In this work,an isotopic analysis of δ^(18)O,δ^(13)C,and NO_(3)^(-) concentrations was carried out to identify the origin and the processes related to the contamination of an aquifer located in the state of Guanajua...In this work,an isotopic analysis of δ^(18)O,δ^(13)C,and NO_(3)^(-) concentrations was carried out to identify the origin and the processes related to the contamination of an aquifer located in the state of Guanajuato,Mexico.The research identified the possible sources of δ^(13)C in groundwater.During groundwater flow,CO_(2) participates in different hydrogeochemical reactions in which the dissolution of carbonates or biochemical processes related to biodegradation stand out.Isotopic data of δ^(13)C,δ^(18)O,and the hydrogeochemical behavior of NO_(3)^(-) and HCO_(3)^(-) in water,in addition to isotopic data and the chemical composition of limestones in the study area,were determined to establish the isotopic signature and the processes undergone by the rocks.The isotopic signature of rock and water samples indicated that metamorphic limestones contributed with carbon dioxide to deep groundwater,while in the upper aquifer,bacterial metabolic reactions during nitrification–denitrification could modify the isotopic signature of δ^(13)C in some wells,although atmospheric contribution also plays a role.The modification of the carbon isotopic component is related to the precipitation of calcite in specific regions of the study area,input of atmospheric CO_(2),and soil(e.g.the possible participation of C4-type plants in the assimilation-release of carbon).This process is not confirmed or completely ruled out in this study since agriculture is excessively developed throughout the region.The joint interpretation of isotopic values and the hydrogeochemical behavior of major and conservative elements help in identifying possible pollution processes in which different carbon sources are related.展开更多
Quaternary intraplate magmatism formed several volcanic islands and seamounts,including Dokdo(DD),Ulleungdo(UD),Simheungtack(ST),Anyongbok,and Isabu in the southwest of the East Sea back-arc basin.In this study,we pre...Quaternary intraplate magmatism formed several volcanic islands and seamounts,including Dokdo(DD),Ulleungdo(UD),Simheungtack(ST),Anyongbok,and Isabu in the southwest of the East Sea back-arc basin.In this study,we present whole-rock geochemical,zircon U–Pb age,and in situ O–Hf isotope data for the submerged volcanic rocks from DD,UD,and ST to provide new insights into the eruption timing of these volcanoes and constrain the magma evolution processes.All samples used in this study were trachytes and exhibited ferroan,alkalic,and metaluminous to weakly peraluminous characteristics.They showed light rare earth element(REE)-enriched patterns with(La/Yb)N ratios of 25.3–31.7 and mostly negative Eu anomalies in a chondrite-normalized REE plot.In addition,they were enriched in large-ion lithophile elements and high field strength elements;they exhibited positive Pb anomalies and strongly negative Ba,Sr,P,and Ti anomalies.The zircons yielded a weighted-mean 206Pb/238U age of 2.61,0.348–0.704,and 2.76–2.94 Ma for the DD,UD,and ST trachytes,respectively.All zircons exhibited lowerδ^(18)O values than normal depleted mantle values,regardless of the crystallization age and spatial distribution of volcanoes.Theδ^(18)O values showed no correlation with U contents or Th/U ratios,indicating that the lowδ^(18)O signatures were of primary magmatic origin.The Hf isotopic compositions of the zircons were relatively heterogeneous but predominately characterized by positive eHf values.Binary O–Hf mixing modeling revealed that low-δ^(18)O rocks with positive eHf values from the UD and ST volcanoes were derived from a hybrid source of recycled juvenile crustal materials with low-δ^(18)O and positive eHf signatures and an enriched mantle source with normalδ^(18)O and negative eHf values.The juvenile oceanic crust in the source was likely metasomatized by seawater at high temperatures prior to melting.In contrast,the felsic magma that formed the DD volcanoes may have assimilated with regional basement rocks(Triassic–Jurassic granitoids),resulting in increasedδ^(18)O values and decreased eHf values relative to those of the UD and ST volcanoes.Our study highlights the significant contribution of recycled oceanic crust materials to the generation of the Quaternary magmas.展开更多
Power-law patterns appear in a variety of natural systems on the modern Earth;nevertheless,whether such behaviors appeared in the deep-time environment has rarely been studied. Isotopic records in sedimentary rocks, w...Power-law patterns appear in a variety of natural systems on the modern Earth;nevertheless,whether such behaviors appeared in the deep-time environment has rarely been studied. Isotopic records in sedimentary rocks, which are widely used to reconstruct the geological/geochemical conditions in paleoenvironments and the evolutionary trajectories of biogeochemical cycles, offer an opportunity to investigate power laws in ancient geological systems. In this study, I focus on the Phanerozoic sedimentary records of carbon, oxygen, sulfur, and strontium isotopes, which have well documented and extraordinarily comprehensive datasets. I perform statistical analyses on these datasets and show that the variations in the sedimentary records of the four isotopes exhibit power-law behaviors. The exponents of these power laws range between 2.2 and 2.9;this narrow interval indicates that the variations in carbon, oxygen, sulfur, and strontium isotopes likely belong to the same universality class, suggesting that these systematic power-law patterns are governed by universal, scale-free mechanisms. I then derive a general form for these power laws from a minimalistic model based on basic physical principles and geosystem-specific assumptions, which provides an interpretation for the power-law patterns from the perspective of thermodynamics. The fundamental mechanisms regulating such patterns might have been ubiquitous in paleoenvironments, implying that similar power-law behaviors may exist in the sedimentary records of other isotopes.展开更多
The oxygen isotopic data for amphibolites from Archaean continental nucleus, North China Craton indicate that ( i ) the evolving lines structured by the data are parallel to the geoselenic evolving line, which means t...The oxygen isotopic data for amphibolites from Archaean continental nucleus, North China Craton indicate that ( i ) the evolving lines structured by the data are parallel to the geoselenic evolving line, which means that the parent materials of these continental nucleus o-riginated from solar matter; ( ii ) different intercepts for these evolving lines manifest that oxy-展开更多
During the 22nd Chinese Antarctic Research Expedition (CHINARE-22), the atmospheric gas samples above the oceanic surface and near the surface were collected on the track for the scientific ship "Xuelong" an...During the 22nd Chinese Antarctic Research Expedition (CHINARE-22), the atmospheric gas samples above the oceanic surface and near the surface were collected on the track for the scientific ship "Xuelong" and on Millor Peninsula of eastern Antarctica, respectively, using the Tedlar gas bags. Every day the sampling times were 10:00 and 22:00 (local time), respectively. In the laboratory, high-precision measurement of the isotopic compositions for N2O in these gas samples was conducted using Thermo Finnigan MAT-253 Isotopic Mass Spectrometer with a fully automated interface for the pre-GC concen-tration (PreCon) of trace gases. The temporal and spatial variations of δ 15N and δ 18O in atmospheric N2O were analyzed. The mean δ 15N and δ 18O-N2O values above the oceanic surface were (7.21±0.50)‰ and (44.52±0.52)‰, respectively. From 30°N to Antarctica, the δ 15N (6.05‰―7.88‰) linearly increased with the rate of about 0.01‰ with the latitude while the δ 18O (43.05‰―48.78‰) showed a large fluctua-tion. The δ 15N negatively correlated with air temperature and N2O concentration, and slightly positively correlated with δ 18O. The summertime variations of δ 15N and δ 18O-N2O appeared the same trend on Millor Peninsula of eastern Antarctica. They significantly positively correlated with each other and negatively with N2O concentration. The δ 15N and δ 18O-N2O at different sites averaged (7.42±0.35)‰ and (44.69±0.49)‰, respectively, slightly higher than those above the oceanic surface, significantly higher than those of atmospheric N2O in the low-latitude regions of Northern Hemisphere. The predominant factors affecting the spatial variations of δ 15N and δ 18O values were also discussed. The isotopic data given in this study can help to investigate the global and regional N2O budgets.展开更多
The denitrifier method is widely used as a novel pretreatment method for the determination of nitrogen and oxygen isotope ratios as it can provide quantitative and high-sensitivity measurements. Nevertheless, the meth...The denitrifier method is widely used as a novel pretreatment method for the determination of nitrogen and oxygen isotope ratios as it can provide quantitative and high-sensitivity measurements. Nevertheless, the method is limited by relatively low measurement accuracy for δ18 O. In this study, we analyzed the factors influencing the accuracy of δ18 O determination, and then systematically investigated the effects of dissolved oxygen concentrations and nitrate sample sizes on estimates of the δ15 N and δ18 O of nitrate reference materials. The δ18 O contraction ratio was used to represent the relationship between the measured difference and true difference between two reference materials. We obtained the following main results:(1) a gas-liquid ratio of 3:10(v/v) in ordinary triangular flasks and a shaking speed of 120 r/min produced an optimal range(1.9 to 2.6 mg/L) in the concentration of dissolved oxygen for accurately determining δ18 O, and(2) the δ18 O contraction ratio decreased as nitrate sample size decreased within a certain range(1.0 to 0.1 μmol). Our results suggested that δ18 O contraction is influenced mainly by dissolved oxygen concentrations in pure culture, and provided a model for improving the accuracy of oxygen isotope analysis.展开更多
基金financed by PAPIIT,and the grant number is IA101019PAPIIT for its support and the scholarships provided to students Cuellar Ramírez E。
文摘In this work,an isotopic analysis of δ^(18)O,δ^(13)C,and NO_(3)^(-) concentrations was carried out to identify the origin and the processes related to the contamination of an aquifer located in the state of Guanajuato,Mexico.The research identified the possible sources of δ^(13)C in groundwater.During groundwater flow,CO_(2) participates in different hydrogeochemical reactions in which the dissolution of carbonates or biochemical processes related to biodegradation stand out.Isotopic data of δ^(13)C,δ^(18)O,and the hydrogeochemical behavior of NO_(3)^(-) and HCO_(3)^(-) in water,in addition to isotopic data and the chemical composition of limestones in the study area,were determined to establish the isotopic signature and the processes undergone by the rocks.The isotopic signature of rock and water samples indicated that metamorphic limestones contributed with carbon dioxide to deep groundwater,while in the upper aquifer,bacterial metabolic reactions during nitrification–denitrification could modify the isotopic signature of δ^(13)C in some wells,although atmospheric contribution also plays a role.The modification of the carbon isotopic component is related to the precipitation of calcite in specific regions of the study area,input of atmospheric CO_(2),and soil(e.g.the possible participation of C4-type plants in the assimilation-release of carbon).This process is not confirmed or completely ruled out in this study since agriculture is excessively developed throughout the region.The joint interpretation of isotopic values and the hydrogeochemical behavior of major and conservative elements help in identifying possible pollution processes in which different carbon sources are related.
基金This research was supported by a project on the sustainable research and development of Dokdo(Grant No.PG52911)which is funded by the Ministry of Oceans and Fisheries,South Korea.
文摘Quaternary intraplate magmatism formed several volcanic islands and seamounts,including Dokdo(DD),Ulleungdo(UD),Simheungtack(ST),Anyongbok,and Isabu in the southwest of the East Sea back-arc basin.In this study,we present whole-rock geochemical,zircon U–Pb age,and in situ O–Hf isotope data for the submerged volcanic rocks from DD,UD,and ST to provide new insights into the eruption timing of these volcanoes and constrain the magma evolution processes.All samples used in this study were trachytes and exhibited ferroan,alkalic,and metaluminous to weakly peraluminous characteristics.They showed light rare earth element(REE)-enriched patterns with(La/Yb)N ratios of 25.3–31.7 and mostly negative Eu anomalies in a chondrite-normalized REE plot.In addition,they were enriched in large-ion lithophile elements and high field strength elements;they exhibited positive Pb anomalies and strongly negative Ba,Sr,P,and Ti anomalies.The zircons yielded a weighted-mean 206Pb/238U age of 2.61,0.348–0.704,and 2.76–2.94 Ma for the DD,UD,and ST trachytes,respectively.All zircons exhibited lowerδ^(18)O values than normal depleted mantle values,regardless of the crystallization age and spatial distribution of volcanoes.Theδ^(18)O values showed no correlation with U contents or Th/U ratios,indicating that the lowδ^(18)O signatures were of primary magmatic origin.The Hf isotopic compositions of the zircons were relatively heterogeneous but predominately characterized by positive eHf values.Binary O–Hf mixing modeling revealed that low-δ^(18)O rocks with positive eHf values from the UD and ST volcanoes were derived from a hybrid source of recycled juvenile crustal materials with low-δ^(18)O and positive eHf signatures and an enriched mantle source with normalδ^(18)O and negative eHf values.The juvenile oceanic crust in the source was likely metasomatized by seawater at high temperatures prior to melting.In contrast,the felsic magma that formed the DD volcanoes may have assimilated with regional basement rocks(Triassic–Jurassic granitoids),resulting in increasedδ^(18)O values and decreased eHf values relative to those of the UD and ST volcanoes.Our study highlights the significant contribution of recycled oceanic crust materials to the generation of the Quaternary magmas.
文摘Power-law patterns appear in a variety of natural systems on the modern Earth;nevertheless,whether such behaviors appeared in the deep-time environment has rarely been studied. Isotopic records in sedimentary rocks, which are widely used to reconstruct the geological/geochemical conditions in paleoenvironments and the evolutionary trajectories of biogeochemical cycles, offer an opportunity to investigate power laws in ancient geological systems. In this study, I focus on the Phanerozoic sedimentary records of carbon, oxygen, sulfur, and strontium isotopes, which have well documented and extraordinarily comprehensive datasets. I perform statistical analyses on these datasets and show that the variations in the sedimentary records of the four isotopes exhibit power-law behaviors. The exponents of these power laws range between 2.2 and 2.9;this narrow interval indicates that the variations in carbon, oxygen, sulfur, and strontium isotopes likely belong to the same universality class, suggesting that these systematic power-law patterns are governed by universal, scale-free mechanisms. I then derive a general form for these power laws from a minimalistic model based on basic physical principles and geosystem-specific assumptions, which provides an interpretation for the power-law patterns from the perspective of thermodynamics. The fundamental mechanisms regulating such patterns might have been ubiquitous in paleoenvironments, implying that similar power-law behaviors may exist in the sedimentary records of other isotopes.
文摘The oxygen isotopic data for amphibolites from Archaean continental nucleus, North China Craton indicate that ( i ) the evolving lines structured by the data are parallel to the geoselenic evolving line, which means that the parent materials of these continental nucleus o-riginated from solar matter; ( ii ) different intercepts for these evolving lines manifest that oxy-
基金the National Natural Science Foundation of China (Grant Nos40676005 and 40406001)
文摘During the 22nd Chinese Antarctic Research Expedition (CHINARE-22), the atmospheric gas samples above the oceanic surface and near the surface were collected on the track for the scientific ship "Xuelong" and on Millor Peninsula of eastern Antarctica, respectively, using the Tedlar gas bags. Every day the sampling times were 10:00 and 22:00 (local time), respectively. In the laboratory, high-precision measurement of the isotopic compositions for N2O in these gas samples was conducted using Thermo Finnigan MAT-253 Isotopic Mass Spectrometer with a fully automated interface for the pre-GC concen-tration (PreCon) of trace gases. The temporal and spatial variations of δ 15N and δ 18O in atmospheric N2O were analyzed. The mean δ 15N and δ 18O-N2O values above the oceanic surface were (7.21±0.50)‰ and (44.52±0.52)‰, respectively. From 30°N to Antarctica, the δ 15N (6.05‰―7.88‰) linearly increased with the rate of about 0.01‰ with the latitude while the δ 18O (43.05‰―48.78‰) showed a large fluctua-tion. The δ 15N negatively correlated with air temperature and N2O concentration, and slightly positively correlated with δ 18O. The summertime variations of δ 15N and δ 18O-N2O appeared the same trend on Millor Peninsula of eastern Antarctica. They significantly positively correlated with each other and negatively with N2O concentration. The δ 15N and δ 18O-N2O at different sites averaged (7.42±0.35)‰ and (44.69±0.49)‰, respectively, slightly higher than those above the oceanic surface, significantly higher than those of atmospheric N2O in the low-latitude regions of Northern Hemisphere. The predominant factors affecting the spatial variations of δ 15N and δ 18O values were also discussed. The isotopic data given in this study can help to investigate the global and regional N2O budgets.
基金Project supported by the National Key R&D Program of China(No.2016YFD0200106)the National Natural Science Foundation of China(No.41571450)
文摘The denitrifier method is widely used as a novel pretreatment method for the determination of nitrogen and oxygen isotope ratios as it can provide quantitative and high-sensitivity measurements. Nevertheless, the method is limited by relatively low measurement accuracy for δ18 O. In this study, we analyzed the factors influencing the accuracy of δ18 O determination, and then systematically investigated the effects of dissolved oxygen concentrations and nitrate sample sizes on estimates of the δ15 N and δ18 O of nitrate reference materials. The δ18 O contraction ratio was used to represent the relationship between the measured difference and true difference between two reference materials. We obtained the following main results:(1) a gas-liquid ratio of 3:10(v/v) in ordinary triangular flasks and a shaking speed of 120 r/min produced an optimal range(1.9 to 2.6 mg/L) in the concentration of dissolved oxygen for accurately determining δ18 O, and(2) the δ18 O contraction ratio decreased as nitrate sample size decreased within a certain range(1.0 to 0.1 μmol). Our results suggested that δ18 O contraction is influenced mainly by dissolved oxygen concentrations in pure culture, and provided a model for improving the accuracy of oxygen isotope analysis.
