Journal of Geoscience, Engineering, Environment, and Technology
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Identification of Geothermal System In “Diana” Area, Indonesia Based On Magnetotelluric Data Modelling
Full text linkThese days, the number of geothermal explorations is being increased to obtain a greater new potential of geothermal energy. One of the methods that is often used is magnetotelluric (MT). By MT, the components of a geothermal system can be delineated based on the resistivity values. This research’s main purpose is MT data modelling in 1 D and 2 D to delineate the geothermal system in the research area. There are 18 point of soundings, with a distance of about 1 – 3 km for each point. Bostick Transformation is used in 1 D modelling while Non-Linear Conjugate Gradient inversion is used as 2 D modelling with L – curve analysis as a method to obtain an optimal value of regularization parameter. Based on the analysis of 1 and 2 D models, the caprock zone was identified with a resistivity value of < 50 Ωm at a depth of 500 m with a thickness of about 250 m. The reservoir zone was identified with a resistivity value range of (50 – 100) Ωm located at a depth of 1000 with a thickness of about 500 m. Also, fault structures have been identified at the center of the research area. The regularization parameter used for the 2 D modelling is 5, which has obtained RMS values of 2.25% and 2.21% for each line
Assessment of Geosite and Geomorphosite at South Solok Aspiring Geopark Area
Full text linkSouth Solok is one of the five districts designated as the aspiring of the Ranah Minang Geopark. Various reliefs and geological structures cause the diversity of landscapes to be an attraction for tourists and ecosystems with biodiversity. The study intends to identify geosite and geomorphosite in the South Solok area with field observations to describe the state of geology, geomorphology of geosite sites, and geomorphosite. Site assessment is carried out quantitatively with five assessment parameters; scientific, educational, functional, tourist, and posting activities on tourist sites on social media. Field observation found 17 sites classified into four groups, specifically waterfalls, manifestations of hot springs, geomorphological landscapes, and caves. Based on the results of the highest value representation obtained by the Batukapal Cave sites with a value of 44.86% and the lowest at Timbulun Waterfall at 0.1%. Of the 17 sites, four sites are considered the main sites in the research area: Suliti Waterfall, Sapan Maluluang Hot Spring Manifestation, Batukapal Cave, and Camintoran
Serpentinization Study On Ultramafic Rock at Morombo Area, Lasolo Islands District, North Konawe Regency, Southeast Sulawesi, Indonesia
Full text linkThe research is in Morombo area, North Konawe Regency, Southeast Sulawesi. The purpose of this study was to determine the characteristics of serpentinized ultramafic rock and serpentine paragenesis. Research was conducted using field observations and laboratory analysis consisting of petrographic and geochemical analysis in the form of X-Ray Fluorosence (XRF). Petrographic analysis was carried out to identify the mineral content and textures in the rock and to determine the percentage of serpentine mineral presence. Both of these rocks are petrographically dominated by primary minerals olivine and clinopyroxine and secondary minerals namely lizardite, chrysotile, antiorite and opaque minerals. The XRF analysis was to determine the elements of Ni, Fe, Co, MgO, SiO2, CaO, Al2O3 and P in ultramafic rocks. The results of petrographic analysis show that serpentinized ultramafic rocks in the study area consist of serpentinized dunite and serpentinized peridotite. The formation of clay minerals in rocks does not occur because of the low serpentinization process in the rock. The results of XRF analysis showed that all samples in the bedrock showed Ni content above 0.2%. This is caused by the enrichment of Ni which is interpreted as a result of the serpentinization process along with the formation of lizardite in the rock. The serpentinization sub-processes in the study area comprised by hydration, serpentine recrystallization, and deserpentinization. Serpentine paragenesis is formed from the mid-oceanic ridge ocean floor, the orogenic phase to weathering. Substitution of Mg by Ni in ultramafic rocks will produce Ni-Serpentin. It is estimated that in the research area lizardite and chrysotile lizardite and chrysotile are the causes of Ni enrichment in bedrocks. The serpentinization characteristics of ultramafic rocks in the study area show a low to moderate level of serpentinization
Analysis of Grain Morphology, Mineral Composition, and Ore Grade on Gold Placer Deposits in Bantimurung, Pangkep Regency, South Sulawesi, Indonesia
Full text linkThe information through social media shows that there is quite an intense placer mining activity by local residents in the Bantimurung area, Tondong Tallasa District, Pangkep Regency. This study as a preliminary research aims to determine the grain morphology characteristics of mineral composition and metal grade in gold placer deposits in the study area. The data collected were eight samples. The collected samples were prepared into thin section, polished and observed using a microscope to identify the mineral composition and grain morphology. The grades of Au metal and its associated metals consisting of Ag, Zn, Pb, and Cu in the placer samples were analyzed by the AAS method. Petrography shows abundant of quartz, plagioclase, biotite and pyroxene minerals it might be indication of mineralization of epithermal. Ore petrography shows pyrite present along the river, silver is also found quite a lot along the river. Meanwhile, covellite, magnetite, sphalerite, and garnet were found only slightly at the sampling station this mineral composition indicates that the source of the placer deposits was epithermal. The grain morphology of the thin-section observation shows that quartz dominant has a high sphericity with character of roundness tends to be very angular to sub-rounded from upstream to downstream of the river. Plagioclase tends to have sub rounded roundness and high sphericity. Biotite tends to have a high sphericity with roundness from upstream to downstream is very angular, then angular, then sub-rounded. Pyroxenes tend to have high sphericity with very angular and angular roundness. Au content is directly proportional to Cu and inversely proportional to Zn, Pb, and Ag. Statistically Au affects the content of Cu by 50.97%. It can be concluded that Au is genetically associated with Cu, however Au grains that were still attached to the mineral and had not been separated from other minerals so that it could not be seen visually. This can also indicate that the source of this placer deposit is not far from the study site. Au grade corelated with stream sediment types it is 97,86 ppm for channel bar and 94,16 ppm for point bar, based on this we conclude the downstream has higher grade of Au compare to the upstream
Morphotectonic Control of Land Movements at Wundulako Region, Kolaka Regency, Southeast Sulawesi Province, Indonesia
Full text linkThis research is located at Wundulako District, Kolaka Regency, Southeast Sulawesi Province. The purpose of this study are to determine the level of tectonic activity and the effect of tectonic activity on the land movement of the study area. Based on the DEM (Digital Elevation Model) analysis, geomorphology of the study area is dominated by mountains unit that indicate the influence of tectonic activity. Geomorphological aspects were analyzed to determine the tectonic classes in the study area such as watershed and non-watershed analysis. The results showed that, tectonic class of the study area is classified as very high and moderate tectonic class. The effect of tectonic class level on land movement in the study area shows a least correlation. This interprets that the cause of land movement at study area is not only influenced by tectonic factors but is also influenced by other factors such as rainfall, lithological conditions, geomorphology, earthquakes, and human activities. This shows that morphotectonic control has little effect on the land movements at Wundulako District, Kolaka Regency, Southeast Sulawesi Province, but is also influenced by other factors such as rainfall, lithological conditions, geomorphology, earthquakes, and human activities
The Effect of Weathered Layer Thickness and Slope on Potential Areas of Landslides in Gerbosari Village, Samigaluh District, Kulonprogo Regency, Indonesia
Full text linkGerbosari Village has a history of landslides with intensity and risk of 56 occurrences over 5 years. Gerbosari Village, Samigaluh District, Kulonprogo Regency is located at geographic coordinates 7◦ 38 '45.33 "- 7◦ 41' 35.24" LS and 100◦ 9 '20.80 "- 110◦ 11' 16.52" BT with topographic conditions at an altitude around 500 - 1000 mdpl. This study aims to determine the subsurface structure of landslide-prone areas in the form of weathered layer thickness and the effect of slope in landslide-prone areas so that it can be used in making micro zonation maps of landslide-prone areas. This study uses 43 microtremor data with a distance between points of 650 m. The microtremor signal was analysed using the horizontal to vertical spectrum ratio ( HVSR) method. From the measurement results, it is obtained that the value of the dominant frequency ranges from 1 - 22 Hz, the value of the amplification factor is obtained in the range of 1 - 10.5, the value of the peak ground acceleration ranges from 60 - 300 cm/s2, the thickness of the weathered layer is obtained in the range of 12 - 22 meters. Based on the results of the slope analysis, the study area is on a slope classified as a bit steep - very steep
The Petrology and Volcano-Stratigraphy of The Muria-Peninsula High-K Volcanic Rocks, Central Java, Indonesia
Full text linkThe Muria-Peninsula is a Quaternary volcano located in the northern Sunda arc. Its activity was controlled under high potassic and very high potassic magma series resulting in leucite-rich trachyte and pyroxene-rich basaltic-andesite. It is a strato-type volcano that is composed of lava, breccia, and tuff layers, and some dikes have some volcanic craters and maars varying in age and composition. The study area is covering the volcanoes of Muria, Genuk, and Patiayam. This paper aims to describe the petrology, mineralogy, and volcano-stratigraphy of the different volcanic materials. The data and materials were sourced from the primary and secondary data. The methods are field mapping, stratigraphy measurements, collecting samples, thin section analyses, and major element geochemistry using X-Ray fluorescence (XRF). The results describe two groups of volcanic rocks consisting of pyroxene-rich andesitic-basaltic volcanic materials and leucite-rich trachytic volcanic materials. Augite presents in the andesitic basalt together with small grains of olivine and a few anorthite and foid minerals. Aegirine (Na-Pyroxene) is present in the leucite-rich trachyte that is often associated with biotite and hornblende. Na-Ca Plagioclase such as labradorite-andesine is often present in the basaltic-trachy-andesite that is usually rarely leucite. The major elements show high-K volcanic rocks with % K2O is 4-5.9% and very high-K volcanic rocks (with % K2O is between 6-8.24%) and low-K volcanic rocks that contain % K2O is 2-3,9%. There are two groups of high-K to very high-K volcanic materials consisting of silicic-rich volcanic materials (~57-64% of SiO2) and low-silicic volcanic materials (~46-50%). The TAS diagram identifies tephrite, phonolite, and trachyte. Stratigraphic data identifies calcareous sediments of the Bulu Formation as the basement rocks of the Muria trachyandesite. Beds of pumice-rich volcanic breccia of the Ujungwatu Formation are the basement rocks of the basanite-tephrite of the Genuk Volcano, and the tuff of the Ujungwatu is also exposed consisting of the basanite-tephritic-phonolite of the Patiayam Volcano. The leucite-like feldspars are very common in the andesite lava and dikes that compose the crater of Muria. Most of the Muria volcanic materials are rarely in leucite, while some maars contain pumice-rich pyroclastic flows and basaltic lava. The results of the major elemental analysis of the Muria materials indicate that the rock tends to be of medium to high K affinity (~2% K2O). The Genuk and older Muria are consisting of leucite-rich tephrite-phonolite. It was two periods of magmatic series developed in the Muria-Peninsula that was resulting in the high-K to very high-K magmatism and the medium K Kalk-alkaline magmatism
Characteristics and Potential of Placer Gold Deposit in Lakan Bilem Block, West Kutai District, East Kalimantan, Indonesia
Full text linkKalimantan is recognized as one of Indonesian islands with huge prospect of minerals particularly gold both primary and secondary deposit styles. However, the publication of the gold resources is still restricted to be described in regional/district scale maps or exploration company internal reports, hence, a detailed study on deposit scale remains limited. This study is aimed to document the characteristics and the estimation of potential or resources of the secondary (placer) gold deposit in Lakan Bilem block, West Kutai district, East Kalimantan province, Indonesia. The study was done by field observation followed by microscopic analysis and simple resources estimation of the gold. Gold in the study area occur in the semi-consolidated paleo alluvial deposit as trace mineral. The gold morphologies show platy to angular form with coarse surface which indicates the process of gold deposition is predominantly controlled by hydrodynamic transportation at a relatively moderate regime. Estimation of the indicated resources of gold results a total of 4.96 tonnes of gold potentially occurred in the study area. Exploration drilling with 100 spacing grid is suggested to delineate lateral and vertical distribution of the gold deposit. The drilling also will upgrade confidence level of the resources from indicated to measured resources