The Longquanguan shear zone is an important structural belt in the North China Craton, separating the underlying Fuping complex from the overlying Wutai complex. This shear zone has experienced three episodes of defor...The Longquanguan shear zone is an important structural belt in the North China Craton, separating the underlying Fuping complex from the overlying Wutai complex. This shear zone has experienced three episodes of deformation: the first and main episode is a ductile top-to-ESE shear along the gently northwest-west dipping foliations, while the other two episodes are later collapse sliding. Prolonged granites parallel to the shear foliations make one of the main compositions of the Longquanguan shear zone. These granites experienced deformation to form mylonitic rocks when they emplaced during the first episode of deformation. Structural characters of the granites and their contacts to the country rocks indicate that these granites possibly resulted from in-situ partial remelting by shearing, i.e., they are syn-deformational granites. Monazites in these mylonitic granites are magmatic minerals and their crystallization ages may represent ages of the magmatic events, and also the ages for the main deformation of the Longquanguan shear zone. Monazite electronic microprobe dating were carried on two samples of granite, which gives multiple peak ages, among which 1,846 Ma and 1,877 Ma are the main peak ages for the two samples. These ages represent the main deformation of the Longquanguan shear zone, which is consistent with the main regional geological event at about 1,850 Ma caused by the collision between the Eastern and Western Blocks in North China. The good match between the monazite ages and the corresponding regional tectono-thermal events shows the feasibility and reliability of monazite electronic microprobe dating.展开更多
The morphology of polyvinyl chloride/polystyrene (PVC/PS) blend samples with different mass ratios, prepared by means of solution casting and melt mixing, have been successfully examined by electron microprobe analysi...The morphology of polyvinyl chloride/polystyrene (PVC/PS) blend samples with different mass ratios, prepared by means of solution casting and melt mixing, have been successfully examined by electron microprobe analysis (EMP). This experiment was performed in a scanning electron microscope attached to an energy dispersive X-ray analyzer. Differential scanning calorimetry was also used to investigate the phase separation of the blends. The results show that PVC and PS are incompatible and the blends have sea-islands phase structures. Blends prepared via melt mixing have finer phase-dispersion than those prepared via solution casting.展开更多
The electron microprobe maps the spatial distribution of elements in a rock at a sub-mineral-grain scale to provide a basis for understanding mineralization processes and to determine optimal strategies for extraction...The electron microprobe maps the spatial distribution of elements in a rock at a sub-mineral-grain scale to provide a basis for understanding mineralization processes and to determine optimal strategies for extraction of valuable target elements. Round Top Mountain (near the town of Sierra Blanca, Hudspeth County, west Texas, USA) is a peraluminous rhyolite laccolith that is homogeneously mineralized at over 500 ppm rare earths, more than 70% of which are yttrium and heavy rare earths (YHREEs). The massive deposit is exposed at the surface as a mountain some 2 km in diameter and 375 m in height. Round Top Mountain also contains Li, Be, U, Th, Nb, Ta, Ga, Rb, Cs, Sn, and F. The valuable YHREEs are hosted in yttrofluorite, which is soluble in dilute sulfuric acid. Texas Mineral Resources Corporation proposes to surface mine, crush, and heap leach the deposit. The distribution of YHREEs, and that of other trace elements, is remarkably homogeneous at outcrop drill hole scale. Here we document that YHREE mineralization appears pervasive through the rhyolite at a millimeter scale. Back scattered electron (BSE) and characteristic X-ray maps reveal the fine grain size and apparently random and dispersed spatial distribution of the yttrofluorite that hosts Round Top’s valuable YHREEs. The yttrofluorite grains do not appear to cluster at special mineralized locations, e.g., in pores or along cracks in the rhyolite. The same is apparently true of such other potentially valuable minerals as cassiterite and uranium species. These findings confirm that the distribution of YHREEs in Round Top Mountain rhyolite is homogeneous through different orders of magnitude of scale, i.e., from outcrop (as seen in the companion work in this volume) to sub-thin section. The material thus is ideal for a heap leach operation where homogeneous feedstock is crucial to consistent and economic operation. The findings also confirm and explain why mechanical separation would prove very difficult and expensive due to the astronomical number of yttrofluorite grains in even a golf-ball-size piece of Round Top rhyolite.展开更多
Zircon as a multi-objective typomorphic mineral commonly contains diverse trace elements with specific petrogenetic significances.The Hf abundance in zircon is sensitively indicative of melt fractionation during zirco...Zircon as a multi-objective typomorphic mineral commonly contains diverse trace elements with specific petrogenetic significances.The Hf abundance in zircon is sensitively indicative of melt fractionation during zircon growth on one hand,and on another,the Ti content is a robust temperature sensor of zircon crystallization and has been effectively u tilized in thermometric estimation.A Hf-Ti negative correlation was previously reported in igneous zircons,and thus a potential Hf thermometry was then speculated.In this work,we performed reliable electron microprobe(EMP)measurements of Hf and Ti in ultrahigh temperature(UHT)zircons from the North China Craton,in optimizing point,line and grid analysis.The EMP contents of Hf and Ti both show a wide range of fluctuation owing to the smaller probe spot,and some of them are higher than the LAICPMS data.The Hf-Ti correlation in UHT zircons displays dual and thus complicated patterns in contrast with the previous consideration,which implicates some other factors controlling the geochemical behaviors of Hf and Ti in zircons.Generally,the estimated Ti temperatures based on the EMP analyses are obviously higher than the LA-ICPMS outcomes,but are well consistent with the actual peak condition of the parent rock.It explains the common underestimation of Ti temperatures in hightemperature metamorphic rocks,by using LA-ICPMS analyses.展开更多
This paper proposes a useful web-based system for the management and sharing of electron probe micro-analysis( EPMA)data in geology. A new web-based architecture that integrates the management and sharing functions is...This paper proposes a useful web-based system for the management and sharing of electron probe micro-analysis( EPMA)data in geology. A new web-based architecture that integrates the management and sharing functions is developed and implemented.Earth scientists can utilize this system to not only manage their data,but also easily communicate and share it with other researchers.Data query methods provide the core functionality of the proposed management and sharing modules. The modules in this system have been developed using cloud GIS technologies,which help achieve real-time spatial area retrieval on a map. The system has been tested by approximately 263 users at Jilin University and Beijing SHRIMP Center. A survey was conducted among these users to estimate the usability of the primary functions of the system,and the assessment result is summarized and presented.展开更多
基金This work was financially supported by the key project for international collaboration, the National Natural Science Foundation of China (Project No. 40420120135).
文摘The Longquanguan shear zone is an important structural belt in the North China Craton, separating the underlying Fuping complex from the overlying Wutai complex. This shear zone has experienced three episodes of deformation: the first and main episode is a ductile top-to-ESE shear along the gently northwest-west dipping foliations, while the other two episodes are later collapse sliding. Prolonged granites parallel to the shear foliations make one of the main compositions of the Longquanguan shear zone. These granites experienced deformation to form mylonitic rocks when they emplaced during the first episode of deformation. Structural characters of the granites and their contacts to the country rocks indicate that these granites possibly resulted from in-situ partial remelting by shearing, i.e., they are syn-deformational granites. Monazites in these mylonitic granites are magmatic minerals and their crystallization ages may represent ages of the magmatic events, and also the ages for the main deformation of the Longquanguan shear zone. Monazite electronic microprobe dating were carried on two samples of granite, which gives multiple peak ages, among which 1,846 Ma and 1,877 Ma are the main peak ages for the two samples. These ages represent the main deformation of the Longquanguan shear zone, which is consistent with the main regional geological event at about 1,850 Ma caused by the collision between the Eastern and Western Blocks in North China. The good match between the monazite ages and the corresponding regional tectono-thermal events shows the feasibility and reliability of monazite electronic microprobe dating.
基金This project is supported by National Natural Science Foundation of China (No. 59773024).
文摘The morphology of polyvinyl chloride/polystyrene (PVC/PS) blend samples with different mass ratios, prepared by means of solution casting and melt mixing, have been successfully examined by electron microprobe analysis (EMP). This experiment was performed in a scanning electron microscope attached to an energy dispersive X-ray analyzer. Differential scanning calorimetry was also used to investigate the phase separation of the blends. The results show that PVC and PS are incompatible and the blends have sea-islands phase structures. Blends prepared via melt mixing have finer phase-dispersion than those prepared via solution casting.
文摘The electron microprobe maps the spatial distribution of elements in a rock at a sub-mineral-grain scale to provide a basis for understanding mineralization processes and to determine optimal strategies for extraction of valuable target elements. Round Top Mountain (near the town of Sierra Blanca, Hudspeth County, west Texas, USA) is a peraluminous rhyolite laccolith that is homogeneously mineralized at over 500 ppm rare earths, more than 70% of which are yttrium and heavy rare earths (YHREEs). The massive deposit is exposed at the surface as a mountain some 2 km in diameter and 375 m in height. Round Top Mountain also contains Li, Be, U, Th, Nb, Ta, Ga, Rb, Cs, Sn, and F. The valuable YHREEs are hosted in yttrofluorite, which is soluble in dilute sulfuric acid. Texas Mineral Resources Corporation proposes to surface mine, crush, and heap leach the deposit. The distribution of YHREEs, and that of other trace elements, is remarkably homogeneous at outcrop drill hole scale. Here we document that YHREE mineralization appears pervasive through the rhyolite at a millimeter scale. Back scattered electron (BSE) and characteristic X-ray maps reveal the fine grain size and apparently random and dispersed spatial distribution of the yttrofluorite that hosts Round Top’s valuable YHREEs. The yttrofluorite grains do not appear to cluster at special mineralized locations, e.g., in pores or along cracks in the rhyolite. The same is apparently true of such other potentially valuable minerals as cassiterite and uranium species. These findings confirm that the distribution of YHREEs in Round Top Mountain rhyolite is homogeneous through different orders of magnitude of scale, i.e., from outcrop (as seen in the companion work in this volume) to sub-thin section. The material thus is ideal for a heap leach operation where homogeneous feedstock is crucial to consistent and economic operation. The findings also confirm and explain why mechanical separation would prove very difficult and expensive due to the astronomical number of yttrofluorite grains in even a golf-ball-size piece of Round Top rhyolite.
基金supported by the National Natural Science Foundation of China(Grant No.41872190)。
文摘Zircon as a multi-objective typomorphic mineral commonly contains diverse trace elements with specific petrogenetic significances.The Hf abundance in zircon is sensitively indicative of melt fractionation during zircon growth on one hand,and on another,the Ti content is a robust temperature sensor of zircon crystallization and has been effectively u tilized in thermometric estimation.A Hf-Ti negative correlation was previously reported in igneous zircons,and thus a potential Hf thermometry was then speculated.In this work,we performed reliable electron microprobe(EMP)measurements of Hf and Ti in ultrahigh temperature(UHT)zircons from the North China Craton,in optimizing point,line and grid analysis.The EMP contents of Hf and Ti both show a wide range of fluctuation owing to the smaller probe spot,and some of them are higher than the LAICPMS data.The Hf-Ti correlation in UHT zircons displays dual and thus complicated patterns in contrast with the previous consideration,which implicates some other factors controlling the geochemical behaviors of Hf and Ti in zircons.Generally,the estimated Ti temperatures based on the EMP analyses are obviously higher than the LA-ICPMS outcomes,but are well consistent with the actual peak condition of the parent rock.It explains the common underestimation of Ti temperatures in hightemperature metamorphic rocks,by using LA-ICPMS analyses.
基金National Major Scientific Instruments and Equipment Development Special Funds,China(No.2016YFF0103303)National Science and Technology Support Program,China(No.2014BAK02B03)
文摘This paper proposes a useful web-based system for the management and sharing of electron probe micro-analysis( EPMA)data in geology. A new web-based architecture that integrates the management and sharing functions is developed and implemented.Earth scientists can utilize this system to not only manage their data,but also easily communicate and share it with other researchers.Data query methods provide the core functionality of the proposed management and sharing modules. The modules in this system have been developed using cloud GIS technologies,which help achieve real-time spatial area retrieval on a map. The system has been tested by approximately 263 users at Jilin University and Beijing SHRIMP Center. A survey was conducted among these users to estimate the usability of the primary functions of the system,and the assessment result is summarized and presented.
