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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.
Arjuna Subject : -
Articles 796 Documents
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Geochemical Signatures of Potassic to Sodic Adang Volcanics, Western Sulawesi: Implications for Their Tectonic Setting and Origin Shaban, Godang; Fadlin, Fadlin; Priadi, Bambang
Indonesian Journal on Geoscience Vol 3, No 3 (2016)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.3.3.195-214

Abstract

DOI:10.17014/ijog.3.3.195-214The Adang Volcanics represent a series of (ultra) potassic to sodic lavas and tuffaceous rocks of predominantly trachytic composition, which forms the part of a sequence of Late Cenozoic high-K volcanic and associated intrusive rocks occurring extensively throughout Western Sulawesi. The tectonic setting and origin of these high-K rocks have been the subject of considerable debates. The Adang Volcanics have mafic to mafitic-intermediate characteristics (SiO2: 46 - 56 wt%) and a wide range of high alkaline contents (K2O: 0.80 - 9.08 %; Na2O: 0.90 - 7.21 %) with the Total Alkali of 6.67 - 12.60 %. Al2O3 values are relatively low (10.63 - 13.21 %) and TiO2 values relatively high (1.27 - 1.91 %). Zr and REE concentrations are also relatively high (Zr: 1154 - 2340 ppm; Total REE (TREY = TRE): 899.20 - 1256.50 ppm; TRExOy: 1079.76 - 1507.97 ppm), with an average Zr/TRE ratio of ~ 1.39. The major rock forming minerals are leucite/pseudoleucite, diopside/aegirine, and high temperature phlogopite. Geochemical plots (major oxides and trace elements) using various diagrams suggest the Adang Volcanics formed in a postsubduction, within-plate continental extension/initial rift tectonic setting. It is further suggested magma was generated by minor (< 0.1 %) partial melting of depleted MORB mantle material (garnet-lherzolite) with the silicate melt having undergone strong metasomatism. Melt enrichment is reflected in the alkaline nature of the rocks and geochemical signatures such as Nb/Zr > 0.0627 and (Hf/Sm)PM > 1.23. A comparison with the Vulsini ultrapotassic volcanics from the Roman Province in Italy shows both similarities (spidergram pattern indicating affinity with Group III ultrapotassics volcanics) and differences (nature of mantle metasomatism).
Stable Isotopes and Hydrochemistry Approach for Determining the Salinization Pattern of Shallow Groundwater in Alluvium Deposit Semarang, Central Java Satrio, Satrio; Prasetio, Rasi; Hadian, Muhamad Sapari Dwi; Syafri, Ildrem
Indonesian Journal on Geoscience Vol 4, No 1 (2017)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.4.1.1-10

Abstract

DOI: 10.17014/ijog.4.1.1-10A groundwater study has been conducted in the Semarang City in August 2014, aiming to determine the source of shallow groundwater salinization using stable isotopes (18O, 2H) and water chemistry approach, and supported by local hydrogeological data. A number of shallow groundwater samples were taken at several locations with a depth of 0 - 35 m. Based on geological data, shallow groundwater of Semarang alluvium is dominated by insertion of sand-gravel and sandy-clay with average porosity of around 56.0 %. This layer is thinning towards the south and then increasingly thickening to the north and north-east of the studied area. The results of the analyses show that the characteristics of shallow groundwater, i.e. approximately 51% of groundwater, still have the original composition as meteoric water and the remaining approximately 49% obtained a shift in the isotopic composition as caused by interaction with seawater and the little influence of evaporation. The results of chemical analysis of water indicates that in dry seasons, shallow groundwater aquifers in the Semarang City is dominated by chloride (Cl-) with NaCl of water type. While the parameters of bicarbonate, chloride, and Na/Cl ratio, shallow groundwater can be classified into two groups, namely unintruded groundwater around 51% spread from the foot hills to the south towards the hills with elevations of 9 - 142 m above sea level and intruded groundwater around 49% spread from the coastline to the urban direction.
Lateral Facies and Permeability Changes in Upper Shoreface Sandstones, Berakas Syncline, Brunei Darussalam Ovinda, Ovinda; Lambiase, Joseph J
Indonesian Journal on Geoscience Vol 4, No 1 (2017)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.4.1.11-20

Abstract

DOI: 10.17014/ijog.4.1.11-20Several outcrops were studied to identify sedimentary facies and to analyze permeability distribution, through which an outcrop analogue for upper shoreface reservoirs can be established. Four facies were identified: upper shoreface, lower shoreface, offshore transition, and tidal ones. Stratigraphic correlation of eleven outcrops indicates that the upper shoreface sandstone is generally clean, well sorted, parallel, and planar cross laminated. The sand becomes thinner and pinches out to the northwest where the mud proportion increases within the sand. Muddier sand was deposited in a relatively low energy upper shoreface setting. The thickness of the upper shoreface reservoir sand generally is 5 m. It decreases to zero over approximately 1.3 km as the sand pinches out to the northwest. To the northeast, the thickness also decreases to 4 m over approximately 4 km. Permeability values are more variable laterally than vertically. The permeability distribution has an obvious relationship to the sedimentary facies and is mainly controlled by the proportion of mud and bioturbation. As the sand pinches out in the northwest, permeability decreases from 590 md to 97 md over 1 km. To the northeast, permeability also decreases to 152 md over approximately 4 km where the sand becomes highly bioturbated. These values indicate that the sands are of good to very good reservoir quality. It appears that there are no major barriers to the lateral flow of fluid within the upper shoreface sandstone.
Geochemistry of Late Triassic weak Peraluminous A-Type Karimun Granite, Karimun Regency, Riau Islands Province Irzon, Ronaldo
Indonesian Journal on Geoscience Vol 4, No 1 (2017)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.4.1.21-37

Abstract

DOI: 10.17014/ijog.4.1.21-37Karimun is an island with various geological deposits: tin, granite, sand, and others. The tin deposit in Karimun is related to the granitoid tin belt which extends from Myanmar to western Indonesia. Late Triassic Karimun Granite is composed of quartz, K-feldspar, plagioclase, biotite, and/or muscovite with small amounts of accessory minerals. The granitoid unit is different with other felsic intrusive rocks in Malay Peninsular because of its A-type affinity although it is classified as part of the Tin Islands. All eight samples can be classified as altered rocks since the occurrence of secondary chlorite was identifed both macroscopically and microscopically. Petrography was used to describe the minerals that form the samples, whereas XRF and ICP-MS were used to study Karimun Granite from the geochemical point of view. Harker diagrams confirm that the granites show similarity to other granite units in Malaysia except for CaO. Whalen diagrams indicate the granite as A-type as well as the SiO2, REE, and LILE amounts. REE content in the weak peraluminous granitoid ranges from 183 to 3,296 ppm with Eu and Ce show negative anomalies in the REE spider diagram. Negative anomalies of Eu, Ba, Sr, P, and Ti in normalized spider plot also conclude that the studied granitoid indicates A-type.
Audio-Magnetotelluric Modeling of Cimandiri Fault Zone at Cibeber, Cianjur Handayani, Lina; Maryati, Maryati; Kamtono, Kamtono; Mukti, M. Ma’ruf; Sudrajat, Yayat
Indonesian Journal on Geoscience Vol 4, No 1 (2017)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.4.1.39-47

Abstract

DOI: 10.17014/ijog.4.1.39-47The characteristic of Cimandiri Fault Zone has not been completely defined despite plenty of studies had already been accomplished. Therefore, an audio-magnetotelluric modeling was carried out. An audiomagnetotelluric survey was conducted at two parallel lines (N166oE) that intersected Cimandiri Fault Zone in Cibeber area, Cianjur. The distance between those two lines was 4.5 km and each line consisted of twenty-one stations with the distance between stations was 500 m. From the acquired forty-two apparent resistivity curves, inversion was executed to obtain two models. The models indicate layers with resistivity value of > 1000 ohm.m at about 500 m depth at both lines, which are associated to the basement layer. Columns of low resistivity zones in about the middle of each model represent fault zones as the weak zones of the area, and both models displayed them slightly dip southward as thrust faults.
Landslide Vulnerability Assessment (LVAs): A Case Study from Kota Kinabalu, Sabah, Malaysia Roslee, Rodeano; Jamaludin, Tajul Anuar; Simon, Norbert
Indonesian Journal on Geoscience Vol 4, No 1 (2017)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.4.1.49-59

Abstract

DOI: 10.17014/ijog.4.1.49-59The topic on Landslide Vulnerability Assessment (LVAs) in Malaysia is relatively new and received little attention from geoscientists and engineers. This research paper tries to formulate the concept of LVAs by taking into account the science and socio-economic aspects. A new approach in vulnerability concept is also introduced herein. To achieve this goal, a framework was designed for assessing the LVAs. The framework was formulated semiquantitatively through the development of database for the risk elements (human and properties) based on information from secondary data (technical reports), extensive review of literature, and field observations. The vulnerability parameters included in assessing LVAs are 1) physical implication (building structures, internal materials, property damage, infrastructural facilities, and stabilization actions), 2) social status (injury, fatalities, safety, loss of accommodation, and public awareness), and 3) interference on environment (affected period, daily operation, and diversity). Each considered parameter in the vulnerability assessment is allocated with a certain index value ranges from 0 (0 % damage/victims/period), 0.25 (1 - 25% damage/victims/period), 0.50 (26 - 50% damage/victims/period), 0.75 (51 - 75% damage/victims/period), and 1.00 (75 - 100% damage/victims/period). All of these parameters are compiled and analyzed with “Landslide Distribution Map” (LDM) to generate a “Landslide Vulnerability Degree map (LVD)”. The LDM was produced based on field studies and satellite image interpretations in order to locate the landslide locations in the studied area. Finally, three types of physical, human, and environment vulnerabilities were then classified into five classes of vulnerabilities, namely: Class 1 (< 0.20): Very Low Vulnerability; Class 2 (0.21 - 0.40): Low Vulnerability; Class 3 (0.41 - 0.60): Medium Vulnerability; Class 4 (0.61 - 0.80): High Vulnerability); and Class 5 (> 0.81): Very High Vulnerability. Results from this study indicate that a further study is needed to the areas of high to very high vulnerability only. This LVAs approach is suitable as a guideline for preliminary development planning, controlling, and managing the landslide hazard /risk in the studied area and potentially to be extended with different background environments.
Geochemistry of Natural Gas Seepages in Boto Area, Bancak, Semarang, Central Java Amijaya, Hendra; Pameco, Pracoyo Adi
Indonesian Journal on Geoscience Vol 4, No 2 (2017)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.4.2.61-70

Abstract

DOI: 10.17014/ijog.4.2.61-70Three seepage gas samples collected from Boto Area, Bancak, Semarang, Central Java, were studied to determine their chemical characteristics using GC and GC-IRMS methods. They are composed 53 - 85% of methane predominantly. However, gas seep Site 3 sample has the highest N2 compound and the lesser extent to the samples Site 2 and Site 1 respectively. The two hydrocarbon gas seeps (Site 1, 2, and Site 3 samples) that are characterized by δ13C methane of -35.61‰ and -27.97‰, and values of δD methane of -112‰ and -109‰ respectively, are each isotopically distinct from all others suggesting, at least, they are derived from different maturity level. The Site 3 gas sample is suggested to be more mature than the others.
Nanggulan Formation and Its Problem As a Basement in Kulonprogo Basin, Yogyakarta Hartono, Hill Gendoet; Sudradjat, Adjat
Indonesian Journal on Geoscience Vol 4, No 2 (2017)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.4.2.71-80

Abstract

DOI: 10.17014/ijog.4.2.71-80Nanggulan Formation consists of the oldest clastic rock sequence exposed in Kulonprogo area, Yogyakarta. This paper discusses the position of Nanggulan Formation as a basement. The method used in this research is surface and subsurface investigations based on gravity surveys. The rock assemblage is exposed and distributed partly in the east flank of Kulonprogo Mountains with weak undulated morphology. The rock sequence is composed of sand to clay grain sizes such as sandstone, quartz sandstone, calcareous sandstone, claystone, fossiliferous claystone, calcareous claystone, siltstone, and coal seam intercalations. The total thickness of the sequence is less than 200 m. Based on the fossil and palynology investigations, previous investigators concluded the age of the rock was Eocene to Middle Miocene. The geological structures developed in the rocks are the lithological stratification, fractures, folding, and faulting. The subsurface interpretation based on gravity data revealed the rock was located under the andesite breccias with 2.44 g/cc density. The density of the rock sequence was 2.63 g/cc. The gravity interpretation shows a strong indication that Nanggulan Formation underlies the andesitic breccias presumably associated with Old Andesite Formation exposed in Kulonprogo Mountains. The limited distribution, the thickness, and the closed environmental deposition of Nanggulan Formation found in the present investigation raised problems on the position of the formation as the basement of Old Andesite Formation occurring in the Kulonprogo Mountain.
Probabilistic Seismic Hazard Analysis Incorporating Monte Carlo Method in the Case of Adelaide Region Setiawan, Bambang
Indonesian Journal on Geoscience Vol 4, No 2 (2017)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.4.2.81-96

Abstract

DOI: 10.17014/ijog.4.2.81-96A topic of seismic hazard analysis (SHA) is briefly elaborated. A probabilistic seismic hazard analysis (PSHA) is commonly used to assess the ground motion level expected with different likelihood at a rock site during a future seismic event. The Incorporating Monte Carlo method into PSHA in an intraplate region (i.e. Adelaide region) is an interesting topic to explore. The result of the analysis using this method is able to characterize the likelihood of seismicity in a targeted region. Furthermore, the results clearly display the seismic ground motions in term of peak ground acceleration and peak ground velocity in Adelaide region. The de-aggregation of the analysis suggests two expected severe events for the Adelaide City. The first expected event is an earthquake M5.2 from a distance of 15 km and 25 km from the city. The second expected one corresponds to an earthquake M6.6 occurring 85 km away from the Adelaide City. However, the results of this analysis must be treated carefully due to dubious seismic data catalogue for a relatively large seismic event in Adelaide region.
ASTER Mineral Classification for Regolith Mapping in Tick Hill Mount Isa, Northwest Queensland Agustin, Fitri
Indonesian Journal on Geoscience Vol 4, No 2 (2017)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.4.2.97-109

Abstract

DOI: 10.17014/ijog.4.2.97-109This paper analyzed the mineral maps of AlOH bearing minerals and iron oxide using ASTER imagery in Tick Hill, Mount Isa, northwestern part of Queensland, as a guide for mapping the regolith unit within the area. Tick Hill is part of the Proterozoic Eastern and Western Fold Belt Province (Mount Isa Inlier Complex) covered by Mesozoic and Paleozoic lithologies and dominated by medium to coarse hornblende-biotite granite and gneiss; both of which intruded during 1760 - 1720 Ma. Highly weathered landforms cover the whole area. The Mesozoic sediments have experienced deep weathering, and currently present in the form of mesas. The weathering profiles are dominated by kaolinite, smectite, and pedogenic carbonates with some secondary silicification. Part of the landform is covered by colluvium varying in thickness from less than 1 m up to 12 m in certain places. Digital image processing has been done to ASTER imagery, i.e: calibrating, mosaicing, and band ratioing and false colour RGB. Within these methods, iron oxide, kaolinite, AlOH, and MgOH group mineral maps have successfully been created through the ASTER imagery. Later, these mineral maps were applied to interpret the surface regolith mapping unit. In addition, field samples have been taken in regolith covered areas to validate the ASTER mineral information.

Page 22 of 80 | Total Record : 796

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