Pumice Tuff Research Articles

Hydrogeology Conceptual Model of Meninting Dam and Its Surrounding Area, West Lombok Regency, West Nusa Tenggara, Indonesia

The Meninting Dam is one of the dams recently built in West Lombok, Indonesia. Hydrogeologically, this dam was built on the Mataram-Selong Groundwater Basin, which is known to be a highly productive aquifer. However, in this area, no extensive research in terms of hydrogeological conditions has been conducted. Therefore, the objective of this research is to present a conceptual model of the hydrogeology of the Meninting Dam and its surrounding area. This study was carried out by collecting primary and secondary data on the geological, hydrological, and hydrogeological conditions in the research area. Results show that there are two layers of unconfined aquifer, one layer of aquitard, and one layer of confined aquifer in this area. The unconfined aquifer is built by layers made up of pebbles, sand, clay, gravel, and boulders, but also a layer of pumiceous tuff with a thickness up to 40 m and a hydraulic conductivity value between 10-1 mm/s and 5x10-2mm/s. The confined aquifer is composed of pumiceous tuff and has a thickness range of up to 100 m and a K value of about 5 x 10-3 mm/s. Between unconfined and confined aquifers, there is a thick layer of aquitard made up of laharic breccia.

Comparison of the Number of Compactor Passes and the Constrained Modulus of a Compacted Volcanic Soil

Volcanic soil is often used as fill material in road embankment construction in Java island-Indonesia. An understanding of the engineering properties of compacted volcanic soils is needed, especially during the preliminary design phase and during the detailed design phase of the road embankment. Carrying out a field compaction trial test will significantly assist in the design of the compaction process of the road embankment construction. Selecting the correct number of passes from the compactor and the engineering properties of compacted volcanic soils can be obtained from field compaction trial tests. Constrained modulus is one of the engineering properties that can indicate the stiffness of the fill material used in a road embankment. This study aims to determine the constrained modulus of compacted volcanic soil and compare it to the number of passes of a compactor from the field compaction trial test. The volcanic soil used in this study is classified as pumiceous tuff, which is derived from older volcanic rocks. The highest value of the oedometer modulus of compacted volcanic soils is 10.38 MPa which comes from eight (8) times passes of smooth drum roller conducted on field compaction trial test.

VES Geoelectrical Method for Identification of Aquifer Depth in Coastal Area of North Lombok Regency, Indonesia: Implications for the Sustainable Utilization of Water Resources

Measurement of the resistivity value distribution of subsurface rocks has been carried out in Mumbul Sari Village, Bayan District, North Lombok, which is one of the drought-prone areas in NTB Province, Indonesia. This research was conducted to identify the presence of groundwater aquifer layers in the study area based on the distribution of resistivity values. Data collection was carried out at two measurement points, namely the MBLS-1 Point with a track length of 700 m and the MBLS-2 Point with a length of 750 m. Data processing was carried out using IP2WIN Software to obtain a one-dimensional subsurface cross-sectional model, then interpreted using a resistivity log to make it easier to draw information on the subsurface point of measurement. Based on the distribution of resistivity values, it is known that the geological layers in the study area consist of pumice tuff, silty silt, sandy silt, and lava. The inversion results from the IP2WIN software show that the depth of the aquifer zone at Point MBLS-1 is 15.6 – 70.2 m with a resistivity value of 90.3 Ωm and a thickness of 54.5 m, while at Point MBLS-2 it is located at a depth of 21.9 – 86.1 m with a resistivity value of 112 Ωm and a thickness 64.3m. The aquifer zone at both measurement points is interpreted as a sandy silt layer. Groundwater drilling is recommended at the MBLS-1 point to a depth of 70 m and at the MBLS-2 point to a depth of 86 m. The geological structure that forms the boundary of the aquifer zone is a layer of compact and hard lava, so for groundwater utilization in the study area, it is recommended to use drilled wells to a depth of 70 – 86 m which is the lower limit of the aquifer layer.

The Estimation of Seismic Site Amplification of Bukittinggi City, West Sumatera, Indonesia

Bukittinggi city area is exposed substantial risk of both, close to seismic source line and site amplification due to soft surface sediment / soil layer. The Great Sumateran Fault (GSF) which is crossing this area, notorious as a very active seismic source. Its responsible to some major earthquake in the vicinity of the fault line. Generally, Bukittinggi area is covered by volcanic product as pumiceous tuff. We applied combined array and single station microtremor measurement to characterize near surface sediment in this area. Based on analysis microtremor single station and array using spatial autocorrelation (SPAC) method, weathered surface layer thickness is in the range of 0-108 m with shear wave velocity in the range of 62-190 m/s, while the fresh pumiceous tuff is in the range of 375-629 m/s. The estimation of site amplification in this area which is indicated by mean amplification is in the range of 1-1.95. The high amplification zone is occupies the northernmost area and some area locally in the southern part of Bukittinggi city.

Microzonation of Cisarua District Using Horizontal Vertical Spectral Ratio

The Bandung region is part of the framework of the Indonesian tectonic system, namely the tectonic plate meeting zone, where the Indo Autralia plate is infiltrated under the Eurasian plate in a convergent manner. The subduction process produces an effect in the form of an active fault geological structure in the Bandung area. One of these active faults is the Lembang Fault, which has a length of ± 29 kilometers and a shear acceleration of 3 to 5.5 millimeters per year. The microtremor measurement method is a passive geophysical method that utilizes natural subsurface vibrations so that it can provide dominant frequency data and amplification factors for soil layers. Based on the results of seismic susceptibility research using microtremor measurements using the HVSR method in the Lembang Fault zone in Cisarua Sub-District, it can be seen that the distribution of the dominant frequency values tends to be influenced by lithology and topography. In the research area, it is known to have a dominant frequency value that varies due to the different types of lithological units. In general, the dominant frequency ranges from 1-3 Hz because it is dominated by tuff sand and tuff pumice, and areas composed of volcanic breccias have a dominant frequency value between 3-6 Hz. Meanwhile, the amplification factor value will be influenced by rock deformation and weathering. The area that has a very high amplification factor value is in the southeast of the study area with an A0 value greater than 5. This indicates that the area is composed of a layer of thick and not dense tuff sand

Effects of thiosulfate addition on ammonia and nitrogen removal in biofilters packed with Oyaishi (pumice tuff).

Ammonia removal is achieved partly by absorption and nitrification in biofilters, resulting in the accumulation of nitrogen and the necessity of treating the effluent water. We investigated the effects of thiosulfate addition to a biofilter containing pumice tuff for ammonia and nitrogen removal in a laboratory-scale experiment. The addition of thiosulfate to the circulating water led to a decreased nitrate and nitrite along with an increase of sulfate. The inorganic nitrogen in the circulating water decreased by up to 44% with thiosulfate addition compared to without thiosulfate. Batch experiments revealed that denitrification activity decreased exponentially along with increases in dissolved oxygen; however, approximately 30% of denitrification activity was maintained at dissolved oxygen concentration of 3.3mg/L. Metabarcoding of 16S rRNA genes indicated that the genus Thiobacillus had a relative abundance of 0.002%-0.016% of total bacteria in the biofilter packing material. The circulating water pH was decreased below 5 with sulfur oxidation, and ammonium was accumulated without pH control resulting in a decrease in the relative abundance of the family Nitrosomonadaceae. Its relative abundance increased with control of pH to near neutral, indicating that ammonia-oxidizing activity could be maintained by adjusting pH. Thiosulfate addition could stimulate nitrogen removal by sulfur-dependent denitrification in biofiltration systems.

In-situ oxidation effect on pore size distribution in investigating adsorption properties under various geochemical conditions

Redox affected pumice tuff was used to investigate the changes of pore properties due to oxidation and its possible consequences to adsorption of nuclides on it. Porosity and pore size distribution were analyzed by mercury injection technique and scanning electron microscopy. Batch experiment was carried out with 1 cm3 block shaped intact pumice tuff samples to determine adsorption coefficient, Kd at several pH, ionic strength and initial nuclide concentrations of stable cesium (133Cs). Pore area, surface area and specific surface area were determined from pore size distribution data before and after adsorption experiment and later compared between fresh and oxidized samples. The results showed that reduction of less than 0.33 μm size micro pores due to oxidation is mainly responsible for reducing surface areas, eventually reducing the sorption quantity. Influence of pore properties became negligible in redox affected pumice tuff indicating inverse relation of oxidation phenomena with adsorption coefficients values.

Adsorption of 133Cs and 87Sr on pumice tuff: A comparative study between powder and intact solid phase

This study examines the use of intact samples as an alternative to powder in conventional batch sorption studies to determine the distribution coefficient (Kd). Stable cesium (133Cs) and strontium (87Sr) were used under specified geochemical conditions to compare the Kd values of powder and block pumice tuff samples. The aim of the study was to infer any Kd difference under laboratory and field conditions. Kd values for block samples were found to be less than one order of magnitude lower than powder materials for both Cs and Sr on fresh tuff, and more than one order of magnitude lower in oxidized tuff. Destruction of micropores in oxidized tuff was estimated to be mainly responsible for reducing Kd values in oxidized tuff. However, approximately one order of magnitude difference in Kd values indicates that homogenously prepared intact samples can be used for sorption coefficient measurement at closer to in situ conditions. Pore size distribution analysis using mercury intrusion porosimetry revealed that lower Kd values on block samples result from lower surface area available as sorption sites due to inaccessible closed pores in the intact solid.

Volcanostratigraphic Sequences of Kebo-Butak Formation at Bayat Geological Field Complex, Central Java Province and Yogyakarta Special Province, Indonesia

DOI:10.17014/ijog.3.2.77-94Bayat Complex is usually used as a work field for students of geology and other geosciences. The study area is located in the southern part of the Bayat Complex. Administratively, it belongs to Central Java Province and Yogyakarta Special Province. The lithology of Bayat is very complex, composed of various kinds of igneous, sedimentary, metamorphic, and volcanic rocks. Most of previous researchers interpreted Bayat as a melange complex constructed within a subduction zone. Kebo-Butak is one of formations that forms the Bayat field complex. The formation is composed of basalt, layers of pumice, tuff, shale, and carbonaceous tuff. Most of them are known as volcanic rocks. These imply that volcanic activities are more probable to construct the geology of Bayat rather than the subducted melange complex. The geological mapping, supported by geomorphology, petrology, stratigraphy, and geological structures, had been conducted in a comprehensive manner using the deduction-induction method. The research encounters basalt, black pumice, tuff with basaltic glasses fragments, zeolite, argilic clay, as well as feldspathic- and pumice tuff. Petrographically, the basalt is composed of labradorite, olivine, clinopyroxene, and volcanic glass. Black pumice and tuff contain prismatic clinopyroxene, granular olivine, and volcanic glasses. Feldspathic tuff and pumice tuff are crystal vitric tuff due to more abundant feldspar, quartz, and amphibole than volcanic glass. Zeolite comprises chlorite and altered glasses as deep sea altered volcanic rocks. The geologic structure is very complex, the major structures are normal faults with pyrite in it. There were two deep submarine paleovolcanoes namely Tegalrejo and Baturagung. The first paleovolcano erupted effusively producing basaltic sequence, while the second one erupted explosively ejecting feldspathic-rich pyroclastic material. The two paleovolcanoes erupted simultaneously and repeatedly.

Oxidation of Solid Phase and Ionic Strength Effect to the Cesium Adsorption on Pumice Tuff

In-situ oxidation of solid phase was considered to investigate adsorption behavior under different geochemical parameters like pH, initial concentration and ionic strength. Pumice tuff, a potential host rock for low and intermediate radioactive wastes, has been affected by the redox zone. The characterization of the fresh and oxidized tuff was performed by X-ray diffractometer, scanning electron microscope and mercury intrusion porosimetry. In order to compare the difference of distribution coefficient (Kd) in fresh and oxidized pumice tuffs, a batch adsorption study was carried out at the range of pH (4 - 12), ionic strength (0.003, 0.1, 1.0 and 3.0 mol/dm3) and initial cesium concentration (10&#454, 10&#455, 10&#456 and 10&#457 mol/dm3). Based on experimental Kd values, ionic strength was found to be the most influential factor, whereas the effects of pH, initial Cs concentration and weathering condition of pumice tuff were negligible. The recalculated Kd values suggest that the existing surface complexation model is applicable to explain the sorption coefficients through the wide range of solution conditions.

Strontium dissolution effect on the adsorption experiment with rhyolitic pumice tuff

Strontium dissolution effect on the adsorption experiment with rhyolitic pumice tuff

Characterization and evaluation of arsenic and boron adsorption onto natural geologic materials, and their application in the disposal of excavated altered rock

Construction of tunnels in Hokkaido, Japan often excavates rocks containing substantial amounts of arsenic (As) and boron (B). When these rocks are exposed to the environment, As and B are leached out that could potentially contaminate the surrounding soil and groundwater. Natural geologic materials contain minerals like Al-/Fe-oxyhydroxides/oxides that have As and B adsorption capabilities. Because these materials are widespread and readily available, they could be utilized in the mitigation of As and B leached out from these sources. This paper describes the ability of three natural geologic materials (i.e., pumiceous tuffs, partly-weathered volcanic ashes and coastal marine sediments) to sequester As and B from aqueous solutions and the actual leachate of a hydrothermally altered rock. The adsorption of As fitted well with either the Langmuir or Freundlich isotherm while that of B followed the Henry-type model (linear). Among the samples, those containing substantial amorphous Al and Fe exhibited higher As adsorption. However, the distribution coefficient of B only had a moderate positive correlation with these amorphous phases. The best adsorbent among these natural geologic materials was utilized in the adsorption layer of the column experiments. Adsorption of As was more effective the thicker the adsorption layer, but this retardation was only temporary due to significant changes in the pH. In contrast, the adsorption layer only retarded the migration of B to a limited extent.

Sorption Behavior of Nickel and Palladium in the Presence of NH3(aq)/NH4+

ABSTRACTIt is necessary to assess the impact of nitrate salts and their reduction products (e.g. NH3(aq)/NH4+) contained in low-level radioactive waste generated from nuclear reprocessing process for the safety assessment of geological disposal of the waste. In the present study, sorption behavior of Ni and Pd on pumice tuff was investigated in the presence of NH3(aq)/NH4+. Under various NH3(aq)/NH4+ concentration, pH and ionic strength conditions, distribution coefficient (Kd) of Ni and Pd on pumice tuff was determined by a batch experiment. For Ni system, the Kd values showed no significant dependence on initial NH4+ concentration ([NH4+]ini < 1 M) in neutral pH region, which agreed with the prediction from thermodynamic data. For Pd system, the Kd values decreased with an increase of [NH4+]ini, suggesting the formation of stable ammine complexes (Pd(NH3)m2+ (m: 1 – 4)). The obtained Kd values for Ni and Pd were analyzed using a surface complexation model. By taking complexes predicted by thermodynamic data into account, sorption behavior of Ni and Pd in the presence of NH3(aq)/NH4+ were well explained.

Crystallization Stages of the Bishop Tuff Magma Body Recorded in Crystal Textures in Pumice Clasts

The Bishop Tuff is a giant silicic ignimbrite erupted at 0.76 Ma in eastern California, USA. Five pumice clasts from the late-erupted Bishop Tuff (Aeolian Buttes) were studied in an effort to better understand the pre- and syn-eruptive history of the Bishop magma body and place constraints on the timescales of its existence. This study complements and expands on a previous study that focused on early-erupted Bishop Tuff pumice clasts. Bulk densities of pumice clasts were measured using an immersion method, and phenocryst crystal contents were determined using a sieving and winnowing procedure. X-ray tomography was used to obtain qualitative and quantitative textural information, particularly crystal size distributions (CSDs). We have determined CSDs for crystals ranging in size from {approx}10 to {approx}1000 {micro}m for three groups of mineral phases: magnetite ({+-}ilmenite), pyroxene + biotite, quartz + feldspar. Similar to early-erupted pumice, late-erupted pumice bulk density and crystal contents are positively correlated, and comparison of crystal fraction vs size trends suggests that the proportion of large crystals is the primary control on crystallinity. Porosity is negatively correlated with crystal content, which is difficult to reconcile with closed-system crystallization. Magnetite and pyroxene + biotite size distributions are fractal in nature, often attributedmore » to fragmentation; however, crystals are mostly whole and euhedral, such that an alternative mechanism is necessary to explain these distributions. Quartz + feldspar size distributions are kinked, with a shallow-sloped log-linear section describing large crystals (> 140 {micro}m) and a steep-sloped log-linear section describing small crystals (< 140 {micro}m). We interpret these two crystal populations as resulting from a shift in crystallization regime. We suggest that the shallow-sloped section describes a pre-eruptive quartz + feldspar growth-dominated regime, whereas the steep-sloped section represents a population that grew during a nucleation-dominated regime that began as a result of decompression at the onset of eruption. Timescales of quartz growth calculated from the slopes of these two segments of the size distributions indicate that the pre-eruptive crystal population grew on timescales on the order of millennia and may describe the timescale of crystallization of the Bishop magma body. The syn-eruptive population gives timescales of < 1-2 years (but possibly much less) and probably marks the onset of eruptive decompression.« less

KAJIAN LONGSOR AKIBAT GEMPA DI NAGARI TANDIKEK KECAMATAN PARTAMUAN KABUPATEN PADANG PARIAMAN SUMATERA BARAT, INDONESIA

Earthquacke on 30th of September 2009 in West Sumatra had ruined Padang Pariaman, Agam, and Padang city districts. The damage was not only caused by the earthquake itself but also due to the landsliding following the earthquake, such as in Tandikek. Hundreds of people, houses, buildings, schools, as well as agricultural land (ricefield and dryland farming) were burried in Lubuk Laweh, Kepala Koto and Cumanak. This research was conducted by employing survey method and by observing the phenomenon of tuff pumice on how it was affected by earthquake and water. Then, soil characteristics were analysed based on soil physical data from previous research. Several soil characteristics analysed were soil texture, bulk density, structure and depth of solum, organic matter content, and permeability. Land characteristics were determined through field visit. Some land condition being observed was slope (percentage and length), stone exposed, soil water depth, and land use. Additionally, besides from field visit, the data were also obtained from topography and morphology maps derived from Google Earth. Rainfall data (monthly and annually) were collected from several nearby meteorology stations. Analyses for degree of landsliding risks for an area were used soil and land characteristics criteria causing landsliding. Based on field visit, it was seen that the research area was still susceptible to landsliding. This was due to the parent materials of the soil deriving from tuff pumice which is crumb structure and loamy texture on the top layer. Climate, especially annual rainfall in study site was high enough (approximately 4322 mm) which was evently distributed all year long without dry month. Slope of the area was &gt; 45%, especially areas hit by landsliding. Land use was not based on soil conservation rule, such as coconut and arenga pinneca, and other mixed trees were planted on the area having &gt; 45% slope. The results of the soil characteristic analyses showed that HARKAT interval of lansliding threat was 13 and land characteristics showed 20. Summation of HARKAT values from soil and land characteristics was 33. This number showed that the study site had high degree of landsliding risk. The possibility of areas would be hit by lansliding were Partamuan, Koto Timur, Sungai Geringging, and around Maninjau lake.Keywords : earthquake, soil and land characteristics, tuff pumice, wet tropical

Analysis of Sorption Behavior of Cesium and Iodide Ions on Pumice Tuff

In the reliable safety assessment of radioactive waste disposal, the understanding and modeling of the sorption behavior onto the host rock under various groundwater conditions are indispensable. The influence of pH, ionic strength, and the initial concentrations of Cs and I on the sorption of Cs and I on tuff and pumice isolated from the original pumice tuff rock was investigated. For both rocks, the proton concentration has little effect on the Kd values forCs in the pH range 3–10. As the ionic strength of the solution increases in the presence of sodium perchlorate as a matrix ion, the Kd value of cesium apparently decreases, reflecting the competition of the electrolyte Na+ with thespecific sorption of Cs+ on the negatively charged sites. In contrast, no significant dependence of ionic strength on the Kd of anionic iodine was found. A simple surface complexation model without considering electrostatic works was applied to simulate the sorption of ions on rocks, and the model parameters were determined. The Kd values at the given chemical conditions were estimated using the parameters and compared with the ones in the literature.

Geotechnical Aspects of the Sumatra Earthquake of September 30, 2009, Indonesia

This paper reports and discusses the results of a field survey conducted by a joint scientific group from Japan and Indonesia to assess the geotechnical aspects of the Sumatra earthquake (Mw=7.6) of September 30, 2009. The studied area included the Padang and Pariaman cities, where a number of buildings collapsed as a result of strong shaking, and a mountainous part of the Pariaman district, a place where massive landslides buried several villages, claiming more than 400 human lives. The main objective of the survey was to investigate the causes and mechanisms of catastrophic landslides; however, other geotechnical problems such as lateral spread and liquefaction were also addressed. Field observations indicated that the catastrophic landslides occurred on relatively gentle slopes, then mobilized into debris flows, and traveled several hundred meters from their points of origin. The failure surfaces developed along the boundary of highly weathered pumice tuff with more intact and less weathered bedrock. Data from a portable cone penetration test showed that the sliding material was rather weak, having SPT N-values in the range of 5-10. The results of the field survey suggested that the main cause of slope instability was high pore-water pressures that generated in the soil mass during the earthquake.

Quantitative 3D petrography using X-ray tomography 2: Combining information at various resolutions

X-ray tomography is a nondestructive technique that can be used to study rocks and other materials in three dimensions over a wide range of sizes. Samples that range from decimeters to micrometers in size can be analyzed, and micrometer- to centimeter-sized crystals, vesicles, and other particles can be identified and quantified. In many applications, quantification of a large spectrum of sizes is important, but this cannot be easily accomplished using a single tomogram due to a common trade-off between sample size and image resolution. This problem can be circumvented by combining tomograms acquired for a single sample at a variety of resolutions. We have successfully applied this method to obtain crystal size distributions (CSDs) for magnetite, pyroxene + biotite, and quartz + feldspar in Bishop Tuff pumice. Five cylinders of systematically varying size (1–10 mm diameter and height) were analyzed from each of five pumice clasts. Cylinder size is inversely proportional to image resolution, such that resolution ranges from 2.5 to 17 μm/voxel with increasing sample size. This allows quantification of crystals 10–1000 μm in size. We obtained CSDs for each phase in each sample by combining information from all resolutions, each size bin containing data from the resolution that best characterizes crystals of that size. CSDs for magnetite and pyroxene + biotite in late-erupted Bishop pumice obtained using this method are fractal, but do not seem to result from crystal fragmentation. CSDs for quartz + feldspar reveal a population of abundant crystals <35 μm in size, and a population of crystals >50 μm in size, which will be the focus of a separate publication.

Laurentian origin of the Ordovician Grangegeeth volcanic arc terrane, Ireland

Abstract: U–Pb ages determined by laser-ablation multi-collector inductively coupled plasma mass spectrometry on 199 zircons from a lithic pumice tuff are the first isotopic ages from the Grangegeeth volcanic terrane of Ireland. The youngest zircon population ( n = 24) yields an age of 465.4 +2.4/−3.1 Ma. Inherited zircons yield ages of c . 1120–1520, c . 1650–1914 and c . 2540–2890 Ma. The absence of zircons between c . 550 and 700 Ma argues against involvement of Avalonia as a source of inherited crystals. Overall, the inherited age spectra are characteristic of Laurentian crust or metasedimentary successions of peri-Laurentian provenance. These findings suggest that the Grangegeeth volcanic terrane does not represent a continuation of the intra-Iapetus Exploits arc of Newfoundland. Supplementary material: Full analytical protocols, applied data corrections, processing and plotting rationales and data table for zircon LA-MC-ICP-MS analysis are available at http://www.geolsoc.org.uk/SUP18399 .

軽石凝灰岩のガス移行特性に関する研究 （その２）気液二相流パラメータの同定

軽石凝灰岩のガス移行特性に関する研究 （その２）気液二相流パラメータの同定