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
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).
