Quantitative analysis of fluid inclusions by particle-induced gamma-ray emission

The particle-induced gamma-ray emission (PIGE) method, very sensitive for the light elements Li, Be, B, F, Na, is complementary to the PIXE method for the determination of trace elements in complex materials. The deep penetration (more than 50 mm) of 3 MeV protons in light matrices allows heterogenities situated under the irradiated surface of the target to be revealed. This facility is exploited in earth sciences mainly to characterize in situ the fluid inclusions placed on the ion beam path. The quantitative PIGE analysis of the fluid requires a calibration valid for any inclusion of any thickness and at any depth. In this paper, the concentration of a light element is calculated in an occluded fluid by comparison to that of a homogenous massive mineral taken as a standard. An application is given on the quantitative determination of F in fluid inclusions in corundum by comparison to a topaz gemstone standard. A discussion follows on the choice of the energies at which the stopping power of the traversed materials is taken for the calculation of the concentrations.