The Xinyu iron deposit, located in central Jiangxi Province, is one of the most important BIF-type deposits in China. It is hosted in the Late Proterozoic volcanic- sedimentary rocks, which are composed of sericite- c...The Xinyu iron deposit, located in central Jiangxi Province, is one of the most important BIF-type deposits in China. It is hosted in the Late Proterozoic volcanic- sedimentary rocks, which are composed of sericite- chlorite pyhllite, magnetite-bearing chlorite phyllite or schist, magnetite quartzite, and schist （Yu et al., 1989; Zeng et al., 2011）.展开更多
On the basis of a comprehensive study on the petrology, trace elements and isotopic geochemistry of the Xiangshan amphibolites, we suggest that the protoliths of the amphibolites were basalts formed in an island\|arc ...On the basis of a comprehensive study on the petrology, trace elements and isotopic geochemistry of the Xiangshan amphibolites, we suggest that the protoliths of the amphibolites were basalts formed in an island\|arc tectonic setting. The basaltic magma was derived from a slightly depleted mantle source with a small amount of crustal contamination. Assemblage of the rock\|forming minerals indicates that these amphibolites underwent a low\|grade metamorphism of amphibolite facies. According to the formation age (1113 Ma) and subsequent metamorphic age (726.6 Ma) of the basalts as well as the geological and geochemical features of these amphibolites, a tectonic model of Proterozoic oceanic island\|arc setting is proposed for central Jiangxi.展开更多
Detailed REE and trace elements geochemical studies of the Zhoutan Group metasedimentary rocks in central Jiangxi Province, China, and rock-forming minerals such as garnet were conducted and the results showed that th...Detailed REE and trace elements geochemical studies of the Zhoutan Group metasedimentary rocks in central Jiangxi Province, China, and rock-forming minerals such as garnet were conducted and the results showed that the REEs are partly present in the rock-forming minerals and are dominantly contained in the lattice of accessory minerals. In the process of metamorphism the REEs between garnet porphyroblast and rock and the partitioning of REEs between garnet and the host rock is obviously controlled by the chemical composition of the system. The REEs compositions of metamorphic veins and their minerals display remarked lanthanide tetrad effects and the element pairs Zr-Hf, Y-Ho, Pb-Nd and U-Th have also experienced a certain degree of fractionation with respect to the metasedimentary rocks and they can be used as discriminating indicators to some extent for the occurrence of fluid processes in the process of metamorphism of the Zhoutan Group.展开更多
The metamorphic belt in central Jiangxi, located in the compound terrain within the Cathaysia, Yangtze Block and Caledonian fold zone of South China, is composed dominantly of meta-argillo-arenaceous rocks, with minor...The metamorphic belt in central Jiangxi, located in the compound terrain within the Cathaysia, Yangtze Block and Caledonian fold zone of South China, is composed dominantly of meta-argillo-arenaceous rocks, with minor amphibolite. These rocks underwent amphibolite-facies metamorphism. The meta-argillo-arenaceous rocks show large variations in major element composition, but have similar REE patterns and trace element composition, incompatible element and LIE enrichments [high Th/Sc ({0.57}-{3.59}), La/Sc ({1.46}-{12.4}), La/Yb ({5.84}-{19.0})] and variable Th/U ratios, with ΣREE=129-296μg/g, δEu={0.51}-{0.86}, and (La/Yb)-N={3.95}-{12.9}. The Nd isotopic model ages t-{DM} of these rocks vary from 1597 to 2124 Ma. Their {}+{143}Nd/+{144}Nd values are low [ε-{Nd}(0)={-11.4} to {-15.8}]. Some conclusions have been drawn as follows: (1) The metamorphic rocks in central Jiangxi Province are likely formed in a tectonic environment at the passive continental margin of the Cathaysia massif. (2) The metamorphosed argillo-arenaceous rocks are composed dominantly of upper crustal-source rocks (Al- and K|rich granitic or/and sedimentary rocks of Early Proterozoic), which experienced good sorting, slow deposition and more intense chemical weathering. (3) According to the whole-rock Sm-Nd isochron ages (1113±49 to 1199±26 Ma) of plagioclase-amphibole (schist) and Nd isotopic model age t-{DM} (1597-2124 Ma) of meta-argillo-arenaceous rocks, the metamorphic belt in central Jiangxi Province was formed during the Middle Proterozoic (1100-1600 Ma).展开更多
基金the China State Mineral Resources Investigation Program (Grant No.1212011220936)National Science Foundation of China (Grant No.U1403292 41472196)
文摘The Xinyu iron deposit, located in central Jiangxi Province, is one of the most important BIF-type deposits in China. It is hosted in the Late Proterozoic volcanic- sedimentary rocks, which are composed of sericite- chlorite pyhllite, magnetite-bearing chlorite phyllite or schist, magnetite quartzite, and schist （Yu et al., 1989; Zeng et al., 2011）.
文摘On the basis of a comprehensive study on the petrology, trace elements and isotopic geochemistry of the Xiangshan amphibolites, we suggest that the protoliths of the amphibolites were basalts formed in an island\|arc tectonic setting. The basaltic magma was derived from a slightly depleted mantle source with a small amount of crustal contamination. Assemblage of the rock\|forming minerals indicates that these amphibolites underwent a low\|grade metamorphism of amphibolite facies. According to the formation age (1113 Ma) and subsequent metamorphic age (726.6 Ma) of the basalts as well as the geological and geochemical features of these amphibolites, a tectonic model of Proterozoic oceanic island\|arc setting is proposed for central Jiangxi.
基金supported jointly by the National Natural Science Foundation of China (40673061)the Ministry of Science and Technology of China (95-Pre-39)the Foundation of State Key Laboratory for Mineral Deposits Research, Nanjing University
文摘Detailed REE and trace elements geochemical studies of the Zhoutan Group metasedimentary rocks in central Jiangxi Province, China, and rock-forming minerals such as garnet were conducted and the results showed that the REEs are partly present in the rock-forming minerals and are dominantly contained in the lattice of accessory minerals. In the process of metamorphism the REEs between garnet porphyroblast and rock and the partitioning of REEs between garnet and the host rock is obviously controlled by the chemical composition of the system. The REEs compositions of metamorphic veins and their minerals display remarked lanthanide tetrad effects and the element pairs Zr-Hf, Y-Ho, Pb-Nd and U-Th have also experienced a certain degree of fractionation with respect to the metasedimentary rocks and they can be used as discriminating indicators to some extent for the occurrence of fluid processes in the process of metamorphism of the Zhoutan Group.
文摘The metamorphic belt in central Jiangxi, located in the compound terrain within the Cathaysia, Yangtze Block and Caledonian fold zone of South China, is composed dominantly of meta-argillo-arenaceous rocks, with minor amphibolite. These rocks underwent amphibolite-facies metamorphism. The meta-argillo-arenaceous rocks show large variations in major element composition, but have similar REE patterns and trace element composition, incompatible element and LIE enrichments [high Th/Sc ({0.57}-{3.59}), La/Sc ({1.46}-{12.4}), La/Yb ({5.84}-{19.0})] and variable Th/U ratios, with ΣREE=129-296μg/g, δEu={0.51}-{0.86}, and (La/Yb)-N={3.95}-{12.9}. The Nd isotopic model ages t-{DM} of these rocks vary from 1597 to 2124 Ma. Their {}+{143}Nd/+{144}Nd values are low [ε-{Nd}(0)={-11.4} to {-15.8}]. Some conclusions have been drawn as follows: (1) The metamorphic rocks in central Jiangxi Province are likely formed in a tectonic environment at the passive continental margin of the Cathaysia massif. (2) The metamorphosed argillo-arenaceous rocks are composed dominantly of upper crustal-source rocks (Al- and K|rich granitic or/and sedimentary rocks of Early Proterozoic), which experienced good sorting, slow deposition and more intense chemical weathering. (3) According to the whole-rock Sm-Nd isochron ages (1113±49 to 1199±26 Ma) of plagioclase-amphibole (schist) and Nd isotopic model age t-{DM} (1597-2124 Ma) of meta-argillo-arenaceous rocks, the metamorphic belt in central Jiangxi Province was formed during the Middle Proterozoic (1100-1600 Ma).
