Investigations of individual fluid inclusions with the Heidelberg proton microprobe — A nondestructive analytical method

Abstract

To obtain chemical information on geologic fluids, we have used the Heidelberg proton-induced X-ray emission (PIXE) microprobe on fluid inclusions. The high penetration of the protons makes the proton microprobe an ideal tool for nondestructive elemental analysis of individual fluid inclusions inside the crystals. Principally, it is possible to detect elements with atomic numbers ( Z) ⩾ 11, corresponding to Na, which in reality is matrix dependent. Between atomic number, matrix, beam and limit of detection there are distinct relationships. The detection limit is more sensitive for higher atomic numbers. Therefore it is possible to analyze heavier elements, e.g., Fe, Br and Sr, in inclusions at a depth of 5–40 μm beneath the sample surface. For investigations with PIXE the same samples can be used as for fluid inclusion studies. Therefore it is possible to collect microthermometric data and to study chemical composition of fluid inclusions within the same sample. Results of qualitative chemical analysis of fluid inclusions in quartz are presented. Resulting calculations as a function of the depth are presented and upcharging problems due to destroyed carbon coating are outlined.