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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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The Drop of Relative Velocity Variation and Coherence Values Prior to Sinabung 2013 Eruptions Suparman, Yasa; Afnimar, Afnimar; Syahbana, Devy Kamil
Indonesian Journal on Geoscience Vol 8, No 1 (2021)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.8.1.109-117

Abstract

DOI: 10.17014/ijog.8.1.109-117The cross-correlations of ambient seismic noise at Sinabung Volcano were analyzed from February 2013 to February 2014. Many eruptions occurred during these periods, started on 15 September 2013. Looking at the variations in the coda of the correlations, two types of measurements can be distinguished associated to two types of changes: relative velocity variation and waveform decoherence. The drop of relative velocity variations and waveform decoherence were observed for each station pair of Sinabung one to two months before the first eruption. These changes in accordance to the deformation of the Sinabung edifice were estimated from geodetic measurements, since an analysis of baseline change between GPS stations indicated an inflation of the volcanic edifice prior to September 2013 eruption. The monitoring of relative velocity variations and decoherence provides insights into the ongoing processes in the volcanic edifice to assist in determining the level of volcanic activity.
Geomorphological and Sedimentological Features of River Sadong, Sarawak, Malaysia Omorinoye, Omolayo Ajoke; Assim, Zaini Bin; Jusoh, Ismail Bin
Indonesian Journal on Geoscience Vol 8, No 1 (2021)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.8.1.119-130

Abstract

DOI: 10.17014/ijog.8.1.119-130The effect of topography, climate, soil, and geology on River Sadong sediments is related to its geochemistry. Eighteen surface sediments and five core samples were collected in replicates from six sampling sites along River Sadong, Sarawak, Malaysia. The main aim of this study is to describe the geomorphology and sedimentological characteristics of the river sediments. This was achieved by the study of the processes that form the sediments and influence their physical and chemical characteristics. The sediments were analyzed for their sedimentological characteristics. The results indicated that the studied area is enriched with organic matter, and there are no sedimentary structures in its vicinity.
Pore Type Inversion and S-Wave Velocity Estimation for the Characterization of Salawati Carbonate Reservoir Rosid, M. Syamsu; Muliandi, Yogi; Hafeez, Al
Indonesian Journal on Geoscience Vol 8, No 1 (2021)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.8.1.131-146

Abstract

DOI: 10.17014/ijog.8.1.131-146A rock physic study was conducted in Salawati Basin, Papua, Indonesia. This field produces hydrocarbons from coral reef formation. The carbonate reservoir has a very heterogeneous and complex pore type. This study useddata from ten wells. Two wells (K-2 and Z-1) have Vs data, while the other eight do not. This study was done to identify the pore type of the reservoir rock, and to estimate the Vs log data in this area. The characterization of the carbonate reservoir was carried out using the DEM (Differential Effective Medium) inversion method. In calculating the bulk (κ) and shear (μ) modulus, the DEM method is supported by the HSW (Hashin-Shtrikman-Walpole) formula in the form of its rock matrix model and Gassmann's relation for its fluid contents. The inversion results show that in eight wells the reservoir is dominated by crack pore type, and in the other two wells the reservoir is dominated by stiff pore type. As for the Vs data, at reference wells K-2 and Z-1, the estimated Vs corresponds very well to the actual Vs, with RMS error of less than 2 m/s and 3 m/s respectively. Another qualitative verification shows that the pore type inversion results are almost perfectly consistent with thin-layer lithology data.
Coastal Area Management Based on Disaster Mitigation: A Case Study in Purworejo Regency, Indonesia Hidajat, Wahju Krisna; Anggoro, Sutrisno; Najib, Najib
Indonesian Journal on Geoscience Vol 8, No 2 (2021)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.8.2.147-156

Abstract

DOI:10.17014/ijog.8.2.147-156Indonesia is an archipelago blessed with the wealth of coastal resources, but also with the risk of natural hazards including tectonic earthquake and tsunami. This potential risk is high in the Purwodadi Subregency, Purworejo Regency, Indonesia, because of its location in an active subduction zone at the edge of the Indian Ocean. Therefore, this study was conducted in the region located on the southern coast of Java Island. The high probability of disaster in the area needs a proper coastal management strategy and mitigation measures. Hence, this study aims to establish an appropriate policy using the strength-weakness-opportunity-threat (SWOT) analysis. Furthermore, the data obtained from this novel analysis include the population and social vulnerability, geological conditions, landuse allocation, and disaster strategies. Each is carefully assessed and then incorporated into the matrix to obtain the result. In addition, the alternative strategies used are the development of disaster mitigation facilities, infrastructure, and institutional strengthening.
Geology, Vein Textures, and Fluid Inclusions of the Cibeber Low-Intermediate Sulfidation Epithermal Au-Ag Orefield, Western Java Dana, Cendi D. P.; Idrus, Arifudin; Setiawan, Iwan; Handayani, Esti; Yurniadi, Feddy; Meak, Ignas A.; Lai, Chun-Kit
Indonesian Journal on Geoscience Vol 8, No 2 (2021)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.8.2.157-175

Abstract

DOI:10.17014/ijog.8.2.157-175This paper describes the results of surficial geological and alteration mapping combined with several laboratory analyses, including petrography, ore microscopy, ore geochemistry, and fluid inclusion studies, aimed at establishing the nature of mineralization and alteration in the Cibeber area, West Java, Indonesia, and developing a genetic model. The area forms part of the Bayah Dome Complex, which hosts several gold-silver deposits. It is underlain by andesitic lava, tuff breccia, and subordinate sandstone. Its structural framework consists of joints, normal faults, NE-SW dextral strike slip faults, and NW-SE strike-slip faults. Hydrothermal alteration can be divided into four types, viz. silicification, clay-silica, argillic, and propylitic. Mineralization is mostly hosted in quartz veins showing a variety of textures, including massive, colloform-crustiform, breccia, lattice bladed, comb, and saccharoidal. Ore minerals consist of native gold and silver, pyrite, chalcopyrite, sphalerite, galena, tennantite-tetrahedrite, covellite, malachite, hematite, and goethite, while the gangue minerals quartz, illite, epidote, and calcite. Four stages of mineralization/veining are recognized: early, middle (the main ore forming stage), late, and supergene. The highest obtained metal grades are 8.17 ppm Au, 113.6 ppm Ag, 1.23% Cu, 1.28% Pb, and 1.2% Zn. Fluid inclusions from mineralized veins yielded temperatures of 222 - 280°C and salinities of 0.36 - 1.31 wt.% NaCl eq. The hydrothermal fluids are interpreted to have been largely of meteoric origin with the mineralization having formed at a depth of about 258 - 270 m below paleosurface. Both low-sulphidation and intermediate-sulphidation styles of mineralization are present.
Geochemistry Study of Cross-castic Magma Alkalinity Evolution Godang, Shaban; Priadi, Bambang; Fadlin, Fadlin; Leeuwen, Theo Van; Idrus, Arifudin
Indonesian Journal on Geoscience Vol 8, No 2 (2021)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.8.2.177-196

Abstract

DOI:10.17014/ijog.8.2.177-196The discrimination of magmatic alkalinity is a classic study that has never stopped for the past ninety years. Various methodologies have been developed since Shand’s classification using the method of alumina saturation to approach silica saturation and the methodology without involving alumina and silica such as K2O vs. Na2O and others, while the aim is to find out the evolution of alkalinity during the magmatic differentiation. The classical magmatic alkalinity evolution has been known as a castic magma alkalinity evolution, where the initial magma in the form of magma-X(a) will evolve along the stages of differentiation and remain a derivative of the initial magma {magmaX(a)}. The same philosophy is also explained in the ternary AFM diagram. Is the magmatic differentiation, followed by fractional crystallization, always an evolution of alkalinity based on caste? This question often raises current debates. This study takes the example of cogenetic volcanic and albitites. The application of the cogenetic volcanic using the selected diagram, which is ‘Three in one an overlaid diagram’. The output of the diagram presents the differentiation of magma which based on the evolution of Mg-series and Fe-series in a discontinuous branch of Bowen 1922 that can take place the castic and cross-castic, e.g. (a) from Mg-series to Mg-series {castic}, (b) from Mg-series to Feseries {cross-castic}, (c) from high-Mg tholeiitic basalt to calc-alkaline series {cross-castic}, (d) from Fe-series to Fe-series {castic}. While the evolution of magmatic alkalinity based on the continuous branch and refer to Trapezoid model generally occurring a cross-castic, e.g. (A) from sodic calc-alkaline to sodic alkaline-calcic, (B) from sodic calc-alkaline to shoshonitic alkaline-calcic, (C) from sodic calc-alkaline to potassic calc-alkaline, (D) from potassic calc-alkaline to shoshonitic alkaline-calcic, (E) sodic alkaline-calcic to sodic alkaline/peralkaline, (F) shoshonitic alkaline-calcic to potassic/ultrapotassic alkaline-calcic (cross-castic in subalkaline), (G) shoshonitic/potassic alkalinecalcic to shoshonitic/potassic alkaline/peralkaline. In this study, Fossa delle Felci volcanics (Italy) shows the evolution of magma from Mg-series to Mg-series, but the evolution of alkalinity of magma reveals the cross-caste (from sodic calc-alkaline to shoshonitic alkaline-calcic). Salak volcanics (Western Jawa) shows the evolution of magma from the Mg-series to Fe-series (cross-castic), and also the cross-castic in the evolution of alkalinity from sodic calc-alkaline to alkaline-calcic. Gothara albitites (India) clearly reveal the sodic-rich alkaline, which the magma generates from the evolution of sodic alkaline-calcic to sodic alkaline without the presence of potassic.
Earthquakes, Volcanic Eruptions, and Other Geological Disasters During Historical Records In Yogyakarta Special Region, Indonesia Mulyaningsih, Sri
Indonesian Journal on Geoscience Vol 8, No 2 (2021)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.8.2.197-212

Abstract

DOI:10.17014/ijog.8.2.197-212Yogyakarta, Indonesia, is a very fast developing area. The Yogyakarta historical time is divided into PreOld Mataram Era (1st - 8th century), Old Mataram Era (8th - 12th century), and Young Mataram Era (since 16th century). Geology has recorded many intermittent natural disasters within those historical time: volcanism, earthquakes, and rock movements as well. Those natural disasters have caused lots of damages, shown by buried and collapsed old buildings. Larger volcanic eruptions were known to occur once in 50 - 150 years ago, which were mostly followed by lahars as far as 32 km from the crater of Merapi Volcano, of which the last eruption was in 2010. Earthquakes were identified based on bumpy foundations that particularly occurred in the first pile of temple stones, i.e. at the temples of Kedulan, Plaosan, Morangan, Gampingan, and Boko Palace. Surface fractures are also present on the base of the palace floors. During 18th - 21st century, larger earthquakes with magnitude of 5 - 8 Richter scale occurred once in 20 - 70 years, of which the last earthquake was in 2006. A geological study clarified that there was a marine volcanism during the Tertiary with radial normal faults. The normal faults have been potential to reactivate since Plio-Pleistocene untill now, shown by surface deformations at Sudimoro Hills with a mass movement occurence as happened in Imogiri (March, 17th 2019), Pleret (2018), Piyungan, and Dlingo (March, 17th - 18th 2019). A stratigraphic study of volcaniclastic deposits around Gendol, Opak, Kuning, and Bedog Rivers shows potential floods around the rivers.
Mass-Transport Deposit In Deep Water Setting, Offshore Cameroon, West Africa Le, Anh Ngoc
Indonesian Journal on Geoscience Vol 8, No 2 (2021)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.8.2.231-219

Abstract

DOI:10.17014/ijog.8.2.231-219Mass-transport deposits (MTDs) have been analyzed over an area of 1,500 km2 in the deep-water setting of West Africa, focusing on the Early Tertiary sequence using high resolution of 3D seismic data. Observed MTD is about 10 km wide and 20 km long, up to 140 m thick, on the high gradient slope of 3.4o, extending from east to west. Internal seismic facies of the mass consist of extensional imbrication facies in the upslope area, thrusted facies downslope area. The MTD likely was triggered by a combination of mechanisms. Uplift in the Tertiary, dated at about 30 - 40 Ma, corresponding to the unconformity KS_5 may be the main reason that causes slope failure. Besides, possibly releasing gas from the gas hydrate stability zone may contribute to triggering mass-transport deposition in the study area.
Investigation of Geothermal Using Magnetotelluric Method in Babakan Bogor, Bengkulu Province, Indonesia Farid, Muhammad; Hadi, Arif Ismul; Sari, Lusi Puspita
Indonesian Journal on Geoscience Vol 8, No 2 (2021)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.8.2.221-231

Abstract

DOI:10.17014/ijog.8.2.221-231Bengkulu Province, due to be crossed by Bukit Barisan Mountains has relatively large geothermal reserves. This study aims to investigate the geothermal reserves in Babakan Bogor Village, Kepahiang Regency, Bengkulu Province. The magnetotelluric (MT) method with electric and magnetic sensors was used to record data in the fields. The electric sensor consisted of three porous pots, two of which were placed horizontally (Ex, Ey) and the other one vertically (Ez) as the ground. Magnetic sensors with two coils were placed horizontally (Hx, Hy) and one vertically (Hz). The data obtained in the field are in the form of rock resistivity values which are correlated with geothermal potential, so that the reservoir could be determined. Data recording in the fields used low frequencies, i.e. 128 Hz. Data processing was done using MAPROS software to convert time-series data to EDI file types. Input data in the MAPROS software is in the form of apparent resistivity vs. depth values. Furthermore, an inversion was carried out to obtain the true resistivity value as the output of the software. ZONDMT1 and ZONDMT2 were used to model the resistivity values in one dimension (1D) and two dimensions (2D). The results showed that there were geothermal reserves in the Babakan Bogor Village, Kepahiang Regency, at a depth of 1,500 to 5,000 m.
Tholeiitic Basalt in Banyumas Basin (Kebasen, Central Java): The Evidence of Sedimentary Recycling Input and the Contribution of Oceanic Slab on Fore-arc Active Continental Margin (ACM) Magmatism fadlin, fadlin; Godang, Shaban; Ariyanti, Nita; Hamzah, Wildan Nur; Aditama, Maulana Rizki
Indonesian Journal on Geoscience Vol 8, No 2 (2021)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.8.2.233-253

Abstract

DOI:10.17014/ijog.8.2.233-253The study of tholeiitic basalt is a general-classic study from geotectonic MORB, ocean island (OIB), continental rift, volcanic-arcs {IAB or Active Continental Margin (ACM)}. However, the geotectonic study of the tholeiitic volcanic-arcs is still unclear at the moment. In general, the arc tholeiitic is directly pointed to an island-arc volcanic, and the result of google search engine defines no existence of tholeiitic geochemistry which is formed from continental-arc volcanic (ACM). The problem lies in the model of discrimination diagram which is not able to discriminate ACM from the island arc volcanic. The spider diagram shows relatively similar of patterns as well as in the use of the isotope 143Nd/144Nd versus 87Sr/86Sr. Tholeiitic Kebasen pillow lava exhibits a slightly hydrothermal alteration (propyilitic alteration) which consists of plagioclase (labradorite-bytownite), olivine, pyroxene (diopside), hornblende, volcanic glass and other secondary minerals (such as iddingsite, zeolite, carbonate, sericite and opaque minerals). The results of the interpretation using the overlay diagram of Mg# and FeO(t)/MgO, diagram Nb/La vs. La/Yb, the overlaid diagram between the diagram of Zr/Y vs. Zr, newly developed diagram for sedimentary recycling (Th/Ce vs. SiO2) reveal the Kebasen lava is a differentiated tholeiitic rock with relatively low of Mg# (Mg# < 55) which is generated from geotectonic forearc ACM (Active Continental Margin) and involves the sedimentary recycling (Th/Ce > 0.1); furthermore, the trace element constituent is interpreted based upon the melting of oceanic slab (Zr/Y ~ 3). The magmatism of Kebasen lava is potentially formed at temperature of ~ 1240 oC and a pressure of ~ 1.7 GPa at the depth of ~ 56 Km.

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