Application of addition HClO4 to improve the dissolution process and sensitivity of Os for low-concentration of Os in pyrite

Abstract

The rhenium (Re) and osmium (Os) isotope systems have long been recognized as effective tools to directly date mineralization and trace the source of metals. In general, 0.4 g of pyrite was dissolved by 11 mL of inverse aqua regia in a 30-mL Carius tube. Larger volumes of acids and a larger Carius tube were required if the sample weight was over 0.4 g. Herein we present an improved dissolution process of the Carius tube digestion method by adding HClO4 to dissolve larger sample weights in smaller volumes of acid. This approach is more suitable for determining low concentrations of Os in metal sulfides. In detail, 0.4 g of pyrite was completely dissolved in a mixture of 1 mL of HClO4 and 3 mL of inverse aqua regia. Notably, addition of 1 mL of HClO4 to 8 mL of inverse aqua regia significantly increases the amount of sample from 0.4 to 0.8 g. Based on our data, while the sample weight was no >0.8 g, addition of 1 mL of HClO4 to inverse aqua regia can not only improve the dissolving capacity significantly, but also avoid Carius tube explosion. Furthermore, the dissolving capacity of HClO4-inverse aqua regia method is much higher than that of H2O2-inverse aqua regia method, which is a typical digestion method for Re-Os dating. This method was certified by reference materials (HLP and JDC). In brief, this new method allows dissolution of larger amounts of sample while consuming less acid. Therefore, this method has more potential for determining low concentrations of Re and Os in metal sulfides.