The cartography of floods by two different approaches enabled us to determine the limits and the advantages of each one of them. This cartography has been applied to the El Maleh basin situated in the South-East of Mo...The cartography of floods by two different approaches enabled us to determine the limits and the advantages of each one of them. This cartography has been applied to the El Maleh basin situated in the South-East of Morocco. The HEC-RAS approach consists of a combination of the surface hydrologic model and the digital terrain model data. This combination allows thereafter the mapping of the flood zones by the use of the WMS software. Thus it can predict the probability occurrence of floods at various frequency times and determine the intensity of the flood (depth and velocity of flood water) inside the El Maleh river by using the existing hydrological data. Otherwise FHI method approach introduces a multi-criteria index to assess flood risk areas in a regional scale. Six parameters (flow accumulation, distance from drainage network, drainage network density, slope, land use, and geology) were used in this last method. The relative importance of each parameter for the occurrence and severity of flood has been connected to weight values. These values are calculated following an Analytical Hierarchy Process: AHP, a method originally developed for the solution of Operational Research problems. According to their weight values, information of the different parameters is superimposed, resulting to flood risk mapping. The use of the WMS model allowed us to accurately map the flood risk areas with precisely flood heights in different levels. However, this method is only applicable for a small portion of the basin located downstream of the hydrological station. Otherwise, the FHI method allows it to map the entire basin but without giving an indication of the water levels reached by floods. One method does not exclude the other since both approaches provide important information for flood risk assessment.展开更多
Dikko area, Niger State, North Central Nigeria falls within the Pan-African thermo-tectonic event which occurred in Nigeria as in other parts of West Africa with widespread effect on the mineralization of rejuvenated ...Dikko area, Niger State, North Central Nigeria falls within the Pan-African thermo-tectonic event which occurred in Nigeria as in other parts of West Africa with widespread effect on the mineralization of rejuvenated basement and geosynclinal trough deposits. The Pan-African Belt in Nigeria forms part of the Benin-Nigeria (Dahomeyan) shield which is regarded as the southern prolongation of the circumcratonic Pan-African belt of the West African Craton. Structurally controlled, gold-bearing quartz veins were measured and studied in the area from an extensive geological ground investigation. Field and petrographical studies indicate that the Neoproterozoic rocks constitute gneisses, amphibolite schist, amphibolites and migmatites. The amphibolites are intruded by pegmatites. The associated quartz veins are generally concordant with the main N</span></span><span><span><span>-</span></span></span><span><span><span>S regional structural trend. The lithological and structural studies carried out in these areas have demonstrated the relationship between structures and mineralization and/or lithology. The main characteristics of the gold mineralization in the area appear to indicate hydrothermal mineralization in connection with shear zones. This study allows us to predict that quartz veins in the amphibolite can be mined at a profit and a detailed geochemical and resource valuation needs to be carried out for the Au and associated Galena and Ag mineralization to fully exploit their economic potential.展开更多
Understanding the levels,causes,and sources of fluoride in groundwater is critical for public health,effective water resource management,and sustainable utilization.This study employs multivariate statistical methods,...Understanding the levels,causes,and sources of fluoride in groundwater is critical for public health,effective water resource management,and sustainable utilization.This study employs multivariate statistical methods,hazard quotient assessment,and geochemical analyses,such as mineral saturation index,ionic activities,and Gibbs diagrams,to investigate the hydrochemical characteristics,causes,and noncarcinogenic risks of fluoride in Red bed groundwater and geothermal water in the Guang'an area and neighboring regions.Approximately 9%of the Red bed groundwater samples contain fluoride concentrations exceeding 1 mg·L^(-1).The predominant water types identified are Cl-Na and HCO_(3)-Na,primarily influenced by evapotranspiration.Low-fluoride groundwater and high-fluoride geothermal water exhibit distinct hydrochemical types HCO_(3)-Ca and SO_(4)-Ca,respectively,which are mainly related to the weathering of carbonate,sulfate,and fluorite-containing rocks.Correlation analysis reveals that fluoride content in Red bed groundwater is positively associated with Na^(+),Cl^(-),SO_(4)^(2-),and TDS(r^(2)=0.45-0.64,p<0.01),while in geothermal water,it correlates strongly with pH,K^(+),Ca^(2+),and Mg^(2+)(r^(2)=0.52-0.80,p<0.05).Mineral saturation indices and ionic activities indicate that ion exchange processes and the dissolution of minerals such as carbonatite and fluorite are important sources of fluoride in groundwater.The enrichment of fluorine in the Red bed groundwater is linked to evaporation,cation exchange and dissolution of fluorite,caused by the lithologic characteristics of the red bed in this area.However,it exhibits minimal correlation with the geothermal water in the adjacent area.The noncarcinogenic health risk assessment indicates that 7%(n=5)of Red bed groundwater points exceed the fluoride safety limit for adults,while 12%(n=8)exceed the limit for children.These findings underscore the importance of avoiding highly fluoridated red bed groundwater as a direct drinking source and enhancing groundwater monitoring to mitigate health risks associated with elevated fluoride levels.展开更多
The extra-peninsular Gondwana Group rocks are exposed in narrow patches within the Lesser Himalayan sequence of the NE-Arunachal Himalayas,India.The bulk of sediments for the sandstones of the Gondwana Group were deri...The extra-peninsular Gondwana Group rocks are exposed in narrow patches within the Lesser Himalayan sequence of the NE-Arunachal Himalayas,India.The bulk of sediments for the sandstones of the Gondwana Group were derived from felsic/acidic to intermediate igneous rocks,with minor mafic input from the upper continental crust(UCC),as supported by various discrimination diagrams based on quantification of detrital minerals coupled with sandstone geochemistry.The inputs from metamorphic sources in subordinate amounts cannot be ruled out,as indicated by quantification of the quartz varieties.These sediments were found to be sourced from the interior part of a craton or shield and recycled platformal sediments which were derived from both passive and active margin settings.The sediments experienced a wide variance in climatic conditions,from arid to humid,suffering low-moderate-inten-sity weathering(CIA:63.43;CIW:86.18;WIP:44.84;PIA:75.37;ICV:2.39;C-value:0.42;PF:0.49;Sr/Cu:9.23 and Rb/Sr:1.68)within the vicinity of the low plains to moderate hills.Additionally,redox-sensitive elements indicate the deposition of sediments under oxygenated or oxygen-rich conditions(U_(au):−2.91;Th/U:7.37;U/Th:0.18;V/Cr:1.71;δU:0.67 and Ce/Ce^(*):0.93).展开更多
The tectonic setting of the Himalaya during the Early Paleozoic has been a subject of enduring debate within the scientific community.Newly discovered bimodal intrusive rocks from comprehensive field geological invest...The tectonic setting of the Himalaya during the Early Paleozoic has been a subject of enduring debate within the scientific community.Newly discovered bimodal intrusive rocks from comprehensive field geological investigation in the central mountain range were subjected to petrology,zircon U-Pb geochronology,zircon Hf isotopes and whole-rock geochemistry analyses.The Palie bimodal intrusive rocks,comprising amphibolite and granitic gneiss,were formed at~489 Ma.The amphibolite exhibits geochemical characteristics consistent with N-MORB,while the granitic gneiss is classified as high potassium calc-alkaline peraluminous S-type granite.Both igneous rocks exhibit negative zirconε_(Hf)(t)values and display ancient T_(DM)^(C)ages.In conjunction with regional geological survey findings,it can be inferred that the formation of the Palie bimodal intrusive rocks occurred within a post-collision extensional tectonic setting.The amphibolite genesis involved partial melting of an enriched lithospheric mantle with some crustal assimilation,whereas the origin of the granitic gneiss can be attributed to partial melting of pre-existing felsic crust.Our data indicate that during the Early Paleozoic,the Himalaya underwent a transition from a pan-African collisional setting to post-collisional extensional tectonics.展开更多
The 2019 Typhoon Lekima triggered extensive landslides in Zhejiang Province.To explore the impact of typhoon paths on the distribution of landslide susceptibility,this study proposes a spatiotemporal zoning assessment...The 2019 Typhoon Lekima triggered extensive landslides in Zhejiang Province.To explore the impact of typhoon paths on the distribution of landslide susceptibility,this study proposes a spatiotemporal zoning assessment framework based on typhoon paths and inner rainbands.According to the typhoon landing path and its rainfall impact range,the study area is divided into the typhoon event period(TEP)and the annual non-typhoon period(ANP).The model uses 14 environmental factors,with the only difference between TEP and ANP being the rainfall index:TEP uses 48-hour rainfall during the typhoon,while ANP uses multi-year average annual rainfall.Modeling and comparative analysis were conducted using six machine learning models including random forest(RF)and support vector machine(SVM).The results show that the distribution pattern of high-risk landslide areas during TEP is significantly correlated with typhoon intensity:when the intensity is level 12,high-risk areas are radially distributed;at levels 10-11,they tend to concentrate asymmetrically along the coast;and when the intensity drops to below level 9,the overall susceptibility decreases significantly.During ANP,the distribution of landslides is relatively uniform with no obvious spatial concentration.Analysis on the factor contribution rate indicates that the rainfall weight in TEP is as high as 32.1%,making it the dominant factor;in ANP,the rainfall weight drops to 13.6%while the influence of factors such as slope and topographic wetness index increases,revealing differences in landslide formation mechanisms between the two periods.This study demonstrates that the spatiotemporal zoning method based on typhoon paths can effectively characterize the spatial susceptibility patterns of landslides and improve disaster identification capabilities under extreme weather conditions.The finally generated annual susceptibility zoning map divides the study area into four types of risk regions,providing a reference for dynamic monitoring and differentiated risk management of landslides in typhoon-prone areas.展开更多
The genesis and tectonic setting of Late Triassic volcanic rocks in the Ganzi–Litang ophiolitic mélange belt have long been a subject of contention.To elucidate these ambiguities,comprehensive petrological,geoch...The genesis and tectonic setting of Late Triassic volcanic rocks in the Ganzi–Litang ophiolitic mélange belt have long been a subject of contention.To elucidate these ambiguities,comprehensive petrological,geochemical,zircon U-Pb geochronological,and Sr-Nd isotopic analyses were conducted on the Luexigou basalts in the Litang area.This investigation has newly delineated a typical volcano-sedimentary sequence indicative of a mid-ocean ridge,with basalts dated to 215±3 Ma.These basalts exhibit geochemical characteristics akin to E-MORB,displaying relatively flat distribution patterns for rare earth elements and trace elements.They are notably depleted in high-field-strength elements(such as Nb and Ta),similar to volcanic arc basalts.展开更多
Geological strength index(GSI)has been widely used as an input parameter in predicting the strength and deformation properties of rock masses.This study derived a series of equations to satisfy the original GSI lines ...Geological strength index(GSI)has been widely used as an input parameter in predicting the strength and deformation properties of rock masses.This study derived a series of equations to satisfy the original GSI lines on the basic GSI chart.Two axes ranging from 0 to 100 were employed for surface conditions of the discontinuities and the structure of rock mass,which are independent of the input parameters.The derived equations can analyze GSI values ranging from 0 to 100 within±5%error.The engineering dimensions(EDs)such as the slope height,tunnel width,and foundation width were used together with representative elementary volume(REV)in jointed rock mass to define scale factor(sf)from 0.2 to 1 in evaluating the rock mass structure including joint pattern.The transformation of GSI into a scaledependent parameter based on engineering scale addresses a crucial requirement in various engineering applications.The improvements proposed in this study were applied to a real slope which was close to the time of failure.The results of stability assessments show that the new proposals have sufficient capability to define rock mass quality considering EDs.展开更多
The subsurface urban heat island(UHI)effect can provide latent clean geothermal potentials for cities.Understanding the city-wide subsurface temperature evolution under different land surfaces is significant in making...The subsurface urban heat island(UHI)effect can provide latent clean geothermal potentials for cities.Understanding the city-wide subsurface temperature evolution under different land surfaces is significant in making better use of geothermal energy.This research presents a study of Nanjing to identify the city-wide temperature distribution and evolution characteristics and further estimates the geothermal potential in Nanjing.Low-cost satellite-measured temperatures were used to derive the subsurface temperatures through a liner regression correction method,with higher accuracy verified by measured borehole data.The simulation results indicate that the concrete surface exhibits higher average temperatures than the grassland surface,resulting in relatively higher subsurface temperatures.The deviations of simulated subsurface temperatures are attributed to many factors,including the influence of complex atmospheric conditions on satellite-measured temperature accuracy,land surface heat absorption,and infiltration in the shallower layer.Furthermore,it reveals that the urban areas have 14.7%greater geothermal potential compared to rural areas,due to the subsurface UHI effect.This study provides a potentially efficient and convenient method for the estimation of potential urban geothermal energy.展开更多
Subduction polarity reversal typically occurs in intra-oceanic arc settings;the existence of an ancient intraoceanic arc and its associated back-arc system within the Neotethyan plate has been deliberated.In this stud...Subduction polarity reversal typically occurs in intra-oceanic arc settings;the existence of an ancient intraoceanic arc and its associated back-arc system within the Neotethyan plate has been deliberated.In this study,we investigate the possible role of subduction initiation of polarity reversal in the formation of Nagaland-Manipur ophiolite(NMO),evaluate the petrological and geochronological data and compare it with the neighboring natural examples of subduction polarity reversal of the Andaman-Nicobar ophiolite(ANO).The ancient intra-oceanic arc,namely the Incertus-Woyla Arc,and its associated back-arc remnant have been correlated with the back-arc mafic of the ANO.We found that the geochemical signatures of mafic rocks of NMO and ANO are comparable,and the available geochronology data of~145 Ma from the NMO basalt and chert fit well with the evolution and formation of the intra-oceanic arc,i.e.,Incertus-Woyla Arc.The evolution and age of the Incertus-Woyla Arc are between 135 and 150 Ma.Although the oldest age of the ANO has been reported from metamor-phic sole at about 106.4 and 105.3 Ma,the back-arc affinity of the amphibole has been credited to the back-arc spreading that occurred behind the Woyla Arc.Previous paleomagnetic and geochronological studies have suggested that the development of the back-arc basin behind the Incertus-Woyla Arc was a result of divergent double subduction.Therefore,we have inferred a similar scenario for the development of the back-arc affinity rocks of the NMO behind the Incertus-Woyla Arc and the reinterpretation for the evolution of the supra-subduction zone affinity rocks of NMO and ANO during subduction initiation after subduction polarity reversal.展开更多
Geodetic observations over the past several decades identify the Tien Shan as a prominent and active intracontinental mountain belt,characterized by a meridional shortening rate of up to 20 mm/a.The region has experie...Geodetic observations over the past several decades identify the Tien Shan as a prominent and active intracontinental mountain belt,characterized by a meridional shortening rate of up to 20 mm/a.The region has experienced significant seismic events,particularly along its northern boundary,highlighting the recurrent seismic activity in the Kyrgyz Republic.The Issyk-Ata fault,stretching 120 km from west to east in the northern Tien Shan,bounds from the north a young,growing anticline demarcating the foothills of the Kyrgyz Range and the Chui depression.This region is susceptible to strong earthquakes,posing a significant threat to the Chui region and Bishkek,the capital city with over a million residents.The youngest fault in the area is the Issyk-Ata fault,traversing the southern part of Bishkek,where modern construction has obscured its features.This study integrates remote sensing,detailed fieldwork,and paleoseismological investigations to map and analyze surface ruptures,quantify vertical displacements,and assess seismic hazards along the Issyk-Ata fault.Using optically stimulated luminescence and radiocarbon dating,we determined ages for documented paleoseismic events,placing two ancient earthquakes in the Holocene.Magnitude estimates suggest seismic events with magnitudes ranging from 6.6 to 7.1.In the Dzhal area,geological and geomorphological analysis yielded a longterm fault-slip rate of 1.15 mm/a.The Issyk-Ata fault shows variable rupture behavior,with distinct segments demonstrating different seismic characteristics and histories of activity.This variability necessitates comprehensive seismic hazard modeling to better understand and mitigate potential risks in the region.展开更多
The Knowledge Economic City (KEC) of Al Madinah Al Munawwarah is one of the major projects and represents the cornerstone for the new development activities for Al Madinah. The study area contains different geological...The Knowledge Economic City (KEC) of Al Madinah Al Munawwarah is one of the major projects and represents the cornerstone for the new development activities for Al Madinah. The study area contains different geological units dominated by basalt and overlain by surface deposits. The surface soils vary in thickness and can be classified into well-graded SAND with silt and gravel (SW-SM), silty SAND with gravel (SM), silty GRAVEL with sand (GM), and sandy SILTY clay (CL-ML). The subsurface soil obtained from the drilled boreholes can be classified into poorly graded GRAVEL (GP), well-graded GRAVEL with sand (GW), poorly graded GRAVEL with silt (GP-GM), silty CLAYEY gravel with sand (GC-GM), silty SAND with gravel (SM), silt with SAND (ML), and silty CLAY with sand (CL-ML), sandy lean CLAY (CL), and lean CLAY (CL). The relative density of the deposit and the different gravel sizes intercalated with the soil influenced the Standard Penetration Test (SPT) values. The SPT N values are high and approach refusal even at shallow depths. The shallow refusal depth (0.10 to 0.90 m) of the Dynamic Cone Penetration Test (DCPT) was observed. Generally, the soil can be described as inactive with low plasticity and dense to very dense consistency. The basalt of the KEC site is characterized by slightly (W2) to highly (W4) weathering, their strength ranges from moderate (S4) to very strong (S2), and the Rock Quality Designation (RQD) ranges from very poor (R5) to excellent (R1). The engineering geological map of the KEC characterized the geoengineering properties of the soil and rock materials and classified them into many zones. The high sulphate (SO42−) and chloride (Cl−) contents in groundwater call for protective measures for foundation concrete. The current study revealed that geohazard(s) mitigation measures concerning floods, volcanic eruptions, and earthquakes should be considered.展开更多
The title of the online version of the original article was revised.The title of the original article has been revised to:Hydrochemical characterization of surface waters in Northern Tehran:Integrating cluster-based t...The title of the online version of the original article was revised.The title of the original article has been revised to:Hydrochemical characterization of surface waters in Northern Tehran:Integrating cluster-based techniques with Self-Organizing Maps.展开更多
Water quality is a critical global issue,especially in urban and semi-urban regions where natural and anthropogenic factors significantly influence surface water systems.This study evaluates the hydrochemical characte...Water quality is a critical global issue,especially in urban and semi-urban regions where natural and anthropogenic factors significantly influence surface water systems.This study evaluates the hydrochemical characteristics of surface water in the North of Tehran Rivers(NTRs),an essential water resource in a rapidly urbanizing region,using advanced clustering techniques,including Hierarchical Clustering Analysis(HCA),Fuzzy CMeans(FCM),Genetic Algorithm Fuzzy C-Means(GAFCM),and Self-Organizing Map(SOM).The research aims to address the scientific challenge of understanding spatial and temporal variability in water quality,focusing on physicochemical parameters,hydrochemical facies,and contamination sources.Water samples from six rivers collected over four seasons in 2020 were analyzed and classified into distinct clusters based on their chemical composition,revealing significant seasonal and spatial differences.Results showed that FCM and GAFCM consistently categorized the NTRs into two clusters during winter and spring and three in summer and autumn.These findings were supported by HCA and SOM,which identified clusters corresponding to specific river segments and contamination levels.The primary hydrochemical processes identified were mineral dissolution and weathering,with calcite,dolomite,and aragonite significantly influencing water chemistry.Additionally,human activities,such as wastewater discharge,were shown to contribute to elevated sulfate,nitrate,and phosphate concentrations,further corroborated by microbial analyses.By integrating HCA,FCM,and GAFCM with an artificial neural network(ANN)-based clustering method(SOM),this study provides a robust framework for evaluating surface water quality.The findings,supported by Gibbs diagrams,Hounslow ion ratio,and saturation indices,highlight the dominance of rock weathering and human impacts in shaping the hydrochemical dynamics of the NTRs.These insights contribute to the scientific understanding of water quality dynamics and offer practical guidance for sustainable water resource management and environmental protection in developing urban areas.展开更多
The ocean bottom seismograph(OBS)is a powerful device deployed on the seafloor for acquiring marine seismic data,capable of detecting the multi-scale Earth’s interiors from submarine sediments to the mantle.Due to th...The ocean bottom seismograph(OBS)is a powerful device deployed on the seafloor for acquiring marine seismic data,capable of detecting the multi-scale Earth’s interiors from submarine sediments to the mantle.Due to the frequent use of free-fall deployment,it is challenging to accurately track its precise position.Additionally,the internal crystal oscillator clock of the OBS has limited accuracy,resulting in clock drift for long-term work on the seabed.To improve the reliability of OBS detections,it is crucial to calculate the precise OBS location and time correction.Focusing on accurately determining OBS position and timing,this study developed a positioning method that integrates time correction based on the Markov Chain Monte Carlo(MCMC)algorithm,utilizing travel times of direct water waves triggered by two-dimensional(2-D)shot lines or three-dimensional(3-D)airgun arrays.This newly developed method can simultaneously estimate accurate OBS location and time correction,incorporating bathymetric data into the inversion procedures to improve sampling efficiency and enhance the reliability of the final results.Synthetic tests with appropriate noise levels are performed independently to evaluate the feasibility and reliability of our method,indicating that it is robust enough to determine OBS location and time correction precisely.Finally,we use travel-time data recorded at three OBSs deployed in the Southwest Indian Ridge to relocate locations and calculate time corrections.The results exhibit high consistency when using 2-D and 3-D shot data,indicating that high-resolution bathymetric data plays a fingerprint role in inversion to evaluate precise OBS location and time correction.展开更多
Elemental concentrations of the siliciclastic sediments from a sedimentary basin provide clues on paleo-weathering,paleoclimate,provenance,and tectonic setting of the basin.Records for Permo-Triassic mass extinction a...Elemental concentrations of the siliciclastic sediments from a sedimentary basin provide clues on paleo-weathering,paleoclimate,provenance,and tectonic setting of the basin.Records for Permo-Triassic mass extinction and climatic fluctuations are commonly traced from the sediments in the Gondwana basins.Nevertheless,our understanding on sedimentation,provenance,and regional tectonics of the Raniganj Basin,a Gondwana basin in the eastern India is poor.Minerals including clay particles and major and trace element concentrations of the siliciclastic sediments from different formations of the Raniganj Basin have been studied to establish the paleo-weathering,paleoclimate,provenance,and tectonic settings of the basin.This study suggests that the Talchir Formation experienced cold and dry climatic conditions at the sediment source area,while the Barakar,Raniganj,and Panchet formations had prevailing semiarid climates.The sources of the siliciclastic sediments are from the felsic rocks of the Chotanagpur Granite Gneissic Complex(CGGC).Further,the geochemical results suggest a rift-like(passive)tectonic setting for the Raniganj Basin,while few samples represent the collision tectonic setting of the basement CGGC,formed due to collision of major Indian blocks during the Paleo-Neoproterozoic time.展开更多
文摘The cartography of floods by two different approaches enabled us to determine the limits and the advantages of each one of them. This cartography has been applied to the El Maleh basin situated in the South-East of Morocco. The HEC-RAS approach consists of a combination of the surface hydrologic model and the digital terrain model data. This combination allows thereafter the mapping of the flood zones by the use of the WMS software. Thus it can predict the probability occurrence of floods at various frequency times and determine the intensity of the flood (depth and velocity of flood water) inside the El Maleh river by using the existing hydrological data. Otherwise FHI method approach introduces a multi-criteria index to assess flood risk areas in a regional scale. Six parameters (flow accumulation, distance from drainage network, drainage network density, slope, land use, and geology) were used in this last method. The relative importance of each parameter for the occurrence and severity of flood has been connected to weight values. These values are calculated following an Analytical Hierarchy Process: AHP, a method originally developed for the solution of Operational Research problems. According to their weight values, information of the different parameters is superimposed, resulting to flood risk mapping. The use of the WMS model allowed us to accurately map the flood risk areas with precisely flood heights in different levels. However, this method is only applicable for a small portion of the basin located downstream of the hydrological station. Otherwise, the FHI method allows it to map the entire basin but without giving an indication of the water levels reached by floods. One method does not exclude the other since both approaches provide important information for flood risk assessment.
文摘Dikko area, Niger State, North Central Nigeria falls within the Pan-African thermo-tectonic event which occurred in Nigeria as in other parts of West Africa with widespread effect on the mineralization of rejuvenated basement and geosynclinal trough deposits. The Pan-African Belt in Nigeria forms part of the Benin-Nigeria (Dahomeyan) shield which is regarded as the southern prolongation of the circumcratonic Pan-African belt of the West African Craton. Structurally controlled, gold-bearing quartz veins were measured and studied in the area from an extensive geological ground investigation. Field and petrographical studies indicate that the Neoproterozoic rocks constitute gneisses, amphibolite schist, amphibolites and migmatites. The amphibolites are intruded by pegmatites. The associated quartz veins are generally concordant with the main N</span></span><span><span><span>-</span></span></span><span><span><span>S regional structural trend. The lithological and structural studies carried out in these areas have demonstrated the relationship between structures and mineralization and/or lithology. The main characteristics of the gold mineralization in the area appear to indicate hydrothermal mineralization in connection with shear zones. This study allows us to predict that quartz veins in the amphibolite can be mined at a profit and a detailed geochemical and resource valuation needs to be carried out for the Au and associated Galena and Ag mineralization to fully exploit their economic potential.
基金supported by the China Geological Survey Project(Nos.DD20220864 and DD20243077).
文摘Understanding the levels,causes,and sources of fluoride in groundwater is critical for public health,effective water resource management,and sustainable utilization.This study employs multivariate statistical methods,hazard quotient assessment,and geochemical analyses,such as mineral saturation index,ionic activities,and Gibbs diagrams,to investigate the hydrochemical characteristics,causes,and noncarcinogenic risks of fluoride in Red bed groundwater and geothermal water in the Guang'an area and neighboring regions.Approximately 9%of the Red bed groundwater samples contain fluoride concentrations exceeding 1 mg·L^(-1).The predominant water types identified are Cl-Na and HCO_(3)-Na,primarily influenced by evapotranspiration.Low-fluoride groundwater and high-fluoride geothermal water exhibit distinct hydrochemical types HCO_(3)-Ca and SO_(4)-Ca,respectively,which are mainly related to the weathering of carbonate,sulfate,and fluorite-containing rocks.Correlation analysis reveals that fluoride content in Red bed groundwater is positively associated with Na^(+),Cl^(-),SO_(4)^(2-),and TDS(r^(2)=0.45-0.64,p<0.01),while in geothermal water,it correlates strongly with pH,K^(+),Ca^(2+),and Mg^(2+)(r^(2)=0.52-0.80,p<0.05).Mineral saturation indices and ionic activities indicate that ion exchange processes and the dissolution of minerals such as carbonatite and fluorite are important sources of fluoride in groundwater.The enrichment of fluorine in the Red bed groundwater is linked to evaporation,cation exchange and dissolution of fluorite,caused by the lithologic characteristics of the red bed in this area.However,it exhibits minimal correlation with the geothermal water in the adjacent area.The noncarcinogenic health risk assessment indicates that 7%(n=5)of Red bed groundwater points exceed the fluoride safety limit for adults,while 12%(n=8)exceed the limit for children.These findings underscore the importance of avoiding highly fluoridated red bed groundwater as a direct drinking source and enhancing groundwater monitoring to mitigate health risks associated with elevated fluoride levels.
文摘The extra-peninsular Gondwana Group rocks are exposed in narrow patches within the Lesser Himalayan sequence of the NE-Arunachal Himalayas,India.The bulk of sediments for the sandstones of the Gondwana Group were derived from felsic/acidic to intermediate igneous rocks,with minor mafic input from the upper continental crust(UCC),as supported by various discrimination diagrams based on quantification of detrital minerals coupled with sandstone geochemistry.The inputs from metamorphic sources in subordinate amounts cannot be ruled out,as indicated by quantification of the quartz varieties.These sediments were found to be sourced from the interior part of a craton or shield and recycled platformal sediments which were derived from both passive and active margin settings.The sediments experienced a wide variance in climatic conditions,from arid to humid,suffering low-moderate-inten-sity weathering(CIA:63.43;CIW:86.18;WIP:44.84;PIA:75.37;ICV:2.39;C-value:0.42;PF:0.49;Sr/Cu:9.23 and Rb/Sr:1.68)within the vicinity of the low plains to moderate hills.Additionally,redox-sensitive elements indicate the deposition of sediments under oxygenated or oxygen-rich conditions(U_(au):−2.91;Th/U:7.37;U/Th:0.18;V/Cr:1.71;δU:0.67 and Ce/Ce^(*):0.93).
基金supported by the China Geological Survey Program(Grant No.DD20220989)the National Natural Science Foundation of China(Grant No.41972118)。
文摘The tectonic setting of the Himalaya during the Early Paleozoic has been a subject of enduring debate within the scientific community.Newly discovered bimodal intrusive rocks from comprehensive field geological investigation in the central mountain range were subjected to petrology,zircon U-Pb geochronology,zircon Hf isotopes and whole-rock geochemistry analyses.The Palie bimodal intrusive rocks,comprising amphibolite and granitic gneiss,were formed at~489 Ma.The amphibolite exhibits geochemical characteristics consistent with N-MORB,while the granitic gneiss is classified as high potassium calc-alkaline peraluminous S-type granite.Both igneous rocks exhibit negative zirconε_(Hf)(t)values and display ancient T_(DM)^(C)ages.In conjunction with regional geological survey findings,it can be inferred that the formation of the Palie bimodal intrusive rocks occurred within a post-collision extensional tectonic setting.The amphibolite genesis involved partial melting of an enriched lithospheric mantle with some crustal assimilation,whereas the origin of the granitic gneiss can be attributed to partial melting of pre-existing felsic crust.Our data indicate that during the Early Paleozoic,the Himalaya underwent a transition from a pan-African collisional setting to post-collisional extensional tectonics.
基金supported by the project of National Natural Science Foundation of China(Grant No.42371203 and U21A2032)the project Financial Fund of Sichuan Institute of Geological Survey(SCIGSCZDXM-2024008)+1 种基金Sichuan Provincial Science and Technology Department Program Funding(No.2025YFHZ0010)Science and Technology Program of Aba City(NO.R24YYJSYJ0001)。
文摘The 2019 Typhoon Lekima triggered extensive landslides in Zhejiang Province.To explore the impact of typhoon paths on the distribution of landslide susceptibility,this study proposes a spatiotemporal zoning assessment framework based on typhoon paths and inner rainbands.According to the typhoon landing path and its rainfall impact range,the study area is divided into the typhoon event period(TEP)and the annual non-typhoon period(ANP).The model uses 14 environmental factors,with the only difference between TEP and ANP being the rainfall index:TEP uses 48-hour rainfall during the typhoon,while ANP uses multi-year average annual rainfall.Modeling and comparative analysis were conducted using six machine learning models including random forest(RF)and support vector machine(SVM).The results show that the distribution pattern of high-risk landslide areas during TEP is significantly correlated with typhoon intensity:when the intensity is level 12,high-risk areas are radially distributed;at levels 10-11,they tend to concentrate asymmetrically along the coast;and when the intensity drops to below level 9,the overall susceptibility decreases significantly.During ANP,the distribution of landslides is relatively uniform with no obvious spatial concentration.Analysis on the factor contribution rate indicates that the rainfall weight in TEP is as high as 32.1%,making it the dominant factor;in ANP,the rainfall weight drops to 13.6%while the influence of factors such as slope and topographic wetness index increases,revealing differences in landslide formation mechanisms between the two periods.This study demonstrates that the spatiotemporal zoning method based on typhoon paths can effectively characterize the spatial susceptibility patterns of landslides and improve disaster identification capabilities under extreme weather conditions.The finally generated annual susceptibility zoning map divides the study area into four types of risk regions,providing a reference for dynamic monitoring and differentiated risk management of landslides in typhoon-prone areas.
基金supported by the State Key Program of National Natural Science of China(Grant No.42230311)the China Geological Survey(Grant No.DD20243073).
文摘The genesis and tectonic setting of Late Triassic volcanic rocks in the Ganzi–Litang ophiolitic mélange belt have long been a subject of contention.To elucidate these ambiguities,comprehensive petrological,geochemical,zircon U-Pb geochronological,and Sr-Nd isotopic analyses were conducted on the Luexigou basalts in the Litang area.This investigation has newly delineated a typical volcano-sedimentary sequence indicative of a mid-ocean ridge,with basalts dated to 215±3 Ma.These basalts exhibit geochemical characteristics akin to E-MORB,displaying relatively flat distribution patterns for rare earth elements and trace elements.They are notably depleted in high-field-strength elements(such as Nb and Ta),similar to volcanic arc basalts.
文摘Geological strength index(GSI)has been widely used as an input parameter in predicting the strength and deformation properties of rock masses.This study derived a series of equations to satisfy the original GSI lines on the basic GSI chart.Two axes ranging from 0 to 100 were employed for surface conditions of the discontinuities and the structure of rock mass,which are independent of the input parameters.The derived equations can analyze GSI values ranging from 0 to 100 within±5%error.The engineering dimensions(EDs)such as the slope height,tunnel width,and foundation width were used together with representative elementary volume(REV)in jointed rock mass to define scale factor(sf)from 0.2 to 1 in evaluating the rock mass structure including joint pattern.The transformation of GSI into a scaledependent parameter based on engineering scale addresses a crucial requirement in various engineering applications.The improvements proposed in this study were applied to a real slope which was close to the time of failure.The results of stability assessments show that the new proposals have sufficient capability to define rock mass quality considering EDs.
基金supports from the National Natural Science Foundation of China(Grant Nos.42222707,41761134089)are gratefully acknowledged.
文摘The subsurface urban heat island(UHI)effect can provide latent clean geothermal potentials for cities.Understanding the city-wide subsurface temperature evolution under different land surfaces is significant in making better use of geothermal energy.This research presents a study of Nanjing to identify the city-wide temperature distribution and evolution characteristics and further estimates the geothermal potential in Nanjing.Low-cost satellite-measured temperatures were used to derive the subsurface temperatures through a liner regression correction method,with higher accuracy verified by measured borehole data.The simulation results indicate that the concrete surface exhibits higher average temperatures than the grassland surface,resulting in relatively higher subsurface temperatures.The deviations of simulated subsurface temperatures are attributed to many factors,including the influence of complex atmospheric conditions on satellite-measured temperature accuracy,land surface heat absorption,and infiltration in the shallower layer.Furthermore,it reveals that the urban areas have 14.7%greater geothermal potential compared to rural areas,due to the subsurface UHI effect.This study provides a potentially efficient and convenient method for the estimation of potential urban geothermal energy.
基金supported by the Ministry of Earth Sciences(MoES),Government of India,New Delhi,through a research grant(No.MoES/P.O.(Geo)/80/2015)to A.K.Singh.
文摘Subduction polarity reversal typically occurs in intra-oceanic arc settings;the existence of an ancient intraoceanic arc and its associated back-arc system within the Neotethyan plate has been deliberated.In this study,we investigate the possible role of subduction initiation of polarity reversal in the formation of Nagaland-Manipur ophiolite(NMO),evaluate the petrological and geochronological data and compare it with the neighboring natural examples of subduction polarity reversal of the Andaman-Nicobar ophiolite(ANO).The ancient intra-oceanic arc,namely the Incertus-Woyla Arc,and its associated back-arc remnant have been correlated with the back-arc mafic of the ANO.We found that the geochemical signatures of mafic rocks of NMO and ANO are comparable,and the available geochronology data of~145 Ma from the NMO basalt and chert fit well with the evolution and formation of the intra-oceanic arc,i.e.,Incertus-Woyla Arc.The evolution and age of the Incertus-Woyla Arc are between 135 and 150 Ma.Although the oldest age of the ANO has been reported from metamor-phic sole at about 106.4 and 105.3 Ma,the back-arc affinity of the amphibole has been credited to the back-arc spreading that occurred behind the Woyla Arc.Previous paleomagnetic and geochronological studies have suggested that the development of the back-arc basin behind the Incertus-Woyla Arc was a result of divergent double subduction.Therefore,we have inferred a similar scenario for the development of the back-arc affinity rocks of the NMO behind the Incertus-Woyla Arc and the reinterpretation for the evolution of the supra-subduction zone affinity rocks of NMO and ANO during subduction initiation after subduction polarity reversal.
基金financial support of the Faculty Research Grant project of the American University of Central Asia(AUCA)supported by the Ministry of Education of the Republic of Korea and the National Research Foundation of Korea(NRF-2023S1A5B5A16080131)。
文摘Geodetic observations over the past several decades identify the Tien Shan as a prominent and active intracontinental mountain belt,characterized by a meridional shortening rate of up to 20 mm/a.The region has experienced significant seismic events,particularly along its northern boundary,highlighting the recurrent seismic activity in the Kyrgyz Republic.The Issyk-Ata fault,stretching 120 km from west to east in the northern Tien Shan,bounds from the north a young,growing anticline demarcating the foothills of the Kyrgyz Range and the Chui depression.This region is susceptible to strong earthquakes,posing a significant threat to the Chui region and Bishkek,the capital city with over a million residents.The youngest fault in the area is the Issyk-Ata fault,traversing the southern part of Bishkek,where modern construction has obscured its features.This study integrates remote sensing,detailed fieldwork,and paleoseismological investigations to map and analyze surface ruptures,quantify vertical displacements,and assess seismic hazards along the Issyk-Ata fault.Using optically stimulated luminescence and radiocarbon dating,we determined ages for documented paleoseismic events,placing two ancient earthquakes in the Holocene.Magnitude estimates suggest seismic events with magnitudes ranging from 6.6 to 7.1.In the Dzhal area,geological and geomorphological analysis yielded a longterm fault-slip rate of 1.15 mm/a.The Issyk-Ata fault shows variable rupture behavior,with distinct segments demonstrating different seismic characteristics and histories of activity.This variability necessitates comprehensive seismic hazard modeling to better understand and mitigate potential risks in the region.
文摘The Knowledge Economic City (KEC) of Al Madinah Al Munawwarah is one of the major projects and represents the cornerstone for the new development activities for Al Madinah. The study area contains different geological units dominated by basalt and overlain by surface deposits. The surface soils vary in thickness and can be classified into well-graded SAND with silt and gravel (SW-SM), silty SAND with gravel (SM), silty GRAVEL with sand (GM), and sandy SILTY clay (CL-ML). The subsurface soil obtained from the drilled boreholes can be classified into poorly graded GRAVEL (GP), well-graded GRAVEL with sand (GW), poorly graded GRAVEL with silt (GP-GM), silty CLAYEY gravel with sand (GC-GM), silty SAND with gravel (SM), silt with SAND (ML), and silty CLAY with sand (CL-ML), sandy lean CLAY (CL), and lean CLAY (CL). The relative density of the deposit and the different gravel sizes intercalated with the soil influenced the Standard Penetration Test (SPT) values. The SPT N values are high and approach refusal even at shallow depths. The shallow refusal depth (0.10 to 0.90 m) of the Dynamic Cone Penetration Test (DCPT) was observed. Generally, the soil can be described as inactive with low plasticity and dense to very dense consistency. The basalt of the KEC site is characterized by slightly (W2) to highly (W4) weathering, their strength ranges from moderate (S4) to very strong (S2), and the Rock Quality Designation (RQD) ranges from very poor (R5) to excellent (R1). The engineering geological map of the KEC characterized the geoengineering properties of the soil and rock materials and classified them into many zones. The high sulphate (SO42−) and chloride (Cl−) contents in groundwater call for protective measures for foundation concrete. The current study revealed that geohazard(s) mitigation measures concerning floods, volcanic eruptions, and earthquakes should be considered.
文摘The title of the online version of the original article was revised.The title of the original article has been revised to:Hydrochemical characterization of surface waters in Northern Tehran:Integrating cluster-based techniques with Self-Organizing Maps.
文摘Water quality is a critical global issue,especially in urban and semi-urban regions where natural and anthropogenic factors significantly influence surface water systems.This study evaluates the hydrochemical characteristics of surface water in the North of Tehran Rivers(NTRs),an essential water resource in a rapidly urbanizing region,using advanced clustering techniques,including Hierarchical Clustering Analysis(HCA),Fuzzy CMeans(FCM),Genetic Algorithm Fuzzy C-Means(GAFCM),and Self-Organizing Map(SOM).The research aims to address the scientific challenge of understanding spatial and temporal variability in water quality,focusing on physicochemical parameters,hydrochemical facies,and contamination sources.Water samples from six rivers collected over four seasons in 2020 were analyzed and classified into distinct clusters based on their chemical composition,revealing significant seasonal and spatial differences.Results showed that FCM and GAFCM consistently categorized the NTRs into two clusters during winter and spring and three in summer and autumn.These findings were supported by HCA and SOM,which identified clusters corresponding to specific river segments and contamination levels.The primary hydrochemical processes identified were mineral dissolution and weathering,with calcite,dolomite,and aragonite significantly influencing water chemistry.Additionally,human activities,such as wastewater discharge,were shown to contribute to elevated sulfate,nitrate,and phosphate concentrations,further corroborated by microbial analyses.By integrating HCA,FCM,and GAFCM with an artificial neural network(ANN)-based clustering method(SOM),this study provides a robust framework for evaluating surface water quality.The findings,supported by Gibbs diagrams,Hounslow ion ratio,and saturation indices,highlight the dominance of rock weathering and human impacts in shaping the hydrochemical dynamics of the NTRs.These insights contribute to the scientific understanding of water quality dynamics and offer practical guidance for sustainable water resource management and environmental protection in developing urban areas.
基金The National Key Research and Development Program of China under contract No.2021YFC3101404the National Natural Science Foundation of China under contract Nos 42106068,42376052,42276064 and 42276075+1 种基金the Foundation of State Key Laboratory of Submarine Geoscience under contract No.sglkfkt2025-2the Zhejiang Provincial Natural Science Foundation of China under contract No.LZ23D060004.
文摘The ocean bottom seismograph(OBS)is a powerful device deployed on the seafloor for acquiring marine seismic data,capable of detecting the multi-scale Earth’s interiors from submarine sediments to the mantle.Due to the frequent use of free-fall deployment,it is challenging to accurately track its precise position.Additionally,the internal crystal oscillator clock of the OBS has limited accuracy,resulting in clock drift for long-term work on the seabed.To improve the reliability of OBS detections,it is crucial to calculate the precise OBS location and time correction.Focusing on accurately determining OBS position and timing,this study developed a positioning method that integrates time correction based on the Markov Chain Monte Carlo(MCMC)algorithm,utilizing travel times of direct water waves triggered by two-dimensional(2-D)shot lines or three-dimensional(3-D)airgun arrays.This newly developed method can simultaneously estimate accurate OBS location and time correction,incorporating bathymetric data into the inversion procedures to improve sampling efficiency and enhance the reliability of the final results.Synthetic tests with appropriate noise levels are performed independently to evaluate the feasibility and reliability of our method,indicating that it is robust enough to determine OBS location and time correction precisely.Finally,we use travel-time data recorded at three OBSs deployed in the Southwest Indian Ridge to relocate locations and calculate time corrections.The results exhibit high consistency when using 2-D and 3-D shot data,indicating that high-resolution bathymetric data plays a fingerprint role in inversion to evaluate precise OBS location and time correction.
基金funded by SERB-DST,New Delhi,India for Early Career Research(ECR/2016/001100)during 2017 to 2021.
文摘Elemental concentrations of the siliciclastic sediments from a sedimentary basin provide clues on paleo-weathering,paleoclimate,provenance,and tectonic setting of the basin.Records for Permo-Triassic mass extinction and climatic fluctuations are commonly traced from the sediments in the Gondwana basins.Nevertheless,our understanding on sedimentation,provenance,and regional tectonics of the Raniganj Basin,a Gondwana basin in the eastern India is poor.Minerals including clay particles and major and trace element concentrations of the siliciclastic sediments from different formations of the Raniganj Basin have been studied to establish the paleo-weathering,paleoclimate,provenance,and tectonic settings of the basin.This study suggests that the Talchir Formation experienced cold and dry climatic conditions at the sediment source area,while the Barakar,Raniganj,and Panchet formations had prevailing semiarid climates.The sources of the siliciclastic sediments are from the felsic rocks of the Chotanagpur Granite Gneissic Complex(CGGC).Further,the geochemical results suggest a rift-like(passive)tectonic setting for the Raniganj Basin,while few samples represent the collision tectonic setting of the basement CGGC,formed due to collision of major Indian blocks during the Paleo-Neoproterozoic time.
