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Depositional Environment of the Sangkarewang Oil Shale, Ombilin Basin, Indonesia Komang Anggayana; Agus Haris Widayat; Sri Widodo
Journal of Engineering and Technological Sciences Vol. 46 No. 4 (2014)
Publisher : Institute for Research and Community Services, Institut Teknologi Bandung

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/j.eng.technol.sci.2014.46.4.6

Five samples from 56 m long drill core of lacustrine Sangkarewang oil shale have been studied by means of petrography and organic geochemistry to investigate the organic matter composition and depositional environments of the shale. The organic matter consists of abundant lamalginite (30%, v/v) and very limited amount of vitrinite, suggesting aquatic depositional environments with minor terrestrial influence. Organic geochemical analysis exhibits the dominance of pristane, phytane, and generally n-alkanes compounds. These compounds might originate mostly from aquatic photosynthetic organisms. The oil shale was likely deposited in anoxic lake environments, suggested by the presence of framboidal pyrite (6%, v/v) and preserved organic matter with total organic carbon (TOC) about 4.9%. The pristane/phytane ratio is relatively high about 3.9 and thought as source sensitive rather than redox sensitive. Hopanoid and aryl isoprenoid compounds are present in minor amounts. The latter compounds are interpreted to be derived from green sulfur bacteria dwelling in anoxic and the presence of H2S in bottom water.

Depositional Cycles of Muara Wahau Coals, Kutai Basin, East Kalimantan Komang Anggayana; Basuki Rahmad; Agus Haris Widayat
Indonesian Journal on Geoscience Vol 1, No 2 (2014)
Publisher : Geological Agency

http://dx.doi.org/10.17014/ijog.v1i2.183Fifteen samples were taken ply by ply from a 33 m thick drill core of Muara Wahau coal seams for interpretation of depositional environments. Generally, lithotype variation in the bottom part of the coal seams has a lower frequency than in the upper part. Petrographical analysis was performed to determine the maceral composition, groundwater index (GWI), and gelification index (GI). The samples from lower sections show much higher GWI-GI values and lower variation frequency than from the upper section. This characteristic is interpreted as the result of development of mesotrophic to ombrotrophic peats during the deposition of lower to upper parts of the section, respectively. During the development of the mesotrophic peat, water was more abundant and relatively stable in budget. However, during the development of ombrotrophic peat, water was less abundant and relatively not stable in budget. The latter is related to the water supply depending only on rain, resulted in the more sensitive water table in the om- brotrophic peat. The unstable water table is thought as the reason of higher variation frequency of lithotype, GWI, GI, as well as maceral composition in the upper part of the core. Unstable water table would lead to moist condition in the uppermost layer of the ombrotrophic peat, favoring fungi to grow. This is confirmed by the higher abundance of sclerotinite maceral in samples from the upper part of the coal core.

Precipitation of Calcite during the Deposition of Paleogene Sangkarewang Oil Shale, Ombilin Basin, West Sumatra, Indonesia Agus Haris Widayat; Komang Anggayana; Isra Khoiri
Indonesian Journal on Geoscience Vol 2, No 3 (2015)
Publisher : Geological Agency

DOI: 10.17014/ijog.2.3.185-197Geochemical and petrographical analyses were carried out to investigate the occurrence of calcite in theformer Ombilin lacustrine lake. The study involves eight samples taken from a 56 m long drill core of Sangkarewangoil shale. Geochemical investigation showed that the samples consist of varied terrigenous input represented by Si, Al, K, and Ti, and autochthonous input represented by S, total organic carbon (TOC), and d13C of bulk organic matter. Along the drill core profile the abundance of autochthonous input decreases upwards, while that of terrigenous input oppositely increases upwards. Petrographical analysis revealed that calcite is a major mineral in the samples. In this study, the abundance of calcite could be represented by the abundance of Ca, as calcite is the only significant Ca containing mineral. Ca is abundant in the samples (8.4% in average) and its concentration varies similarly with those of S, TOC, and d13C, suggesting that the element as well as calcite incorporates the autochthonous input. Thevariation of calcite abundance in the drill core profile is considered to be related with primary productivity changes during the development of the former lake. Higher primary productivity represented by more positive of d13C value(-24.8‰) during the deposition of the lower part of the drill core profile promoted the higher amount of deposited organic matter. In such environment, the supersaturation of carbonate ion in lake water was also reached and significant precipitation of authigenic calcite occurred. As the lake developed, the primary productivity decreased as indicated by more negative of d13C value (eventually -26.8‰). This condition led to the decreases of deposited organic matterand calcite in the lake sediments.

The Occurrence and Genesis of Silicified Coals in Tanjung Redeb, Embalut, and Loa Kulu, East Kalimantan, Indonesia Agus Haris Widayat; Komang Anggayana; Teti Indriati; Andy Yahya Al Hakim; Mulyono Dwiantoro; Miqdam Furqany; Mirza Dian Rifaldi
Indonesian Journal on Geoscience Vol 9, No 1 (2022)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.9.1.27-43

DOI:10.17014/ijog.9.1.27-43The occurrence and genesis of silicified coals in Tanjung Redeb, Embalut, and Loa Kulu have been described and reconstructed by means of petrography and geochemistry. The silicified coals are black, hard, and contain dispersed fine-grained silica minerals. Silica (SiO2) contents vary from 58 to 76%, and LOI (mostly represents organic matter) ranges from 23 to 40% of the bulk silicified coal samples based on the ICP-INAA analysis. Microscopic examination shows the presence of quartz, chalcedony, and amorphous opal. Silicification occurs both as layers and nodules within the coal seams. The layer type is usually thin layers (<25 cm) near the top and bottom of the seams, and they can spread horizontally up to 3 m. Nodules occur randomly in the coal seams having a diameter from several centimeters to 1 m. Further microscopic investigation shows that preserved cellular structure is more commonly observed in the layered silicified coal samples. This may suggest that the layered silicification occurred relatively early in the coal seam diagenesis, while the nodule silicification took place during later diagenesis. The coexistence of silica polymorphs in some samples may indicate the presence of multiple silicification stages during coalification.

The Occurrence and Genesis of Silicified Coals in Tanjung Redeb, Embalut, and Loa Kulu, East Kalimantan, Indonesia Agus Haris Widayat; Komang Anggayana; Teti Indriati; Andy Yahya Al Hakim; Mulyono Dwiantoro; Miqdam Furqany; Mirza Dian Rifaldi
Indonesian Journal on Geoscience Vol. 9 No. 1 (2022)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.9.1.27-43

DOI:10.17014/ijog.9.1.27-43The occurrence and genesis of silicified coals in Tanjung Redeb, Embalut, and Loa Kulu have been described and reconstructed by means of petrography and geochemistry. The silicified coals are black, hard, and contain dispersed fine-grained silica minerals. Silica (SiO2) contents vary from 58 to 76%, and LOI (mostly represents organic matter) ranges from 23 to 40% of the bulk silicified coal samples based on the ICP-INAA analysis. Microscopic examination shows the presence of quartz, chalcedony, and amorphous opal. Silicification occurs both as layers and nodules within the coal seams. The layer type is usually thin layers (<25 cm) near the top and bottom of the seams, and they can spread horizontally up to 3 m. Nodules occur randomly in the coal seams having a diameter from several centimeters to 1 m. Further microscopic investigation shows that preserved cellular structure is more commonly observed in the layered silicified coal samples. This may suggest that the layered silicification occurred relatively early in the coal seam diagenesis, while the nodule silicification took place during later diagenesis. The coexistence of silica polymorphs in some samples may indicate the presence of multiple silicification stages during coalification.

Mineralogi dan Mobilitas Unsur pada Lithium dan Logam Tanah Jarang pada Lumpur Sidoarjo (Lusi), Indonesia Hakim, Andy Yahya Al; Anggayana, Komang; Indriati, Teti; Sulistijo, Budi; Syafrizal, Syafrizal; Heriawan, Mohamad Nur; Widayat, Agus Haris
Geosapta Vol 8, No 2 (2022): JULI 2022
Publisher : Universitas Lambung Mangkurat

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.20527/jg.v8i2.13936

Lumpur Sidoarjo (Lusi) merupakan manivestasi gunung lumpur (mud volcano) yang mengeluarkan erupsi sejak Mei 2006 hingga saat ini. Kegiatan penelitian dengan fokus elemen tanah jarang pada Lusi menjadi perhatian karena volume lumpur yang terus bertambah, serta potensi logam yang bernilai ekonomis. Studi ini bertujuan untuk mengetahui mineralogi Lusi berdasarkan studi mikroskopi optik dan elektron, serta konfirmasi dari geokimia untuk memahami kelimpahan unsur. Sampel didominasi seperti kuarsa, Ca-feldspar, mineral filosilikat seperti muskovit. Kaolinit teramati pada semua sampel, merupakan mineral lempung yang dapat menangkap elemen tanah jarang (rare-earth element) melalui mekanisme adsorpsi dan substitusi ion. Analisa geokimia menunjukkan kelimpahan unsur lithium pada Lusi mengalami pengayaan sebanyak 3 hingga 5 kali jika dibandingkan dengan kelimpahan unsur di kerak bumi. Terdapat korelasi unsur yang kuat antara unsur lithium (r>0,8) dengan Sr, Rb, Be, K, Cs, diduga terkayakan pada mineral silikat dengan struktur berlapis seperti kaolinit dan muskovit. Unsur light rare-earth elements menunjukkan kelimpahan yang lebih tinggi dengan heavy rare-earth elements. Lithium merupakan unsur yang menarik untuk dieksplorasi lebih lanjut karena mengalami pengayaan dan kemungkinan berikatan membentuk garam klorida atau mineral lain. Logam tanah jarang, walaupun mengalami pengayaan, dengan kondisi ilmu pengetahuan saat ini bukan merupakan target utama untuk kegiatan eksplorasi lanjutan.

Estimating Groundwater Inflow to The Underground Mine Works using a 3D Groundwater Model at Vein Kubang Cicau, UBPE Pongkor Naiborhu, Kory Yohana Adinda; Anggayana, Komang; Widodo, Lilik Eko; Wibowo, Aryo Prawoto
Indonesian Journal on Geoscience Vol. 11 No. 3 (2024)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.11.3.423-435

Estimating groundwater inflow to underground mines is essential for ensuring that mining activities can be conducted safely and continuously. Research conducted at UBPE Pongkor indicates that the veins have the fault connectivity with the Kubang Cicau vein showing potential for deeper mining, while other veins are expected to become exhausted. As the result, the Kubang Cicau vein will likely be at a lower elevation in the future. Planning decisions regarding groundwater control measures, such as dewatering, can be made in advance, contributing to a more efficient assessment of the economic feasibility of mining development. Groundwater modeling using MODFLOW software predicted a maximum groundwater discharge of 55 L/s. To address the model uncertainty, a sensitivity analysis was performed by increasing the hydraulic conductivity parameter by two order of magnitude, as this value significantly affects groundwater inflow. Conversely, decreasing the hydraulic conductivity by two order resulted in a new discharge estimate of 87 L/s. In the worst-case scenario, with the highest specific storage values, the inflow increased to 76 L/s. This demonstrates that although changes in specific storage have a notable effect on groundwater inflows, the impact is less pronounced compared to the changes in hydraulic conductivity. Nonetheless, Ss remains a key parameter, particularly in transient simulations where storage plays a more significant role in the system response to changes in water levels.

EVALUASI SUMBER DAYA PASIR KUARSA BERDASARKAN DATA PEMBORAN DAN SURVEI GPR PADA MATERIAL SISA HASIL PENGOLAHAN TIMAH ALUVIAL DI KEPULAUAN BANGKA DAN BELITUNG Safitra, Roby Mardiyan; Heriawan, Mohamad Nur; Anggayana, Komang; Parnadi, Wahyudi Widyatmoko; Azwardi, Ichwan; Rubiarto, Rubiarto
Prosiding Temu Profesi Tahunan PERHAPI 2023: PROSIDING TEMU PROFESI TAHUNAN PERHAPI
Publisher : PERHAPI

Show Abstract | Download Original | Original Source | Check in Google Scholar

Pasir kuarsa merupakan salah satu bahan galian yang dimanfaatkan untuk memenuhi kebutuhan industri manufaktur. Pasir kuarsa yang diperoleh dari area penambangan timah aluvial memiliki kandungan silika (SiO2) yang cukup tinggi dengan rata-rata kadar 95%. Sehingga dalam alur pengolahan bijih timah, hasil penambangan dan pengolahan yang berlangsung telah menghasilkan pasir kuarsa berkualitas cukup tinggi sebagai produk sisa hasil pengolahan (SHP). Studi ini dilakukan untuk mengevaluasi potensi atau sumber daya material SHP yang berupa silika yang terdapat di lima lokasi di Kepulauan Bangka dan Belitung. Metode yang dilakukan untuk mengevaluasi sumber daya pasirkuarsa adalah survei geofisika dengan metode ground penetrating radar (GPR) tipe unshielded dan shielded untuk menginterpretasikan variasi ketebalan lapisan di setiap lokasi. Panjang lintasan pengambilan data GPR cukup beragam berkisar pada rentang 100 – 900 m tergantung pada luasan dan kondisi sebagian besar lokasi studi yang berupa kolong bekas tambang dan hutan sawit. Metode pemboran dengan spasi yang bervariasi mulai dari 50 m, 100 m, 150 m, sampai 200 m dilakukan untuk pengambilan sampel SHP dan meningkatkan keyakinan terhadap model geometri lapisan pasir kuarsa.Berdasarkan data hasil pemboran pada lima lokasi (blok) yang berada di Kepulauan Bangka dan Belitung diperoleh informasi berupa volume pasir kuarsa dan kandungan silika yang cukup signifikan dan dapat mendukung peluang bisnis terhadap komoditas tersebut. Kombinasi antara data pemborandan data GPR akan menghasilkan model geometri yang lebih akurat daripada berdasarkan data pemboran saja. Spasi pemboran yang semakin lebar menunjukkan perbedaan volume pasir kuarsa yang lebih besar antara interpretasi berdasarkan data pemboran saja dibandingkan dengan kombinasi data pemboran dan GPR. Sehingga penggunaan survei GPR untuk spasi pemboran yang lebih lebar terutamapada spasi 100 – 200 m dapat meningkatkan keyakinan terhadap hasil estimasi sumber daya pasir kuarsa

Drill Hole Spacing Analysis for Evaluation of Quartz Sand Resources as Residual Material from On-Land Alluvial Tin Processing based on Global Estimation Variance and Kriging Variance, with Case Study in the Bangka and Belitung Islands, Indonesia Safitra, Roby Mardiyan; Heriawan, Mohamad Nur; Anggayana, Komang; Rubiarto, Rubiarto; Lubis, Ichwan Azwardi
Journal of Engineering and Technological Sciences Vol. 56 No. 5 (2024)
Publisher : Directorate for Research and Community Services, Institut Teknologi Bandung

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/j.eng.technol.sci.2024.56.5.9

On-land alluvial tin mining activities produce residual materials from mineral processing or mineral washing; the major one of these is quartz sand, which can be utilized in the manufacturing industry. As time goes by, the reserves of alluvial tin are decreasing, which is in line with the increasing residual material from abundant mineral processing. Mining procedures are carried out following the Indonesian government regulations, covering mining as well as reprocessing. This motivated us to evaluate the potential of quartz sand at two mining sites in Bangka and Belitung Islands. This study evaluated alluvial tin processing residual quartz sand through drill hole spacing analysis (DHSA) by comparing two geostatistics parameters, namely global estimation variance (GEV) and kriging variance (KV). Drill hole samples were taken with varying spacing, ranging from 50 to 200 m, after which geostatistical analysis was carried out. With several simulations, the incorporation of GEV and KV was able to produce the optimal drill hole spacing with measured resource categories in the range of 40 to 55 m, indicated resources in the range of 55 to 85 m, and inferred resources >85 m. Accordingly, the total estimated quartz sand resources of both sites were obtained.

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