ANALYSIS OF VOLCANIC SAMPLES BY ALPHA-PARAMETER METHOD ESTABLISHED FOR CORRECTING PIXE MEASUREMENTS

The cooling down of volcanic gases produces deposits of condensed mineral phases (sublimates, incrustations) at the volcano-atmosphere interface. The analysis of these deposits presents a high volcanological interest. The procedure of fractional condensation, used to obtain the samples, gives generally very small amounts of materials and this explains the scarcity of suitable analytical methods. Efforts to prepare samples for XRF or AAS analysis failed because of the presence of insoluble chemicals and because of the necessity to avoid heating the material. PIXE analysis proved to be successful by using intermediate thickness samples and the new α parameter correction method for matrix effects. The analytical procedure is described and the results and their volcanological significance are given. © 1990.