Thickness Of Sediment Layer Research Articles

Determination of earthquake prone zones at university of tadulako based on dominant periods and peak ground acceleration (PGA)

University of Tadulako is the largest State University in Palu City. When an earthquake with a magnitude of 7.4 Mw on September 28, 2018, occurred, many buildings were damaged and even collapsed at that time, even causing casualties due to the rubble. Research on the Local Site Effect is essential for the assessment of seismic hazard. In this study, the local site effect was analyzed using the HVSR method based on microtremor data. The predominant Period (To) ranges between 1.709 s to 3.816 s, indicates that this area consists of alluvium and has a very thick sediment layer. Another parameter calculated in this paper is the peak ground acceleration (PGA) with values from 0.914 g to 0.924 g. This value is the first indicated soil damage level due to ground motions. The results of this study can be used as a consideration in the development of regional spatial planning and building structures based on earthquake analysis.

Анализ изменений эпюры скоростей в самотечных сетях водоотведения с разной толщиной слоя отложений в лотковой части труб

The practice of operation of gravity sewer networks of domestic wastewater shows that sediment de-posits are formed in the chute section of pipes at certain velocities of the gravity flow. These deposits affect the hydraulic characteristics of the flow, which depend on the actual thickness of the sediment layer in sewer pipes. In this study, a velocity diagram reflecting the distribution of actual velocity values of wastewater flow along the depth of the wetted perimeter of pipes with sediment deposits in their chute sections is established. To this end, the dependences derived by the authors previously for hy-draulic calculation of drainage networks with internal sediments were used. It is confirmed on a specific example that the limiting value of sediment thickness preventing the continuation of further operation for concrete pipes with a diameter of 400 mm equals 80 mm. The obtained diagram of the vertical ve-locity distribution of sewage flow can be used to determine the actual pipeline fill level corresponding to the actual sediment layer thickness in sewer pipes.

Migration and Deposition Law of Pollutants in Urban Sewage Confluence Pipe Network from the Perspective of Ecology.

Aiming at the problem of pollutant migration and deposition in urban sewage confluence pipe, an experimental simulation system of sewage confluence pipe was established. The confluence conditions of three flow patterns (velocity ratio Vaccess/Vtrunk = 0.1/0.2, Vaccess/Vtrunk = 0.1/0.3, and Vaccess/Vtrunk = 0.2/0.3) were simulated. The changes of sediment thickness, carbon pollutants, nitrogen pollutants, and phosphorus pollutants in different confluence areas were analyzed, and the migration and deposition laws of various pollutants in urban sewage confluence pipe network under different flow patterns were revealed. The results show that when the flow velocity of trunk and branch roads changes, the deposition of various pollutants and the carrying capacity of water flow in the pipeline change, resulting in the change of sediment layer thickness and pollutant content. With the increase of trunk velocity, the sediment thickness in the area before and after confluence decreases, while the increase of branch velocity only reduces the sediment thickness in the area at the back of confluence. Under any flow pattern, the sediment thickness in the retention area (G3 and G4) shows an increasing trend, which is the key area of pollution removal. Under the three flow patterns, the content of carbon pollutants reaches the peak at the TCOD and SCOD values of G4 monitoring point. Increasing the trunk velocity can effectively reduce the content of carbon pollutants. The content of nitrogen pollutants in each flow pattern also reaches the maximum at G4 point, which are 213.6 mg/g, 205.2 mg/g, and 212.8 mg/g, respectively. Increasing the trunk velocity can effectively reduce the nitrogen content at points G1-G4, while increasing the flow velocity of the branch road can reduce the nitrogen content at points G5-G7. The distribution of phosphorus pollutants is complex, and the flow pattern needs to be adjusted according to different monitoring points.

Long-term deposition of fine sediments in Vienna's Danube floodplain before and after channelization

Investigations on the deposition processes in current alluvial landscapes are commonly affected by multiple forms of human interventions such as local hydraulic measures and reduced sediment transport caused by upstream reservoirs. The present study focuses on the sedimentation rates and floodplain accretion over 500 yr prior to major river engineering measures. A comprehensive borehole database and research on long-term fluvial dynamics in Vienna's Danube floodplain enabled us to correlate the thickness of fine sediment layers (silt and fine sand) with the morphological age of individual sites before the great regulation program 1870–1875. Five years after the onset of the sedimentation process on top of a gravel bar, the median deposition rate amounted to 18.60 cm yr−1. In the following decades the rate significantly decreased and leveled off after 300 yr with median annual rates between 0.15 and 0.10 cm. Five hundred years after the deposition process had started, the fine sediment layer reached a thickness of 2.64 m, of which half already had been deposited within the first 10 yr.Stabilization of riverbanks in 1870–1875 significantly boosted the long-term annual sedimentation rates by at least 23–41% (depending on the calculation method), although the volume of the suspended load decreased by 18–45% since around 1880. Assuming equal loads today would hypothetically yield a greater increase of the rates. As opposed to the historical situation featuring intensive lateral erosion, natural levee formation along the protected riverbanks has become a common phenomenon today. The thickness of fine sediment deposition and therefore the long-term “climax level” of the floodplain depends on numerous controlling factors including hydrological regime, sediment volume/size, stream power and riparian vegetation. Human interventions, i.e., bank stabilization, also alter the basic conditions for floodplain accretion, leading to greater sedimentation rates and higher floodplain levels.

Impact of Sediment Layer on Longitudinal Dispersion in Sewer Systems

Experiments focused on pollution transport and dispersion phenomena in conditions of low flow (low water depth and velocities) in sewers with bed sediment and deposits are presented. Such conditions occur very often in sewer pipes during dry weather flows. Experiments were performed in laboratory conditions. To simulate real hydraulic conditions in sewer pipes, sand of fraction 0.6–1.2 mm was placed on the bottom of the pipe. In total, we performed 23 experiments with 4 different thicknesses of sand sediment layers. The first scenario is without sediment, the second is with sediment filling 3.4% of the pipe diameter (sediment layer thickness = 8.5 mm), the third scenario represents sediment filling 10% of the pipe diameter (sediment layer thickness = 25 mm) and sediment fills 14% of the pipe diameter (sediment layer thickness = 35 mm) in the last scenario. For each thickness of the sediment layer, a set of tracer experiments with different flow rates was performed. The discharge ranges were from (0.14–2.5)·10−3 m3·s−1, corresponding to the range of Reynolds number 500–18,000. Results show that in the hydraulic conditions of a circular sewer pipe with the occurrence of sediment and deposits, the value of the longitudinal dispersion coefficient Dx decreases almost linearly with decrease of the flow rate (also with Reynolds number) to a certain limit (inflexion point), which is individual for each particular sediment thickness. Below this limit the value of the dispersion coefficient starts to rise again, together with increasing asymmetricity of the concentration distribution in time, caused by transient (dead) storage zones.

Crustal Structure Study in Lampung Region Using Teleseismic Receiver Function Analysis

Lampung region is seismically and volcanic active because located in subduction zone of Indo-Australian and Eurasian plate. We applied receiver function and stacking H-k analysis to estimate the crustal structure in Lampung region. We used teleseismic earthquake data (epicenter distance 30°-90°) and M>6 recorded at 3 seismic broadband stations owned by Agency for Meteorology Climatology and Geophysics (BMKG). Those stations are PSLI (located on Sebesi Island approximately 20 km from Anak Krakatau) represented volcanic arc zone, KASI (located on Kota Agung, Lampung) represented Sumatran Fault Zone and KLI (located on Kotabumi, Lampung) represented back-arc basin. Crustal thickness estimated at PSLI station 32-36 km, KASI station 36-40 km, and KLI station 30-36 km. Furthermore, in 3 stations P wave velocity estimated 4.1-11 km/s, S wave velocity 2.2-6.2 km/s, while vp/vs value estimated 1.7-2.05. We estimated Anak Krakatau volcano’s magma chamber beneath PSLI station in depth 16-30 km, Great Sumatran Fault structure in depth about 8-14 km beneath KASI station, and thick sediment layer about 4 km near surface beneath KLI station. This study result is expected to explain more detail crustal of Lampung region and can be useful for developing of BMKG’s seismic monitoring systems and other geophysical fields in future.

Tomographic Image of Shear Wave Structure of NE India Based on Analysis of Rayleigh Wave Data

The major scientific purpose of this work is to evaluate the geodynamic processes involved in the development of tectonic features of NE India and its surroundings. In this work, we have obtained tomographic images of the crust and uppermost mantle using inversion of Rayleigh waveform data to augment information about the subsurface gleaned by previous works. The images obtained reveal a very complicated tectonic regime. The Bengal Basin comprises a thick layer of sediments with the thickness increasing from west to east and a sudden steepening of the basement on the eastern side of the Eocene Hinge zone. The nature of the crust below the Bengal Basin varies from oceanic in the south to continental in the north. Indo-Gangetic and Brahmaputra River Valleys comprise ∼5–6-km-thick sediments. Crustal thickness in the higher Himalayas and southern Tibet is ∼70 km but varies between ∼30 and ∼40 km in the remaining part. Several patches of low-velocity medium present in the mid-to-lower crust of southern Tibet along and across the major rifts indicate the presence of either partially molten materials or aqueous fluid. Moho depth decreases drastically from west to east across the Yadong-Gulu rift indicating the complex effect of underthrusting of the Indian plate below the Eurasian plate. Crust and upper mantle below the Shillong Massif and Mikir Hills are at a shallow level. This observation indicates that tectonic forces contribute to the uprising of the Massif.

An Archaeological Perspective on Changes in the Course of the Yellow River and Changes in Civilization

The Yellow River has always been known for “easily silting up, easily bursting its banks, and easily shifting course” and its course has indeed changed many times. It did not undergo any large-scale course changes during the pre-Qin period, but instead followed the course given in the “Hanzhi 汉 志 (Treatises in the Book of Han).” The river recorded in the Yugong 禹 贡 (Tribute of Yu) is actually the Hanzhi river, and the he (river) recorded in the Yugong that passed through the counties of Xunxian and Neihuang actually followed the former course of the Qi River. The Yellow River’s large-scale course changes began in the Han dynasty. After two thousand years of frequent changes, a 6-15 meters thick layer of sediment formed in the lower reaches of the Yellow River, completely altering the natural landscape of hills, rivers and lakes that had existed in the pre-Qin lower Yellow River, and finally shaping today’s landscape of an endless plain. The course changes brought about a rupture in the development of civilization in this area, with most cities and towns destroyed. The changes in the ecological and living environment around the lower Yellow River over thousands of years were apparently related to the flooding and course changes of the Yellow River, but in reality were caused by human over-exploitation of natural resources.

Vulnerability Analysis of Earthquake Hazards in Tasikmalaya City Using Horizontal to Vertical Spectral Ratio (HVSR) Method

Tasikmalaya City is one of the regions in West Java Province that is often hit by earthquakes due to its location near the Indo-Australian Plate subduction zone towards the Eurasian Plate. The surface deposits in this city are alluvium and weakly consolidated step deposits which can cause wave amplification during an earthquake. As a mitigation effort, seismic zoning needs to be carried out to map the areas that will experience heavy damage when an earthquake occurs. This study uses the Horizontal to Vertical Spectral Ratio (HVSR) method which is applied to the microtremor recording data to obtain spatial variations in the predominant frequency and amplification values that can explain the characteristics of the geological layer beneath the surface. Based on the obtained results, the predominant frequency ranging from 0.7 to 9.5 Hz with the lowest frequency distribution in the eastern and northwestern parts, which indicates a thicker sediment layer. Amplification ranging from 1.2 to 12.6 with the distribution of higher values in the eastern, southeastern, and northwestern parts. The inversion of the HVSR curves was carried out to determine the value of shear wave velocity (V s ) in order to obtain a more detailed subsurface geological structure that can be used to determine the level of vulnerability of earthquake hazards. The Neighborhood Algorithm is used to find an optimum model. Based on the results of the inversion process, the V s ranging from 150 - 3054 m/s with lower V s values in the eastern, southeastern, and northwestern parts at depth of about 25 meters. The average value of shear wave velocity at a depth of 30 meters (V s 30) can also be used to determine the type of soil for geotechnical study. From the obtained V s 30data, the types of soil in the research area are classified into moderate soil, hard soil, and rocks.

Particle dispersion in turbulent sedimentary duct flows

A simplified geometric model of a circular tube with a sedimentary layer is proposed and named as sedimentary duct. Based on h = 1/4d (h is the thickness of sedimentary layer and d is the pipe diameter), the flow field (Re = 40000) and particle distribution (5, 10, 50 μm and St = 0.6, 2.5, 63) in the sedimentary duct are simulated using Large Eddy Simulation (LES) coupled with Lagrange Particle Tracking (LPT) method. As a result, four streamwise eddies are found in the sedimentary duct as distributed in pairs near the corner. The eddy center near ceiling is found to be farther from the corner than that from the floor. Small particles (5 μm, St = 0.6) tend to move with the secondary flow as their upward movements distribute in both sides. Their centripetal movement is near the floor and preferential distribution near the top. For large particles (50 μm, St = 63), it is the drag force that dominates their motion while for medium particles (10 μm, St = 2.5) lift force may have significant influence on their motion. This study is the first work to investigate the characteristics of particle behavior in turbulent sedimentary duct flows.

A Metamorphic Origin for Europa's Ocean

Europa likely contains an iron‐rich metal core. For it to have formed, temperatures within Europa reached ≳1250 K. Going up to that temperature, accreted chondritic minerals — for example, carbonates and phyllosilicates — would partially devolatilize. Here, we compute the amounts and compositions of exsolved volatiles. We find that volatiles released from the interior would have carried solutes, redox‐sensitive species, and could have generated a carbonic ocean in excess of Europa's present‐day hydrosphere, and potentially an early CO2 atmosphere. No late delivery of cometary water was necessary. Contrasting with prior work, CO2 could be the most abundant solute in the ocean, followed by Ca2+, SO42−, and HCO3−. However, gypsum precipitation going from the seafloor to the ice shell decreases the dissolved S/Cl ratio, such that Cl>S at the shallowest depths, consistent with recently inferred endogenous chlorides at Europa's surface. Gypsum would form a 3–10 km thick sedimentary layer at the seafloor.

Environmental factors shaping bacterial, archaeal and fungal community structure in hydrothermal sediments of Guaymas Basin, Gulf of California.

The flanking regions of Guaymas Basin, a young marginal rift basin located in the Gulf of California, are covered with thick sediment layers that are hydrothermally altered due to magmatic intrusions. To explore environmental controls on microbial community structure in this complex environment, we analyzed site- and depth-related patterns of microbial community composition (bacteria, archaea, and fungi) in hydrothermally influenced sediments with different thermal conditions, geochemical regimes, and extent of microbial mats. We compared communities in hot hydrothermal sediments (75-100°C at ~40 cm depth) covered by orange-pigmented Beggiatoaceae mats in the Cathedral Hill area, temperate sediments (25-30°C at ~40 cm depth) covered by yellow sulfur precipitates and filamentous sulfur oxidizers at the Aceto Balsamico location, hot sediments (>115°C at ~40 cm depth) with orange-pigmented mats surrounded by yellow and white mats at the Marker 14 location, and background, non-hydrothermal sediments (3.8°C at ~45 cm depth) overlain with ambient seawater. Whereas bacterial and archaeal communities are clearly structured by site-specific in-situ thermal gradients and geochemical conditions, fungal communities are generally structured by sediment depth. Unexpectedly, chytrid sequence biosignatures are ubiquitous in surficial sediments whereas deeper sediments contain diverse yeasts and filamentous fungi. In correlation analyses across different sites and sediment depths, fungal phylotypes correlate to each other to a much greater degree than Bacteria and Archaea do to each other or to fungi, further substantiating that site-specific in-situ thermal gradients and geochemical conditions that control bacteria and archaea do not extend to fungi.

Tectonic Structure and Relationship with Sinkhole Harzard in Bang Lung Area, Cho Don District, Bac Kan Province

By integration of remote sensing images analysis, geology, geomorphology, hydrogeology, geophysical method, and drilling data, the paper illustrates the structure tectonics, causes, and initial mechanism of a sinkhole forming in Bang Lung, Cho Don, Bac Kan province. The NE-SW normal slip faults are an essential fault system in the area, which created Bang Lung graben valley. This fault system also forms large fracture zones, creating advantage conditions for the groundwater runoff both vertically and horizontally to eroded and dissolved carbonate rock-forming underground karst caves. These are favorable natural conditions for forming a sinkhole. The sinkhole hazard in the Bang Lung area is initiated by some main factors such as tectonic activity, thickness, and characteristics of unconsolidated sediment layers, groundwater fluctuation, karst caves, and human activities. The most human impacts are mining exploitation and agricultural cultivation that promote sinkholes occurring faster and earlier. The horizontal and vertical movement of groundwater dragged the material on the ceiling karst caves into ground spaces. Thereby, weakening the cohesion of the unconsolidated sediment above caves leads to gravitational unbalance and creates a sinkhole. This study has also shown potential sinkhole areas in Bang Lung, which helps the authorities and local people in sinkhole prevention and mitigation mission.

Analysis of Earthquakes Potential Damages as a Disaster Mitigation Effort

Muara Bangkahulu District is one of Bengkulu Province Subdistricts, which is used as a place for higher education service centers, government office centers, and community residential areas. Muara Bangkahulu has the risk of being affected by an earthquake caused by its geological conditions. To avoid the potential damage due to earthquake, the PGA parameters, seismic vulnerability index, ground shear strain, and thickness of sediment layer (h) were analyzed in Muara Bangkahulu District as an effort to mitigate earthquakes. The purpose of this study is to describe the potential damage caused by the earthquake in Muara Bangkahulu District as a disaster mitigation effort. This research was a qualitative descriptive study using the literature study method. The results of the literature study which showed the value of PGA produced between 184.22 gal to 532.92 gal. Distribution of seismic vulnerability index values between 0.56 to 7.95. Distribution of ground shear strain values between 5.14 x10-5 to 7.42 x10-4. The thickness of the sediment layer (h) ranged from 8.13 meters to 61.31 meters. The largest PGA, IKS, GSS and h values are in Kualo Beach which is estimated to have a high level of risk for earthquake disasters with a correlation more than 74%. Thus, it can be concluded that the vicinity of Kualo Beach is the most potential and prone to earthquake damage.

Hydrodynamic Characteristics of Flow in a Strongly Curved Channel with Gravel Beds

This study experimentally and numerically investigated the hydrodynamic characteristics of a 180° curved open channel over rough bed under the condition of constant downstream water depth. Three different sizes of bed particles (the small, middle and big cases based upon the grain size diameter D50) were selected for flume tests. Three-dimensional instantaneous velocities obtained by the acoustic Doppler velocimeter (ADV) were used to analyze hydrodynamic characteristics. Additionally, the Renormalization-Group (RNG) turbulence model was employed for numerical simulations. Experimental results show that rough bed strengthens turbulence and increases turbulent kinetic energy along curved channels. The power spectra of the longitudinal velocity fluctuation satisfy the classic Kolmogorov −5/3 law in the inertial subrange, and the existence of rough bed shortens the inertial subrange and causes the flow reach the viscous dissipation range in advance. The contributions of sweeps and ejections are more important than those of the outward and inward interactions over a rough bed for the middle case. Flow-3D was adopted to simulate flow patterns on two rough bed settings with same surface roughness (skin drag) but different bed shapes (form drag): one is bed covered with thick bottom sediment layers along the curved part of the flume (the big case) as the experimental condition, and the other one is uniform bed along the entire flume (called the big case_flat only for simulations). Numerical simulations reveal that the secondary flow is confined to the near-bed area and the intensity of secondary flow is improved for both rough bed cases, possibly causing more serious bed erosion along a curved channel. In addition, the thick bottom sediments (the big case), i.e., larger form drag, can enhance turbulence strength near bed regions, enlarge the transverse range of secondary flow, and delay the shifting of the core region of maximum longitudinal velocity towards the concave bank.

LOCAL GEOLOGY AND SITE CLASS ASSESSMENT BASED ON MICROTREMOR DATA IN NORTH LOMBOK

Lombok Island is an active seismic area in Indonesia potentially hit by an earthquake due to located between two earthquake generators from the south and the North. Several large earthquakes rocked Lombok, an earthquake with a magnitude of 6.4 on July 29, 2018, and 7.0 on August 5, 2018. This study aims to determine the characteristics of the local site effect based on the dominant frequency value ( ), soil amplification ( ), sediment layer thickness (d), , dominant period (T0), and seismic vulnerability index ( ) and to comprehend the soil class (site class) based on the thickness of the sediment layer (d), and in the North Lombok region. The data used is secondary data from microtremor signal recordings in North Lombok Regency in 2018. Data processing used Geopsy software, and microtremor data were analyzed using the HVSR method. From processing the HVSR data, the dominant frequency value about (0.8 - 18) Hz, amplification value (1.7 – 9.7), dominant period value (0.05 – 1.2) seconds, seismic vulnerability index value (0.4 – 71) , and the value of in the study area (20.05 – 287.04) m/s. Based on microtremor analysis, the local site effect indicates that alluvium rocks caused stronger earthquake vibrations and more damage. Whereas the Kalibabak and Lekopiko formations caused fewer earthquake vibrations and less wear. Based on the dominant period and , area study classify as Site Class IV class E and Site Class III class D Copyright © 2021 IPR. All rights reserved.

Frictional stability of porous tuff breccia under subsurface pressure conditions and implications for shallow seismicity

Thick sediment layers frequently cover the Japan islands’ surface, and their frictional properties significantly affect the shallow slip behavior that occurs during earthquakes. However, laboratory data on the properties of the shallow zone remain limited. We collected tuff breccia samples from deep borehole cores in the Miocene “Green Tuff” formation, a major surface cover, and performed velocity-stepping friction tests on these samples under in situ stresses of 2 to 20 MPa to assess the velocity dependence of their frictional strength. The samples exhibit predominantly frictionally stable, velocity-strengthening behavior over the range of normal stresses tested, which supports the hypothesis that shallow sediment layers are seismically quiescent. This result is consistent with the low seismicity and attenuation of coseismic slip occurring in the shallow zone that is observed during regional earthquakes. Microstructural observations of the postmortem samples using optical and scanning electron microscopes indicate a fabric transition from boundary shear localization to distributed cataclastic flow with increasing normal stress. Our laboratory investigation of the depth-variable distribution of the frictional velocity dependence of a shallow sediment layer would provide further insight into the mechanical role for earthquake rupture dynamics and shallow seismicity.

A comparative study on natural gas hydrate accumulation models at active and passive continental margins

The comparative study on natural gas hydrate accumulation models between active and passive continental margins as well as their controlling factors is of great significance to the guidance of natural gas hydrate exploration. Based on the data and research results of international typical active continental margin hydrate accumulation areas such as the Cascadia margin of the Northeast Pacific, the Nankai trough, etc. and passive continental margin areas like the Blake Ridge, the models of the gas hydrate accumulation system are summarized and numerically simulated, and a preliminary comparison of active and passive continental margin reservoir accumulation models was also carried out. The following results were obtained. (1) The active continental margin provides a driving force and channel for vertical gas migration, which induces deep free gas and in-situ biogas to migrate along the fault. The migration channels are mainly faults, fractures and slumps produced by subduction–accretion. (2) Coarse-grained turbidity sediments such as silt and sandy silt have good porosity and permeability. Moreover, the sediment thickness on the accretionary wedge is large, which provides a good storage space for hydrate accumulation. (3) Numerical simulations of the Blake Ridge, and Niger Delta hydrate accumulation show that the passive continental margin lacks the lateral stress caused by the subduction zone compared with the active continental margin. However, due to the plastic materials in the thick sedimentary layer, high-pressure fluids and volcanic activities outside the continental margin, vertical accretion and tensile stress are generated and the accumulation rate of diffusion-type hydrates mainly depends on the methane supply rate. (4) Organic matter content, gas production rate, geothermal gradient and sedimentation rate at the passive continental margin have different effects on the spatial distribution of hydrate content. Mud volcanoes or diapir structures provide an ideal place for the formation and occurrence of hydrates.

Thickness of sediments in the Congo basin based on the analysis of decompensative gravity anomalies

The Congo basin is one of the largest intracratonic basins in the World, locating within a cold lithospheric plate. The structure of the thick sedimentary layer is investigated by seismic studies only in limited places. Here, we present a map of sedimentary thickness for the whole Congo basin, based on the inversion of the decompensative gravity anomalies. Contrary to the conventional Bouguer or isostatic gravity anomalies, the effect of the isostatic compensation of sediments is reduced in the decompensative anomalies, which provides a possibility to recover the full effect of low-density sediments. The calculated decompensative correction reaches ±70 mGal and exceeds the amplitude of the isostatic anomalies, especially in the long wavelengths. The final decompensative anomalies are negative over the whole basin and their patterns well correspond to its tectonic fragmentation. By inverting these anomalies with the predefined density-depth relationship we have obtained the sedimentary thickness map for the whole Congo basin. The maximum basement depth exceeding 10 km is found in the Lokoro basin and basins in the South. In the Lomami basin, thickness of sediments reaches about 6.5 km. It is important to note, that these deep depressions, are not covered by seismic studies. Furthermore, we found a new deep basin adjacent to the Lokonia High (on the SW side) that we propose to name as the Salonga basin.

Exploration for Platinum-Group Minerals in Till: A New Approach to the Recovery, Counting, Mineral Identification and Chemical Characterization

The discovery of new mineral deposits contributes to the sustainable mineral industrial development, which is essential to satisfy global resource demands. The exploration for new mineral resources is challenging in Canada since its vast lands are mostly covered by a thick layer of Quaternary sediments that obscure bedrock geology. In the course of the recent decades, indicator minerals recovered from till heavy mineral concentrates have been effectively used to prospect for a broad range of mineral deposits including diamond, gold, and base metals. However, these methods traditionally focus on (visual) investigation of the 0.25–2.0 mm grain-size fraction of unconsolidated sediments, whilst our observations emphasize on higher abundance, or sometimes unique occurrence of precious metal (Au, Ag, and platinum-group elements) minerals in the finer-grained fractions (<0.25 mm). This study aims to present the advantages of applying a mineral detection routine initially developed for gold grains counting and characterization, to platinum-group minerals in <50 µm till heavy mineral concentrates. This technique, which uses an automated scanning electron microscopy (SEM) equipped with an energy dispersive spectrometer, can provide quantitative mineralogical and semi-quantitative chemical data of heavy minerals of interest, simultaneously. This work presents the mineralogical and chemical characteristics, the grain size distribution, and the surface textures of 2664 discrete platinum-group mineral grains recovered from the processing of 5194 glacial sediment samples collected from different zones in the Canadian Shield (mostly Quebec and Ontario provinces). Fifty-eight different platinum-group mineral species have been identified to date, among which sperrylite (PtAs2) is by far the most abundant (n = 1488; 55.86%). Textural and mineral-chemical data suggest that detrital platinum-group minerals in the studied samples have been derived, at least in part, from Au-rich ore systems.