Ar ar dating method
The zero value problem can be avoided by performing generalised linear regression of the ratios (using a logarithmic link function to ensure positive intercepts, Nelder and Wedderburn, 1972), or to cast the regression problem into a more sophisticated maximum likelihood form (Wood, 2015).A comprehensive discussion of these alternative methods falls outside the scope of the present paper and will be deferred to a future publication.Sample irradiation is presently performed at the Geesthacht Neutron Facility (Ge NF) at the GKSS research centre.
In section samples, the UV pulsed laser is able to ablate spots with minimum diameters of a few tens of micrometers.
They occur as a result of mass fractionation corrections and detector inter-calibrations (Section 5).
They arise when accounting for the effect of radioactive decay on Ar (from Ca) (Section 7), or whenever an interference correction is made (Section 8).
The important point which needs to be made here is that Equations 6-11 only contain ratios, and do not depend on the absolute abundances of the different argon isotopes.
In statistical terms, Ar-measurements are said to be ‘compositional data’ and are subject to the peculiar mathematics of the compositional dataspace or ‘simplex’ (Aitchison, 1986).