This study selects geochemical data of basalts from different seamounts in the Mid-Pacific Mountains province and conducts analyses of major and trace elements as well as Sr-Nd-Pb isotopes to explore the tectonic evol...This study selects geochemical data of basalts from different seamounts in the Mid-Pacific Mountains province and conducts analyses of major and trace elements as well as Sr-Nd-Pb isotopes to explore the tectonic evolution,petrogenesis,and mantle-source magama characteristics of the Mid-Pacific Mountains.The basalts from the Mid-Pacific Mountains are predominantly alkali basalts,rich in alkalies,and changing in potassium.They exhibit geochemical features of ocean island basalts(OIB),with distinct fractionation between light and heavy rare-earth elements and a pronounced Ce negative anomaly(δ_(Ce)=0.16–1.10,average 0.84),along with enrichment in large ion lithophile elements(LILEs).The Mid-Pacific Mountains are intraplate ocean island basalts formed by mantle plume(hotspot)activity,originating mainly from an enriched mantle magma source region,and most of them have undergone low degree of partial melting and a certain degree of crystalline differentiation,with negligible contamination from oceanic crust materials.The Mid-Pacific Mountains exhibit ratios of^(87)Sr/^(86)Sr(i)(0.702733–0.704313,average 0.703452)and^(143)Nd/^(144)Nd(i)(0.512698–0.512996,average 0.512846)which are close to the HIMU mantle endmember,and ratios of 206Pb/204Pb(18.953–19.803),^(207)Pb/^(204)Pb(15.54–15.62)and^(208)Pb/^(204)Pb(38.813–39.514)which are close to the EMII mantle end-member.Combined with the isotopic geochemical characteristics in the West Pacific Seamounts province,the basalts from the Mid-Pacific Mountains were considered to represent a certain proportion of mixing mantle end-members between the HIMU and EMII,possibly formed by the mixing of the HIMU superplume in the South Pacific hotspot region with the EMII secondary mantle plume in the transition zone during their ascent.展开更多
The complexity of the seismicity pattern for the subduction zone along the oceanic plate triggered the outer rise events and revealed cyclic tectonic deformation conditions along the plate subduction zones.The outer r...The complexity of the seismicity pattern for the subduction zone along the oceanic plate triggered the outer rise events and revealed cyclic tectonic deformation conditions along the plate subduction zones.The outer rise earthquakes have been observed along the Sunda arc,following the estimated rupture area of the 2005 M_(W)8.6 Nias earthquakes.Here,we used kinematic waveform inversion(KIWI)to obtain the source parameters of the 14 May 2021 M_(W)6.6 event off the west coast of northern Sumatra and to define the fault plane that triggered this outer rise event.The KIWI algorithm allows two types of seismic source to be configured:the moment tensor model to describe the type of shear with six moment tensor components and the Eikonal model for the rupture of pure double-couple sources.This method was chosen for its flexibility to be applied for different sources of seismicity and also for the automated full-moment tensor solution with real-time monitoring.We used full waveform traces from 8 broadband seismic stations within 1000 km epicentral distances sourced from the Incorporated Research Institutions for Seismology(IRIS-IDA)and Geofon GFZ seismic record databases.The initial origin time and hypocenter values are obtained from the IRIS-IDA.The synthetic seismograms used in the inversion process are based on the existing regional green function database model and were accessed from the KIWI Tools Green's Function Database.The obtained scalar seismic moment value is 1.18×10^(19)N·m,equivalent to a moment magnitude M_(W)6.6.The source parameters are 140°,44°,and−99°for the strike,dip,and rake values at a centroid depth of 10.2 km,indicating that this event is a normal fault earthquake that occurred in the outer rise area.The outer rise events with normal faults typically occur at the shallow part of the plate,with nodal-plane dips predominantly in the range of 30°-60°on the weak oceanic lithosphere due to hydrothermal alteration.The stress regime around the plate subduction zone varies both temporally and spatially due to the cyclic influences of megathrust earthquakes.Tensional outer rise earthquakes tend to occur after the megathrust events.The relative timing of these events is not known due to the viscous relaxation of the down going slab and poroelastic response in the trench slope region.The occurrence of the 14 May 2021 earthquake shows the seismicity in the outer rise region in the strongly coupled Sunda arc subduction zone due to elastic bending stress within the duration of the seismic cycle.展开更多
Nitrogen(N)and phosphorus(P)are essential nutrients and can significantly impact primary productivity of the ecosystem causing water environmental problems.However,their cycling mechanisms are not well understood in a...Nitrogen(N)and phosphorus(P)are essential nutrients and can significantly impact primary productivity of the ecosystem causing water environmental problems.However,their cycling mechanisms are not well understood in alpine mountains with climate change.Hence,94 samples of river water were collected from 2018 to 2020 in the headwaters of the Shule River Basin to assess the nutrients spatiotemporal distribution and combined ap-proach of water quality index to assess water quality and potential sources.The findings depict that high nutrient concentrations were found to coincide with snowmelt and glacial meltwater and rainfall recharge periods,while total flux peaked from June to September due to increased runoff.Notably,total nitrogen(TN)concentrations were significantly higher near the town,primarily attributed to the replenishment of nitrate(NO_(3)^(‒)-N)from live-stock manure.The high total P(TP)was near the glacier,which was attributed to the transportation of glacial sediments into the river,and pH was another critical factor.N was the primary nutrient limiting factor for the growth of phytoplankton in river water.Although the migration and transport of nutrients have altered with climate change,river water quality is good in alpine mountains based on an overall evaluation.These findings contribute to enriching nutrient datasets and highlight the importance of water resource management and water quality assessment in sensitive and fragile alpine mountains.展开更多
We present the preparation and measurement of the radioactive isotope^(37)Ar,which was produced using thermal neutrons from a reactor,as a calibration source for liquid xenon time projection chambers.^(37)Ar is a low-...We present the preparation and measurement of the radioactive isotope^(37)Ar,which was produced using thermal neutrons from a reactor,as a calibration source for liquid xenon time projection chambers.^(37)Ar is a low-energy calibration source with a half-life of 35.01 days,making it suitable for calibration in the low-energy region of liquid xenon dark-matter experiments.Radioactive isotope^(37)Ar was produced by irradiating ^(36)Ar with thermal neutrons.It was subsequently measured in a gaseous xenon time projection chamber(GXe TPC)to validate its radioactivity.Our results demonstrate that^(37)Ar is an effective and viable calibration source that offers precise calibration capabilities in the low-energy domain of xenon-based detectors.展开更多
We conducted a field campaign to investigate the chemical composition,sources,and light absorption of submicron aerosols(PM_(1))from early 2022 in Nanjing,China.The average concentration of PM_(1) was 31μg m^(−3),org...We conducted a field campaign to investigate the chemical composition,sources,and light absorption of submicron aerosols(PM_(1))from early 2022 in Nanjing,China.The average concentration of PM_(1) was 31μg m^(−3),organics(33%)constituted the largest fraction,followed by nitrate(30%),sulfate(18%),ammonium(15%),chloride(3%),and rBC(2%).Four organic aerosol(OA)subcomponents were identified,including two primary OA(POA)and two secondary OA(SOA).The less-oxidized SOA(LO-OOA)contributes the most to the total OA mass(59%).LO-OOA is tightly correlated with the tracer ion C_(2)H_(4)O_(2)^(+)from levoglucosan,and another aged biomass-burning derived species,K_(3)SO_(4)^(+),suggesting it was likely influenced by aged biomass-burning OA.Our study also revealed that fireworks during the Spring Festival have a detrimental impact on air quality,contributing to secondary formation and accumulation under static winter meteorological conditions,prolonging the pollution duration.Also,LO-OOA was found to have the strongest light-absorbing ability.Our results highlight that the light absorption of LO-OOA can mainly be attributed to the C_(x)H_(y)N^(+) family,increased with the double-bond equivalent value.The more-oxidized SOA(MO-OOA)exhibited a negligible light absorption and was strongly correlated with daytime photochemical processes,implying a light-bleaching effect.This study enhances our understanding of the regional contribution of biomass combustion and fireworks to PM_(1) pollution in Nanjing,a typical megacity in the Yangtze River Delta region,during winter,aiding in the development of strategies for long-term air quality improvement in the region.展开更多
Carbonyl compounds play a pivotal role in the formation of secondary pollutants such as O_(3) and SOA,signifi-cantly impacting air quality and human health.This study extended the observation period compared to previo...Carbonyl compounds play a pivotal role in the formation of secondary pollutants such as O_(3) and SOA,signifi-cantly impacting air quality and human health.This study extended the observation period compared to previous research,providing a long-term perspective on carbonyl compound variations and their environmental implica-tions.Atmospheric observations were conducted at Beijing(BJ)and Xianghe(XH)during the summer and winter months of 2018,2019,and 2023 to study the sources and impacts of carbonyl compounds in typical urban areas and peri‑urban areas.Notably,concentrations in the summer of 2023 increased compared to 2018 and 2019.The predominant carbonyl compounds—formaldehyde,acetaldehyde,and acetone—accounted for over 60%of the total.The mean values of OFP in BJ ranged from 18.55 to 58.61μg/m3,lower than those in XH(29.82 to 65.48μg/m3),with formaldehyde and acetaldehyde contributing over 80%of the total.SOAP exhibited a similar pattern,with values in XH(69.21 to 508.55μg/m3)significantly exceeding those in BJ(34.47 to 159.78μg/m3).The PMF model highlighted vehicle exhaust,secondary pollution,and biomass combustion as major sources of carbonyl compounds,emphasizing differences in source contributions between the two regions.This study’s com-parative analysis over different years and locations provides new insights into the dynamic changes in carbonyl compounds and their environmental importance.These results not only reinforce the importance of carbonyl compounds regulation but also offer a valuable reference for evaluating and refining emission control strategies during this period.展开更多
Oxidative potential(OP)can be used as an indicator of the health risks of particulate matter in the air.To study the variation and sources of OP,we conducted an observation of PM_(2.5) in a megacity in southern China ...Oxidative potential(OP)can be used as an indicator of the health risks of particulate matter in the air.To study the variation and sources of OP,we conducted an observation of PM_(2.5) in a megacity in southern China in winter and spring of 2021.The results show that the average concentration of PM_(2.5) decreased by 47%from winter to spring,while volume-normalized and mass-normalized OP(i.e.,OP_(v) and OP_(m))increased by 6%and 69%,respectively.It suggests that the decline of PM_(2.5) may not necessarily decrease the health risks and the intrinsic toxicity of PM_(2.5).Variations of OP_(v) and OP_(m) among different periods were related to the different source contributions and environmental conditions.The positive matrix factorization model was used to identify the major sources of OP_(v).OP_(v) was mainly contributed by biomass burning/industrial emissions(29%),soil/road dust(20%),secondary sulfate(14%),and coal combustion(13%)in winter.Different major sources were resolved to be secondary sulfate(36%),biological sources(21%),and marine vessels(20%)in spring,presenting the substantial contribution of biological sources.The analysis shows strong associations between OP_(v) and both live and dead bacteria,further confirming the important contribution of bioaerosols to the enhancement of OP.This study highlights the importance of understanding OP in ambient PM_(2.5) in terms of public health impact and provides a new insight into the biological contribution to OP.展开更多
Annual haze in Northern Thailand has become increasingly severe,impacting health and the environment.How-ever,the sources of the haze remain poorly quantified due to limited observational data on aerosol molecular tra...Annual haze in Northern Thailand has become increasingly severe,impacting health and the environment.How-ever,the sources of the haze remain poorly quantified due to limited observational data on aerosol molecular tracers.This study comprehensively investigates chemical composition of PM_(2.5),including both inorganic and organic compounds throughout haze and post-haze periods in 2019 at a rural site of Northern Thailand.Average PM_(2.5) concentrations during haze and post-haze period were 87±36 and 21±11μg/m^(3),respectively.Organic matter was the dominant contributor in PM_(2.5) mass,followed by water soluble inorganic ions and mineral dust.Molecular markers,including levoglucosan,dehydroabietic acid,and 4-nitrocatechol,and ions(Cl^(-),and K^(+)),were used to characterize low haze(PM_(2.5)<100μg/m^(3))and episodic haze(PM_(2.5)>100μg/m^(3)).Low haze is associated with local aerosols from agricultural waste burning,while episodic haze is linked to aged aerosols from mixed agricultural waste,softwood,and hardwood burning.Source apportionment incorporating these molecular markers in receptor modelling(Positive matrix factorization),identified three distinct biomass burning sources:mixed,local,and aged biomass burnings,contributing 31,19 and 13%of PM_(2.5) during haze period.During post-haze period,contributions shifted,with local biomass burning(32%)comparable to secondary sulfate(34%)and mixed dust and traffic sources(26%).These findings demonstrate that both regional and local sources con-tribute to severe haze,highlighting the need for integrated policies for cross-border cooperation as well as stricter regulations to reduce biomass burning in Northern Thailand and Southeast Asia.展开更多
To fully utilize the resources provided by optical fiber networks,a cross-band quantum light source generating photon pairs,where one photon in a pair is at C band and the other is at O band,is proposed in this work.T...To fully utilize the resources provided by optical fiber networks,a cross-band quantum light source generating photon pairs,where one photon in a pair is at C band and the other is at O band,is proposed in this work.This source is based on spontaneous four-wave mixing(SFWM)in a piece of shallow-ridge silicon waveguide.Theoretical analysis shows that the waveguide dispersion could be tailored by adjusting the ridge width,enabling broadband photon pair generation by SFWM across C band and O band.The spontaneous Raman scattering(SpRS)in silicon waveguides is also investigated experimentally.It shows that there are two regions in the spectrum of generated photons from SpRS,which could be used to achieve cross-band photon pair generation.A chip of shallow-ridge silicon waveguide samples with different ridge widths has been fabricated,through which cross-band photon pair generation is demonstrated experimentally.The experimental results show that the source can be achieved using dispersion-optimized shallow-ridge silicon waveguides.This cross-band quantum light source provides a way to develop new fiber-based quantum communication functions utilizing both C band and O band and extends applications of quantum networks.展开更多
The alkaline oceanic island basalts(OIBs)with under-saturated SiO2 and high contents of CaO and alkaline are usually attributed to mantle sources different from typical tholeiitic OIBs.Based on the results of high pre...The alkaline oceanic island basalts(OIBs)with under-saturated SiO2 and high contents of CaO and alkaline are usually attributed to mantle sources different from typical tholeiitic OIBs.Based on the results of high pressure and temperature experiment study,the genesis of silica under-saturated alkaline basaltic melts could be explained by the role of CO2,thus,the genetic relationship of alkaline basalts with CO2 has become a topic of relevance because it is closely related to the deep carbon cycle.The Magellan Seamount chain in the West Pacific Seamount Province has wide distribution of alkali basalts.For the first time,we collected alkaline basalt samples from the Kocebu Seamount of the Magellan Seamount chain and found that magmatic apatites widely occur in the less evolved volcanic rock samples,and the high contents of phosphorus should be a feature of the alkaline OIBs of the Magellan Seamounts.Compared with typical OIBs,these alkaline volcanic rocks have higher CaO and P2O5,lower SiO2 content,negative anomaly of high field strength elements(HFSEs),more distinctly negative anomaly of potassium(K)and the ubiquity of titanaugite,indicating a CO2-rich mantle source.Based on the relatively high K2O and TiO2 contents and La/Yb ratio and low MgO content of these alkaline rocks,we suggest that the volcanic rocks of the Magellan Seamounts are originated from carbonated eclogites derived possibly from ancient subducted altered oceanic crust.展开更多
Geological setting\;Jinding superlarge Pb\|Zn deposit lies in the Lanping basin between the Lancangjiang fracture zone and the Jinshajiang\|Ailaoshan fracture zone. The Lanping basin is a Meso\|Cenozoic rifting basin ...Geological setting\;Jinding superlarge Pb\|Zn deposit lies in the Lanping basin between the Lancangjiang fracture zone and the Jinshajiang\|Ailaoshan fracture zone. The Lanping basin is a Meso\|Cenozoic rifting basin whose basement consists of the Paleozoic strata. Mesozoic paralic and continental sediments with a thickness of about 20000m deposited in the basin. In the Paleocene, gypsum\|salt\|bearing strata with a thickness of more than 1000m accumulated. In the Cenozoic, collision of the Indian plate with the Eurasian plate resulted in strong folding and napping and subsequent extensions in the Oligocene and Pliocene. The extensions were responsible for alkaline magmatic intrusion in the centre and alkaline magmatic extrusion in the east.Faulting is well developed. N\|S\|trending Bijiang fault with a length of 120km links with the Jinshajiang fracture zone in the north and with the Lancangjiang fracture zone in the south, controlling on the Cenozoic Lanping rifting basin and acting as passage\|way for ore fluids.展开更多
Research on the distribution of mantle CO_(2)should involve comprehensive analysis from CO_(2)source to accumulation.The crust-mantle pathway system is the key controlling factor of the distribution of mantle CO_(2),b...Research on the distribution of mantle CO_(2)should involve comprehensive analysis from CO_(2)source to accumulation.The crust-mantle pathway system is the key controlling factor of the distribution of mantle CO_(2),but has received little attention.The pathway system and controlling factors of CO_(2)distribution in the Bohai Sea are analyzed using data on fault styles and information on the mantle and lithosphere.The relation between volcanic rocks and the distribution of mantle CO_(2)is reassessed using age data for CO_(2)accumulations.The distribution of mantle CO_(2)is controlled by uplift of the asthenosphere and upper mantle,magma conduits in the mantle and fault systems in the crust.Uplifted regions of the asthenosphere are accumulation areas for CO_(2).The area with uplift of the Moho exhibits accumulation of mantle CO_(2)at depth.CO_(2)was mainly derived from vertical migration through the upper mantle and lower crust.The fault style in the upper crust controls the distance of horizontal migration and the locations of CO_(2)concentrations.The distribution of mantle CO_(2)and volcanic rocks are not the same,but both probably followed the same pathways sometimes.Mantle CO_(2)in the Bohai Sea is concentrated in the Bozhong sag and the surrounding area,particularly in a trap that formed before 5.1 Ma and is connected to crustal faults(the Bozhang faults)and lithospheric faults(the Tanlu faults).展开更多
Based on the REE geochemistry data from the Baimazhai nickel deposit, Yunnan Province, the authors modeled the composition of the mantle source region by way of petrological mixing calculation, and further discussed t...Based on the REE geochemistry data from the Baimazhai nickel deposit, Yunnan Province, the authors modeled the composition of the mantle source region by way of petrological mixing calculation, and further discussed the genesis of this type of rocks. Both element geochemistry data and mixing calculation showed that lamprophyres in the Baimazhai nickel deposit were derived from a metasomatism-enrichment mantle and the fluids resulted from dehydration of a subducted slab which is comprised of ALK-, LREE- and incompatible element-rich sediments.展开更多
Mafic rocks comprising tholeiitic pillow basalt, dolerite and minor gabbro form the basal stratigraphic unit in the ca. 2.8 to 2.6 Ga Geita Greenstone Belt situated in the NW Tanzania Craton. They outcrop mainly along...Mafic rocks comprising tholeiitic pillow basalt, dolerite and minor gabbro form the basal stratigraphic unit in the ca. 2.8 to 2.6 Ga Geita Greenstone Belt situated in the NW Tanzania Craton. They outcrop mainly along the southern margin of the belt, and are at least 50 million years older than the supracrustal assemblages against which they have been juxtaposed. Geochemical analyses indicate that parts of the assemblage approach high Mg-tholeiite （more than 8 wt.% MgO）. This suite of samples has a restricted compositional range suggesting derivation from a chemically homogenous reservoir. Trace element modeling suggests that the mafic rocks were derived by partial melting within the spinel peridotite field from a source rock with a primitive mantle composition. That is, trace elements maintain primitive mantle ratios （Zr/Hf = 32-35, Ti/Zr - 107-147）, producing flat REE and HFSE profles [（La/Yb）pm = 0.9 -1.3], with abundances of 3-10 times primitive mantle and with minor negative anomalies of Nb [（Nb/ La）pm - 0.6-0.8] and Th [（Th/La）pm = 0.6-0.9]. Initial isotope compositions （εNd） range from 1.6 to 2.9 at 2.8 Ga and plot below the depleted mantle line suggesting derivation from a more enriched source compared to present day MORB mantle. The trace element composition and Nd isotopic ratios are similar to the mafic rocks outcropping -50 km south. The mafic rocks outcropping in the Geita area were erupted through oceanic crust over a short time period, between -2830 and-2820 Ma; are compositionally homogenous, contain little to no associated terrigenous sediments, and their trace element composition and short emplacement time resemble oceanic plateau basalts. They have been interpreted to be derived from a plume head with a primitive mantle composition.展开更多
This paper discusses the discrimination principles. deduction and methods for probing into the source composition of mantle-derived magma. The magmatophile (incompatible) source elements are not all optimal tracers fo...This paper discusses the discrimination principles. deduction and methods for probing into the source composition of mantle-derived magma. The magmatophile (incompatible) source elements are not all optimal tracers for mantle source composition. The ratios of two strong magmatophile elements (D<1) or the ratios of two trace elements with the same D value are not controlled by the formation mode and evolution degree of a magma, but maintain the characteristics of their composition in mantle source region prior to the magma formation. The ratios are related to different mantle-crust structures and dynamics. The mantle source composition of the Emeishan Basalt series is similar to that of the South Atlantic Rio Grande Rise-Walvis Ridge Basalts and Brazil continental-margin basalts. This may indicate that these basalt series might have similar source regions and tectonic environments.展开更多
Several types of felsic granitoid rocks have been recognized, intrusive in both the mantle and the crustal sequence of the Semail ophiolite. Several models have been proposed for the source of this suite of tonalites,...Several types of felsic granitoid rocks have been recognized, intrusive in both the mantle and the crustal sequence of the Semail ophiolite. Several models have been proposed for the source of this suite of tonalites, granodiorites, trondhjemites intrusions, however their genesis is still not clearly understood.The sampled Dadnah tonalites that intruded in the mantle section of the Semail ophiolite display arctype geochemical characteristics, are high siliceous, low-potassic, metaluminous to weakly peraluminous, enriched in LILE, show positive peaks for Ba, Pb, Eu, negative troughs for U, Ti and occur with low δ^(18)O_(H_2 O), moderate ε_(Sr) and negative eNd values. They have crystallized at temperatures that range from～550 ℃ to ～720 ℃ and pressure ranging from 4.4 kbar to 6.5 kbar. The isotopic ages from our tonalite samples range between 98.6 Ma and 94.9 Ma, slightly older and overlapping with the age of the metamorphic sole. Our field observations, mineralogical, petrological, geochemical, isotopic and melt inclusion data suggest that the Dadnah tonalites formed by partial melting(～10%-15% continuous or ～12% batch partial melting), accumulation of plagioclase, fractional crystallization(～55%-57%), and interaction with their host harzburgites. These tonalites were the end result of partial melting and subsequent contamination and mixing of ～4% oceanic sediments with ～96% oceanic lithosphere from the subducted slab. This MORB-type slab melt composed from ～97% recycled oceanic crust and ～3% of the overlying mantle.We suggest that a possible protolith for these tonalites was the basaltic lavas from the subducted oceanic slab that melted during the initial stages of the supra-subduction zone(SSZ), which was forming synchronously to the spreading ridge axis. The tonalite melts mildly modified due to low degree of mixing and interaction with the overlying lithospheric mantle. Subsequently, the Dadnah tonalites emplaced at the upper part of the mantle sequence of the Semail ophiolite and are geochemically distinct from the other mantle intrusive felsic granitoids to the south.展开更多
The Zhangjiakou-Xuanhua area is a mineral resource-concentrated area for gold-silver polymetallic ore deposits. The temporal and spatial distribution and origin of mineral resources have been argued for a long time. B...The Zhangjiakou-Xuanhua area is a mineral resource-concentrated area for gold-silver polymetallic ore deposits. The temporal and spatial distribution and origin of mineral resources have been argued for a long time. Based on the comprehensive studies of geochronology and sulfur, lead, oxygen, carbon and noble gas isotopes, it is considered that the temporal and spatial distribution of mineral resources in this area is obviously controlled by the Zhangjiakou-Xuanhua mantle branch structure, as is reflected by the occurrence of gold deposits in the inner parts and of Ag-Pb-Zn polymetallic ore deposits in the outer parts. The mineralization took place mainly during the Yanshanian period. Ore-forming materials came largely from the deep interior of the Earth, and hydrothermal fluids were derived predominantly from Yanshanian magmatism.展开更多
This study was conducted following research on metallogenesis in the Zhangjiajie-Xuanhua and East Hebei mantle branch structure zones. The Fuping mantle branch structure zone is one where Au, Cu and Ag poly-metallic o...This study was conducted following research on metallogenesis in the Zhangjiajie-Xuanhua and East Hebei mantle branch structure zones. The Fuping mantle branch structure zone is one where Au, Cu and Ag poly-metallic ore resources are concentrated in North Hebei. However, there has existed a long-standing controversy on the temporal-spatial distribution of ore resources and their ore-forming material sources. In terms of age dating and the comprehensive analysis of S, Pb, O, C and Si isotopes, it is considered that the temporal-spatial distribution of ore resources in this mantle branch structure zone is obviously controlled by the Fuping mantle branch structure. In space there is developed such a metallogenic pattern as to be Ag, Pb and Zn polymetallic ore deposits with gold appearing inside and copper appearing outside. Metallogenesis is dated mainly at Yanshanian, the ore-forming materials were derived predominantly from the deep interior of the Earth, and ore-forming fluids were derived largely from Yanshanian magmatism.展开更多
The composition of mantle-derived basalts reflects the nature of their mantle source regions,which constrain magma generation and composition.Here we present a new whole rock major and trace elements and phenocryst co...The composition of mantle-derived basalts reflects the nature of their mantle source regions,which constrain magma generation and composition.Here we present a new whole rock major and trace elements and phenocryst composition of the basaltic lava in the central Mariana Trough.These data provide insights into the mantle source characteristics affected by subduction components.The rocks range from basalts to basaltic andesites,which have high subduction-mobile element contents(e.g.,K,U,Th,LREE)related to N-MORB.The calculated temperature and depth of magma generation are about 1300℃and 30 km,respectively.Although the results above suggest that the addition of hydrous fluid and/or a melt derived from a slab decreases the temperature of mantle partial melting and mildly modifies the composition of a mantle source,the mantle source lithology from which primary magma is generated remains to be peridotite.展开更多
Principal component analysis(PCA)was employed to determine the implications of geochemical and isotopic data from Cenozoic volcanic activities in the Southeast Asian region,including China(South China Sea(SCS),Hainan ...Principal component analysis(PCA)was employed to determine the implications of geochemical and isotopic data from Cenozoic volcanic activities in the Southeast Asian region,including China(South China Sea(SCS),Hainan Island,Fujian-Zhejiang coast,Taiwan Island),and parts of Vietnam and Thailand.We analyzed 15 trace element indicators and 5 isotopic indicators for 623 volcanic rock samples collected from the study region.Two principal components(PCs)were extracted by PCA based on the trace elements and Sr-Nd-Pb isotopic ratios,which probably indicate an enriched oceanic island basalt-type mantle plume and a depleted mid-ocean ridge basalt-type spreading ridge.The results show that the influence of the Hainan mantle plume on younger volcanic activities(<13 Ma)is stronger than that on older ones(>13 Ma)at the same location in the Southeast Asian region.PCA was employed to verify the mantle-plume-ridge interaction model of volcanic activities beneath the expansion center of SCS and refute the hypothesis that the tension of SCS is triggered by the Hainan plume.This study reveals the efficiency and applicability of PCA in discussing mantle sources of volcanic activities;thus,PCA is a suitable research method for analyzing geochemical data.展开更多
基金Supported by the National Natural Science Foundation of China(No.U2244222).
文摘This study selects geochemical data of basalts from different seamounts in the Mid-Pacific Mountains province and conducts analyses of major and trace elements as well as Sr-Nd-Pb isotopes to explore the tectonic evolution,petrogenesis,and mantle-source magama characteristics of the Mid-Pacific Mountains.The basalts from the Mid-Pacific Mountains are predominantly alkali basalts,rich in alkalies,and changing in potassium.They exhibit geochemical features of ocean island basalts(OIB),with distinct fractionation between light and heavy rare-earth elements and a pronounced Ce negative anomaly(δ_(Ce)=0.16–1.10,average 0.84),along with enrichment in large ion lithophile elements(LILEs).The Mid-Pacific Mountains are intraplate ocean island basalts formed by mantle plume(hotspot)activity,originating mainly from an enriched mantle magma source region,and most of them have undergone low degree of partial melting and a certain degree of crystalline differentiation,with negligible contamination from oceanic crust materials.The Mid-Pacific Mountains exhibit ratios of^(87)Sr/^(86)Sr(i)(0.702733–0.704313,average 0.703452)and^(143)Nd/^(144)Nd(i)(0.512698–0.512996,average 0.512846)which are close to the HIMU mantle endmember,and ratios of 206Pb/204Pb(18.953–19.803),^(207)Pb/^(204)Pb(15.54–15.62)and^(208)Pb/^(204)Pb(38.813–39.514)which are close to the EMII mantle end-member.Combined with the isotopic geochemical characteristics in the West Pacific Seamounts province,the basalts from the Mid-Pacific Mountains were considered to represent a certain proportion of mixing mantle end-members between the HIMU and EMII,possibly formed by the mixing of the HIMU superplume in the South Pacific hotspot region with the EMII secondary mantle plume in the transition zone during their ascent.
基金supported by the National Natural Science Foundation of China(Grant No.42130312)。
文摘The complexity of the seismicity pattern for the subduction zone along the oceanic plate triggered the outer rise events and revealed cyclic tectonic deformation conditions along the plate subduction zones.The outer rise earthquakes have been observed along the Sunda arc,following the estimated rupture area of the 2005 M_(W)8.6 Nias earthquakes.Here,we used kinematic waveform inversion(KIWI)to obtain the source parameters of the 14 May 2021 M_(W)6.6 event off the west coast of northern Sumatra and to define the fault plane that triggered this outer rise event.The KIWI algorithm allows two types of seismic source to be configured:the moment tensor model to describe the type of shear with six moment tensor components and the Eikonal model for the rupture of pure double-couple sources.This method was chosen for its flexibility to be applied for different sources of seismicity and also for the automated full-moment tensor solution with real-time monitoring.We used full waveform traces from 8 broadband seismic stations within 1000 km epicentral distances sourced from the Incorporated Research Institutions for Seismology(IRIS-IDA)and Geofon GFZ seismic record databases.The initial origin time and hypocenter values are obtained from the IRIS-IDA.The synthetic seismograms used in the inversion process are based on the existing regional green function database model and were accessed from the KIWI Tools Green's Function Database.The obtained scalar seismic moment value is 1.18×10^(19)N·m,equivalent to a moment magnitude M_(W)6.6.The source parameters are 140°,44°,and−99°for the strike,dip,and rake values at a centroid depth of 10.2 km,indicating that this event is a normal fault earthquake that occurred in the outer rise area.The outer rise events with normal faults typically occur at the shallow part of the plate,with nodal-plane dips predominantly in the range of 30°-60°on the weak oceanic lithosphere due to hydrothermal alteration.The stress regime around the plate subduction zone varies both temporally and spatially due to the cyclic influences of megathrust earthquakes.Tensional outer rise earthquakes tend to occur after the megathrust events.The relative timing of these events is not known due to the viscous relaxation of the down going slab and poroelastic response in the trench slope region.The occurrence of the 14 May 2021 earthquake shows the seismicity in the outer rise region in the strongly coupled Sunda arc subduction zone due to elastic bending stress within the duration of the seismic cycle.
基金supported by the Second Tibetan Plateau Scientific Expedition and Research Program(STEP)(No.2019QZKK0208)the National Natural Science Foundation of China(Nos.42171148 and 42330512)the Key R&D Project from the Science and Technology Department of Tibet(No.XZ202501ZY0030).
文摘Nitrogen(N)and phosphorus(P)are essential nutrients and can significantly impact primary productivity of the ecosystem causing water environmental problems.However,their cycling mechanisms are not well understood in alpine mountains with climate change.Hence,94 samples of river water were collected from 2018 to 2020 in the headwaters of the Shule River Basin to assess the nutrients spatiotemporal distribution and combined ap-proach of water quality index to assess water quality and potential sources.The findings depict that high nutrient concentrations were found to coincide with snowmelt and glacial meltwater and rainfall recharge periods,while total flux peaked from June to September due to increased runoff.Notably,total nitrogen(TN)concentrations were significantly higher near the town,primarily attributed to the replenishment of nitrate(NO_(3)^(‒)-N)from live-stock manure.The high total P(TP)was near the glacier,which was attributed to the transportation of glacial sediments into the river,and pH was another critical factor.N was the primary nutrient limiting factor for the growth of phytoplankton in river water.Although the migration and transport of nutrients have altered with climate change,river water quality is good in alpine mountains based on an overall evaluation.These findings contribute to enriching nutrient datasets and highlight the importance of water resource management and water quality assessment in sensitive and fragile alpine mountains.
基金supported by National Key R&D grant from the Ministry of Science and Technology of China(Nos.2021YFA1601600,2023YFA1606200)National Science Foundation of China(Nos.12090062,12105008)the Major State Basic Research Development Program of China.
文摘We present the preparation and measurement of the radioactive isotope^(37)Ar,which was produced using thermal neutrons from a reactor,as a calibration source for liquid xenon time projection chambers.^(37)Ar is a low-energy calibration source with a half-life of 35.01 days,making it suitable for calibration in the low-energy region of liquid xenon dark-matter experiments.Radioactive isotope^(37)Ar was produced by irradiating ^(36)Ar with thermal neutrons.It was subsequently measured in a gaseous xenon time projection chamber(GXe TPC)to validate its radioactivity.Our results demonstrate that^(37)Ar is an effective and viable calibration source that offers precise calibration capabilities in the low-energy domain of xenon-based detectors.
基金support from the Natural Science Foundation of Jiangsu Province(Grant No.BK20240036)the National Natural Science Foundation of China(Grant Nos.U24A20515,22276099,and 22361162668)Guangxi Key Research and Development Program,China(Grant No.Guike AB24010074)。
文摘We conducted a field campaign to investigate the chemical composition,sources,and light absorption of submicron aerosols(PM_(1))from early 2022 in Nanjing,China.The average concentration of PM_(1) was 31μg m^(−3),organics(33%)constituted the largest fraction,followed by nitrate(30%),sulfate(18%),ammonium(15%),chloride(3%),and rBC(2%).Four organic aerosol(OA)subcomponents were identified,including two primary OA(POA)and two secondary OA(SOA).The less-oxidized SOA(LO-OOA)contributes the most to the total OA mass(59%).LO-OOA is tightly correlated with the tracer ion C_(2)H_(4)O_(2)^(+)from levoglucosan,and another aged biomass-burning derived species,K_(3)SO_(4)^(+),suggesting it was likely influenced by aged biomass-burning OA.Our study also revealed that fireworks during the Spring Festival have a detrimental impact on air quality,contributing to secondary formation and accumulation under static winter meteorological conditions,prolonging the pollution duration.Also,LO-OOA was found to have the strongest light-absorbing ability.Our results highlight that the light absorption of LO-OOA can mainly be attributed to the C_(x)H_(y)N^(+) family,increased with the double-bond equivalent value.The more-oxidized SOA(MO-OOA)exhibited a negligible light absorption and was strongly correlated with daytime photochemical processes,implying a light-bleaching effect.This study enhances our understanding of the regional contribution of biomass combustion and fireworks to PM_(1) pollution in Nanjing,a typical megacity in the Yangtze River Delta region,during winter,aiding in the development of strategies for long-term air quality improvement in the region.
基金supported by the National Natural Science Foundation of China(Nos.41905108 and 42130704).
文摘Carbonyl compounds play a pivotal role in the formation of secondary pollutants such as O_(3) and SOA,signifi-cantly impacting air quality and human health.This study extended the observation period compared to previous research,providing a long-term perspective on carbonyl compound variations and their environmental implica-tions.Atmospheric observations were conducted at Beijing(BJ)and Xianghe(XH)during the summer and winter months of 2018,2019,and 2023 to study the sources and impacts of carbonyl compounds in typical urban areas and peri‑urban areas.Notably,concentrations in the summer of 2023 increased compared to 2018 and 2019.The predominant carbonyl compounds—formaldehyde,acetaldehyde,and acetone—accounted for over 60%of the total.The mean values of OFP in BJ ranged from 18.55 to 58.61μg/m3,lower than those in XH(29.82 to 65.48μg/m3),with formaldehyde and acetaldehyde contributing over 80%of the total.SOAP exhibited a similar pattern,with values in XH(69.21 to 508.55μg/m3)significantly exceeding those in BJ(34.47 to 159.78μg/m3).The PMF model highlighted vehicle exhaust,secondary pollution,and biomass combustion as major sources of carbonyl compounds,emphasizing differences in source contributions between the two regions.This study’s com-parative analysis over different years and locations provides new insights into the dynamic changes in carbonyl compounds and their environmental importance.These results not only reinforce the importance of carbonyl compounds regulation but also offer a valuable reference for evaluating and refining emission control strategies during this period.
基金supported by the National Natural Science Foundation of China(No.41975156)and the Fundamental Research Funds for the Central Universities.
文摘Oxidative potential(OP)can be used as an indicator of the health risks of particulate matter in the air.To study the variation and sources of OP,we conducted an observation of PM_(2.5) in a megacity in southern China in winter and spring of 2021.The results show that the average concentration of PM_(2.5) decreased by 47%from winter to spring,while volume-normalized and mass-normalized OP(i.e.,OP_(v) and OP_(m))increased by 6%and 69%,respectively.It suggests that the decline of PM_(2.5) may not necessarily decrease the health risks and the intrinsic toxicity of PM_(2.5).Variations of OP_(v) and OP_(m) among different periods were related to the different source contributions and environmental conditions.The positive matrix factorization model was used to identify the major sources of OP_(v).OP_(v) was mainly contributed by biomass burning/industrial emissions(29%),soil/road dust(20%),secondary sulfate(14%),and coal combustion(13%)in winter.Different major sources were resolved to be secondary sulfate(36%),biological sources(21%),and marine vessels(20%)in spring,presenting the substantial contribution of biological sources.The analysis shows strong associations between OP_(v) and both live and dead bacteria,further confirming the important contribution of bioaerosols to the enhancement of OP.This study highlights the importance of understanding OP in ambient PM_(2.5) in terms of public health impact and provides a new insight into the biological contribution to OP.
文摘Annual haze in Northern Thailand has become increasingly severe,impacting health and the environment.How-ever,the sources of the haze remain poorly quantified due to limited observational data on aerosol molecular tracers.This study comprehensively investigates chemical composition of PM_(2.5),including both inorganic and organic compounds throughout haze and post-haze periods in 2019 at a rural site of Northern Thailand.Average PM_(2.5) concentrations during haze and post-haze period were 87±36 and 21±11μg/m^(3),respectively.Organic matter was the dominant contributor in PM_(2.5) mass,followed by water soluble inorganic ions and mineral dust.Molecular markers,including levoglucosan,dehydroabietic acid,and 4-nitrocatechol,and ions(Cl^(-),and K^(+)),were used to characterize low haze(PM_(2.5)<100μg/m^(3))and episodic haze(PM_(2.5)>100μg/m^(3)).Low haze is associated with local aerosols from agricultural waste burning,while episodic haze is linked to aged aerosols from mixed agricultural waste,softwood,and hardwood burning.Source apportionment incorporating these molecular markers in receptor modelling(Positive matrix factorization),identified three distinct biomass burning sources:mixed,local,and aged biomass burnings,contributing 31,19 and 13%of PM_(2.5) during haze period.During post-haze period,contributions shifted,with local biomass burning(32%)comparable to secondary sulfate(34%)and mixed dust and traffic sources(26%).These findings demonstrate that both regional and local sources con-tribute to severe haze,highlighting the need for integrated policies for cross-border cooperation as well as stricter regulations to reduce biomass burning in Northern Thailand and Southeast Asia.
基金supported by the Quantum Science and Technology-National Science and Technology Major Project (Grant No.2024ZD0302502 for WZ)the National Natural Science Foundation of China(Grant No.92365210 for WZ)+1 种基金Tsinghua Initiative Scientific Research Program (for WZ)the project of Tsinghua University-Zhuhai Huafa Industrial Share Company Joint Institute for Architecture Optoelectronic Technologies (JIAOT,for YH)。
文摘To fully utilize the resources provided by optical fiber networks,a cross-band quantum light source generating photon pairs,where one photon in a pair is at C band and the other is at O band,is proposed in this work.This source is based on spontaneous four-wave mixing(SFWM)in a piece of shallow-ridge silicon waveguide.Theoretical analysis shows that the waveguide dispersion could be tailored by adjusting the ridge width,enabling broadband photon pair generation by SFWM across C band and O band.The spontaneous Raman scattering(SpRS)in silicon waveguides is also investigated experimentally.It shows that there are two regions in the spectrum of generated photons from SpRS,which could be used to achieve cross-band photon pair generation.A chip of shallow-ridge silicon waveguide samples with different ridge widths has been fabricated,through which cross-band photon pair generation is demonstrated experimentally.The experimental results show that the source can be achieved using dispersion-optimized shallow-ridge silicon waveguides.This cross-band quantum light source provides a way to develop new fiber-based quantum communication functions utilizing both C band and O band and extends applications of quantum networks.
基金the National Natural Science Foundation of China(Nos.91858206,41876040)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA22050101,XDB42020302)+1 种基金the Taishan Scholars Program of Shandong Province(No.tsqn201909157),Senior User Project of R/V Kexue(No.KEXUE2018G09)the Laboratory for Marine Geology,Qingdao National Laboratory for Marine Science and Technology(No.MGQNLMTD201806)。
文摘The alkaline oceanic island basalts(OIBs)with under-saturated SiO2 and high contents of CaO and alkaline are usually attributed to mantle sources different from typical tholeiitic OIBs.Based on the results of high pressure and temperature experiment study,the genesis of silica under-saturated alkaline basaltic melts could be explained by the role of CO2,thus,the genetic relationship of alkaline basalts with CO2 has become a topic of relevance because it is closely related to the deep carbon cycle.The Magellan Seamount chain in the West Pacific Seamount Province has wide distribution of alkali basalts.For the first time,we collected alkaline basalt samples from the Kocebu Seamount of the Magellan Seamount chain and found that magmatic apatites widely occur in the less evolved volcanic rock samples,and the high contents of phosphorus should be a feature of the alkaline OIBs of the Magellan Seamounts.Compared with typical OIBs,these alkaline volcanic rocks have higher CaO and P2O5,lower SiO2 content,negative anomaly of high field strength elements(HFSEs),more distinctly negative anomaly of potassium(K)and the ubiquity of titanaugite,indicating a CO2-rich mantle source.Based on the relatively high K2O and TiO2 contents and La/Yb ratio and low MgO content of these alkaline rocks,we suggest that the volcanic rocks of the Magellan Seamounts are originated from carbonated eclogites derived possibly from ancient subducted altered oceanic crust.
基金theNationalClimbingProgram(95 Pre .393 1 2 )andMLMRStrategicKeyProgram (95 0 110 3)
文摘Geological setting\;Jinding superlarge Pb\|Zn deposit lies in the Lanping basin between the Lancangjiang fracture zone and the Jinshajiang\|Ailaoshan fracture zone. The Lanping basin is a Meso\|Cenozoic rifting basin whose basement consists of the Paleozoic strata. Mesozoic paralic and continental sediments with a thickness of about 20000m deposited in the basin. In the Paleocene, gypsum\|salt\|bearing strata with a thickness of more than 1000m accumulated. In the Cenozoic, collision of the Indian plate with the Eurasian plate resulted in strong folding and napping and subsequent extensions in the Oligocene and Pliocene. The extensions were responsible for alkaline magmatic intrusion in the centre and alkaline magmatic extrusion in the east.Faulting is well developed. N\|S\|trending Bijiang fault with a length of 120km links with the Jinshajiang fracture zone in the north and with the Lancangjiang fracture zone in the south, controlling on the Cenozoic Lanping rifting basin and acting as passage\|way for ore fluids.
基金supported by the Major Program of the National Natural Science Foundation of China(41790453)the Natural Science Foundation of Jilin Province(20170101001JC)+1 种基金the National Natural Science Foundation of China(41472304)the National Science and Technology Major Project of the Ministry of Science and Technology of China(2016ZX05026-004-001)。
文摘Research on the distribution of mantle CO_(2)should involve comprehensive analysis from CO_(2)source to accumulation.The crust-mantle pathway system is the key controlling factor of the distribution of mantle CO_(2),but has received little attention.The pathway system and controlling factors of CO_(2)distribution in the Bohai Sea are analyzed using data on fault styles and information on the mantle and lithosphere.The relation between volcanic rocks and the distribution of mantle CO_(2)is reassessed using age data for CO_(2)accumulations.The distribution of mantle CO_(2)is controlled by uplift of the asthenosphere and upper mantle,magma conduits in the mantle and fault systems in the crust.Uplifted regions of the asthenosphere are accumulation areas for CO_(2).The area with uplift of the Moho exhibits accumulation of mantle CO_(2)at depth.CO_(2)was mainly derived from vertical migration through the upper mantle and lower crust.The fault style in the upper crust controls the distance of horizontal migration and the locations of CO_(2)concentrations.The distribution of mantle CO_(2)and volcanic rocks are not the same,but both probably followed the same pathways sometimes.Mantle CO_(2)in the Bohai Sea is concentrated in the Bozhong sag and the surrounding area,particularly in a trap that formed before 5.1 Ma and is connected to crustal faults(the Bozhang faults)and lithospheric faults(the Tanlu faults).
文摘Based on the REE geochemistry data from the Baimazhai nickel deposit, Yunnan Province, the authors modeled the composition of the mantle source region by way of petrological mixing calculation, and further discussed the genesis of this type of rocks. Both element geochemistry data and mixing calculation showed that lamprophyres in the Baimazhai nickel deposit were derived from a metasomatism-enrichment mantle and the fluids resulted from dehydration of a subducted slab which is comprised of ALK-, LREE- and incompatible element-rich sediments.
文摘Mafic rocks comprising tholeiitic pillow basalt, dolerite and minor gabbro form the basal stratigraphic unit in the ca. 2.8 to 2.6 Ga Geita Greenstone Belt situated in the NW Tanzania Craton. They outcrop mainly along the southern margin of the belt, and are at least 50 million years older than the supracrustal assemblages against which they have been juxtaposed. Geochemical analyses indicate that parts of the assemblage approach high Mg-tholeiite （more than 8 wt.% MgO）. This suite of samples has a restricted compositional range suggesting derivation from a chemically homogenous reservoir. Trace element modeling suggests that the mafic rocks were derived by partial melting within the spinel peridotite field from a source rock with a primitive mantle composition. That is, trace elements maintain primitive mantle ratios （Zr/Hf = 32-35, Ti/Zr - 107-147）, producing flat REE and HFSE profles [（La/Yb）pm = 0.9 -1.3], with abundances of 3-10 times primitive mantle and with minor negative anomalies of Nb [（Nb/ La）pm - 0.6-0.8] and Th [（Th/La）pm = 0.6-0.9]. Initial isotope compositions （εNd） range from 1.6 to 2.9 at 2.8 Ga and plot below the depleted mantle line suggesting derivation from a more enriched source compared to present day MORB mantle. The trace element composition and Nd isotopic ratios are similar to the mafic rocks outcropping -50 km south. The mafic rocks outcropping in the Geita area were erupted through oceanic crust over a short time period, between -2830 and-2820 Ma; are compositionally homogenous, contain little to no associated terrigenous sediments, and their trace element composition and short emplacement time resemble oceanic plateau basalts. They have been interpreted to be derived from a plume head with a primitive mantle composition.
文摘This paper discusses the discrimination principles. deduction and methods for probing into the source composition of mantle-derived magma. The magmatophile (incompatible) source elements are not all optimal tracers for mantle source composition. The ratios of two strong magmatophile elements (D<1) or the ratios of two trace elements with the same D value are not controlled by the formation mode and evolution degree of a magma, but maintain the characteristics of their composition in mantle source region prior to the magma formation. The ratios are related to different mantle-crust structures and dynamics. The mantle source composition of the Emeishan Basalt series is similar to that of the South Atlantic Rio Grande Rise-Walvis Ridge Basalts and Brazil continental-margin basalts. This may indicate that these basalt series might have similar source regions and tectonic environments.
基金part of H.J.'s MSc thesis project (PIPGSTS-16-16)conducted at the Petroleum Institute,UAE.
文摘Several types of felsic granitoid rocks have been recognized, intrusive in both the mantle and the crustal sequence of the Semail ophiolite. Several models have been proposed for the source of this suite of tonalites, granodiorites, trondhjemites intrusions, however their genesis is still not clearly understood.The sampled Dadnah tonalites that intruded in the mantle section of the Semail ophiolite display arctype geochemical characteristics, are high siliceous, low-potassic, metaluminous to weakly peraluminous, enriched in LILE, show positive peaks for Ba, Pb, Eu, negative troughs for U, Ti and occur with low δ^(18)O_(H_2 O), moderate ε_(Sr) and negative eNd values. They have crystallized at temperatures that range from～550 ℃ to ～720 ℃ and pressure ranging from 4.4 kbar to 6.5 kbar. The isotopic ages from our tonalite samples range between 98.6 Ma and 94.9 Ma, slightly older and overlapping with the age of the metamorphic sole. Our field observations, mineralogical, petrological, geochemical, isotopic and melt inclusion data suggest that the Dadnah tonalites formed by partial melting(～10%-15% continuous or ～12% batch partial melting), accumulation of plagioclase, fractional crystallization(～55%-57%), and interaction with their host harzburgites. These tonalites were the end result of partial melting and subsequent contamination and mixing of ～4% oceanic sediments with ～96% oceanic lithosphere from the subducted slab. This MORB-type slab melt composed from ～97% recycled oceanic crust and ～3% of the overlying mantle.We suggest that a possible protolith for these tonalites was the basaltic lavas from the subducted oceanic slab that melted during the initial stages of the supra-subduction zone(SSZ), which was forming synchronously to the spreading ridge axis. The tonalite melts mildly modified due to low degree of mixing and interaction with the overlying lithospheric mantle. Subsequently, the Dadnah tonalites emplaced at the upper part of the mantle sequence of the Semail ophiolite and are geochemically distinct from the other mantle intrusive felsic granitoids to the south.
基金the National Natural Science Foundation of China （No. 40272088）.
文摘The Zhangjiakou-Xuanhua area is a mineral resource-concentrated area for gold-silver polymetallic ore deposits. The temporal and spatial distribution and origin of mineral resources have been argued for a long time. Based on the comprehensive studies of geochronology and sulfur, lead, oxygen, carbon and noble gas isotopes, it is considered that the temporal and spatial distribution of mineral resources in this area is obviously controlled by the Zhangjiakou-Xuanhua mantle branch structure, as is reflected by the occurrence of gold deposits in the inner parts and of Ag-Pb-Zn polymetallic ore deposits in the outer parts. The mineralization took place mainly during the Yanshanian period. Ore-forming materials came largely from the deep interior of the Earth, and hydrothermal fluids were derived predominantly from Yanshanian magmatism.
基金supported by the National Natural Science Foundation of China (Grant No. 40872137)Natural Science Foundation of Hebei Province (GrantNo.D2007000751)
文摘This study was conducted following research on metallogenesis in the Zhangjiajie-Xuanhua and East Hebei mantle branch structure zones. The Fuping mantle branch structure zone is one where Au, Cu and Ag poly-metallic ore resources are concentrated in North Hebei. However, there has existed a long-standing controversy on the temporal-spatial distribution of ore resources and their ore-forming material sources. In terms of age dating and the comprehensive analysis of S, Pb, O, C and Si isotopes, it is considered that the temporal-spatial distribution of ore resources in this mantle branch structure zone is obviously controlled by the Fuping mantle branch structure. In space there is developed such a metallogenic pattern as to be Ag, Pb and Zn polymetallic ore deposits with gold appearing inside and copper appearing outside. Metallogenesis is dated mainly at Yanshanian, the ore-forming materials were derived predominantly from the deep interior of the Earth, and ore-forming fluids were derived largely from Yanshanian magmatism.
基金the Shandong Provincial Natural Science Foundation,China(Nos.ZR2017PD002 and ZR2019BD010)the Open Fund of the Key Laboratory of Marine Geology and Environment,Chinese Academy of Sciences(Nos.MGE2019KG05 and MG E2021KG01)the Fundamental Research Funds for the Central Universities(No.202051009)。
文摘The composition of mantle-derived basalts reflects the nature of their mantle source regions,which constrain magma generation and composition.Here we present a new whole rock major and trace elements and phenocryst composition of the basaltic lava in the central Mariana Trough.These data provide insights into the mantle source characteristics affected by subduction components.The rocks range from basalts to basaltic andesites,which have high subduction-mobile element contents(e.g.,K,U,Th,LREE)related to N-MORB.The calculated temperature and depth of magma generation are about 1300℃and 30 km,respectively.Although the results above suggest that the addition of hydrous fluid and/or a melt derived from a slab decreases the temperature of mantle partial melting and mildly modifies the composition of a mantle source,the mantle source lithology from which primary magma is generated remains to be peridotite.
基金Supported by the State Key Laboratory of Marine Environmental Science Visiting Fellowship(No.MELRS2233)the State Key Laboratory of Marine Geology,Tongji University(No.MGK202302)+4 种基金the Innovation Group Project of Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)(No.311021003)the Zhujiang Talent Project Foundation of Guangdong Province(No.2017ZT07Z066)the Fundamental Research Funds for the Central Universities,Sun Yat-sen University(Nos.22qntd2101,2021qntd23)the Major Projects of the National Natural Science Foundation of China(Nos.41790465,41590863)the National Natural Science Foundation of China(Nos.42102333,41806077,41904045)。
文摘Principal component analysis(PCA)was employed to determine the implications of geochemical and isotopic data from Cenozoic volcanic activities in the Southeast Asian region,including China(South China Sea(SCS),Hainan Island,Fujian-Zhejiang coast,Taiwan Island),and parts of Vietnam and Thailand.We analyzed 15 trace element indicators and 5 isotopic indicators for 623 volcanic rock samples collected from the study region.Two principal components(PCs)were extracted by PCA based on the trace elements and Sr-Nd-Pb isotopic ratios,which probably indicate an enriched oceanic island basalt-type mantle plume and a depleted mid-ocean ridge basalt-type spreading ridge.The results show that the influence of the Hainan mantle plume on younger volcanic activities(<13 Ma)is stronger than that on older ones(>13 Ma)at the same location in the Southeast Asian region.PCA was employed to verify the mantle-plume-ridge interaction model of volcanic activities beneath the expansion center of SCS and refute the hypothesis that the tension of SCS is triggered by the Hainan plume.This study reveals the efficiency and applicability of PCA in discussing mantle sources of volcanic activities;thus,PCA is a suitable research method for analyzing geochemical data.
