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Revisiting the Mg isotopic systematics of siliciclastic components of sediments and sedimentary rocks:A new geochemical proxy of continental weathering in Earth's history

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Science China Earth Sciences 2024年第2期67卷 620-633页

作者： Tianzheng HUANG Bing SHEN Kangjun HUANG Meng NING Chao LI Jinzhuang XUE Yuanlin SUN Baoqi HUANG Key laboratory of Orogenic Belt and Crustal Evolution MOESchool of Earth and Space SciencesPeking UniversityBeijing100871China State Key laboratory of Continental Dynamics Shaanxi Key Laboratory of Early Life and EnvironmentsDepartment of GeologyNorthwest UniversityXi’an710069China Institute of Sedimentary Geology Chengdu University of TechnologyChengdu610059China Key laboratory of Rhenium-Osmium isotopic geochemistry Chinese Academy of Geological SciencesBeijing100037China

The Mg isotopic compositions of siliciclastic components(δ^(26)Mg_(sili))of sediments and sedimentary rocks have been commonly used to constrain the intensity of continental weathering,based on observations of,(1)an upward enrichment of26Mg in modern weathering profiles,(2)preferential uptake of26Mg in soil clays,and(3)general positive correlations between weathering intensities andδ^(26)Mg_(sili)***,not all weathering profiles display an upward increase ofδ^(26)Mg_(sili),and not all soil clays enrich in26Mg,complicating the interpretations ofδ^(26)Mg_(sili)data of sediments and sedimentary *** further explore the controls ofδ^(26)Mg_(sili)of sediments and sedimentary rocks,here we measuredδ^(26)Mg_(sili),mineralogical compositions and major element compositions of deep sea sediments from South China Sea(SCS)and carbonate rock samples from two late Paleozoic sections in South *** samples show decreasing trends of both normalized Mg concentration(Mgnorm)andδ^(26)Mg_(sili)values with the increase of weathering intensity,while SCS sediments samples do not show any correlation between Mgnormorδ^(26)Mg_(sili)values and weathering intensity.A three-stages weathering model is developed to explain the observed Mgnorm andδ^(26)Mg_(sili)*** the new model,weathering can be divided into three stages,(1)the preliminary weathering stage characterized by dissolution of primary minerals and formation of secondary clay minerals in saprolite,(2)the transitional stage with massive vermiculite and chlorite formation on the bottom of soil,and(3)the advanced stage showing dissolution of vermiculite and chlorite in the top of *** new model explains anδ^(26)Mg_(sili)increase and Mgnormdecrease with an increase weathering intensity in preliminary weathering stage and decrease of Mgnormandδ^(26)Mg_(sili)with increase weathering intensity in advanced weathering *** revised weathering model warrants the application of Mg isotope in the study of contin

关键词： Clay mineral chemical weathering CIA Soil Weathering model

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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

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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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Provenance and paleogeographic evolution of the Upper Paleozoic–Lower Mesozoic strata in northern Laos

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Journal of Earth Science 2024年

作者： Jingjie Jin Xin Qian Vongpaseuth Senebouttalath Yuzhi Zhang Yuejun Wang Guangdong Provincial Key Lab of geodynamics and Geohazards， School of Earth Sciences and Engineering， Sun Yat-sen University， and Southern Marine Science and Engineering Guangdong laboratory (Zhuhai) Ministry of Energy and Mines， Department of Geology and Minerals

The Late Paleozoic–Early Mesozoic sedimentary system of the Luang Prabang Paleotethyan back-arc basin in northern Laos is important for investigating sedimentary provenance， paleogeographic patterns， and the tectonic evolution of the Eastern Paleotethyan Ocean. This study presents systematic stratigraphy， petrology， geochemistry， and detrital zircon U–Pb–Hf isotopic analyses for the Late Carboniferous–Jurassic sedimentary strata on both sides of the Luang Prabang basin. Based on distinct stratigraphic ages and provenance characteristics， the clastic rock samples can be divided into four groups. The Group 1 Late Carboniferous–Early Permian samples from the western part of the basin yield detrital zircon age-peaks of ～348 and ～1425 Ma， with corresponding εHf(t) values ranging from -2.0 to +15.5 and +1.5 to +14， respectively. The age spectrum of Group 2 Late Carboniferous–Early Permian samples from the eastern part of the basin shows major age-peaks of ～287 and ～1860 Ma， with εHf(t) values of -5.9–-0.9 and -3.6–+4.2， respectively. Group 3 Late Permian–Triassic samples exhibit age-peaks of ～242 and ～1853 Ma， along with εHf(t) values of -0.7–+14.4 and -5.4–-1.8， respectively. Group 4 Middle–Late Jurassic samples yield age-peaks of ～237，～431，～813，～1833， and ～2460 Ma， lacking Late Devonian (413–345 Ma) detrital zircons. All these data collectively suggest that the Group 1 sample primarily originated from the Sukhothai Arc in western Indochina， Group 2 was from the Kontum and Truong Son in eastern Indochina， and Group 3 has a combined provenance of the Sukhothai， Kontum， and Truong Son. Regional comparisons suggest that the Jurassic provenance was mainly derived from South China， which was imported through the northern river system. Our data， combined with the regional angular unconformities between Jurassic continental strata and pre-Jurassic marine strata， suggest that the Luang Prabang basin transformed into a superimposed collisional retroforeland basin during the Ju

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Evolution of Diagenetic Fluid of the Dawsonite-Bearing Sandstone in the Jiyang Depression,Eastern China

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Journal of Ocean University of China 2024年第1期23卷 80-98页

作者： LI Fulai MA Wenkuan ZHANG Chun WANG Kaining National Key laboratory of Deep Oil and Gas China University of Petroleum(East China)Qingdao 266580China laboratory for Marine Mineral Resources Qingdao National Laboratory for Marine Science and TechnologyQingdao 266071China Shandong Geological Exploration Institute of China chemical Geology and Mine Bureau Jinan 250013China

Based on the petrology,isotope geochemistry and fluid inclusions analysis,we established the evolutionary mode of the diagenetic fluid of dawsonite-bearing sandstone in the Jiyang ***-bearing sandstone is characterized by double injection of CO_(2)and oil-gas in the Jiyang Depression that have experienced a relatively complex diagenetic fluid evolution *** diagenetic sequence of secondary minerals involves secondary enlargement of quartz,kaolinite,first-stage calcite,dawsonite,second-stage calcite,ferrocalcite,dolomite and *** charging in the dawsonite-bearing sandstone occurred at around 2.6–0 *** CO_(2)charging event occurred during Dongying tectonism,forming the Pingfangwang CO_(2)gas reservoir,which provided an abundant carbon source for dawsonite *** and oxygen isotopic compositions of dawsonite demonstrate that CO_(2)forming the dawsonite was of an inorganic origin derived from the mantle,and that water mediating the proc-ess during dawsonite precipitation was sequestered brine with a fluid temperature of 82℃.The evolutionary sequence of the diagenetic fluid in the dawsonite-bearing sandstone was:alkaline syngenetic fluids,weak alkaline fluids during organic acid forma-tion,acidic fluids in the early stage of CO_(2)injection,alkaline fluids in the late stage of CO_(2)injection,and weak alkaline fluids during oil and gas *** mode indicates an increase in-HCO_(3)because of the CO_(2)injection,and the loss of Ca^(2+)and Mg^(2+)due to the precipitation of carbonate ***,the evolutionary mode of diagenetic fluids is in good agreement with high HCO_(3)^(-),low Ca^(2+)and low Mg^(2+)composition of the present formation water in the dawsonite-bearing sandstone.

关键词： evolution of diagenetic fluid dawsonite CO_(2)injection and hydrocarbon charging mineral diagenetic sequence iso-topic geochemistry fluid inclusions

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Early Neoproterozoic Granite-Gneisses of the Junggar Alataw(Southeastern Kazakhstan):Age,Petrogenesis and Tectonic Implications

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Acta Geologica Sinica(English Edition) 2024年第1期98卷 67-82页

作者： Nadezhda KANYGINA Andrey TRETYAKOV Dmitriy ALEXEIEV Kirill DEGTYAREV Anfisa SKOBLENKO Natalia SOLOSHENKO Boris ERMOLAEV Geological Institute Russian Academy of SciencesMoscow 119017Russia A.N.Zavaritsky Institute of Geology and geochemistry Ural Branch of the Russian Academy of SciencesYekaterinburg 620016Russia

The combined petrographic,petrological,geochemical and geochronological study of the Neoproterozoic gneisses of the Sarychabyn and Baskan complexes of the Junggar Alataw of South Kazakhstan elucidate the Precambrian tectonic evolution of the Aktau–Yili *** is one of the largest Precambrian crustal blocks in the western Central Asian orogenic *** U-Pb single-grain zircon ages indicate that granite-gneisses formed from the same source and crystallised in the early Neoproterozoic ca.930–920 *** chemical composition of gneisses corresponds to A2-type *** whole-rock Nd isotopic characteristics(εNd(t)=−4.9 to−1.0 and TNd(DM-2st)=1.9 to 1.7 Ga)indicate the involvement of Paleoproterozoic crustal rocks in magma *** Neoproterozoic ca.930–920 Ma A-type granitoids in the Aktau–Yili terrane of South and Central Kazakhstan might reflect within-plate magmatism adjacent to the collisional belt or a local extension setting in back-arc areas of the continental arc.

关键词： granitoid magmatism geochemistry geochronology Sm-Nd isotope systematics Neoproterozoic Junggar Alataw Kazakhstan Central Asian orogenic belt

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Himalayas as a global hot spot of springtime stratospheric intrusions:Insight from isotopic signatures in sulfate aerosols

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Research in Cold and Arid Regions 2024年第1期16卷 5-13页

作者： Kun Wang ShiChang Kang Mang Lin PengFei Chen ChaoLiu Li XiuFeng Yin Shohei Hattori Teresa L.Jackson JunHua Yang YiXi Liu Naohiro Yoshida Mark HThiemens State Key laboratory of Cryospheric Science Northwest Institute of Eco-Environment and ResourcesChinese Academy of Sciences(CAS)LanzhouGansu 730000China State Key laboratory of Isotope geochemistry Guangzhou Institute of GeochemistryCASGuangzhouGuangdong 510640China University of Chinese Academy of Sciences Beijing 100049China International Center for Isotope Effects Research(ICIER) School of Earth Sciences and EngineeringNanjing UniversityNanjingJiangsu 210023China Frontiers Science Center for Critical Earth Material Cycling State Key Laboratory for Mineral Deposits ResearchSchool of Earth Sciences and EngineeringNanjing UniversityNanjingJiangsu 210023China Department of chemical Science and Engineering School of Materials and Chemical TechnologyTokyo Institute of Technology4259 Nagatsuta-choMidori-kuYokohamaKanagawa 226-8502Japan Department of Chemistry and Biochemistry University of California San DiegoLa JollaCA 92093-0021USA Earth-Life Science Institute Tokyo Institute of TechnologyMeguro-kuTokyo 152-8551Japan National Institute of Information and Communications Technology KoganeiTokyo 184-8795Japan

Downward transport of stratospheric air into the troposphere(identified as stratospheric intrusions)could potentially modify the radiation budget and chemical of the Earth's surface *** the highest and largest plateau on earth,the Tibetan Plateau including the Himalayas couples to global climate,and has attracted widespread attention due to rapid warming and cryospheric *** studies recognized strong stratospheric intrusions in the Himalayas but are poorly understood due to limited direct evidences and the complexity of the meteorological dynamics of the third ***^(35)S is a radioactive isotope predominately produced in the lower stratosphere and has been demonstrated as a sensitive chemical tracer to detect stratospherically sourced air mass in the planetary boundary ***,we report 6-month(April–September 2018)observation of^(35)S in atmospheric sulfate aerosols(^(35)SO_(4)^(2-))collected from a remote site in the Himalayas to reveal the stratospheric intrusion phenomenon as well as its potential impacts in this *** the sampling campaign,the^(35)SO_(4)^(2-)concentrations show an average of 1,070±980 atoms/m^(3).In springtime,the average is 1,620±730 atoms/m^(3),significantly higher than the global existing data measured so *** significant enrichments of^(35)SO_(4)^(2-)measured in this study verified the hypothesis that the Himalayas is a global hot spot of stratospheric intrusions,especially during the springtime as a consequence of its unique geology and atmospheric *** combined with the ancillary evidences,e.g.,oxygen-17 anomaly in sulfate and modeling results,we found that the stratospheric intrusions have a profound impact on the surface ozone concentrations over the study region,and potentially have the ability to constrain how the mechanisms of sulfate oxidation are affected by a change in plateau atmospheric properties and *** study provides new observational constraints on stra

关键词： Himalayas Stratospheric intrusions Cosmogenic^(35)SO_(4)^(2-) Ozone Atmospheric oxidation

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Fractal Analysis of Lineaments in Equatorial Africa: Insights on Lithospheric Structure

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Open Journal of Geology 2013年第3期3卷 157-168页

作者： Collin Nkono Olivier Féménias Annick Lesne Jean-Claude Mercier Daniel Demaiffe isotopic geochemistry and chemical geodynamics laboratory DSTE (CP 160/02) Université Libre de Bruxelles (ULB) Bruxelles Belgique

In this paper, the complexity in the spatial distribution of the lineaments was investigated from on remote sensing topographic (SRTM DEM) and multispectral (Landsat) data. Lineaments in equatorial Africa were chosen to apply the fractal analysis methodology. The good correlations of the obtained data with some geophysical data from the same area allow that the complexity in the spatial distribution of the lineaments can give qualitative information on the interior of the earth (or on other planets). This method can provide a bridge between classical geology and geophysics, and particularly powerful for studying large and inaccessible regions.

关键词： Lineament Fractal Analysis SRTM Equatorial Africa

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Sedimentary and Geochemical Characteristics of Sinian Cap Carbonates in the Upper Yangtze Region

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Chinese Journal Of geochemistry 2003年第4期22卷 320-329页

作者：杨瑞东王世杰董丽敏姜立君张卫华高慧 The State Key laboratory of Environmental geochemistry Institute of Geochemistry Guizhou University of Technology

A global\|scale glaciation occurred at about 600 Ma ago. As a result, the Earth became the "Snowball Earth". The glaciation came to the end abruptly when atmospheric carbon dioxide increased to such an extent as to be about 350 times the modern level because of subaerial volcanic degassing. The rapid termination of glaciation would have led to warming of the Snowball Earth and extreme greenhouse conditions would have been created. The transfer of atmospheric carbon dioxide to oceans would give rise to the rapid precipitation of calcium carbonate in warm surface seawaters, thus forming the cap carbonate rocks as observed worldwide today.\; Regionally persisting, thin layers of carbonate rocks directly and ubiquitously overlie Proterozoic glacial deposits almost on every continent, and are commonly referred to as cap carbonates. Their unusual litho\| fabrics, stratigraphically abrupt basal and upper\|level contacts and strongly negative carbonate isotopic signatures (\{δ\{\}\+\{13\}C\-\{carb.\}\} values range from -7.0‰-0‰) suggest a chemical oceanographic origin, the details of which remain unknown. It is proposed that these enigmatic deposits are related to the destabilization of gaseous hydrate in terrestrial permafrost following rapid postglacial warming and flooding of widely exposed continental shelves and internal basins.\; The authors carried out studies on the geochemistry, sedimentology and palaeontology of the Sinian cap carbonates in Guizhou and Hunan provinces, including the occurrence of cap carbonates of unusual fabrics, strongly negative carbon isotopic signatures, and a lot of bitumen nodules. From the results it is suggested that the cap carbonates were formed from solid methane seepage, and it is in agreement with Kennedy’s viewpoint (2001) that the cap carbonates resulted from the rapid precipitation of calcium carbonate in response to solid methane seepage.

关键词： litho-fabrics geochemistry cap carbonate Sinian Upper Yangtze region

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isotopic geochemistry of Cadmium:A Review

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Acta Geologica Sinica(English Edition) 2015年第6期89卷 2048-2057页

作者： ZHU Chuanwei WEN Hanjie ZHANG Yuxu LIU Yizhang WEI Rongfei State Key laboratory of Ore Deposit geochemistry Institute of GeochemistryChinese Academy of Sciences State Key laboratory of Environmental geochemistry Institute of GeochemistryChinese Academy of Sciences Center for Environment Remediation Institute of Geographic Sciences and Natural Resources ResearchChinese Academy of Sciences

Cadmium（Cd） is a scarce, but not an extremely rare element in the Earth＇s crust（crustal average： 0.2 ppm Cd）. Geochemically, Cd exhibits thiophile, lithophile, and volatile behavior in different geologic processes. Biologically, it is a nutrient-like element that is closely related to P and Zn and is toxic element to organisms. Presently, Cd isotopes have been successfully utilized to trace Cd sources and nutrient cycling in marine systems in addition to unearthing other geochemical processes. Using published studies and our recent work, this survey summarizes the chemical preparation and mass spectrometry of Cd isotopes. It also reviews Cd isotopic compositions and fractionation mechanisms in nature as well as experiments.

关键词： Cadmium non-traditional stable isotopes stable isotopic fractionation geochemical tracer

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