Some elements normally occur at trace levels while the majority of natural geological materials may be exceedingly enriched in some special cases, such as the Bayan Obo ore deposit where REE and Nb are extremely enric...Some elements normally occur at trace levels while the majority of natural geological materials may be exceedingly enriched in some special cases, such as the Bayan Obo ore deposit where REE and Nb are extremely enriched. These elements may not be removed completely during purification. Therefore, matrix effects will be caused during stable isotope ratio measurement in the MC-ICP-MS. Experiments have shown that the established methods of chromatographic separation of Cu, Fe, and Zn using AG MP-1 Anion Exchange Resin cannot make ef-fective separation of Nb, W, and Cu from Fe using 20 mL 6 M HCl. It is also observed that the elution curves of W and Cu overlap at working conditions and thus W is present in measurable amounts in some sample solutions. Matrix effects in the MC-ICP-MS induced by Nb, W, and Cu during Fe isotope ratio measurements and by W during Cu isotope ratio measurements were thus investigated by examining their changes in delta values between doped and undoped standards. The results show that the effects of the matrix elements Nb, W, or Cu on Fe isotope ratio measurements are minimal in the case of m(Nb)/m(Fe)<0.005, m(W)/m(Fe)<0.01, or m(Cu)/m(Fe)<0.6. This finding, combined with the extremely low levels of W and Cu, and the fact that nearly 90% of Nb can be removed during purification, demonstrates that the methods of chromatographic separation of Fe established before are suitable for Bayan Obo ore samples and that the methods can be simplified when Cu elution is unnecessary. The effects of the matrix element W on Cu isotope determinations are minimal in the case of m(W)/m(Cu)<0.7. Therefore, W exerts no significant effect on the measurements of Cu isotopes for the majority of natural geological materials.展开更多
To better understand the Fe isotope characteristics of natural samples in the Karst area,the Fe isotope compositions of riverine suspended particulates,lake suspended particulates,lake sediments,porewaters,phytoplankt...To better understand the Fe isotope characteristics of natural samples in the Karst area,the Fe isotope compositions of riverine suspended particulates,lake suspended particulates,lake sediments,porewaters,phytoplanktons,and aerosols in the watersheds of Lake Aha(a mineralized water system)and Lake Hongfeng(a mesotrophic water system),which are located in the Karst area, southwest China,were investigated.The studied samples displayed a variable range betweenδ^(56)Fe=-2.03‰and 0.36‰.Aerosols and phytoplanktons have similar or slightly heavier Fe isotope compositions relative to the average of igneous rocks.Fe isotope compositions of riverine Suspended Particulate Matter(SPM)were mainly affected by the types of tributaries.Suspended particulates collected from tributaries seriously contaminated with coal mine drainages displayed negativeδ^(56)Fe values(-0.89‰to-0.31‰)during summer,and there were significant increases ofδ^(56)Fe values in winter,except AR2,which was polluted with both coal mine drainage and sewage effluent. Characteristics of lakes have important influences on Fe isotope compositions of suspended particulates,lake sediments,and porewaters.The epilimnetic particulate Fe of Lake Hongfeng hadδ^(56)Fe=-0.04‰to 0.13‰,while lighter Fe isotope compositions were measured for particulate Fe from Lake Aha,ranging from-0.42‰to-0.09‰.Sediments collected from Hou Wu(HW)station of Lake Hongfeng have an averageδ^(56)Fe value of 0.09‰and their corresponding porewaters have lighter Fe isotope compositions,ranging from-0.57‰to-0.31‰;no significant variations have been observed. For the Liang Jiang Kou(LJK)station of Lake Aha,the content of reactive Fe and the concentration of sulfate were all high.Due to the reactive Fe recycling,including dissimilatory Fe reduction,adsorption, and Fe-sulfide formation,porewaters sampled near the sediment surface have been found to have aδ^(56)Fe value as low as-2.03‰and an increase up to 0.12‰,with a burial depth of 10 cm.In contrast,an opposite variation trend was found for LJK sediments.Sediments sampled at 1-cm depth had a value ofδ^(56)Fe=-0.59‰and decrease as low as-1.75‰with burial depth.This investigation demonstrated that significant Fe isotope fractionations occur in surface environments.Fe isotope compositions of particulate Fe were seriously affected by Fe sources,and Fe biogeochemical recycling has an important influence on Fe isotope fractionations in lake sediments,especially when there are significant amounts of reactive Fe and sulfate.展开更多
Ti separation was achieved by ion-exchange chromatography using Bio-Rad AG 1-X8 anion-exchange and DGA resins.For high-Fe/Ti and high-Mg/Ti igneous samples,a three-column procedure was required,whereas a two-column pr...Ti separation was achieved by ion-exchange chromatography using Bio-Rad AG 1-X8 anion-exchange and DGA resins.For high-Fe/Ti and high-Mg/Ti igneous samples,a three-column procedure was required,whereas a two-column procedure was used for low-Fe/Ti and low-Mg/Ti igneous samples.The Ti isotopes were analysed by MC-ICP-MS,and instrumental mass bias was corrected using a ^(47)Ti-^(49)Ti double-spike technique.The ^(47)Ti-^(49)Ti double-spike and SRM 3162a were calibrated using SRM 979-Cr,certificated value ^(53)Cr/^(52)Crt rue=0.11339.Isobaric interference was evaluated by analysing Alfa-Ti doped with Na,Mg,Ca,and Mo,and results indicate that high concentrations of Na and Mg have no significant effect on Ti isotope analyses;however,Ca and Mo interferences lead to erroneousδ^(49/47)Ti values when Ca/Ti and Mo/Ti ratios exceed 0.01 and 0.1,respectively.Titanium isotopic compositions were determined for 12 igneous reference materials,BCR-2,BHVO-2,GBW07105,AGV-1,AGV-2,W-2,GBW07123,GBW07126,GBW07127,GBW07101,JP-1,and DTS-2b.Samples yieldδ^(49/47)Ti(‰)of−0.035±0.022,−0.038±0.031,0.031±0.022,0.059±0.038,0.044±0.037,0.000±0.015,0.154±0.044,−0.044±0.018,0.010±0.022,0.064±0.043,0.169±0.034,and−0.047±0.025(relative to OL-Ti,±2SD),respectively;of which isotopic compositions of DTS-2b,JP-1,GBW07101,GBW07105,GBW07123,GBW07126,and GBW07127 are reported for the first time.Standard Alfa-Ti was analysed repeatedly over a ten-month period,indicating a reproducibility of±0.047(2SD)forδ^(49/47)Ti,similar to the precisions obtained for geochemical reference materials.展开更多
The Paiku composite leucogranitic pluton in the Malashan gneiss dome within the Tethyan Himalaya consists of tourmaline leucogranite,two-mica granite and garnet-bearing leucogranite.Zircon U-Pb dating yields that(1)to...The Paiku composite leucogranitic pluton in the Malashan gneiss dome within the Tethyan Himalaya consists of tourmaline leucogranite,two-mica granite and garnet-bearing leucogranite.Zircon U-Pb dating yields that(1)tourmaline leucogranite formed at28.2±0.5 Ma and its source rock experienced simultaneous metamorphism and anatexis at 33.6±0.6 Ma;(2)two-mica granite formed at 19.8±0.5 Ma;(3)both types of leucogranite contain inherited zircon grains with an age peak at^480 Ma.These leucogranites show distinct geochemistry in major and trace elements as well as in Sr-Nd-Hf isotope compositions.As compared to the two-mica granites,the tourmaline ones have higher initial Sr and zircon Hf isotope compositions,indicating that they were derived from different source rocks combined with different melting reactions.Combined with available literature data,it is suggested that anatexis at^35 Ma along the Himalayan orogenic belt might have triggered the initial movement of the Southern Tibetan Detachment System(STDS),and led to the tectonic transition from compressive shortening to extension.Such a tectonic transition could be a dominant factor that initiates large scale decompressional melting of fertile high-grade metapelites along the Himalayan orogenic belt.Crustal anatexis at^28 Ma and^20 Ma represent large-scale melting reactions associated with the movement of the STDS.展开更多
The geochronological works for the Hannan intrusive complex, cosisting of the gabbro-quartz dio-rite-plagiogranite bodies, in the north border of the Yangtze craton block, adjoining the Qinling orogen, are reported, b...The geochronological works for the Hannan intrusive complex, cosisting of the gabbro-quartz dio-rite-plagiogranite bodies, in the north border of the Yangtze craton block, adjoining the Qinling orogen, are reported, because its age and genesis are of great importance to research of the tectonic evalutional history for the Qinling orogen and of the rifted processes for the Late Proterozoic supercontinent Rodinia. A good isochron of t=(837±26) Ma (2σ), corresponding to INd=0.51165±2(2σ), εNd(t)=+1.9, MSWD1.02, was difined by the Nd isotopic analytical results for the 21 whole-rock samples from the varied lithological complex bodies, but for the Rb-Sr isotopic aralytical data there is no isochron. The 40Ar/39Ar plateau age of the biotite, sorted from plagiogranites, is (796±20) Ma(2σ), and yet for the Rb-Sr isotopic data of the plagiogranite whole-rock samples (WR) and the sorted biotite (Bio), plagioclase (Plag) and apatite (Apt) mineral samples from the plagiogranitewhole-rock samples, an展开更多
The Qinling Mountains in central China are the joint orogenic zone between the Sino-Korean(or North China)and the Yangtze craton blocks.The age and genesis of the Danfeng mafic volcanics in the north of the Shangzhou-...The Qinling Mountains in central China are the joint orogenic zone between the Sino-Korean(or North China)and the Yangtze craton blocks.The age and genesis of the Danfeng mafic volcanics in the north of the Shangzhou-Danfeng fault zone,I.e.The main suture zone in the Qinling orogenic belt,have been controverted for a long time because their age is closely related to the converged time of two blocks.The ages and the geochemical data of the Heihe pillow lavas for the Danfeng mafic volcanics in the Heihe River area in the Qinling orogen are reported in this paper.The obtained isochron age by the Sm-Nd isotopic data of the 13 whole-rock samples for the mafic pillow lavas is 963±130(2σ)Ma,corresponding to I_(nd)=0.51173±16(2σ),ε_(Nd)(T)=+6.6,MSWD0.57.However,the Rb-Sr isotopic analytical results for the same samples as the Sm-Nd whole-rock ones are disperse.For the Sm-Nd isotopic systems were interfered during the later geological functions,the Sm-Nd isochron age for the whole-rock sample(Q9511WR)and the mineral phenocrystal sam-ples:amphiboles(Hb)and plagioclases(Plag)presents the better uncertainty,whereas isochron ages of 930 Ma and 437 Ma are given if the WR-Plag and WR-Hb are calculated respectively,and their Rb-Sr isochron age is 268±47(2σ)Ma,I_(sr)=0.70475±11(2σ),MSWD0.96.The major and trace elements for the lavas show that they were formed in the quasi-N-MORB setting.展开更多
基金financially supported by the National Natural Science Foundation of China (Grant No. 40973037)the MLR Public Benefit Research Foundation of China (Grant No.200911043-14)
文摘Some elements normally occur at trace levels while the majority of natural geological materials may be exceedingly enriched in some special cases, such as the Bayan Obo ore deposit where REE and Nb are extremely enriched. These elements may not be removed completely during purification. Therefore, matrix effects will be caused during stable isotope ratio measurement in the MC-ICP-MS. Experiments have shown that the established methods of chromatographic separation of Cu, Fe, and Zn using AG MP-1 Anion Exchange Resin cannot make ef-fective separation of Nb, W, and Cu from Fe using 20 mL 6 M HCl. It is also observed that the elution curves of W and Cu overlap at working conditions and thus W is present in measurable amounts in some sample solutions. Matrix effects in the MC-ICP-MS induced by Nb, W, and Cu during Fe isotope ratio measurements and by W during Cu isotope ratio measurements were thus investigated by examining their changes in delta values between doped and undoped standards. The results show that the effects of the matrix elements Nb, W, or Cu on Fe isotope ratio measurements are minimal in the case of m(Nb)/m(Fe)<0.005, m(W)/m(Fe)<0.01, or m(Cu)/m(Fe)<0.6. This finding, combined with the extremely low levels of W and Cu, and the fact that nearly 90% of Nb can be removed during purification, demonstrates that the methods of chromatographic separation of Fe established before are suitable for Bayan Obo ore samples and that the methods can be simplified when Cu elution is unnecessary. The effects of the matrix element W on Cu isotope determinations are minimal in the case of m(W)/m(Cu)<0.7. Therefore, W exerts no significant effect on the measurements of Cu isotopes for the majority of natural geological materials.
基金supported by the Natural Science Foundation of China(no40903008,90610037, 40721002,and 40331005)the Open Research Fund of State Key Laboratory of Environmental Geochemistry, Chinese Academy of Sciences(SKLEG9006)the Chinese important special project(No2009ZX07419-003)
文摘To better understand the Fe isotope characteristics of natural samples in the Karst area,the Fe isotope compositions of riverine suspended particulates,lake suspended particulates,lake sediments,porewaters,phytoplanktons,and aerosols in the watersheds of Lake Aha(a mineralized water system)and Lake Hongfeng(a mesotrophic water system),which are located in the Karst area, southwest China,were investigated.The studied samples displayed a variable range betweenδ^(56)Fe=-2.03‰and 0.36‰.Aerosols and phytoplanktons have similar or slightly heavier Fe isotope compositions relative to the average of igneous rocks.Fe isotope compositions of riverine Suspended Particulate Matter(SPM)were mainly affected by the types of tributaries.Suspended particulates collected from tributaries seriously contaminated with coal mine drainages displayed negativeδ^(56)Fe values(-0.89‰to-0.31‰)during summer,and there were significant increases ofδ^(56)Fe values in winter,except AR2,which was polluted with both coal mine drainage and sewage effluent. Characteristics of lakes have important influences on Fe isotope compositions of suspended particulates,lake sediments,and porewaters.The epilimnetic particulate Fe of Lake Hongfeng hadδ^(56)Fe=-0.04‰to 0.13‰,while lighter Fe isotope compositions were measured for particulate Fe from Lake Aha,ranging from-0.42‰to-0.09‰.Sediments collected from Hou Wu(HW)station of Lake Hongfeng have an averageδ^(56)Fe value of 0.09‰and their corresponding porewaters have lighter Fe isotope compositions,ranging from-0.57‰to-0.31‰;no significant variations have been observed. For the Liang Jiang Kou(LJK)station of Lake Aha,the content of reactive Fe and the concentration of sulfate were all high.Due to the reactive Fe recycling,including dissimilatory Fe reduction,adsorption, and Fe-sulfide formation,porewaters sampled near the sediment surface have been found to have aδ^(56)Fe value as low as-2.03‰and an increase up to 0.12‰,with a burial depth of 10 cm.In contrast,an opposite variation trend was found for LJK sediments.Sediments sampled at 1-cm depth had a value ofδ^(56)Fe=-0.59‰and decrease as low as-1.75‰with burial depth.This investigation demonstrated that significant Fe isotope fractionations occur in surface environments.Fe isotope compositions of particulate Fe were seriously affected by Fe sources,and Fe biogeochemical recycling has an important influence on Fe isotope fractionations in lake sediments,especially when there are significant amounts of reactive Fe and sulfate.
基金financially supported by the National Natural Science Foundation of China(Project Nos.41473005,41973020,41873027)。
文摘Ti separation was achieved by ion-exchange chromatography using Bio-Rad AG 1-X8 anion-exchange and DGA resins.For high-Fe/Ti and high-Mg/Ti igneous samples,a three-column procedure was required,whereas a two-column procedure was used for low-Fe/Ti and low-Mg/Ti igneous samples.The Ti isotopes were analysed by MC-ICP-MS,and instrumental mass bias was corrected using a ^(47)Ti-^(49)Ti double-spike technique.The ^(47)Ti-^(49)Ti double-spike and SRM 3162a were calibrated using SRM 979-Cr,certificated value ^(53)Cr/^(52)Crt rue=0.11339.Isobaric interference was evaluated by analysing Alfa-Ti doped with Na,Mg,Ca,and Mo,and results indicate that high concentrations of Na and Mg have no significant effect on Ti isotope analyses;however,Ca and Mo interferences lead to erroneousδ^(49/47)Ti values when Ca/Ti and Mo/Ti ratios exceed 0.01 and 0.1,respectively.Titanium isotopic compositions were determined for 12 igneous reference materials,BCR-2,BHVO-2,GBW07105,AGV-1,AGV-2,W-2,GBW07123,GBW07126,GBW07127,GBW07101,JP-1,and DTS-2b.Samples yieldδ^(49/47)Ti(‰)of−0.035±0.022,−0.038±0.031,0.031±0.022,0.059±0.038,0.044±0.037,0.000±0.015,0.154±0.044,−0.044±0.018,0.010±0.022,0.064±0.043,0.169±0.034,and−0.047±0.025(relative to OL-Ti,±2SD),respectively;of which isotopic compositions of DTS-2b,JP-1,GBW07101,GBW07105,GBW07123,GBW07126,and GBW07127 are reported for the first time.Standard Alfa-Ti was analysed repeatedly over a ten-month period,indicating a reproducibility of±0.047(2SD)forδ^(49/47)Ti,similar to the precisions obtained for geochemical reference materials.
基金supported by the National Basic Research Program of China(2011CB403102)the National Natural Science Foundation of China(41073024 and 41273034)
文摘The Paiku composite leucogranitic pluton in the Malashan gneiss dome within the Tethyan Himalaya consists of tourmaline leucogranite,two-mica granite and garnet-bearing leucogranite.Zircon U-Pb dating yields that(1)tourmaline leucogranite formed at28.2±0.5 Ma and its source rock experienced simultaneous metamorphism and anatexis at 33.6±0.6 Ma;(2)two-mica granite formed at 19.8±0.5 Ma;(3)both types of leucogranite contain inherited zircon grains with an age peak at^480 Ma.These leucogranites show distinct geochemistry in major and trace elements as well as in Sr-Nd-Hf isotope compositions.As compared to the two-mica granites,the tourmaline ones have higher initial Sr and zircon Hf isotope compositions,indicating that they were derived from different source rocks combined with different melting reactions.Combined with available literature data,it is suggested that anatexis at^35 Ma along the Himalayan orogenic belt might have triggered the initial movement of the Southern Tibetan Detachment System(STDS),and led to the tectonic transition from compressive shortening to extension.Such a tectonic transition could be a dominant factor that initiates large scale decompressional melting of fertile high-grade metapelites along the Himalayan orogenic belt.Crustal anatexis at^28 Ma and^20 Ma represent large-scale melting reactions associated with the movement of the STDS.
基金the NationalNatural Science Foundation of China (Grant Nos. 49732080 and 49773182).
文摘The geochronological works for the Hannan intrusive complex, cosisting of the gabbro-quartz dio-rite-plagiogranite bodies, in the north border of the Yangtze craton block, adjoining the Qinling orogen, are reported, because its age and genesis are of great importance to research of the tectonic evalutional history for the Qinling orogen and of the rifted processes for the Late Proterozoic supercontinent Rodinia. A good isochron of t=(837±26) Ma (2σ), corresponding to INd=0.51165±2(2σ), εNd(t)=+1.9, MSWD1.02, was difined by the Nd isotopic analytical results for the 21 whole-rock samples from the varied lithological complex bodies, but for the Rb-Sr isotopic aralytical data there is no isochron. The 40Ar/39Ar plateau age of the biotite, sorted from plagiogranites, is (796±20) Ma(2σ), and yet for the Rb-Sr isotopic data of the plagiogranite whole-rock samples (WR) and the sorted biotite (Bio), plagioclase (Plag) and apatite (Apt) mineral samples from the plagiogranitewhole-rock samples, an
基金the National Natural Science Foundation of China(Grant Nos.49773182,49732080).
文摘The Qinling Mountains in central China are the joint orogenic zone between the Sino-Korean(or North China)and the Yangtze craton blocks.The age and genesis of the Danfeng mafic volcanics in the north of the Shangzhou-Danfeng fault zone,I.e.The main suture zone in the Qinling orogenic belt,have been controverted for a long time because their age is closely related to the converged time of two blocks.The ages and the geochemical data of the Heihe pillow lavas for the Danfeng mafic volcanics in the Heihe River area in the Qinling orogen are reported in this paper.The obtained isochron age by the Sm-Nd isotopic data of the 13 whole-rock samples for the mafic pillow lavas is 963±130(2σ)Ma,corresponding to I_(nd)=0.51173±16(2σ),ε_(Nd)(T)=+6.6,MSWD0.57.However,the Rb-Sr isotopic analytical results for the same samples as the Sm-Nd whole-rock ones are disperse.For the Sm-Nd isotopic systems were interfered during the later geological functions,the Sm-Nd isochron age for the whole-rock sample(Q9511WR)and the mineral phenocrystal sam-ples:amphiboles(Hb)and plagioclases(Plag)presents the better uncertainty,whereas isochron ages of 930 Ma and 437 Ma are given if the WR-Plag and WR-Hb are calculated respectively,and their Rb-Sr isochron age is 268±47(2σ)Ma,I_(sr)=0.70475±11(2σ),MSWD0.96.The major and trace elements for the lavas show that they were formed in the quasi-N-MORB setting.