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Journal of Applied Geology
ISSN : 25022822     EISSN : 25022822     DOI : https://doi.org/10.22146
Journal of Applied Geology – JAG focuses on the applied geology and geosciences with its key objective particularly emphasis on application of basic geological knowledge for addressing environmental, engineering, and geo-hazards problems. The subject covers variety of topics including geodynamics, sedimentology and stratigraphy, volcanology, engineering geology, environmental geology, hydrogeology, geo-hazard and mitigation, mineral resources, energy resources, medical geology, geo-archaeology, as well as applied geophysics and geodesy.
Articles 5 Documents
Search results for , issue "Vol 5, No 1 (2020)" : 5 Documents clear
Determination of Groundwater Recharge Area by Using Hydroisotope Technic of Sei Bingei Area and Surrounding Areas, Langkat Regency, North Sumatra Azmin Nuha; Heru Hendrayana; Agus Budhie Wiyatna; Doni Prakasa Eka Putra; Azwar Satry Muhammad
Journal of Applied Geology Vol 5, No 1 (2020)
Publisher : Geological Engineering Department Universitas Gadjah Mada

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (7747.596 KB) | DOI: 10.22146/jag.51627

Abstract

Determination of Groundwater Recharge Area by Using Hydroisotope Technic of Sei Bingei Area and Surrounding Areas, Langkat Regency, North Sumatra
Coastal groundwater aquifer characterization from geoelectrical measurements- A case study at Kalapara, Patuakhali, Bangladesh. Mohammad Ibrahim Khalil; S. M. Didar-Ul Islam; Md. Jamal Uddin; Ratan Kumar Majumder
Journal of Applied Geology Vol 5, No 1 (2020)
Publisher : Geological Engineering Department Universitas Gadjah Mada

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (910.994 KB) | DOI: 10.22146/jag.55009

Abstract

Vertical electrical sounding has been carried out in a coastal area in the southern part of Bangladesh to locate the groundwater aquifers containing fresh water. The Interpex1X1Dv3 computer program was used to process the field apparent resistivity data sets obtained from the vertical electrical sounding.  Geoelectric layers were identified in the context of resistivity and thickness from the vertical electrical sounding data. From the initial parameters layered model was achieved using the inversion technique. Correlation of the obtained layer model with a nearby lithologic log concludes the groundwater aquifer system of the area. From the electrical properties of the subsurface layers, water bearing layers were detected and characterized. Very fine sand geoelectric layer with a thickness varying from 20 to 143 meters is an upper aquifer and has 0.66–14.02 Ωm apparent resistivity value. Fine sand geoelectric layer with 0.21-5.99 Ωm apparent resistivity value is lower aquifer with maximum thickness ~250 meters. From the resistivity value, it is observed that the upper aquifer contains saline to brackish-fresh water while the resistivity value of the lower aquifer indicates that it contains saline water. The water quality of the upper zone varies geographically from the southern to the northern part in the investigated area. The water quality of the upper aquifer is fresh in the northern part of the study while lower aquifer contains saline water there.
Low-Sulfidation Epithermal Carbonate-Base metal-Gold Mineralization Hosted by Tertiary Sedimentary Rocks in Bastem Prospect, Luwu District, Sulawesi Island, Indonesia: A Preliminary Study Arifudin Idrus; Irzal Nur; Sufriadin Sufriadin; Fadlin Fadlin; Indra Sanjaya; Rohaya Langkoke
Journal of Applied Geology Vol 5, No 1 (2020)
Publisher : Geological Engineering Department Universitas Gadjah Mada

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (3983.907 KB) | DOI: 10.22146/jag.55472

Abstract

In Indonesia, gold is typically mined out from epithermal, porphyry and skarn deposit types occurred within volcanic belts along magmatic arc or active continental margin setting. Numerous gold prospects, however, are recently discovered in association with metamorphic and sedimentary rocks. This paper is aimed to discuss a preliminary study on the occurrences and characteristics of the sedimentary rock-hosted low-sulfidation (LS) epithermal gold mineralization in Bastem (Bessengan Tempe) prospect, Luwu district, Sulawesi Island, Indonesia. Detailed geological and hydrothermal alteration mapping was performed to understand the distribution and characteristics of ore mineralization. Representative ore samples taken were analysed for ore chemistry by means of Fire Assay – Atomic Absorption Spectrometry (FA-AAS) and Acid Geochemical Digest - Atomic Absorption Spectrometry (GA-AAS). The results from this work that the Bastem prospect is stratigrapically occupied by Tertiary sedimentary rocks of Toraja formation, which is adjacent to volcanic rocks of Lamasi formation. Gold-bearing quartz±carbonate veins are hosted by mudstone and siltstone of Toraja formation. The quartz-carbonate veins show a typical LS epithermal open space filling texture containing erratic gold grade of up to 7.16 g/t with relatively high besemetals (Pb and Zn) grades of up to >0.4 and >1%, respectively. Based on those various features, the LS epithermal deposit is categorized as “carbonate-basemetal-gold mineralization type”, which might be originated in back arc rift/basin setting. This ‘unconventional’ sedimentary rock hosted-gold mineralization type would be the new target of gold exploration in Indonesia.
Mineralogical, Geochemical, and Mechanical Characteristics of Intrusive Andesite Rock Slope in Sangon 2 Area, Kulon Progo Regency, Indonesia Hnin Thandar Phyu; Heru Hendrayana; I Gde Budi Indrawan; Toshitaka Kamai
Journal of Applied Geology Vol 5, No 1 (2020)
Publisher : Geological Engineering Department Universitas Gadjah Mada

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (9890.6 KB) | DOI: 10.22146/jag.56345

Abstract

This study was carried out to investigate mineralogical, geochemical, and mechanical characteristics of intrusive igneous rock andesite consisting of Sangon 2 Slope located in Kulon Progo Mountains. Mineralogical characteristics of the rocks consisting of the slope were identified by visual observation of hand specimens in the field and petrographic and X-ray Diffraction (XRD) analyses of the rock samples in the laboratory, which rock genetic classification was determined. Types of rock hydrothermal alterations were determined by the presence of key minerals identified in the petrographic and XRD analyses. Hydrothermal alteration intensity was determined by comparing the number of secondary minerals to the primary minerals observed in the petrographic analyses of thin sections by point counting method. Rock weathering degrees were determined in the field based on the visual characteristics and in the laboratory-based on the Chemical Index of Alteration (CIA) of the rock samples. The rock uniaxial compressive strength (UCS) was determined by point load and compression tests. The results showed that the rocks typically consisted of 6.37 to 74.3% plagioclase, 1.52 to 6.82% quartz, 7.81 to 17.2% hornblende, and 4.81% pyroxene minerals and, therefore, were classified as andesite. The presence of chlorite and calcite as secondary minerals in the andesite rock samples indicated that the parent andesite rocks had undergone prophylactic hydrothermal alteration. Meanwhile, the percentages of primary minerals to secondary minerals indicated that the andesite rocks had undergone weak to high alteration intensity. Based on the visual characteristics, the research area consisted of fresh, slightly, moderately, highly, and completely weathered andesite rocks, and residual soil. The CIA values of the rock samples increased with the increase in rock weathering degree. Rock weathering degrees identified by the visual characteristics appeared to be in good agreement with those classified based on the CIA. The lower part of the mine slope profile consisted of fresh and slightly and moderately weathered andesite rocks, which had relatively high strength and were classified as very strong rocks. Meanwhile, the upper part of the slope profile consisted of highly and completely weathered andesite rocks, which had low compressive strength.Keywords:  andesite, hydrothermal alteration, kulon progo,  prophylactic alteration, weathering
Numerical Evaluation of Tunnel Portal Slope Stability at Bagong Dam Site, East Java, Indonesia Irien Akinina Fatkhiandari; I Gde Budi Indrawan; Dwikorita Karnawati
Journal of Applied Geology Vol 5, No 1 (2020)
Publisher : Geological Engineering Department Universitas Gadjah Mada

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (2961.867 KB) | DOI: 10.22146/jag.57044

Abstract

Geometries of excavated tunnel portal slopes at Bagong Dam site was initially designed without taking into account earthquake load. The excavated slope designs also assumed the rocks consisting the slopes were homogenous. The purpose of this research was to evaluate stability of the excavated tunnel inlet and outlet slopes at the Bagong Dam site under static and earthquake loads using finite element method. Stability of the natural slopes was also analyzed for comparison. The numerical static and pseudostatic analyses of slope stability were carried out using RS2 software (Rocscience, Inc.). Input data used in the numerical analyses were obtained from engineering geological mapping, rock core analyses, and laboratory tests. Seismic coefficient applied in the pseudostatic slope stability analyses was determined following guideline described in Indonesian National Standard. The engineering geological mapping and evaluation of rock cores indicated that the inlet tunnel slope consisted of four types of materials, namely residual soil, poor quality of volcanic breccia, very poor quality of volcanic breccia, and good quality of volcanic breccia. The outlet portal slope consisted of six types of materials, namely residual soil, very poor quality of limestone, poor quality of limestone, very poor quality of volcanic breccia, poor quality breccia, and good quality breccia. Based on the secondary elastic wave velocity (Vs) values, the rock masses in the research area were classified as hard rock (SA). Seismic analyses based on the earthquake hazard source map with 10% probability of exceedance in 50 years provided by the National Earthquake Center (2017) indicated that the PGA and the corresponding amplification factor FPGA in the research area were 0.3 and 0.8, respectively. The calculated seismic coefficient for the pseudostatic slope stability analyses was 0.12. The numerical analysis results showed that, in general, earthquake load reduced critical Strength Reduction Factor (SRF) values of the slopes. However, the natural and excavated tunnel portal slopes were relatively stable under static and earthquake loads. The natural slope at the tunnel inlet with a 40° inclination had critical SRF value of 4.0, while that of at the tunnel outlet with a 51° inclination had critical SRF value of 2.6. Under static load, the excavated slopes at the tunnel inlet and outlet having a 45° inclination had critical SRF values of 2.4 and 5.0, respectively. Under earthquake load, the excavated slopes at the tunnel inlet and outlet had critical SRF values of 2.3 and 3.5, respectively.

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