RELATIONSHIP BETWEEN CATHODOLUMINESCENCE AND CONCENTRATION OF IRON AND MANGANESE IN CARBONATE MINERALS
Huang Sijing(Chengdu College of Geology, Chengdu 610059)
Eighty-six carbonate samples,from Sichuan,Guizhou and Shanxi,ranging in age of Ordovician,Carboniferous and Permian,were analysed for iron and manganese by atomic absorption spectrophotometry and observed under luminoscope. The results show the following. 1. Cathodoluminescence of carbonate minerals is mainly controlled by the absolute amount of manganese when the concentration of manganese is below 40 μg/g. Carbonate containing manganese less than 20μg/g will not luminesce. 2. Cathodoluminescence of carbonate minerals is mainly controlled by the absolute amount of iron when the concentration of iron is above 5 000μg/g. Carbonate containing iron more than 10000μg/g will not luminesce. 3. Cathodoluminescence of carbonate minerals is obviously controlled by Fe/Mn ratios when the concentration of manganese is above 40μg/g and concentration of iron is below 5 000μg/g . The samples with Fe/Mn ratios more than 30 display a generally weak luminescence, with Fe/Mn ratios less than 7 displlay a generally bright luminescence,and with Fe/Mn ratios between 7 and 30 display a generally moderate luminescence. In addition,the cathodoluminescence of carbonate minerals could be related to some rare earth elements which perhaps is the results of lower activated voltage and longer afterglow duration of some samples.