are often interpreted as evidence for the action of plate tectonics, these are not true boninites and non-plate tectonic models can also account for their formation. Texturally, the mafic metavolcanics include pillow lavas and pillow breccias, which indicate that the lavas erupted subaqueously, and requires the presence of surface water during the Eoarchaean. More felsic volcanic compositions have been observed, but it is not clear whether these represent volcanic or sedimentary rocks, and the only examples of potential andesite are significantly weathered. The mafic volcanic sequences contain abundant meta-ultramafic rocks, including amphibolites, serpentinites, carbonated-peridotites and peridotite. The majority of these are widely accepted to be intrusive in origin, representing ultramafic cumulates. Some peridotite lenses have been interpreted as obducted mantle fragments, and used as evidence to support the operation of plate tectonics during the formation of the Isua Greenstone Belt. However, this interpretation is contested, and some studies suggest that all peridotites at Isua are cumulates, representing shallow level magma chambers and conduits with the volcanic sequences. Metasedimentary rocks include banded iron formation and detrital quartzite, likely representing a metamorphosed siliciclastic sedimentary rock. Although they do not form part of the supracrustal belt itself, the belt is hosted in and in places intruded by tonalite-trondhjemite-granodiorite (TTG) orthogneisses. Tectonics The tectonic setting in which the Isua Greenstone Belt formed remains contentious. Ideas can be broadly divided into plate tectonic models, in which the belt formed in one of several possible tectonic settings that exist on the modern day Earth, and non-plate tectonic or non-uniformitarian models, in which the Isua Greenstone Belt formed in a tectonic regime that was different to the modern day Earth. Plate tectonic models can be further subdivided into those that argue that the Isua Greenstone Belt or parts of it represent an ophiolite, a sliver of obducted oceanic crust and mantle, and those that argue that the belt represents an accretionary prism, formed in a subduction zone. Non-plate tectonic models generally suggest a heat pipe or mantle plume origin for the belt. This forms part of a much broader debate about when plate tectonics emerged on Earth, and whether the Archaean Earth operated under a fundamentally different tectonic regime. Ophiolite controversy Furnes et al. (2007) suggested that the presence of pillow lavas and closely spaced parallel dykes indicated that the Isua Greenstone Belt represented an ophiolite. The interpretation of the parallel dykes as a sheeted dyke complex