Mixed metamorphic and fluid graphite deposition in Palaeoproterozoic supracrustal rocks of the Lewisian Complex, NW Scotland

Graphite deposits may form alternatively by metamorphism of sedimentary rocks and from fluids. Both types occur in supracrustal successions within the Lewisian Complex Northwest Scotland, similarly Palaeoproterozoic across North Atlantic region Canada, Greenland Scandinavia. Carbon isotope compositions show that graphite Scotland had a mixed origin organic matter (schists) decarbonation limestones (marbles). Raman spectroscopy shows most exhibits some structural disorder, unlike complete order vein ore region. Exceptionally, where was precipitated fluid, albitized rock Tiree Scardroy, it is fully ordered. While survive granulite facies without being transformed to ordered graphite, can yield commercially more valuable when mobilized fluid.