The geodynamic regime(s) that predominated during the Archean remains controversial, with the plethora of competing models largely informed by the felsic lithologies. Ultramafic–mafic rocks displaying distinctive geochemical signatures are formed in a range of Phanerozoic geotectonic environments. These rocks have high melting points, making them potentially useful tools for investigating Archean geodynamic processes in highly metamorphosed regions. We present the results of field mapping, petrography, traditional bulk-rock geochemistry and platinum group element geochemistry for 12 ultramafic–mafic bodies in the Lewisian Gneiss Complex, which is a highly metamorphosed fragment of the North Atlantic Craton in NW Scotland. Our data indicate that most of these occurrences are layered intrusions emplaced into the tonalite–trondhjemite–granodiorite-dominated crust prior to polyphase metamorphism, representing a significant re-evaluation of the magmatic evolution of the Lewisian Gneiss Complex. Of the other occurrences, two remain ambiguous, but one (Loch an Daimh Mor) has some geochemical affinity with abyssal/orogenic peridotites and may represent a fragment of Archean mantle, although further investigation is required. The ultramafic–mafic bodies in the Lewisian Gneiss Complex thus represent more than one type of event/process. Compared with the tonalite–trondhjemite–granodiorite host rocks, these lithologies may preserve evidence of protolith origin(s), with potential to illuminate the tectonic setting(s) and geodynamic regimes of the early Earth.

Supplementary material: Bulk rock geochemical data is available at:

You do not have access to this content, please speak to your institutional administrator if you feel you should have access.