鲁西昌乐新生代碱性玄武岩中刚玉/蓝宝石的矿物学特征及其成因探讨 Mineral Characteristics and Origin Discussion of Corundum/Sapphire in Cenozoic Alkali Basalts of the Changle, Western Shandong, China

本文利用电子探针、LA-ICP-MS等现代测试方法系统的分析山东昌乐刚玉/蓝宝石矿物的元素分布特征，探讨了新生代碱性玄武岩中蓝宝石的成因。昌乐刚玉/蓝宝石矿物中总体杂质含量较低，总含量为1.73%~0.21%，不同样品元素含量具有差异，Fe元素是昌乐蓝宝石中含量最高的杂质元素，也明显高于其他产地的玄武岩型蓝宝石。昌乐蓝宝石中Ga元素含量均高于100 ppm，表明昌乐刚玉显示岩浆型成因，裂纹较发育的刚玉叠加了明显的后期熔体渗透交代作用。通过刚玉边部共生的碱性长石初步估算，刚玉形成的条件应接近或大于1000˚C/23 km。 On the basis of EPMA and LA-ICP-MS modern analysis methods, we systemically investigate the che- mical characteristics of the Changle corundum/sapphire minerals, and explore the origin of the Changle corundum/sapphire in Cenozoic alkali basalts. The general content of impurity in the Chan-gle corundum/sapphire is low, which is 1.73%~0.21% in total, and is variable in different samples. Among the impurity elements in Changle samples, the concentration of Fe is the highest, and it’s significantly higher than the basalt type sapphires from other origin places. Ga content is higher than 100 ppm in the Changle corundum/sapphire, showing a magma type in origin. The fracture developed corundum presents a significant late melt infiltration and alteration. By the associated alkali feldspar within the margin of corundum crystal, preliminary estimate indicates that the formation of corundum/sapphire conditions should be close to or more than 1000˚C/23 km.