Author name: Stearns A. Morse

Radiogenic isotope ratios can be used as a kind of petrogenetic “DNA” to identify the source components of magmas. Technical advances allowing us to measure isotopic compositions at the sub-crystal scale have led to the realisation that many magmatic rocks are isotopically heterogeneous. Crystals traditionally regarded as phenocrysts grown from the host magma have now been shown to be wholly or partly out of isotopic equilibrium with the glass or groundmass in which they are contained. Many of these crystals are likely to be recycled from earlier cumulates. Combining these fingerprinting techniques with the other approaches described in this issue offers an unprecedented opportunity to understand the processes and timescales through which magmas are assembled, differentiated and delivered to sites of eruption or emplacement.

Igneous rocks display a large and varied range of textures and compositions, reflecting complex magma pathways, differentiation processes and cooling histories. Integrating geochemical analyses with petrographic and textural information allows us to gain valuable insights into the details of the magma system: the rock’s texture serves as a window into the crystallization history of the magma, while the compositions of the components (crystals and glass) document the conditions and pathways of evolution. In this issue of Elements we take a look at the frontiers in igneous petrology, focussing on the state of the art in textural and microgeochemical analysis and on how we can use some of the latest approaches to unravel the complexities of the magmatic system.