辽西义县盆地火山岩的基本特征及其成因探讨

通过对辽西义县盆地火山岩的岩石学、矿物学以及地球化学特征的研究，指出本区火山岩属于一套弱碱性、普通型的火山岩系列．通过热力学计算以及对岩石结构和动力学的分析，表明原始岩浆来自上地幔（约６７ｋｍ），并在约１７ｋｍ处（上下地壳附近）形成高位岩浆房．在高位岩浆房中，由于岩浆的双扩散对流作用，发生了伴随有分离结晶作用的液相分异作用，而同化混染作用则发生于岩浆演化的早期。喷出的岩浆成分受断裂切过高位岩浆房的相对位置的控制。

ESSENTIAL CHARACTERISTICS OF VOLCANIC ROCKS AND DISCUSSION ON THEIR GENESIS IN YIXIAN BASIN, WESTERN LIAONING

The volcanic rocks from Yi-clan basin of western Liaoning are thought to be a suite ofthe weak-alkali and normal type volcanic series by the study of petrology, mineralogicaland geochemical characteristics. Thermodynamics calculation and analysis with the textureof rocks and dynamics show that primitive magma comes from upper-mantle (about 67km) and high-level magma chamber forms at about 17 km (estimated at the boundary between upper and lower crust). In the high-level magma chamber, double--diffusive convection of magma leads to the liquid-state differentiation with a little fractional crystallization. Assimilation and contamination occurs at the early period of magmatic evolution. Themagmatic composition of eruption is controlled by comparative position of the high-levelmagma chamber cut by fault.