Journal of Applied Geology
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Fluid Inclusion Study of Epithermal Gold-Base Metal Mineralization System in the Shwebontha Prospect, Monywa Mining District, Central Myanmar Monywa
No full textThe Shwebontha Prospect area is one of prominent epithermal Au-Ag prospects in Monywa mining district, central Myanmar, characterized by the appearance of gold-bearing and base metal quartz veins with gold grade is around 3g/t -10.4g/t. The geology of the area consists of the volcanic and volcaniclastic rocks of Upper Oligocene-Middle Miocene Magyigon Formation that served as the host rock of the ore mineralization. This research focused on fluid inclusion study is aimed to know the characteristics of hydrothermal fluids during ore mineralization as well as the possible paleo- depth and temperature of formation of gold-bearing and base metal quartz veins. The mineralization styles are gold-bearing brecciated quartz veins and chalcedonic quartz veins where sulfides are clustered as well as disseminated both in quartz gangue and volcanic host rocks. Those quartz veins include pyrite, sphalerite, galena, chalcopyrite and gold (electrum). Fluid inclusion microthermometry indicates that the ore mineralization is characterized by the values of homogenization temperature range from 158°C to 310°C and salinities range from 0.35 to 2.41wt.% NaCl equiv. This temperature is consistent with the formation temperature of 250°C to 270 °C and also their estimate paleo-depth of formation is between 440m and 640m respectively. Microthermometric data indicates that fluid mixing and dilution were significant processes during ore mineralization and evolution of hydrothermal fluids. Based on the petrography of fluid inclusion, microthermometric measurements and ore minerals assemblage as well as estimation of paleo-depth from the Shwebontha Prospect imply that forming in under shallow level epithermal environmen
Hydrothermal Alteration of High Sulfidation Epithermal Deposits in Secang Area, Tulungagung, East Java, Indonesia
Get PDFThis research aims to determine geological condition and alteration in an epithermal high sulfidation mineralization as an initial guide for further exploration stages. Detailed geological mapping with scale of 1:12,500 is conducted to identify geological aspects and distribution of alteration zones. Selected rocks samples were prepared for laboratory analysis which are petrography, XRD (X-Ray Diffraction), and FA-AAS (Fire Assay-Atomic Absorption Spectrometry) analyse. Geological condition of the study area consists of six rock units including andesite lava, andesite breccia, diorite intrusion, polymict breccia, limestone, and alluvial deposit. Geological structures found are left strike-slip fault with right strike-slip fault as accompany. Result of XRD analysis shows the presence of clay minerals group: smectite, kaolinite, illite, diaspore, alunite, and pyrophillite. The alteration zones of study area are propylitic, argillic, advance argillic, and silisification zones. The further exploration stage is recommended to focus at the southwest and northeast of study area
Petrography and Geochemistry of Metasedimentary Rocks from the Taku Schist in Kelantan, North-East Peninsular Malaysia.
Get PDFThe Taku Schist, which is located in the north-east Peninsular Malaysia, is characterized by its North-South oriented elongated body. It forms part of the Indonesian orogenic build-up that was generated via the convergence of the Sibumasu continental unit and Sukhothai Arc. Subsequent petrography analyses of the metasedimentary rocks sourced from the Taku Schist revealed that their formation was attributable to the metamorphism of greenschist into amphibolite facies, which could be observed near the Triassic and Cretaceous intrusions of the Kemahang Granite. The evolutionary process of the rocks could be linked with the interactions occurring between contact and regional metamorphisms. The resulting chemical classification upon their assessment disclosed that the metasedimentary rocks of Taku Schist were made up of greywacke and shale, grouped into the quartzose sedimentary provenance, and belonged to the Continental Island Arc (CIA). This information is required for the tectonic setting discrimination purpose. It is a reflection of the episodic contractions underwent by the Taku Schist, wherein they would lead to the Sibumasu sedimentary cover along with both an accretionary wedge and the genetically-correlated Bentong-Raub melange to different greenschist. Otherwise associated with amphibolite facies, the conditions and depths of the facies were determined according to their position in relation to the upper plate of the Sukhothai Arc
The Engineering Characteristics and Classifications of Rock Masses along Road Section from Prambanan to Patuk, Yogyakarta, Indonesia
Get PDFSeveral attraction places and agriculture area that essentials for tourism and villager to do their activities are located approximately 6 km along the road of Candi Ijo to Ngoro-Oro in between Prambanan and Patuk sub-districts, Yogyakarta, Indonesia. Many jointed rock masses along the road have the potential to fail. This paper describes the rock mass characteristic and quality determined using the Geological Strength Index (GSI) and Rock Mass Rating (RMR) classifications. The rock mass characteristic and quality were essentially the preliminary results of a study to evaluate stability of the rock slopes along the road of Candi Ijo to Ngoro-Oro. Field observation and laboratory tests were carried out to determine parameters of the GSI and RMR. The results show that the slopes in the study area consisted of tuffaceous sandstone, vitric tuff, lithic tuff, cemented tuffaceous sandstone, lapilli tuff, subarkose, laminated mudrock, and laminated tuffaceous sandstone. The intact rocks were classified as weak to very strong. The research area consisted of three rock mass qualities, namely fair rock mass quality having GSI between 30 and 45 and RMR between 41 and 60, good rock mass quality having GSI between 46 to 65 and RMR between 61 and 80, and very good rock mass quality having GSI > 65 and RMR between 81-100. The relationship between GSI and RMR obtained in this study was in good agreement with that proposed by Hoek et al. (1995)
Assessment of heavy metal contamination in soil around Piyungan Landfill, Yogyakarta, Indonesia
Get PDFOne of the negative impacts of the landfill as solid waste disposal is soil contamination by heavy metals. This study assessed heavy metals impact, especially Pb, Cu, Zn, and Cd, in the soil in Piyungan landfill, Bantul, Yogyakarta, Indonesia. The assessment was conducted by analyzing 15 soil samples from 25 cm depth in the study area, which was divided into three-zone. The study results showed that generally, the highest content of metals was found in zone II, which is located near or directly situated in a landfill site. The pollution index (PI) calculated showed in order Cd>Cu>Pb>Zn. The result also indicates that Cd has the highest pollution index and even the highest risk compared to Pb, Cu, and Zn. The eco-risk index (RI) calculation showed that the value was 29 to 70 demonstrating a low class. The result also indicates that the accumulation of heavy metals investigated in this study was normal, and that the ecological risk was relatively low
Engineering Site Investigation for Foundation Design and Construction in Shale and Sandstone Derived Soils of Okitipupa Area, Southwestern Nigeria
Get PDFGeotechnical and geo-electrical investigations of Okitipupa has been carried out with the major objectives of establishing the subsoil/geology, evaluate the geotechnical properties and recommend appropriate foundation alternatives for building foundation construction. Seven borings were carried out with hand auger at two cone penetration test locations, and representative samples were collected and analyzed in the laboratory in accordance with relevant geotechnical engineering standards. In addition, six vertical electrical soundings (VES) were also conducted using Schlumberger configuration. The result of VES delineates three major geologic sequence comprising the topsoil/caprock, sand surficial aquifer, and sand intermediate aquifer. The topsoil has resistivity range of 242 – 1503 ohm-m and thickness of 3.4 - 20.9 m composed of clay sand and sand. This layer is capable of supporting shallow foundation such as simple spread, raft of reinforced concrete, with recommended allowable bearing pressure of 100 KN/m2 at depths of 1.0 m and 3.2 m in the northern and southern part of the study area respectively. The estimated settlement are less than 50 mm using foundation width of 0.6 m, but could be reduced by almost 50% if the width is greater than or equal to 2 m. The groundwater level is very deep (>10 m) and may not likely threatens the integrity of the foundation structures. The estimated allowable bearing capacity for strip footing (203 – 980 KN/m2), square footing (608 – 2940 KN/m2) within 1.4 m depth is appropriate. The capacity of driven (deep foundation) circular piles of diameters 400mm, 500mm, and 600mm, the recommended pile capacity varies at depth of 5 m (69 – 124 KN), 10 m (225 – 378 KN), and 15 m (470 – 766 KN), while that of bored circular pile ranges from (36 – 75 KN), 10 m (93 – 180 KN), and 15 m (170 – 317 KN)
Subsurface Geology and Hydrothermal Alteration of The “X” Geothermal Field, West Java: A Progress Report
Get PDF“X” geothermal field is one of the geothermal fields in West Java. PT. Y (Persero) developed it since 2014. The geothermal field has produced electricity, with installed capacity amounted to 55 MWe. The “X” geothermal system is vapor-dominated. The geothermal manifestations are located at approximately 2,100 m asl. The “X” field consists of three main upflow zones: Kawah Putih, Kawah Ciwidey, and Kawah Cibuni. This study analyzed the drill cuttings from 3 wells as the primary data with total depths ranging from 1,581 to 2,166 m with the well’s highest stable temperatures measured of ±230°C. The three wells selected for this research—Well A, Well B, and Well C—were analyzed to describe the rock properties and estimate the prospect areas of present-day geothermal exploration in the “X” geothermal field.The paper aims to understand better of the subsurface geology and its correlation to the dynamic processes (i.e., hydrothermal alteration) in the “X” geothermal field. The hydrothermal minerals are formed by near-neutral pH fluids and are characterized by quartz, calcite, clays (smectite, illite, chlorite), wairakite, epidote, and actinolite. Acidic fluids are evident by forming acidic hydrothermal mineral, e.g., anhydrite at various depths of the studied wells, particularly at Well C which is located around Sugihmukti-Urug area. Moreover, the previous studies by Reyes (1990), Layman and Soemarinda (2003), Rachmawati et al. (2016), Elfina (2017) on hydrothermal minerals, geothermal manifestation characteristics, fluid geochemistry, and conceptual model are adapted to improve the analysis and interpretation of this paper
Phytoremediation of Heavy Metals Contaminated Soil in Artisanal Gold Mining at Selogiri, Wonogiri District, Central Java, Indonesia
No full textArtisanal gold mining (ASGM) is commonly found in Indonesia, particularly in Wonogiri District, Central Java. One of the impacts of ASGM activity is soil contamination influence by mining waste. The objective of this study to investigate the potential use of Amaranthus spinosus L. and Jatropha curcas for remediation of Pb and As in contaminated soil. Phytoremediation experiment was conducted by using Amaranthus spinosus L. and Jatropha curcas and evaluate the effectiveness of both plants as a hyperaccumulator. The result shows that the higher Pb and As concentration was found in roots rather than shoots in both plants, however, the use of Jatropha curcas seems more effective on reducing Pb and As concentrations more than Amaranthus spinosus L in both shoots and roots. Generally, the use of both hyperaccumulator plants was more effective in Pb remediation compared to As. This phytoremediation experiment revealed that the use of both hyperaccumulator plants reduces the concentrations of Pb and As in contaminated soil, which of the critical point leading to the entry of Pb and As into the food chain
Dominant Weathering Profile Assessment of Kebo-Butak Volcanic Rocks in Gedangsari and Ngawen area, Yogyakarta, Indonesia
Get PDFThe Gedangsari and Ngawen area is predominantly composed of volcanic and volcaniclastic sequencesdistributed east – west direction of the northern parts of Southern Mountain. The massive tectonism as well as tropical climatein this region have been producing weathering profiles in varying thickness which inevitably affects thegeotechnical properties. This study aims to assess the dominant weathering profileof the lower part of Kebo-Butak Formation as well as evaluating the distribution of the discontinuity. In order to know the dominant weathering profile and discontinuity evaluation, this study utilizes a total of 26 panels from five stations investigated through a geotechnical data acquisition including the geological condition, weathering zones, joint distribution, and discontinuity characteristics. The result shows four types of dominant weathering profiles in lower part of Kebo-Butak Formation called as dominant weathering profile A, B, C, and D. Profile A, B, C consisted of a relatively identical weathering degree pattern of fresh, slightly, moderately, completely weathered zone with the variation of thicknesses. However, the weathering degree in profile D reached the residual soil degree controlled by more intensive joints. The fine-grained sedimentary rocks also tends to have smaller spacing, shorter persistence, and higher weathering degree of discontinuities as compared to coarse-grained sedimentary rocks
Numerical Analysis of Slope Stability Due to Excavation of Diversion Tunnel at Pamukkulu Dam Site, Indonesia
Get PDFLocated in the Takalar Regency of South Sulawesi Province, the Pamukkulu Dam is planned to use a tunnel type as its diversion structure. One of the critical parts in the tunnel construction is the stability of portal slopes. This research aimed to estimate the effect of tunnel excavation on the stability of the portal inlet and outlet slopes under static and earthquake loads by using the finite element method. The slope stability analyses were carried out under conditions of prior to and after tunnel excavation. The input parameters used were laboratory test results in the forms of index properties and mechanical properties taken from rock core drilling samples, completed with the rock mass quality parameters based on the Geological Strength Index (GSI) classification. The Mohr-Coulomb failure criterion was used to model strength of the soil, while the Generalized Hoek-Brown failure criterion was used to model strength of the rocks. The results of rock cores analysis using the GSI method showed that the inlet tunnel slope consisted of four types of materials, namely residual soil, fair quality of basalt lava, good quality of basalt lava, and very good quality of basalt lava. Meanwhile, the outlet portal slope consisted of three types of materials, namely residual soil, good quality basalt lava, and very good quality basalt lava. The calculated horizontal seismic coefficient for the pseudo-static slope stability analysis was 0.0375. The analysis results of slope stability in the Y1 inlet section had a critical Strength Reduction Factor (SRF) value of 2.35 in a condition prior to the tunnel excavation and a critical SRF value of 2.34 after the tunnel excavation. The Y2 outlet section had a critical SRF value of 13.27 in a condition before tunnel excavation and a critical SRF value of 5.55 after the tunnel excavation. The earthquake load addition at the Y1 inlet section showed a critical SRF value of 2.05, both before and after the tunnel excavation. The Y2 outlet section showed a critical SRF value of 11.49 before the tunnel excavation and a critical SRF value of 5.54 after the tunnel excavation. The numerical analysis results showed that earthquake load reduced critical SRF values of the slopes. At the Y1 inlet section, the tunnel excavation did not have a significant effect on slope stability. It was demonstrated by an extremely small decrease in a critical SRF value of 0.43% for a condition without an earthquake load and an unchanged critical SRF in a condition with an earthquake load. At the Y2 outlet section, the tunnel excavation had a more significant effect on the slope stability. It was exhibited by the decrease in the critical SRF value of 58.18% in a condition without an earthquake load and a decrease in the critical SRF value of 51.78% in a condition with an addition of an earthquake load. However, the analysis of slope stability for both sections showed that all design slopes were above the required allowable safety factor value