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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
 1 
Search results for , issue "Vol. 8 No. 1 (2021)" : 10 Documents clear
A Combined Petrographic-Geochemical Provenance and Tectonic Setting Study of Palaeozoic Rocks, in East Johor Basin, Peninsular Malaysia Sugeng Sapto Surjono; Mohd. Shafeea Leman; Kamal Roslan Mohamed; Che Aziz Ali
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.8.1.11-24

Abstract

DOI: 10.17014/ijog.8.1.11-24Several greywacke sandstones considered as Paleozoic rocks are found in three different formations, i.e. the Dohol, Linggiu, and Tanjung Leman Formations within the Palaeozoic East Johor Basin. The compositions of twenty-nine sandstone samples were identified using petrographical and geochemical methods to determine the provenance of sandstones as well as the tectonic setting of pre-and syn-sedimentation. Seven samples of them were examined using point counting method to obtain the mineralogical compositions. This petrographical point counting was done by plotting composition percentages to QFL and QmFLt triangular diagrams, The results showed a magmatic arc for Dohol Formation, a change from a magmatic to a recycled orogen for Linggiu Formation, and a recycled orogen for Tanjung Leman Formation. The recycled orogen tectonic setting of Linggiu and Tanjung Leman may have come from the underlying metamorphic and sedimentary rocks of Mersing and Murau Formations. Meanwhile, twenty-two samples were examined using a geochemical method by utilizing the ratio of K2O/Na2O and SiO2. The samples suggest a tectonic setting from both passive continental margin (PM) and active continental margin (ACM). Based on these findings, it is interpreted that the sedimentary rocks in East Johor were deposited in a subduction-related basin, such as fore-arc, magmatic arc, and back-arc.
Pore Type Inversion and S-Wave Velocity Estimation for the Characterization of Salawati Carbonate Reservoir M. Syamsu Rosid; Yogi Muliandi; Al Hafeez
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.
Komatiitic Lamprophyre in West Sulawesi: First Evidence for >1350°C and 3.5 - 3.8 GPa Mantle Melts Shaban Godang; Fadlin Fadlin; Bambang Priadi; Arifudin Idrus; I Gde Sukadana
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.8.1.39-58

Abstract

DOI: 10.17014/ijog.8.1.39-58The presence of lamprophyric lavas of Late Cenozoic in Talaya Volcanic Formation at the boundary between the subregencies of Mamuju and Tabulahan (Western Sulawesi) associated with the mantle enrichment rocks of the Adang Volcanics is the subject of this study. Petrologically, lamprophyre is composed of orthopyroxene (enstatite), clinopyroxene (augite), biotite, leucite, amphibole, magnetite, and autometasomatism of chlorite in grain minerals and groundmass. The lamprophyre is classified into monchiquite shoshonitic lamprophyre, and it has a komatiitic composition with the ratio of MgO/Al2O3 > 0.7906 (in wt %). The komatiitic monchiquite lamprophyre is characterized by high MgO (10.02 - 12.67 %), relatively low alumina (Al2O3= 10.98 - 11.70 %), SiO2= 46.43 - 47.8 %, TiO2 (0.84 - 1.00 %), FeOt (7.75 - 7.88 %), and relatively high content of alkaline (Na2O: 2.20 - 2.59 %; K2O: 1.58 - 2.45 %; Total alkali: 4.00 - 4.89 %, and CaO (9.29 - 10.71 %). The geochemical trace element plots using various diagrams suggests the geotectonic setting of the lamprophyric rock was formed in suprasubduction alkaline continental-arc, and the proposed source of magmatism comes from the suprasubduction activities from the east. The protolith of magma was originated from partial melting of depleted MORB mantle (DMM), composed of pyroxene-peridotite (garnet-lherzolite). The partial melting conditions are suggested to occur at high pressure (3.5 - 3.8 GPa) and the depth of ~120 km with melting temperature of >1350°C, and the magma is dominantly controlled by olivine fractional crystallization.
The Drop of Relative Velocity Variation and Coherence Values Prior to Sinabung 2013 Eruptions Yasa Suparman; Afnimar Afnimar; Devy Kamil Syahbana
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 Omolayo Ajoke Omorinoye; Zaini Bin Assim; Ismail Bin Jusoh
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.
Earthquake Potential Hazard Analysis of Palembang City, Sumatra Island Wahyu Triyoso; Aris Suwondo; Zael Yahd Xanggam Naibaho
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.8.1.1-9

Abstract

DOI: 10.17014/ijog.8.1.1-9Most of the destructive earthquakes in Sumatra are dominated by thrust mechanisms that occur due to the process of subduction and some earthquakes with strike-slip fault sources such as the Sumatra fault and northwestern Sumatra. The subduction zones along western Sumatra and Sumatran fault zones are active seismic sources of earthquake events. The seismotectonics of South Sumatra can be affected by earthquakes triggered by these seismic sources. In this study, an estimation and analysis of the potential for earthquake hazard curves were carried out in Palembang City due to the influence of subduction zone sources, strike-slip faults, and intermediate to deep earthquake sources. The algorithm of the seismicity smoothing was applied to estimate the seismicity rate for megathrust sources, active faults, and intermediate to deep earthquake sources. The results of the earthquake hazard potential curve showed that the estimated Peak Ground Acceleration (PGA) in the bedrock of the subduction earthquake sources was greater than the estimated ground shaking due to strike-slip fault sources as well as intermediate to deep earthquake sources. To understand better the potential ground shaking, the evaluation of PGA at the surface was then estimated by including the amplification factor. The amplification factor was calculated using the Horizontal-Vertical Spectral Ratio (HVSR) method. Based on the PGA estimated at the surface of 10% probability exceedance level during 50 years, the Palembang City has a potential shaking of around 35 gal, which is likely to be caused by a megathrust earthquake source.
Insights on Mineralogy and Chemistry of Fairview Gold Mine, Barberton Greenstone Belt, South Africa Mohammed Alnagashi Hassan Altigani
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.8.1.73-99

Abstract

DOI: 10.17014/ijog.8.1.73-99Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and electron microprobe analysis (EMPA) techniques were used to determine the mineralogy and chemistry of dominant sulphide and associated gold deposits at the Fairview Gold Mine of the Barberton Greenstone Belt (BGB). The rocks and ore mineral associations at the Fairview Mine indicate mesothermal (orogenic) conditions for the gold deposit. The whole rock chemistry of the Fairview Mine reflects calc-alkaline affinities, and felsic provenance is revealed by high SiO2, K2O, Al2O3, and TiO2, and low Fe2O3, MgO, Ni, and Cr contents. The mineral assemblages of the Fairview Mine rocks and ores indicate three phases of metamorphisms; regional prograde, thermal, and retrograde metamorphism, which caused zonation and heterogeneity of the ore minerals. The principal ore minerals in this deposit are pyrite, arsenopyrite, pyrrhotite, chalcopyrite, and rare sphalerite, as well as minor gold. The obtained results revealed that sulphides of the Fairview Mine are divided into two types (generations) varying in their morphology, association, and elemental composition. The old type 1 is porous, anhedral, heterogeneous, contains inclusions and rich in As, Ni, Co, and Au compared to type 2. Trace-element distribution and occurrence mode of gold at Fairview mine reflect two phases of gold mineralization. The first stage is associated with sulphides (mainly pyrite and arsenopyrite), whilst the second phase is free-lode hosted by silicates (mainly quartz).
Mineralogical, Geochemical, and Raman Spectral Characteristics of Amphibole Mineral Types in Amphibolite from Southern Sanandaj-Sirjan Metamorphic Belt (Iran) Hesam Moeinzadeh; Hadiseh Rahimisadegh; Mohsen Moazzen; Kazu Nakashima
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.8.1.59-72

Abstract

DOI: 10.17014/ijog.8.1.59-72The current study is related to amphiboles in amphibolite rocks in the northwest of Golgohar Iron Mine located in the southern part of Sanandaj-Sirjan metamorphic zone.Petrography observations indicate that the studied rocks are of ortho-amphibolite type, formed from metamorphism of igneous rocks. The analysis of amphibole crystals in amphibolites of the region was done by petrography, electron microprobe, and Raman spectroscopy. Raman spectral pattern of the studied minerals was discussed in comparison to mineral type and chemistry characteristics. Based on mineral chemistry studies, it was discovered that all amphiboles in the studied rocks are calcic with (Ca+Na)B≥1.34 and SiIV between 6.27 and 6.76 atoms per formula unit. Based on their enrichment in the elements Al and Fe3+, their composition varies from tschermakite to magnesio-hornblende. Raman spectral peak pattern for amphiboles and terrestrial tremolite does not have significant discriminable differences. However, Raman peak patterns of tremolite have clearly different features versus tschermakite. According to the general formula of amphiboles [A0-1B2C5T8O22(OH, F, Cl)2], the Raman spectrum variability of the tschermakite and tremolite can be due to the position of A site, Al incorporation into M1 + M2 + M3 sites and into the T site.
Study of Production-Injection Strategies for Sustainable Production in Geothermal Reservoir Two-Phase by Numerical Simulation Heru Berian Pratama; Nenny Miryani Saptadji
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.8.1.25-38

Abstract

DOI: 10.17014/ijog.8.1.25-38The rapid pressure decline in liquid-dominated geothermal fields is a significant problem affecting the steam supply to the power plant. This study aims to understand the reservoir characteristics changes due to extraction of mass and heat from the reservoir through a numerical reservoir simulation under various strategies production-injection. The development of a liquid-dominated geothermal field model is assessed with various production strategies and injection strategies for the generation of 110 MW and 220 MW using a separated steam cycle. Thirty two production-injection strategies from a full factorial have been successfully carried out. The results show a low decrease for both reservoir pressure and decline rate for the steam cap and brine reservoir's production strategy combined with deep and dispersed injection strategy. From a simulation for 220 MW, the strategy for sustainable production is 25% from the steam cap and 75% from brine reservoir, dispersed, and deep reinjection with 9 make-up wells from the steam cap. The lowest decline rate after the 30th year is 0.5%, with Arps 1.0 exponent harmonic decline curve. The implementation of the production-injection strategy needs to be planned from the beginning of exploration or exploitation so that the strategy can be adjusted to changes in reservoir characteristics without causing problems.
Striations at The Base of The Paleo-Fan and Channel Revealed by 3D Seismic Data, Offshore Cameroon Anh Ngoc Le
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.8.1.101-107

Abstract

DOI: 10.17014/ijog.8.1.101-107The 3D seismic data, offshore Cameroon, reveal the evidence of a Pliocene fan and a channel with a series of striations at their base. The fan and channel developing in Early Pliocene, were characterized by high amplitude reflections with bi-directional downlap on the base of the Pliocene sequence, and interpreted to be deep-water sandrich fan and channel. Pliocene channel flowed from east to west in the High Gradient Slope (HGS), whereas, the fan extended from NE to SW on the Low Gradient Slope (LGS). Individual striations have been imaged that are 20 - 50 m wide, c. 10 - 20 km long, and 4 - 8 m deep, trending NE - SW and E - W, slightly divergent patterns toward downslope. Striations are observed at the base of fan and channel suggesting the beginning of a period of unstable slope creating NE - SW slides in LGS and erosion in HGS. They were followed by the deposition of large scale fan deposits on the LGS and a series of parallel aggradational channels in the HGS. The striated unconformity at the base of the Pliocene sequence may be the result of a major tectonic uplift event or significant climate changes.

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