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INDONESIA
IJOG : Indonesian Journal on Geoscience
Published by Geological Agency of Indonesia
ISSN : 23559314     EISSN : 23559306     DOI : -
Core Subject : Science,
Earth & Planetary Sciences
The spirit to improve the journal to be more credible is increasing, and in 2012 it invited earth scientists in East and Southeast Asia as well as some western countries to join the journal for the editor positions in the Indonesia Journal of Geology. This is also to realize our present goal to internationalize the journal, The Indonesian Journal on Geoscience, which is open for papers of geology, geophysics, geochemistry, geodetics, geography, and soil science. This new born journal is expected to be published three times a year. As an international publication, of course it must all be written in an international language, in this case English. This adds difficulties to the effort to obtain good papers in English to publish although the credit points that an author will get are much higher.
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Articles 10 Documents
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Search results for , issue "Vol. 9 No. 1 (2022)" : 10 Documents clear
Vertical Fracability Model on Lithofacies Association of Brownshale Formation from Outcrop Analog Using Rock Mechanical and Mineralogy Correlation Method: A Preliminary Study of Shale Hydrocarbon Development in Bengkalis Trough, Central Sumatra Basin Aris Buntoro; C. Prasetyadi; Ricky Adi Wibowo; Suranto Suranto
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.9.1.87-104

Abstract

DOI:10.17014/ijog.9.1.87-104In the production stage of shale hydrocarbon with very low permeability, an in-depth analysis of the mechanism governing hydraulic fracking is required to open natural fractures, so that the fractures are connected to allow maximum flow of hydrocarbon fluids. This study is dedicated to create a vertical fracability model of shale hydrocarbon as a basis for planning the optimal position combination of horizontal well with multistage hydraulic fracking based on the correlation of rock mechanical and mineralogy analysis. Because in-situ core data is not available, this study uses shale core and shale sample data from outcrop analog (surface) as as a representative of the Brownshale Formation in the Central Sumatra Basin. At present, Indonesia has a very large potential for shale hydrocarbon, mainly from the Brownshale Formation of Pematang Group as the main source rock in the Central Sumatra Basin, which spread over several troughs, namely: Balam, Rangau, Kiri, Aman, and Bengkalis, where Bengkalis trough has the largest area compared to others, so it was chosen as the research target. In creating the vertical fracability model, information about the elastic rock properties, namely Young's Modulus (YM) and Poisson's ratio (PR) are needed as the basis for determining the depth interval of the formation with high fracability. Fortunately, at this time there was a very good outcrop analog at the coal mine site of PT. Karbindo in Kiliranjao, and there were also several outcrop analog locations in Limapuluh Koto area, West Sumatra. The vertical fracability model of shale hydrocarbon of the Brownshale Formation shows an interesting phenomenon, where the sweetspot fracable window interval is in the low YM - high PR zone, so it can be concluded that the low YM - high PR zone is a good candidate for hydraulic fracking. In contrast, the fracture barrier interval is in the high YM - high PR and low YM - low PR zones, where both are correlated with high Brittleness Index (BI), but the Fracability Index (FI) is low. I t can be concluded that high YM - high PR and low YM - low PR are inappropriate interval as a candidate for hydraulic fracking. This phenomenon is confirmed by the presence of a dominant carbonate mineral at the upper section as fracture barrier, while at the lower section as a sweetspot fracable window, which is more dominated by quartz mineral.
Application of Landsat 8 Image in An Assessment of Hydrothermal Alteration Mapping in Dense Vegetation: A Case Study from Kokap Area, Kulon Progo Agung Setianto; Bayu Raharja; Anastasia Dewi Titisari
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.9.1.45-60

Abstract

DOI:10.17014/ijog.9.1.45-60Several researchers through geochemical analysis have proven the presence of gold mineralization in Kokap, Kulon Progo, as a result of hydrothermal alteration. Alteration mapping with optical remote sensing images in tropical areas is very difficult due to atmospheric conditions, dense vegetation cover, and rapid weathering. This study aims to assess the ability of Landsat 8 images in the mapping of hydrothermal alteration in Kokap, Kulon Progo, with the Principles Component Analysis (PCA) method. Three conventional machine learning methods, including artificial neural network (ANN), maximum likelihood classification (MLC), and support vector machine (SVM) were compared to find an optimal classifier for hydrothermal alteration mapping. The experiment revealed that the MLC method offered the highest overall accuracy. Two alteration zones were mapped, i.e. argillic zone and propylitic zone. The comparison results showed that the MLC classification of band ratio images of 5:2 and 6:7 yielded a classification accuracy of 56.4% and kappa coefficient of 0.36, which was higher than those of other machine learning methods and band combinations. The combination of Landsat 8 with DEM succeeded in increasing accuracy to 59.5% with kappa coefficient of 0.4.
Magma Evolution of Lasem and Senjong Volcanic Complex: High-K Magmatism in Sunda Arc, Indonesia Haryo Edi Wibowo; Agung Harijoko; Mradipta Lintang Alifcanta Moktikanana; Mohammad Yazid Abdillah
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.9.1.131-145

Abstract

DOI:10.17014/ijog.9.1.131-145Lasem and Senjong Volcanic Complex (LSVC) is one of four Quaternary volcanic complexes with high-K magmatism distributed in the northern coast of Central Java. This research aims to understand the magmatic evolution of the volcanic complex. Morphostratigraphy analysis and field observation show twelve pyroclastic density flow units in Lasem Volcano, distributed mainly in the northern to eastern flanks, but minor occurrences in the southern and western flanks. Meanwhile, nine lava flow units of Lasem are concentrated on the south flank of the volcano. Lasem stratovolcano is attributed to four lava domes distributed on the northern and southern flanks. Senjong Volcano comprises one lava flow and four lava domes. Rocks of LSVC are composed of plagioclase, K-feldspar, hornblende, clinopyroxene, and opaque minerals embedded in the groundmass of volcanic glass and microlite. These calc-alkaline rocks range from basaltic trachyandesite to trachyte in composition. The magma of LSVC can further be grouped into High K/Rb and Low K/Rb types, which dominate the Lasem and Senjong Volcano products, respectively. These two magma types consistently show divergent trends in K/Rb and Rb/Nb plots against increasing silica, indicating distinct differentiation processes of similar magma source.
Rainfall Infiltration-induced Slope Instability of the Unsaturated Volcanic Residual Soils During Wet Seasons in Indonesia Agus Setyo Muntohar; Jazaul Ikhsan; Hung-Jiun Liao; Apiniti Jotisankasa; Victor G. Jetten
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.9.1.71-85

Abstract

DOI:10.17014/ijog.9.1.71-85Located in the ring of fire, Indonesia is widely covered by volcanic soil deposits in various hilly or mountainous areas, especially in Java Island. It is also being characterized as a tropical region, rainfall-induced slope failure in residual volcanic soil, and it is of practical significance to study its mechanism. This paper presents the study of the influence of rainfall and antecedent rainfall pattern on the stability of a residual slope in Yogyakarta. Two residual soil types, clayey sand, SC, and high plasticity clay, CH, were investigated in this study which is of different soil-water and hydraulic characteristics. The studied area was located in Kedungrong Village, Samigaluh, Kulonprogo. The rainfall record was obtained from the automatic rain gauge station in Kalibawang catchment area during November 2001. Two rainfall scenarios were modelled in the numerical analysis; those classified as the major rainfall that precipitates for thirty days (Condition 1) and the three influencing-rainfall (Conditions 2 to 4). Based on the simulation result from the major rainfall and the antecedent rainfall, the slope tended to fail when the precipitation went on continuously for three days with the so-called rolling rainfall pattern. The stability of the slope was dependent on the soil-water and hydraulic properties of the soil layer.
Earthquake Forces on the Stability of the Meninting Diversion Tunnel Design Based on Current Seismic Conditions of Lombok Island Didi Supriadi Agustawijaya; Rian Mahendra Taruna; Ausa Ramadhan Agustawijaya
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.9.1.105-117

Abstract

DOI:10.17014/ijog.9.1.105-117A series of earthquakes in 2018 have ruined thousands of buildings, and affected the stability of many infrastructures in Lombok Island. The Meninting dam, located at just a 20 km distance from the epicentre of the 5th August earthquake, is one of the many infrastructures being constructed in the island. Unfortunately, stability problems might arise to the dam, in particular to its diversion-spillway tunnel, since the tunnel was designed by using the Indonesian Standards SNI 1726:2012 for the estimation of earthquake forces into the design. After the earthquake events in 2018, seismic conditions of Lombok Island changed, resulted in changing seismic parameters. Seismic forces might shear off the friable weak volcanic rocks around the tunnel, and then consequently, the residual strength of the rocks had to stand the tunnel construction, so its factor of safety reduced. Thus, the tunnel required some stability improvements by adding more support instalments, including grouting and rock bolting. This is important for the tunnel to face probable similar severe earthquakes in the future.
Behaviour of Friction Resistance of Pile Groups on Clay Soil During Loading Tests: Case Study in Semarang and Temanggung, Central Java, Indonesia Muhammad Mukhlisin; Budi Hamdani; Erna Novita; Sukoyo Sukoyo; Aiun Hayatu Rabinah
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.9.1.61-69

Abstract

DOI:10.17014/ijog.9.1.61-69Shear strength parameters influence the bearing capacity of pile foundations, i.e. internal friction angle (ϕ) and cohesion (c). Soil parameters are affected by water content, which can be altered by climate change. Clay soils have high swelling and shrinking potential, caused by changes in water content, and this can affect the failure of foundations. Analysis of the influence of moisture content on the friction resistance of piles needs to be carried out, especially in clay soils. This research uses laboratory experiments to model four piles, with diameters of 16 mm. The pile group models are modeled in soil samples taken from three different locations, i.e. Tembalang, Pengaron, and Pingit, in Central Java. The samples were treated (soaking and drying) for one, three, and seven days. The USCS categorization of the soil samples were OH (organic clay with medium plasticity) and CH (inorganic clay with high plasticity). Friction resistance in piles within soaking conditions, decrease in proportion to an increase in moisture content. On the other hand, friction resistance increases under drying conditions. However, the friction resistance of the soil that had been treated (by soaking and drying) was not equal to the initial conditions.
REE-Bearing Minerals in Tin Waste Dumps of Singkep Island: Geochemical Identification and Recovery Ronaldo Irzon
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.9.1.15-26

Abstract

DOI:10.17014/ijog.9.1.15-26Instead of environmental hazard, tailing might contain resources which could be reworked with the development of mining and separation technologies. Tailing dumps and waste ponds which associated with the long period of tin mining are easily found in Singkep Island. The waste should be processed to recover and purify precious metals within, and to reduce environmental degradation. REE-bearing minerals identification in tin tailing based on trace and rare earth element abundances is the aim of this study. Concise mineral beneficiation is illustrated for any further re-work strategy. The tailings collected from four locations in Singkep were analyzed for their trace and rare earth element compositions using ICP-MS at The Centre for Geological Survey. REE content in concentrates was upgraded at the range of 9 to 94 folds of the corresponding wastes. Monazite-(Ce), xenotime, and zircon are the REE-bearing minerals of the studied samples according to the elemental composition. Gravity, flotation, magnetic, and electrostatic methods would be applicable to separate the REE-bearing minerals from the tailing.
Geothermal Surface Manifestation Identification Using Airborne Hyperspectral Imagery Case Study: Davis-Schrimpf Geothermal Field, Salton Sea, California Izzul Qudsi; Muhammad Rifat Noor
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.9.1.119-130

Abstract

DOI:10.17014/ijog.9.1.119-130Research on surface geothermal evidence has been done extensively using remote sensing techniques. For detailed remote sensing exploration on geothermal areas, UAV and airborne based were preferred over the satellite-based sensor. In this research, anomalies in surface temperature, mineral occurrence, and ammonia emission were studied on a set of airborne hyperspectral imagery from NASA, the Hyperspectral Thermal Emission Spectrometer (HyTES). High-resolution surface temperature and mineral maps were able to identify and describe the mineralogy of the mud pots and gryphons at the Davis-Schrimpf Geothermal Field, Salton Sea, California. From the surface temperature map, the surface temperature of the geothermal features was measured at approximately 314°K (40oC) and higher. The purest pixels from MNF transformation of the first four cleanest bands of emissivity map produce endmembers that include the geothermal indicator minerals (barite, anhydrite, quartz, gypsum). Based on the mineralogy deposits, these manifestations are classified as potassic alteration types from a porphyry system that could be an indication of an active geothermal system. This also explains that the surface features are part of the upper reservoir of the Salton Sea Geothermal Field. On the other hand, ammonia detection that was performed in this research failed to get any clear recognition from the simple image processing. It is concluded that the airborne hyperspectral imagery could be a reliable option for remote sensing geothermal exploration, as it was able to characterize the surface geothermal manifestation with quite good detail using this imagery from a wide area of survey.
Contributions of Loading and Unloading to Overpressure: Analytical Results from The Shelfal Area of The Lower Kutai Basin, Indonesia Agus M. Ramdhan; Lambok M. Hutasoit
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.9.1.1-13

Abstract

DOI:10.17014/ijog.9.1.1-13A modified Bowers Method is applied to analyze the contribution of loading and unloading to total overpressure magnitude in the shelfal area of the Lower Kutai Basin. The method combines Bowers Method with density-sonic cross plots to differentiate contributors to overpressure. This method has a strong physical background, and has proven to give satisfactory overpressure estimation in the studied area. Several processes related to overpressure and compaction in the studied area have also been deduced: 1) top of overpressure is caused by unloading due to gas generation, 2) gas generation on its own can produce overburden-scale overpressure magnitude, 3) loading starts to contribute to overpressure at depth, where the lithology is dominated by mudrocks, 4) effective stress history experienced by mudrocks before unloading, and 5) the presence of two compaction lines and therefore two associated velocity-effective stress relations.
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

Abstract

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. 

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