拜城县黑英山霞石正长岩矿物学特征研究

MINERALOGICAL CHARACTERISTICS OF NEPHELINE -SYENITEIN HEIYINGSHAN ,BAICHENG COUNTY

霞石正长岩是重要的炼铝资源和陶瓷、玻璃原料。文中利用扫描电镜、X衍射、红外线、电子探针等,综合分析方法对黑英山霞石正长岩的矿物学特征作了详细研究。着重描述了岩石的矿物组合、矿物生成及变化特征。对主要矿物进行了化学成分及X衍射分析,测得霞石成分:SiO_243.66％,Al_2O_330.97％,K_2O4.23％,Na_2O18.46％(Na_2O高于其它地区的霞石)。根据霞石单矿物实测成分计算出其晶体化学分子式为:(K_(0.525)Na_(3.528)Ca_(0.012))_(4.065)[Cr_(0.010)Al-(3.559)Mg_(0.009)Fe_(0.054)Mn_(0.012)Ti_(0.008)Si_(4.258)O_(16)];测得霞石的主要X衍射d值为:0.302～0.303,0.386～0.389,0.1388～0.1391(nm)。测得微斜长石的成分:SiO_264.82％,Al_2O_319.68％,K_2O11.77％,Na_2O2.30％,求得其三斜度△=0.83～1.00,属低微斜长石。通过霞石正长岩中钾长石与霞石矿物中对K原子分配值计算和作图,解得矿物生成温度为400～500℃。测得岩石中的钠长石主要为低钠长石,属后期交代矿物。

Nepheline-syenite is an important aluminium resource and a raw material for ceramic and glass industry. The mineralogical characteristics of the nepheline-syenite were studied in detail by use of electronic scanning microscope,X - ray power diffraction pattern,infrared absorption,and electron-probe analysis etc. .The association,growing sequence and the variation of minerals were described. Through analysis and identification,the average chemical composition of the nepheline is shown to be SiO2 43. 66%,Al2O3 30. 97%, K2O 4. 23% and Na2O 18. 46%. The Na2O content is more than that of the other regions. The molecule formula of the nepheline crystal computed is (K0.525 Na3.582Ca0.012)4.065[Cr0.010Al3.559Mg0.009Fe0.054 Mn0.012Ti0.008Si4.258O16]. The stronger lines of the nepheline in the power diffraction pattern are 0. 302-0. 303 ,0. 386,0. 389 and 0.1388-0.1391(nm). The chemical composition of microcline is SiO2 64. 82%,A12O3 19. 68% ,K2O 11. 77% and Na2O 2. 30%,with low triclinicity of 0. 81-1. 00. By calculation of the K-atom content in potashfeldspar and nepheline,the temperature of the two minerals being formed is 400-500℃. The albite in this rock is a low-albite,formed by later replacement.