Figure 8: Model showing partial melting of subducted eclogite and how melt channels aid exhumation, feed crustal lavas and make seismic bright spots.
From: Partial melting of deeply subducted eclogite from the Sulu orogen in China
The elliptical insets a–d represent the progressive different stages and scales of partial melting of eclogite and melt segregation during exhumation. Eclogite begins partial melting by initial melt droplets forming along grain boundaries (a, scale bar, 50 μm), which then coalesce into 4–10 m wide intergranular veinlets (b, scale bar, 1 cm), which then move along foliation planes and extensional shear zones, eventually forming larger melt pockets in low-stress zones such as fold hinges between units with different rheologies (c, scale bar, 10 cm). Melts in these pockets then merge through interaction of melting and deformation, enhancing deformation in these zones, forming melt channels consisting of ~50% melt and 50% residual eclogite (d, scale bar, 1 m). Where these melt channels merge melts escape and form metre-scale dikes that may interact with melts derived from the gneisses and transport magma to higher lithospheric levels. SCLM, subcontinental lithospheric mantle; NCC, North China Craton.
