238 IGNEOUS ROCKS/Granite Figure Granitic rocks in the field (A) Migmatite outcrop from south eastern Australia, showing the deformation enhanced segregation and accumulation of locally derived partial melts into a dilatant shear zone In this case, the leucogranite in the shear zone is compositionally equivalent to the kilometre scale leucogranitic plutons of the area (B) Strongly peraluminous leucogranite invading and stoping its metasedimentary roof rocks along bedding planes and cracks (Cornwall, UK) (C) Enclaves of gneiss and migmatite in a deep crustal (ca 20 km) granitic pluton in south eastern Australia that has been retained close to the generative region The enclaves correspond to less fertile horizons of the granite’s source rocks (D) Mingling between a syn plutonic basaltic dyke and a metaluminous tonalite, Moruya Batholith, eastern Lachlan Fold Belt (Australia) (E) Composite enclave, in which a mafic igneous enclave (basaltic andesite) is enclosed by a microgranular enclave Note the physical incorporation of potassium feldspar pheno crysts from the enclosing granite (Elba Island, Italy) (F) Thin section of a microgranular enclave, showing a large quartz grain rimmed by pyroxene, which is overgrown in turn by hornblende (3 mm across) The quartz grain is interpreted as a xenocryst incorporated from the host granite, which reacted with, and was partially resorbed by, the hotter enclave magma (G) Unusual vortex like structure in granitic rock, which is thought to represent a cross section through a magma flow conduit that has subsequently been ‘infilled’ by crystal rich magma during crystallization Features such as this hint at the dynamic nature of upper crustal magma chambers and demonstrate how considerable compositional heterogeneity can be caused by simple magmatic flow processes in granitic crystal mushes (Elba Island, Italy)