This study deals with the interaction between deformation and magmatism in mid- to deep-crustal
domains. The relation is analysed between migmatites and shear zones and the spatial distribution of leucogranitoid
veins and dykes running through a footwall migmatite system, and reaching a transtensional
shear zone operated under amphibolite- to greenschist-facies metamorphic conditions (Boa Fé shear zone,
Variscan belt, SW Iberia). Statistical results show that the frequency of width and spacing of the leucogranitoid
dykes conform to power-law distributions comparable with observations in volcanic systems. The fractal
geometry of the distribution of leucogranitoid dykes highlights the development of a dense framework of
thinner weakly or non-mineralized veins and dykes formed at higher nucleation/growth ratios in the footwall
migmatite system that contrasts with the emplacement of thicker dykes associated with strongly mineralized
thinner veins within the shear zone. The volume of injected leucogranitoid dykes in the shear zone is lower
as compared with the footwall and is comparable with an expanding footwall shear zone with non-coaxial
flow and volume increase. The Boa Fé shear zone seems to form a physical barrier to the transport of magma to the hanging wall