The Source and Tectonic Setting of Neoproterozoics Metasedimentary Rocks from Tantou Group in the Central-south of Jiangxi Province

The Neoproterozoic metasedimentary rocks from Tantou Group which exposed broadly in the central-south of Jiangxi Province are developed obviously volcanic rocks and a combination of volcanic rocks-clastic sedimentary rocks.There are moderate contents of SiO2(64.81% ~ 71.77%,an average of 68.30%),lower FeOt + MgO(4.08 %~ 6.99%,an average of 5.74 %) and higher K2O/Na2O(0.75~3.33,An average of 1.64)、Al2O3/TiO2(26.02 ~ 43.47,an average of 31.73) in the sandy rocks.At the same time,the metasedimentary rocks have the characteristics of high ΣREE(158.44×10-6 to 293.36×10-6,with an average of 237.98×10-6) and obviously enriched LREE.The distribution patterns of all samples of rare earth elements are similar,with the obvious right tilt and medium-level Eu anomaly(δEu=0.42~ 0.61,with an average of 0.48).The average compositions of trace elements are corresponded to the upper crust.The geochemical characteristics indicate that the meta-sedimentary rocks of Neoproterozoic Tantou Group in the central-south of Jiangxi Province are derived from the Early and Mid-Proterozoic stratum.Combination of metamorphic sedimentary environment and its volcanic features,the result shows that the tectonic setting of Tantou Group is island arc and the formation are related to the subduction and collision between the Yangtze and Cathaysia block during Neoproterozoic.