Journal of Geoscience, Engineering, Environment, and Technology
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Analysis of gravity anomaly decomposition and depth to basement, case study: Cenozoic Bogor Basin, Indonesia.
No full textThe Cenozoic Bogor Basin situated on the SE edge part of Sunda shelf is presumed to have hydrocarbon potential on its turbidite deep-water play. The deep subsurface geometry of this basin may play an important role, yet unexplored, to the hydrocarbon exploration. The gravity method is advantageous to illuminate the subsurface structure on the arbitrary depth and various sources. Eight-hundred-thirty-eight points of ground-based gravity survey were collected on roughly one kilometer spacing in the North of Bandung to Pamanukan region covering the Cenozoic Bogor Basin on the Subang-Purwakarta segment to generate complete Bouguer anomaly (CBA) map. This study examines the two robust methods of gravity anomaly decomposition (i.e., polynomial trend surface and upward continuation) by using multiple parameters to match the geological background. Radially averaged power spectrum was used to estimate the depth of anomalous source corresponds to the top of basement layer and resulting 4 km basement depth in North West Java basin and below 1 km on Tangkuban Parahu volcanic zone. The resulting estimated depth of Cenozoic Bogor Basin was evaluated by the matched a priori published data on those two areas and revealed the depth of depocenter (deepest sediment) on the Cenozoic Bogor Basin is up to 9 km, quite a deeper extent than previously assumed
Comparison of Granitoid Characteristics West Kalimantan and Karangsambung Based On Mineralogical And Geochemical Aspects
Full text linkIndonesia was included in the ring of fire so that it has various types of tectonic products, one of which is granitoid. Granitoid is very complex rock and many are found in Indonesia. Some of them are found in West Kalimantan and Karangsambung. Basis of the reasearch is there is no research that compares granitoid in two regions. The purpose of this study was to compare rock characteristics and granite petrogenesis of West Kalimantan and Karangsambung. The research method used was collecting data on field, also laboratory analysis of rock samples using a polarization microscope, refraction microscope, and X-Ray Fluorescence analysis. The mineralogical characteristics of each study area tend to be almost the same. The predominant composition of the main minerals is quartz, plagioclase and orthoclase. But specifically the rock samples from West Kalimantan have been altered from phylic-silicification-propylitic. The entire study area contained accessory minerals, namely apatite, zircon, titanite, and for monazite only in the West Kalimantan sample. There was mineralization up to the supergene stage in the presence of the characteristic minerals for the supergene covelite and chalcocytes in the West Kalimantan sample. Geochemical analysis of both regions shows the same magma affinity, namely Calc Alkaline - High K Calc Alkaline. For West Kalimantan, the value of A / CNK <1.1 has a type metaluminious and > 1.1 a type peraluminious. Meanwhile, Karangsambung A / CNK value <1.1 has a type metaluminious. So that West Kalimantan granite has two I-type and S-type. While Karangsambung is I-type. West Kalimantan granite is formed in continental arc granite (CAG) and continental collision granite (CCG). Meanwhile, Karangsambung in Volcanic Arc Granite (VAG). It can be concluded that the granites of the two regions have quite different characteristics even though they belong to a relatively similar tectonic environment
The Geomorphological Factors and Its Implications for The Tidal Energy Installations in Java, Indonesia
Full text linkThis study aims to place the tidal energy installation effectively in Indonesia based on geomorphological factors. The survey method was used to analyze the characteristics of beaches in Indonesia. Mathematical physics model was implemented to find the new formulas based on geomorphological factors. Tides are the result of gravitational attraction and the centrifugal effect, which is the drive In the earth-moon system, tidal generating forces are the resultant forces that cause tides, namely: the earth-moon system (FS) centrifugal force and the moon's gravitational force (FB). FS works in the center of the mass of the earth-moon system whose mass point is located on the 3/4 radius of the earth. The style of tidal generator caused by the moon can be calculated by combining Newton's universal gravitational law .The results of this study consist of F = m ac, where the style of the tidal generator caused by the moon can be calculated by combining newton's universal gravitational law in equation and newton's second law of motion in Equation. The another results is tan = , where the formula takes into account constants (K) based on slopes. The last result is the constants (K) for each land form starting on 0,00 untill 1,00. The north coast of Java is more suitable for tidal energy installations because the land form is dominated by alluvium plains of the quaternary age with a lower risk than the southern region of Java. The effectiveness of tidal energy installation depends on the characteristics of the land form. In alluvial plains, the quaternary age of the alluvial plains is more suitable than the hill form volcanic quaternary, tertiary volcanic, and tertiary holokarst
Diagenesis Study of Jatiluhur Formation at Cipamingkis River, Bogor Regency, West Java, Indonesia
Full text linkDiagenesis studies in the Jatiluhur Formation are still relatively new, especially in the Cipamingkis River. This research can provide information in the form of components and characteristics of sandstone in the Jatiluhur Formation which can be used as a basis for further research or useful information in the oil and gas industry. Knowledge of diagenetic could be one of the factors that affect in raservoir quality, espesially in sandstone. In this study, data collection was carried out through surface mapping, which is 55 rock samples were obtained from stratigraphic measuring section with a path length of ±2 Km in the Cipamingkis River. The data is in the form of information on sedimentarry structure, textures and composition. There were 23 sandstone and 2 limestone samples which were then subjected to petrographic analysis, X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results of study are several features of diagenesis were found including compaction that works in the form of point contact, long contact, concavo-convex contact and suture contact and dominated by mechanical compaction, while in limestone there is a brittle fracture feature in bioclasts. The cement found in the form of calcite cement, quartz and clay minerals that the form of kaolinite, smectite and illite, while the limestone is in the form of blocky and fibrous to bleded which is filled with calcite minerals. Dissolution occurs in the minerals of quartz, feldspar, and mica. The mineral replacement that is commonly found occurs in quartz and feldspar minerals. In limestone, there is an intergranular micritization. The dominant type of porosity found was interparticle with an average of 10.4% found between 3 – 23%. The history of diagenesis that occurs in rocks in the Jatiluhur Formation begins with the initial deposition of eogenesis, followed by burial mesogenesis and ends with telogenesis which reveals rocks on the surface
Understanding Mud Volcano System Using Hele-Shaw (H-S) Experiment: Seismic Confirmation at East Java Mud Volcano
Full text linkNumerous researchers have carried out studies on the mud volcano system in East Java. However, there have been no experiments on the mud volcano system's mechanism, including overpressure confirmed by direct subsurface data. Therefore, this study aims to directly evaluate the mud volcano system's mechanism using the Hele-Shaw (H-S) experiment with the subsurface data confirmation. The H-S experiment utilized four primary materials: quartz sand diameter below 250 µm and 320 µm to analogize the porous layer. Gypsum flour clay is the ductile layer, while mud from the Kuwu and Kesongo Mud Volcanoes is the original material from nature. Wax represents impermeable material. The sealing layer is made of wax, and oxygen represents the natural fluids of the rock formation. The overpressured zone is created by pumping oxygen into a layer of quartz sand covered by a wax as an impermeable layer. Pressure is measured digitally, and the process is continuously recorded to produce traceable data. Each material was experimented on individually to determine the critical phase characteristics, valve fault structure geometry, and validation with seismic interpretation. The results indicate that the critical phase of the mud volcano system is characterized by the dome structure at the surface, with high intensify of gas and oil seepage. Piercement structure geometry is shown by plumbing of fluidization zone, which becomes shallower than before. Furthermore, each material's piercement structure geometry shows a consistent pattern, with differences in the density of the fault and pressure structures. Thus, the H-S experiment's validation with seismic interpretation shows a similar geometry in pressure structures and valve faults as the mud volcano system's migration paths
Evaluation of Groundwater Quality Status Around Gunung Tugel Landfill In Kedungrandu Village, Patikraja District, Banyumas Regency, Central Java, Indonesia.
No full textGunung Tugel Disposal Site (GTDS) is one of the final land disposal sites established in 1983 in the Banyumas Regency, and it operates with an open-dumping system. In this system, the base of the disposal site is neither coated with an impermeable layer nor equipped with leachate collection and drainage channels, for which leachate can percolate through the soil and pollute groundwater. In March 2016, GTDS was closed because its capacity had been exceeded. The closure of GTDS was not followed by appropriate waste and environmental management, prompting the formation of leachate that can contaminate the environment, particularly groundwater. This research set out to identify the leachate quality of GTDS, assess the groundwater quality, and determine the groundwater quality status around the disposal site. It employed a field survey and mapping to plot and display the groundwater well points in the study area, laboratory analysis to identify the groundwater quality, and pollution index calculation to determine the groundwater quality status. The groundwater samples were tested in the laboratory for their physical (turbidity and TDS), chemical (pH, COD, BOD, iron (Fe), cadmium (Cd)), and biological properties (total coliform). The results showed that the cadmium (Cd) levels in several groundwater well points had exceeded the quality standards. Based on the analysis and calculation results, the groundwater quality status in the study area is mildly contaminated, with the pollution index ranging between 2.571 and 4.099
Geology, Rock Geochemistry and Ore Fluid Characteristics of the Brambang Copper-Gold Porphyry Prospect, Lombok Island, Indonesia.
No full textBrambang is one of the porphyry copper-gold prospects/deposits situated along eastern Sunda arc. This study is aimed to understand geological framework, alteration geochemistry and ore fluid characteristics of the prospect. Fieldworks and various laboratory analyses were performed including petrography, ore microscopy, rock geochemistry, chlorite chemistry and fluid inclusion microthermometry. The prospect is composed of andesitic tuff and diorite which are intruded by tonalite porphyries. Tonalite porphyries are interpreted as ore mineralisation-bearing intrusion. Various hydrothermal alterations are identified including potassic, phyllic, propylitic, advanced argillic and argillic types. Ore mineralisation is characterized by magnetite and copper sulfides such as bornite and chalcopyrite. Potassic alteration is typified by secondary biotite, and associated with ore mineralisation. Mass balance calculation indicates SiO2, Fe2O3, K2O, Cu and Au are added during potassic alteration process. Ore forming fluid is dominated by magmatic fluid at high temperature (450-600ºC) and high salinity (60-70 wt. % NaCl eq.). Hydrothermal fluid was diluted by meteoric water incursion at low-moderate temperature of 150-400ºC and salinity of 0.5-7 wt. % NaCl eq
Shallow Aquifer Groundwater Facies At Multiple Landuse Sites In Manglayang Volcanic Area, Jatinangor And Surroundings, Indonesia
Full text linkManglayang Mountain is generally composed by old and young volcanic materials. Older rocks are located around the northern part of mountain peak, in medial and distal parts. In the southern and southeastern parts composed by relatively young volcanic rocks starting from the proximal, medial to distal. These geologic conditions produce diverse aquifer systems. These differences in land use environments contribute to water quality conditions in local shallow aquifers. The research is therefore carried out in order to the effect of difference in land use environments on groundwater facies by dividing the area based on each land use. Land use in the research area is dominated by allotment of agricultural land, settlement, and industry. The study was conducted from the medial area to distal to the southern part of Manglayang Mountain, administratively including Sukasari, Jatinangor, and Rancaekek districts. To observe the groundwater conditions in the aquifer from the study area, physical and chemical parameters were tested. Chemical parameter test results were plotted using piper diagrams and Durov diagrams as a method that can illustrate the condition of groundwater facies. Physical characteristics of groundwater may reflect groundwater interactions with rocks. Measurable TDS concentrations of 48 - 299 mg / L and measured EC 100 - 1020 μmhos / cm, show different interaction conditions between groundwater with rocks or have received different material subsidies. Similarly, the occurrence of temperatures that vary considerably between air and water indicates the distance of groundwater sources with various water bodies. The groundwater facies that developed in the research area are generally dominated by Ca, HCO3 in the agricultural land use area, Mg, HCO3 in the settlement area, and in some Cl-facing evolving places in the industrial land use zones. In addition, there are also indications of mixing of anions and cations in groundwater samples in all three land use areas. This indicates that there has been a change in groundwater characteristics in some areas of land use utilization in the research are