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All Journal IJOG : Indonesian Journal on Geoscience Journal of Geoscience, Engineering, Environment, and Technology Buletin Sumber Daya Geologi Indonesian Journal on Geoscience Indonesian Journal on Geoscience Journal of Applied Geology Berita Sedimentologi Jurnal Geologi dan Sumberdaya Mineral (Journal of Geology and Mineral Resources)
Nugroho Imam Setiawan
Universitas Gadjah Mada
Chemistry Civil Engineering, Building, Construction & Architecture Earth & Planetary Sciences Education Energy Engineering Environmental Science Physics

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Numerical Analysis of Slope Stability Due to Excavation of Diversion Tunnel at Pamukkulu Dam Site, Indonesia Wakhid Khoiron Nugroho; I Gde Budi Indrawan, Dr.; Nugroho Imam Setiawan
Journal of Applied Geology Vol 6, No 2 (2021)
Publisher : Geological Engineering Department Universitas Gadjah Mada

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (7466.289 KB) | DOI: 10.22146/jag.57658

Abstract

Located in the Takalar Regency of South Sulawesi Province, the Pamukkulu Dam is planned to use a tunnel type as its diversion structure. One of the critical parts in the tunnel construction is the stability of portal slopes. This research aimed to estimate the effect of tunnel excavation on the stability of the portal inlet and outlet slopes under static and earthquake loads by using the finite element method. The slope stability analyses were carried out under conditions of prior to and after tunnel excavation. The input parameters used were laboratory test results in the forms of index properties and mechanical properties taken from rock core drilling samples, completed with the rock mass quality parameters based on the Geological Strength Index (GSI) classification. The Mohr-Coulomb failure criterion was used to model strength of the soil, while the Generalized Hoek-Brown failure criterion was used to model strength of the rocks. The results of rock cores analysis using the GSI method showed that the inlet tunnel slope consisted of four types of materials, namely residual soil, fair quality of basalt lava, good quality of basalt lava, and very good quality of basalt lava. Meanwhile, the outlet portal slope consisted of three types of materials, namely residual soil, good quality basalt lava, and very good quality basalt lava. The calculated horizontal seismic coefficient for the pseudo-static slope stability analysis was 0.0375. The analysis results of slope stability in the Y1 inlet section had a critical Strength Reduction Factor (SRF) value of 2.35 in a condition prior to the tunnel excavation and a critical SRF value of 2.34 after the tunnel excavation. The Y2 outlet section had a critical SRF value of 13.27 in a condition before tunnel excavation and a critical SRF value of 5.55 after the tunnel excavation. The earthquake load addition at the Y1 inlet section showed a critical SRF value of 2.05, both before and after the tunnel excavation. The Y2 outlet section showed a critical SRF value of 11.49 before the tunnel excavation and a critical SRF value of 5.54 after the tunnel excavation. The numerical analysis results showed that earthquake load reduced critical SRF values of the slopes. At the Y1 inlet section, the tunnel excavation did not have a significant effect on slope stability. It was demonstrated by an extremely small decrease in a critical SRF value of 0.43% for a condition without an earthquake load and an unchanged critical SRF in a condition with an earthquake load. At the Y2 outlet section, the tunnel excavation had a more significant effect on the slope stability. It was exhibited by the decrease in the critical SRF value of 58.18% in a condition without an earthquake load and a decrease in the critical SRF value of 51.78% in a condition with an addition of an earthquake load. However, the analysis of slope stability for both sections showed that all design slopes were above the required allowable safety factor value.
Petrography and Geochemistry of Metasedimentary Rocks from the Taku Schist in Kelantan, North-East Peninsular Malaysia. Muhammad Irman Khalif bin Ahmad Aminuddin; Nugroho Imam Setiawan; I Wayan Warmada; Kamar Shah Ariffin; Kotaro Yonezu
Journal of Applied Geology Vol 5, No 2 (2020)
Publisher : Geological Engineering Department Universitas Gadjah Mada

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (5089.195 KB) | DOI: 10.22146/jag.61183

Abstract

The Taku Schist, which is located in the north-east Peninsular Malaysia, is characterized by its North-South oriented elongated body. It forms part of the Indonesian orogenic build-up that was generated via the convergence of the Sibumasu continental unit and Sukhothai Arc. Subsequent petrography analyses of the metasedimentary rocks sourced from the Taku Schist revealed that their formation was attributable to the metamorphism of greenschist into amphibolite facies, which could be observed near the Triassic and Cretaceous intrusions of the Kemahang Granite. The evolutionary process of the rocks could be linked with the interactions occurring between contact and regional metamorphisms. The resulting chemical classification upon their assessment disclosed that the metasedimentary rocks of Taku Schist were made up of greywacke and shale, grouped into the quartzose sedimentary provenance, and belonged to the Continental Island Arc (CIA). This information is required for the tectonic setting discrimination purpose. It is a reflection of the episodic contractions underwent by the Taku Schist, wherein they would lead to the Sibumasu sedimentary cover along with both an accretionary wedge and the genetically-correlated Bentong-Raub melange to different greenschist. Otherwise associated with amphibolite facies, the conditions and depths of the facies were determined according to their position in relation to the upper plate of the Sukhothai Arc.
ALTERASI HIDROTERMAL ENDAPAN SINABAR DAERAH BUKIT TEMBAGA, IHA – LUHU, PULAU SERAM, MALUKU : HYDROTHERMAL ALTERATION OF CINNABAR DEPOSIT IN TEMBAGA HILL, IHA – LUHU - SERAM ISLAND, MALUKU Herfien Samalehu; Arifudin Idrus; Nugroho Imam Setiawan
Buletin Sumber Daya Geologi Vol. 17 No. 3 (2022): Buletin Sumber Daya Geologi
Publisher : Pusat Sumber Daya Mineral Batubara dan Panas Bumi

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.47599/bsdg.v17i3.357

Abstract

Iha – Luhu area is located in the western part of Seram Island, which is about 59.2 km from city of Piru. Geographically, it is located at 128o0’35” to 128o2’42”East Longitude and 3o20’40” s.d 3o22’05”South Latitude and is included in Huamual sub-district, West Seram Regency, Maluku. Stratigraphy of Iha – Luhu is composed of metapelitic rock and low grade metamorphic lithologies, namely meta quartz – muscovite sandstone units and quartz – muscovite phyllite unit and is unconformaby covered by alluvial deposits. Research area consists of three hydrothermal alteration zones which are mentioned as illite±kaolinite alteration zone, illite±chlorite alteration zone and Illit±smectite±kaolinite alteration zone. Illite±kaolinite alteration zone is characterized by assemblage of clay minerals, presumably illite and kaolinite. This alteration is associated with quartz-muscovite meta-siltstone and dominant occurred to quartz-muscovite meta-sandstone. Intensity of alteration is moderate to strong altered which mainly describing percentage of alteration mineral presence more than 75%. Based on assemblage of kaolinite and illite alteration minerals thus illite±kaolinite alteration zone was formed at temperatures <220o-300o C. Illite±chlorite alteration zone is associated with fracture-related mineralization and disseminated enrichment of cinnabar ore deposits where alteration pattern is a pervasive alteration show. This zone is characterized by presence of mica (illite) clay mineral and chlorite and quartz as well. Illite±chlorite alteration is more dominantly associated with quartz-muscovite phyllite and quartz-muscovite meta-siltstone and spread over in the middle of Bukit Tembaga. Formation Temperature of this alteration zone is estimated at 250o – 300o C. Illite±smectite±kaolinite alteration zone spread widely on top of Bukit Tembaga to lowlands and reaching area of ​​> 9.6 Km2. This alteration covers illite ± chlorite and illite ± kaolinite alterations with pervasive alteration pattern and strong altered alteration. Clay in this zone occurred due to alteration of muscovite/sericite and plagioclase minerals. Presence of smectite in this alteration zone reflects vertical depth that is relatively far from ore zone or at top of formation with temperature tend to be lower than illite and kaolinite minerals. Formation temperature of this alteration zone is estimated at 220o-300o C.
Late Triassic Metatonalite from the Schwaner Mountains in West Kalimantan and Its Contribution to Sedimentary Provenance in the Sundaland Nugroho Imam Setiawan; Yasuhito Osanai; Nobuhiko Nakano; Tatsuro Adachi; Lucas Donny Setiadji; Joko Wahyudiono
Berita Sedimentologi Vol 28, No 1 (2013)
Publisher : Ikatan Ahli Geologi Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (2491.878 KB) | DOI: 10.51835/bsed.2013.28.1.150

Abstract

This contribution presents petrography, geochemical characteristicc and LA-ICP-MS U-Pb zircon dating from metatonalites in the Schwaner Mountains of West Kalimantan. The metatonalites mainly consist of plagioclase, biotite, quartz, apatite, muscovite, and titanite with relict clinopyroxene surrounded by hornblende. The geochemical characteristics show that the rocks have calc-alkaline affinities and were derived from subduction-related arc tectonic environment. Some of the metatonalites have adakite signature, which suggests the Schwaner Mountains were not formed by a consecutive subduction system. The result of LA-ICP-MS U-Pb zircon dating reveals that the metatonalite has magmatic age at 233 ± 3 Ma (Late Triassic), which is the oldest magmatic age in the Schwaner Mountains. Therefore, it strongly suggests that the Schwaner Mountains has significantly potential for important sedimentary sources in Sundaland not only from Cretaceous age but also from Triassic age as well as Tin Belt granites from Malay Peninsula.
Cooling history (from magma ascent to lava extrusion) of the Watuadeg pillow lava, Berbah, Yogyakarta, Indonesia Indranova Suhendro; Agung Harijoko; Nugroho Imam Setiawan; Haryo Edi Wibowo
Journal of Applied Geology Vol 8, No 1 (2023)
Publisher : Geological Engineering Department Universitas Gadjah Mada

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.22146/jag.73942

Abstract

The Watuadeg pillow lava (WPL) is known as one of the most famous pillow lava outcrops in Yogyakarta, Indonesia, and its origin has been attributed to rapid-cooling process of subaqueous lava extrusion. However, there is no quantitative evidence that implies such hypotheses. Therefore, this study aims to reduce such a gap by revealing the cooling times (t) of WPL on the basis of a quantitative approach. In particular, we measured the size distribution (CSD) and number density (MND) of plagioclase microlites from the core, medial, and marginal (rim) domains of WPL. We found that the CSD slope significantly increases towards marginal zones, namely 30.4ᵒ for the core, 53.4ᵒ for the medial, and 228.1ᵒ for the rim. Because CSD slope is inversely proportional to cooling time ( ), by assuming a typical plagioclase microlite growth rate (G) of 1×107 mm/s, it is therefore inferred that the rim experienced the fastest cooling time (±12.1 hours), followed by the medial and core ((±52.0 and 91.4 hours, respectively). The fact that MNDs value increases toward the marginal zones also does not deny this idea (0.3×1016 m-3 for the core, 1.4×1016 m-3 for the medial, and 2.4×1016 m-3 for the rim), as higher MND with the domination of acicular-spherulitic habit represents a higher degree of undercooling. Because microlite is syn-eruptive product, our estimation represents the cooling time of magma since it migrated from the reservoir to the surface.
KARAKTERISTIK MINERALISASI CEBAKAN AU±LOGAM DASAR DI TAMILOUW – HAYA, PULAU SERAM, MALUKU: MINERALIZATION CHARACTERISTIC OF AU±BASE METAL DEPOSIT AT TAMILOUW - HAYA, SERAM ISLAND, MALUKU Herfien Samalehu; Arifudin Idrus; Nugroho Imam Setiawan
Buletin Sumber Daya Geologi Vol. 18 No. 1 (2023): Buletin Sumber Daya Geologi
Publisher : Pusat Sumber Daya Mineral Batubara dan Panas Bumi

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.47599/bsdg.v18i1.400

Abstract

The research area is located in the southern part of Seram Island, Maluku, which is at an elevation of 3 to 675 meters above sea level; is composed of metapelites to low-grade metamorphic rocks, coralline limestone and alluvial deposits. The purpose of this investigation is to study geological control, mineralization characteristics and ore geochemistry of Au±basemetal deposit in Tamilouw – Haya. Investigation activities began with literature review, field investigations for sampling, geological mapping, alteration & mineralization and laboratory analysis which including polish sections and ore geochemistry (FA/AAS). Based on the results of investigation, it shows that mineralization in Tamilouw - Haya is associated with 3 type of veins, namely quartz veins (V1) that parallel to the foliation plane (concordant), quartz veins that cutting through foliation plane (V2) and third generation veins (V3) are quartz ±carbonate veins associated with breccia - stockwork and formed at the end of veins formation. Massive texture is found in most of the veins, especially those with relatively large dimensions. Vein filling minerals are dominated by quartz, sulfide minerals and precious metals while dominant sulfide veins consist of pyrite and arsenopyrite. Metal sulfide mineralizations at Tamilouw – Haya are pyrite, gold, chalcopyrite, sphalerite, galena, pyrhotite, tetrahydrite, tenantite, marcasite, arsenopyrite, sinabar, kalininite and realgar. Gold grades reaching 0.006 to 7.45 ppm.
Studi Fluida Pembawa Bijih Endapan Sinabar di Bukit Tembaga, Iha Luhu, Pulau Seram- Maluku Herfien Samalehu; Arifudin Idrus; Nugroho Imam Setiawan
Jurnal Geologi dan Sumberdaya Mineral Vol. 24 No. 4 (2023): JURNAL GEOLOGI DAN SUMBERDAYA MINERAL
Publisher : Pusat Survei Geologi

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.33332/jgsm.geologi.v24i4.727

Abstract

Lokasi penyelidikan terletak dibagian barat Pulau Seram dan tersusun oleh batuan metapelitik dan batuan metamorf berderajat rendah. Latar belakang dilakukannya penyelidikan ini disebabkan oleh masih minimnya studi mengenai karakteristik sifat kimia-fisik fluida hidrotermal pembentuk bijih endapan sinabar yang berasosiasi dengan batuan metamorf di Pulau Seram. Sejarah tekanan - temperatur selama proses mineralisasi oleh inklusi fluida menyiratkan asal fluida sumber bijih serta evolusinya selama mineralisasi. Metode penyelidikan menggunakan pemetaan geologi (fieldwork) yang dipadukan dengan mikrotermometri inklusi fluida. Lebih dari 61 inklusi fluida diukur untuk mendapatkan data mikrotermometrik menggunakan alat Linkam THMSG 600 freezing and heating stages. Inklusi fluida primer dari 2 tipe endapan sinabar yang berbeda di Iha – Luhu mengkristal pada temperatur homogenisasi (Th) 261 s.d 336°C dengan salinitas fluida dari 0,70 s.d 4.65% berat NaCl.ek serta temperatur leleh (Tm) sebesar -0,4 s.d -2,4°C. Fluida pembentuk bijih terdiri dari inklusi dua fase (VCO2 + LH2O) yang kaya akan cairan ditandai dengan kandungan CO2 yang rendah hingga tinggi serta bersalinitas rendah dan temperatur sedang. Terdapat 3 jenis urat kuarsa yang mewakili 2 tipe endapan sinabar di Iha – Luhu. Urat kuarsa tipe 1 (V1), konkordan dan merupakan endapan sinabar disseminated yang terbentuk pada suhu 264 s.d 307°C dengan salinitas 1,22 s.d 2,57 wt.% NaCl ek. Urat kuarsa tipe 2 (V2), diskordan, berasosiasi dengan endapan metasinabar serta terbentuk pada temperatur berkisar 293 s.d 331°C dan salinitas menunjukkan nilai 2.67 s.d 4.65 wt.% NaCl ek. Sedangkan urat tipe 3 adalah urat kuarsa (V3) yang berasosiasi dengan sinabar yang memotong foliasi batuan yang terbentuk pada temperatur 261-336°C dan salinitas 0,70 s.d 2,90 wt.% NaCl ek. Kata kunci: Sinabar, inklusi fluida, mikrotermometri, Ore-forming fluid, temperatur.
Co-Authors Adachi, Tatsuro Adachi, Tatsuro Agung Harijoko Agus Hendratno Ahmad Aminuddin, Muhammad Irman Khalif bin Amril Asy’ari, Amril Amril Asy’ari Ansori, Chusni Ariffin, Kamar Shah Arifudin Idrus Arifudin Idrus Asy’ari, Amril Chusni Ansori Chusni Ansori Haryo Edi Wibowo Herfien Samalehu Herfien Samalehu Herry Yogaswara I Gde Budi Indrawan I Wayan Warmada Indranova Suhendro Joko Wahyudiono Kamar Shah Ariffin Kotaro Yonezu Lucas Donny Setiadji Muhammad Irman Khalif bin Ahmad Aminuddin Nakano, Nobuhiko Nakano, Nobuhiko Nobuhiko Nakano Nobuhiko Nakano Nobuhiko Nakano Nobuhiko Nakano Nobuhiko Nakano, Nobuhiko Osanai, Yasuhito Osanai, Yasuhito Tatsuro Adachi Tatsuro Adachi Tatsuro Adachi Tatsuro Adachi Tatsuro Adachi, Tatsuro Wahyu Sasongko Wakhid Khoiron Nugroho Yasuhito Osanai Yasuhito Osanai Yasuhito Osanai Yasuhito Osanai Yasuhito Osanai, Yasuhito Yonezu, Kotaro