Experimental results are presented for eighteen experiments exploring
multicomponent chemical-diffusion in basaltic liquids. Experiments wer
e performed in Columbia River Basalt (CRB) composition doped with abou
t 5 wt% SiO2, TiO2, Al2O3, FeO, MgO, and CaO, under reducing condition
s at 1 atm., at 1473 K, 1573 K, and 1723 K. Results indicate that diff
usion behavior in CRB compositions is consistent with a simple Fick's
law formulation. This Fickian behavior in CRB compositions contrasts w
ith more complicated diffusion behavior observed in MgO-Al2O3-SiO2 and
CaO-MgO-Al2O3-SiO2 melts. Results of CRB experiments are combined to
calibrate a diffusion matrix (D) in CRB liquids at 1473 K, 1573 K, and
1723 K. Our D estimates indicate negative coupling between CaO and bo
th FeO and Al2O3 components, though diagonal elements still dominate.
These general features persist across the temperature range considered
. Self- and tracer-diffusion data from the literature are used with th
e predictive model of Richter (1993) to estimate a D matrix at 1573 K.
The resulting matrix does not compare well with our measured 1573 K d
iffusion matrix. It cannot be established if this discrepancy indicate
s a failure of the Richter (1993) model, or merely reflects deficienci
es in the available tracer- and self-diffusion data, or limitations in
the melt activity model. Effective Binary Diffusion Coefficients (EBD
C) were also estimated for TiO2, Al2O3, FeO, MgO, CaO at 1473 K, 1573
K, and 1723 K. These EBDC estimates are used to constrain a polytherma
l Arrhenian model for the prediction of EBDC values at super-liquidus
temperatures. Results of experiments on alkali diffusion in CRB compos
itions are included to add Na2O and K2O to the polythermal EBDC model.