A reappraisal of decrepitation-inductively coupled plasma spectroscopy (D-ICP) for the bulk analysis of fluid inclusions in minerals

Abstract

The complexity of fluid inclusions in minerals as an analytical object has led to the development of several analytical methods to address this issue. The aim of the present study was to specify the field of application of the Decrepitation-Inductively Coupled Plasma Spectroscopy (D-ICP) technique in comparison with the other contemporary methods of fluid inclusion analysis. In this study, the analytical train included a “decrepitator” between the nebulizer and the plasma torch. The heating element was a fast operating (∼400 grad per min) “nude” oven, ensuring a well-reproducible heating program. The time-resolved evolution curves of Na, K, Li, Ca, Mg, Al, Cu, Zn, Fe, Mn and Pb featured a single, well-shaped maximum at ca. 300 °C, which fitted also the maximum peak in the decrepigrams. S and As appeared at higher temperatures (T > 500 °C), probably due to the thermal decomposition of sulphide microimpurities in the quartz sample. The elemental ratios of X/Na (X = chemical element) were found to be independent from the sample mass (0.1–3.0 g) or the size of the mineral grains (0.10–1.60 mm), which is good proof of the relationship between decrepitation and the formation of the analytical signal. Both the quoted results did not differ significantly and actually can be pooled in a single body of evidence. Data from analyses of the fluid inclusions in the standard quartz obtained by three independent methods – bulk (D-ICP-AES and D-(C-)leach-AAS) and local (LA-ICP-MS) – were compared. It is concluded that D-ICP-AES is capable of supplying reliable information on the chemical composition of fluid inclusions.