南秦岭主要类型热水沉积岩的REE地球化学

REE GEOCHEMISTRY OF MAIN TYPES OF HYDRSTHERMAL SEDIMENTARY ROCKS IN SOUTH QINLING

南秦岭泥盆纪沉积柱中产有多种类型海底热水沉积岩．它们的ΣＲＥＥ偏低（平均６３．０９×１０－６），ＲＥＥ配分曲线平缓右倾，Ｌａ／Ｙｂ＝２～８，Ｃｅ亏损，总体上与海水相似。产于Ｓｅｄｅｘ含矿层中的热水沉积岩具有正Ｅｕ异常，与现代海底热液及红海热液沉积物可比；而产在Ｓｅｄｅｘ含矿层以下地层中的热水沉积岩Ｅｕ亏损，与ＥＰＲ热液沉积物相似。ＲＥＥ地球化学研究和岩石学研究结果一致，支持热水沉积岩ＲＥＥ来源于海水及部分下伏沉积柱（包括基底），含矿热水沉积岩是盆地热演化到一定阶段具有一定深度和规模的循环对流体系在海底的化学沉积，而Ｓｅｄｅｘ含矿层以下地层中的热水沉积岩则是浅部热水对流循环的海底显示．成岩和变质作用对岩石的ＲＥＥ未造成影响。

There are many types of seafloor hydrothermal sedimentary rocks in Devonian colunm, South Qinling.Their ΣREE are low (average 63. 09 ×10-6, the REE patterns are gently right devition, La/Yb=2～8, Ce is deficit and the overall tendency of the pattern are similar to the REE patterns of sea water.The hydrothermal sedomentary and can be compared to modern seafloor hyerothermal sedimentary rocks within the the stratum below Sedex ore-beding bed possess Eu deficit and are similar to EPR hydrothermal Sediments.The REE geochemical study and geological and petrological study Lave the same result and suport that the hydrothermal sedimentary rocks REE came from the sea water and the partial REE mixing of under sedimentary column (including the base), the ore-bearing hydrothermal sedimentary rocks were seafloor chemical stdimtnts of the convention systim with certain scale and depth during the cettain tine of the basin heat evolution and the hydrothermal sedimentary rocks in the stratum below the Sedex ore-bearing bed were seafloor shows of hydrothermal shallow convection and circulation. The diagenesis and metamophism had not influence on the REE of the rocks.