0 INTRODUTION The Kuqa Depression,situated along the northern margin of the Tarim Basin,holds substantial geological significance due to its intricate sedimentary burial history,tectonic history,and the evolution of h...0 INTRODUTION The Kuqa Depression,situated along the northern margin of the Tarim Basin,holds substantial geological significance due to its intricate sedimentary burial history,tectonic history,and the evolution of hydrocarbon source rocks(Jiang et al.,2024;Zhang et al.,2023;Huang et al.,2019;Yang et al.,2017;Jia et al.,2003;Hendrix,2000).展开更多
Cadmium(Cd)contamination in soil can lead to food chain accumulation and greatly impacts on human health.Bioremediation has gained more and more attention due to its environment-friendly,high efficiency and low-cost.I...Cadmium(Cd)contamination in soil can lead to food chain accumulation and greatly impacts on human health.Bioremediation has gained more and more attention due to its environment-friendly,high efficiency and low-cost.In this work,we studied the impact of phosphate solubilizing bacterial agent(PSBA)on Cd bioavailability,microbial communities in soil and Cd accumulation in lettuce plants with pot experiment and field trial.Results of pot experiment showed that PSBA could decrease the bioavailability of Cd(Cd-acid extractable from 3.30 to 2.34mg/kg,Cd-reducible from 1.94 to 1.56 mg/kg),promote lettuce plants growth(increased by 33.85%height and by 33.65%fresh weight)and reduce the accumulation of Cd(from 5.85 to 3.73 mg/kg)in lettuce plants.High-throughput sequencing identified that PSBA could change the composition and structure of the soil microbial communities.The relative abundances of the three ecologically beneficial bacterial families of Pseudomonadaceae,Burkholderiaceae,and Enterobacteriaceae increased from 2.29%to 5.13%,0.56%to 5.24%,and 1.87%to 16.93%,respectively.And the former two were positively correlated with redox potential(Eh)(R^(2)=0.474,p<0.05,R^(2)=0.590,p<0.01,respectively).The bacterial networks were more complex in PSBA treatment,reflecting through more links(from 1893 to 2185)and a higher average degree(from 38.242 to 45.052)and density(from 0.390 to 0.469).Results of field trial demonstrated that PSBA could also decrease Cd content in lettuce plants and microbial composition in soil.This study indicated that PSBA could be served as an alternative material in bioremediation of Cd contamination in soil.展开更多
Shale formations have recently gained plenty of attention owing to their large amounts of reserves.Horizontal drilling and hydraulic fracturing are the proposed approaches for the development of shale formations.The e...Shale formations have recently gained plenty of attention owing to their large amounts of reserves.Horizontal drilling and hydraulic fracturing are the proposed approaches for the development of shale formations.The extended information of the mechanical properties of shale formation is crucial for designing a successful hydraulic fracturing operation.On the other hand,the mechanical properties of such organic-rich formations are greatly affected by the mechanical characteristics of the present kerogen(organic matter),which dramatically changes during the maturation process.In this study,a Qingshankou shale sample containing kerogen type I is mechanically investigated at different maturity levels using the grid nanoindentation approach.To this end,the original immature sample is artificially matured during hydrous(HP)and anhydrous(AHP)pyrolysis.More than 930 nanoindentation tests were performed on grids of 9×8 on the surface of 13 samples with different maturities.The test results showed that the presence of water during pyrolysis can significantly affect the shale sample's mechanical characteristics.In higher temperatures and higher levels of maturity,the role of water becomes more pronounced.During hydrous pyrolysis,kerogen produces larger amounts of oil and bitumen,which become progressively porous.While the original sample showed a Young's modulus value of more than 48 GPa,and it fluctuated between approximately 19 and 32 GPa during the HP scenario and between 17 and 34 GPa during the AHP process.In terms of hardness,the original sample exhibited an initial value of about 1.1 GPa and more mature samples reflected hardness values in the range of approximately 0.3 and 0.97 GPa in both scenarios.According to the trends of mechanical properties during maturation,mechanical properties decreased at the initial stage of maturation and remained relatively constant during the oil window.Then,another decline was detected at the wet-gas window's closure.In the dry-gas window,HP and AHP scenarios exhibited different behaviors mainly due to the chemical structure of the kerogen residue.展开更多
Groundwater is essential for maintaining public health,promoting economic development,and ensuring ecosystem stability in arid and semi-arid regions.The northwestern Ordos Basin(China)primarily relies on groundwater f...Groundwater is essential for maintaining public health,promoting economic development,and ensuring ecosystem stability in arid and semi-arid regions.The northwestern Ordos Basin(China)primarily relies on groundwater from multilayered aquifer systems;however,our knowledge of the hydrochemical characteristics and water quality of groundwater in this region is limited.Here,we employed a newly collected dataset of 94 groundwater samples from different aquifers to constrain the source,controlling processes of fluoride in groundwater,and its potential health risk in the area.Groundwater is characterized by Na-Cl and Na-SO_(4) types with a minor Na-HCO_(3) type,which is primarily controlled by ion exchange,silicate weathering,and the dissolution of carbonate and evaporite minerals.Of the groundwater samples,42%exceeded the fluoride limit of 1.5 mg/L established by the World Health Organization(WHO).This is mainly attributed to geogenic sources,including fluorine-bearing mineral dissolution,cation exchange,evaporation,and competitive adsorption.The water quality index suggests that most samples are unsuitable for drinking.Health risk assessment results based on the Monte Carlo simulation indicate that children face significantly higher non-carcinogenic health risks from fluoride exposure than adults(both males and females).These findings provide new insights into the complex hydrogeochemical evolution of fluoride in groundwater and the groundwater quality status in multi-aquifer systems,contributing to the sustainable development and management of groundwater resources in the Ordos Basin.展开更多
Significant progress has been made in exploring shale gas resources in the middle-upper Permian strata of western Hubei.However,the unclear geochemical characteristics and origins of the gas have hindered a comprehens...Significant progress has been made in exploring shale gas resources in the middle-upper Permian strata of western Hubei.However,the unclear geochemical characteristics and origins of the gas have hindered a comprehensive understanding of reservoir evolution and have constrained integrated resource development.This study involved a 28-h desorption experiment in which gases released from shales of the Dalong and Gufeng Formations were systematically collected for compositional and carbon—hydrogen isotope analyses.Comparing the compositional and geochemical characteristics of the desorbed gases and investigating their genetic origins resulted in four main findings:(1)Gas composition during the middle stage of desorption,excluding H_(2)S,best represents the original reservoir fluid,with component variations linked to adsorption and diffusion capacities.(2)Both shales display similar gas compositions with trace H_(2)S;the Dalong shale contains lower CH_(4),CO_(2),and H_(2)S but higher C_(2)H_(6)and N_(2).(3)Carbon and hydrogen isotopes indicate oil-type thermogenic gases,with carbon isotope reversal reflecting tectonic uplift,depressurization,and the mixing of primary kerogen-derived and secondary oil-/condensate-derived gases.(4)N_(2)likely originates from ammonium-bearing silicate decomposition,CO_(2)is mainly inorganic,from thermal carbonate decomposition with minor organic contribution,and H_(2)S may result from oil cracking or thermochemical sulfate reduction.This study provides a comprehensive record of the fluid characteristics of middle-upper Permian shale gas reservoirs and enhances the understanding of their formation and evolution.展开更多
The origin of tight reservoirs in the Yanchang Formation of the Ordos Basin and their relationship with hydrocarbon charging remain unclear.Based on petrological observations,physical property analysis,fluid inclusion...The origin of tight reservoirs in the Yanchang Formation of the Ordos Basin and their relationship with hydrocarbon charging remain unclear.Based on petrological observations,physical property analysis,fluid inclusion system analysis and in situ U-Pb dating,the sequence of tight sandstone reservoir densification and oil charging was determined.Through petrological observations,fluid inclusion analysis and physical property analysis,it is concluded that compaction and cementation are the primary causes of reservoir densification.When the content of calcite cement is less than or equal to 7%,compaction dominates densification;otherwise,cementation becomes more significant.However,determining the exact timing of compaction densification proved challenging.Microscopic observations revealed that oil charging likely occurred either before or during the densification of the reservoir.According to in situ U-Pb dating and the porosity evolution curve,cementation densification occurred between 167.0±20.0 Ma and 151.8 Ma.Temperature measurements of the aqueous inclusions indicate that oil charging occurred between 125.0 and 96.0 Ma,suggesting that densification preceded oil charging.This study provides valuable insights for the future exploration of tight oil reservoirs in the Ordos Basin.展开更多
Iron oxide-copper–gold(IOCG)deposits encompass a diverse set of mineralization styles,leading to outstanding questions about how different alteration facies are related across a single ore-producing system and the ov...Iron oxide-copper–gold(IOCG)deposits encompass a diverse set of mineralization styles,leading to outstanding questions about how different alteration facies are related across a single ore-producing system and the overarching mechanisms of ore genesis.This study investigates the age and characteristics of mineralization at the La Farola deposit,a hematite-dominated IOCG deposit located at the southern margin of the Candelaria-Punta del Cobre IOCG district of northern Chile.Two lithologically-controlled ore bodies occur along the WSW-ENE striking,∼18°NNW-dipping contact between the Lower Cretaceous Chañarcillo Group and Punta del Cobre Formation.Syn-mineralization N-S to NNW-SSE striking sinistral strike-slip faults likely acted as fluid pathways.Distinct mineral assemblages include an early Na-Ca assemblage(albite-scapolite)overprinted by skarnoid garnet with minor pyroxene,Ca-Fe(magnetite-actinolite),and K-Fe(magnetite-k-feldspar-biotite and minor sulfides)assemblages.The main sulfide mineralization(chalcopyrite-pyrite with minor bornite)is associated with specular hematite-white mica-K-feldspar-calcite and overprints all previous assemblages.The presence of hematite as the dominant Fe-oxide phase associated with Cu mineralization is characteristic of lower-temperature IOCG deposits,and may be a result of La Farola’s stratigraphic position<700 m higher than other deposits in the district.New U-Pb ages of 115.7±1.2 Ma for garnet and Re-Os ages of∼113–114 Ma for sulfides indicate mineralization occurred within a 3-million-year timeframe.These findings confirm hematite-dominant mineralization at La Farola was coeval with IOCG mineralization across the district.This research contributes to understanding IOCG systems and their formation mechanisms,highlighting the control local geological structures and alteration processes has on the diversity of mineralization types associated with a single IOCG system.展开更多
The global ocean is a major source of the climate-relevant atmospheric trace gas nitrous oxide(N_(2)O).However,an accurate assessment of the global oceanic emissions of N_(2)O is hampered by missing data on dissolved ...The global ocean is a major source of the climate-relevant atmospheric trace gas nitrous oxide(N_(2)O).However,an accurate assessment of the global oceanic emissions of N_(2)O is hampered by missing data on dissolved N_(2)O from large regions such as the Southern Ocean.To address this deficit,N_(2)O was measured in the Prydz Bay in February 2015 during the 31st Chinese National Antarctic Research Expedition.N_(2)O concentrations(saturation)in the surface layer were generally low(undersaturation with respect to atmospheric equilibrium)and ranged from 13.3 nmol/L to 16.1 nmol/L(83%–102%)at the time of sampling.A comparison of our observations with archived data revealed that no discernible trend in N_(2)O concentrations in the surface waters of Prydz Bay could be detected for the period between 2006 and 2015.Temperature and salinity changes driven by meltwater input were the predominant controls on N_(2)O concentrations in surface waters.At depth,the distribution of N_(2)O concentrations was dominated by production via nitrification in offshore deep waters and vertical convection in the shelf waters,where concentrations were lower and gradients were less steep.Our results suggest a rather unusual pattern of N_(2)O distribution in the Prydz Bay(low N_(2)O in shelf waters compared with the open ocean),providing important insights into the coastal dynamics of N_(2)O in high-latitude polar regions.展开更多
Understanding the thermo-mechanical behavior of various rock types is important in a wide range of geoscientific applications.In this study,the effects of elevated temperature treatments(250℃-750℃)on the elastic res...Understanding the thermo-mechanical behavior of various rock types is important in a wide range of geoscientific applications.In this study,the effects of elevated temperature treatments(250℃-750℃)on the elastic response(wave velocities and mechanical properties)of dolerite,retrieved from a borehole in the Sonhat Basin,India,were analyzed.The results showed that uniaxial compressive strength(UCS)increased by 15.4%at 250℃ compared to their room temperature(25℃)counterparts due to drying effects and inherent rock strengthening,but declined steadily at higher temperatures due to heat-induced microcracking and mineral transformations.Similarly,Young's modulus of the rock samples increased up to 250℃ and then decreased sharply above 450℃,aligning with the brittle-ductile transition temperature of 450℃.Petrographic and electron microscopy analyses of the samples revealed the development of intergranular and intragranular fractures at temperatures above 450℃,contributing to the observed mechanical weakening.Furthermore,ultrasonic wave velocities(P-and S-waves)exhibited significant reductions with increasing temperature,highlighting microstructural damage.These findings provide critical knowledge for designing underground geological engineering structures by identifying temperature thresholds and understanding mechanical degradation under thermal stress.The findings are particularly relevant for underground coal gasification(UCG)projects in the Sonhat Coalfield,where dolerite sills overlying coal seams may be exposed to significant heat.The identified threshold temperatures and trends in mechanical behaviour provide valuable insights for addressing structural stability challenges and mitigating environmental risks,such as surface subsidence.展开更多
Seed to soil contact is critical for successful germination and establishment.The seed coat micromorphology is a stable trait that has contributed significant information to the phylogenetic classification of angiospe...Seed to soil contact is critical for successful germination and establishment.The seed coat micromorphology is a stable trait that has contributed significant information to the phylogenetic classification of angiosperms.Seed morphology refers to the physical characteristics of seeds,such as their size,shape,color,texture,and structure.The characteristics can vary greatly among different plant species and can provide important information about the plants'life cycle,ecological requirements,and evolutionary history.The aim of this work was to describe the 34 species representing 23 botanical families that were collected to study the micromorphological features of seeds from Khaplu and Skardu mountainous area.Seed shape,color,and texture were observed under a light and scanning microscope and stereo microscope.Micromorphological and ultrastructural data have proved useful in determining seed plant evolution,classification,ecology,and phylogeny.Seed shapes varied from elliptic,oblong,ovate,pyramidal,and spherical.Surface sculpturing varied from rugulate,negative reticulate,reticulate,foveolate,granular and striated.The seed size varied enormously from very minute Matricaria chamomilla 0.33 mm×0.06 mm to very large seed Elaeagnus angustifolia 13.76 mm×4.70 mm.Epicuticular projections,anticlinal wall,periclinal wall,wall ornamentation,and seed texture were also studied under scanning electron microscopy.Most of the seed colors were brown and black except Carthamus tinctorius which exhibits creamy white color.A principal component analysis was used to identify the most outliers in seed micromorphology and provide a significant explanation.A taxonomic key based on micromorphological features has been constructed to assist botanists in identifying species and genera,and to support the conservation of seed bank resources.展开更多
The Arno River Basin(Central Italy)is affected by a considerable anthropogenic pressure due to the presence of large cities and widespread industrial and agricultural practices.In this work,26 water samples from the A...The Arno River Basin(Central Italy)is affected by a considerable anthropogenic pressure due to the presence of large cities and widespread industrial and agricultural practices.In this work,26 water samples from the Arno River and its main tributaries were analyzed to assess the water pollution status.The geochemical composition of the Arno River changes from the source(dominated by a Ca-HCO_(3) facies)to the mouth(where a Na-Cl(SO4)chemistry prevails)with an increasing quality deterioration,as suggested by the Chemical Water Quality Index,due to anthropogenic contributions and seawater intrusion before flowing into the Ligurian Sea.The Ombrone and Usciana tributaries introduce anthropogenic pollutants into the Arno River,whilst Elsa tributary supplies significant contents of geogenic sulfate.The concentrations of dissolved nitrate and nitrite(up to 63 and 9 mg/L,respectively)and the respective isotopic values of𝛿15N and𝛿18O were also determined to understand origin and fate of the N-species in the Arno River Basin surface waters.The combined application of𝛿15N-NO_(3) and𝛿18O-NO_(3) and N-source apportionment modelling allowed the identification of soil organic nitrogen and sewage and domestic wastes as primary sources for dissolved NO_(3)-.The𝛿15N-NO_(2) and𝛿18O-NO_(2) values suggest that the nitrification process affects the ARB waters,thus controlling the abundances and proportion of the N-species.Our work indicates that additional efforts are needed to improve management strategies to reduce the release of nitrogenated species to the surface waters of the Arno River Basin,since little progress has been made from the early 2000s.展开更多
Eclogite lenses in marbles from the Dabie-Sulu ultrahigh-pressure （UHP） terrane are deeply subducted meta-sedimentary rocks. Zircons in these rocks have been used to constrain the ages of prograde and UHP metamorphi...Eclogite lenses in marbles from the Dabie-Sulu ultrahigh-pressure （UHP） terrane are deeply subducted meta-sedimentary rocks. Zircons in these rocks have been used to constrain the ages of prograde and UHP metamorphism during subduction, and later retrograde metamorphism during exhumation. Inherited （detrital） and metamorphic zircons were distinguished on the basis of transmitted light microscopy, cathodoluminescence （CL） imaging, trace element contents and mineral inclusions. The distribution of mineral inclusions combined with CL imaging of the metamorphic zircon make it possible to relate zircon zones （domains） to different metamorphic stages. Domain 1 consists of rounded, oblong and spindly cores with dark-luminescent images, and contains quartz eclogite facies mineral inclusion assemblages, indicating formation under high-pressure （HP） metamorphic conditions of T = 571-668℃ and P =1.7-2.02 GPa. Domain 2 always surrounds domain 1 or occurs as rounded and spindly cores with white-luminescent images. It contains coesite eclogite facies mineral inclusion assemblages, indicating formation under UHP metamorphic conditions of T = 782-849℃ and P 〉 5.5 GPa. Domain 3, with gray-luminescent images, always surrounds domain 2 and occurs as the outermost zircon rim. It is characterized by low-pressure mineral inclusion assemblages, which are related to regional amphibolite facies retrograde metamorphism of T = 600- 710℃ and P = 0.7-1.2 GPa. The three metamorphic zircon domains have distinct ages; sample H1 from the Dabie terrane yielded SHRIMP ages of 245 ± 4 Ma for domain 1, 235 ± 3 Ma for domain 2 and 215± 6 Ma for domain 3, whereas sample H2 from the Sulu terrane yielded similar ages of 244 ± 4 Ma, 233 ± 4 Ma and 214 ± 5 Ma for Domains 1, 2 and 3, respectively. The mean ages of these zones suggest that subduction to UHP depths took place over 10-11 Ma and exhumation of the rocks occurred over a period of 19-20 Ma. Thus, subduction from - 55 km to 〉 160 km deep mantle depth took place at rates of approximately 9.5-10.5 km/Ma and exhumation from depths 〉160 km to the base of the crust at -30 km occurred at approximately 6.5 km/Ma. We propose a model for these rocks involving deep subduction of continental margin lithosphere followed by ultrafast exhumation driven by buoyancy forces after break-off of the UHP slab deep within the mantle.展开更多
In deep mineral exploration, the acquisition of audio magnetotelluric （AMT） data is severely affected by ambient noise near the observation sites; This near-field noise restricts investigation depths. Mathematical m...In deep mineral exploration, the acquisition of audio magnetotelluric （AMT） data is severely affected by ambient noise near the observation sites; This near-field noise restricts investigation depths. Mathematical morphological filtering （MMF） proved effective in suppressing large-scale strong and variably shaped noise, typically low-frequency noise, but can not deal with pulse noise of AMT data. We combine compressive sensing and MMF. First we use MMF to suppress the large-scale strong ambient noise; second, we use the improved orthogonal match pursuit （IOMP） algorithm to remove the residual pulse noise. To remove the noise and protect the useful AMT signal, a redundant dictionary that matches with spikes and is insensitive to the useful signal is designed. Synthetic and field data from the Luzong field suggest that the proposed method suppresses the near-source noise and preserves the signal well; thus, better results are obtained that improve the output of either MMF or IOMP.展开更多
Various combinations of diamond, moissanite, zircon, corundum, rutile and titanitehave been recovered from the Bulqiza chromitites. More than 10 grains of diamond have been recovered, most of which are pale yellow to ...Various combinations of diamond, moissanite, zircon, corundum, rutile and titanitehave been recovered from the Bulqiza chromitites. More than 10 grains of diamond have been recovered, most of which are pale yellow to reddish–orange to colorless. The grains are all 100–300 μm in size and mostly anhedral, but with a range of morphologies including elongated, octahedral and subhedral varieties. Their identification was confirmed by a characteristic shift in the Raman spectra between 1325 cm-1 and 1333 cm-1, mostly at 1331.51 cm-1 or 1326.96 cm-1. This investigation extends the occurrence of diamond and moissanite to the Bulqiza chromitites in the Eastern Mirdita Ophiolite. Integration of the mineralogical, petrological and geochemical data of the Bulqiza chromitites suggests their multi–stage formation. Magnesiochromite grains and perhaps small bodies of chromitite formed at various depths in the upper mantle, and encapsulated the ultra–high pressure, highly reduced and crustal minerals. Some oceanic crustal slabs containing the magnesiochromite and their inclusion were later trapped in suprasubduction zones, where they were modified by tholeiitic and boninitic arc magmas, thus changing the magnesiochromite compositions and depositing chromitite ores in melt channels.展开更多
The Early Paleozoic evolution of the northern margin of Gondwana is characterized by several episodes of bimodal magmatism intruded or outpoured within thick sedimentary basins. These processes are well recorded in th...The Early Paleozoic evolution of the northern margin of Gondwana is characterized by several episodes of bimodal magmatism intruded or outpoured within thick sedimentary basins. These processes are well recorded in the Variscan blocks incorporated in the Ligurian Alps because they experienced low temperature Alpine metamorphism. During the Paleozoic, these blocks, together with the other Alpine basements, were placed between the Corsica-Sardinia and the Bohemian Massif along the northern margin of Gondwana. In this framework, they host several a variegated lithostratigraphy forming two main complexes(Complexs I and II) that can be distinguished by both the protoliths and their crosscutting relationships, which indicate that the acidic and mafic intrusives of Complex II cut an already folded sequence made of sediments, basalts and granitoids of Complex I. Both complexes were involved in the Variscan orogenic phases as highlighted by the pervasive eclogite-amphibolite facies schistosity(foliation II). However, rare relicts of a metamorphic foliation at amphibolite facies conditions(foliation I)is locally preserved only in the rocks of Complex I. It is debatable if this schistosity was produced during the early folding event e occurred between the emplacement of Complex I and II e rather than during an early stage of the Variscan metamorphic cycle.New SHRIMP and LA ICP-MS Ue Pb zircon dating integrated with literature data, provide emplacement ages of the several volcanic or intrusive bodies of both complexes. The igneous activity of Complex I is dated between 507 ± 15 Ma and 494 ± 5 Ma, while Complex II between 467 ± 12 Ma and 445.5 ± 12 Ma.The folding event recorded only by the Complex I should therefore have occurred between 494 ± 5 Ma and 467 ± 12 Ma. The Variscan eclogite-amphibolite facies metamorphism is instead constrained between ~420 Ma and ~300 Ma. These ages and the geochemical signature of these rocks allow constraining the Early Paleozoic tectono-magmatic evolution of the Ligurian blocks, from a middleeupper Cambrian rifting stage, through the formation of an Early Ordovician volcanic arc during the Rheic Ocean subduction, until a Late Ordovician extension related to the arc collapse and subsequent rifting of the PaleoThetys. Furthermore, the ~420-350 Ma ages from zircon rims testify to thermal perturbations that may be associated with the Silurian rifting-related magmatism, followed by the subduction-collisional phases of the Variscan orogeny.展开更多
The Bulqiza ultramafic massif, which is part of the eastern Mirdita ophiolite of northern Albania, is world renowned for its high-Cr chromitite deposits. High-Cr chromitites hosted in the mantle section are the crysta...The Bulqiza ultramafic massif, which is part of the eastern Mirdita ophiolite of northern Albania, is world renowned for its high-Cr chromitite deposits. High-Cr chromitites hosted in the mantle section are the crystallized products of boninitic melts in a supra-subduction zone(SSZ). However,economically important high-Al chromitites are also present in massive dunite of the mantle-crust transition zone(MTZ). Chromian-spinel in the high-Al chromitites and dunites of the MTZ have much lower Cr~# values(100 Cr/(Cr+Al))(47.7-55.1 and 46.5-51.7, respectively) than those in the high-Cr chromitites(78.2-80.4), harzburgites(72.6-77.9) and mantle dunites(79.4-84.3). The chemical differences in these two types of chromitites are reflected in the behaviors of their platinum-group elements(PGE).The high-Cr chromitites are rich in IPGE relative to PPGE with 0.10-0.45 PPGE/IPGE ratios, whereas the high-Al chromitites have relatively higher PPGE/IPGE ratios between 1.20 and 7.80. The calculated melts in equilibrium with the high-Cr chromitites are boninitic-like, and those associated with the high-Al chromitites are MORB-like but with hydrous, oxidized and TiO-poor features. We propose that the coexistence of both types of chromitites in the Bulqiza ultramafic massif may indicates a change in magma composition from MORB-like to boninitic-like in a proto-forearc setting during subduction initiation.展开更多
Test geochemistry of planktonic foraminifera is an indispensable tool in reconstructing past ocean hydrological changes. It is essential to investigate region-specific implications of test geochemistry,although those ...Test geochemistry of planktonic foraminifera is an indispensable tool in reconstructing past ocean hydrological changes. It is essential to investigate region-specific implications of test geochemistry,although those established from other regions can be broadly applied. In this study, characteristics of6180 and Mg/Ca from tests of four planktonic foraminiferal species, Globigerinoides ruber sensu stricto(s.s.), Globigerinoides sacculifer, Pulleniatina obliquiloculata and Neogloboquadrina dutertrei, from 60 coretop sediment samples retrieved from the Indonesian Throughflow(ITF) region were studied. These geochemical data were compared with modern hydrographic profiles in order to assess their relations and to investigate potential implications of test geochemical parameters in reconstructing past oceanographic change in the ITF region. Calcification depths of these four species were first estimated based on comparison between measured test δ180 and predicted calcite δ^(18)O that was calculated from modern temperature and salinity. The results indicate that G. ruber s.s. and G. sacculifer calcify within the mixedlayer at 0-50 m and 20-75 m, respectively, whereas P. obliquiloculata and N. dutertrei calcify within the thermocline at around 75 to 125 m. A combined study of excess Mg/Ca(difference between measured and predicted Mg/Ca) and salinity suggests that salinity exerts a negligible impact on test Mg/Ca of these foraminiferal species in the ITF region. Comparison of test Mg/Ca-derived temperatures with temperature profiles of the upper 200 m of the water column from the seas of the ITF region also indicate calcification depths of these species, which match well with the above estimations using test δ^(18)O. It further indicates that G. sacculifer may be more sensitive in reflecting changes in the depth of the mixedlayer, highlighting a potential use of Mg/Ca temperature difference between G. ruber s.s. and G. sacculifer in reconstructing the depth of the mixed-layer in the ITF region.展开更多
Measuring the relative importance and assigning weights to conditioning factors of land- slides occurrence are significant for landslide prevention and/or mitigation. In this contribution, a fractal method is introduc...Measuring the relative importance and assigning weights to conditioning factors of land- slides occurrence are significant for landslide prevention and/or mitigation. In this contribution, a fractal method is introduced for measuring the spatial relationships between landslides and condition- ing factors （such as faults, rivers, geological boundaries, and roads）, and for assigning weights to condi- tioning factors for mapping of landslide susceptibility. This method can be expressed as p=C~, where d is the fractal dimension, and C is a constant. This relationship indicates a fractal relation between land- slide density （p） and distances to conditioning factors （6）. The case of d〉0 suggests a significant spatial correlation between landslides and conditioning factors. The larger the d （〉0） value, the stronger the spatial correlation is between landslides and a specific conditioning factor. Two case studies in South China were examined to demonstrate the usefulness of this novel method.展开更多
This paper presents preliminary results of three-dimensional thermomechanical finite-element models of a parameter study to compute the current temperature and stress distribution in the subduction zone of the central...This paper presents preliminary results of three-dimensional thermomechanical finite-element models of a parameter study to compute the current temperature and stress distribution in the subduction zone of the central Andes （16°S-26°S） up to a depth of 400 km, the bottom of the asthenosphere. For this purpose a simulation running over c. 50,000 years will be realized based on the geometry of a generic subduction zone and an elasto-viscoplastic Drucker-Prager rheology. The kinematic and thermal boundary conditions as well as the rheological parameters represent the current state of the study area. In future works the model will be refined using a systematic study of physical parameters in order to estimate the influence of the main parameters （e.g. viscosity, fault friction, velocity, shear heating） on the results of the reference model presented here. The reference model is kept as simple as possible to be able to estimate the influence of the parameters in future studies in the best possible way, whilst minimizing comnutational time.展开更多
The spatial occurrence of iron in kaolinite of coal measures west of Beijing was studied by using the Mossbauer spectroscopy technique and a step-by-step method of fitting. The results show that there are three kinds ...The spatial occurrence of iron in kaolinite of coal measures west of Beijing was studied by using the Mossbauer spectroscopy technique and a step-by-step method of fitting. The results show that there are three kinds of spatial occurrence in kaolinites： tetra-coordination Fe（3＋） in Si-O tetrahedrons, sexa-coordination Fe（3＋） in A1--O octahedrons and sexa-coordination Fe（2＋） in A1-O octahedrons, respectively occupying 51.72 %, 37.25 % and 11.03 %, Neither foreign matter of magnetic Fe mineral nor superparamagnetic goethite exists in kaolin concentrates. Fe in kaolin concentrates cannot be removed by conventional methods, which is significant for both theoretical research on kaolinite minerology and practical use of the kaolinites of coal measures west of Beijing.The research also illustrates that the Mossbauer spectroscopy is an effective method in studying the micro-superfine Fe in kaolin.展开更多
基金supported by the National Key Research and Development Project(No.2019YFA0708601)the National Natural Science Foundation of China(No.4231101056)the Chinese Academy of Geological Sciences Basic Research Fund(No.JKYZD202402)。
文摘0 INTRODUTION The Kuqa Depression,situated along the northern margin of the Tarim Basin,holds substantial geological significance due to its intricate sedimentary burial history,tectonic history,and the evolution of hydrocarbon source rocks(Jiang et al.,2024;Zhang et al.,2023;Huang et al.,2019;Yang et al.,2017;Jia et al.,2003;Hendrix,2000).
基金supported by the Science and Technology Programs of Department of Natural Resources of Zhejiang Province,China(No.2020006)the Zhejiang Provincial Natural Science Foundation of China(No.LGF22D030001)the Key R&D Program of Zhejiang Province,China(No.2021C04020)。
文摘Cadmium(Cd)contamination in soil can lead to food chain accumulation and greatly impacts on human health.Bioremediation has gained more and more attention due to its environment-friendly,high efficiency and low-cost.In this work,we studied the impact of phosphate solubilizing bacterial agent(PSBA)on Cd bioavailability,microbial communities in soil and Cd accumulation in lettuce plants with pot experiment and field trial.Results of pot experiment showed that PSBA could decrease the bioavailability of Cd(Cd-acid extractable from 3.30 to 2.34mg/kg,Cd-reducible from 1.94 to 1.56 mg/kg),promote lettuce plants growth(increased by 33.85%height and by 33.65%fresh weight)and reduce the accumulation of Cd(from 5.85 to 3.73 mg/kg)in lettuce plants.High-throughput sequencing identified that PSBA could change the composition and structure of the soil microbial communities.The relative abundances of the three ecologically beneficial bacterial families of Pseudomonadaceae,Burkholderiaceae,and Enterobacteriaceae increased from 2.29%to 5.13%,0.56%to 5.24%,and 1.87%to 16.93%,respectively.And the former two were positively correlated with redox potential(Eh)(R^(2)=0.474,p<0.05,R^(2)=0.590,p<0.01,respectively).The bacterial networks were more complex in PSBA treatment,reflecting through more links(from 1893 to 2185)and a higher average degree(from 38.242 to 45.052)and density(from 0.390 to 0.469).Results of field trial demonstrated that PSBA could also decrease Cd content in lettuce plants and microbial composition in soil.This study indicated that PSBA could be served as an alternative material in bioremediation of Cd contamination in soil.
基金supported by the National Natural Science Foundation of China(Grant No.U22A20574)the Hainan Province Science and Technology Special Fund(Grant No.ZDYF2023GXJS009).
文摘Shale formations have recently gained plenty of attention owing to their large amounts of reserves.Horizontal drilling and hydraulic fracturing are the proposed approaches for the development of shale formations.The extended information of the mechanical properties of shale formation is crucial for designing a successful hydraulic fracturing operation.On the other hand,the mechanical properties of such organic-rich formations are greatly affected by the mechanical characteristics of the present kerogen(organic matter),which dramatically changes during the maturation process.In this study,a Qingshankou shale sample containing kerogen type I is mechanically investigated at different maturity levels using the grid nanoindentation approach.To this end,the original immature sample is artificially matured during hydrous(HP)and anhydrous(AHP)pyrolysis.More than 930 nanoindentation tests were performed on grids of 9×8 on the surface of 13 samples with different maturities.The test results showed that the presence of water during pyrolysis can significantly affect the shale sample's mechanical characteristics.In higher temperatures and higher levels of maturity,the role of water becomes more pronounced.During hydrous pyrolysis,kerogen produces larger amounts of oil and bitumen,which become progressively porous.While the original sample showed a Young's modulus value of more than 48 GPa,and it fluctuated between approximately 19 and 32 GPa during the HP scenario and between 17 and 34 GPa during the AHP process.In terms of hardness,the original sample exhibited an initial value of about 1.1 GPa and more mature samples reflected hardness values in the range of approximately 0.3 and 0.97 GPa in both scenarios.According to the trends of mechanical properties during maturation,mechanical properties decreased at the initial stage of maturation and remained relatively constant during the oil window.Then,another decline was detected at the wet-gas window's closure.In the dry-gas window,HP and AHP scenarios exhibited different behaviors mainly due to the chemical structure of the kerogen residue.
基金supported by the Natural Science Foundation of Inner Mongolia Autonomous Region(2024QN04014)the Open Research Fund of Yinshanbeilu Grassland Eco-hydrology National Observation and Research Station,China Institute of Water Resources and Hydropower Research(Grant No.YSS202401)+2 种基金Scientific Research Support Program for Introducing Talents at the Inner Mongolia Autonomous Region of China(DC2400002177 and DC2400003177)Major Projects of Erdos Science and Technology(Project No.2022EEDSKJZDZX015)Applied technology research and development project in Jungar Banner of Inner Mongolia Autonomous Region of China(2023YY-13).
文摘Groundwater is essential for maintaining public health,promoting economic development,and ensuring ecosystem stability in arid and semi-arid regions.The northwestern Ordos Basin(China)primarily relies on groundwater from multilayered aquifer systems;however,our knowledge of the hydrochemical characteristics and water quality of groundwater in this region is limited.Here,we employed a newly collected dataset of 94 groundwater samples from different aquifers to constrain the source,controlling processes of fluoride in groundwater,and its potential health risk in the area.Groundwater is characterized by Na-Cl and Na-SO_(4) types with a minor Na-HCO_(3) type,which is primarily controlled by ion exchange,silicate weathering,and the dissolution of carbonate and evaporite minerals.Of the groundwater samples,42%exceeded the fluoride limit of 1.5 mg/L established by the World Health Organization(WHO).This is mainly attributed to geogenic sources,including fluorine-bearing mineral dissolution,cation exchange,evaporation,and competitive adsorption.The water quality index suggests that most samples are unsuitable for drinking.Health risk assessment results based on the Monte Carlo simulation indicate that children face significantly higher non-carcinogenic health risks from fluoride exposure than adults(both males and females).These findings provide new insights into the complex hydrogeochemical evolution of fluoride in groundwater and the groundwater quality status in multi-aquifer systems,contributing to the sustainable development and management of groundwater resources in the Ordos Basin.
基金supported by the Hubei Provincial Natural Science Foundation of China(Grant No.2022CFB490,2024AFD381)Science and Technology Project of Hubei Geological Bureau(Grant No.KJ2024-2,KJ2025-14)Open Fund of Technology Innovation Center for Shale oil and Gas Accumulation Theory and Engineering in Southern Complex Structural Area,China Geological Survey(Grant No.SOG-202410).
文摘Significant progress has been made in exploring shale gas resources in the middle-upper Permian strata of western Hubei.However,the unclear geochemical characteristics and origins of the gas have hindered a comprehensive understanding of reservoir evolution and have constrained integrated resource development.This study involved a 28-h desorption experiment in which gases released from shales of the Dalong and Gufeng Formations were systematically collected for compositional and carbon—hydrogen isotope analyses.Comparing the compositional and geochemical characteristics of the desorbed gases and investigating their genetic origins resulted in four main findings:(1)Gas composition during the middle stage of desorption,excluding H_(2)S,best represents the original reservoir fluid,with component variations linked to adsorption and diffusion capacities.(2)Both shales display similar gas compositions with trace H_(2)S;the Dalong shale contains lower CH_(4),CO_(2),and H_(2)S but higher C_(2)H_(6)and N_(2).(3)Carbon and hydrogen isotopes indicate oil-type thermogenic gases,with carbon isotope reversal reflecting tectonic uplift,depressurization,and the mixing of primary kerogen-derived and secondary oil-/condensate-derived gases.(4)N_(2)likely originates from ammonium-bearing silicate decomposition,CO_(2)is mainly inorganic,from thermal carbonate decomposition with minor organic contribution,and H_(2)S may result from oil cracking or thermochemical sulfate reduction.This study provides a comprehensive record of the fluid characteristics of middle-upper Permian shale gas reservoirs and enhances the understanding of their formation and evolution.
基金supported by the project of the Exploration Department of the Huabei Oilfield Company of Sinopec(No.34550008-20-ZC0609-0031).
文摘The origin of tight reservoirs in the Yanchang Formation of the Ordos Basin and their relationship with hydrocarbon charging remain unclear.Based on petrological observations,physical property analysis,fluid inclusion system analysis and in situ U-Pb dating,the sequence of tight sandstone reservoir densification and oil charging was determined.Through petrological observations,fluid inclusion analysis and physical property analysis,it is concluded that compaction and cementation are the primary causes of reservoir densification.When the content of calcite cement is less than or equal to 7%,compaction dominates densification;otherwise,cementation becomes more significant.However,determining the exact timing of compaction densification proved challenging.Microscopic observations revealed that oil charging likely occurred either before or during the densification of the reservoir.According to in situ U-Pb dating and the porosity evolution curve,cementation densification occurred between 167.0±20.0 Ma and 151.8 Ma.Temperature measurements of the aqueous inclusions indicate that oil charging occurred between 125.0 and 96.0 Ma,suggesting that densification preceded oil charging.This study provides valuable insights for the future exploration of tight oil reservoirs in the Ordos Basin.
基金National Science Foundation Grant#1822064 to J.Singleton,Fondecyt grant#1230161 to I.del Real,and a Society of Economic Geologists Student Research Grant to N.Seymour supported this work.
文摘Iron oxide-copper–gold(IOCG)deposits encompass a diverse set of mineralization styles,leading to outstanding questions about how different alteration facies are related across a single ore-producing system and the overarching mechanisms of ore genesis.This study investigates the age and characteristics of mineralization at the La Farola deposit,a hematite-dominated IOCG deposit located at the southern margin of the Candelaria-Punta del Cobre IOCG district of northern Chile.Two lithologically-controlled ore bodies occur along the WSW-ENE striking,∼18°NNW-dipping contact between the Lower Cretaceous Chañarcillo Group and Punta del Cobre Formation.Syn-mineralization N-S to NNW-SSE striking sinistral strike-slip faults likely acted as fluid pathways.Distinct mineral assemblages include an early Na-Ca assemblage(albite-scapolite)overprinted by skarnoid garnet with minor pyroxene,Ca-Fe(magnetite-actinolite),and K-Fe(magnetite-k-feldspar-biotite and minor sulfides)assemblages.The main sulfide mineralization(chalcopyrite-pyrite with minor bornite)is associated with specular hematite-white mica-K-feldspar-calcite and overprints all previous assemblages.The presence of hematite as the dominant Fe-oxide phase associated with Cu mineralization is characteristic of lower-temperature IOCG deposits,and may be a result of La Farola’s stratigraphic position<700 m higher than other deposits in the district.New U-Pb ages of 115.7±1.2 Ma for garnet and Re-Os ages of∼113–114 Ma for sulfides indicate mineralization occurred within a 3-million-year timeframe.These findings confirm hematite-dominant mineralization at La Farola was coeval with IOCG mineralization across the district.This research contributes to understanding IOCG systems and their formation mechanisms,highlighting the control local geological structures and alteration processes has on the diversity of mineralization types associated with a single IOCG system.
基金The National Natural Science Foundation of China under contract No.41906193the Scientific Research Foundation of Third Institute of Oceanography,Ministry of Natural Resources,under contract No.2019033+2 种基金the Natural Science Foundation of Fujian Province under contract No.2019J05147the Federal Ministry of Education and Research of Germany under contract No.FKZ 03F03F0783Athe National Polar Special Program under contract Nos IRASCC 01-01-02 and IRASCC 02-02.
文摘The global ocean is a major source of the climate-relevant atmospheric trace gas nitrous oxide(N_(2)O).However,an accurate assessment of the global oceanic emissions of N_(2)O is hampered by missing data on dissolved N_(2)O from large regions such as the Southern Ocean.To address this deficit,N_(2)O was measured in the Prydz Bay in February 2015 during the 31st Chinese National Antarctic Research Expedition.N_(2)O concentrations(saturation)in the surface layer were generally low(undersaturation with respect to atmospheric equilibrium)and ranged from 13.3 nmol/L to 16.1 nmol/L(83%–102%)at the time of sampling.A comparison of our observations with archived data revealed that no discernible trend in N_(2)O concentrations in the surface waters of Prydz Bay could be detected for the period between 2006 and 2015.Temperature and salinity changes driven by meltwater input were the predominant controls on N_(2)O concentrations in surface waters.At depth,the distribution of N_(2)O concentrations was dominated by production via nitrification in offshore deep waters and vertical convection in the shelf waters,where concentrations were lower and gradients were less steep.Our results suggest a rather unusual pattern of N_(2)O distribution in the Prydz Bay(low N_(2)O in shelf waters compared with the open ocean),providing important insights into the coastal dynamics of N_(2)O in high-latitude polar regions.
基金funded by“The Pearl River Talent Recruitment Program”in 2019(Grant No.2019CX01G338)Guangdong Province and Guangdong Provincial Basic and Applied Basic Research Fund Committee(2022A1515240073).
文摘Understanding the thermo-mechanical behavior of various rock types is important in a wide range of geoscientific applications.In this study,the effects of elevated temperature treatments(250℃-750℃)on the elastic response(wave velocities and mechanical properties)of dolerite,retrieved from a borehole in the Sonhat Basin,India,were analyzed.The results showed that uniaxial compressive strength(UCS)increased by 15.4%at 250℃ compared to their room temperature(25℃)counterparts due to drying effects and inherent rock strengthening,but declined steadily at higher temperatures due to heat-induced microcracking and mineral transformations.Similarly,Young's modulus of the rock samples increased up to 250℃ and then decreased sharply above 450℃,aligning with the brittle-ductile transition temperature of 450℃.Petrographic and electron microscopy analyses of the samples revealed the development of intergranular and intragranular fractures at temperatures above 450℃,contributing to the observed mechanical weakening.Furthermore,ultrasonic wave velocities(P-and S-waves)exhibited significant reductions with increasing temperature,highlighting microstructural damage.These findings provide critical knowledge for designing underground geological engineering structures by identifying temperature thresholds and understanding mechanical degradation under thermal stress.The findings are particularly relevant for underground coal gasification(UCG)projects in the Sonhat Coalfield,where dolerite sills overlying coal seams may be exposed to significant heat.The identified threshold temperatures and trends in mechanical behaviour provide valuable insights for addressing structural stability challenges and mitigating environmental risks,such as surface subsidence.
基金supported by Princess Nourah bint Abdulrahman University Researchers Supporting Project number(PNURSP2025R101),Princess Nourah bint Abdulrahman University,Riyadh,Saudi Arabia.
文摘Seed to soil contact is critical for successful germination and establishment.The seed coat micromorphology is a stable trait that has contributed significant information to the phylogenetic classification of angiosperms.Seed morphology refers to the physical characteristics of seeds,such as their size,shape,color,texture,and structure.The characteristics can vary greatly among different plant species and can provide important information about the plants'life cycle,ecological requirements,and evolutionary history.The aim of this work was to describe the 34 species representing 23 botanical families that were collected to study the micromorphological features of seeds from Khaplu and Skardu mountainous area.Seed shape,color,and texture were observed under a light and scanning microscope and stereo microscope.Micromorphological and ultrastructural data have proved useful in determining seed plant evolution,classification,ecology,and phylogeny.Seed shapes varied from elliptic,oblong,ovate,pyramidal,and spherical.Surface sculpturing varied from rugulate,negative reticulate,reticulate,foveolate,granular and striated.The seed size varied enormously from very minute Matricaria chamomilla 0.33 mm×0.06 mm to very large seed Elaeagnus angustifolia 13.76 mm×4.70 mm.Epicuticular projections,anticlinal wall,periclinal wall,wall ornamentation,and seed texture were also studied under scanning electron microscopy.Most of the seed colors were brown and black except Carthamus tinctorius which exhibits creamy white color.A principal component analysis was used to identify the most outliers in seed micromorphology and provide a significant explanation.A taxonomic key based on micromorphological features has been constructed to assist botanists in identifying species and genera,and to support the conservation of seed bank resources.
文摘The Arno River Basin(Central Italy)is affected by a considerable anthropogenic pressure due to the presence of large cities and widespread industrial and agricultural practices.In this work,26 water samples from the Arno River and its main tributaries were analyzed to assess the water pollution status.The geochemical composition of the Arno River changes from the source(dominated by a Ca-HCO_(3) facies)to the mouth(where a Na-Cl(SO4)chemistry prevails)with an increasing quality deterioration,as suggested by the Chemical Water Quality Index,due to anthropogenic contributions and seawater intrusion before flowing into the Ligurian Sea.The Ombrone and Usciana tributaries introduce anthropogenic pollutants into the Arno River,whilst Elsa tributary supplies significant contents of geogenic sulfate.The concentrations of dissolved nitrate and nitrite(up to 63 and 9 mg/L,respectively)and the respective isotopic values of𝛿15N and𝛿18O were also determined to understand origin and fate of the N-species in the Arno River Basin surface waters.The combined application of𝛿15N-NO_(3) and𝛿18O-NO_(3) and N-source apportionment modelling allowed the identification of soil organic nitrogen and sewage and domestic wastes as primary sources for dissolved NO_(3)-.The𝛿15N-NO_(2) and𝛿18O-NO_(2) values suggest that the nitrification process affects the ARB waters,thus controlling the abundances and proportion of the N-species.Our work indicates that additional efforts are needed to improve management strategies to reduce the release of nitrogenated species to the surface waters of the Arno River Basin,since little progress has been made from the early 2000s.
基金the National 973 Project of Chinese Ministry of Science and Technology （Grant No. 2003CB716502） the Natural Science Foundation of China （Grant No. 40399143） +1 种基金 the German Science Foundation （DFG grant No. GE 1152/2-2 , WE2850/3- 1）.
文摘Eclogite lenses in marbles from the Dabie-Sulu ultrahigh-pressure （UHP） terrane are deeply subducted meta-sedimentary rocks. Zircons in these rocks have been used to constrain the ages of prograde and UHP metamorphism during subduction, and later retrograde metamorphism during exhumation. Inherited （detrital） and metamorphic zircons were distinguished on the basis of transmitted light microscopy, cathodoluminescence （CL） imaging, trace element contents and mineral inclusions. The distribution of mineral inclusions combined with CL imaging of the metamorphic zircon make it possible to relate zircon zones （domains） to different metamorphic stages. Domain 1 consists of rounded, oblong and spindly cores with dark-luminescent images, and contains quartz eclogite facies mineral inclusion assemblages, indicating formation under high-pressure （HP） metamorphic conditions of T = 571-668℃ and P =1.7-2.02 GPa. Domain 2 always surrounds domain 1 or occurs as rounded and spindly cores with white-luminescent images. It contains coesite eclogite facies mineral inclusion assemblages, indicating formation under UHP metamorphic conditions of T = 782-849℃ and P 〉 5.5 GPa. Domain 3, with gray-luminescent images, always surrounds domain 2 and occurs as the outermost zircon rim. It is characterized by low-pressure mineral inclusion assemblages, which are related to regional amphibolite facies retrograde metamorphism of T = 600- 710℃ and P = 0.7-1.2 GPa. The three metamorphic zircon domains have distinct ages; sample H1 from the Dabie terrane yielded SHRIMP ages of 245 ± 4 Ma for domain 1, 235 ± 3 Ma for domain 2 and 215± 6 Ma for domain 3, whereas sample H2 from the Sulu terrane yielded similar ages of 244 ± 4 Ma, 233 ± 4 Ma and 214 ± 5 Ma for Domains 1, 2 and 3, respectively. The mean ages of these zones suggest that subduction to UHP depths took place over 10-11 Ma and exhumation of the rocks occurred over a period of 19-20 Ma. Thus, subduction from - 55 km to 〉 160 km deep mantle depth took place at rates of approximately 9.5-10.5 km/Ma and exhumation from depths 〉160 km to the base of the crust at -30 km occurred at approximately 6.5 km/Ma. We propose a model for these rocks involving deep subduction of continental margin lithosphere followed by ultrafast exhumation driven by buoyancy forces after break-off of the UHP slab deep within the mantle.
基金supported by the National High Technology Research and Development Program of China(No.2014AA06A602)National Natural Science Foundation of China(No.41404111)Natural Science Foundation of Hunan Province(No.2015JJ3088)
文摘In deep mineral exploration, the acquisition of audio magnetotelluric （AMT） data is severely affected by ambient noise near the observation sites; This near-field noise restricts investigation depths. Mathematical morphological filtering （MMF） proved effective in suppressing large-scale strong and variably shaped noise, typically low-frequency noise, but can not deal with pulse noise of AMT data. We combine compressive sensing and MMF. First we use MMF to suppress the large-scale strong ambient noise; second, we use the improved orthogonal match pursuit （IOMP） algorithm to remove the residual pulse noise. To remove the noise and protect the useful AMT signal, a redundant dictionary that matches with spikes and is insensitive to the useful signal is designed. Synthetic and field data from the Luzong field suggest that the proposed method suppresses the near-source noise and preserves the signal well; thus, better results are obtained that improve the output of either MMF or IOMP.
基金funded by grants from the NSF China(Nos.41502062,41672046,41541017,41641015)the China Geological Survey(Nos.DD20160023-01,201511022)+2 种基金National Key Research and Development Project of China(2016YFC0600310)from the Institute of Geology,Chinese Academy of Geological Sciences(J1526)IGCP–649
文摘Various combinations of diamond, moissanite, zircon, corundum, rutile and titanitehave been recovered from the Bulqiza chromitites. More than 10 grains of diamond have been recovered, most of which are pale yellow to reddish–orange to colorless. The grains are all 100–300 μm in size and mostly anhedral, but with a range of morphologies including elongated, octahedral and subhedral varieties. Their identification was confirmed by a characteristic shift in the Raman spectra between 1325 cm-1 and 1333 cm-1, mostly at 1331.51 cm-1 or 1326.96 cm-1. This investigation extends the occurrence of diamond and moissanite to the Bulqiza chromitites in the Eastern Mirdita Ophiolite. Integration of the mineralogical, petrological and geochemical data of the Bulqiza chromitites suggests their multi–stage formation. Magnesiochromite grains and perhaps small bodies of chromitite formed at various depths in the upper mantle, and encapsulated the ultra–high pressure, highly reduced and crustal minerals. Some oceanic crustal slabs containing the magnesiochromite and their inclusion were later trapped in suprasubduction zones, where they were modified by tholeiitic and boninitic arc magmas, thus changing the magnesiochromite compositions and depositing chromitite ores in melt channels.
基金supported by Italian 1:50,000 Geological Mapping (CARGdR egione Liguria Project, University of Pavia grants)
文摘The Early Paleozoic evolution of the northern margin of Gondwana is characterized by several episodes of bimodal magmatism intruded or outpoured within thick sedimentary basins. These processes are well recorded in the Variscan blocks incorporated in the Ligurian Alps because they experienced low temperature Alpine metamorphism. During the Paleozoic, these blocks, together with the other Alpine basements, were placed between the Corsica-Sardinia and the Bohemian Massif along the northern margin of Gondwana. In this framework, they host several a variegated lithostratigraphy forming two main complexes(Complexs I and II) that can be distinguished by both the protoliths and their crosscutting relationships, which indicate that the acidic and mafic intrusives of Complex II cut an already folded sequence made of sediments, basalts and granitoids of Complex I. Both complexes were involved in the Variscan orogenic phases as highlighted by the pervasive eclogite-amphibolite facies schistosity(foliation II). However, rare relicts of a metamorphic foliation at amphibolite facies conditions(foliation I)is locally preserved only in the rocks of Complex I. It is debatable if this schistosity was produced during the early folding event e occurred between the emplacement of Complex I and II e rather than during an early stage of the Variscan metamorphic cycle.New SHRIMP and LA ICP-MS Ue Pb zircon dating integrated with literature data, provide emplacement ages of the several volcanic or intrusive bodies of both complexes. The igneous activity of Complex I is dated between 507 ± 15 Ma and 494 ± 5 Ma, while Complex II between 467 ± 12 Ma and 445.5 ± 12 Ma.The folding event recorded only by the Complex I should therefore have occurred between 494 ± 5 Ma and 467 ± 12 Ma. The Variscan eclogite-amphibolite facies metamorphism is instead constrained between ~420 Ma and ~300 Ma. These ages and the geochemical signature of these rocks allow constraining the Early Paleozoic tectono-magmatic evolution of the Ligurian blocks, from a middleeupper Cambrian rifting stage, through the formation of an Early Ordovician volcanic arc during the Rheic Ocean subduction, until a Late Ordovician extension related to the arc collapse and subsequent rifting of the PaleoThetys. Furthermore, the ~420-350 Ma ages from zircon rims testify to thermal perturbations that may be associated with the Silurian rifting-related magmatism, followed by the subduction-collisional phases of the Variscan orogeny.
基金financially supported by the National Natural Science Foundation of China(grants No.41541017,41641015,41720104009)the China Geological Survey(grants No.DD20160023-01,201511022)the Research funding from the Chinese Academy of Geological Sciences(grant No.YYWF201702)
文摘The Bulqiza ultramafic massif, which is part of the eastern Mirdita ophiolite of northern Albania, is world renowned for its high-Cr chromitite deposits. High-Cr chromitites hosted in the mantle section are the crystallized products of boninitic melts in a supra-subduction zone(SSZ). However,economically important high-Al chromitites are also present in massive dunite of the mantle-crust transition zone(MTZ). Chromian-spinel in the high-Al chromitites and dunites of the MTZ have much lower Cr~# values(100 Cr/(Cr+Al))(47.7-55.1 and 46.5-51.7, respectively) than those in the high-Cr chromitites(78.2-80.4), harzburgites(72.6-77.9) and mantle dunites(79.4-84.3). The chemical differences in these two types of chromitites are reflected in the behaviors of their platinum-group elements(PGE).The high-Cr chromitites are rich in IPGE relative to PPGE with 0.10-0.45 PPGE/IPGE ratios, whereas the high-Al chromitites have relatively higher PPGE/IPGE ratios between 1.20 and 7.80. The calculated melts in equilibrium with the high-Cr chromitites are boninitic-like, and those associated with the high-Al chromitites are MORB-like but with hydrous, oxidized and TiO-poor features. We propose that the coexistence of both types of chromitites in the Bulqiza ultramafic massif may indicates a change in magma composition from MORB-like to boninitic-like in a proto-forearc setting during subduction initiation.
基金supported by the National Natural Science Foundation of China(Grant Nos.41176044 and 41576045)Shaanxi Provincial Technology Foundation for Selected Overseas Chinese Scholar(Grant No.Shaan Renshe[2015]No.1190)
文摘Test geochemistry of planktonic foraminifera is an indispensable tool in reconstructing past ocean hydrological changes. It is essential to investigate region-specific implications of test geochemistry,although those established from other regions can be broadly applied. In this study, characteristics of6180 and Mg/Ca from tests of four planktonic foraminiferal species, Globigerinoides ruber sensu stricto(s.s.), Globigerinoides sacculifer, Pulleniatina obliquiloculata and Neogloboquadrina dutertrei, from 60 coretop sediment samples retrieved from the Indonesian Throughflow(ITF) region were studied. These geochemical data were compared with modern hydrographic profiles in order to assess their relations and to investigate potential implications of test geochemical parameters in reconstructing past oceanographic change in the ITF region. Calcification depths of these four species were first estimated based on comparison between measured test δ180 and predicted calcite δ^(18)O that was calculated from modern temperature and salinity. The results indicate that G. ruber s.s. and G. sacculifer calcify within the mixedlayer at 0-50 m and 20-75 m, respectively, whereas P. obliquiloculata and N. dutertrei calcify within the thermocline at around 75 to 125 m. A combined study of excess Mg/Ca(difference between measured and predicted Mg/Ca) and salinity suggests that salinity exerts a negligible impact on test Mg/Ca of these foraminiferal species in the ITF region. Comparison of test Mg/Ca-derived temperatures with temperature profiles of the upper 200 m of the water column from the seas of the ITF region also indicate calcification depths of these species, which match well with the above estimations using test δ^(18)O. It further indicates that G. sacculifer may be more sensitive in reflecting changes in the depth of the mixedlayer, highlighting a potential use of Mg/Ca temperature difference between G. ruber s.s. and G. sacculifer in reconstructing the depth of the mixed-layer in the ITF region.
基金financial support from the National Natural Science Foundation of China (No. 41522206)the MOST Special Fund from the State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences (No. MSFGPMR03-3)
文摘Measuring the relative importance and assigning weights to conditioning factors of land- slides occurrence are significant for landslide prevention and/or mitigation. In this contribution, a fractal method is introduced for measuring the spatial relationships between landslides and condition- ing factors （such as faults, rivers, geological boundaries, and roads）, and for assigning weights to condi- tioning factors for mapping of landslide susceptibility. This method can be expressed as p=C~, where d is the fractal dimension, and C is a constant. This relationship indicates a fractal relation between land- slide density （p） and distances to conditioning factors （6）. The case of d〉0 suggests a significant spatial correlation between landslides and conditioning factors. The larger the d （〉0） value, the stronger the spatial correlation is between landslides and a specific conditioning factor. Two case studies in South China were examined to demonstrate the usefulness of this novel method.
文摘This paper presents preliminary results of three-dimensional thermomechanical finite-element models of a parameter study to compute the current temperature and stress distribution in the subduction zone of the central Andes （16°S-26°S） up to a depth of 400 km, the bottom of the asthenosphere. For this purpose a simulation running over c. 50,000 years will be realized based on the geometry of a generic subduction zone and an elasto-viscoplastic Drucker-Prager rheology. The kinematic and thermal boundary conditions as well as the rheological parameters represent the current state of the study area. In future works the model will be refined using a systematic study of physical parameters in order to estimate the influence of the main parameters （e.g. viscosity, fault friction, velocity, shear heating） on the results of the reference model presented here. The reference model is kept as simple as possible to be able to estimate the influence of the parameters in future studies in the best possible way, whilst minimizing comnutational time.
基金Project 3042013 supported by Natural Science Foundation of Beijing
文摘The spatial occurrence of iron in kaolinite of coal measures west of Beijing was studied by using the Mossbauer spectroscopy technique and a step-by-step method of fitting. The results show that there are three kinds of spatial occurrence in kaolinites： tetra-coordination Fe（3＋） in Si-O tetrahedrons, sexa-coordination Fe（3＋） in A1--O octahedrons and sexa-coordination Fe（2＋） in A1-O octahedrons, respectively occupying 51.72 %, 37.25 % and 11.03 %, Neither foreign matter of magnetic Fe mineral nor superparamagnetic goethite exists in kaolin concentrates. Fe in kaolin concentrates cannot be removed by conventional methods, which is significant for both theoretical research on kaolinite minerology and practical use of the kaolinites of coal measures west of Beijing.The research also illustrates that the Mossbauer spectroscopy is an effective method in studying the micro-superfine Fe in kaolin.
