The history of crustal evolution deciphered through exploration and analysis of accessory minerals

Abstract

Accessory minerals are those that do not contribute to the definition of a rock species. These minerals can act as carriers of trace elements, recording the geological environments experienced by the host rock during its formation and evolution. Some accessory minerals, being carriers of radioactive elements, can be used for geochronological studies. This presentation highlights zirconium minerals in ultramafic rocks, a topic that has seen increased understanding in recent years. Zircons in ultramafic rocks have diverse origins: some are magmatic, others precipitate through metamorphism or metasomatism, are mechanically incorporated, or undergo further metamorphism and metasomatism within the ultramafic rocks. Thus, the analysis of zircons in ultramafic rocks can decode not only magmatic processes but also chemical interactions between the crust and mantle. When interpreting the evolution of geological bodies through the analysis of accessory minerals with diverse origins, it is crucial to focus on heterogeneities such as boundaries and veins. It is preferable to analyze accessory minerals in situ within their host rocks whenever possible. In addition to traditional thin-section observations, utilizing techniques such as micro-XRF for rapid and large-area elemental imaging will be essential for the efficient exploration of accessory minerals.