Dinantian volcanism in Derbyshire was associated with minor phases of isostatic uplift of a shallow carbonate platform on the northern margin of the St. George's Land E-W land mass. The mainly tholeiitic magmas were generated by varying degrees of partial melting of heterogeneous mantle sources followed by fractional crystallization and final equilibration mainly within the lower crust. Large, high-level magma chambers were not established. Even single lava sequences, such as the Miller's Dale Lava, represent several, isolated magmatic phases. Volcanism was of within-plate type. Magmas generated in isolated mantle pockets rose to the surface through crust attenuated by lithospheric stretching.