【摘要】 江西山南铀矿区位于相山铀矿田的北部,矿区内出露有大量的流纹岩和花岗斑岩,两者也是矿区内最主要的赋矿岩石。地球化学和Sr、Nd同位素研究表明,流纹英安岩和花岗斑岩具有高硅(SiO2质量分数为69.47%~72.19%和72.32%~78.6%)、富钠(K2O/Na2O为0.4~0.52和0.4~0.67之间)的碱性岩特征,具有过铝质特征;流纹英安岩和花岗斑岩富集Th、U、Pb等高场强元素和Rb、K等大离子亲石元素,相对亏损Zr、Ti、Ta、Ce等高场强元素和Ba、Sr等大离子亲石元素,表现出轻稀土元素富集,重稀土元素亏损(LREE/HREE分别为9.32~11.59和2.12~8.27),(La/Yb)N值分别为10.59~14.26和1.41~9.47,两者具有明显的负Eu异常(0.41~0.56和0.09~0.32),地球化学特征显示流纹英安岩和花岗斑岩形成于低压环境,属于板内环境;锆石饱和温度计得出两者具有较高的结晶温度,分别为812.5~904.9℃和772.1~826℃;流纹英安岩和花岗闪长斑均具有较大的I Sr含量,较小的εNd(t)值(-7.81~-8.93)。地球化学和Sr、Nd同位素特征显示山南矿区的流纹英安岩和花岗斑岩具有明显的S型花岗岩特征,形成过程中经历了部分熔融和同化混染作用。流纹英安岩和花岗斑岩及铀矿化具有强烈的壳源特征,区域内分布的元古代变质岩中的砂质岩和泥质岩很可能就是两者的源岩。结合前人年代学研究和本次地球化学、Sr-Nd同位素研究结果,说明相山矿田山南矿区内的流纹英安岩和花岗斑岩及相应的铀矿化形成与中生代华南地区岩石圈发生大规模的伸展减薄有关。更多还原

【Abstract】 The Shannan ore district is located in the north of the Xiangshan ore field,where rhyodacite and granite porphyry which are the most im- portant host rocks exposed in the surface. Geochemistry and Sr-Nd isotope of the rocks show the rhyodacite and granite porphyry is characterized with high Si( the qualities of SiO 2 are 69. 47% ~ 72. 19% and 72. 32% ~ 78. 6%,especially),rich Na( the ratios of K 2 O / Na 2 O are 0. 4 ~ 0. 52 and 0. 4 ~ 0. 67,especially) and with alkaline rock characteristics. The rhyodacite and granite porphyry with peraluminous characteristics are belong to high k calc al- kaline and shoshonite series. Rhyodacite and granodioritic porphyry are enrich in Th,U,Pb et al. high field-strength elements( HFSEs) and Rb、K et al. large-ion ithophile elements( LILEs),and depleted Zr、Ti、Ta、Ce et al. HFSEs and Ba、Sr et al. LILEs. The show the similar chondrite-normalized REE patterns,with negative Eu anomalies( δEu were 0. 41 ~ 0. 56 and 0. 09 ~ 0. 32,especially),enrich in LREEs and depleted HREEs( the ratio of LREE / HREE were 9. 32 ~ 11. 59 and 2. 12 ~ 8. 27,especially) and( La / Yb) N were 10. 59 ~ 14. 26 and 1. 41 ~ 9. 47,especially. The crystallization temperature of rhyodacite and granite porphyry based on zircon saturated thermometer are 812. 5 ~ 904. 9℃ and 772. 1 ~ 826℃,especially. The chemistry characteristics of rhyodacite and granite porphyry show they formed in a low pressure environment. The Sr-Nd isotope show the rocks with majoe I Sr and lesser εNd( t)(-7.81 ~-8. 93). Chemistry and Sr-Nd isotope characteristics show rhyodacite and granite porphyry are S type,and experience partial melting and assimilation constrain during their forming process. The source region of the rocks and uranium mineralization are provided with intense shell source characteristics,and the source rocks are may be arenaceous rock and argillaceous rock of the Proterozoic metamorphic rocks in the area. Combined with the chronology resulted by other scholar and chemistry,Sr-Nd isotope of this research,we think rhyodacite,granite porphyry and uranium mineraliza- tion in Shannan ore district of Xiangshan ore field are formed during the lithosphere extension and thinning of the South China Craton,which was caused by the subduction of Pacific plate in Mesozoic.更多还原