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| 1 | The multistage genesis of the giant Dongshengmiao Zn-Pb-Cu deposit in western Inner Mongolia,China:Syngenetic stratabound mineralization and metamorphic remobilization显示文摘The genesis of the giant Dongshengmiao in the northern margin of the North China Block has been debated since its discovery in the 1950 s,because it shows geological and geochemical characteristics with both syngenetic and epigenetic signatures.It has geological settings and sulfur and lead isotopic compositions that are similar with typical SEDEX(sedimentary exhalative) deposit,while the Zn-Pb-Cu mineralization was controlled by shear deformation and metamorphism,showing similarities with orogenic-type deposits.In this contribution,both the syngenetic and epigenetic features of the Dongshengmiao are envisaged,and accounted for in the context of a genetic model with two metallogenic periods.Massive pyrite at the Dongshengmiao was mostly recrystallized during metamorphism,but finegrained texture was locally preserved,indicating its syngenetic origin.On the contrary,all the Zn-Pb-Cu ores observed in this study show characteristics of epigenetic hydrothermal mineralization that controlled by metamorphism and accompanying shear deformation.The sulfur and lead isotopic compositions of sphalerite and galena indicate that they were in situ remobilized from a syngenetic stratabound source,and the oxygen and hydrogen isotopic ratios of ore-fluid indicate that the large-scale remobilization was assisted by metamorphic fluid.The thermodynamic modeling indicates that the orefluid during remobilization has a great potential of transporting Cu.This may account for the abnormally enriched Cu in the remobilized SEDEX deposit.The metamorphic fluid might strip Cu from the fluid source during devolatilization,and overprint it on the Zn-Pb orebodies during remobilization.A secondary flowthrough modeling reveals that Zn- and Cu-sulfides would be preferentially redistributed in Fe-rich carbonates during remobilization,as a result of fluid-rock interaction.Conclusively,a multistage genetic model is proposed.During the development of the Proterozoic rift,stratabound Zn-Pb mineralization took place in a SEDEX ore-forming system.The syngenetic sulfides subsequently underwent a large-scale fluidassisted remobilization during the early Cretaceous metamorphism and thrusting,forming the shear zone-controlled epigenetic orebodies.During the remobilization process,Cu was scavenged from the source of metamorphic fluid,and deposited accompanying remobilized Zn-Pb sulfides.Shear structures and Fe-rich carbonates are ideal sites for redistribution and re-deposition of remobilized sulfide. | Richen Zhong Wenbo Li | 2016 | Geoscience Frontiers2016，7，3： | 2 |
| 2 | Melt-Fluid and Fluid-Fluid Immiscibility in a Na_(2)SO_(4)-SiO_(2)-H_(2)O System and Implications for the Formation of Rare Earth Deposits显示文摘Liquid-liquid immiscibility has crucial influences on geological processes,such as magma degassing and formation of ore deposits.Sulfate,as an important component,associates with many kinds of deposits.Two types of immiscibility,including(i)fluid-melt immiscibility between an aqueous solution and a sulfate melt,and(ii)fluid-fluid immiscibility between two aqueous fluids with different sulfate concentrations,have been identified for sulfate-water systems.In this study,we investigated the immiscibility behaviors of a sulfate-and quartz-saturated Na_(2)SO_(4)-SiO_(2)-H_(2)O system at elevated temperature,to explore the phase relationships involving both types of immiscibility.The fluid-melt immiscibility appeared first when the Na_(2)SO_(4)-SiO_(2)-H_(2)O sample was heated to~270℃,and then fluid-fluid immiscibility emerged while the sample was further heated to~450℃.At this stage,the coexistence of one water-saturated sulfate melt and two aqueous fluids with distinct sulfate concentrations was observed.The three immiscible phases remain stable over a wide pressure-temperature range,and the appearance temperature of the fluid-fluid immiscibility increases with the increased pressure.Considering that sulfate components occur extensively in carbonatite-related deposits,the fluid-fluid immiscibility can result in significant sulfate fractionation and provides implications for understanding the formation of carbonatite-related rare earth deposits. | CUI Hao ZHONG Richen XIE Yuling WANG Xiaolin CHEN Huan | 2021 | Acta Geologica Sinica(English Edition)2021，95，5： | 1 |
| 3 | Hunting the Datable Garnet using the LA-ICP-MS U-Pb Method:Predicting Garnet U Concentration,based on Major and Minor Elements显示文摘Garnet occurs in a wide range of rock types,from mantle peridotites to granites,from eclogites to skarns.In recent years,garnet LA-ICP-MS(Laser Ablation Inductively Coupled Plasma Mass Spectrometry)U-Pb dating has provided a powerful solution for retrieving the ages of rock formations,but successful dating is often prohibited by the low concentration of U.However,the concentration of U,a trace element of garnet,is unknown prior to the LA-ICP-MS analysis.In this study,we propose that the U concentration in garnet can be predicted by the contents of major and minor elements,which can be quantitatively obtained by EPMA(electron probe microanalysis).Using a supervised machine learning method(neural network),a model is trained to discriminate U-rich(>2 ppm)and U-poor(<2 ppm)garnets,based on EPMA results.Results of cross validation shows that the model has an average accuracy of~92%and is a powerful tool in detecting datable U-rich garnet.To facilitate the use of the discriminator,it is programmed as a stand-alone Microsoft Excel spreadsheet(HighUGarnet)and users directly paste the molar proportions of garnet end members into it and obtain the discrimination result. | DENG Yi ZHONG Richen LI Dengfeng LI Yanxia CUI Hao | 2022 | Acta Geologica Sinica(English Edition)2022，96，6： | 1 |
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