Are the Granites at Dartmoor, migmatitic or magmatic in origin?

Granite is magmatic in origin. Part of the definition of a granite is "an igneous rock". Part of the definition of an igneous rock is "formed from a melt". Part of the definition of a migmatite is "a metamorphic rock with inclusions of melted rock". Since granite is not a metamorphic rock it cannot be migmatitic in origin.