STEPPED-HEATING OF CARBONATES AND CARBON-BEARING QUARTZ GRAINS

Abstract

Stepped-heating, for the stable isotope analysis of trace quantities of light elements (such as C, N and H) has evolved from a technique used solely for the separation of components of different isotopic composition. By increasing the number of temperature steps (i.e. decreasing the temperature interval), the shape of the release profile can aid in the identification of the component in which the element is present. However, by increasing the number of steps there is in an increase in the duration of the experiment, thus automation is desirable.In anticipation of automation, simple models have been derived which simulate the type of results to be expected. The simplest of these is the breakdown of carbonates of the Group-IIA metals, which was considered to be first-order decomposition. The model was investigated by stepped-heating experiments on CaCO3, SrCO3 and BaCO3, and was subsequently applied to previous results, for the release of trace amounts of carbon, obtained from natural quartz samples.