, 871.6 nm. These persistent and well-defined features confirm monazite’s utility as a robust spectral indicator for REE-bearing mineral in heavy mineral assemblages.

Accurate estimation of shale gas content and production rate is crucial for large-scale shale gas commercialisation. However, limited understanding of shale pore structures and gas accumulation mechanisms has hindered prediction accuracy. This study focuses on the northern Fuling shale gas field in China, where pore size distribution (PSD) models were constructed using literature data. Combined with gas storage and flow behaviour and the phase equilibrium model, a simplified pore structure model was used to develop a storage and seepage model. Results indicate that PSD can be reasonably fitted by both single and segmented curve models. As maximum pore size increases, free gas becomes more dominant and flows mainly in slip flow. Permeability rises linearly with temperature and drops exponentially with pressure, while gas content decreases with temperature and increases with pressure. The material of pore walls significantly influences gas content and apparent permeability, with silicon atoms offering more realistic results. The choice of adsorption model also matters; the Langmuir model yields higher permeability values.

This final segment invites reflections from presenters and attendees, synthesizing key insights from the session. The session chair will formally conclude the discussion by summarizing thematic threads, highlighting interdisciplinary contributions, and outlining potential collaborative directions.