Guizhou is one of the dominating karst regions, where laterite is widespread, in China. Seventy-two laterite samples were taken from twelve laterite sections in the karst areas of Guizhou Province, which are possessed...Guizhou is one of the dominating karst regions, where laterite is widespread, in China. Seventy-two laterite samples were taken from twelve laterite sections in the karst areas of Guizhou Province, which are possessed of typical subtropical karst geomorphological and ecological environmental features and have evolved completely from dolostones and limestones. In terms of the major, trace and REE data for the samples this paper discusses the gcochemical characteristics of laterite in the karst areas with an attempt to disclose the geochemical process and evolutionary rule of laterite formation. There have been involved three important pedogenetic geochemical precesses in the formation of laterite in the karst areas: (1 ) enrichment of silicon and aluminum and depletion of calcium and magnesium; (2) enrichment of iron and manganese; and (3) enrichment of aluminum and depletion of silicon. During the formation and evolution of laterite, obvious enrichment and differentiation of trace elements such as Cu, Pb,Zn, Ni, Co, Cr, Rb, F, Cl, and As can be observed, but for the rare-earth elements, their enrichment is remarkable against a weak differentiation. The REE distribution patterns in the laterite are similar to those of its parental carbonate rocks.展开更多
Distributions of the rare-earth elements (REE) in omphacite and garnet and REE behaviors during metamorphic processes were discussed. The REE concentrations of garnet and omphacite in six eclogite samples from the Dab...Distributions of the rare-earth elements (REE) in omphacite and garnet and REE behaviors during metamorphic processes were discussed. The REE concentrations of garnet and omphacite in six eclogite samples from the Dabie Mountain, central China, were measured by inductively coupled plasma-mass spectrometry (ICP-MS). The correlation of δEu ratios between garnet and omphacite indicated that chemical equilibrium of REE distribution between garnet and omphacite could be achieved during ultra-high pressure (UHP) metamorphism. Most of the partition coefficients (Kd=CiOmp/CiGrt) of light rare-earth elements (LREE) are higher than 1. However the partition coefficients of heavy rare-earth elements (HREE) are lower than 1. This indicated that the LREE inclined to occupy site M2 in omphacite, but the HREEs tended to occupy eightfold coordinated site in garnet during the eclogite formation. The REE geochemistry of the eclogites indicated that LREE could be partially lost during the prograde metamorphic process of protolith, but be introduced into the rocks during the symplectite formation. LREE are more active than HREE during the UHP metamorphism. The results are favorable to highlighting the REE behavior and evolution of UHP metamorphic rocks.展开更多
The distribution and anomalies of rare earth elements(REEs) of granitic regolith were studied in Inner Mongolia and Hainan Island, China. One profile showed slight REE enrichment of an upper layer and no obvious light...The distribution and anomalies of rare earth elements(REEs) of granitic regolith were studied in Inner Mongolia and Hainan Island, China. One profile showed slight REE enrichment of an upper layer and no obvious light REE/heavy REE(LREE/HREE) fractionation(La_N/Yb_N of 0.9). The second profile was significantly enriched in REEs and enriched in LREEs in the upper portion(La_N/Yb_N>1.8). Eu, Ce, and Gd anomalies of the two profiles are different. Slightly negative Eu, Ce, and Gd anomalies in NMG-3-1 indicate slow dissolution of primary minerals and little secondary products; in contrast, a positive Eu anomaly in HN-2 suggests the vegetation cycle may contribute to soil. The Ce anomaly of HN-2 reflects oxidation of Ce and coprecipitation by Fe-and Mn-oxides and organic matter. Correlation between Ce and Gd anomalies in HN-2 suggests Ce and Gd are both influenced by redoxreduction.展开更多
This study investigated the impact of topography and vegetation on distribution of rare earth elements(REEs)in calcareous soils using methods of single extraction and mass balance calculation. The purposes of the stud...This study investigated the impact of topography and vegetation on distribution of rare earth elements(REEs)in calcareous soils using methods of single extraction and mass balance calculation. The purposes of the study were to set a basis for further research on the biogeochemical REE cycle and to provide references for soil–water conservation and REE-containing fertilizer amendments. The results show a generally flat Post-Archean Average Australian Shale—normalized REE pattern for the studied calcareous soils. REE enrichment varied widely. The proportion of acidsoluble phases of heavy REEs was higher than that of light REEs. From top to bottom of the studied hills, dominant REE sources transitioned from limestone in-situ weathering to input from REE-containing phases(e.g., clay minerals,amorphous iron, REE-containing fluids). Our results indicate that the REE content of calcareous soils is mainly controlled by slope aspect, while the enrichment degree of REEs is related to geomorphological position and vegetation type.Furthermore, the proportion of acid-soluble phases of REEs is mainly controlled by geomorphological position.展开更多
The distribution of rare earth element (REE) forms in soils is given in the present paper on the basis of sequential fractionation and determination of 34 representative surface soils collected from all parts of China...The distribution of rare earth element (REE) forms in soils is given in the present paper on the basis of sequential fractionation and determination of 34 representative surface soils collected from all parts of China.Results obtained show that the extraction rate of water soluble and exchangeable REE had the odd-even phenomenon and that of organically bound REE from La to Lu tended to reduce gradually with the increase of atomic number.The stability of Sc and the activity and enrichment of Tm in soils are proposed.Furthermore,the paper makes a preliminary discussion on the differences in the concentration distribution of various forms of individual REE in some soils.展开更多
The increased production and price of rare earth elements(REEs) are indicative of their importance and of growing global attention. More accurate and practical exploration procedures are needed for REEs, and for other...The increased production and price of rare earth elements(REEs) are indicative of their importance and of growing global attention. More accurate and practical exploration procedures are needed for REEs, and for other geochemical resources. One such procedure is a multivariate approach. In this study, five classifiers, including multilayer perceptron(MLP), Bayesian, k-Nearest Neighbors(KNN), Parzen, and support vector machine(SVM),were applied in supervised pattern classification of bulk geochemical samples based on REEs, P, and Fe in the Kiruna type magnetite-apatite deposit of Se-Chahun,Central Iran. This deposit is composed of four rock types:(1) High anomaly(phosphorus iron ore),(2) Low anomaly(metasomatized tuff),(3) Low anomaly(iron ore), and(4)Background(iron ore and others). The proposed methods help to predict the proper classes for new samples from the study area without the need for costly and time-consuming additional studies. In addition, this paper provides a performance comparison of the five models. Results show that all five classifiers have appropriate and acceptable performance. Therefore, pattern classification can be used for evaluation of REE distribution. However, MLP and KNN classifiers show the same results and have the highest CCRs in comparison to Bayesian, Parzen, and SVM classifiers. MLP is more generalizable than KNN and seems to be an applicable approach for classification and predictionof the classes. We hope the predictability of the proposed methods will encourage geochemists to expand the use of numerical models in future work.展开更多
文摘Guizhou is one of the dominating karst regions, where laterite is widespread, in China. Seventy-two laterite samples were taken from twelve laterite sections in the karst areas of Guizhou Province, which are possessed of typical subtropical karst geomorphological and ecological environmental features and have evolved completely from dolostones and limestones. In terms of the major, trace and REE data for the samples this paper discusses the gcochemical characteristics of laterite in the karst areas with an attempt to disclose the geochemical process and evolutionary rule of laterite formation. There have been involved three important pedogenetic geochemical precesses in the formation of laterite in the karst areas: (1 ) enrichment of silicon and aluminum and depletion of calcium and magnesium; (2) enrichment of iron and manganese; and (3) enrichment of aluminum and depletion of silicon. During the formation and evolution of laterite, obvious enrichment and differentiation of trace elements such as Cu, Pb,Zn, Ni, Co, Cr, Rb, F, Cl, and As can be observed, but for the rare-earth elements, their enrichment is remarkable against a weak differentiation. The REE distribution patterns in the laterite are similar to those of its parental carbonate rocks.
基金financially supported by the National Natural Science Foundation of China(Grant No.40873049) and Kyoto University,Japan
文摘Distributions of the rare-earth elements (REE) in omphacite and garnet and REE behaviors during metamorphic processes were discussed. The REE concentrations of garnet and omphacite in six eclogite samples from the Dabie Mountain, central China, were measured by inductively coupled plasma-mass spectrometry (ICP-MS). The correlation of δEu ratios between garnet and omphacite indicated that chemical equilibrium of REE distribution between garnet and omphacite could be achieved during ultra-high pressure (UHP) metamorphism. Most of the partition coefficients (Kd=CiOmp/CiGrt) of light rare-earth elements (LREE) are higher than 1. However the partition coefficients of heavy rare-earth elements (HREE) are lower than 1. This indicated that the LREE inclined to occupy site M2 in omphacite, but the HREEs tended to occupy eightfold coordinated site in garnet during the eclogite formation. The REE geochemistry of the eclogites indicated that LREE could be partially lost during the prograde metamorphic process of protolith, but be introduced into the rocks during the symplectite formation. LREE are more active than HREE during the UHP metamorphism. The results are favorable to highlighting the REE behavior and evolution of UHP metamorphic rocks.
基金supported by the National Natural Science Foundation of China(Grant No.4121000441661144042)National Basic Research Program(973 project)of China(2013CB956401)
文摘The distribution and anomalies of rare earth elements(REEs) of granitic regolith were studied in Inner Mongolia and Hainan Island, China. One profile showed slight REE enrichment of an upper layer and no obvious light REE/heavy REE(LREE/HREE) fractionation(La_N/Yb_N of 0.9). The second profile was significantly enriched in REEs and enriched in LREEs in the upper portion(La_N/Yb_N>1.8). Eu, Ce, and Gd anomalies of the two profiles are different. Slightly negative Eu, Ce, and Gd anomalies in NMG-3-1 indicate slow dissolution of primary minerals and little secondary products; in contrast, a positive Eu anomaly in HN-2 suggests the vegetation cycle may contribute to soil. The Ce anomaly of HN-2 reflects oxidation of Ce and coprecipitation by Fe-and Mn-oxides and organic matter. Correlation between Ce and Gd anomalies in HN-2 suggests Ce and Gd are both influenced by redoxreduction.
基金supported jointly by the National Natural Science Foundation of China(41571130042,41522207,41325010)the State’s Key Project of Research and Development Plan of China(2016YFA0601002)
文摘This study investigated the impact of topography and vegetation on distribution of rare earth elements(REEs)in calcareous soils using methods of single extraction and mass balance calculation. The purposes of the study were to set a basis for further research on the biogeochemical REE cycle and to provide references for soil–water conservation and REE-containing fertilizer amendments. The results show a generally flat Post-Archean Average Australian Shale—normalized REE pattern for the studied calcareous soils. REE enrichment varied widely. The proportion of acidsoluble phases of heavy REEs was higher than that of light REEs. From top to bottom of the studied hills, dominant REE sources transitioned from limestone in-situ weathering to input from REE-containing phases(e.g., clay minerals,amorphous iron, REE-containing fluids). Our results indicate that the REE content of calcareous soils is mainly controlled by slope aspect, while the enrichment degree of REEs is related to geomorphological position and vegetation type.Furthermore, the proportion of acid-soluble phases of REEs is mainly controlled by geomorphological position.
文摘The distribution of rare earth element (REE) forms in soils is given in the present paper on the basis of sequential fractionation and determination of 34 representative surface soils collected from all parts of China.Results obtained show that the extraction rate of water soluble and exchangeable REE had the odd-even phenomenon and that of organically bound REE from La to Lu tended to reduce gradually with the increase of atomic number.The stability of Sc and the activity and enrichment of Tm in soils are proposed.Furthermore,the paper makes a preliminary discussion on the differences in the concentration distribution of various forms of individual REE in some soils.
文摘The increased production and price of rare earth elements(REEs) are indicative of their importance and of growing global attention. More accurate and practical exploration procedures are needed for REEs, and for other geochemical resources. One such procedure is a multivariate approach. In this study, five classifiers, including multilayer perceptron(MLP), Bayesian, k-Nearest Neighbors(KNN), Parzen, and support vector machine(SVM),were applied in supervised pattern classification of bulk geochemical samples based on REEs, P, and Fe in the Kiruna type magnetite-apatite deposit of Se-Chahun,Central Iran. This deposit is composed of four rock types:(1) High anomaly(phosphorus iron ore),(2) Low anomaly(metasomatized tuff),(3) Low anomaly(iron ore), and(4)Background(iron ore and others). The proposed methods help to predict the proper classes for new samples from the study area without the need for costly and time-consuming additional studies. In addition, this paper provides a performance comparison of the five models. Results show that all five classifiers have appropriate and acceptable performance. Therefore, pattern classification can be used for evaluation of REE distribution. However, MLP and KNN classifiers show the same results and have the highest CCRs in comparison to Bayesian, Parzen, and SVM classifiers. MLP is more generalizable than KNN and seems to be an applicable approach for classification and predictionof the classes. We hope the predictability of the proposed methods will encourage geochemists to expand the use of numerical models in future work.
