eArgon at Mac App Store analyse

This program facilitates the analysis and interpretation of argon geochronology data from step-heating experiments in vacuo in a furnace attached to a mass spectrometer. The program allows corrections for excess argon, using the analysis of Turner Plots to recognise trends. The program allows analysis of complex age spectra using the method of asymptotes and limits. Cumulated plots allow recognition of Frequently Measured Ages (FMAs). Gaussian plots present data using probability. Arrhenius Plots and Relative Radius Plots allow estimates for the diffusion parameters for individual samples. Data is input in XML format with data tags available for individual laboratories by request. The output document is in an XML format intended to become an industry standard, ensuring data interoperability between different programs and different laboratories.

All data is recorded in a single document using XML format, allowing recreation of the analysis, including isochrons, asymptotes and limits for individual spectra, and other parameters. Data for a single sample can be exported to the Wunderkind and MacArgon apps for inversion. Wunderkind uses 39Ar release data from ultra-high-vacuum (UHV) temperature-controlled step-heating diffusion experiments. MacArgon allows forward modelling of the effect of arbitrary pressure-temperature-time histories. Step colours are also saved in the eArgon document. A small screen format is also available for the Age Spectrum Window.

The weighted mean is used for isochrons on the age plot, using formula in Mahon 1996. If the MSWD is unacceptably high, a weighted average used instead reflecting the scatter of the individual steps [shown at the 2σ level] The Turner inverse 40Ar isotope correlation diagram uses the York 1969 regression as corrected by Mahon 1996 and Trappitsch 2018. The square root of the MSWD (Pearsons chi statistic) is used to assess the likelihood that the scatter in age is within the 95% probability limits defined using equations as set out by Wendt and Carl 1991 but here evaluating the approximations to the scatter distributions using the gamma function, and directly estimating the uncertainty in the chi-statistic.

The document-based architecture stores key aspects of the analysis of a set of argon age spectra, and for interpretation of associated argon isotope ratios. The weighted mean age is shown unless the scatter of the individual steps [shown at the 2σ level] nullifies the statistic . If the MSWD is too high to allow definition of a plateau segment the mean age is shown with the scatter of the mean ages of individual steps defining the uncertainty.

Each age step displays the overall 2-sigma uncertainty, with the systematic uncertainties in age related to uncertainties in the J-factor and the decay constant discernible during mouse over events. Statistical analysis based on a section of steps is now bifurcated depending on age scatter. The systematic age uncertainties due to J-factor uncertainty and decay constant uncertainty can be reapplied, using a first-order Taylor expansion. By default, input without control parameters occurs as though uncertainty related to teh J-factor has been included. Use the toolbox options to remedy matters, if this is not correct.

The toolbox contains many useful routines, including two options for the estimation of the loss of 39Ar as the result of recoil during irradiation, or loss during prior warming of a sample. Generally these values are low, but they can be higher than normal in fine-grained or in partially altered sample aliquots. There are "How to ..." documents in the Instructions Menu. 

There are options for selection of multiple datasets to allow synoptic plots, and allows for drag and drop reordering of a dataset collection.

Latest version eArgon: v9.0.0

Version §14 includes the option to make plots of the estimated diffusion parameters, either for a single dataset, or for a cumulated collection. These plots are based on analysis of the Arrhenius data. The values for each dataset (or as a collection when amalgamating to make a synoptic plot) are also shown in the Diffusion Parameters window. The option exists to add reference points based on data from hydrothermal experiments. Options are provided to correct for the prior loss of 39Ar due to neutron-collision-induced recoil during irradiation, or due to loss during cleaning of the aliquot by protracted warming. Version §14.2.3 corrects an issue with labelling the x-axis in a Gaussian plot. Version §14.2.4 allows points with abnormally low gas release and/or abnormally high error to be hidden. These points are then not included in a York regression when determining lines of best fit taking account of uncertainty on both axes.

Apps Changes History:

• New App Version 299.99 -> 0