Calculation of Compound APFs
The program will automatically calculate the compound APF based the actual concentrations of the sample and the end-member APFs from the Empirical APF dialog. The calculation for compound APFs is shown here:
Where:
is the binary (end-member) APF
for elements other than the affected element
is the weight fraction for
elements other than the affected element
is the sum of all elements other
than the affected element
A further normalization is performed on the compound APF to ensure that in situations where the partial sum is very low, the compound APF is not over applied to the affected (pure) element when only the trace elements are varying in precision. This calculation is show here:
Note that this APF normalization correction is only applied when the absolute value of the scaling factor :
is greater than or equal to 1.0 to avoid problems with over applying the correction on major elements.