Ocean rises are products of variable mantle composition, temperature and focused melting

Focused Mantle Upwelling below Mid-ocean Ridges Due to Feedback between Viscosity and Melting

We present the first internally consistent calculation which leads to a narrow 'conduit' of rapid vertical advection and melting of mantle under a spreading center. In this model, mantle flow is driven by plate separation and compositional buoyancy. Melt segregation is described as flow through a permeable media. The major new feature is that the viscosity of the mantle is considered to be a st...

Major element chemistry of ocean island basalts — Conditions of mantle melting and heterogeneity of mantle source

Continuous eclogite melting and variable refertilisation in upwelling heterogeneous mantle

Large-scale tectonic processes introduce a range of crustal lithologies into the Earth's mantle. These lithologies have been implicated as sources of compositional heterogeneity in mantle-derived magmas. The model being explored here assumes the presence of widely dispersed fragments of residual eclogite (derived from recycled oceanic crust), stretched and stirred by convection in the mantle. H...

Redox systematics of a magma ocean with variable pressure-temperature gradients and composition.

Oxygen fugacity in metal-bearing systems controls some fundamental aspects of the geochemistry of the early Earth, such as the FeO and siderophile trace element content of the mantle, volatile species that influence atmospheric composition, and conditions for organic compounds synthesis. Redox and metal-silicate equilibria in the early Earth are sensitive to oxygen fugacity (fO(2)), yet are poo...

Origin of Lherzolitic Peridotites in Ab-Bid Ultramafic Complex (Hormozgan Province); Products of Mantle Metasomatism or Partial Melting Processes?

Lherzolite is one of the main units in the Ab-Bid ultramafic complex from Esfandagheh-HadjiAbad coloured mélange (South of Iran). The complex contains harzburgite, dunite, lherzolite and pyroxenite dykes and the lherzolites mainly occur in the margins. In the field, lherzolites occur as weakly foliated coarse-grained peridotites with shiny pyroxene grains and cut by neumerous pyroxenitic veins....