ArArRedux - Rigorous Data Reduction and Error Propagation of Ar40 / Ar39
Data
Processes noble gas mass spectrometer data to determine
the isotopic composition of argon (comprised of Ar36, Ar37,
Ar38, Ar39 and Ar40) released from neutron-irradiated
potassium-bearing minerals. Then uses these compositions to
calculate precise and accurate geochronological ages for
multiple samples as well as the covariances between them. Error
propagation is done in matrix form, which jointly treats all
samples and all isotopes simultaneously at every step of the
data reduction process. Includes methods for regression of the
time-resolved mass spectrometer signals to t=0 ('time zero')
for both single- and multi-collector instruments, blank
correction, mass fractionation correction, detector
intercalibration, decay corrections, interference corrections,
interpolation of the irradiation parameter between neutron
fluence monitors, and (weighted mean) age calculation. All
operations are performed on the logs of the ratios between the
different argon isotopes so as to properly treat them as
'compositional data', sensu Aitchison [1986, The Statistics of
Compositional Data, Chapman and Hall].
