The dual isotopes(N and O)of nitrate were measured using a denitrifier bacterial method in the western South China Sea(WSCS)during September 2015 to elucidate key information during N transformation in the lower eupho...The dual isotopes(N and O)of nitrate were measured using a denitrifier bacterial method in the western South China Sea(WSCS)during September 2015 to elucidate key information during N transformation in the lower euphotic zone(LEZ)-upper mesopelagic zone(UMZ,down to 500 m in this study)continuum,which is a vital sub-environment for marine N cycle and sequestration of atmospheric CO_(2)as well.The N isotopic composition(δ^(15)N)of nitrate generally decreased from 500 m toward the base of the euphotic zone(∼100 m),reaching a value of∼4.6‰(vs.air N_(2))at the base of the LEZ,suggesting the imprint of remineralization(nitrification)of isotopically light N from atmospheric source.Theδ^(15)N andδ18O of nitrate only generally conform to a 1:1 line at 50 m and 75 m,suggesting that nitrate assimilation is a dominant process to shape nitrate isotope signature in this light-limited and relatively N-replete lower part of the euphotic zone.The fractionation factors of N and O isotopes during nitrate fractionation(15εASSIM,18εASSIM)using a steady-state model were estimated to be 4.0‰±0.3‰and 5.4‰±0.3‰,respectively.The occurrence of nitrification at the base of the LEZ and most of the UMZ is corroborated by the decoupling ofδ^(15)N and the oxygen isotopic composition(δ18O)of nitrate.Our results will provide insights for better understanding N cycle in the South China Sea from a perspective of present and past.展开更多
In steady state the stable isotopic composition of nitrogenand oxygen in tropospheric N\-2O is balanced by isotopically light N\-2O emitted from soils and oceans and isotopically heavy N\-2O as a return flux from the ...In steady state the stable isotopic composition of nitrogenand oxygen in tropospheric N\-2O is balanced by isotopically light N\-2O emitted from soils and oceans and isotopically heavy N\-2O as a return flux from the stratosphere. However, no such balance was reached in calculations given by Kim and Craig (1993). Modifications have been made on their calculations based on the most recent reports on annual global emission of N\-2O. It is considered that the nitrogen and oxygen isotope budget in tropospheric N\-2O are approximately in balance if isotopic fractionation effects during the production of N\-2O in soils and furthermore this paper puts forward further evidence for validating the above results.展开更多
The putative Jambil meta-carbonatites of Swat,northern Pakistan,occur as discrete intrusions into the Proterozoic Manglaur Formation,which are difficult to be distinguished from nearby calc-silicate marble because bot...The putative Jambil meta-carbonatites of Swat,northern Pakistan,occur as discrete intrusions into the Proterozoic Manglaur Formation,which are difficult to be distinguished from nearby calc-silicate marble because both rock types experienced regional metamorphism during Himalayan orogenesis that resulted in similar mosaic textures and mineral assemblages.Carbonatites are often significant repositories of economic mineral resources and,therefore,are important to be distinguished from calc-silicate marble.We present new geochemical and geochronology data to distinguish between the two rock types and interpret the petrogenesis and tectonic evolution of the Jambil metacarbonatites.Whole rock chemical data from the Jambil meta-carbonatites show characteristically high rare earth element(REE),Sr contents and lack of negative Eu anomaly,consistent with average calcio-carbonatite values worldwide and an igneous origin.More than 0.5 wt.% SrO in the metacarbonatites and SrO> 0.15 wt.% in constituent rock forming calcite are discriminating signatures of the Jambil meta-carbonatites.Chemically,the Jambil meta-carbonatites are relatively depleted in Rb,Nb,Ta,Ti,Zr and Hf,relatively enriched in Ba,Th,Sr,and have a high LREE/HREE ratio when normalized to primitive mantle.Their carbon and oxygen isotope compositions vary from-3.5‰ to-4.3‰and from 9.7‰ to 12.3‰,respectively.These geochemical characteristics indicate generation of the carbonatites through small degree of partial melting from a carbonated eclogitic source.In-situ,U/Pb analysis of titanite indicates that the Jambil meta-carbonatites were emplacement at 438 ±3 Ma.When combined with regional geological observations,we interpret the emplacement of the Jambil metacarbonatites to have taken place during the Silurian back arc extension within greater Gondwana and mark a transition from a compressional tectonic regime,brought about by collision of microcontinental blocks along the northern margin of Gondwana,to post-orogenic extension in the waning stages of the pre-Himalayan Ordovician orogeny.Finally,in-situ ^(208)Pb/^(232)Th monazite dates(40.3-27.6Ma) extracted from the meta-carbonatites are consistent with the Cenozoic metamorphism of the area.展开更多
The recently discovered nitrate ore field in the Turpan-Hami Basin of western China represents an estimated resource of 2.5 billion tons, and is comparable in scale to the Atacama Desert super-scale nitrate deposit in...The recently discovered nitrate ore field in the Turpan-Hami Basin of western China represents an estimated resource of 2.5 billion tons, and is comparable in scale to the Atacama Desert super-scale nitrate deposit in Chile. The research on this area is rarely carried out, and the origin of the deposits remains uncertain. In this study, new methods were used to systematically analyze N and O isotopes in nitrate minerals collected from the Kumutage, Xiaocaohu, Wuzongbulak, Dawadi, Tuyugou, and Shaer ore deposits in the Turpan-Hami Basin. The data showed that the δ15NAir value ranges from 0.7‰ to 27.6‰, but mostly between 2‰ and 6‰, which was similar to atmospheric NO3-. The 18O was highly enriched with δ18OV-SMOW varying from 30.2‰ to 46.7‰. This differs from levels in deposits derived from microbial nitrogen fixation, but is similar to those in atmospheric nitrates. N and O isotopes data indicated that nitrate deposits in Turpan-Hami Basin must be the result of deposition of atmospheric nitrate particles. Although atmospheric nitrate particles are common, the nitrate deposits could form only under the condition of long-term extreme drought climate and very limited biological activity. This paper summarized the ore-forming mechanism of different types nitrate deposits based on their geological setting.展开更多
Potential energy surfaces and vibrational spectra for the four isotopomers ( 15 N 14 N 16 O, 14 N 15 N 16 O, 15 N 2 16 O and 15 N 2 18 O) of N 2O have been investigated with the vibrational self consistent field confi...Potential energy surfaces and vibrational spectra for the four isotopomers ( 15 N 14 N 16 O, 14 N 15 N 16 O, 15 N 2 16 O and 15 N 2 18 O) of N 2O have been investigated with the vibrational self consistent field configuration interaction method. It is shown that the isotopomers with the same end atom have similar values of the potential parameters, and that substitution with different end atoms can affect the potential obviously. The calculated vibrational levels are in good agreement with the observed values by the optimization of several potential parameters ( f (1) 1, f (0) 13 , f (1) 3) which are sensitive to isotopic substitutions.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
基金The National Natural Science Foundation of China under contract Nos 42076042 and 41721005the Science and Technology Basic Resources Investigation Program of China under contract No.2017FY201403.
文摘The dual isotopes(N and O)of nitrate were measured using a denitrifier bacterial method in the western South China Sea(WSCS)during September 2015 to elucidate key information during N transformation in the lower euphotic zone(LEZ)-upper mesopelagic zone(UMZ,down to 500 m in this study)continuum,which is a vital sub-environment for marine N cycle and sequestration of atmospheric CO_(2)as well.The N isotopic composition(δ^(15)N)of nitrate generally decreased from 500 m toward the base of the euphotic zone(∼100 m),reaching a value of∼4.6‰(vs.air N_(2))at the base of the LEZ,suggesting the imprint of remineralization(nitrification)of isotopically light N from atmospheric source.Theδ^(15)N andδ18O of nitrate only generally conform to a 1:1 line at 50 m and 75 m,suggesting that nitrate assimilation is a dominant process to shape nitrate isotope signature in this light-limited and relatively N-replete lower part of the euphotic zone.The fractionation factors of N and O isotopes during nitrate fractionation(15εASSIM,18εASSIM)using a steady-state model were estimated to be 4.0‰±0.3‰and 5.4‰±0.3‰,respectively.The occurrence of nitrification at the base of the LEZ and most of the UMZ is corroborated by the decoupling ofδ^(15)N and the oxygen isotopic composition(δ18O)of nitrate.Our results will provide insights for better understanding N cycle in the South China Sea from a perspective of present and past.
基金ThisprojectwasfinanciallysupportedbytheNationalNaturalScienceFoundationofChina! (No .498730 34 )
文摘In steady state the stable isotopic composition of nitrogenand oxygen in tropospheric N\-2O is balanced by isotopically light N\-2O emitted from soils and oceans and isotopically heavy N\-2O as a return flux from the stratosphere. However, no such balance was reached in calculations given by Kim and Craig (1993). Modifications have been made on their calculations based on the most recent reports on annual global emission of N\-2O. It is considered that the nitrogen and oxygen isotope budget in tropospheric N\-2O are approximately in balance if isotopic fractionation effects during the production of N\-2O in soils and furthermore this paper puts forward further evidence for validating the above results.
基金financial support from the National Centre of Excellence in Geology, University of Peshawar, Pakistan。
文摘The putative Jambil meta-carbonatites of Swat,northern Pakistan,occur as discrete intrusions into the Proterozoic Manglaur Formation,which are difficult to be distinguished from nearby calc-silicate marble because both rock types experienced regional metamorphism during Himalayan orogenesis that resulted in similar mosaic textures and mineral assemblages.Carbonatites are often significant repositories of economic mineral resources and,therefore,are important to be distinguished from calc-silicate marble.We present new geochemical and geochronology data to distinguish between the two rock types and interpret the petrogenesis and tectonic evolution of the Jambil metacarbonatites.Whole rock chemical data from the Jambil meta-carbonatites show characteristically high rare earth element(REE),Sr contents and lack of negative Eu anomaly,consistent with average calcio-carbonatite values worldwide and an igneous origin.More than 0.5 wt.% SrO in the metacarbonatites and SrO> 0.15 wt.% in constituent rock forming calcite are discriminating signatures of the Jambil meta-carbonatites.Chemically,the Jambil meta-carbonatites are relatively depleted in Rb,Nb,Ta,Ti,Zr and Hf,relatively enriched in Ba,Th,Sr,and have a high LREE/HREE ratio when normalized to primitive mantle.Their carbon and oxygen isotope compositions vary from-3.5‰ to-4.3‰and from 9.7‰ to 12.3‰,respectively.These geochemical characteristics indicate generation of the carbonatites through small degree of partial melting from a carbonated eclogitic source.In-situ,U/Pb analysis of titanite indicates that the Jambil meta-carbonatites were emplacement at 438 ±3 Ma.When combined with regional geological observations,we interpret the emplacement of the Jambil metacarbonatites to have taken place during the Silurian back arc extension within greater Gondwana and mark a transition from a compressional tectonic regime,brought about by collision of microcontinental blocks along the northern margin of Gondwana,to post-orogenic extension in the waning stages of the pre-Himalayan Ordovician orogeny.Finally,in-situ ^(208)Pb/^(232)Th monazite dates(40.3-27.6Ma) extracted from the meta-carbonatites are consistent with the Cenozoic metamorphism of the area.
基金supported by Basic Scientific Research Operation Cost of State-Leveled Public Welfare Scientific Research Courtyard (Grant No. K0926)National Natural Science Foundation of China (Grant Nos. 40543013, 40873003)Key Laboratory of Isotope Geology, Ministry of Land and Resources
文摘The recently discovered nitrate ore field in the Turpan-Hami Basin of western China represents an estimated resource of 2.5 billion tons, and is comparable in scale to the Atacama Desert super-scale nitrate deposit in Chile. The research on this area is rarely carried out, and the origin of the deposits remains uncertain. In this study, new methods were used to systematically analyze N and O isotopes in nitrate minerals collected from the Kumutage, Xiaocaohu, Wuzongbulak, Dawadi, Tuyugou, and Shaer ore deposits in the Turpan-Hami Basin. The data showed that the δ15NAir value ranges from 0.7‰ to 27.6‰, but mostly between 2‰ and 6‰, which was similar to atmospheric NO3-. The 18O was highly enriched with δ18OV-SMOW varying from 30.2‰ to 46.7‰. This differs from levels in deposits derived from microbial nitrogen fixation, but is similar to those in atmospheric nitrates. N and O isotopes data indicated that nitrate deposits in Turpan-Hami Basin must be the result of deposition of atmospheric nitrate particles. Although atmospheric nitrate particles are common, the nitrate deposits could form only under the condition of long-term extreme drought climate and very limited biological activity. This paper summarized the ore-forming mechanism of different types nitrate deposits based on their geological setting.
文摘Potential energy surfaces and vibrational spectra for the four isotopomers ( 15 N 14 N 16 O, 14 N 15 N 16 O, 15 N 2 16 O and 15 N 2 18 O) of N 2O have been investigated with the vibrational self consistent field configuration interaction method. It is shown that the isotopomers with the same end atom have similar values of the potential parameters, and that substitution with different end atoms can affect the potential obviously. The calculated vibrational levels are in good agreement with the observed values by the optimization of several potential parameters ( f (1) 1, f (0) 13 , f (1) 3) which are sensitive to isotopic substitutions.
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.
