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The influence of silica on reaction rates and molecular hydrogen(H_(2))generation during olivine hydrothermal alteration

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Science China Earth Sciences 2024年第1期67卷 222-233页

作者： Ruifang HUANG Weidong SUN Xing DING Yusheng ZHAO Yibing LI Xiuqi SHANG cas key laboratory of Ocean and Marginal Sea Geology South China Sea Institute of OceanologyChinese Academy of SciencesGuangzhou 510301China SUSTech Academy for Advanced Interdisciplinary Studies Southern University of Science and TechnologyShenzhen 518055China Center of Deep Sea Research Institute of OceanologyChinese Academy of SciencesQingdao 266071China State key laboratory of isotope geochemistry Guangzhou Institute of GeochemistryChinese Academy of SciencesGuangzhou 510640China Institue of Geology Chinese Academy of Geological SciencesBeijing 100037China

Hydrothermal alteration of olivine greatly influences geodynamics and the recycling of volatiles(such as water and carbon)in subduction *** is an important component of geological fluids,and its influence on the hydrothermal alteration of olivine remains poorly *** this study,we performed experiments at 300–515℃ and 3.0 kbar(1 bar=10^(5)Pa)by reacting well homogenized mixtures of olivine and silica powders with saline solutions(0.5 mol L^(−1)NaCl).Silica greatly influences the reaction pathways,reaction rates,and molecular hydrogen(H_(2))formation during olivine hydrothermal *** experiments at 300℃ and 3.0 kbar with mixtures of olivine and 10 wt%silica,olivine was replaced by serpentine and *** proportions of serpentine and talc were determined according to standard curves based on infrared spectroscopy *** 6.5%serpentine and 12%talc were produced after an experimental duration of 7 days,which had no change after a longer period(14 days).Compared to the kinetics in silica-free systems,the rates of olivine hydrothermal alteration in experiments with 10 wt%silica are much *** overall reaction is:4.5Forsterite+5.5SiO_(2),aq+4H_(2)O=Serpentine+*** the addition of more silica(20 wt%and 40 wt%),olivine was transformed into *** rates of reaction were much faster,e.g.,for experiments with olivine and 20 wt%silica,43%of talc was produced after 14 days,which increased to 77%for experiments with 40 wt%silica over the same *** overall reaction is:3Forsterite+5SiO_(2),aq+2H_(2)O=*** experiments at 400–505℃ and 3.0 kbar,the promoting effect of silica on olivine hydrothermal alteration was also observed,which is closely associated with a decrease in Gibbs free energies of olivine hydrothermal *** 300℃ and 3.0 kbar,silica decreased H_(2)formed during olivine hydrothermal alteration by around an order of magnitude,resulting in an increase in oxygen *** on measured H_(2),we calibrated ox

关键词： Olivine hydrothermal alteration Silica Serpentinization Hydrogen Serpentine

Rebuilding the theory of isotope fractionation for evaporation of silicate melts under vacuum condition

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Acta Geochimica 2024年第4期43卷 661-676页

作者： Jie Wang Yun Liu Research Center for Planetary Science College of Earth and Planetary SciencesChengdu University of TechnologyChengdu 610059China State key laboratory of Ore Deposit geochemistry Institute of GeochemistryChinese Academy of SciencesGuiyang 550081China cas Center for Excellence in Comparative Planetology Hefei 230026China

isotope eff ects are pivotal in understanding silicate melt evaporation and planetary accretion *** on the Hertz-Knudsen equation,the current theory often fails to predict observed isotope fractionations of laboratory experiments due to its oversimplified ***,we point out that the Hertz-Knudsen-equation-based theory is incomplete for silicate melt evaporation cases and can only be used for situations where the vaporized species is identical to the one in the *** propose a new model designed for silicate melt evaporation under *** model considers multiple steps including mass transfer,chemical reaction,and *** derivations reveal a kinetic isotopic fractionation factor(KIFF orα)αour model=[m(^(1)species)/m(^(2)species)]^(0.5),where m(species)is the mass of the reactant of reaction/nucleation-limiting step or species of diffusion-limiting step and superscript 1 and 2 represent light and heavy isotopes,*** model can eff ectively reproduce most reported KIFFs of laboratory experiments for various elements,i.e.,Mg,Si,K,Rb,Fe,Ca,and ***,the KIFF-mixing model referring that an overall rate of evaporation can be determined by two steps jointly can account for the eff ects of low P_(H2)pressure,composition,and *** addition,we find that chemical reactions,diffusion,and nucleation can control the overall rate of evaporation of silicate melts by using the fitting slope in ln(−ln f)versus ln(t).Notably,our model allows for the theoretical calculations of parameters like activation energy(E_(a)),providing a novel approach to studying compositional and environmental eff ects on evaporation processes,and shedding light on the formation and evolution of the proto-solar and Earth-Moon systems.

关键词： Evaporation Kinetic isotopic fractionation Chemical kinetics Hertz-Knudsen equation CAIS

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Scientific objectives and payload configuration of the Chang'E-7 mission

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National Science Review 2024年第2期11卷 285-300页

作者： Chi Wang Yingzhuo Jia Changbin Xue Yangting Lin Jianzhong Liu Xiaohui Fu Lin Xu Yun Huang Yufen Zhao Yigang Xu Rui Gao Yong Wei Yuhua Tang Dengyun Yu Yongliao Zou State key laboratory of Space Weather National Space Science Center Chinese Academy of Sciences National Space Science Center Chinese Academy of Sciences Institute of Geology and Geophysics Chinese Academy of Sciences Institute of geochemistry Chinese Academy of Sciences Shandong Provincial key laboratory of Optical Astronomy and Solar-Terrestrial Environment School of Space Science and Physics Institute of Space SciencesShandong University Institute of Drug Discovery Technology Ningbo University State key laboratory of isotope geochemistry Guangzhou Institute of Geochemistry Chinese Academy of Sciences School of Earth Science and Engineering Sun Yat-sen University Lunar Exploration and Space Engineering Center China Aerospace Science and Technology Corporation

As the cornerstone mission of the fourth phase of the Chinese Lunar Exploration Program, Chang'E-7(CE-7) was officially approved, and implementation started in 2022, including a main probe and a communication relay satellite. The main probe, consisting of an orbiter, a lander, a rover and a mini-flying probe, is scheduled to be launched in 2026. The lander will land on Shackleton crater's illuminated rim near the lunar south pole, along with the rover and mini-flying probe. The relay satellite(named Queqiao-2) will be launched in February 2024 as an independent mission to support relay communication during scientific exploration undertaken by Chang'E-4, the upcoming Chang'E-6 in 2024 and subsequent lunar *** CE-7 mission is mainly aimed at scientific and resource exploration of the lunar south pole. We present CE-7's scientific objectives, the scientific payloads configuration and the main functions for each scientific payload with its key technical specifications.

关键词： Chang’ E-7 scientific objectives scientific payloads

Multiple Uplift and Exhumation of the Southeastern Tibetan Plateau:Evidence from Low-Temperature Thermochronology

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Acta Geologica Sinica(English Edition) 2024年第3期98卷 569-584页

作者： WU Limin PENG Touping FAN Weiming ZHAO Guochun GAO Jianfeng DONG Xiaohan PENG Shili MIN Kang Tin Aung MYINT State key laboratory of isotope geochemistry Guangzhou Institute of GeochemistryChinese Academy of SciencesGuangzhou 510640China Chinese Academy of Sciences Center for Excellence in Deep Earth Science Guangzhou 510640China University of Chinese Academy of Sciences Beijing 100049China Chinese Academy of Sciences Center for Excellence in Tibetan Plateau Earth Sciences Beijing 100101China Department of Earth Sciences The University of Hong KongHong Kong 999077China State key laboratory of Ore Deposit geochemistry Institute of GeochemistryChinese Academy of SciencesGuiyang 550081China Southern Marine Science and Engineering Guangdong laboratory(Zhuhai) ZhuhaiGuangdong 519085China Department of Geology University of MandalayMandalay 05011Myanmar

Since the Cenozoic,the Tibetan Plateau has experienced large-scale uplift and outgrowth due to the India-Asia ***,the mechanism and timing of these tectonic processes still remain ***,using apatite fission track dating and inverse thermal modeling,we explore the mechanism of different phases of rapid cooling for different batholiths and intrusions in the southeastern Tibetan *** contrast to previous views,we find that the coeval granitic batholith exposed in the same tectonic zone experienced differential fast uplift in different sites,indicating that the present Tibetan Plateau was the result of differential uplift rather than the entire lithosphere uplift related to lithospheric collapse during Cenozoic *** addition,we also suggest that the 5-2 Ma mantle-related magmatism should be regarded as the critical trigger for the widely coeval cooling event in the southeastern Tibetan Plateau,because it led to the increase in atmospheric CO_(2)level and a hotter upper crust than before,which are efficient for suddenly fast rock weathering and ***,we propose that the current landform of the southeastern Tibetan Plateau was the combined influences of tectonic and climate.

关键词： apatite fission track rapid cooling differential uplift magmatism southeastern Tibetan Plateau

The photosynthetic oxygen evolution does not exclude the important role and contribution of bicarbonate photolysis

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Acta Geochimica 2024年第1期43卷 174-179页

作者： Yanyou Wu Shaogang Guo State key laboratory of Environmental geochemistry Institute of GeochemistryChinese Academy of SciencesGuiyang 550081People’s Republic of China University of Chinese Academy of Sciences Beijing 100049People’s Republic of China

Photosynthesis is the most important biochemical reaction on Earth. It has co-evolved and developed with the Earth, driving the biogeochemical cycle of all elements on the planet and serving as the only chemical process in nature that can convert light energy into chemical energy. Some heavy oxygen isotopic(^(18)O) labeling experiments have"conclusively" demonstrated that the oxygen released by photosynthesis comes only from water and are written into textbooks. However, it is not difficult to find that bicarbonate has never been excluded from the direct substrate of photosynthesis from beginning to end during the history of photosynthesis research. No convincing mechanism can be used to explain photosynthetic oxygen evolution solely from water photolysis. The bicarbonate effect, the Dole effect, the thermodynamic convenience of bicarbonate photolysis, the crystal structure characteristics of photosystem Ⅱ, and the reinterpretation of heavy oxygen isotopic labeling(^(18)O)experiments all indicate that the photosynthetic oxygen evolution does not exclude the important role and contribution of bicarbonate photolysis. The recently proposed view that bicarbonate photolysis is the premise of water photolysis, bicarbonate photolysis and water photolysis work together with a 1:1(mol/mol) stoichiometric relationship, and the stoichiometric relationship between oxygen and carbon dioxide released during photosynthetic oxygen evolution is also 1:1, has excellent applicability and objectivity, which can logically and reasonably explain the precise coordination between light and dark reactions during photosynthesis, the bicarbonate effect, the Dole effect, the Kok cycle and the neutrality of water and carbon in *** is of great significance for constructing the bionic artificial photosynthetic reactors and scientifically answering the question of the source of elemental stoichiometric relationships in nature.

关键词： Bicarbonate effect Dole effect Kok cycle Heavy oxygen isotope Artificial photosynthetic reactor

Altered oceanic crust source for the alkaline rocks with superchondritic Nb/Ta ratios due to the steep subduction

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Journal of Earth Science 2024年

作者： Xu Zhao Ning-Bo Li He-Cai Niu Shu-Cheng Tan Department of Geology， School of Earth Sciences， Yunnan University cas key laboratory of Mineralogy and Metallogeny， Guangzhou Institute of geochemistry， Chinese Academy of Sciences cas Center for Excellence in Deep Earth Science

The cause resulting in alkaline rocks with superchondritic Nb/Ta ratios remains a geochemical enigma. This paper present zircon and apatite geochronology， mineralogy， geochemistry， and Nd-Hf-Zn isotope investigation on the Ejinao nepheline syenite from South China to constrain the petrogenesis of alkaline rocks. The occurrence of alkaline minerals， including alkaline feldspar， arfvedsonite， and nepheline， indicate an alkaline feature of the Ejinao nepheline syenite. Zircon and apatite from the rock show U-Pb concordia age of 135.4±0.9 Ma and 137.5±5.8Ma， respectively， suggesting generation in the Early Cretaceous. The rock is characterized by low MgO （0.17 wt.%–0.26 wt.%） contents， but high Fe2O3T（4.66 wt.%–6.16 wt.%） and total alkalis (Na2O + K2O = 12.1 wt.%–13.1 wt.%) contents， consistent with the melts from subducting oceanic crust rather than mantle peridotite. The rock has low TiO2（0.13 wt.%–0.21 wt.%） contents and superchondritic Nb/Ta and Zr/Hf ratios， resulting from rutile residue in the source area. The εNd（t）（-1.35 to -1.09）， εHf（t）（-3.03 to -1.52）， and δ66Zn （0.32‰ to 0.34‰） values of the nepheline syenite manifest the involvement of 15%–20% carbonate-bearing sediments in the altered oceanic crust. Geochemical modeling further reveals that the nepheline syenite was sourced from 10%–20% melting of such a source. This superchondritic Nb/Ta nepheline syenite was generated during the steep subduction of the Paleo-Pacific Ocean， which is needed to bring oceanic slab to a hot mantle and resulted in the altered oceanic crust melting. Our study highlights that the altered oceanic crust represents a novel source for superchondritic Nb/Ta alkaline rocks.

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Nuclear volume effects in kinetic isotope fractionation:A case study of mercury oxidation by chlorine species

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Acta Geochimica 2024年第3期43卷 411-423页

作者： Chenlu Yang Yining Zhang Yun Liu Research Center for Planetary Science College of Earth and Planetary SciencesChengdu University of TechnologyChengdu 610059China State key laboratory of Ore Deposit geochemistry Institute of GeochemistryChinese Academy of SciencesGuiyang 550081China

It is well-known that the equilibrium isotope fractionation of mercury(Hg)includes classical massdependent fractionations(MDFs)and nuclear volume effect(NVE)induced mass-independent fractionations(MIFs).However,the effect of the NVE on these kinetic processes is not *** total fractionations(MDFs+NVEinduced MIFs)of several representative Hg-incorporated substances were selected and calculated with ab initio calculations in this work for both equilibrium and kinetic ***-induced MIFs were calculated with scaled contact electron densities at the nucleus through systematic evaluations of their accuracy and errors using the Gaussian09 and DIRAC19 packages(named the electron density scaling method).Additionally,the NVE-induced kinetic isotope effect(KIE)of Hg isotopes are also calculated with this method for several representative Hg oxidation reactions by chlorine *** KIEs for 202 Hg/^(198)Hg ranging from−2.27‰to 0.96‰are *** anomalous^(202)Hg-enriched KIEs(δ^(202)Hg/^(198)Hg=0.83‰,0.94‰,and 0.96‰,)caused by the NVE are observed,which are quite different from the classical view(i.e.,light isotopes react faster than the heavy ones).The electron density scaling method we developed in this study can provide an easier way to calculate the NVE-induced KIEs for heavy isotopes and serve to better understand the fractionation mechanisms of mercury isotope systems.

关键词： Nuclear volume effect Kinetic fractionation Hg isotopes Ab initio calculations

A novel model of the carbon cycle in the Cambrian ocean

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Science China Earth Sciences 2024年第6期67卷 1759-1778页

作者： Huajian WANG Shuichang ZHANG Xiaomei WANG Jin SU Yuntao YE Yuke LIU key laboratory of Petroleum geochemistry Research Institute of Petroleum Exploration and DevelopmentChina National Petroleum CorporationBeijing 100083China key laboratory of Orogenic Belts and Crustal Evolution School of Earth and Space SciencesPeking UniversityBeijing 100871China

The classic model of the carbon cycle suggests that the extensive burial of ^(12)C-enriched organic carbon leads to a positive carbon isotope(δ^(13)C)excursion(CIE),while massive oxidation of organic carbon results in a negative ***,global events such as the BAsal Cambrian Carbon isotope Excursion(BACE)and the Steptoean Positive Carbon isotope Excursion(SPICE)are global negative and positive δ^(13)C excursions,respectively,and they also exhibit significant organic carbon burial anomalies,displaying decoupling between carbon isotope anomalies and organic carbon *** on the analyses of the Cambrian carbon cycle and paleoceanographic evolution records from well Tadong2 in the Tarim Basin,we propose a novel model of the carbon cycle in the Cambrian ocean that incorporates oceanic dissolved organic carbon(DOC).Our findings are as follows.(1)The Cambrian ocean maintained substantial DOC reservoirs,which were regulated by ocean currents and paleo-redox conditions and exerted significant influence on the oceanic carbon cycle.(2)The oxidation of the oceanic DOC reservoirs during the early Cambrian led to the BACE and the Asian Phenomenon of the Cambrian petroleum systems,while the expansion of the oceanic DOC reservoirs during the SPICE resulted in a global positive δ^(13)C excursion and the absence of significant organic carbon burial.(3)The deep-basin sedimentary environment in the eastern depression of the Tarim Basin may have fostered the development of organic-rich black shales during the Furongian Series,corresponding to organic carbon burial during the SPICE and representing potential prospects for ultra-deep oil and gas *** research should focus on the formation mechanism,reserve scale,and influencing factors of the oceanic DOC reservoirs,as well as their resource and environmental *** is expected that new breakthroughs will be made in the fields of Earth system science and oil and gas exploration.

关键词： Carbon isotope Organic carbon BACE SPICE Dissolved organic carbon Climate change Black shale

South China Sea Typhoon Hagibis enhanced Xinfengjiang Reservoir seismicity

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Earthquake Science 2024年第3期37卷 210-223页

作者： Peng Zhang Xinlei Sun Yandi Zeng Zhuo Xiao Runqing Huang State key laboratory of isotope geochemistry Guangzhou Institute of GeochemistryGuangzhou 510640China University of Chinese Academy of Sciences Beijing 100049China College of Geosciences Chengdu University of TechnologyChengdu 610059China College of Artificial Intelligence Guangxi Minzu UniversityNanning 530006China

There was an evident increase in the number of earthquakes in the Xinfengjiang Reservoir from June to July 2014 after the landing of Typhoon *** understand the spatial and temporal evolution of this microseismicity,we built a high-precision earthquake catalog for 2014 and relocated 2275 events using recently developed methods for event picking and catalog *** occurred in the southeastern part of the reservoir,with the preferred fault plane orientation aligned along the Heyuan *** total seismic energy peaked when the typhoon passed through the reservoir,and seismicity correlated with typhoon *** contrast,a limited seismic response was observed during the later Typhoon *** data regarding the water level in the Xinfengjiang Reservoir and seismicity frequency changes in the Taiwan region during these two typhoon events,we suggest that typhoon activity may increase microseism energy by impacting fault stability around the Xinfengjiang *** a fault can be activated also depends on how close the stress accumulation is to its failure point.

关键词： typhoon seismicity analysis earthquake detection spatio-temporal evolution characteristics microseisms