Fig. 2: Evolving approaches to oxygen isotope analysis.

a Photograph of a lava sample from Merapi with visible feldspar and clinopyroxene phenocrysts. Conventional fluorination (CF) is typically utilised to analyse oxygen isotope ratios of pulverised bulk lava and/or mineral separates. b Extended focus images (EFI) of polished clinopyroxene crystals in Agung and Batur lavas showing internal features such as mineral and melt inclusions. Laser fluorination (LF) is typically utilised to analyse oxygen isotopes in single minerals or mineral separates. c Back Scattered Electron (BSE) image of a clinopyroxene mineral grain from Batur in topographic mode showing surface features. Although this grain also contains mineral inclusions exposed at the polished surface, these are easily avoided with SIMS due to the high degree of spatial control. Abbreviations: Cpx, clinopyroxene; Fsp, feldspar; MS, mass spectrometry; Mt, magnetite.