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IJOG : Indonesian Journal on Geoscience

IJOG
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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 Evidence of Island-Arc Origin for Sumatra Island; A New Perspective based on Volcanic Rocks in Lampung Province, Indonesia Iskandar Zulkarnain
Indonesian Journal on Geoscience Vol 6, No 4 (2011)
Publisher : Geological Agency

DOI: 10.17014/ijog.v6i4.128Since decades, Sumatra Island is considered as the Eurasia continental margin where the Indian Ocean plate has been subducted oblique beneath the continental plate of Sumatra. But, the occurrences of volcanic rocks in almost all areas of Lampung Province in the southernmost of Sumatra Island, as the presence of the Quaternary Tanggamus Volcano in the western part of the province together with the Quaternary Rajabasa Volcano in the eastern area cannot be justified using the consideration. Spider diagrams of trace and rare earth elements of volcanic rocks from the western and eastern areas of the province reveal that the rocks come from three different tectonic settings, namely island-arc, active continental margin (ACM), and intra continental plate. All basalt and one dacite of western volcanic rocks show a character of island-arc origin, while the eastern volcanic rocks are reflecting characters of ACM and intra continental plate. Plot of the rocks in the diagram of Ta/Yb versus Ce/P and in Ta/Yb versus Th/Yb confirmed the tectonic environments and specifically classify the intra continental plate into Within Plate Volcanic Zone (WPVZ). The island-arc group is characterized by Ta/Yb ratio of less than 2.0 and Ce/P less than 1.8. The ACM group is recognized having Ta/Yb ratio between 2 and 4 with Ce/P more 1.8, while the WPVZ group is defined as a group having Ta/Yb more than 6 and Ce/P more than 1.0. The result indicates that the western part of Sumatra is an island-arc fragment and the eastern part belongs to the Eurasia continental margin. The concentration of volcanics having ACM character from areas around the Sumatra Fault System to the east indicates that the collision zone between the Sumatra island-arc fragments with the Eurasia continental margin is probably located along the SFS. More statistical data is still needed from other Sumatra volcanics to confirm this conclusion.

Modelling of Magma Density and Viscocity Changes and Their Influences towards the Characteristic of Kelud Volcano Eruption Hanik Humaida; K. S. Brotopuspito; H. D. Pranowo; narsito narsito
Indonesian Journal on Geoscience Vol 6, No 4 (2011)
Publisher : Geological Agency

DOI: 10.17014/ijog.v6i4.129The effusive eruption of Kelud Volcano in 2007 was different from the previous ones, which in general were more explosive. Among others, density and viscosity are factors that determine the type of eruption. Therefore, the study on the difference of the recent eruption style based on the density and viscosity of magma was carried out. The method used in this study was based on geochemical analysis of the rock and then a modeling was established by using the above parameter. The study on the explosive eruption was emphasized on the data of 1990 eruption, whereas the effusive eruption was based on the data of 2007 eruption. The result shows that the magma viscosity of Kelud Volcano depend on the H O concentration as one of the volatile compound in magma, and temperature which gives the exponential equation. The higher the increase of H O content the smaller the value of its viscosity as well as the higher the temperature. The H O content in silica fluid can break the polymer bond of the silica fluid, because a shorter polymer will produce a lower viscosity. The density of the silica content of Kelud Volcano ranges between andesitic and basaltic types, but andesite is more likely. The fluid density of the material of 1990 eruption is different from 2007 eruption. Compared to the 2007, the 1990 eruption material gave a lower density value in its silica fluid than that of the 2007 one. The low density value of the silica fluid of the 1990 eruption material was reflecting a more acid magma. The level of density value of silica fluid depends on its temperature. At the temperature of 1073 K the density of the 1990 Kelud magma is 2810 kg/m3 and the 2007 magma is 2818 kg/m3, whereas at a temperature of 1673 K, the density is 2672 kg/m3 and 2682 kg/m3 of the 1990 and 2007 eruptions respectively. A modeling by using an ideal gas law of Henry’s Law illustrated that the ascent of Kelud’s magma to the surface may cause changes in it’s physical properties. The evolution of the flow pressure in the conduit is characterized by three different areas; based of the conduit until the pressure is saturated, then at the level between release and fragmentation, and then the level above the fragmentation, that implicates the decrease in the wall friction.

Experiment of Industrial Waste Absorption using Activated Carbon from Coal of Tanjung Tabalong, South Kalimantan M. Ulum Gani; Widodo Widodo
Indonesian Journal on Geoscience Vol 6, No 4 (2011)
Publisher : Geological Agency

DOI: 10.17014/ijog.v6i4.130Activated carbon made from Tanjung Tabalong coal was investigated its absorption capability to organic and inorganic elements in industrial waste. Coal was carbonized at low temperature of 600C to produce semicoke, and then was activated at temperature of 700C with activation time of 120 minutes with water steam flow. The absorption capability of activated carbon to chemical oxygen demand (COD) was performed using 2.5 and 9.0 g activated carbon for 250 ml and 300 ml COD waste respectively. The agitation time of each experiment were 30, 60, and 90 minutes. Atomic absorption spectrophotometer (AAS) was used to analyze the COD waste. The result shows that 2.5 g activated carbon could absorb COD waste ranging from 6.9-67.5 %, while the utilization of 9 g could absorb COD waste ranging from 88.9 - 100 %. The more activated carbon and the longer time of agitation used in this experiment, the more the absorption of COD waste.

3-D Imaging of Cleat and Micro-cleat Characteristics, South Walker Creek Coals, Bowen Basin, Australia: Microfocus X-ray Computed Tomography Analysis Asep Kurnia Permana
Indonesian Journal on Geoscience Vol 7, No 1 (2012)
Publisher : Geological Agency

DOI: 10.17014/ijog.v7i1.131The Permian coals of the South Walker Creek area have a moderately to highly developed cleat system. The cleat fractures are well developed in both bright and dull bands, and generally parallel, inclined or perpendicular to the bedding planes of the seam, with the spaces open or filled by mineral matter, such as clay and carbonate minerals. Microfocus X-ray computed tomography (CT) technique was performed to identify cleat characteristics in the coal seams. This technique allows visualizing of microcleat distribution and mineralization in three dimensional images. Cleat mineralization in the coal seam occurs either as single mineral (monomineralic) or intermixed mineral (polymineralic) masses. The cross cutting relationship was shown by X-ray CT scan analysis. The timing of microcleat formation in the coal seam from early to late is carbonate minerals, clay minerals (kaolinite) plus minor high density (rutile or anatase) phases. Thus, a high resolution of microfocus X-ray CT does not only provides a better visualization, but also could identify microcleat orientation, cleat mineralization, and generation of microcleat.

Evolution of Rajabasa Volcano in Kalianda Area and Its Vicinity, South Lampung Regency Sutikno Bronto; P. Asmoro; G. Hartono; Sulistiyono Sulistiyono
Indonesian Journal on Geoscience Vol 7, No 1 (2012)
Publisher : Geological Agency

DOI: 10.17014/ijog.v7i1.132Rajabasa Volcano (± 1281 m) and Lampung Tuff, located in the South Lampung Regency, is the main point in order to understand the evolution of Quaternary volcanism in the area. A remote sensing analysis and field geologic work are the methods of the study. The volcanism began with the construction period of the Pre-Rajabasa composite cone which was followed by the destruction period of the cone to form the Pre-Rajabasa Caldera having ca. 25 km in diameter. The present Rajabasa Volcano, along with cones of flank eruptions and monogenesis, has appeared in the Pre-Rajabasa Caldera depression. Those volcanic activities are considered as the second construction period. During the first and the second construction periods, basaltic to andesitic lava flows, pyroclastic breccias, and tuffs were erupted. The Rajabasa eruption points moved in WNW - ESE direction, which were possibly controlled by a subsurface weak zone. The Pre-Rajabasa Caldera erupted voluminous Lampung Tuffs having rhyolite in composition, and they are considered as a combination of pyroclastic falls, flows, and surges, or pyroclastic density currents.

Engineering Geological Investigation of Slow Moving Landslide in Jahiyang Village, Salawu, Tasikmalaya Regency Dwi Sarah; M. R. Daryono
Indonesian Journal on Geoscience Vol 7, No 1 (2012)
Publisher : Geological Agency

DOI: 10.17014/ijog.v7i1.133An understanding of landslide mechanism is imperative to determine the appropriate mitigation method. The slow moving landslide (creeping) which occurred in Kampung Salawangi, Jahiyang Village, Salawu Subregency, Tasikmalaya had caused economical and environmental losses due to the frequent active movement particularly following rainfall events. Engineering geological investigation and slope stability analysis were carried out in the studied area in order to elucidate the mechanism of the landslide. The engineering geological investigation consists of local topographical mapping, geotechnical drillings, hand borings, cone penetration, and laboratory tests. The slope stability assessment of the recent landslide was conducted by a finite element method. The results of engineering geological data analysis show that the studied area is composed of residual soils of soft to firm sandy silt and loose to compact silty sand and base rock of fresh to weathered volcanic breccias with groundwater level varying between 3 - 16 m. The engineering properties of the residual soils indicate that the sandy silt is of high plasticity and the shear strength properties of the sandy silt and silty sand show low value with effective cohesion of 6.0 - 21.74 kPa and effective friction angle of 12.00 - 25.980. The assessment of slope stability shows that the stability of the studied area is largely influenced by the rise of groundwater level marked by the decrease of safety factor and increase of slope displacement.

Morphostructure Control Towards the Development of Mahawu Volcanic Complex, North Sulawesi S. Poedjoprajitno
Indonesian Journal on Geoscience Vol 7, No 1 (2012)
Publisher : Geological Agency

DOI: 10.17014/ijog.v7i1.134The studied area, situated in northeastern part of North Sulawesi Arm, is dominantly occupied by the Mahawu, Linau, Tompusu, and Kasurutan volcanic rocks. Using remote sensing data, such as landsat image, black and white panchromatic aerial photograph, and IFSAR image, morphology-origin unit and morphology lineament can be interpreted. Four morphology-origin units, those are Mahawu Volcano Complex, Intra-montane Plain structure, Linau Volcano Complex, and Lacustrine Plain are recognized. Furthermore, morphological lineament pattern was statistically processed to find out the general stress direction in the area to determine the probability of the structural morphology occurrence in the Mahawu Volcano Complex. The result shows that generally the development pattern of volcanic cones are irregular, except the Mahawu Volcano Complex showing a linear pattern. This lineament pattern is interpreted as a NW - SE fault pattern controlling the rise of magma. At least, two tectonic and two eruption periods occurred regularly at different time from the Quaternary age till the present.

Tsunami Characteristics along The Coast of Biak Island based on the 1996 Biak Tsunami Traces Yudhicara Yudhicara
Indonesian Journal on Geoscience Vol 7, No 1 (2012)
Publisher : Geological Agency

DOI: 10.17014/ijog.v7i1.135Identification on tsunami traces had been conducted along the coast of Biak Island, Papua, to recognize the character of tsunami potential in this region, referring to the 1996 tsunami event. This study is to observe the influence of tsunami to the environment and tsunami character itself which can be learned from tsunami deposit. According to the 1996 Biak tsunami run up distributions, it can be observed that the maximum tsunami run up was found at the coast which has an undulating to steep morphology rather than other places which has a relatively flat one. The 1996 Biak Tsunami arrival times were approximately between 10 and 15 minutes, such as at the northern and southern coasts of Biak, except for the western one which is about 1 to 5 minutes. This was influenced by the local bathymetry and another possible source triggering tsunami such as a local submarine landslide. The number of tsunami waves were between 2 and 4, and the second one was usually the highest. Based on a sedimentological analysis, the 1996 tsunami deposit is characterized by the dominant coarse sand, while grain size distribution curve shows a character of transportation process similar to an ordinary beach process dominated by saltation current. The foraminifera fossil content tends to indicate that the tsunami deposit was derived from > 200 m seafloor depth (bathyal zone).

The Paleo-Orientations of Northwestern Borneo and Adjacent South China Sea Basins H. D. Tjia
Indonesian Journal on Geoscience Vol 7, No 2 (2012)
Publisher : Geological Agency

DOI: 10.17014/ijog.v7i2.136Limited paleomagnetic data from West Kalimantan and southwestern Sarawak appear to indicate counter-clockwise (CCW) rotation of over 50 degrees during Cenozoic. On the other hand, similar studies from Sabah show conflicting results in terms of paleo-positions. This CCW information and other plate tectonic considerations have formed the base of Southeast Asia’s plate reconstructions that have seen print in a number of updated versions. The existing publications on extensive field and exploration data, including geological stress fields from wellbore breakouts, on northwestern Borneo and basins of South China Sea have not been taken into account. The latter wealth of information already established that the region under discussion consists of a mosaic-like assemblage of diverse tectono-stratigraphic terranes, each with separate tectonic development. Stress fields changed in different ways in the different terranes indicating definitively that regional, progressive CCW rotation of Borneo is not possible.

Thermal and Infrared Studies of Garnierite from the Soroako Nickeliferous Laterite Deposit, Sulawesi, Indonesia Sufriadin Sufriadin; Arifudin Idrus; S. Pramumijoyo; I. W. Warmada; I. Nur; A. Imai; A. M. Imran; Kaharuddin Kaharuddin
Indonesian Journal on Geoscience Vol 7, No 2 (2012)
Publisher : Geological Agency

DOI: 10.17014/ijog.v7i2.137Mineralogical characterization of some garnierite samples from Soroako have been conducted using X-ray diffraction, thermal analysis, and infrared spectroscopy methods. XRD patterns reveal the samples mainly containing the mixture of kerolite (talc-like phase) and serpentine with minor smectite, sepiolite, and silica. Thermal analyses of garnierite samples indicated by DTA curves are in good agreement with patterns that have been reported in literature. Three endothermic peaks normally occur in the ranges between 58º C and <800º C illustrating three steps of weight losses: adsorbed, bound, and hydroxyl/crystal water. One additional weight loss in low temperature region of sepiolite is corresponding to the lost of zeolitic water. Infrared spectra appeared in 3800 - 3200 cm-1 region generally exhibit broad absorption bands, indicating low crystallinities of studied samples and can be assigned to the presence of hydroxyl group bonded to octahedral coordination mainly Mg atom. The bands observed at 1660 cm-1, 1639 cm-1, 1637 cm-1, and 1633 cm-1 in all samples indicate water molecules. FTIR spectra displaying the strong bands at 1045 cm-1, 1038 cm-1, and 1036 cm-1 could be related to the presence of Si-O-Si bonds linking to tetrahedral coordination. The strong absorption bands appeared at 511 cm-1, 505 cm-1, 499 cm-1, and 496 cm-1 in respective samples are attributed to divalent cation bonds (e.g. Mg, Ni-O). Both TG/DTA and FTIR seem to be the powerful tool in diagnosing the crystal chemistry of garnierite which is mainly composed of phyllosilicate minerals.

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Contact Name
Ivan Ferdian

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ivan.ijgbg@gmail.com

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Journal Mail Official
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Location
Kota bandung,

Jawa barat

INDONESIA