At Seathwaite there is major deposit of graphite. The graphite appears as pipes and veins associated with a diorite intrusion, presumed to be of Caradoc age. Organic-rich sediments in the Skiddaw Group mudstones are considered the likely source for the carbon. These high-temperature veins were probably deposited from aqueous fluids rich in carbon dioxide and methane driven by the effects of the dioritic intrusion.