Despite the significant improvement on spatial resolution, NanoSIMS still preserves relatively high mass resolution, sensitivity, and analytical precision. It has become an important analytical platform to determine c...Despite the significant improvement on spatial resolution, NanoSIMS still preserves relatively high mass resolution, sensitivity, and analytical precision. It has become an important analytical platform to determine chemical compositions of solid materials, and has been widely used in space, earth, life, and materials sciences, etc. By using a Cs＋ ion beam with a size as small as 50 nm scanning over sample surfaces, we are able to obtain high spatial resolution images of up to 7 species simultaneously. When utilizing Faraday cup, high analytical precision of 0.3‰-0.5‰ （1SD） for C, O and S isotopic analysis can be achieved. Although this precision level is still lower than that of conventional SIMS, it already meets the major requirements of Earth Sciences. In 2011, the first NanoSIMS of China （Cameca NanoSIMS 50L） was installed at Institute of Geology and Geophysics, Chinese Academy of Sciences. Based on the working mechanism and analytical modes of the instrument, this paper will systematically introduce the analytical methods established with the NanoSIMS and their potential applications in earth sciences. These methods include trace element distribution images in mineral zoning, high spatial resolution （2-5/am） Pb-Pb and U-Pb dating, water content and H isotopic analysis for silicate glass and apatite, C isotopic analysis for diamond and graphite, O isotopic analysis for carbonate, S isotopic analysis for sulfides. In addition, the specific requirements for sample preparation will also be introduced in order to facilitate domestic earth scientists＇ use.展开更多
We conducted detailed studies of the Sinian carbonates from the Helan Mountain,Ningxia by both field investigation and laboratory analyses of carbon and oxygen isotopes.The carbon isotopic compositions of the Sinian Z...We conducted detailed studies of the Sinian carbonates from the Helan Mountain,Ningxia by both field investigation and laboratory analyses of carbon and oxygen isotopes.The carbon isotopic compositions of the Sinian Zhengmuguan Formation shows variations with regularity in the five studied sections,theδ13C values all gradually decrease from bottom to top,with a total range from 4.51‰to 0.11‰,and the biggest negative excursion reaches up to 6.88‰.In addition,abundant macro-body fossils were also found from the Tuerkeng Formation in this study,similar to those found from the Dengying Formation in the South China Block.This observation firmly constrained the age for the Zhengmuguan and Tuerkeng formations to the Sinian period.Here we interpreted that the Zhengmuguan Formation formed during a glacial period when the extremely cold climate substantially decreased the amount of burial of organic matter in the ocean and thus led to the general negativeδ13C excursion.The increasingδ13C values in the Tuerkeng Formation dolomites imply the ending of the glacial period in the Zhengmuguan epoch,biological recovery and increase of organic matter burial in the ocean occurred during this period.Comparing our obtained carbon and oxygen isotopes of the Zhengmuguan and Tuerkeng formations with those of coeval carbonate successions from other places all over the world,the Zhengmuguang-aged glacial deposits might be deposited after the Gaskiers glaciation.This study provides important information for paleo-ocean,paleogeographic and biological evolution in the North China Block during the Ediacaran period and adds new carbon and oxygen isotopes data for the global Sinian carbon-oxygen isotopes dataset.展开更多
Aluminum-rich chondrules （ARCs）, which share mineralogic and chemical properties with both Ca, Al-rich inclusions （CAIs） and ferromagnesian chondrules, play an important role in revealing their temporal and petrog...Aluminum-rich chondrules （ARCs）, which share mineralogic and chemical properties with both Ca, Al-rich inclusions （CAIs） and ferromagnesian chondrules, play an important role in revealing their temporal and petrogenetic relationships. In this work, seven ARCs were found in three ordinary chondrites GRV 022410 （H4）, GRV 052722 （H3.7） and Julesburg （L3.6）. They contain bulk Al2O3 - 17%-33% and exhibit igneous textures composed of olivine, high- and low-Ca pyroxene, plagioclase, spinel and glass. In situ SIMS analyses show that ARCs have oxygen isotopic compositions （δ18O=-6.1‰-7.1‰; δ17O= -4.5‰-5.1‰） close to ferromagnesian chondrules but far more depleted in 160 than CAIs （δ18O=-40‰; δ17O=-40‰）. Most ARCs plot close to the terrestrial mass fractionation （TF） line, and a few between the TF and carbonaceous chondrite anhydrous mixing （CCAM） lines. Plagioclase, nepheline and glass suffered O-isotopic exchanges during the metamorphism processes in the parent body. Spinel, olivine and pyroxene represent the primary O-isotopic compositions of ARCs, and define a fitted line with a slope of- 0.7±0.1. Compared with the results of previous studies, shallower slope as well as more depleted 160 compositions further demonstrates that ARCs in ordinary chondrites are not a simple mixing product of ferromagnesian chondrules and CAIs. Instead, they probably experienced higher-degree oxygen isotope exchange with a δ6O-poor nebular gas reservoir during multiple melting episodes.展开更多
In this study, with the method of vacuum extraction, two evaporative processes of soil water and free water under equilibrium condition were simulated. For each sample,water vapor was condensed by liquid nitrogen and ...In this study, with the method of vacuum extraction, two evaporative processes of soil water and free water under equilibrium condition were simulated. For each sample,water vapor was condensed by liquid nitrogen and was collected in four time intervals. From the analysis of hydrogen and oxygen isotopic compositions of the water collected at different times, it was discovered that the isotope fractionation of soil water also follows the mode, which is just the same as the evaporative process of free water. The relationship between the stable hydrogen and oxygen isotopes in residual water showed that the simulative evaporation line was close to the global meteoric water line (GMWL) under the equilibrium condition at about 20℃. Comparison of the two types of evaporative processes indicated that the isotope fractionation and evaporation velocity of soil water were only slightly modified by the Van der Waals force.展开更多
基金supported by the National Natural Science Foundation of China(Grants Nos.41173012,41103031,41230209,41322022,41221002)
文摘Despite the significant improvement on spatial resolution, NanoSIMS still preserves relatively high mass resolution, sensitivity, and analytical precision. It has become an important analytical platform to determine chemical compositions of solid materials, and has been widely used in space, earth, life, and materials sciences, etc. By using a Cs＋ ion beam with a size as small as 50 nm scanning over sample surfaces, we are able to obtain high spatial resolution images of up to 7 species simultaneously. When utilizing Faraday cup, high analytical precision of 0.3‰-0.5‰ （1SD） for C, O and S isotopic analysis can be achieved. Although this precision level is still lower than that of conventional SIMS, it already meets the major requirements of Earth Sciences. In 2011, the first NanoSIMS of China （Cameca NanoSIMS 50L） was installed at Institute of Geology and Geophysics, Chinese Academy of Sciences. Based on the working mechanism and analytical modes of the instrument, this paper will systematically introduce the analytical methods established with the NanoSIMS and their potential applications in earth sciences. These methods include trace element distribution images in mineral zoning, high spatial resolution （2-5/am） Pb-Pb and U-Pb dating, water content and H isotopic analysis for silicate glass and apatite, C isotopic analysis for diamond and graphite, O isotopic analysis for carbonate, S isotopic analysis for sulfides. In addition, the specific requirements for sample preparation will also be introduced in order to facilitate domestic earth scientists＇ use.
基金supported by China Geological Survey (1212011120552)
文摘We conducted detailed studies of the Sinian carbonates from the Helan Mountain,Ningxia by both field investigation and laboratory analyses of carbon and oxygen isotopes.The carbon isotopic compositions of the Sinian Zhengmuguan Formation shows variations with regularity in the five studied sections,theδ13C values all gradually decrease from bottom to top,with a total range from 4.51‰to 0.11‰,and the biggest negative excursion reaches up to 6.88‰.In addition,abundant macro-body fossils were also found from the Tuerkeng Formation in this study,similar to those found from the Dengying Formation in the South China Block.This observation firmly constrained the age for the Zhengmuguan and Tuerkeng formations to the Sinian period.Here we interpreted that the Zhengmuguan Formation formed during a glacial period when the extremely cold climate substantially decreased the amount of burial of organic matter in the ocean and thus led to the general negativeδ13C excursion.The increasingδ13C values in the Tuerkeng Formation dolomites imply the ending of the glacial period in the Zhengmuguan epoch,biological recovery and increase of organic matter burial in the ocean occurred during this period.Comparing our obtained carbon and oxygen isotopes of the Zhengmuguan and Tuerkeng formations with those of coeval carbonate successions from other places all over the world,the Zhengmuguang-aged glacial deposits might be deposited after the Gaskiers glaciation.This study provides important information for paleo-ocean,paleogeographic and biological evolution in the North China Block during the Ediacaran period and adds new carbon and oxygen isotopes data for the global Sinian carbon-oxygen isotopes dataset.
基金supported by the Natural Science Foundation of Jiangsu Province(Grant No.BK20131040)the National Natural Science Foundation of China(Grants Nos.41403056,41173076,41273079,41003026)the Minor Planet Foundation of China
文摘Aluminum-rich chondrules （ARCs）, which share mineralogic and chemical properties with both Ca, Al-rich inclusions （CAIs） and ferromagnesian chondrules, play an important role in revealing their temporal and petrogenetic relationships. In this work, seven ARCs were found in three ordinary chondrites GRV 022410 （H4）, GRV 052722 （H3.7） and Julesburg （L3.6）. They contain bulk Al2O3 - 17%-33% and exhibit igneous textures composed of olivine, high- and low-Ca pyroxene, plagioclase, spinel and glass. In situ SIMS analyses show that ARCs have oxygen isotopic compositions （δ18O=-6.1‰-7.1‰; δ17O= -4.5‰-5.1‰） close to ferromagnesian chondrules but far more depleted in 160 than CAIs （δ18O=-40‰; δ17O=-40‰）. Most ARCs plot close to the terrestrial mass fractionation （TF） line, and a few between the TF and carbonaceous chondrite anhydrous mixing （CCAM） lines. Plagioclase, nepheline and glass suffered O-isotopic exchanges during the metamorphism processes in the parent body. Spinel, olivine and pyroxene represent the primary O-isotopic compositions of ARCs, and define a fitted line with a slope of- 0.7±0.1. Compared with the results of previous studies, shallower slope as well as more depleted 160 compositions further demonstrates that ARCs in ordinary chondrites are not a simple mixing product of ferromagnesian chondrules and CAIs. Instead, they probably experienced higher-degree oxygen isotope exchange with a δ6O-poor nebular gas reservoir during multiple melting episodes.
基金supports provided by International Atomic Energy TC Project (No. PRC\08\015)the National Natural Science Founda-tion of China (No. 50579017)
文摘In this study, with the method of vacuum extraction, two evaporative processes of soil water and free water under equilibrium condition were simulated. For each sample,water vapor was condensed by liquid nitrogen and was collected in four time intervals. From the analysis of hydrogen and oxygen isotopic compositions of the water collected at different times, it was discovered that the isotope fractionation of soil water also follows the mode, which is just the same as the evaporative process of free water. The relationship between the stable hydrogen and oxygen isotopes in residual water showed that the simulative evaporation line was close to the global meteoric water line (GMWL) under the equilibrium condition at about 20℃. Comparison of the two types of evaporative processes indicated that the isotope fractionation and evaporation velocity of soil water were only slightly modified by the Van der Waals force.
