Elemental Mapping for Characterizing of Thorium and Rare Earth Elements (REE) Bearing Minerals Using µXRF

Aspek kegunungapian merupakan salah satu aspek penting dalam survei pemilihan calon tapak Pembangkit Listrik Tenaga Nuklir (PLTN). Survei bahaya gunung api dilaksanakan pada radius 150 km dari calon tapak PLTN, meliputi survei produk gunung api tua hingga gunung api aktif. Salah satu gunung api muda di daerah Kalimantan Barat adalah Gunung Api Semadum yang terletak di Desa Pisak, Kecamatan Tujuhbelas, Bengkayang berumur Pliosen-Plistosen dengan jarak 115 km dari calon tapak PLTN di Pantai Gosong, Kecamatan Sungai Raya, Bengkayang, Kalimantan Barat. Tujuan penelitian ini adalah untuk mengetahui karakteristik dan potensi bahaya gunung api Semadum terhadap rencana Calon Tapak PLTN. Metodologi yang digunakan adalah interpretasi citra DEM-SRTM untuk mengetahui pola topografi, dilanjutkan dengan kegiatan lapangan pemetaan geologi, pengambilan contoh batuan produk gunung api Semadum dan analisis Petrografi serta geokimia menggunakan X-Ray Fluorescence (XRF). Gunung Semadum tersusun oleh lava andesit-basalt berstruktur vesikuler-skoria, lava andesit berstruktur masif, batuan piroklastika berupa breksi piroklastik dengan fragmen andesit (bom dan blok), breksi lapili/tuf, dan kubah lava. Kompleks ini secara geokimia tersusun atas trakhiandesite dan dasit yang memiliki afinitas calc-alkaline. Berdasarkan sifat magma dan sebaran produknya, gunung api Semadum tidak memiliki potensi bahaya gunung api terhadap Calon Tapak PLTN.

Radiometric mapping could play a prominent role in locating the host rock or alteration that leads to gold mineralization. Nevertheless, in low-sulfidation epithermal gold deposits, the radiometric signatures have to be priorly characterized due to their geometry. It is comprised of a small ore vein system within the large alteration zones. The Pongkor gold mine is a low-sulfidation epithermal deposit and was selected for this purpose. The method started with the surface identification of radiometric signatures on altered and unaltered rocks near Pongkor using portable spectrometers. They are followed by the characterization of the underground mining front, which is comprised of different types of veins and host rocks. The results show that the altered rocks were characterized by a high K% and a low eTh/K ratio. Vice versa, the mineralized veins show low radioelement concentrations. Following the characterization of the geometry of alteration zones and mineralized veins, a study of the relationship between radioelements detected by radiometric mapping and gold pathfinder elements was conducted. Gold pathfinders of Mn, Fe, Zn, As, and Pb were selected for correlation studies with the radioelement. The pathfinders and radioelements were more significantly correlated in veins compared to the host rock. Based on this study, radiometric mapping has the potential and benefit of being applied in the exploration of low-sulfidation epithermal gold deposits. An alteration zone could be delineated by K or eTh/K as an anomaly indicator, and the vein bodies could also be delineated using low K or eTh as an anomaly indicator.

The Mamuju region in West Sulawesi, Indonesia, is a High Background Natural Radiation Area (HBNRA) characterized by a significant enrichment of high field strength elements (HFSEs) and rare earth elements (REEs) within its lateritic deposits. This study investigates the geochemical behavior, mineralogical distribution, and enrichment processes of HFSEs and REEs in lateritic profiles of drill cores and surface samples derived from alkaline volcanic rocks. The mineralogy and geochemical content of HFSEs and REEs in the alkaline bedrocks indicate its potential to become a source of lateritic enrichment. An intense lateritic weathering process leads to the residual accumulation of HFSEs and REEs, particularly in B-horizon soils, where clay minerals and Fe–Al oxides are crucial in element precipitation. Moreover, groundwater redox conditions are a key factor for uranium precipitation in the lateritic profile. The findings provide insight into the potential of lateritic weathering as a natural mechanism for HFSE and REE concentration, contributing to the broader understanding of critical metal resources in Indonesia. These insights have implications for sustainable resource exploration and environmental management in areas with high natural radiation exposure.

Distribution and Mineralogical Characteristic of Raya Volcanics, West Kalimantan

Landslides are natural disasters that often occur in certain areas in Indonesia, which cause great damage to aspects of human life. To reduce or prevent major losses due to landslide disasters, previous research used the kind of study that is called Landslide Susceptibility Map (LSM). Meanwhile the purpose of this study is to compare 6 distance metrics on K-Nearest Neighbor (KNN) with distance weight. It is to find the optimal distance metric to create a landslide susceptibility map from the data which is located in the Kejajar sub-district, Wonosobo regency, Central Java, Indonesia, with 25 factors that cause landslides. Data processing is carried out using information gain as a feature selection which aims to reduce the factors that can cause landslide. The distance metrics that used in this study are: Euclidean, City Block, Chebyshev, Cosine, Hamming, and Jaccard. Every distance metrics were trained with the dataset and compare each performance model. The result is Chebyshev distance has a better performance than other distance metrics with precision 0.8289, recall 0.9763, f1-score 0.8966, and accuracy 0.9874.