Controversy is ongoing regarding the relationship between ore formation and the structural evolution of the Hadamengou gold deposit.To address this issue,we conducted a comprehensive investigation of mineralization-re...Controversy is ongoing regarding the relationship between ore formation and the structural evolution of the Hadamengou gold deposit.To address this issue,we conducted a comprehensive investigation of mineralization-related structures,geochronology and Fe isotopes.From the perspective of spatial evolution,hydrothermal fluids originating from the Shadegai and Xishadegai plutons have extracted accumulated ore-forming elements from the Wulashan Group(Ar2WL)and then evolved,initiating at Exploration Line 11 and migrating eastwards and westwards along the EW-trending thrust fault system to form orebodies.From the temporal evolution standpoint,the Wulashan Group(Ar_(2)WL)experienced diagenesis(2591.00 Ma to 2204.00 Ma)and metamorphism(2074.00 Ma to 1625.00 Ma)from late Neoarchean to early Paleoproterozoic,when ore-forming materials were initially accumulated;in the early Paleozoic(440.71 Ma to 425.00 Ma),the collision led to the formation of early-stage EW-trending imbricated thrust faults,which established a fundamental structural framework for the orefield and further accumulated ore-forming materials;from the late Paleozoic to the Mesozoic,multiple subsequent episodes of regional tectonic-magmatic-hydrothermal events have superimposed,modified and reactivated the thrust fault system.Notably,the Triassic period,particularly between 245.00 Ma and 217.90 Ma,is considered to be a primary ore-forming stage.In summary,the intricate relationship between ore-formation and structural evolution has been fundamentally elucidated.展开更多
Although previous researchers have attempted to decipher ore genesis and mineralization in the Erdaokan Ag-Pb-Zn deposit,some uncertainties regarding the mineralization process and evolution of both ore-forming fluids...Although previous researchers have attempted to decipher ore genesis and mineralization in the Erdaokan Ag-Pb-Zn deposit,some uncertainties regarding the mineralization process and evolution of both ore-forming fluids and magnetite types still need to be addressed.In this study,we obtained new EPMA,LA-ICP-MS,and in situ Fe isotope data from magnetite from the Erdaokan deposit,in order to better understand the mineralization mechanism and evolution of both magnetite and the ore-forming fluids.Our results identified seven types of magnetite at Erdaokan:disseminated magnetite(Mag1),coarse-grained magnetite(Mag2a),radial magnetite(Mag2b),fragmented fine-grained magnetite(Mag2c),vermicular gel magnetite(Mag3a1 and Mag3a2),colloidal magnetite(Mag3b)and dark gray magnetite(Mag4).All of the magnetite types were hydrothermal in origin and generally low in Ti(<400 ppm)and Ni(<800 ppm),while being enriched in light Fe isotopes(δ^(56)Fe ranging from−1.54‰to−0.06‰).However,they exhibit different geochemical signatures and are thus classified into high-manganese magnetite(Mag1,MnO>5 wt%),low-silicon magnetite(Mag2a-c,SiO_(2)<1 wt%),high-silicon magnetite(Mag3a-b,SiO_(2)from 1 to 7 wt%)and high-silicon-manganese magnetite(Mag4,SiO_(2)>1 wt%,MnO>0.2 wt%),each being formed within distinct hydrothermal environments.Based on mineralogy,elemental geochemistry,Fe isotopes,temperature trends,TMg-mag and(Ti+V)vs.(Al+Mn)diagrams,we propose that the Erdaokan Ag-Pb-Zn deposit underwent multi-stage mineralization,which can be broken down into four stages and nine sub-stages.Mag1,Mag2a-c,Mag3a-b and Mag4 were formed during the first sub-stage of each of the four stages,respectively.Additionally,fluid mixing,cooling and depressurization boiling were identified as the main mechanisms for mineral precipitation.The enrichment of Ag was significantly enhanced by the superposition of multi-stage ore-forming hydrothermal fluids in the Erdaokan Ag-Pb-Zn deposit.展开更多
The sediments atop the sequence of ophiolite usually contain Fe(-Mn-Si)exhalites,chemical sediments that aremainlycomposedofamorphousFe-Mn oxy-hydroxides and chert/jasper.They were precipitated from hydrothermal fluid...The sediments atop the sequence of ophiolite usually contain Fe(-Mn-Si)exhalites,chemical sediments that aremainlycomposedofamorphousFe-Mn oxy-hydroxides and chert/jasper.They were precipitated from hydrothermal fluids produced by deep leaching of basalt particularly during volcano activity or seafloor spreading.These hydrothermal Fe exhalites provide a good record for the depositional environment and the ocean environment as well.A well-preserved Phanerozoic Fe deposit,Motuosala Fe-Mn deposit,resulted from hydrothermal exhalation,was investigated for its trace element and Fe isotope geochemistry.The deposit is located in Xinjiang province,China and is hosted in a suit of Carboniferous volcano-sedimentary clastic rocks.The Fe deposit is mainly composed of massive hematite Fe oreand banded hematite-jasper ore.The hematite ore/band and jasper band were subjected to be analyzed.They are both composed mainly of Fe2O3 and Si O2,with very low contents of Al2O3 and Ti O2(<1%),indicating they werechemical precipitates with little detrital contamination.They both show slightly LREE depleted or near flat PAAS-normalised REE patterns,with positive Eu anomalies and Y anomolies,indicating that they were sourced from a mixture of high-temperature fluids and seawater.Compared to the hematite Fe ore/band,the jasper band shows higher EuSN/EuSN*but lower Y/Ho values.δ56Fe values for the hematite Fe ores are clustered around-0.3‰,similar to those for high-temperature fluids.The jasper samples show heavier Fe isotope compositions varying from-0.1‰to0.5‰,indicating that they were resulted from partial Fe precipitation.For all samples,δ56Fe values are related to Y/Ho and EuSN/EuSN*values.The results indicate that the hematite Fe ore and jasper were deposited in different environments.The jasper was deposited in a more anoxic condition with higher hydrothermal fluids/seawater ratio,probably when the hydrothermal activity was more intense;while the hematite Fe ore was deposited in a more oxic condition with lower hydrothermal fluids/seawater ratio,probably when the hydrothermal activity was weaker.展开更多
Iron isotopic composition of the upper continental crust(UCC) is critical for understanding Fe mobilization and migration through the Earth. Because rocks exposed at Earth's surface have heterogeneous δ^(56)Fe, f...Iron isotopic composition of the upper continental crust(UCC) is critical for understanding Fe mobilization and migration through the Earth. Because rocks exposed at Earth's surface have heterogeneous δ^(56)Fe, finegrained clastic sediments can be used to estimate the average composition of UCC. In this study, we report δ^(56)Fe of loess-paleosol sequences from Yimaguan, Chinese Loess Plateau(CLP), to constrain the average Fe isotopic composition of UCC. The loess-paleosol sequences in this area formed in glacial-interglacial cycles and are characterized by varying degrees of weathering. Our data show that the loess-paleosol layers have extremely homogeneous Fe isotopic compositions with δ^(56)Fe ranging from 0.06‰ to 0.12‰, regardless of variations in the major element composition and weathering intensity. Our study indicates that since Fe isotopes are not significantly fractionated during loess deposition, the loess can be regarded as representative of UCC. It follows that the average δ^(56)Fe of UCC is 0.09‰± 0.03‰(2SD), consistent with previous estimates based on igneous rock data.展开更多
Element doping has been proved to be a useful method to correct for the mass bias fractionation when analyzing iron isotope compositions.We present a systematic re-assessment on how the doped nickel may affect the iro...Element doping has been proved to be a useful method to correct for the mass bias fractionation when analyzing iron isotope compositions.We present a systematic re-assessment on how the doped nickel may affect the iron isotope analysis in this study by carrying out several experiments.We find three important factors that can affect the analytical results,including the Ni:Fe ratio in the analyte solutions,the match of the Ni:Fe ratio between the unknown sample and standard solutions,and the match of the Fe concentration between the sample and standard solutions.Thus,caution is required when adding Ni to the analyte Fe solutions before analysis.Using our method,theδ56Fe and δ57Fe values of the USGS standards W-2 a,BHVO-2,BCR-2,AGV-2 and GSP-2 are consistent with the recommended literature values,and the long-term(one year) external reproducibility is better than 0.03 and 0.05‰(2 SD) for δ56Fe and δ57Fe,respectively.Therefore,the analytical method established in our laboratory is a method of choice for high quantity Fe isotope data in 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
The Neoproterozoic banded iron formations(BIFs)were closely associated with the“Snowball Earth”during the breakup of the Rodinia,thus they played an important role in our understanding of the atmospheric and oceanic...The Neoproterozoic banded iron formations(BIFs)were closely associated with the“Snowball Earth”during the breakup of the Rodinia,thus they played an important role in our understanding of the atmospheric and oceanic oxygen levels during this period.In this contribution,the Neoproterozoic(ca.737 Ma)Baijianshan BIF at Southeast Tarim,northwestern China was identified.Magnetite is the dominated iron-species,which occurs as the lamina interbedded with chert.The BIF contains low concentrations of trace elements,and is depleted in light rare earth elements(LREEs)based on comparison with the Post-Archean Australian Shale(PAAS).In addition,the BIF exhibits slightly positive La-Eu anomalies,negligible Ce anomalies,insignificant Y anomalies,chondritic Y/Ho ratios(23-32),and slightly chondritic initial ε_(Nd)(t=737 Ma)values(−0.45 to 1.46,averaging 0.37).All these features indicate that the precipitation of Baijianshan BIF was closely related to the submarine low-T hydrothermal fluids with little detrital contribution.Moreover,the Baijianshan BIF is characterized by the significant enrichment of heavy Fe isotopes,with δ^(57)Fe_(IRMM-014) values ranging from 1.78‰ to 3.05‰,revealing the partial oxidation of Fe^(2+) into Fe^(3+) during the precipitation of this BIF.Our data suggest that the formation of Baijianshan BIF was closely associated with a significantly reducing ocean,which most likely was isolated from the oxidized atmosphere by a local ice sheet.This Neoproterozoic Baijianshan ocean has the initial oxygen levels as low as,or even lower than that of Archean and Paleoproterozoic oceans.展开更多
Iron(Fe)is a productivity-limiting nutrient in the ocean.However,the sources of dissolved Fe(dFe)in the deep ocean and how they respond to tectonic and climate changes are still poorly understood.In the northern hemis...Iron(Fe)is a productivity-limiting nutrient in the ocean.However,the sources of dissolved Fe(dFe)in the deep ocean and how they respond to tectonic and climate changes are still poorly understood.In the northern hemisphere,dust flux to the low-latitude western Pacific has increased dramatically since the late Miocene associated with intense aridification of the Asian inland.Meanwhile,the terrigenous material supply to the open ocean might have also changed as a result of the reorganization of the Pacific circulation due to the gradual closure of seaways in the low latitudes.Therefore,the western Pacific is a characteristic region for understanding the sources of dFe in the deep ocean and their responses to long term climate changes.Here,we present data on isotopic evolution of dFe and dissolved Pb since^8 Ma based on ferromanganese crust METG-03(16.0°N,152.0°E,3850 m water depth)in the western Pacific deep water.Our results show thatδ56Fe of the crust remains fairly stable since the late Miocene,i.e.,about-0.32±0.08‰(2SD).We infer thatδ56Fe of dFe in the deep western Pacific is relatively invariant at^0.45±0.1‰based on the Fe isotopic fractionation between hydrogenetic crust and the seawater dissolved component.The reconstructed isotope signature is similar to the measuredδ56Fe value(0.37±0.15‰)of the intermediate to deep waters in the modern low-latitude western Pacific region close to the island arcs,but is significantly higher than that of the eastern Pacific deep waters near South America which is controlled by the reductive dissolution of continental shelf sediments and the hydrothermal inputs(δ56Fe<-0.1‰).The deep-water 206Pb/204Pb ratio recorded by METG-03 displays systematic increase at about 8–4 Ma,reflecting increased input from sediment dissolution of low-latitude island arcs associated with reorganization of the western Pacific deep circulation.Notably,Fe isotopes of terrigenous materials from different sources are similar,while their dissolved Fe isotopic signatures released to the ocean are mainly controlled by the mechanism of particle dissolution.The stability ofδ56Fe and systematic changes in Pb isotopes over the last^8 Ma thus suggest that Asian dust dissolution and hydrothermal inputs are likely only minor sources of dFe in the low-latitude deep western Pacific,while the acquisition and transport of dFe from shelf sediments by organic ligand binding in the oxic environment is the major dFe source which keeps stable on tectonic time scales since the late Miocene.展开更多
Iron (Fe) migration in soil-plants is a critical part of Fe biogeochemical cycling in the earth surface system. Fe isotope fractionation analysis in the soil-rice system is promising for quantitatively assessing vario...Iron (Fe) migration in soil-plants is a critical part of Fe biogeochemical cycling in the earth surface system. Fe isotope fractionation analysis in the soil-rice system is promising for quantitatively assessing various pathways and clarifying Fe transformation processes. However, the mechanisms of Fe isotope fractionation in the soil-rice system are not well understood. In this study, the Fe isotopic compositions (δ^(56)Fe) of rhizosphere soils, pore water, Fe plaque, and rice plant tissues at the jointing and mature stages of the plants were determined. The rice plants were slightly enriched in heavier δ^(56)Fe by 0.3‰ relative to the soil, and the stele and cortex showed similar δ^(56)Fe values, indicating that the uptake of Fe by rice plants predominantly occurred via Fe(III)-phytosiderophores (Fe(III)-PS) chelation, but not Fe(III) reduction. Additionally, at both the jointing and mature stages, the rice plant tissues showed similar δ^(56)Fe values. However, the Fe isotope fractionation between the roots and stems (Δ56Feroot−stem) was 1.39 ± 0.13‰, which is similar to the previously Ab initio-calculated values between Fe(III)-citrate and Fe(III)- 2-deoxymugineic acid (DMA), indicating that both the phloem and xylem have similar δ^(56)Fe values, and the major Fe-chelating substances in the phloem of the rice plants are Fe(III)-DMA and Fe(II)- Nicotianamine (NA). Therefore, this study demonstrates that Fe isotope fractionation can be used as a signature for interpreting the Fe uptake and translocation mechanism in the soil-rice system.展开更多
基金the financial support by the Major Research Plan of National Natural Science Foundation of China(92062219)the Young Elite Scientists Sponsorship Program by BAST(No.BYESS2023411)+2 种基金the Open Research Project from the State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences(GPMR202407)the Geological Survey Project of the China Geological Survey„General survey of Hadamengou Rock Gold Deposit in Inner Mongolia'(DD20191017)the Geological Survey Project(H90063).
文摘Controversy is ongoing regarding the relationship between ore formation and the structural evolution of the Hadamengou gold deposit.To address this issue,we conducted a comprehensive investigation of mineralization-related structures,geochronology and Fe isotopes.From the perspective of spatial evolution,hydrothermal fluids originating from the Shadegai and Xishadegai plutons have extracted accumulated ore-forming elements from the Wulashan Group(Ar2WL)and then evolved,initiating at Exploration Line 11 and migrating eastwards and westwards along the EW-trending thrust fault system to form orebodies.From the temporal evolution standpoint,the Wulashan Group(Ar_(2)WL)experienced diagenesis(2591.00 Ma to 2204.00 Ma)and metamorphism(2074.00 Ma to 1625.00 Ma)from late Neoarchean to early Paleoproterozoic,when ore-forming materials were initially accumulated;in the early Paleozoic(440.71 Ma to 425.00 Ma),the collision led to the formation of early-stage EW-trending imbricated thrust faults,which established a fundamental structural framework for the orefield and further accumulated ore-forming materials;from the late Paleozoic to the Mesozoic,multiple subsequent episodes of regional tectonic-magmatic-hydrothermal events have superimposed,modified and reactivated the thrust fault system.Notably,the Triassic period,particularly between 245.00 Ma and 217.90 Ma,is considered to be a primary ore-forming stage.In summary,the intricate relationship between ore-formation and structural evolution has been fundamentally elucidated.
基金financially supported by the Heilongjiang Provincial Key R&D Program Project(No.GA21A204)Heilongjiang Provincial Natural Science Foundation of China(No.LH2022D031)the Research Project of Heilongjiang Province Bureau of Geology and Mineral Resources(No.HKY202302).
文摘Although previous researchers have attempted to decipher ore genesis and mineralization in the Erdaokan Ag-Pb-Zn deposit,some uncertainties regarding the mineralization process and evolution of both ore-forming fluids and magnetite types still need to be addressed.In this study,we obtained new EPMA,LA-ICP-MS,and in situ Fe isotope data from magnetite from the Erdaokan deposit,in order to better understand the mineralization mechanism and evolution of both magnetite and the ore-forming fluids.Our results identified seven types of magnetite at Erdaokan:disseminated magnetite(Mag1),coarse-grained magnetite(Mag2a),radial magnetite(Mag2b),fragmented fine-grained magnetite(Mag2c),vermicular gel magnetite(Mag3a1 and Mag3a2),colloidal magnetite(Mag3b)and dark gray magnetite(Mag4).All of the magnetite types were hydrothermal in origin and generally low in Ti(<400 ppm)and Ni(<800 ppm),while being enriched in light Fe isotopes(δ^(56)Fe ranging from−1.54‰to−0.06‰).However,they exhibit different geochemical signatures and are thus classified into high-manganese magnetite(Mag1,MnO>5 wt%),low-silicon magnetite(Mag2a-c,SiO_(2)<1 wt%),high-silicon magnetite(Mag3a-b,SiO_(2)from 1 to 7 wt%)and high-silicon-manganese magnetite(Mag4,SiO_(2)>1 wt%,MnO>0.2 wt%),each being formed within distinct hydrothermal environments.Based on mineralogy,elemental geochemistry,Fe isotopes,temperature trends,TMg-mag and(Ti+V)vs.(Al+Mn)diagrams,we propose that the Erdaokan Ag-Pb-Zn deposit underwent multi-stage mineralization,which can be broken down into four stages and nine sub-stages.Mag1,Mag2a-c,Mag3a-b and Mag4 were formed during the first sub-stage of each of the four stages,respectively.Additionally,fluid mixing,cooling and depressurization boiling were identified as the main mechanisms for mineral precipitation.The enrichment of Ag was significantly enhanced by the superposition of multi-stage ore-forming hydrothermal fluids in the Erdaokan Ag-Pb-Zn deposit.
文摘The sediments atop the sequence of ophiolite usually contain Fe(-Mn-Si)exhalites,chemical sediments that aremainlycomposedofamorphousFe-Mn oxy-hydroxides and chert/jasper.They were precipitated from hydrothermal fluids produced by deep leaching of basalt particularly during volcano activity or seafloor spreading.These hydrothermal Fe exhalites provide a good record for the depositional environment and the ocean environment as well.A well-preserved Phanerozoic Fe deposit,Motuosala Fe-Mn deposit,resulted from hydrothermal exhalation,was investigated for its trace element and Fe isotope geochemistry.The deposit is located in Xinjiang province,China and is hosted in a suit of Carboniferous volcano-sedimentary clastic rocks.The Fe deposit is mainly composed of massive hematite Fe oreand banded hematite-jasper ore.The hematite ore/band and jasper band were subjected to be analyzed.They are both composed mainly of Fe2O3 and Si O2,with very low contents of Al2O3 and Ti O2(<1%),indicating they werechemical precipitates with little detrital contamination.They both show slightly LREE depleted or near flat PAAS-normalised REE patterns,with positive Eu anomalies and Y anomolies,indicating that they were sourced from a mixture of high-temperature fluids and seawater.Compared to the hematite Fe ore/band,the jasper band shows higher EuSN/EuSN*but lower Y/Ho values.δ56Fe values for the hematite Fe ores are clustered around-0.3‰,similar to those for high-temperature fluids.The jasper samples show heavier Fe isotope compositions varying from-0.1‰to0.5‰,indicating that they were resulted from partial Fe precipitation.For all samples,δ56Fe values are related to Y/Ho and EuSN/EuSN*values.The results indicate that the hematite Fe ore and jasper were deposited in different environments.The jasper was deposited in a more anoxic condition with higher hydrothermal fluids/seawater ratio,probably when the hydrothermal activity was more intense;while the hematite Fe ore was deposited in a more oxic condition with lower hydrothermal fluids/seawater ratio,probably when the hydrothermal activity was weaker.
基金financially supported by the National Science Foundation of China(41173031,41325011 and 41503001)the Fundamental Research Funds for the Central Universities(WK3410000004)
文摘Iron isotopic composition of the upper continental crust(UCC) is critical for understanding Fe mobilization and migration through the Earth. Because rocks exposed at Earth's surface have heterogeneous δ^(56)Fe, finegrained clastic sediments can be used to estimate the average composition of UCC. In this study, we report δ^(56)Fe of loess-paleosol sequences from Yimaguan, Chinese Loess Plateau(CLP), to constrain the average Fe isotopic composition of UCC. The loess-paleosol sequences in this area formed in glacial-interglacial cycles and are characterized by varying degrees of weathering. Our data show that the loess-paleosol layers have extremely homogeneous Fe isotopic compositions with δ^(56)Fe ranging from 0.06‰ to 0.12‰, regardless of variations in the major element composition and weathering intensity. Our study indicates that since Fe isotopes are not significantly fractionated during loess deposition, the loess can be regarded as representative of UCC. It follows that the average δ^(56)Fe of UCC is 0.09‰± 0.03‰(2SD), consistent with previous estimates based on igneous rock data.
基金This work was supported by National Nature Science Foundation of China(Grant Numbers 41776067 and 41630968).
文摘Element doping has been proved to be a useful method to correct for the mass bias fractionation when analyzing iron isotope compositions.We present a systematic re-assessment on how the doped nickel may affect the iron isotope analysis in this study by carrying out several experiments.We find three important factors that can affect the analytical results,including the Ni:Fe ratio in the analyte solutions,the match of the Ni:Fe ratio between the unknown sample and standard solutions,and the match of the Fe concentration between the sample and standard solutions.Thus,caution is required when adding Ni to the analyte Fe solutions before analysis.Using our method,theδ56Fe and δ57Fe values of the USGS standards W-2 a,BHVO-2,BCR-2,AGV-2 and GSP-2 are consistent with the recommended literature values,and the long-term(one year) external reproducibility is better than 0.03 and 0.05‰(2 SD) for δ56Fe and δ57Fe,respectively.Therefore,the analytical method established in our laboratory is a method of choice for high quantity Fe isotope data in 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funded by the Fundamental Research Fund for central universities(Grant No.B16020127)。
文摘The Neoproterozoic banded iron formations(BIFs)were closely associated with the“Snowball Earth”during the breakup of the Rodinia,thus they played an important role in our understanding of the atmospheric and oceanic oxygen levels during this period.In this contribution,the Neoproterozoic(ca.737 Ma)Baijianshan BIF at Southeast Tarim,northwestern China was identified.Magnetite is the dominated iron-species,which occurs as the lamina interbedded with chert.The BIF contains low concentrations of trace elements,and is depleted in light rare earth elements(LREEs)based on comparison with the Post-Archean Australian Shale(PAAS).In addition,the BIF exhibits slightly positive La-Eu anomalies,negligible Ce anomalies,insignificant Y anomalies,chondritic Y/Ho ratios(23-32),and slightly chondritic initial ε_(Nd)(t=737 Ma)values(−0.45 to 1.46,averaging 0.37).All these features indicate that the precipitation of Baijianshan BIF was closely related to the submarine low-T hydrothermal fluids with little detrital contribution.Moreover,the Baijianshan BIF is characterized by the significant enrichment of heavy Fe isotopes,with δ^(57)Fe_(IRMM-014) values ranging from 1.78‰ to 3.05‰,revealing the partial oxidation of Fe^(2+) into Fe^(3+) during the precipitation of this BIF.Our data suggest that the formation of Baijianshan BIF was closely associated with a significantly reducing ocean,which most likely was isolated from the oxidized atmosphere by a local ice sheet.This Neoproterozoic Baijianshan ocean has the initial oxygen levels as low as,or even lower than that of Archean and Paleoproterozoic oceans.
基金supported by the National Natural Science Foundation of China(Grant Nos.91858105&41822603)。
文摘Iron(Fe)is a productivity-limiting nutrient in the ocean.However,the sources of dissolved Fe(dFe)in the deep ocean and how they respond to tectonic and climate changes are still poorly understood.In the northern hemisphere,dust flux to the low-latitude western Pacific has increased dramatically since the late Miocene associated with intense aridification of the Asian inland.Meanwhile,the terrigenous material supply to the open ocean might have also changed as a result of the reorganization of the Pacific circulation due to the gradual closure of seaways in the low latitudes.Therefore,the western Pacific is a characteristic region for understanding the sources of dFe in the deep ocean and their responses to long term climate changes.Here,we present data on isotopic evolution of dFe and dissolved Pb since^8 Ma based on ferromanganese crust METG-03(16.0°N,152.0°E,3850 m water depth)in the western Pacific deep water.Our results show thatδ56Fe of the crust remains fairly stable since the late Miocene,i.e.,about-0.32±0.08‰(2SD).We infer thatδ56Fe of dFe in the deep western Pacific is relatively invariant at^0.45±0.1‰based on the Fe isotopic fractionation between hydrogenetic crust and the seawater dissolved component.The reconstructed isotope signature is similar to the measuredδ56Fe value(0.37±0.15‰)of the intermediate to deep waters in the modern low-latitude western Pacific region close to the island arcs,but is significantly higher than that of the eastern Pacific deep waters near South America which is controlled by the reductive dissolution of continental shelf sediments and the hydrothermal inputs(δ56Fe<-0.1‰).The deep-water 206Pb/204Pb ratio recorded by METG-03 displays systematic increase at about 8–4 Ma,reflecting increased input from sediment dissolution of low-latitude island arcs associated with reorganization of the western Pacific deep circulation.Notably,Fe isotopes of terrigenous materials from different sources are similar,while their dissolved Fe isotopic signatures released to the ocean are mainly controlled by the mechanism of particle dissolution.The stability ofδ56Fe and systematic changes in Pb isotopes over the last^8 Ma thus suggest that Asian dust dissolution and hydrothermal inputs are likely only minor sources of dFe in the low-latitude deep western Pacific,while the acquisition and transport of dFe from shelf sediments by organic ligand binding in the oxic environment is the major dFe source which keeps stable on tectonic time scales since the late Miocene.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.41807026,42030702,and U20A20109)China Postdoctoral Science Foundation(Grant Nos.2020T130126 and 2019M662820)+3 种基金Guangdong Key Research and Development Project(Grant Nos.2019B110207002)Local Innovative and Research Teams Project of Guangdong Pearl River Talents Program(Grant Nos.2017BT01Z176)projects of Science and Technology Development in Guangdong Academy of Sciences(Grant Nos.2020GDASYL-20200104022 and 2019GDASYL-0103054)Guangdong Special Support Plan for High-Level Talents(Grant Nos.2017TX04Z175).
文摘Iron (Fe) migration in soil-plants is a critical part of Fe biogeochemical cycling in the earth surface system. Fe isotope fractionation analysis in the soil-rice system is promising for quantitatively assessing various pathways and clarifying Fe transformation processes. However, the mechanisms of Fe isotope fractionation in the soil-rice system are not well understood. In this study, the Fe isotopic compositions (δ^(56)Fe) of rhizosphere soils, pore water, Fe plaque, and rice plant tissues at the jointing and mature stages of the plants were determined. The rice plants were slightly enriched in heavier δ^(56)Fe by 0.3‰ relative to the soil, and the stele and cortex showed similar δ^(56)Fe values, indicating that the uptake of Fe by rice plants predominantly occurred via Fe(III)-phytosiderophores (Fe(III)-PS) chelation, but not Fe(III) reduction. Additionally, at both the jointing and mature stages, the rice plant tissues showed similar δ^(56)Fe values. However, the Fe isotope fractionation between the roots and stems (Δ56Feroot−stem) was 1.39 ± 0.13‰, which is similar to the previously Ab initio-calculated values between Fe(III)-citrate and Fe(III)- 2-deoxymugineic acid (DMA), indicating that both the phloem and xylem have similar δ^(56)Fe values, and the major Fe-chelating substances in the phloem of the rice plants are Fe(III)-DMA and Fe(II)- Nicotianamine (NA). Therefore, this study demonstrates that Fe isotope fractionation can be used as a signature for interpreting the Fe uptake and translocation mechanism in the soil-rice system.
