Disequilibrium mantle melting

摘要: Abstract The attainment of equilibrium between basalt and residual peridotite depends on the relative magnitudes melt segregation rate solid residue re-equilibration rate. Garnets pyroxenes (and perhaps spinels) require at least 103 years to equilibrate with by volume inter-diffusion. Percolation velocities in porous (1–10%) mantle rocks are order 10−4 10−8 cm/s. If moves homogeneous percolation, then a column matrix several kilometers height must interact for an partitioning elements be achieved. also involves flow through dykes, as seems likely, time available equilibration is even shorter, disequilibration melting expected. By varying residues remain contact, variable will ensue. This can produce crossing REE profiles basalts derived identical degrees from sources. Basalt-depleted disequilibrium have fractionated profiles. provides alternative “cryptic” metasomatism enigmatic decoupling major trace that observed many nodules.