Several of Earth's intra-plate volcanic provinces occur within or
adjacent to continental lithosphere, with many believed to mark the
surface expression of upwelling mantle plumes. Nonetheless, studies of
plume-derived magmatism have generally focussed on ocean-island
volcanism, where the overlying rigid lithosphere is of uniform
thickness. Here, we investigate the interaction between mantle plumes
and heterogeneous continental lithosphere using a series of geodynamical
models. Our results demonstrate that the spatio-temporal magmatic
expression of plumes in these continental settings is complex and
strongly depends on the location of plume impingement, differing
substantially from that expected beneath oceanic lithosphere. Where
plumes ascend beneath thick continental cratons, the overlying lid
locally limits decompression melting. However, gradients in lithospheric
thickness channel plume material towards regions of thinner lithosphere,
activating magmatism away from the plume conduit, sometimes
simultaneously at locations more than a thousand kilometres apart. This
magmatism regularly concentrates at lithospheric steps, where it may be
difficult to distinguish from that arising through edge-driven
convection, especially if differentiating geochemical signatures are
absent, as implied by some of our results. If plumes impinge in regions
of thinner lithosphere, the resulting asthenospheric flow regime can
force material downwards at lithospheric steps, shutting off
pre-existing edge-related magmatism. In addition, under certain
conditions, the interaction between plume material and lithospheric
structure can induce internal destabilisation of the plume pancake,
driving complex time-dependent magmatic patterns at the surface. Our
study highlights the challenges associated with linking continental
magmatism to underlying mantle dynamics and motivates an
inter-disciplinary approach in future studies.