Relationships between μm-scale melt inclusions and oscillatory trace element zoning in olivine

Oscillatory zoning of trace elements P, Cr and Al in otherwise unzoned magmatic olivines may preserve information on early crystallisation histories [1, 2], because the higher diffusivities of Mg, Fe, Mn, Ca and Ni inhibit preservation of such clues in the major and minor elements. Concentrations of P in trace-element-rich bands exceed expected equilibrium values, and similar enrichment bands are observed in olivines grown experimentally at constant cooling rate [2]; thus, it seems likely that this phenomenon in natural olivine reflects local kinetic processes during crystal growth rather than oscillations in magma temperature or bulk composition.