赣中南新元古代潭头群变质沉积岩物源及构造背景

赣中南一带广泛出露前震旦纪新元古代潭头群变质沉积岩，地层中火山岩较发育，属火山-沉积碎屑岩组合。其砂质岩石具有中等含量的SiO2（64．81％～71．77％，平均为68．30％），较低的FeOt＋MgO（4．08％～6．99％，平均为5．74％）和较高的K2O／Na2O（0．75～3．33，平均为1．64）及Al2O3／TiO2（26．02～43．47，平均为31．73）。稀土总量较高（∑REE为158．44×10^-6～293．36×10^-6。平均为237．98×10^-6），轻稀土明显富集。所有样品的稀土分布模式相似，明显向右倾斜，具有中等程度的Eu异常（δEu为0．42～0．61，平均为0．48）。微量元素平均含量与上地壳平均组分相当。地球化学特征表明，赣中南新元古代潭头群变质沉积岩可能来源于古-中元古代地层。结合变质岩的沉积环境及其火山岩特征，研究认为潭头群的构造背景属岛弧环境，可能与新元古代华夏陆块和扬子陆块的俯冲碰撞有关。

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 centralsouth 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 ∑REE （ 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.