江西冷水火山—侵入杂岩体岩石化学及地球化学特征

冷水银铅锌矿的火山—侵入杂岩体出露于信江中生代火山盆地南缘。岩石化学、微量元素、稀土元素和铷锶同位素分析表明冷水火山岩及次火山岩是同源产物,是同熔岩浆分异的结果。岩浆中成矿物质Cu、Fe、Pb、Zn、S、H_2O的数量与下地壳、上地慢或洋壳物质的部分熔融程度有关。冷水火山—侵入杂岩是钙碱性岩浆于不同演化阶段形成的岩石组合并具有化学成分上的相似性和继承性。岩浆房中具有良好的分带现象,上部为富钾的流纹质岩浆,向下逐渐变为基性岩浆。岩浆由钙碱性向偏碱性演化,促使成矿元素大量富集,在一定条件下形成矿床。

Petrochemical and Geochemical Characteristics of the Volcano-intrusive Complex in lengshui,Jiangxi

The Lengshui volcano-intrusive complex occurs in the Mesozoic volcanic depression of the northeastern Jiangxi province. Its country rocks are mainly metamorphic rocks of Banxi Group. This complex consists of extrusive rocks which are mainly rhyolite-pyroclastic rocks, different kind of subvolcanic rocks and shallow-plutonic rocks from the basic basalt-porphyrite to the acidic granite-porphry. It belongs to a calcalkalie rock series, but it exhibits some features of the potash-rich subalkalic rocks formed at the late stage of the magmatic differentiation. The regularity in the development of the zoned magma chamber can be seen in the perfect fractional crystallization, gravitational differentiation and intrusive sequence. The Rb/Sr and Li/Mg ratios of the rocks increase, while the Ba/Rb ratio decrease with the evolution of the petrochemical composition from basic to acidic. The content of siderophile elements is quite low and that of chalcophile elements is high in the complex in comparison with the same kind of rocks in South China. The REE distribution patterns of the rocks show similarity with the syntectic granitoid in South China. The initial ratio of ~(87)Sr/~(86)Sr is 0.7139. The rock-forming materials originated mainly from partical melting of lower crust of the earth. The authors have concluded that the volcano-intrusive complex is comagmatic rock and it is resulted from the different evolvementary stage of the s yntectic magma.