Geological setting,facies characteristics,and geochemistry,including TGA(thermo-gravimetric analysis)of Paleogene deposits in east Beni Suef region(Egypt),were studied in the present work.Lithostratigraphically,the ar...Geological setting,facies characteristics,and geochemistry,including TGA(thermo-gravimetric analysis)of Paleogene deposits in east Beni Suef region(Egypt),were studied in the present work.Lithostratigraphically,the area consists of three rock units,arranged from oldest to youngest:Tarbul Member of Beni Suef Formation(MiddleLate Eocene),Maadi Formation(Late Eocene),and Gebel Ahmar Formation(Oligocene),this last formation registered for the first time in the east of Beni Suef area(Egypt).Seven microfacies types(F1-F7)were determined by the microscopic examination of the studied samples in low-to high-energy and shallow-subtidal marine conditions.The lithostratigraphic,petrological,and geochemical results revealed that the Eocene succession in the present area is composed mainly of carbonates as well as siliciclastics.The Oligocene Gebel Ahmar Formation consists mainly of silica and iron oxides.The enrichment of the rock units with iron oxides in the studied area,as well as the high proportions of trace elements such as Zr,Ba,V,and Sr,in particular in the Gebel Ahmar Formation,reflects the influence of the hydrothermal solutions during the Oligocene.TGA,which monitors weight changes during heating at a constant rate,was used to determine the thermal stability and volatile component content of the materials.The ferruginous sandstone of Gebel Ahmar Formation exhibits various decomposition phases when exposed to thermal inf luences,with TGA indicating an initial mass decrease starting at 61.8℃.In contrast,the ferruginous limestone of the Maadi Formation shows a single-phase mass decrease between 650 and 875℃.展开更多
In the Fatira(Abu Zawal)mine area,located in the northern Eastern Desert of Egypt,fieldwork and mineralogical analysis,integrated with machine learning techniques applied to Landsat-8 OLI,ASTER,and Sentinel-2 multi-sp...In the Fatira(Abu Zawal)mine area,located in the northern Eastern Desert of Egypt,fieldwork and mineralogical analysis,integrated with machine learning techniques applied to Landsat-8 OLI,ASTER,and Sentinel-2 multi-spectral imagery(MSI)data delineate gold-sulfide mineralization in altered rocks.Gold(Au)anomalies in hydrothermal breccias and quartz veins are associated with NE-oriented felsite dykes and silicified granitic rocks.Two main alteration types are identified:a pyrite-sericite-quartz and a sulfide-chlorite-carbonate assemblage,locally with dispersed free-milling Au specks.Dimensionality reduction techniques,including principal component analysis(PCA)and independent component analysis(ICA),enabled mapping of alteration types.Sentinel-2 PC125 composite images offered efficient lithological differentiation,while supervised classifications,i.e.,the support vector machine(SVM)of Landsat-8 yielded an accuracy of 88.55%and a Kappa value of 0.86.ASTER mineral indices contributed to map hydrothermal alteration mineral phases,including sericite,muscovite,kaolinite,and iron oxides.Results indicate that post-magmatic epigenetic hydrothermal activity significantly contributed to the Au-sulfide mineralization in the Fatira area,distinguishing it from the more prevalent orogenic gold deposits in the region.展开更多
Fractal geometry quantitatively analyzes the irregular distribution of geological features,highlighting the dynamic aspects of tectonics,seismic heterogeneity,and geological maturity.This study analyzed the active fau...Fractal geometry quantitatively analyzes the irregular distribution of geological features,highlighting the dynamic aspects of tectonics,seismic heterogeneity,and geological maturity.This study analyzed the active fault data along the Kuhbanan fault zone in southeastern Iran by applying the boxcounting method and observing the changes in Coulomb stress and tried to find the potential triggering parts.The entire region was divided into 16subzones with the box-counting method,and then the fractal dimension(D)in each zone was calculated.The analysis of the fractal dimension for active faults and earthquake epicenters along with the seismicity parameter(b)and their ratio in the Kuhbanan region indicates an imbalance between seismic fractals and faults.This finding suggests that the area may have the potential for future earthquakes or hidden faults.In conjunction with b-value and changes in Coulomb stress change,D-value analysis reveals intense tectonic activity and stress accumulation,particularly within the Ravar,Zarand,and Kianshahr sections.It may be considered a potential location for future earthquakes.The changes in Coulomb stress resulting from the 2005Dahuieh earthquake have also placed this region within the stress accumulation zone,potentially triggering the mentioned areas.This integrative approach,backed by historical earthquake data,highlights the impact of fault geometry and stress dynamics,offering an enhanced framework for earthquake forecasting and seismic risk mitigation applicable to other tectonically active areas within the Iranian plateau.展开更多
Offshore Nile Delta in Egypt represents an enormous hydrocarbon province with recent projected gas and condensate discoveries of more than 50 trillion cubic feet“TCF”.Most of these occur in the post-salt hydrocarbon...Offshore Nile Delta in Egypt represents an enormous hydrocarbon province with recent projected gas and condensate discoveries of more than 50 trillion cubic feet“TCF”.Most of these occur in the post-salt hydrocarbon plays where biogenic gases are dominant.This study integrates organic geochemistry,seismic geomorphology and petrophysics in order to decipher the origin,and accumulation conditions of the wet gas/condensate blend in the Upper Miocene sub-salt Wakar Formation sandstones in Port Fouad Marine“PFM”Field,offshore Nile Delta.Hydrocarbon pay zones are scattered thin(<10 m)sandstones deposited in as turbiditic channel/levee complex facies.Spatial distribution of vertical gas chimneys(~2 km wide)rooting-down to the Messinian Rosetta salt is associated with the lateral pinching-out of the turbiditic sandstones.Organically-rich(total organic carbon“TOC”>1 w.t.%,hydrogen index“HI”>200 mgHC/gTOC)and mature(Tmax>430℃,vitrinite reflectance“VR”>0.6%R_(o)),source rocks are restricted to Upper Miocene Wakar and Oligo-Miocene Tineh formations.The latter contains more mature organofacies(up to 1.2%R_(o))and type Ⅱ/Ⅲ kerogen,thereby demonstrating a good capability to generate wet gases.The studied gas is wet and has thermogenic origin with signs of secondary microbial alteration,whereas the condensate contains a mixture of marine and terrestrial input.Molecular bio-markers of the condensate,isotopic and molecular composition of the gas reveals a generation of condensate prior to gas expulsion from the source.The Wakar sandstones have a heterogeneous pore system where three reservoir rock types(RRTⅠ,RRTⅡ and RRTⅢ).RRTI rocks present the bulk compo-sition of the Wakar pay zones.Spatial distribution of RRTⅠ facies likely control the accumulation of the sub-salt hydrocarbons.Our results provide a new evidence on an active petroleum system in the sub-salt Paleogene successions in the offshore Nile Delta where concomitant generation of gas/condensate blend has been outlined.展开更多
Leucogranite,pegmatite,and aplite from selected areas in the Wadi El Gemal area in the southern Eastern Desert of Egypt were investigated geochemically for their petrogenesis.These rocks represent a significant episod...Leucogranite,pegmatite,and aplite from selected areas in the Wadi El Gemal area in the southern Eastern Desert of Egypt were investigated geochemically for their petrogenesis.These rocks represent a significant episode of felsic magmatism during the late stage of the Pan-African orogeny in the evolution of the Arabian–Nubian Shield(ANS)during the Late Neoproterozoic.On a petrographic basis,the leucogranite is sometimes garnetiferous and can be distinguished into monzogranite,syenogranite,and alkali feldspar granite.The analyses of muscovite,biotite,garnet,and apatite reveal the magmatic nature of the studied leucogranite.The investigated leucogranite,pegmatite,and aplite are alkali-calcic,calc-alkaline,and peraluminous.The peraluminous nature of these rocks is evidenced by using the chemical analyses of biotite.These studied rocks show a slight enrichment in light rare-earth elements(LREEs)and large-ion lithophile elements(LILE,especially Rb and Th),with an insignificant depletion of heavy rareearth elements(HREEs).On a geochemical basis,the leucogranite,pegmatite,and aplite in the study area crystallized from multiple-sourced melts that include mafic,metagraywake,and pelitic.They were derived from melts generated at crystallization temperatures around 568-900℃ for leucogranite,553-781℃ for pegmatite,and 639-779℃ for aplite based on the Zr saturation geothermometers,and at a pressure around 0.39-0.48 GPa,i.e.shallow depth intrusions.The studied felsic rocks have strong negative Eu anomalies,which are very consistent with an upper crust composition,indicating fractionation of feldspar cumulates.Also,they show a moderate La/Sm ratio indicating combined magmatic processes represented by partial melting and fractional crystallization.Integration of whole-rock chemical composition and mineral microanalysis suggests that felsic magmatism in the west Wadi El Gemal area produced voluminous masses of syn-to post-collisional granite,pegmatite,and aplite.An evolutionary three-stage model is presented to understand late magmatism in the ANS in terms of a geodynamic model.Such a model discusses the propagation of felsic magmatism in the ANS during syn-collisional to post-collisional stages.展开更多
The Barud gneissic dome complex is situated along the ENE-trending dextral shear zone of the Qena-Safaga Line that serves as a significant tectonic boundary between the basement terrains of the Northern and Central Ea...The Barud gneissic dome complex is situated along the ENE-trending dextral shear zone of the Qena-Safaga Line that serves as a significant tectonic boundary between the basement terrains of the Northern and Central Eastern Desert.These terrains exhibit distinct differences in crustal composition and deformation style.The Northern Eastern Desert and its extension into Sinai are predominantly composed of gneissic granites that are intruded by large batholiths of calc-alkaline and alkaline granites.Conversely,the Central and Southern Eastern Desert are commonly blanketed by a carapace of ophiolite-bearing volcano-sedimentary rocks of the Pan-African cover nappes.These northern terrains,just north of the Barud dome complex,the crust underwent significant NW-SE regional crustal extension across the Qena-Safaga Line,which sharply delineates the northern limit of the transpressional deformations linked to the Najd fault system in the Central and Southern Eastern Desert.Through comprehensive geological mapping and the integration of various geophysical,geochemical and geochronological data,this paper offers explanations for the contrasting geological features of the basement terrains on both sides of the Qena-Safaga Line and its analogous Fatira Shear Zone that plays a significant role in tectonic modeling of the Barud dome complex region.The Barud gneissic protolith experienced crustal shortening approximately 697 million years ago in the NW-SE direction,initiating dextral motion along the Fatira Shear Zone.Large batholiths of granodiorite/tonalite complex intruded the Barud gneissic dome protolith around 630 million years ago along the Qena-Safaga Line,at relatively shallow crustal depths,following the same orientation as the earlier shortening direction.Ongoing magmatic activity along the Qena-Safaga Line indicates intense magmatic underplating,resulting in significant intrusions of granodioritic melts into the early rifted crust of the Northern Eastern Desert and Sinai terrains.The crust of these northern terrains likely underwent isostatic compensation through uplifting and subsequent erosion.The disappearance of ophiolite-bearing belts and the presence of Paleo-to Mesoproterozoic continental-derived cobbles and ignimbrites in Sinai metasedimentary belts and Northern Eastern Desert molasse basins suggest that the northern terrains,located north of the Qena-Safaga Line,originated as a cohesive,thin continental crust that rifted off the eastern passive margin of the Sahara Metacraton during the early Neoproterozoic rifting of the Rodinia supercontinent.展开更多
Arc-continent collision zones are critical areas where uplift,accretion,and erosion processes significantly influence the growth,elimination,or recycling of the continental crust.The Zagros–Makran Transition Zone,loc...Arc-continent collision zones are critical areas where uplift,accretion,and erosion processes significantly influence the growth,elimination,or recycling of the continental crust.The Zagros–Makran Transition Zone,located along the Minab-Zendan Fault,represents a convergence boundary between the Zagros continental domain and the Makran accretionary prism in southern Iran from the Cretaceous onwards.Several tectonic slices,including Neotethys ophiolitic remnants and the Ganj and Bajgan-Durkan complexes,have accreted along the southern margin of the Eurasian Plate during subduction in the western Makran wedge.To clarify the growth steps of the Makran Prism and the internal deformation associated with arc-continent collision,we used a provenance study of sandstones from the western Makran accretionary prism involving petrography of the main detrital components and U–Pb dating,Hf isotopic values,and trace elements of detrital zircon grains.Our findings reveal a progressive scenario in which oceanic arc-related rocks of the∼99 Ma Ganj Complex with Hf values ranging from+10 to+16 were uplifted during the Early to Late Eocene.The Eocene fore-arc sediments were sourced from the∼49–47 Ma Urumieh-Dokhtar Magmatic Arc with Hf values between−5 and+12,as well as from the Ganj Complex.The Jurassic–Cretaceous Bajgan-Durkan Complex was uplifted due to the Late Eocene to Oligocene collision of various terranes along the southern margin of the Eurasian Plate.This led to a major sediment influx into the Makran trench with a detrital signal in the range∼175–160 Ma with Hf isotopic values from−3 to+4 and alongside the Urumieh-Dokhtar Magmatic Arc with detrital ages ranging∼46–37 Ma and ca.80 Ma.Notably,metamorphic lithic grains began to appear in the sediments in the Late Eocene.The initial arrival of sediments from the Arabian margin to the arc-continent suture zone along the Minab-Zendan Fault indicates the onset of initial collision.During the Late Oligocene–Early Miocene,detrital zircon ages in the range of∼610–520 Ma,sourced from the Arabian basement,were deposited in the trench basin together with components from the Eocene Urumieh-Dokhtar Magmatic Arc and Cretaceous ophiolitic clasts of∼93 Ma with Hf isotopic values of+12 to+16.Following the development and uplift of the orogen from the Middle Miocene onward,detrital zircon grains from the Cretaceous–Miocene Urumieh-Dokhtar Magmatic Arc,Jurassic–Cretaceous Bajgan-Durkan Complex,and Cretaceous ophiolites are present in both the Makran and Zagros sedimentary domains.展开更多
Hemipelagic to pelagic(H/P)marls,representing pelitic deposits,accumulated within the foredeep sub-basin of the Dinaric Foreland Basin(northern Neotethyan margin,present-day Croatia)during the Middle to Late Eocene.Sy...Hemipelagic to pelagic(H/P)marls,representing pelitic deposits,accumulated within the foredeep sub-basin of the Dinaric Foreland Basin(northern Neotethyan margin,present-day Croatia)during the Middle to Late Eocene.Syn-sedimentary tectonic movements,paleogeographic position and exchanges of short-lived hyperthermal episodes affected the sedimentation and related mineral and geochemical record of these deposits.Mineral(clay)assemblages bear signature of prevailing physical weathering with significant illite and chlorite content,but climatic seasonality is suggested by smectite-interlayered phases and sporadical increase of kaolinite content.Illite crystallinity varies significantly,and the lowest crystallinity is recorded by the Lutetian samples.Illite chemistry index is always bellow 0.5,being characteristic for Fe-Mg-rich illite.The geochemical records are the most prominent(CIA up to 76,CIW up to 91)for the Istrian Lutetian(42.3-40.5 Ma),but also for Priabonian(35.8-34.3 Ma)samples of Hvar Island.The ICV values(the lowest 1.40 and the highest 10.85)of all studied samples fall above PAAS(ICV=0.85)and point to their chemical immaturity.The Ga/Rb ratios are lower than 0.2 and K_(2)O/Al_(2)O_(3) ratios are also low(0.16-0.22),implying transition between cold and dry,and warm and humid climate,obviously trending among several warming episodes.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 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
The Bikaner-Nagaur and Barmer Basins(Rajasthan)are the most important petroliferous sedimentary basins in India.For over a decade,the exploration and extraction of hydrocarbons in these basins.Paleocene-Eocene age roc...The Bikaner-Nagaur and Barmer Basins(Rajasthan)are the most important petroliferous sedimentary basins in India.For over a decade,the exploration and extraction of hydrocarbons in these basins.Paleocene-Eocene age rocks bear organic-rich sediments in these basins,including lignite and carbonaceous shale deposits.The present research investigates the source rock properties,petroleum potential and thermal maturity of the carbonaceous shale partings from the lignite mines of Gurha(Bikaner-Nagaur Basin)and Kapurdi(Barmer Basin)using petrographical and geochemical tools.The carbonaceous shales have high organic matter(OM),with considerable total organic carbon(TOC)contents ranging from 13%to 39%.Furthermore,they contain hydrogen-rich kerogen,including types II and II/III,as evidenced by the Rock-Eval and elemental analysis results.The existence of these kerogen types indicates the abundance of reactive(vitrinite and liptinite)macerals.However,the carbonaceous shales from the Bikaner–Nagaur Basin have oil generation potentials,with a high hydrogen index(up to 516 mg HC/g TOC)and a H/C ratio(up to 1.5)along with a significant presence of oil-prone liptinitic macerals.Apart from the geochemical and petrological results,the studied shales have low huminite reflectance(0.31%–0.48%),maximum temperature(S_(2) peak;Tmax)between 419℃ and 429℃,and low production index values(PI:0.01–0.03).These results indicate that these carbonaceous shales contain immature OM,and thereby,they cannot yet release commercial amount of oil.This immaturity level in the studied outcrop section is due to the shallow burial depth.Geochemical proxies further indicate the presence of both oil and gas-prone source rocks.展开更多
The Arabian-Nubian Shield(ANS)serves as a key geological archive,preserving the tectono-thermal evolution associated with the Rodinia breakup(∼900–800 Ma)and Gondwana formation(∼800–620 Ma).The Katherina Ring Comp...The Arabian-Nubian Shield(ANS)serves as a key geological archive,preserving the tectono-thermal evolution associated with the Rodinia breakup(∼900–800 Ma)and Gondwana formation(∼800–620 Ma).The Katherina Ring Complex(KRC),located in the Sinai Peninsula,Egypt(northern ANS),exemplifies continental growth through multistage magmatism and orogenesis,spanning the Tonian to Ediacaran periods(∼900–530 Ma).Despite its importance,debates persist regarding the nature,age,crustal characteristics,and magma source evolution of its constituent units.Situated in the northwestern part of the KRC,the Wadi Rofaiyed Cu deposit offers an exceptional natural laboratory for investigating continental crust formation during this interval,owing to its superb exposure and preservation.This study integrates detailed fieldwork,petrographic analyses,whole-rock geochemistry,Sr-Nd isotopes,and in situ zircon U-Pb-Lu-Hf isotopic data.It aims to(i)establish a robust chronological framework for the unmetamorphosed plutonic rocks of the KRC,(ii)advance the understanding of associated geodynamic processes,and(iii)elucidate the episodic magmatism events.The findings show that Wadi Rofaiyed juvenile crust developed in four main phases:(i)a subduction-accretionary phase(∼755 Ma)characterized by intense calc-alkaline magmatism,originating from the partial melting of mafic lower crust;(ii)a syn-collisional phase(∼630 Ma)occurred during the collision between the Saharan metacraton and the younger ANS crust,producing I-type granitoids formed through magma mixing and crustal anatexis;(iii)a post-collisional phase characterized by intermediate I-type(∼595 Ma)to felsic A-type alkaline magma(∼594 Ma),originated from the partial melting of the overthickened lower crust corresponding to lithospheric delamination;and(iv)an anorogenic phase(∼530 Ma)related to the final amalgamation of Greater Gondwana.Isotopic analyses across all four magmatic phases reveal low initial^(87)Sr/^(86)Sr(0.702648–0.703311)and positiveε_(Hf)(t)(+2.84 to+7.78)andε_(Nd)(t)(+2.61 to+5.21)values,consistent with lower crustal sources with depleted mantle-like signatures.The model ages(T_(DM2))for these magmatic rocks derived from zircon Hf(1.2–1.5 Ga)and whole-rock Nd isotopes(0.96–1.17 Ga)support a predominantly juvenile crustal origin.These findings underscore the multistage tectono-magmatic evolution of the northern ANS,advancing our understanding of obduction-accretion dynamics and crustal development during the Neoproterozoic.展开更多
The Baibokoum syenitic pluton(BSP),located in southern Chad,to the NE of the Adamawa-Yadédomain,is one of the few strongly potassic magmatic bodies in the southern part of the Central African Fold Belt(CAFB)in Ch...The Baibokoum syenitic pluton(BSP),located in southern Chad,to the NE of the Adamawa-Yadédomain,is one of the few strongly potassic magmatic bodies in the southern part of the Central African Fold Belt(CAFB)in Chad.It has been previously studied petrologically,but its petrogenesis has remained poorly known.Petrographic and whole-rock geochemical data presented in this article highlight their magma genesis and geodynamic evolution.The BSP consists of medium-to coarse-grained syenites associated with minor microdiorites,which occur as syn-plutonic dikes and mafic microgranular enclaves(MME)coarse-and medium-grained syenites outcrop respectively to the core and the border of the BSP.The syenite displays high-K and alkaline to trans-alkaline affinity.Petrographic and geochemical data suggest that medium-to coarse-grained syenites are from single magma source that evolved and differentiated by fractional crystallization in a magma reservoir.REE profiles show enriched LREEs(La_(N)/Yb_(N)=6.19-45.55)while HREEs show an almost flat profile(Dy_(N)/Yb_(N)=1.0-2.23),and the La/Sm and Sm/Yb ratios have led to propose that the aforementioned rocks derived from the partial melting of a garnet-spinel-lherzolite mantle source.Negative Nb and Ta anomalies indicate that this mantle source was modified by the addition of subduction-related material.Th/Yb ratios associated with high Ba/La ratios indicate that enrichment of the source could be related to slab-derived fluids.The parental magma of the BSP was generated by partial melting of the metasomatized lithospheric mantle that was modified into arc-magmatism material in a subduction setting.Its emplacement took place in two successive stages:a static stage of fractional crystallization and crystal settling in a deep magma source and a dynamic stage in a shear deformation setting during which stratified magma rises towards the upper crust,with evolved syenite magma being emplaced first and diorite later.The emplacement of the BSP was probably controlled by the evolution of the Tcholliré-Banyo Fault and M'BéréShear Zone during the Pan-African orogeny.展开更多
Hejiangkou W-Sn-polymetallic deposit is a newly found deposit in Xitian ore field,one of the important and large scale W-Sn-polymetallic ore fields in the middle segment of Nanling metallogenic zone.Re-Os isotope dati...Hejiangkou W-Sn-polymetallic deposit is a newly found deposit in Xitian ore field,one of the important and large scale W-Sn-polymetallic ore fields in the middle segment of Nanling metallogenic zone.Re-Os isotope dating was used on three molybdenite samples from Hejiangkou deposit to determine the ore forming period.The result is(224.9±2.6)Ma-(225±3.1)Ma and isochron age is(225.5±3.6)Ma.The field geological observations,geochronological data and optical petrography indicated that Hejiangkou deposit underwent multi-period of superimposed mineralization.It can be differentiated into three periods composed of six mineralization stages.The first period is the initial period for hydrothermal metasomatism and metal element enrichment during Indosinian Epoch.Further enrichment,strong brittle fracturing and hydrothermal metasomatism,remobilization and superimposition happened in the second period,during early Yanshanian.It is the major mineralization period of Hejiangkou deposit and can be subdivided into four mineralization stages,namely the skarn stage,oxide stage,high-temperature sulfide stage and low-temperature sulfide stage.And the third period is the mineralization period of a porphyry-skarn system related to the emplacement of the granite porphyry dyke.As minerogenic epoch of Hejiangkou deposit is similar with Hehuaping deposit,they show the possibility of Indosinian mineralization event in Nanling metallogenic zone.It can be an important perspective in any future mineral exploration in the same metallogenic zone.展开更多
The use of geomagnetic for geophysical and geological studies is a new method for receiving different information from new and old faults and lineaments. Accordingly, the present study is applied research and it use c...The use of geomagnetic for geophysical and geological studies is a new method for receiving different information from new and old faults and lineaments. Accordingly, the present study is applied research and it use combined the two methods, analytical signal and Euler’s combined method and invented a new combined method to estimate the depth, location and shape of the magnetic and gravity sources. As a case, this research selected Iran’s Zagros zone. This region due to the geological dynamics is considered by many geologists. In this regard, the 1:250,000 framework of Haji Abad was selected as a case study because of its convenient location for structural analysis. As a result, with airborne magnetic images survey, and applying filters in the vertical derivative and analytical signal, lineaments in depth of this region discovered and investigated.展开更多
The accumulation of sediment in river channels is a phenomenon that is not only influenced by the channel morphology, but also by the physical and geographical character- istics and the endogenous and exogenous proces...The accumulation of sediment in river channels is a phenomenon that is not only influenced by the channel morphology, but also by the physical and geographical character- istics and the endogenous and exogenous processes taking place in the catchment. This paper presents an analysis of the impact the changes in lithological conditions have on the morphological and morphometric parameters of the Udava River channel and their relation to the channel accumulation forms representative of the river＇s longitudinal profile as well as of its planform. Results document when accumulation forms occur and what is their spatial dis- tribution within the longitudinal and cross-sectional river profiles. More resistant structures created sections with a lower degree of sedimentation, while in depression segments the degree of sedimentation was higher. With the increase in longitudinal slope, the impact of channel width on the average channel bar size increased. Also a difference in the accumula- tion was observed between the left and right bank which could be possibly explained by the impact of Coriolis force.展开更多
Carpathian-Balkan Geological Association （CBGA）, according to its Statute, ＂is non-governmental, international, scientific, non-political and non-profit making union of geoscientists working in the Carpathian-Balka...Carpathian-Balkan Geological Association （CBGA）, according to its Statute, ＂is non-governmental, international, scientific, non-political and non-profit making union of geoscientists working in the Carpathian-Balkan realm＂ and surrounding areas. The membership of CBGA is collective and it is ＂open to geoscientists of all countries of the Carpathian-Balkan＂ and neighboring countries. Application of collective membership ＂should be submitted by competent scientific bodies＂.展开更多
There are many factors which affect the hydrological, geomorphologic and hydrogeological condition of the area. In order to better comprehend all processes, a Digital Elevation Model (DEM) was developed based on Geogr...There are many factors which affect the hydrological, geomorphologic and hydrogeological condition of the area. In order to better comprehend all processes, a Digital Elevation Model (DEM) was developed based on Geographical Information System. This latter appears as an essential tool to facilitate the decision support and can provide very important geological information. In fact, the use of the DEM is growing dramatically with the use of the GIS and the improvement of information extracted from elevation data such as mapping of floods, forest areas, erosion, and lineaments. The spatial distribution of topographic attributes can often be used as an indirect measure of the spatial variability of these processes and allows them to be mapped using relatively simple techniques. The main purpose of this study is to model the natural surface of the earth as the most accurate and the most precise. For this end we have tried in this work to develop various types of Digital Elevation Models DEM of the Foussana rift in Central Tunisia and to demonstrate the role of these models in geological, hydrogeological and hydrological study. The 3D model is also coupled in this study with piezometric and hydrochemistry study, so a new information’s plan was mapped by multiple GIS techniques like Spatial analysis and interpolation;in order 1) to comprehend the hydrodynamic of the aquifer, 2) to quantify surface and subsurface water resources and 3) to generate water management scenarios in the study area. To this end, several groundwater samples were collected and analyzed from wells and piezometers. Examining the corresponding physical and chemical parameters showed an increase in the concentrations of hydraulic conductivity in the center of the study area and it coincided with zones with high nutrient concentration. Recommendations are proposed in this zone.展开更多
The capital of Georgia</span><span style="font-family:Verdana;">—Tbilisi has a very convenient location and is a node of the transit corridor. Along with natural-geological conditions, its compl...The capital of Georgia</span><span style="font-family:Verdana;">—Tbilisi has a very convenient location and is a node of the transit corridor. Along with natural-geological conditions, its complexity is due to the rapid demographic growth of the city in a highly “sensitive” area of the geological environment and the pressure of high engineering and agricultural activities. In Tbilisi</span></span><span style="font-family:Verdana;">,</span><span style="font-family:Verdana;"> it is observed almost all type</span><span style="font-family:Verdana;">s</span><span style="font-family:""><span style="font-family:Verdana;"> of geological hazards, including landslide-gravitational, suffosion, debris/mudflows, river </span><span style="font-family:Verdana;">bank erosion and inundation </span></span><span style="font-family:Verdana;">were </span><span style="font-family:Verdana;">caused by groundwater. These hazard</span><span style="font-family:Verdana;">s</span><span style="font-family:Verdana;"> cause</span><span style="font-family:""><span style="font-family:Verdana;"> high damages to the residential houses and other infrastructure facilities. Most importantly and most tragically is that these kind of negative geological events are often accompanied by human casualties. The study discusses the geological processes developed in March 2021 in the corridor of the Vashlij</span><span style="font-family:Verdana;">vari-Lisi road (Machavariani Street). The information obtained from the study,</span><span style="font-family:Verdana;"> reflects the triggering factors of the geological hazards, also damages caused by them, and provides recommendations for short-term and long-term protective measures that should ensure the sustainable operation of the road and other infrastructure facilities.展开更多
In the event of natural disasters, Sierra Leone like any other country loses lives as well as properties and natural resources. Despite notable occurrences of small disasters in the country, only on August 14th sugarl...In the event of natural disasters, Sierra Leone like any other country loses lives as well as properties and natural resources. Despite notable occurrences of small disasters in the country, only on August 14th sugarloaf landslide and the resulting flash flood (twin disasters) which affected Regent and other communities in 2017 have captured both national and international attention due to their alarming impacts. To obtain a better knowledge on the nature of the disasters, this research considered the geological context of the landslide and focused on statistical analysis of the impacts of the twin disasters using Statistical Package for Social Sciences (SPSS). Geological field-based approach and self-administered questionnaires of both closed and open-ended questions, personal interviews and observations were adopted as research techniques. Descriptive statistics and qualitative analysis were used to analyze the data of the research. Relevant literature from books, journals, and newspapers was also consulted, including Radio, Television discussions and the internet. Slope destabilization that caused the Landslide was linked to the geology of sub-surface formation (highly weathered olivine gabbro), lineaments and the rate of weathering. Study showed remarkable economic, social and political impacts as a consequence of the twin disasters. Study also revealed that families assisted the most in both financial and non-financial ways to the victims, and renowned misappropriation of donated disaster funds. All variables tested using student t-distribution and chi-square test of independence accepted the hypothesis. Information obtained from this work could be fundamental for policy makers and development practitioners (Osuteye & Leck, 2017).展开更多
文摘Geological setting,facies characteristics,and geochemistry,including TGA(thermo-gravimetric analysis)of Paleogene deposits in east Beni Suef region(Egypt),were studied in the present work.Lithostratigraphically,the area consists of three rock units,arranged from oldest to youngest:Tarbul Member of Beni Suef Formation(MiddleLate Eocene),Maadi Formation(Late Eocene),and Gebel Ahmar Formation(Oligocene),this last formation registered for the first time in the east of Beni Suef area(Egypt).Seven microfacies types(F1-F7)were determined by the microscopic examination of the studied samples in low-to high-energy and shallow-subtidal marine conditions.The lithostratigraphic,petrological,and geochemical results revealed that the Eocene succession in the present area is composed mainly of carbonates as well as siliciclastics.The Oligocene Gebel Ahmar Formation consists mainly of silica and iron oxides.The enrichment of the rock units with iron oxides in the studied area,as well as the high proportions of trace elements such as Zr,Ba,V,and Sr,in particular in the Gebel Ahmar Formation,reflects the influence of the hydrothermal solutions during the Oligocene.TGA,which monitors weight changes during heating at a constant rate,was used to determine the thermal stability and volatile component content of the materials.The ferruginous sandstone of Gebel Ahmar Formation exhibits various decomposition phases when exposed to thermal inf luences,with TGA indicating an initial mass decrease starting at 61.8℃.In contrast,the ferruginous limestone of the Maadi Formation shows a single-phase mass decrease between 650 and 875℃.
基金the National Science Foundation of China (Grant No. NSFC: 92162213)the Geology Department Faculty of Science of Al-Azhar University (Assiut Branch)+2 种基金the China Scholarship CouncilChang'an UniversityIstanbul Technical University's Scientific Research Project (BAP Project ID: 45396, code: FHD-2024-45396)
文摘In the Fatira(Abu Zawal)mine area,located in the northern Eastern Desert of Egypt,fieldwork and mineralogical analysis,integrated with machine learning techniques applied to Landsat-8 OLI,ASTER,and Sentinel-2 multi-spectral imagery(MSI)data delineate gold-sulfide mineralization in altered rocks.Gold(Au)anomalies in hydrothermal breccias and quartz veins are associated with NE-oriented felsite dykes and silicified granitic rocks.Two main alteration types are identified:a pyrite-sericite-quartz and a sulfide-chlorite-carbonate assemblage,locally with dispersed free-milling Au specks.Dimensionality reduction techniques,including principal component analysis(PCA)and independent component analysis(ICA),enabled mapping of alteration types.Sentinel-2 PC125 composite images offered efficient lithological differentiation,while supervised classifications,i.e.,the support vector machine(SVM)of Landsat-8 yielded an accuracy of 88.55%and a Kappa value of 0.86.ASTER mineral indices contributed to map hydrothermal alteration mineral phases,including sericite,muscovite,kaolinite,and iron oxides.Results indicate that post-magmatic epigenetic hydrothermal activity significantly contributed to the Au-sulfide mineralization in the Fatira area,distinguishing it from the more prevalent orogenic gold deposits in the region.
基金financial support received through a grant from the Vice-President's Research Office at Bu-Ali Sina University,Iran(Grant Number 09.99)。
文摘Fractal geometry quantitatively analyzes the irregular distribution of geological features,highlighting the dynamic aspects of tectonics,seismic heterogeneity,and geological maturity.This study analyzed the active fault data along the Kuhbanan fault zone in southeastern Iran by applying the boxcounting method and observing the changes in Coulomb stress and tried to find the potential triggering parts.The entire region was divided into 16subzones with the box-counting method,and then the fractal dimension(D)in each zone was calculated.The analysis of the fractal dimension for active faults and earthquake epicenters along with the seismicity parameter(b)and their ratio in the Kuhbanan region indicates an imbalance between seismic fractals and faults.This finding suggests that the area may have the potential for future earthquakes or hidden faults.In conjunction with b-value and changes in Coulomb stress change,D-value analysis reveals intense tectonic activity and stress accumulation,particularly within the Ravar,Zarand,and Kianshahr sections.It may be considered a potential location for future earthquakes.The changes in Coulomb stress resulting from the 2005Dahuieh earthquake have also placed this region within the stress accumulation zone,potentially triggering the mentioned areas.This integrative approach,backed by historical earthquake data,highlights the impact of fault geometry and stress dynamics,offering an enhanced framework for earthquake forecasting and seismic risk mitigation applicable to other tectonically active areas within the Iranian plateau.
文摘Offshore Nile Delta in Egypt represents an enormous hydrocarbon province with recent projected gas and condensate discoveries of more than 50 trillion cubic feet“TCF”.Most of these occur in the post-salt hydrocarbon plays where biogenic gases are dominant.This study integrates organic geochemistry,seismic geomorphology and petrophysics in order to decipher the origin,and accumulation conditions of the wet gas/condensate blend in the Upper Miocene sub-salt Wakar Formation sandstones in Port Fouad Marine“PFM”Field,offshore Nile Delta.Hydrocarbon pay zones are scattered thin(<10 m)sandstones deposited in as turbiditic channel/levee complex facies.Spatial distribution of vertical gas chimneys(~2 km wide)rooting-down to the Messinian Rosetta salt is associated with the lateral pinching-out of the turbiditic sandstones.Organically-rich(total organic carbon“TOC”>1 w.t.%,hydrogen index“HI”>200 mgHC/gTOC)and mature(Tmax>430℃,vitrinite reflectance“VR”>0.6%R_(o)),source rocks are restricted to Upper Miocene Wakar and Oligo-Miocene Tineh formations.The latter contains more mature organofacies(up to 1.2%R_(o))and type Ⅱ/Ⅲ kerogen,thereby demonstrating a good capability to generate wet gases.The studied gas is wet and has thermogenic origin with signs of secondary microbial alteration,whereas the condensate contains a mixture of marine and terrestrial input.Molecular bio-markers of the condensate,isotopic and molecular composition of the gas reveals a generation of condensate prior to gas expulsion from the source.The Wakar sandstones have a heterogeneous pore system where three reservoir rock types(RRTⅠ,RRTⅡ and RRTⅢ).RRTI rocks present the bulk compo-sition of the Wakar pay zones.Spatial distribution of RRTⅠ facies likely control the accumulation of the sub-salt hydrocarbons.Our results provide a new evidence on an active petroleum system in the sub-salt Paleogene successions in the offshore Nile Delta where concomitant generation of gas/condensate blend has been outlined.
基金finational supported by the Foundation of Science,Technology and Innovation Funding Authority(STDF)(Award Number:47106Recipient:Mokhles K K.Azer)。
文摘Leucogranite,pegmatite,and aplite from selected areas in the Wadi El Gemal area in the southern Eastern Desert of Egypt were investigated geochemically for their petrogenesis.These rocks represent a significant episode of felsic magmatism during the late stage of the Pan-African orogeny in the evolution of the Arabian–Nubian Shield(ANS)during the Late Neoproterozoic.On a petrographic basis,the leucogranite is sometimes garnetiferous and can be distinguished into monzogranite,syenogranite,and alkali feldspar granite.The analyses of muscovite,biotite,garnet,and apatite reveal the magmatic nature of the studied leucogranite.The investigated leucogranite,pegmatite,and aplite are alkali-calcic,calc-alkaline,and peraluminous.The peraluminous nature of these rocks is evidenced by using the chemical analyses of biotite.These studied rocks show a slight enrichment in light rare-earth elements(LREEs)and large-ion lithophile elements(LILE,especially Rb and Th),with an insignificant depletion of heavy rareearth elements(HREEs).On a geochemical basis,the leucogranite,pegmatite,and aplite in the study area crystallized from multiple-sourced melts that include mafic,metagraywake,and pelitic.They were derived from melts generated at crystallization temperatures around 568-900℃ for leucogranite,553-781℃ for pegmatite,and 639-779℃ for aplite based on the Zr saturation geothermometers,and at a pressure around 0.39-0.48 GPa,i.e.shallow depth intrusions.The studied felsic rocks have strong negative Eu anomalies,which are very consistent with an upper crust composition,indicating fractionation of feldspar cumulates.Also,they show a moderate La/Sm ratio indicating combined magmatic processes represented by partial melting and fractional crystallization.Integration of whole-rock chemical composition and mineral microanalysis suggests that felsic magmatism in the west Wadi El Gemal area produced voluminous masses of syn-to post-collisional granite,pegmatite,and aplite.An evolutionary three-stage model is presented to understand late magmatism in the ANS in terms of a geodynamic model.Such a model discusses the propagation of felsic magmatism in the ANS during syn-collisional to post-collisional stages.
基金The Egyptian ministry for higher education and the Stipendium Hungaricum scholarship are thanked for funding Mohamed Badawi under the joint executive program between Hungary and Egypt.
文摘The Barud gneissic dome complex is situated along the ENE-trending dextral shear zone of the Qena-Safaga Line that serves as a significant tectonic boundary between the basement terrains of the Northern and Central Eastern Desert.These terrains exhibit distinct differences in crustal composition and deformation style.The Northern Eastern Desert and its extension into Sinai are predominantly composed of gneissic granites that are intruded by large batholiths of calc-alkaline and alkaline granites.Conversely,the Central and Southern Eastern Desert are commonly blanketed by a carapace of ophiolite-bearing volcano-sedimentary rocks of the Pan-African cover nappes.These northern terrains,just north of the Barud dome complex,the crust underwent significant NW-SE regional crustal extension across the Qena-Safaga Line,which sharply delineates the northern limit of the transpressional deformations linked to the Najd fault system in the Central and Southern Eastern Desert.Through comprehensive geological mapping and the integration of various geophysical,geochemical and geochronological data,this paper offers explanations for the contrasting geological features of the basement terrains on both sides of the Qena-Safaga Line and its analogous Fatira Shear Zone that plays a significant role in tectonic modeling of the Barud dome complex region.The Barud gneissic protolith experienced crustal shortening approximately 697 million years ago in the NW-SE direction,initiating dextral motion along the Fatira Shear Zone.Large batholiths of granodiorite/tonalite complex intruded the Barud gneissic dome protolith around 630 million years ago along the Qena-Safaga Line,at relatively shallow crustal depths,following the same orientation as the earlier shortening direction.Ongoing magmatic activity along the Qena-Safaga Line indicates intense magmatic underplating,resulting in significant intrusions of granodioritic melts into the early rifted crust of the Northern Eastern Desert and Sinai terrains.The crust of these northern terrains likely underwent isostatic compensation through uplifting and subsequent erosion.The disappearance of ophiolite-bearing belts and the presence of Paleo-to Mesoproterozoic continental-derived cobbles and ignimbrites in Sinai metasedimentary belts and Northern Eastern Desert molasse basins suggest that the northern terrains,located north of the Qena-Safaga Line,originated as a cohesive,thin continental crust that rifted off the eastern passive margin of the Sahara Metacraton during the early Neoproterozoic rifting of the Rodinia supercontinent.
基金This research was supported by the NSFC grant(No.92255303)The first author is grateful for support from the IGGCAS postdoctoral program(2016IFPR01)under the guidance of Prof.Bo Wan.
文摘Arc-continent collision zones are critical areas where uplift,accretion,and erosion processes significantly influence the growth,elimination,or recycling of the continental crust.The Zagros–Makran Transition Zone,located along the Minab-Zendan Fault,represents a convergence boundary between the Zagros continental domain and the Makran accretionary prism in southern Iran from the Cretaceous onwards.Several tectonic slices,including Neotethys ophiolitic remnants and the Ganj and Bajgan-Durkan complexes,have accreted along the southern margin of the Eurasian Plate during subduction in the western Makran wedge.To clarify the growth steps of the Makran Prism and the internal deformation associated with arc-continent collision,we used a provenance study of sandstones from the western Makran accretionary prism involving petrography of the main detrital components and U–Pb dating,Hf isotopic values,and trace elements of detrital zircon grains.Our findings reveal a progressive scenario in which oceanic arc-related rocks of the∼99 Ma Ganj Complex with Hf values ranging from+10 to+16 were uplifted during the Early to Late Eocene.The Eocene fore-arc sediments were sourced from the∼49–47 Ma Urumieh-Dokhtar Magmatic Arc with Hf values between−5 and+12,as well as from the Ganj Complex.The Jurassic–Cretaceous Bajgan-Durkan Complex was uplifted due to the Late Eocene to Oligocene collision of various terranes along the southern margin of the Eurasian Plate.This led to a major sediment influx into the Makran trench with a detrital signal in the range∼175–160 Ma with Hf isotopic values from−3 to+4 and alongside the Urumieh-Dokhtar Magmatic Arc with detrital ages ranging∼46–37 Ma and ca.80 Ma.Notably,metamorphic lithic grains began to appear in the sediments in the Late Eocene.The initial arrival of sediments from the Arabian margin to the arc-continent suture zone along the Minab-Zendan Fault indicates the onset of initial collision.During the Late Oligocene–Early Miocene,detrital zircon ages in the range of∼610–520 Ma,sourced from the Arabian basement,were deposited in the trench basin together with components from the Eocene Urumieh-Dokhtar Magmatic Arc and Cretaceous ophiolitic clasts of∼93 Ma with Hf isotopic values of+12 to+16.Following the development and uplift of the orogen from the Middle Miocene onward,detrital zircon grains from the Cretaceous–Miocene Urumieh-Dokhtar Magmatic Arc,Jurassic–Cretaceous Bajgan-Durkan Complex,and Cretaceous ophiolites are present in both the Makran and Zagros sedimentary domains.
基金supported by Croatian Science Foundation Research Project Dinaridic Foreland Basin between Two Eocene Thermal Optima:A Possible Scenario for the Northern Adriatic BREEMECO(No.2019-04-5775)。
文摘Hemipelagic to pelagic(H/P)marls,representing pelitic deposits,accumulated within the foredeep sub-basin of the Dinaric Foreland Basin(northern Neotethyan margin,present-day Croatia)during the Middle to Late Eocene.Syn-sedimentary tectonic movements,paleogeographic position and exchanges of short-lived hyperthermal episodes affected the sedimentation and related mineral and geochemical record of these deposits.Mineral(clay)assemblages bear signature of prevailing physical weathering with significant illite and chlorite content,but climatic seasonality is suggested by smectite-interlayered phases and sporadical increase of kaolinite content.Illite crystallinity varies significantly,and the lowest crystallinity is recorded by the Lutetian samples.Illite chemistry index is always bellow 0.5,being characteristic for Fe-Mg-rich illite.The geochemical records are the most prominent(CIA up to 76,CIW up to 91)for the Istrian Lutetian(42.3-40.5 Ma),but also for Priabonian(35.8-34.3 Ma)samples of Hvar Island.The ICV values(the lowest 1.40 and the highest 10.85)of all studied samples fall above PAAS(ICV=0.85)and point to their chemical immaturity.The Ga/Rb ratios are lower than 0.2 and K_(2)O/Al_(2)O_(3) ratios are also low(0.16-0.22),implying transition between cold and dry,and warm and humid climate,obviously trending among several warming episodes.
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.
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.
基金The University of Malaya's postdoctoral fellowship program has been acknowledged by the first author and is associated with grant number IF064-2019the Department of Science and Technology (Project No. SB/S4/ES-681/2013), Government of India, for their supportthe Researchers Supporting Project number (RSPD2024R546) at King Saud University in Riyadh, Saudi Arabia
文摘The Bikaner-Nagaur and Barmer Basins(Rajasthan)are the most important petroliferous sedimentary basins in India.For over a decade,the exploration and extraction of hydrocarbons in these basins.Paleocene-Eocene age rocks bear organic-rich sediments in these basins,including lignite and carbonaceous shale deposits.The present research investigates the source rock properties,petroleum potential and thermal maturity of the carbonaceous shale partings from the lignite mines of Gurha(Bikaner-Nagaur Basin)and Kapurdi(Barmer Basin)using petrographical and geochemical tools.The carbonaceous shales have high organic matter(OM),with considerable total organic carbon(TOC)contents ranging from 13%to 39%.Furthermore,they contain hydrogen-rich kerogen,including types II and II/III,as evidenced by the Rock-Eval and elemental analysis results.The existence of these kerogen types indicates the abundance of reactive(vitrinite and liptinite)macerals.However,the carbonaceous shales from the Bikaner–Nagaur Basin have oil generation potentials,with a high hydrogen index(up to 516 mg HC/g TOC)and a H/C ratio(up to 1.5)along with a significant presence of oil-prone liptinitic macerals.Apart from the geochemical and petrological results,the studied shales have low huminite reflectance(0.31%–0.48%),maximum temperature(S_(2) peak;Tmax)between 419℃ and 429℃,and low production index values(PI:0.01–0.03).These results indicate that these carbonaceous shales contain immature OM,and thereby,they cannot yet release commercial amount of oil.This immaturity level in the studied outcrop section is due to the shallow burial depth.Geochemical proxies further indicate the presence of both oil and gas-prone source rocks.
基金supported by the National Natural Science Foundation of China(No.92162103)the Natural Science Foundation of Hunan Province(No.2022JJ30699,No.2023JJ10064)the Science and Technology Innovation Program of Hunan Province(No.2021RC4055,No.2022RC1182).
文摘The Arabian-Nubian Shield(ANS)serves as a key geological archive,preserving the tectono-thermal evolution associated with the Rodinia breakup(∼900–800 Ma)and Gondwana formation(∼800–620 Ma).The Katherina Ring Complex(KRC),located in the Sinai Peninsula,Egypt(northern ANS),exemplifies continental growth through multistage magmatism and orogenesis,spanning the Tonian to Ediacaran periods(∼900–530 Ma).Despite its importance,debates persist regarding the nature,age,crustal characteristics,and magma source evolution of its constituent units.Situated in the northwestern part of the KRC,the Wadi Rofaiyed Cu deposit offers an exceptional natural laboratory for investigating continental crust formation during this interval,owing to its superb exposure and preservation.This study integrates detailed fieldwork,petrographic analyses,whole-rock geochemistry,Sr-Nd isotopes,and in situ zircon U-Pb-Lu-Hf isotopic data.It aims to(i)establish a robust chronological framework for the unmetamorphosed plutonic rocks of the KRC,(ii)advance the understanding of associated geodynamic processes,and(iii)elucidate the episodic magmatism events.The findings show that Wadi Rofaiyed juvenile crust developed in four main phases:(i)a subduction-accretionary phase(∼755 Ma)characterized by intense calc-alkaline magmatism,originating from the partial melting of mafic lower crust;(ii)a syn-collisional phase(∼630 Ma)occurred during the collision between the Saharan metacraton and the younger ANS crust,producing I-type granitoids formed through magma mixing and crustal anatexis;(iii)a post-collisional phase characterized by intermediate I-type(∼595 Ma)to felsic A-type alkaline magma(∼594 Ma),originated from the partial melting of the overthickened lower crust corresponding to lithospheric delamination;and(iv)an anorogenic phase(∼530 Ma)related to the final amalgamation of Greater Gondwana.Isotopic analyses across all four magmatic phases reveal low initial^(87)Sr/^(86)Sr(0.702648–0.703311)and positiveε_(Hf)(t)(+2.84 to+7.78)andε_(Nd)(t)(+2.61 to+5.21)values,consistent with lower crustal sources with depleted mantle-like signatures.The model ages(T_(DM2))for these magmatic rocks derived from zircon Hf(1.2–1.5 Ga)and whole-rock Nd isotopes(0.96–1.17 Ga)support a predominantly juvenile crustal origin.These findings underscore the multistage tectono-magmatic evolution of the northern ANS,advancing our understanding of obduction-accretion dynamics and crustal development during the Neoproterozoic.
文摘The Baibokoum syenitic pluton(BSP),located in southern Chad,to the NE of the Adamawa-Yadédomain,is one of the few strongly potassic magmatic bodies in the southern part of the Central African Fold Belt(CAFB)in Chad.It has been previously studied petrologically,but its petrogenesis has remained poorly known.Petrographic and whole-rock geochemical data presented in this article highlight their magma genesis and geodynamic evolution.The BSP consists of medium-to coarse-grained syenites associated with minor microdiorites,which occur as syn-plutonic dikes and mafic microgranular enclaves(MME)coarse-and medium-grained syenites outcrop respectively to the core and the border of the BSP.The syenite displays high-K and alkaline to trans-alkaline affinity.Petrographic and geochemical data suggest that medium-to coarse-grained syenites are from single magma source that evolved and differentiated by fractional crystallization in a magma reservoir.REE profiles show enriched LREEs(La_(N)/Yb_(N)=6.19-45.55)while HREEs show an almost flat profile(Dy_(N)/Yb_(N)=1.0-2.23),and the La/Sm and Sm/Yb ratios have led to propose that the aforementioned rocks derived from the partial melting of a garnet-spinel-lherzolite mantle source.Negative Nb and Ta anomalies indicate that this mantle source was modified by the addition of subduction-related material.Th/Yb ratios associated with high Ba/La ratios indicate that enrichment of the source could be related to slab-derived fluids.The parental magma of the BSP was generated by partial melting of the metasomatized lithospheric mantle that was modified into arc-magmatism material in a subduction setting.Its emplacement took place in two successive stages:a static stage of fractional crystallization and crystal settling in a deep magma source and a dynamic stage in a shear deformation setting during which stratified magma rises towards the upper crust,with evolved syenite magma being emplaced first and diorite later.The emplacement of the BSP was probably controlled by the evolution of the Tcholliré-Banyo Fault and M'BéréShear Zone during the Pan-African orogeny.
基金Project(41403035)supported by the National Natural Science Foundation of ChinaProject(13JJ4041)supported by Hunan Provincial National Natural Science Foundation,China
文摘Hejiangkou W-Sn-polymetallic deposit is a newly found deposit in Xitian ore field,one of the important and large scale W-Sn-polymetallic ore fields in the middle segment of Nanling metallogenic zone.Re-Os isotope dating was used on three molybdenite samples from Hejiangkou deposit to determine the ore forming period.The result is(224.9±2.6)Ma-(225±3.1)Ma and isochron age is(225.5±3.6)Ma.The field geological observations,geochronological data and optical petrography indicated that Hejiangkou deposit underwent multi-period of superimposed mineralization.It can be differentiated into three periods composed of six mineralization stages.The first period is the initial period for hydrothermal metasomatism and metal element enrichment during Indosinian Epoch.Further enrichment,strong brittle fracturing and hydrothermal metasomatism,remobilization and superimposition happened in the second period,during early Yanshanian.It is the major mineralization period of Hejiangkou deposit and can be subdivided into four mineralization stages,namely the skarn stage,oxide stage,high-temperature sulfide stage and low-temperature sulfide stage.And the third period is the mineralization period of a porphyry-skarn system related to the emplacement of the granite porphyry dyke.As minerogenic epoch of Hejiangkou deposit is similar with Hehuaping deposit,they show the possibility of Indosinian mineralization event in Nanling metallogenic zone.It can be an important perspective in any future mineral exploration in the same metallogenic zone.
文摘The use of geomagnetic for geophysical and geological studies is a new method for receiving different information from new and old faults and lineaments. Accordingly, the present study is applied research and it use combined the two methods, analytical signal and Euler’s combined method and invented a new combined method to estimate the depth, location and shape of the magnetic and gravity sources. As a case, this research selected Iran’s Zagros zone. This region due to the geological dynamics is considered by many geologists. In this regard, the 1:250,000 framework of Haji Abad was selected as a case study because of its convenient location for structural analysis. As a result, with airborne magnetic images survey, and applying filters in the vertical derivative and analytical signal, lineaments in depth of this region discovered and investigated.
文摘The accumulation of sediment in river channels is a phenomenon that is not only influenced by the channel morphology, but also by the physical and geographical character- istics and the endogenous and exogenous processes taking place in the catchment. This paper presents an analysis of the impact the changes in lithological conditions have on the morphological and morphometric parameters of the Udava River channel and their relation to the channel accumulation forms representative of the river＇s longitudinal profile as well as of its planform. Results document when accumulation forms occur and what is their spatial dis- tribution within the longitudinal and cross-sectional river profiles. More resistant structures created sections with a lower degree of sedimentation, while in depression segments the degree of sedimentation was higher. With the increase in longitudinal slope, the impact of channel width on the average channel bar size increased. Also a difference in the accumula- tion was observed between the left and right bank which could be possibly explained by the impact of Coriolis force.
文摘Carpathian-Balkan Geological Association （CBGA）, according to its Statute, ＂is non-governmental, international, scientific, non-political and non-profit making union of geoscientists working in the Carpathian-Balkan realm＂ and surrounding areas. The membership of CBGA is collective and it is ＂open to geoscientists of all countries of the Carpathian-Balkan＂ and neighboring countries. Application of collective membership ＂should be submitted by competent scientific bodies＂.
文摘There are many factors which affect the hydrological, geomorphologic and hydrogeological condition of the area. In order to better comprehend all processes, a Digital Elevation Model (DEM) was developed based on Geographical Information System. This latter appears as an essential tool to facilitate the decision support and can provide very important geological information. In fact, the use of the DEM is growing dramatically with the use of the GIS and the improvement of information extracted from elevation data such as mapping of floods, forest areas, erosion, and lineaments. The spatial distribution of topographic attributes can often be used as an indirect measure of the spatial variability of these processes and allows them to be mapped using relatively simple techniques. The main purpose of this study is to model the natural surface of the earth as the most accurate and the most precise. For this end we have tried in this work to develop various types of Digital Elevation Models DEM of the Foussana rift in Central Tunisia and to demonstrate the role of these models in geological, hydrogeological and hydrological study. The 3D model is also coupled in this study with piezometric and hydrochemistry study, so a new information’s plan was mapped by multiple GIS techniques like Spatial analysis and interpolation;in order 1) to comprehend the hydrodynamic of the aquifer, 2) to quantify surface and subsurface water resources and 3) to generate water management scenarios in the study area. To this end, several groundwater samples were collected and analyzed from wells and piezometers. Examining the corresponding physical and chemical parameters showed an increase in the concentrations of hydraulic conductivity in the center of the study area and it coincided with zones with high nutrient concentration. Recommendations are proposed in this zone.
文摘The capital of Georgia</span><span style="font-family:Verdana;">—Tbilisi has a very convenient location and is a node of the transit corridor. Along with natural-geological conditions, its complexity is due to the rapid demographic growth of the city in a highly “sensitive” area of the geological environment and the pressure of high engineering and agricultural activities. In Tbilisi</span></span><span style="font-family:Verdana;">,</span><span style="font-family:Verdana;"> it is observed almost all type</span><span style="font-family:Verdana;">s</span><span style="font-family:""><span style="font-family:Verdana;"> of geological hazards, including landslide-gravitational, suffosion, debris/mudflows, river </span><span style="font-family:Verdana;">bank erosion and inundation </span></span><span style="font-family:Verdana;">were </span><span style="font-family:Verdana;">caused by groundwater. These hazard</span><span style="font-family:Verdana;">s</span><span style="font-family:Verdana;"> cause</span><span style="font-family:""><span style="font-family:Verdana;"> high damages to the residential houses and other infrastructure facilities. Most importantly and most tragically is that these kind of negative geological events are often accompanied by human casualties. The study discusses the geological processes developed in March 2021 in the corridor of the Vashlij</span><span style="font-family:Verdana;">vari-Lisi road (Machavariani Street). The information obtained from the study,</span><span style="font-family:Verdana;"> reflects the triggering factors of the geological hazards, also damages caused by them, and provides recommendations for short-term and long-term protective measures that should ensure the sustainable operation of the road and other infrastructure facilities.
文摘In the event of natural disasters, Sierra Leone like any other country loses lives as well as properties and natural resources. Despite notable occurrences of small disasters in the country, only on August 14th sugarloaf landslide and the resulting flash flood (twin disasters) which affected Regent and other communities in 2017 have captured both national and international attention due to their alarming impacts. To obtain a better knowledge on the nature of the disasters, this research considered the geological context of the landslide and focused on statistical analysis of the impacts of the twin disasters using Statistical Package for Social Sciences (SPSS). Geological field-based approach and self-administered questionnaires of both closed and open-ended questions, personal interviews and observations were adopted as research techniques. Descriptive statistics and qualitative analysis were used to analyze the data of the research. Relevant literature from books, journals, and newspapers was also consulted, including Radio, Television discussions and the internet. Slope destabilization that caused the Landslide was linked to the geology of sub-surface formation (highly weathered olivine gabbro), lineaments and the rate of weathering. Study showed remarkable economic, social and political impacts as a consequence of the twin disasters. Study also revealed that families assisted the most in both financial and non-financial ways to the victims, and renowned misappropriation of donated disaster funds. All variables tested using student t-distribution and chi-square test of independence accepted the hypothesis. Information obtained from this work could be fundamental for policy makers and development practitioners (Osuteye & Leck, 2017).
