Cation Diffusion in Plagioclase Feldspar

See allHide authors and affiliations

Science  03 Aug 1984:
Vol. 225, Issue 4661, pp. 504-505
DOI: 10.1126/science.225.4661.504


Steep compositional gradients in igneous plagioclase feldspar from slowly cooled intrusive bodies imply a maximum value of the intracrystalline diffusion coefficient for NaSi [unknown] CaAl exchange, Dmax ∼10-20 centimeters squared per second for temperatures in the range 1250° to 1000°C. Millimeter-sized grains cannot be homogenized in all geologic time; hence reactive equilibrium crystallization of plagioclase from the melt does not occur in dry systems.