The method of LA-MC-ICP-MS has become one choice for the analysis of many isotopic systems due to its relatively low cost,high analysis speed,high spatial resolution,and low matrix effect.However,there are still many ...The method of LA-MC-ICP-MS has become one choice for the analysis of many isotopic systems due to its relatively low cost,high analysis speed,high spatial resolution,and low matrix effect.However,there are still many challenges in the accuracy,precision,and spatial resolution of in situ isotopic composition determination by LA-MC-ICP-MS,which mainly include:(1)how to improve instrument sensitivity,further improve the spatial resolution,and achieve simultaneous determination of isotopes,multiple isotopes,or isotopes with trace elements in low-content samples?(2)how to deduct and correct interference to improve the accuracy of isotopic determination?(3)how to correct isotope fractionation?(4)how to reduce the matrix effect of isotopes?how to develop matrix-matched reference materials?and(5)how to achieve non-matrix-matched correction of isotopes?The high-sensitivity cone combinations,gas mixture,shield torch,and reasonable detector array can be applied to improve the elemental sensitivity.The interferences include the background interference and the interferences from the matrix elements(the isobaric interference,the polyatomic interference,and doubly charged ions interference).To reduce or even eliminate the interference,commonly used methods including interference elimination,background correction,and interference correction by evaluating with an interference-free isotope.Isotopic fractionation correction mainly involves external standard calibration and internal and pseudo-internal standard normalization.For non-matrix matched calibration,many methods can be applied,such as the femtosecond laser,line scan,low laser energy,wet plasma condition,optical setup below the sample surface,and matching the intensity of the sample and standard.In this review,we systematically summarized the above challenges and solutions to promote the study and application of LA-MC-ICP-MS in isotopic determination.展开更多
Zircon is a key accessary mineral for metamorphic geochronology and geochemical tracing,but it has been a challenge to interpret its complex chemical zoning and age record acquired during multiple episodes of anatecti...Zircon is a key accessary mineral for metamorphic geochronology and geochemical tracing,but it has been a challenge to interpret its complex chemical zoning and age record acquired during multiple episodes of anatectic metamorphism in collisional orogens.This is illustrated by a combined study of petrography,phase equilibrium modeling and metamorphic P-T-t determination for granulites from the Bohemian Massif in the Variscan Orogen.These rocks record multiple episodes of zircon growth during anatectic metamorphism.They started from the compressional heating for prograde metamorphism to high-pressure(HP)to ultrahigh-pressure(UHP)eclogite facies with low degrees of partial melting.Afterwards,they underwent a decompressional stage from UHP eclogite facies to HP granulite facies for dehydration melting.These were followed by a further decompressional stage either to kyanite granulite facies or to sillimanite granulite facies at ultrahigh-temperature(UHT)conditions.Episodes of zircon growth are linked to specific metamorphic conditions for peritectic reactions on the basis of zoning patterns,trace element signatures,index mineral inclusions in dated domains and textural relationships to coexisting minerals.The results indicate that relict zircon domains are preserved even at UHT granulite facies conditions.A few zircon domains in the kyanite granulite grew during the prograde to peak UHP metamorphism,possibly corresponding to consumption of biotite and plagioclase but growth of garnet.During the decompressional exhumation to the HP granulite-facies,relict or prograde zircon domains were mostly dissolved into anatectic melts produced by muscovite breakdown.Most zircon grains grew during this transition to the HP granulite-facies in the kyanite granulite and are chemically related to continuous growth of garnet,whereas abundant zircon grains grew subsequently at the UHT granulite facies in the sillimanite granulite and are chemically related to garnet breakdown reactions.Another peak of zircon growth occurred at the final crystallization of anatectic melts in the sillimanite granulite rather than in the kyanite granulite,and these zircon grains mostly show oscillatory zoning,low HREE+Y contents and significantly negative Eu anomalies.In terms of the inference for protolith nature,it appears that zircon in metasedimentary rocks can grow at a short timescale in different stages of anatectic metamorphism,and its dissolution and growth are mainly dictated by anatectic conditions and extent,the property of peritectic reactions,and the stability of Ti-rich minerals.展开更多
Oxide interference correction plays a vital role in the accurate determination of trace element compositions of geological samples by inductively coupled plasma-mass spectrometry(ICP-MS).In this study,we found that th...Oxide interference correction plays a vital role in the accurate determination of trace element compositions of geological samples by inductively coupled plasma-mass spectrometry(ICP-MS).In this study,we found that the oxide production is mainly controlled by the gas flow of the ICP-MS and a constant oxide correction factor(OCF)can be measured during a routine analysis.Thus,we can obtain the oxide production by just investigating the gas flow for a fixed ICP-MS system with monitoring of OCF.Si,Ba and LREE oxide interferences on the Sc,Eu and Gd of four geological standard samples GSP-2,JP-1,GBW03112 and GBW03113 were corrected by such method and the results were in good agreement with the recommended values.Therefore,the present study provides a simple and fast correction method for the oxide interferences of the geological samples during the routine analyses.Furthermore,a Microsoft Excel spreadsheet template integrating the correction equations was developed in an in-house software(ICPMSData Cal)for effective calibration.展开更多
Isotope plays an important role in both tracing and dating in earth science, especially 87Rb-86 Sr system. With the development of earth science, whole-rock analysis can't sufficiently meet the requirements for sc...Isotope plays an important role in both tracing and dating in earth science, especially 87Rb-86 Sr system. With the development of earth science, whole-rock analysis can't sufficiently meet the requirements for scientific research and the micro-analysis becomes more and more significant. Laser ablation multi-collector inductively-coupled plasma mass-spectrometry(LA-MC-ICP-MS) has been extensively applied in micro-zone analysis due to its low sample-consumption, high accuracy, in situ and low requirements on matrix, but it is still difficult to accurately measure Sr isotope compositions especially for the samples with high Rb/Sr ratios and low Sr contents as it is restricted by severe quality discrimination and various types of mass spectrum interferences. Consequently, thermal ionization mass-spectrometry(TIMS), as the most accurate and precise method to analyze isotopic ratios, is still the most popular method of analyzing Sr ratios, especially for the samples with low Sr contents. This paper makes a systematic review on the high-precision Sr isotope analyses of low-Sr geological samples, including the micro-sampling technique, ultra-low procedural blank chemical method and TIMS measurement technique. The combination of ultra-low procedural blank and TIMS can be used to perform high-precision micro-analysis of the samples with ng magnitude, which will be undoubtedly an important direction for Rb-Sr geochronology, geochemistry and environmental studies.展开更多
This work evaluates the use of femtosecond laser ablation multiple collector inductively coupled plasma mass spectrometry(fs-LA-MC-ICP-MS) for Zr isotopic analysis in zircons. The mass fractionation caused by instrume...This work evaluates the use of femtosecond laser ablation multiple collector inductively coupled plasma mass spectrometry(fs-LA-MC-ICP-MS) for Zr isotopic analysis in zircons. The mass fractionation caused by instrumental mass discrimination was corrected by a combination of internal correction using Sr as an internal standard(coming from a NIST SRM 987 standard solution) and external correction using a matrix-matched standard. Several important instrument parameters were investigated, such as the effect of the addition of N;and "wet" plasma condition, the mass fractionation behaviors between Zr isotopes and Sr isotopes, the position effect in laser ablation cell and the effect of laser ablation parameters(laser spot size and energy density). The Zr isotope compositions of seven zircons(GJ-1, 91500, Ple?ovice, Rak-17, Paki, Aus and Mala) were determined by the developed fs-LAMC-ICP-MS and thermal ionization mass spectrometry(TIMS). Our fs-LA-MC-ICP-MS results for Zr isotope compositions agreed with TIMS analyses within analytical uncertainties, indicating the presented method is a suitable tool to resolve isotopic zoning in natural zircons. The results also suggest that GJ-1, 91500, Ple?ovice, Paki, Aus and Mala had the homogenous Zr isotope composition and could be considered as the potential candidates for the Zr isotope analysis in zircons, except Rak-17 which presented the large Zr isotope variation.展开更多
We proposed a new laser analytical mode,which used the high-frequency laser ablation to deliberately obtain the peak-shape signal profile,combined with the linear regression calibration(LRC)method to calculate element...We proposed a new laser analytical mode,which used the high-frequency laser ablation to deliberately obtain the peak-shape signal profile,combined with the linear regression calibration(LRC)method to calculate elemental or isotopic ratios.In order to assess the performance of the new laser analytical mode for the application in the field of earth science,we systematically investigated the elemental quantitative analysis with high spatial resolution(10μm),rapid U-Pb dating in zircons and accurate Sr-Hf isotope analysis in geological samples.The new high-frequency laser analysis technology(20 Hz,100 pulses)reduced the limit of detection(LOD)of 25 elements to 0.005-0.16μg g^(-1) with crater diameters of 10μm,which are significantly lower(decrease to 2-20%)than previous researches.The quantitative analysis of five silicate glass reference materials showed that the precision and accuracy of the 25 trace elements(with the concentration ranging from 0.17 to 683μg g^(-1))were better than 16% and 15%,respectively.The new methods raised the analytical throughput of zircon U-Pb dating,Sr isotope ratios and Hf isotope ratios to 250 analyses per hour,144 analyses per hour and 120 analyses per hour in theory,while the analytical accuracy and precision were not affected.The detailed investigations showed that the proposed new laser analytical mode has good application effects in the field of earth sciences.展开更多
Bastn?site is widespread in alkali granite, carbonatite and REE ore deposits. The U-Th-Pb ages of bastn?site can constrain the mineralization age. Currently, the lack of suitable in situ analysis reference material is...Bastn?site is widespread in alkali granite, carbonatite and REE ore deposits. The U-Th-Pb ages of bastn?site can constrain the mineralization age. Currently, the lack of suitable in situ analysis reference material is the major obstacle of bastn?site U-Th-Pb geochronology. In this study, the matrix effects of U-Pb and Th-Pb age determination in bastn?site using glass NIST 610 as the external calibration reference were evaluated with the 193-nm excimer LA-ICP-MS analysis in normal and additional gases laser ablation modes. The obtained U-Th-Pb ages of bastn?site were approximately 7–11% lower than their reference values in the normal analytical mode(without additional gas). Fortunately, the determined systematic age biases in UTh-Pb dating were significantly reduced(less than 1–2%) with the addition of water vapor within the ablation chamber. This reduction may be attributed to the observed significant suppression of206 Pb/238 U and208 Pb/232 Th downhole fractionation in both NIST 610 glass and bastn?site by introducing a small quantity of water vapor in the ablation chamber. In addition, the obtained206 Pb/238 U and208 Pb/232 Th ages of bastn?site K-9, LZ1384, and MAD809 showed great consistency with their corresponding recommended values. The obtained results show that accurate and precise U-Th-Pb ages of bastn?site can be simultaneously obtained by using glass NIST 610 as the primary calibration standard in 193-nm LA-ICP-MS with the water vapor-assisted method. This simple and effective water vapor-assisted non-matrix-matched laser ablation method helps to promote the geological application of bastn?site U-Th-Pb geochronology.展开更多
The Permian basalts in the Central Asian Orogenic Belt(CAOB)are crucial for constraining the closure of the Paleo-Asian Ocean.However,the origin of these basalts is still under discussion.Here,we present comprehensive...The Permian basalts in the Central Asian Orogenic Belt(CAOB)are crucial for constraining the closure of the Paleo-Asian Ocean.However,the origin of these basalts is still under discussion.Here,we present comprehensive bulk-rock geochemical,Sr-Nd-Pb-Hf isotopic,and zircon U-Pb-Lu-Hf isotopic data of the Liuyuan basalts and coexisting gabbros,which are located in the Beishan Orogen in the southern CAOB,to constrain their emplacement setting and tectonic implications.Our new gabbro ages of ca.288–294 Ma are interpreted to represent the formation time of the Liuyuan basaltic belt.The Liuyuan basalts show MORB-like rare earth element(REE)patterns and bulk-rockε_(Hf)(t)andε_(Nd)(t)values of 11.0–15.4 and 4.6–9.2,respectively,suggesting an origination mainly from a depleted mantle source.However,positive Pb anomalies,Nb-Ta depletions,and high Th/Yb ratios as well as evolved Sr-Nd-Pb-Hf isotopic compositions of some samples indicate variable continental crustal contribution.According to the covariation of Pb anomalies(Pb^(*)=2×Pb_(N)/(Ce_(N)+Pr_(N)))with Sr-Nd-Pb-Hf isotopic compositions,we speculate that parent magma of the Liuyuan basalt was contaminated by continental crustal materials during the eruption rather than having been generated from an enriched mantle source.As revealed by mixing modelling,the Liuyuan basaltic magmas would require a minor(<10%)upper continental crustal assimilation to explain the enriched trace elemental and radiogenic Sr-Nd-Pb-Hf isotopic signatures.Consequently,the Liuyuan basaltic belt is believed to have been generated in a continental extensional environment instead of an oceanic setting and does not constitute a Permian ophiolitic suture zone as previously suggested,since the Paleo-Asian Ocean was already closed in the southern Beishan Orogen in the Early Permian.展开更多
The successful return of lunar soil samples from the northern Oceanus Procellarum by the Chang’E 5(CE-5) mission has provided unprecedented ground-truth information for the previously unexplored region of the Moon. I...The successful return of lunar soil samples from the northern Oceanus Procellarum by the Chang’E 5(CE-5) mission has provided unprecedented ground-truth information for the previously unexplored region of the Moon. In particular, the particle size and mineral constituents of the CE-5 soil samples are of critical importance to interpret remote sensing data. With a Raman-based particle analysis system, we show that the particle size properties and mineral constituents of the CE-5 soil can be simultaneously determined with a small sample size(ca. 30 μg). The CE-5 sample scooped from the lunar surface has an overall small size between 0.4 μm and 73.9 μm(mean=3.5 μm), and mainly consists of pyroxene(39.4%), plagioclase(37.5%), olivine(9.8%), Fe-Ti oxides(1.9%), glass(8.3%) and other minor or trace phases. The results are consistent with previous analyses with larger sample sizes. In addition to minimum sample consumption, this method requires very little sample preparation, and can rapidly build a large database with each particle precisely traceable. Therefore, this novel technique is particularly suitable for the analysis of future returned soil samples from extraterrestrial bodies.展开更多
基金funded by the National Key R&D Program of China (No. 2019YFA0708400)the National Natural Science Foundation of China (No. 41927803)+2 种基金the MOST (Ministry of Science and Technology) Special Fund from the State Key Laboratory of Geological Processes and Mineral Resources (No. MSFGPMR01)the Natural Science Foundation of Hubei Province (No. 2020CFA045)the Fundamental Research Funds for the Central Universities,China University of Geosciences (Wuhan).
文摘The method of LA-MC-ICP-MS has become one choice for the analysis of many isotopic systems due to its relatively low cost,high analysis speed,high spatial resolution,and low matrix effect.However,there are still many challenges in the accuracy,precision,and spatial resolution of in situ isotopic composition determination by LA-MC-ICP-MS,which mainly include:(1)how to improve instrument sensitivity,further improve the spatial resolution,and achieve simultaneous determination of isotopes,multiple isotopes,or isotopes with trace elements in low-content samples?(2)how to deduct and correct interference to improve the accuracy of isotopic determination?(3)how to correct isotope fractionation?(4)how to reduce the matrix effect of isotopes?how to develop matrix-matched reference materials?and(5)how to achieve non-matrix-matched correction of isotopes?The high-sensitivity cone combinations,gas mixture,shield torch,and reasonable detector array can be applied to improve the elemental sensitivity.The interferences include the background interference and the interferences from the matrix elements(the isobaric interference,the polyatomic interference,and doubly charged ions interference).To reduce or even eliminate the interference,commonly used methods including interference elimination,background correction,and interference correction by evaluating with an interference-free isotope.Isotopic fractionation correction mainly involves external standard calibration and internal and pseudo-internal standard normalization.For non-matrix matched calibration,many methods can be applied,such as the femtosecond laser,line scan,low laser energy,wet plasma condition,optical setup below the sample surface,and matching the intensity of the sample and standard.In this review,we systematically summarized the above challenges and solutions to promote the study and application of LA-MC-ICP-MS in isotopic determination.
基金supported by the Natural Science Foundation of China(Nos.41673030,41590624)the Strategy Guide Project B of the Chinese Academy of Sciences(No.XDB18020303)+1 种基金the Youth Innovation Promotion Association of CAS(No.2013283)the Fundamental Research Programs for the Central Universities。
文摘Zircon is a key accessary mineral for metamorphic geochronology and geochemical tracing,but it has been a challenge to interpret its complex chemical zoning and age record acquired during multiple episodes of anatectic metamorphism in collisional orogens.This is illustrated by a combined study of petrography,phase equilibrium modeling and metamorphic P-T-t determination for granulites from the Bohemian Massif in the Variscan Orogen.These rocks record multiple episodes of zircon growth during anatectic metamorphism.They started from the compressional heating for prograde metamorphism to high-pressure(HP)to ultrahigh-pressure(UHP)eclogite facies with low degrees of partial melting.Afterwards,they underwent a decompressional stage from UHP eclogite facies to HP granulite facies for dehydration melting.These were followed by a further decompressional stage either to kyanite granulite facies or to sillimanite granulite facies at ultrahigh-temperature(UHT)conditions.Episodes of zircon growth are linked to specific metamorphic conditions for peritectic reactions on the basis of zoning patterns,trace element signatures,index mineral inclusions in dated domains and textural relationships to coexisting minerals.The results indicate that relict zircon domains are preserved even at UHT granulite facies conditions.A few zircon domains in the kyanite granulite grew during the prograde to peak UHP metamorphism,possibly corresponding to consumption of biotite and plagioclase but growth of garnet.During the decompressional exhumation to the HP granulite-facies,relict or prograde zircon domains were mostly dissolved into anatectic melts produced by muscovite breakdown.Most zircon grains grew during this transition to the HP granulite-facies in the kyanite granulite and are chemically related to continuous growth of garnet,whereas abundant zircon grains grew subsequently at the UHT granulite facies in the sillimanite granulite and are chemically related to garnet breakdown reactions.Another peak of zircon growth occurred at the final crystallization of anatectic melts in the sillimanite granulite rather than in the kyanite granulite,and these zircon grains mostly show oscillatory zoning,low HREE+Y contents and significantly negative Eu anomalies.In terms of the inference for protolith nature,it appears that zircon in metasedimentary rocks can grow at a short timescale in different stages of anatectic metamorphism,and its dissolution and growth are mainly dictated by anatectic conditions and extent,the property of peritectic reactions,and the stability of Ti-rich minerals.
基金supported by the National Natural Science Foundation of China(42241156)the Pre-research Project on Civil Aerospace Technologies funded by China National Space Adiministration(D020205)the Outstanding Youth Team Project of China University of Geosciences,Wuhan(G1323523042)to Zaicong Wang。
基金supported by the National Natural Science Foundation of China (Nos. 41473031,41530211)the MOST Special Fund from the State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences,Wuhan (No. MSFGPMR01)
文摘Oxide interference correction plays a vital role in the accurate determination of trace element compositions of geological samples by inductively coupled plasma-mass spectrometry(ICP-MS).In this study,we found that the oxide production is mainly controlled by the gas flow of the ICP-MS and a constant oxide correction factor(OCF)can be measured during a routine analysis.Thus,we can obtain the oxide production by just investigating the gas flow for a fixed ICP-MS system with monitoring of OCF.Si,Ba and LREE oxide interferences on the Sc,Eu and Gd of four geological standard samples GSP-2,JP-1,GBW03112 and GBW03113 were corrected by such method and the results were in good agreement with the recommended values.Therefore,the present study provides a simple and fast correction method for the oxide interferences of the geological samples during the routine analyses.Furthermore,a Microsoft Excel spreadsheet template integrating the correction equations was developed in an in-house software(ICPMSData Cal)for effective calibration.
基金supported by National Natural Science Foundation of China (Nos. 90914007, 41125013)111 Plan (B07039)+1 种基金special fund of Ministry of Science and Technology,State Key Laboratory of Geological Processes and Mineral Resources (No. MSFGPMR201404)fund of Central University Fundamental Research (No. CUG090105)
文摘Isotope plays an important role in both tracing and dating in earth science, especially 87Rb-86 Sr system. With the development of earth science, whole-rock analysis can't sufficiently meet the requirements for scientific research and the micro-analysis becomes more and more significant. Laser ablation multi-collector inductively-coupled plasma mass-spectrometry(LA-MC-ICP-MS) has been extensively applied in micro-zone analysis due to its low sample-consumption, high accuracy, in situ and low requirements on matrix, but it is still difficult to accurately measure Sr isotope compositions especially for the samples with high Rb/Sr ratios and low Sr contents as it is restricted by severe quality discrimination and various types of mass spectrum interferences. Consequently, thermal ionization mass-spectrometry(TIMS), as the most accurate and precise method to analyze isotopic ratios, is still the most popular method of analyzing Sr ratios, especially for the samples with low Sr contents. This paper makes a systematic review on the high-precision Sr isotope analyses of low-Sr geological samples, including the micro-sampling technique, ultra-low procedural blank chemical method and TIMS measurement technique. The combination of ultra-low procedural blank and TIMS can be used to perform high-precision micro-analysis of the samples with ng magnitude, which will be undoubtedly an important direction for Rb-Sr geochronology, geochemistry and environmental studies.
基金supported by the National Natural Science Foundation of China(Nos.41973013,41730211)the Natural Science Foundation of Hubei Province(No.2020CFA045)the Most Special Fund from the State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences(Nos.MSFGPMR04 and MSFGPMR08)。
文摘This work evaluates the use of femtosecond laser ablation multiple collector inductively coupled plasma mass spectrometry(fs-LA-MC-ICP-MS) for Zr isotopic analysis in zircons. The mass fractionation caused by instrumental mass discrimination was corrected by a combination of internal correction using Sr as an internal standard(coming from a NIST SRM 987 standard solution) and external correction using a matrix-matched standard. Several important instrument parameters were investigated, such as the effect of the addition of N;and "wet" plasma condition, the mass fractionation behaviors between Zr isotopes and Sr isotopes, the position effect in laser ablation cell and the effect of laser ablation parameters(laser spot size and energy density). The Zr isotope compositions of seven zircons(GJ-1, 91500, Ple?ovice, Rak-17, Paki, Aus and Mala) were determined by the developed fs-LAMC-ICP-MS and thermal ionization mass spectrometry(TIMS). Our fs-LA-MC-ICP-MS results for Zr isotope compositions agreed with TIMS analyses within analytical uncertainties, indicating the presented method is a suitable tool to resolve isotopic zoning in natural zircons. The results also suggest that GJ-1, 91500, Ple?ovice, Paki, Aus and Mala had the homogenous Zr isotope composition and could be considered as the potential candidates for the Zr isotope analysis in zircons, except Rak-17 which presented the large Zr isotope variation.
基金supported by the National Natural Science Foundation of China(Grant Nos.41973013,41730211)the Natural Science Foundation of Hubei Province(Grant No.2020CFA045)the Most Special Fund from the State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences(Grant Nos.MSFGPMR04,MSFGPMR08)。
文摘We proposed a new laser analytical mode,which used the high-frequency laser ablation to deliberately obtain the peak-shape signal profile,combined with the linear regression calibration(LRC)method to calculate elemental or isotopic ratios.In order to assess the performance of the new laser analytical mode for the application in the field of earth science,we systematically investigated the elemental quantitative analysis with high spatial resolution(10μm),rapid U-Pb dating in zircons and accurate Sr-Hf isotope analysis in geological samples.The new high-frequency laser analysis technology(20 Hz,100 pulses)reduced the limit of detection(LOD)of 25 elements to 0.005-0.16μg g^(-1) with crater diameters of 10μm,which are significantly lower(decrease to 2-20%)than previous researches.The quantitative analysis of five silicate glass reference materials showed that the precision and accuracy of the 25 trace elements(with the concentration ranging from 0.17 to 683μg g^(-1))were better than 16% and 15%,respectively.The new methods raised the analytical throughput of zircon U-Pb dating,Sr isotope ratios and Hf isotope ratios to 250 analyses per hour,144 analyses per hour and 120 analyses per hour in theory,while the analytical accuracy and precision were not affected.The detailed investigations showed that the proposed new laser analytical mode has good application effects in the field of earth sciences.
基金supported by the National Science Fund for Distinguished Young Scholars (Grant No. 41725013)the National Natural Science Foundation of China (Grant Nos. 41903015 and 41873029)+2 种基金China National Space Administration (Grant No. D020205)the Natural Science Foundation of Hubei Province (Grant No. 2020CFA045)the MOST Special Fund from the State Key Laboratories of Geological Processes and Mineral Resources。
文摘Bastn?site is widespread in alkali granite, carbonatite and REE ore deposits. The U-Th-Pb ages of bastn?site can constrain the mineralization age. Currently, the lack of suitable in situ analysis reference material is the major obstacle of bastn?site U-Th-Pb geochronology. In this study, the matrix effects of U-Pb and Th-Pb age determination in bastn?site using glass NIST 610 as the external calibration reference were evaluated with the 193-nm excimer LA-ICP-MS analysis in normal and additional gases laser ablation modes. The obtained U-Th-Pb ages of bastn?site were approximately 7–11% lower than their reference values in the normal analytical mode(without additional gas). Fortunately, the determined systematic age biases in UTh-Pb dating were significantly reduced(less than 1–2%) with the addition of water vapor within the ablation chamber. This reduction may be attributed to the observed significant suppression of206 Pb/238 U and208 Pb/232 Th downhole fractionation in both NIST 610 glass and bastn?site by introducing a small quantity of water vapor in the ablation chamber. In addition, the obtained206 Pb/238 U and208 Pb/232 Th ages of bastn?site K-9, LZ1384, and MAD809 showed great consistency with their corresponding recommended values. The obtained results show that accurate and precise U-Th-Pb ages of bastn?site can be simultaneously obtained by using glass NIST 610 as the primary calibration standard in 193-nm LA-ICP-MS with the water vapor-assisted method. This simple and effective water vapor-assisted non-matrix-matched laser ablation method helps to promote the geological application of bastn?site U-Th-Pb geochronology.
基金co-supported by the National Natural Science Foundation of China(No.41922021)the MOST Special Fund from the State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences(No.MSFGPMR01-03)。
文摘The Permian basalts in the Central Asian Orogenic Belt(CAOB)are crucial for constraining the closure of the Paleo-Asian Ocean.However,the origin of these basalts is still under discussion.Here,we present comprehensive bulk-rock geochemical,Sr-Nd-Pb-Hf isotopic,and zircon U-Pb-Lu-Hf isotopic data of the Liuyuan basalts and coexisting gabbros,which are located in the Beishan Orogen in the southern CAOB,to constrain their emplacement setting and tectonic implications.Our new gabbro ages of ca.288–294 Ma are interpreted to represent the formation time of the Liuyuan basaltic belt.The Liuyuan basalts show MORB-like rare earth element(REE)patterns and bulk-rockε_(Hf)(t)andε_(Nd)(t)values of 11.0–15.4 and 4.6–9.2,respectively,suggesting an origination mainly from a depleted mantle source.However,positive Pb anomalies,Nb-Ta depletions,and high Th/Yb ratios as well as evolved Sr-Nd-Pb-Hf isotopic compositions of some samples indicate variable continental crustal contribution.According to the covariation of Pb anomalies(Pb^(*)=2×Pb_(N)/(Ce_(N)+Pr_(N)))with Sr-Nd-Pb-Hf isotopic compositions,we speculate that parent magma of the Liuyuan basalt was contaminated by continental crustal materials during the eruption rather than having been generated from an enriched mantle source.As revealed by mixing modelling,the Liuyuan basaltic magmas would require a minor(<10%)upper continental crustal assimilation to explain the enriched trace elemental and radiogenic Sr-Nd-Pb-Hf isotopic signatures.Consequently,the Liuyuan basaltic belt is believed to have been generated in a continental extensional environment instead of an oceanic setting and does not constitute a Permian ophiolitic suture zone as previously suggested,since the Paleo-Asian Ocean was already closed in the southern Beishan Orogen in the Early Permian.
基金supported by the Pre-Research Project on Civil Aerospace Technologies funded by CNSA (Grant No. D020205)the National Natural Science Foundation of China (Grant No. 42172337)the Program of the State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences (Grant No. GBL12101)。
文摘The successful return of lunar soil samples from the northern Oceanus Procellarum by the Chang’E 5(CE-5) mission has provided unprecedented ground-truth information for the previously unexplored region of the Moon. In particular, the particle size and mineral constituents of the CE-5 soil samples are of critical importance to interpret remote sensing data. With a Raman-based particle analysis system, we show that the particle size properties and mineral constituents of the CE-5 soil can be simultaneously determined with a small sample size(ca. 30 μg). The CE-5 sample scooped from the lunar surface has an overall small size between 0.4 μm and 73.9 μm(mean=3.5 μm), and mainly consists of pyroxene(39.4%), plagioclase(37.5%), olivine(9.8%), Fe-Ti oxides(1.9%), glass(8.3%) and other minor or trace phases. The results are consistent with previous analyses with larger sample sizes. In addition to minimum sample consumption, this method requires very little sample preparation, and can rapidly build a large database with each particle precisely traceable. Therefore, this novel technique is particularly suitable for the analysis of future returned soil samples from extraterrestrial bodies.
