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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
Heri Syaeful
Pusat Pengembangan Geologi Nuklir – BATAN Jl. Lebak Bulus Raya No.9 Pasar Jumat, Jakarta Selatan
Chemical Engineering, Chemistry & Bioengineering Earth & Planetary Sciences Energy Engineering Materials Science & Nanotechnology Social Sciences

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Review on Granitic Rocks in Sumatra: Intrusion Process, Classification, Mineralization, and Potential Uses Irzon, Ronaldo; Syaeful, Heri; Kusworo, Aries; Wahyudiono, Joko; Ngadenin
EKSPLORIUM Vol. 43 No. 1 (2022): MAY 2022
Publisher : BRIN Publishing

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17146/eksplorium.2022.43.1.6471

Abstract

Granitic rocks are widely distributed in Sumatra and surrounding areas. These granitoids are classified into several granite provinces of Southeast Asia with different intrusion processes and specific characteristics. This paper aims to review the intrusion of granitic rocks in Sumatra and describe the opportunities associated with it. Granite rocks are used to manufacture cultural heritage, works of art, and ornaments because of their weathering resistance, color diversity, and hardness characters. S-type granite intrusion in Sumatra might be associated with tin mineralization while silver-gold with the I-type. Theoretically, granite contains more REE than other igneous rocks. Mining and extraction difficulties complicate the direct REE exploitation from fresh granite. A-type granite relatively contains more REE than the other types, but this type of granite is not correlated with certain provinces. Indonesia has a tropical climate which is prone to weathering. Therefore, it is possible for REE and/or bauxite enrichments in the granite weathering horizon. Granite is assumed to be a potential source of uranium and thorium, especially for the S-type, because it is formed through the compression of sediments that can absorb these radioactive elements from the continental crust.
Geostatistical Ore Body Modeling on Uranium Mineralization in Remaja Sector, Kalan Area, West Kalimantan Ciputra, Roni Cahya; Heriawan, Mohamad Nur; Syaeful, Heri; Kamajati, Dhatu; Rahmawati, Putri
EKSPLORIUM Vol. 43 No. 1 (2022): MAY 2022
Publisher : BRIN Publishing

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17146/eksplorium.2022.43.1.6622

Abstract

Manual ore body modeling on Remaja Sector, Kalan, West Kalimantan generally takes a long time and is subjective. On the other hand, automatic modeling (implicit modeling) is faster, objective, and equipped with uncertainty factors. This study aimed to analyze the comparison between the geostatistical Sequential Indicator Simulation (SIS) ore body model to the manual ore body model. The lithology database was used as input for variogram analysis and SIS simulation. The directional variogram was used to construct an experimental variogram for the lithology with orientation data. The orientation of the lithologies corresponds to the anisotropy of their variogram map. The SIS was carried out in Block A and Block B with block sizes of 6×6×6 m3 and 5×5×5 m3 respectively. The simulation results were processed to produce a lithology probability model. By using maximum probability as block lithology, simulation results were well validated by the composite database histogram, the lithologies along the tunnel on the geological map of level 450 masl of Eko Remaja Tunnel., and the lithologies along boreholes. The weakness of the geostatistical ore body model was the results depending on the input parameters. Meanwhile, several advantages of the geostatistical ore body model were a faster processing process, equipped with an uncertainty factor, and the block size of the model has taken into account the distance between grade data so that it can be used directly for grade estimation. Quantitatively, the geostatistical ore body model had a higher average percentage of conformity to the lithology of the mineralized zone along the borehole than the manual ore body model
Distribution and Characteristics of Rare Earth Elements in Uranium-Ore Deposits from Rirang Area, West Kalimantan Province, Indonesia Adimedha, Tyto Baskara; Farenzo, Rayhan Aldizan; Sukadana, I Gde; Nugraheni, Rosmalia Dita; Pratiwi, Fadiah; Ciputra, Roni Cahya; Indrastomo, Frederikus Dian; Syaeful, Heri; Rachael, Yoshi
EKSPLORIUM Vol. 45 No. 1 (2024): MAY 2024
Publisher : BRIN Publishing

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.55981/eksplorium.2024.7058

Abstract

Uranium and rare earth elements (REE) are essential elements for the development of green environmentally friendly, and sustainable energy. To meet the increasing demand for these raw materials, Indonesia has taken steps to explore and map potential deposits, including the Rirang Sector in Melawi Regency, West Kalimantan. However, the available information on the mineralization of these elements in the area is limited. Therefore, this study aimed to provide a detailed characterization on the petrology and geochemical characteristics of uranium ore and to synthesize the mineral genesis of uranium and REE-bearing ore in the Rirang Sector. The analytical methods used included petrography, micro-XRF, and geochemical analysis. The results showed that uranium mineralization was present in brannerites, uranophane, and swamboite associated with tourmaline and monazite ore. Similarly, REE concentrations were hosted by REE-bearing minerals, such as monazite, xenotime, and loparite. Geochemically, the uranium concentration in the monazite ore ranged from 1,110 – 28,440 ppm, while the total REE (TREE) concentration varied between 85,320 to 138,488 ppm. The formation of uranium and REE mineralization were due to the metasomatism process and its association with the Na-rich fluid of felsic intrusion. Notably, the weathering process did not enrich uranium and REE content in the soil but rather decreased it due to the leaching process and the absence of clay minerals capable of absorbing the REE cations on the surface of clay crystal structures.
Magmatic Evolution of Dago Volcano, West Java, Indonesia Adimedha, Tyto Baskara; Harijoko, Agung; Handini, Esti; Sukadana, I Gde; Syaeful, Heri; Ciputra, Roni Cahya; Rosianna, Ilsa; Indrastomo, Frederikus Dian; Pratiwi, Fadiah; Rachael, Yoshi
EKSPLORIUM Vol. 44 No. 1 (2023): MAY 2023
Publisher : BRIN Publishing

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.55981/eksplorium.2023.6873

Abstract

Dago Volcano is a product of Miocene Sunda Arc volcanism located southeast of the capital city of Jakarta. The morphological change from flat lava flow to steeper lava morphology implies a process of magma evolution under Dago Volcano. This research provides an overview of the magma evolution that occurs on this volcano. The methods used include volcanostratigraphic analysis, petrographic analysis, mineral chemistry, and whole-rock geochemistry. The volcanostratigraphy of Dago Volcano is composed of two eruption centers and a flank eruption forming lava and cinder cones products. The mineralogical associations of Dago Volcano products include plagioclase, olivine, and clinopyroxene. The mineral textures of Dago edifices show zoning, sieve, and reaction rims textures. Geochemically, the Dago Volcano product has a magma affinity of med-K calc-alkaline with quite high levels of MgO, Ni, and Cr approaching the characteristics of primitive magma. The magma evolution process of Dago Volcano includes fractional crystallization and magma mixing which originates from the same magma source.
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 Adhika Junara Karunianto Adi Gunawan Muhammad Adimedha, Tyto Baskara Agung Harijoko Arie Naftali Hawu Hede Aries Kusworo Ciputra, Roni Cahya Damaledo, Ebenheser Dhatu Kamajati, Dhatu Dwi Haryanto Esti Handini Farenzo, Rayhan Aldizan Firdaus, Muhammad Anugrah Frederikus Dian Indrastomo, Frederikus Dian Heriawan, Mohamad Nur Hery Prabowo I Gde Sukadana Ichwan Azwardi Lubis Imam Achmad Sadisun Joko Wahyudiono Kurnia Setiawan Widana Lilik Subiantoro Mardania, Faneza Nur Maulana, Muhammad Wira Mirna Berliana Garwan, Mirna Berliana Muhammad Nurdin Ngadenin Ngadenin Ngadenin Nugraheni, Rosmalia Dita Prasetyo, Gagah Hari Pratiwi, Fadiah Putra, Aldo Febriansyah Putri Rahmawati Rachael, Yoshi Ronaldo Irzon Rosianna, Ilsa Sucipta Sucipta Suharji Suharji Suharji Sukmawan, I Gusti Made syafrizal Yogi La Ode Prianata