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All Journal IJOG : Indonesian Journal on Geoscience Eksplorium : Buletin Pusat Pengembangan Bahan Galian Nuklir Eksplorium : Buletin Pusat Pengembangan Bahan Galian Nuklir
Rachael, Yoshi
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Chemical Engineering, Chemistry & Bioengineering Earth & Planetary Sciences Energy Engineering Materials Science & Nanotechnology Social Sciences

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Radioactive Mineral Distribution on Tin Placer Deposits of Southeast Asia Tin Belt Granite in Bangka Island Ngadenin, Ngadenin; Sukadana, I Gde; Muhammad, Adi Gunawan; Indrastomo, Frederikus Dian; Rosianna, Ilsa; Ciputra, Roni Cahya; Adimedha, Tyto Baskara; Pratiwi, Fadiah; Rachael, Yoshi
EKSPLORIUM Vol. 44 No. 2 (2023): NOVEMBER 2023
Publisher : BRIN Publishing

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.55981/eksplorium.2023.6969

Abstract

Bangka Island is an area rich in primary and secondary tin deposits. Tin deposits are formed around the contact between granite and older rocks, while secondary tin deposits are formed in the modern channels and paleochannels. Many previous researchers have researched radioactive minerals in primary tin deposits and modern channel deposits, but research on radioactive minerals in paleo channel deposits has never been carried out. The characterization of radioactive minerals in paleo channel deposits was done in this study to determine the potency of radioactive minerals in secondary tin deposits by comparing the content of radioactive minerals in paleochannels with modern channels and tin mine tailing deposits. The data used were mineralogical data and radioactivity data, along with the uranium and thorium content of the rocks from several previous studies. Data showed significant mineral content differences in paleo channel, modern channel, and tin mine tailings deposits. Mineral (monazite and zircon) content in tin mine tailing deposits was the highest. Source rocks for the radioactive minerals monazite and zircon are predicted to be the granitic rocks or tourmaline quartz veins of primary tin deposits. The radioactivity value of rocks in the paleo channel is relatively the same as the modern channel, ranging from 20 to 150 c/s. Uranium content in paleo channel is the same as modern channel deposits, ranging from 10 to 15 ppm eU. The thorium content of the rocks in the paleo channel ranges from 1 to 60 ppm eTh, while in the modern channel, it ranges from 1 to 45 ppm eTh. The radioactivity value and uranium content of the rocks are less effective for determining potential areas of radioactive minerals in placer tin deposits. In contrast, data on thorium content are quite effective for determining potential areas of radioactive minerals in placer tin deposits.
Characteristics and Genesis of Mount Pengki: A Scoria Cone of Dago Volcano, West Java, Indonesia Adimedha, Tyto Baskara; Ciputra, Roni Cahya; Rosianna, Ilsa; Sukadana, I Gde; Harijoko, Agung; Handini, Esti; Pratiwi, Fadiah; Indrastomo, Frederikus Dian; Syaeful, Heri; Rachael, Yoshi; Sukmawan, I Gusti Made
EKSPLORIUM Vol. 45 No. 2 (2024): NOVEMBER 2024
Publisher : BRIN Publishing

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.55981/eksplorium.2024.7131

Abstract

Scoria cones are a typical product of volcanic activity constructed by the bomb and lapilli-sized pyroclasts formed by Strombolian eruption. Mount Pengki is a scoria cone found in Miocene Dago Volcano, West Java. Mount Pengki was a remnant of a Miocene volcano that was exceptionally well preserved and exposed. This scoria cone contains layers of scoria beds and a lava flow unit. The study aims to characterize the exposed scoria bed deposits and investigate the eruptive history and degradation process of Mount Pengki. Field observation, including measured sections and detailed characterizations of the Mount Pengki quarry, allows us to observe its volcanic sequence from its internal structure toward the surface. Morphometric analysis of Mount Pengki can describe the degradation process undergone by the scoria cone. The early phase deposits were characterized by massive to weakly bedded, poorly sorted, clast-supported beds mainly composed of coarse lapilli to bombs/blocks scoria grain. The middle phase deposit typically shows well-stratified, well-sorted, clast-supported scoria beds with coarse ash to coarse lapilli grain size. The late phase deposit is similar to the middle phase deposit, with additional features of coarser-grain, reverse grading, and clast-supported lenticular beds. Eruptive mechanisms involved in the formation of Mount Pengki include ballistic transport of clasts, fallout deposition, and grain avalanching process. The degradation process was likely influenced by prolonged exposure to weathering, cone rim collapse, and regional deformation processes.
Lithological Discrimination Based on Radiometric Data: Case Study of Rabau Sector, West Kalimantan and Salumati Sector, West Sulawesi Maulana, Muhammad Wira; Ciputra, Roni Cahya; Iskandarsyah, Iskandarsyah; Adimedha, Tyto Baskara; Sukadana, I Gde; Indrastomo, Frederikus Dian; Syaeful, Heri; Pratiwi, Fadiah; Rachael, Yoshi; Mardania, Faneza Nur; Kamajati, Dhatu; Rahmawati, Putri; Garwan, Mirna Berliana
EKSPLORIUM Vol. 46 No. 1 (2025): MAY 2025
Publisher : BRIN Publishing

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.55981/eksplorium.2025.11475

Abstract

This study evaluates the applicability of radiometric methods for lithological discrimination in tropical environments, with a focus on two uranium exploration sites in Indonesia: the Rabau Sector in West Kalimantan and the Salumati Sector in West Sulawesi. These locations were selected to represent various lithologies within the uranium exploration program. The aim is to determine whether gamma-ray spectrometry, commonly effective in arid environments, can also delineate lithological boundaries and alteration zones under conditions of intense weathering and dense vegetation cover of tropical area. Ground-based radiometric data were collected using the RS-125 gamma spectrometer to record the concentration of potassium (K), equivalent uranium (eU), and equivalent thorium (eTh). Data processing involved anisotropy analysis, geostatistical interpolation using ordinary kriging, ternary RGB composite mapping, and delineation of radiometric domains. The resulting radiometric maps were then qualitatively compared with existing geological maps for validation. The results show that radiometric signatures, particularly eTh and eU, can effectively distinguish rock units with differing genesis or degrees of alteration, despite tropical conditions. In Rabau, where lithologies share a common protolith, elevated eU concentrations correspond to hornfels, while metatuff and metasiltstone remain indistinguishable, indicating the influence of thermal metamorphism on radiometric responses. In Salumati, eTh and eU zoning within phonolite suggest compositional variability or differential alteration, and elevated eU in altered tuff reflects uranium remobilization in smectite-rich zones. These findings demonstrate that, despite the challenges posed by tropical climates, radiometric mapping remains a viable tool for lithological discrimination and early-stage uranium exploration in Indonesia. This work extends the application of radiometric techniques beyond arid environments and underscores the need to integrate radiometric interpretation with genetic, provenance, and alteration context in tropical geological mapping.
Co-Authors . Iskandarsyah Adi Gunawan Muhammad Adimedha, Tyto Baskara Agung Harijoko Ciputra, Roni Cahya Damaledo, Ebenheser Dhatu Kamajati, Dhatu Dwi Haryanto Esti Handini Farenzo, Rayhan Aldizan Fauzi, Rachman Frederikus Dian Indrastomo, Frederikus Dian Heri Syaeful I Gde Sukadana Mardania, Faneza Nur Maulana, Muhammad Wira Mirna Berliana Garwan, Mirna Berliana Ngadenin Ngadenin Nugraheni, Rosmalia Dita Nunik Madyaningarum, Nunik Prasetyo, Gagah Hari Pratiwi, Fadiah Putra, Aldo Febriansyah Putri Rahmawati Rosianna, Ilsa Sukmawan, I Gusti Made Widodo Widodo Widodo