Abstract

The compositions of Earth materials are usually described in terms of specific components, normalised to a whole. This means that individual components must always be positive, and their sum cannot exceed 100%. While these properties are obvious, their wider implications are often misunderstood. In this talk, I will first show how most geochemical datasets are not nearly as amenable to standard statistical analysis and interpretation as they may initially appear. I will then show how the magic of log-ratios can help us to address these difficulties. Finally, I will discuss the physico-chemical meaning of log-ratios and give some examples of how they can be used to better describe, understand, and model various geochemical fractionation processes. This will inevitably raise questions regarding the standard, classical approaches still used for these tasks.