Abstract Petroleum systems within rifted margin basins affected by volcanism continue to remain challenging for the exploration of hydrocarbons, most notably owing to the volume of intrusions that pose imaging, drilling and exploration problems. Typically, intrusions possess small thermal aureoles, but despite this, there is evidence that intrusions could none the less be responsible for the generation of commercial volumes of hydrocarbons. Here we shed new light on this petroleum systems challenge by integrating organic geochemical and Raman spectroscopic techniques to produce potential volumetric data for hydrocarbons generated as a result of igneous intrusion. The results indicate that, in areas with immature source rock intervals, it may be possible for intrusions to generate volumes of oil that would be capable of comfortably filling likely known oil reservoirs. This is a critical step forward in integrating several analytical techniques, indicating that under the right conditions there is the potential for hydrocarbon generation as a result of igneous intrusion.

Abstract Archibald Geikie’s (1835–1924) field research led to better understanding of geological relationships and, ultimately, Earth processes. We consider three pieces of research in Scotland, from his early work on Skye through to the execution and impact of his 1860 expedition to the NW Highlands with Murchison, returning to Skye to consider arguments with Judd on igneous relationships. We describe the field locations and place modern interpretations in their historical context. We discuss how methods and approaches for building interpretations in the field were modified and improved through debates. Reliance on a few ‘critical outcrops’ served to anchor interpretation at the expense of understanding more complex exposures. Similar bias appears to have arisen from using simple exploratory transects which were only mitigated by proper mapping approaches. Significant misunderstandings between protagonists appear to have arisen through the reliance of text description rather than diagrammatic illustrations. The vitriolic nature of debate seems to have anchored misinterpretations, obscured interpretational uncertainty and promoted false-reasoning by inhibiting inclusive scientific engagement.