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INDONESIA
Indonesian Journal on Geoscience
Published by Geological Agency Ministry of Energy and Mineral Resources
ISSN : 23559314     EISSN : 23559306     DOI : https://doi.org/10.17014/ijog.3.2.77-94
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. This Journal publishes 3 numbers per year at least 15 articles. It is a challenge for the management of the journal to remain survive and at the same time continuously maintain its quality and credibility in spite of those various constraints. Fortunately, this effort is strongly supported by the Geological Agency of Indonesia, as the publisher and which financially bear the journal. Last but not least the journal is also managed by senior geologist of various subdisciplines from various countries who are responsible for its quality.
Arjuna Subject : Ilmu Bumi dan Planet (semua kategori) - Geologi
Articles 323 Documents
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Geochemical Evaluation and Pore Type Characterization of Carbonaceous Rich Facies in Brown Shale Formation, Central Sumatra Basin Permana, Asep Kurnia; Iskandar, Yusup
Indonesian Journal on Geoscience Vol 7, No 2 (2020)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.7.2.121-133

Abstract

DOI:10.17014/ijog.7.2.121-133Brown Shale Formation of Pematang Group is a key source rock in the Central Sumatra Basin. The formation consists of three lithofacies: algal rich facies, mixed algal-carbonaceous facies, and carbonaceous rich facies. This paper focuses on evaluating the geochemistry and on characterizing the porosity of the carbonaceous rich facies. Geochemical evaluation of the carbonaceous source rocks was conducted using Rock-Eval pyrolysis, while mineralogy and microtextural characterization were assessed by incident light microscopy and scanning electron microscopy (SEM). The results show that the organic components of the carbonaceous source rocks are predominantly composed of vitrinite with minor inertinite and liptinite. The geochemical characteristics indicate that the carbonaceous rich facies could be ranked as a good to excellent level in terms of source rock potential with high TOC content, mainly containing kerogen type III as a gas prone potential. SEM results show that the pore types in the carbonaceous source rocks can be classified into three main types: porous floccules, organic-porosity, and intraparticle pores. Thus, the carbonaceous rich facies of the Brown Shale Formation contains gas prone source rocks with good generation potential, as well as organic rich shale unconventional reservoirs.
Temporal Variations of Petrological Characteristics of Tangkil and Rajabasa Volcanic Rocks, Indonesia Hasibuan, Reza Firmansyah; Ohba, Tsukasa; Abdurrachman, Mirzam; Hoshide, Takashi
Indonesian Journal on Geoscience Vol 7, No 2 (2020)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.7.2.135-159

Abstract

DOI:10.17014/ijog.7.2.135-159Tangkil and Rajabasa Volcanoes are neighbouring subduction-zone volcanoes located on the southeast tip of Sumatra Island (Sunda Strait, Indonesia). Stratigraphic correlation of lavas in Tangkil-Rajabasa volcanic area was established from field observations, morphological analysis, and K-Ar dating analysis. Detailed petrography and geochemical data of two and eleven lava units from Tangkil and Rajabasa, respectively, were then integrated with the stratigraphy to show the temporal variations. Early stage (> 4.3 Ma) effusives of Tangkil Volcano are dacitic to rhyolitic (67-71 wt. % SiO2; Tklf), whereas the later (c. 4.3 Ma) rocks are basalt to basaltic andesite (c. 52 wt. % SiO2; Tklm). Tangkil shows bimodal magmatism, of which the felsic endmember is > 71 wt. % SiO2 and < 0.1 wt. % MgO. Lavas of Rajabasa Volcano are comparatively younger (c. 0.3 to 0.1 Ma) with compositions ranging from basalt to andesite (51-62 wt. % SiO2; Rbs). Chemical variations of Rajabasa accounts for the interactions of at least three endmembers: Mg-rich medium-K basalt magma, low-Mg medium-K basalt magma, and high-K andesitic magma. During the long evolution of Rbs magma system, the temporal chemistry shows rising-falling variation in SiO2 and MgO indicating the three magmas were active. The felsic endmember magma of Rajabasa is fixed in composition (at ~62 wt. % SiO2; ~2.2 wt. % MgO). The rocks from the last Tklf and Rbs indicate open system processes by containing plagioclase and pyroxene phenocrysts that show resorption of evolved core and overgrowth of less evolved mantle. The multiple zones of dissolution-overgrowth in plagioclase crystals and the fluctuating trend in temporal whole-rock variation suggest that the changes of magmatic condition in temperature, H2O, or chemical composition were repetitive.
Geochemistry of Basaltic Merbabu Volcanic Rocks, Central Java, Indonesia Mulyaningsih, Sri; Shaban, Godang
Indonesian Journal on Geoscience Vol 7, No 2 (2020)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.7.2.161-178

Abstract

DOI: 10.17014/ijog.7.2.161-178The studied area is located along the hiking track of Kajor - Selo, the south flank of Merbabu Volcano, Central Java, Indonesia. Olivine basalt and augite-rich basalt compose the volcanic rocks. A geochemical study recognizes these basalts which tend to originate from the product of tholeiitic magma, in terms of transitional enriched mantle source. It is interpreted to have been formed as primary magma that mixed later with higher degrees of partial melting with a mantle wedge. Both fl uid and melt were derived from the mixing of lower active continental margin and subducting oceanic slab. This study also shows general trends of increasing incompatible elements, i.e. Rb, Ba, Pb2+, and Sr as LIL trace elements and Th, U, Nb, Ce, Zr, Hf, Nb, and Ta as HFS element comparing to basaltic andesites exposed at Thekelan, they show decreasing compatible of MgO, Fe2O3*, Al2O3, CaO, TiO2, Ni, Sr, and Ba in line with increasing SiO2. It was fractional crystallization process, shown by the slightly wide variation of Rb/Zr and La/Sm that indicates random crustal contamination.
Terrestrial Laser Scanner (TLS) Measurement in A Volcanic Area: Detection of Error Source and Scanned Object Intensity Haerani, Nia; Abidin, Hasanuddin Z.; Surono, Surono; Wijaya, Dudy D.
Indonesian Journal on Geoscience Vol 7, No 2 (2020)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.7.2.179-200

Abstract

DOI:10.17014/ijog.7.2.179-200The purpose of the study of Terrestrial Laser Scanner (TLS) application in an active volcanic crater is to detect the influence of gas emission and local atmospheric change into the accuracy of measurement.The measurement was conducted at Papandayan Volcano crater, along with the local temperature, humidity, and air pressure (thp). The measured target located near a gas emission hole gives a significant fluctuative range due to possible false return by gas particles. The refraction index was calculated using thp data. Two correction models were applied: velocity-geometry and atmospheric delay correction. The atmospheric delay correction gives a more reliable result, however their refraction index calculation does not accomodate specific volcanic gas yet. An intensity map obtained from TLS can also be used for rock segmentation. An experiment from some types of volcanic rocks shows that the intensity value is influenced by a weathering degree of rock outcrops. Rock segmentation using TLS intensity data for fresh outcrops is relatively easier, while for weathered rocks it still needs a field check for validation. The temperature of volcanic rocks also contributes to the intensity value. It is found that the intensity increases along with the temperature of rock.
The Determination of Volcanic Characteristics Based on Deuterium and Oxygen-18 Isotope Compositions: A Case Study at Dieng Plateau, Central Java Priatna, Priatna; Sulaksana, Nana; Hutabarat, Johanes; Haryanto, Iyan
Indonesian Journal on Geoscience Vol 7, No 2 (2020)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.7.2.201-213

Abstract

DOI:10.17014/ijog.7.2.201-213To find out volcanic characteristics, a geochemical approach can be used, one of which is through the measurement of deuterium and oxygen-18 isotopes from condensate and crater water samples. In this study, Dieng Plateau in Central Java was chosen, because it has a wide spread of fumarole fields and crater water. In addition, research in the Dieng Plateau is very useful in the management of geological-based tourism and geopark development in the future. Results of isotope analysis in Candradimuka Crater show the average number of isotope deuterium is δD – 500/00 and isotope oxygen-18 is δ18O –30/00 which produce the value of the mixing fraction of f 18O = 47.11%. This figure is the highest isotope number compared to other craters on the Dieng Plateau. The high value of the isotope-18 mixing fraction is supported by a strong plume from three vents in Candradimuka. Meanwhile, the results of crater water isotope tests obtained the highest results in Sikidang Crater with the value of the deuterium isotope is δD = – 10.300/00 and the isotope oxygen-18 is δ18O = 6.570/00 which are in the metamorphic water area from the mixing of magmatic processes with surface meteoric water. Based on the deuterium isotope approach with oxygen-18 crater water and fumarole condensate supported by subsurface temperature data, most of the Dieng Plateau has magmatic-hydrothermal characteristics, except Candradimuka Crater which belongs to the magmatic group. 
Risk Assessment of Groundwater Abstraction Vulnerability Using Spatial Analysis: Case Study at Salatiga Groundwater Basin, Indonesia Putranto, Thomas Triadi; Winarno, Tri; Susanta, Axel Prima Agita
Indonesian Journal on Geoscience Vol 7, No 2 (2020)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.7.2.215-224

Abstract

DOI:10.17014/ijog.7.2.215-224Salatiga Groundwater Basin (SGB) is located in Java Island, Indonesia. Administratively, it covers Semarang Regency, Salatiga City, and Boyolali Regency. Industry and community use groundwater to fulfil their daily need. Increasing number of deep wells that extract groundwater will cause some environmental problems, such as lowering groundwater level and subsidence at SGB. Thus, there is a need to assess the adverse impacts of groundwater abstraction. Risk assessment of groundwater vulnerability due to abstraction is the goal of this study. The research method was taking account of weighting of geological parameters, such as response characteristics of the aquifers, characteristics of aquifer storage, aquifer thickness, piezometric depth, and distance from the shoreline to conduct the groundwater vulnerability mapping. It was then overlaid on a map of regional spatial plan to develop the map of vulnerability risk due to abstraction. The groundwater vulnerability due to abstraction is categorized in the medium level. After being overlaid by the land use map, the risk of groundwater vulnerability due to abstraction is classified into three kinds, which are low, medium, and high. Regions with a low class can be neglected. Areas with moderate risk require an exhaustive review of technical requirements of the use of borewell. Areas with high-risk need a comprehensive consideration to use artesian wells by monitoring wells with drill licenses, tightening the permit to add new production wells, and conducting periodic review of groundwater monitoring.
Peak Metamorphic Conditions of Garnet Amphibolite from Luk Ulo Complex, Central Java, Indonesia: Implications for Medium-Pressure/High-Temperature Metamorphism in the Central Indonesian Accretionary Collision Complex Setiawan, Nugroho Imam; Osanai, Yasuhito; Nakano, Nobuhiko; Adachi, Tatsuro; Hendratno, Agus; Sasongko, Wahyu; Ansori, Chusni
Indonesian Journal on Geoscience Vol 7, No 3 (2020)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.7.3.225-239

Abstract

DOI:10.17014/ijog.7.3.225-239Garnet amphibolites, which suggest medium-pressure/high-temperature (MP/HT), are widely recognized in Luk Ulo Complex, Central Java. Their occurrences associated with high-pressure/low-temperature (HP/LT; eclogite, blueschist) metamorphic rocks in the Luk Ulo Complex will provide important constraint on the geodynamic model of Central Indonesian Accretionary Collision Complex (CIACC). This study aimed to estimates P-T metamorphic condition of garnet amphibolite from Luk Ulo Complex by using mineral parageneses, thermodynamic data, and NCKFMASHO pseudosection. Prograde stage assemblages represented by inclusions in the garnet, which are garnet core, zoisite, titanite, apatite, and quartz. Mineral coexistences at the peak P-T condition are garnet rim, magnesio-hornblende, zoisite, titanite, quartz, albite, and phengite. The retrograde stage represented by secondary minerals fill the crack in the garnet and other minerals, which are chlorite and quartz. P-T metamorphic condition of garnet amphibolite can only be interpreted from the peak metamorphic stage. The temperature of the garnet amphibolite is estimated using the garnet-amphibole and garnet-phengite geothermometers. Meanwhile, the pressure condition is estimated from phengite geobarometer. The results were compared to the stability and compositions of the phases in NCKFMASHO pseudosection in order to constrain the peak P-T metamorphic conditions. It is concluded that the peak P-T metamorphic condition for garnet amphibolite is 0.9 - 1.4 GPa and 558 - 606 ºC. The estimated peak P-T metamorphic temperature is higher compared to the previously published gradient geothermal of eclogite and tourmaline-eclogite in the Luk Ulo Complex. The MP/HT (amphibolite) and HP/LT (blueschist and eclogite) metamorphic rocks could have similar metamorphic ages if both footwall and hanging wall had initially very high thermal gradients and the rate of subduction was very slow (10 km/Ma or less).
Lava Discharge Rate of Sinabung Volcano Obtained from Modis Hot Spot Data Kriswati, Estu; Solikhin, Akhmad
Indonesian Journal on Geoscience Vol 7, No 3 (2020)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.7.3.241-252

Abstract

DOI:10.17014/ijog.7.3.241-252To find out the long term data of Sinabung magma discharge rate and how long a series of eruption will be ended, time series of the volume of magma discharge is required. The dominant eruption product is pyroclastic flow that begins with the growth of the lava dome, so it is important to determine the volume of the lava dome over time. The method of determining the volume of magma issued is carried out by using hotspot data to resolve the problem of prevented visual observations and ground measurements. The heat and volume flux data expressed within a long period for a better view of variations in the Sinabung volcanic activity are based on thermal satellite data. Related lava dome volume and seismic data are also displayed to be compared with the heat and volume flux data. The numbers of thermally anomalous pixels and sum of radiance for all detected pixels at Sinabung during an overpass in the period of 2014 to 2018 have a downward trend. The discharge rates in the period of January 2014 to April 2015, Mei 2015 to March 2016, April 2016 to March 2017, and June 2017 to February 2018 are 0.86 m3/sec, 0.59 m3/sec, 0.36 m3/sec, and 0.25 m3/sec, respectively. Assuming no new intrusion or deformation rate changes, the lava discharge will be in the lowest rate in the early 2020s.
Density Normal Compaction Trend in the Peciko Field, Lower Kutai Basin, Indonesia Ramdhan, Agus M.; Goulty, Neil R.; Jones, Stuart J.; Hutasoit, Lambok M.
Indonesian Journal on Geoscience Vol 7, No 3 (2020)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.7.3.253-265

Abstract

DOI:10.17014/ijog.7.3.253-265The density normal compaction trend is the mandatory parameter in order to calculate contribution of disequilibrium compaction to overpressure, in the presence of unloading to total overpressure. In this paper, mudrock compaction behaviour is studied in the Peciko Field. The density normal compaction trend was constructed in a normally pressured section, where the temperature is <1200C, within the transformation of smectite–illite zone. The compaction trend includes not only vertical effective stress, but also diagenesis, especially smectite-illite transformation, as dependant factor for compaction, both termed as β. This compaction trend is also known as Skempton-Duta compaction model. Quardros-Linares fifth-order kinetic reaction was found that could model smectite-illite transformation in the studied area fairly well. The plot between β and smectite content shows a very good match, confirming that Skempton-Dutta compaction model is valid for the entire range of smectite-illite transformation. In the area where the density log is unavailable, the density normal compaction can be constructed from temperature history acting as a proxy for smectite-illite transformation, with some local calibration.
Geochemical Compositions and Magnetic Susceptibility of Soils from Different Origins: A Case Study in South Lampung, Indonesia Santoso, Nono Agus; Iqbal, Mochamad; Kadja, Grandprix Thomryes Marth
Indonesian Journal on Geoscience Vol 7, No 3 (2020)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.7.3.267-272

Abstract

DOI:10.17014/ijog.7.3.267-272The study of rock weathering into soil is very important in geophysics. The geochemical and magnetic characteristics of soil were investigated in South Lampung using magnetic susceptibility and X-ray Fluorescence (XRF) measurements to identify the rock origin of the soil. The samples consisted of three soil types, those are granite soil, tuff soil in front of ITERA (Institut Teknologi Sumatra, South Lampung), and tuff soil inside ITERA. The tuffs (in front of and inside ITERA) and granite were taken in and around ITERA. The result showed that granite had the highest magnetic susceptibility value, while tuff soil in front of ITERA had the highest FeO content. Each sample can be distinguished by magnetic susceptibility and FeO content to prove that it can be used as a tool to distinguish the rock origin of soil.

Page 29 of 33 | Total Record : 323

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