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How to estimate isotope fractionations of a Rayleigh-like but diffusion-limited disequilibrium process?

Acta Geochimica 2023年第1期42卷 24-37页

作者： Zi Xuan Guan Yun Liu School of Earth and Space Science Peking UniversityBeijing 100871China State Key Laboratory of Ore Deposit Geochemistry Institute of GeochemistryChinese Academy of SciencesGuiyang 550081China International center for planetary Science College of Earth ScienceChengdu University of TechnologyChengdu 610059China CAS center for excellence in comparative Planetology Hefei 230026China

The Rayleigh distillation isotope fractionation(RDIF) model is one of the most popular methods used in isotope geochemistry. Numerous isotope signals observed in geologic processes have been interpreted with this model. The RDIF model provides a simple mathematic solution for the reservoir-limited equilibrium isotope fractionation effect. Due to the reservoir effect, tremendously large isotope fractionations will always be produced if the reservoir is close to being depleted. However, in real situations, many prerequisites assumed in the RDIF model are often difficult to meet. For instance, it requires the relocated materials, which are removed step by step from one reservoir to another with different isotope compositions(i.e., with isotope fractionation), to be isotopically equilibrated with materials in the first reservoir simultaneously. This ‘‘quick equilibrium requirement’’ is indeed hard to meet if the first reservoir is sufficiently large or the removal step is fast. The whole first reservoir will often fail to re-attain equilibrium in time before the next removal *** problem led the RDIF model to fail to interpret isotope signals of many real situations. Here a diffusion-coupled and Rayleigh-like(i.e., reservoir-effect included) separation process is chosen to investigate this problem. We find that the final isotope fractionations are controlled by both the diffusion process and the reservoir effects via the disequilibrium separation process. Due to its complexity, we choose to use a numerical simulation method to solve this problem by developing specific computing codes for the working *** to our simulation results, the classical RDIF model only governs isotope fractionations correctly at the final stages of separation when the reservoir scale(or thickness of the system) is reduced to the order of magnitude of the quotient of the diffusivity and the separation rate. The RDIF model fails in other situations and the isotope fractionations

关键词： Isotope fractionation Reservoir isotope effect Rayleigh-like distillation process Diffusional isotope effect Numerical modeling Disequilibrium process

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Equilibrium mercury and lead isotope fractionation caused by nuclear volume effects in crystals

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Acta Geochimica 2021年第2期40卷 150-162页

作者： Sha Yang Yun Liu Department of Geological Engineering Qinghai University.Xining 810016China State Key Laboratory of Ore Deposit Geochemistry Institute of GeochemistryChinese Academy of SciencesGuiyang 550081China International center for planetary Science College of Earth SciencesChengdu University of TechnologyChengdu 610059China CAS center for excellence in comparative Planetology Hefei 230026China

To investigate equilibrium mercury(Hg)and lead(Pb)isotope fractionation caused by the nuclear volume effect(NVE)in crystals,the electron densities at nuclei(i.e.,|Ψ(0)|2)for Hg-or Pb-bearing crystalline compounds were investigated by using the relativistic spin orbit zeroth-order regular approximation(ZORA)method with a three-dimensional periodic boundary condition based on the density functional theory(DFT).Many isotope fractionation factors of crystalline compounds are provided for the first *** results show,even at1000℃,NVE-driven Hg and Pb isotope fractionation are meaningfully large,i.e.,range from 0.12‰to 0.49‰(202Hg/^(198)Hg),from-0.20‰to 0.17‰(208Pb/^(206)Pb)and from-0.08‰to 0.06‰(207Pb/^(206) Pb)relative to Hg0 vapor and Pb0 vapor,***,the fractionations range from-0.06‰to-0.20‰(208Pb/^(206)Pb)and from-0.02‰to-0.08‰(207Pb/^(206)Pb)for Pb2+-bearing species,from 0.10‰to 0.17‰(208Pb/^(206)Pb)and from 0.04‰to 0.06‰(207Pb/^(206)Pb)for Pb4+-bearing species in *** calculated Hg-bearing species in crystals will enrich heavier isotope(202Hg)relative to Hg0 ***,Pb4+-bearing species enrich heavier Pb isotopes(208Pb and 207Pb)than Pb^(2+)-bearing species in crystals,which the enrichment can be up to 0.37‰(208-Pb/^(206)Pb)and 0.14‰(207Pb/^(206)Pb)at 1000℃,due to their NVEs are in opposite *** NVE-driven MIFs of Hg isotopes,which are compared to the Hg202-Hg198baseline,are up to-0.158‰(ΔNV199Hg),-0.024‰(ΔNV200Hg)and-0.094‰(ΔNV201Hg)relative to Hg0 vapor at5000 *** all studied Hg-bearing species in crystals,the MIFs of two odd-mass isotopes(i.e.,ΔNV199Hg andΔNV201Hg)will be changed proportionally and their ratio(i.e.,ΔNV199Hg/ΔNV201Hg)will be a constant *** NVE can also cause mass-independent fractionations for 207Pb and 204 Pb compared to the baseline of 208Pb and *** largest NVEdriven MIFs are 0.043‰(ΔNV207Pb)and-0.040‰(ΔNV204Pb)among all the studied species relative to Pb0 vapor at 5000 *** magnit

关键词： Mercury and lead isotopes Crystals Nuclear volume effect DFT relativistic effect calculations

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Eco-environmental changes in the Chinese Loess Plateau during low-eccentricity interglacial Marine Isotope Stage 19

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Science China Earth Sciences 2020年第9期63卷 1408-1421页

作者： Yueting ZHANG Naiqin WU Fengjiang LI Qingzhen HAO Yajie DONG Dan ZHANG Houyuan LU Key Laboratory of Cenozoic Geology and Environment Institute of Geology and GeophysicsChinese Academy of SciencesBeijing 100029China College of Earth and planetary Sciences University of Chinese Academy of SciencesBeijing 100049China innovation Academy for Earth Science Chinese Academy of SciencesBeijing 100029China CAS center for excellence in Life and Paleoenvironment Beijing 100044China center for excellence in Tibetan Plateau Earth Science Chinese Academy of SciencesBeijing 100101China

Eco-environmental changes during interglacials with an astronomical background similar to that of the Holocene are potentially helpful for understanding the future climatic *** oxygen isotope stage(MIS)19 is similar to the Holocene in astronomical background,both being characterized by a low eccentricity of the Earth’s ***,MIS 19 has attracted research attention only recently and therefore less is known about eco-environmental changes during this interval,especially based on terrestrial *** the Chinese Loess Plateau(CLP),the S7 paleosol can provide valuable terrestrial paleoclimatic and paleoenvironmental record for MIS ***,high-resolution terrestrial snail records from the L8–L7 strata of the Huining,Xifeng and Luochuan sequences in the CLP were analyzed in order to characterize spatio-temporal changes in climate and eco-environment during MIS 20–*** results show that in all three sections the late part of MIS 20 was dominated by abundant cold-aridiphilous mollusc species,indicating that cold and dry climatic conditions prevailed across the entire CLP,under the strong influence of the winter *** mollusc fauna of MIS 19 were dominated by warmth-loving and thermohumidiphilous species that enable the definition of two climatic *** early part of MIS 19(~790–778 ka)was marked by warm and humid conditions,as evidenced by high abundances of warmth-loving and thermo-humidiphilous *** interval was slightly warmer than today and it lasted for^12 *** climate of the later part of MIS 19(~778–761 ka)was more moderate,and increased proportions of cold-aridiphilous and warmth-loving species were *** warmth of this period was similar to that of today,but the climatic fluctuations were *** the early part of MIS 18(~761–745 ka),the Xifeng and Luochuan sections in the eastern CLP still maintained high abundances of warmth-loving and thermo-humidiphilous species,indicating that the moderate climatic

关键词： Chinese loess-paleosol sequences Terrestrial mollusc fossils Low-eccentricity interglacial MIS 19 Climatic and environmental pattern

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Study of the Modified Gaussian Model on olivine diagnostic spectral features and its applications in space weathering experiments

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Research in Astronomy and Astrophysics 2020年第8期20卷 261-279页

作者： Hui-Jie Han Xiao-Ping Lu Ya-Zhou Yang Hao Zhang Admire Muchimamui Mutelo State Key Laboratory of Lunar and planetary Sciences Macao University of Science and TechnologyTaipa 999078MacaoChina State Key Laboratory of Space Weather National Space Science CenterChinese Academy of SciencesBeijing 100190China planetary Science Institute School of Earth SciencesChina University of GeosciencesWuhan 430074China CAS center for excellence in comparative Planetology Hefei 230026China School of Earth Science and Resources China University of GeosciencesBeijing 100083China

The absorption features of olivine in visible and near-infrared(VNIR)reflectance spectra are the key spectral parameters in its mineralogical ***,these spectral parameters can be obtained by exploiting the Modified Gaussian Model(MGM)with a proper continuum ***,different continua may change the deconvolution results of these *** paper investigates the diagnostic spectral features of olivine with diverse chemical *** different continuum removal methods with MGM for getting the deconvolution results are presented and the regression equations for predicting the Mg-number(Fo#)are *** results show that different continua superimposed on the mineral absorption features will make the absorption center shift,as well as the obvious alterations in shape,width and strength of the absorption ***,it is also found that the logarithm of a second-order polynomial continuum can match the overall shape of the spectrum in logarithmic space,and the improved regression equations applied to estimate the chemical composition of olivine-dominated spectra also have a better *** an application example,the improved approach is applied to pulse laser irradiated olivine grains to simulate and study the space weathering effects on olivine diagnostic spectral *** experiments confirm that space weathering can make the absorption band center shift toward longer ***,the Fo#estimated from remote sensing spectra may be less than its actual chemical *** results may provide valuable information for revealing the difference between the spectra of olivine grains and olivine-dominated asteroids.

关键词： techniques:spectroscopic instrumentation:spectrographs methods:statistical minor planets asteroids:general

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Geochronological and geochemical comparison of Precambrian meta-mafic volcanics in Zhongtiaoshan and Lüliangshan Regions in Shanxi, North China Craton

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Acta Geochimica 2021年第3期40卷 325-347页

作者： Baishun Shi Jianzhong Liu Yongquan Li Kai Zhu Li Zhang Junhao Hu Jingwen Liu College of Earth Sciences Jilin UniversityChangchun 1300611China center for Lunar and planetary Sciences Institute of GeochemistryChinese Academy of SciencesGuiyang 550081China School of Earth Science and Resources China University of GeosciencesBeijing 100083China College of Earth and planetary Sciences University of Chinese Academy of SciencesBeijing 100049China center for excellence in comparative Planetology Chinese Academy of SciencesHefei 230026China College of Urban and Rural Planning and Architectural Engineering Guiyang UniversityGuiyang 550005China

To unravel the geochemical heterogeneity and its origin in different terranes of North China,we conducted geochronological and geochemical analyses of the meta-mafic rocks from the Lüliang–Zhongtiao rift zone(Shanxi Province).LA-ICP-MS zircon U–Pb dating yielded mostly End-Neoarchean to Proterozoic ages for the basement rocks(Sushui Complex:2516±26 Ma;Metamafic rocks:2494±31 Ma),Jiangxian Group(~2213 Ma),Zhongtiao Group(2077±29 Ma),Jiehekou Group(1998±23 Ma),and Lüliang Group(2152±52 Ma).Petrographic characteristics show that the meta-mafic rocks from the Neoarchean–Paleoproterozoic Zhongtiaoshan(Sushui Complex)have similar geochemical characteristics to the overlying Jiangxian and Zhongtiao *** Paleoproterozoic Lüliang andYejishan Group meta-mafic rocks from Lüliangshan also have similar geochemical characteristics but are geochemically different from similar-age rocks from *** shows that the late-stage rocks have a geochemical inheritance from the early-stage rocks in the same region and that the geochemical heterogeneity of rocks from different areas was originated from the inherited heterogeneity of the magma source.

关键词： Geochemical heterogeneity Geochronological and geochemical Meta-mafic rocks Lüliang–Zhongtiao rift zone Neoarchean–Paleoproterozoic

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A MAVEN investigation of O++ in the dayside Martian ionosphere

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Earth and planetary Physics 2020年第1期4卷 11-16页

作者： Hao Gu Jun Cui ZhaoGuo He JiaHao Zhong State Key Laboratory of Lunar and planetary Sciences Macao University of Science and TechnologyMacao 999078China School of Atmospheric Sciences Sun Yat-sen UniversityZhuhai Guangdong 519082China Chinese Academy of Sciences center for excellence in comparative Planetology Hefei 230000China National Astronomical Observatories Chinese Academy of SciencesBeijing 100012China

O^++ is an interesting species in the ionospheres of both the Earth and Venus. Recent measurements made by the Neutral Gas and Ion Mass Spectrometer (NGIMS) on board the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft provide the first firm detection of O^++ in the Martian ionosphere. This study is devoted to an evaluation of the dominant O^++ production and destruction channels in the dayside Martian ionosphere, by virtue of NGIMS data accumulated over a large number of MAVEN orbits. Our analysis reveals the dominant production channels to be double photoionization of O at low altitudes and photoionization of O^+ at high altitudes, respectively, in response to the varying degree of O ionization. O^++ destruction is shown to occur mainly via charge exchange with CO2 at low altitudes and with O at high altitudes. In the dayside median sense, an exact balance between O^++ production and destruction is suggested by the data below 200 km. The apparent discrepancy from local photochemical equilibrium at higher altitudes is interpreted as a signature of strong O^++ escape on Mars, characterized by an escape rate of 6×10^22s^-1.

关键词： Mars ionosphere doubly ionized oxygen MAVEN

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Ground calibration of the Mars orbiter magnetometer onboard Tianwen-1

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Earth and planetary Physics 2023年第3期7卷 371-377页

作者： ManMing Chen Kai Liu XiaoWen Hu YiRen Li XinJun Hao ZongHao Pan School of Earth and Space Sciences University of Science and Technology of ChinaHefei 230026China Chinese Academy of Sciences center for excellence in comparative Planetology University of Science and Technology of ChinaHefei 230026China

Ground calibration experiments of the Mars orbiter magnetometer(MOMAG)onboard the orbiter of Tianwen-1 were performed to determine the sensitivity,misalignment angle,and offset of the *** linearity of the applied calibrated magnetic fields and the output from the sensors were confirmed to be better than 10^(-4),and the sensor axes were orthogonal to each other within 0.5 *** temperature dependencies of the sensitivity and misalignment angle were examined,but no clear signatures of temperature dependencies could be *** offset and the stability of sensor offset drift with a temperature change were also determined by the rotation *** stability of the sensor offset drift was less than 0.01 nT/℃.The ground calibration of MOMAG determines all the calibration parameters of the sensors for accurate magnetic field measurements in orbit with the appropriate corrections.

关键词： Mars orbiter magnetometer Tianwen-1 ground calibration

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An Experimental Study of Partial Melting of Metafelsic Rocks:Constraints on the Feature of Anatectic Melts and the Origin of Garnets in Collisional Orogens

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Journal of Earth Science 2022年第3期33卷 753-769页

作者： Xu Luo Qiong-Xia Xia Yong-Fei Zheng Wan-Cai Li CAS Key Laboratory of Crust-Mantle Materials and Environments School of Earth and Space SciencesUniversity of Science and Technology of ChinaHefei 230026China center of excellence in comparative Planetology Chinese Academy of Sciences(CAS)Hefei 230026China Department of Earth Environmental and Planetary SciencesCase Western Reserve UniversityCleveland OH 44106USA

Crustal anatexis in continental subduction zones has great bearing on chemical differentiation of the continental crust at convergent plate *** was experimentally investigated for ultrahigh-pressure(UHP)metafelsic rocks at 0.5-3.0 GPa and 650-900℃.The results show that partial melting begins at about 750℃ when pressure drops from 3.0 to 2.0 GPa,corresponding to decompressional exhumation of the deeply subducted continental *** the pressure further decreases to 1.0 GPa,the partial melting degree reaches the maximum of~25%at 900℃.Partial melts produced in these experiments are rich in silica and alkali,and poor in iron,manganese and *** the degree of partial melting increases,the composition of partial melts gradually converges toward homogeneous *** the absence of free water,the partial melting of metafelsic rocks were triggered by the breakdown of hydrous *** low temperatures of~750℃at 1.0-2.0 GPa,phengite dehydration melting occurs at first,giving rise to small amounts of felsic melts and peritectic *** the temperature rises up to 850-900℃,biotite begins to break down and gives rise to large amounts of felsic melts and peritectic minerals such as garnet,K-feldspar and *** is noted that peritectic garnet is much different from anatectic garnet crystallized from anatectic melts and metamorphic garnet formed through metamorphic dehydration reaction under subsolidus *** peritectic garnet is characterized not only by anhedral shapes with many multiphase crystal inclusions but also by compositions poor in spessartine and grossular but rich in almandine and *** the other hand,the anatectic garnets are characterized not only by euhedral shapes with few inclusions but also by compositions rich in grossular and spessartine but poor in almandine and *** observations provide experimental constraints on the origin of garnets in UHP metamorphic rocks,which have great bearing on understanding of

关键词： collisional orogen partial melting experimental petrology metafelsic rocks garnet melts

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Solar control of CO2^+ultraviolet doublet emission on Mars

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Earth and planetary Physics 2020年第6期4卷 543-549页

作者： ZiChuan Li Jun Cui Jing Li XiaoShu Wu JiaHao Zhong FaYu Jiang National Astronomical Observatories Chinese Academy of SciencesBeijing 100012China School of Astronomy and Space Sciences University of Chinese Academy of SciencesBeijing 100049China planetary Environmental and Astrobiological Research Laboratory(PEARL) School of Atmospheric SciencesSun Yat-Sen UniversityZhuhai Guangdong 519082China center for excellence in comparative Planetology Chinese Academy of SciencesHefei 230026China Lunar and planetary Laboratory University of ArizonaTucsonArizonaUSA

The CO2^+;ultraviolet doublet(UVD)emission near 289 nm is an important feature of dayside airglow emission from planetaryupper *** this study,we analyzed the brightness profiles of CO2^+;UVDemission on Mars by using the extensive observationsmade by the lmaging Ultraviolet Spectrograph on board the recent Mars Atmosphere and Volatle Evolution *** solar cycleand solar zenith angle variations in peak emission intensity and altitude were revealed by the data:(1)Both the peak intensity and altitude increase with increasing solar activity,and(2)the peak intensity decreases,whereas the peak altitude increases,with increasingsolar zenith *** observations can be favorably interpreted by the solar-driven scenario combined with the fact that photoionization and photoelectron impact ionization are the two most important processes responsible for the production of excited-state cotand consequently the intensity of CO2^+;*** this,we propose that an extra driver,presumably related to thecomplicated variation in the background atmosphere,such as the occurrence of globaldust storms is required to fuly interpret *** general,our analysis suggests that the CO2^+;UVD emission is a useful diagnostic of the variability of the dayside Martianatmosphere under the influences of both internal and external drivers.

关键词： Mars dayglow CO2^+ MAVEN

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Mesopause temperatures and relative densities at midlatitudes observed by the Mengcheng meteor radar

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Earth and planetary Physics 2023年第6期7卷 665-674页

作者： Wen Yi XiangHui Xue MaoLin Lu Jie Zeng HaiLun Ye JianFei Wu Chong Wang TingDi Chen Chinese Academy of Sciences Key Laboratory of Geospace Environment Department of Geophysics and Planetary SciencesUniversity of Science and Technology of ChinaHefei 230026China Mengcheng National Geophysical Observatory School of Earth and Space SciencesUniversity of Science and Technology of ChinaHefei 230026China Hefei National Laboratory for the Physical Sciences at the Microscale University of Science and Technology of ChinaHefei 230026China Chinese Academy of Sciences center for excellence in comparative Planetology Hefei 230026China Collaborative innovation center of Astronautical Science and Technology Harbin 150001China

The atmospheric temperatures and densities in the mesosphere and lower thermosphere(MLT)region are essential for studying the dynamics and climate of the middle and upper *** this study,we present more than 9 years of mesopause temperatures and relative densities estimated by using ambipolar diffusion coefficient measurements observed by the Mengcheng meteor radar(33.4°N,116.5°E).The intercomparison between the meteor radar and Thermosphere Ionosphere Mesosphere Energetics and Dynamics/Sounding of the Atmosphere by Broadband Emission Radiometry(TIMED/SABER)and Earth Observing System(EOS)Aura/Microwave Limb Sounder(MLS)observations indicates that the meteor radar temperatures and densities agree well with the simultaneous satellite *** variations dominate the mesopause temperatures,with the maximum during winter and the minimum during *** mesopause relative densities also show annual variations,with strong maxima near the spring equinox and weak maxima before the winter solstice,and with a minimum during *** addition,the mesopause density exhibits a structure similar to that of the zonal wind:as the zonal wind flows eastward(westward),the mesopause density decreases(increases).At the same time,the meridional wind shows a structure similar to that of the mesopause temperature:as the meridional wind shows northward(southward)enhancements,the mesopause temperature increases(decreases).Simultaneous horizontal wind,temperature,and density observations provide multiple mesospheric parameters for investigating mesospheric dynamics and thermodynamic processes and have the potential to improve widely used empirical atmospheric models.

关键词： meteor radar mesopause horizontal wind temperature density

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