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皖赣相邻的鄣公山地区位于江南造山带东段北缘,区内广布一套厚度巨大、低绿片岩相变质的以泥砂质细碎屑岩为主含少量火山物质的复理石建造体,大量高精度同位素测年数据显示,其形成于822～850 Ma的新元古代。其以斜切本区的景德镇—江潭构造带为界,南部为溪口岩群,北部属双桥山群,二者REE、高场强元素(HFSE),如Nb、Ta、Zr、Hf及Nd同位素等具有相似的变化特征,显示区内浅变质碎屑岩具相同或相近的“原始”地壳物质组成特征;(La/Yb)N=4.66～13.63,δEu=0.09～0.3,(Gd/Yb)N=1.22～1.66,表明区内浅变质碎屑岩物源主要来自长英质岩石组成的后太古宙上地壳。碎屑锆石U-Pb年龄主要集中在826～2600 Ma,并出现显著的5个峰值,大致为2500 Ma,2000～2200 Ma,1800 Ma,960 Ma,827～841 Ma,其中以年轻碎屑锆石占绝对多数,大量的年轻碎屑锆石U-Pb年龄与碎屑岩密切共生的火山岩夹层年龄相近,反映浅变质碎屑岩物质主要来源于同时代火成岩类。溪口岩群和双桥山群浅变质碎屑岩大离子亲石元素(LILE)Rb、Cs、Sr、Ba、Th等含量及其相关比值、Sr同位素特征等存在一定差异,可能意味着溪口岩群和双桥山群碎屑岩在成岩过程中经历了不同的地质构造演化。区内浅变质火山-陆缘细碎屑岩形成于与板块构造体制相关构造-沉积环境,溪口岩群显示大陆边缘拉张构造背景下的沉积作用特征,而双桥山群原岩沉积构造环境与大陆岛弧关系较密切,显示板块俯冲阶段的沉积特征。
The adjacent Gaogongshan area in Anhui and Jiangxi is located in the northern margin of the eastern section of the Jiangnan orogenic belt. There is a broad set of thick, low-greenschist facies metamorphism in the area with silty fine-grained clastics consisting mainly of a small amount of volcanic flysch A large number of high-precision isotope dating data show that it was formed in the Neoproterozoic from 822 to 850 Ma. It is bounded by the Jingdezhen-Jiantan tectonic belt in the diagonal area, the Xikou group in the south and the Shuangqiaoshan group in the north. Both REE and HFSE such as Nb, Ta, Zr and Hf And Nd isotopes, showing that the metamorphic clastic rocks have the same or similar “original ” crust material composition characteristics; (La / Yb) N = 4.66-13.63 and δEu = 0.09-0.3, (Gd / Yb) N = 1.22-1.66, indicating that the source rocks of the metamorphic clastic rocks in the area mainly come from the upper Archean upper crust composed of feldspathic rocks. The U-Pb ages of detrital zircons are mainly concentrated in the range of 826-2600 Ma with 5 significant peaks of 2500 Ma, 2000-2200 Ma, 1800 Ma, 960 Ma and 827-841 Ma, of which the young detritus The zircons are the absolute majority. The young U-Pb age of young detrital zircons is similar to the age of closely interbedded volcanic rocks, which indicates that the metamorphic clastic rocks are mainly derived from contemporaneous igneous rocks. There are some differences in the contents of Rb, Cs, Sr, Ba, Th and other related ratios, Sr isotope characteristics of the LILE in the Shikou Rock Group and the Shuangqiao Group of supermassive clastic rocks, Koukou Group and Shuangqiao Group clastic rocks underwent different tectonic evolution during diagenesis. The metamorphic volcano-marginal microfacies in the area are formed in the tectonic-sedimentary environment related to plate tectonics and the sedimentary facies in the Xikou group show the extensional structure of the continental margin. The sedimentary structure of the original rocks in the Shuangqiaoshan group The environment is closely related to the continental island arc, indicating the depositional characteristics of the plate subduction stage.