Techniques of the Correction of Melt Inclusion Compositions for Boundary Layer Effects

Sergey Trousov (serg@students.web.ru) & Pavel Pletchov (pavel@cs.ru)

Room A-402,Geological Department, Moscow State University, Vorobievi Gori, Moscow,119899,Russia, Russia

It's well known, that at growth of crystals there is the boundary layer near growing surface, distinguished from melt composition on a distance from this surface. Width of this layer is depending on melt viscosity and growth conditions from 10-15 micron (for basalt melts) up to 100-150 microns (for viscous rhiolitic melts). The melt inclusion at formation should partially grasp a melt portion from this layer (Lu et al., 1995). The obtained experimental data on melt inclusion growth (Pletchov et al.,1997), study of boundary effects in natural glasses and melt inclusions allow to take into account influence of boundary effects on the basis of multi-component diffusion model (Oishi, 1965) of a boundary layer. The account of complete model of a boundary layer is complicated and requires attraction of a numerous of uncertain parameters, such as diffusion coefficients of ionic complexes in the melt. The semi-empirical approach for correction calculation based on study of glassy melt inclusion zonation is offered. The correction on boundary effects is similar in a quantitative sense adjusted for the host mineral crystallization inside inclusion at main components calculation, but essentially differs for trace elements collecting in a boundary layer proportional diffusion ability and Kd between melt and the host-mineral. The boundary effects calculation, probably, will allow reduce significant disorder of the trace element contents in melt inclusions.

Lu F.Q., Anderson A.T., Davis A.M., Journal of Geology, 103, 591-597, (1995).

Plechov PYu, Kotelnikov AR, Experiment in Geosciences, 6, 48-51, (1997).

Oishi Y, Journ. Chem. Phys, 46, 1611-1620, (1965).

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Reported at EMPG VIII , 16th - 19th April, 2000, Bergamo, Italy