EARTH232 Lecture Notes - Lecture 5: Partial Melting, Phase Diagram, Crystallization
26 Aug 2016
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Document Summary
Equilibrium crystallization: usually not the case in nature. Disequilibrium during crystallization: occurs due removal of crystals due to gravity settling, diffusion is not allowed. Results in compositional zoning: inner layers shielded from magma by new layers forming on top. Equilibrium and partial melting: melting is the exact opposite of the crystallization on the olivine phase diagram, equilibrium melting occurs only until enough melt has accumulated and then it moves upwards as a separate mas. Initially melt is accumulated along mineral grain boundaries due to cohesion and s=surface area tension. When enough melt accumulates then it moves upward. Partial melt, solid left behind as melt moves up. Melt is composed of lower t component (weaker bonds like fe) Olivine paragenesis: fo rich olivine (80-90) is one of the first phases to crystallize basaltic melts. Erupting volcanoes will have fo in phenocrysts surrounded by more rapidly cooled melt: partial melt of upper mantle mafic magma.
