中子活化分析花岗岩中造岩矿物的稀土和微量元素特征

Characterization of rare earth elements and trace elements in the rock-forming minerals of granite by INAA

中子活化分析的主要特点是用量少而精度高,是研究颗粒细小、极难挑选的矿物地球化学特征非常理想的方法。采用该方法测定了江西某地花岗岩中的主要矿物钾长石、斜长石、石英、黑云母以及副矿物锆石、磷灰石等的稀土和微量元素。结果表明,从锆石、磷灰石、黑云母到斜长石、钾长石、石英的8∑REE的含量和微量元素的含量依次降低,这正是花岗岩结晶过程的反映:即先结晶出的矿物微量元素含量高。全岩的Eu异常主要受到黑云母(可能还有钾长石和斜长石)的影响。

INAA analysis is considered as an effective method to study the geochemical features of some tiny minerals which are very difficult to be selected from rock samples. Both rare earth elements and trace elements in the rock-forming minerals of the granite from Jiangxi Province, including potash feldspar, plagioclase, quartz, biotite, accessory minerals, zircon and apatite, were analyzed and studied by INAA. Measured data show that the total 8 REE contents of minerals gradually decrease from zircon, apatite, biotite, plagioclase, potash feldspar to quartz in proper order, indicating a crystallization process of the granite. The Eu abnormal of whole rock would be affected by biotite, potash feldspar and plagioclase.