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2.3.26  Degassing Patterns Toolbox

The degassing of whole rock and basaltic groundmass samples during incremental heating experiments can be rather complex (for example Koppers et al. 2000 and 2004). The Degassing Patterns Toolbox is provided to you to better study and understand these degassing behaviors. In the example below of a submarine groundmass sample, the measured intensities of four argon components are shown, as indicated by the orange, purple, light blue and green buttons in the Select Argon Components panel. This is an interesting view of the degassing behavior of this sample, but the signal is rather erratic and the high intensity for the 40Ar(r) Component forces the other components to be nearly invisible near the bottom axis. This view becomes much more useful, if we normalize the signal (i.e. intensity) to the step size, as shown in the second example below. The 40Ar(r) Component now closely resembles the shape of the age spectra, which is what we are expecting, yet its intensity still overwhelms the other components. This problem gets alleviated as well, if we plot the degassing patterns as fractions over the entire experiment. This is shown in the third example below and clearly brings forward the low intensity components in the same plot. As it turns out, this experiment shows large spikes in the 36Ar(a) and 38Ar(cl) Components for the low temperature increments and another spike in the 37Ar(ca) Component for the high temperature increments. These are very useful observations that will help you in the interpretation of complex argon age spectra.

Select Argon Components
To select or deselect certain Argon Components, click either on the buttons or make your selections in the list box on the left-hand side. You can also use the buttons beneath this list box to Select All or Deselect All. The colors of the selected buttons correspond to the colors of the lines in the diagram.

Calculation Mode
By default the data are plotted against the Cumulative Amount of 39Ar(k) Released. However, you can also display the data against the Increment Temperature in case of a incremental heating experiment. Select one of the two checkboxes to change between these modes. Freeze Scales is helpful when you want to save the scaling settings between different toolbox sessions. You can also select the Show Age Plateau checkbox, which will add a horizontal bar to the plot, indicating the position of the age plateau. Check the Normalize Data checkbox if you want the normalize the intensities measured against the step size or the amount of 39Ar(k) in each increment. And, finally, you can disable the automatic updating of the plot and do a Manual Calculation. In that case use the Recalculate button to update the calculations.

Scaling
To manually scale the plot, change the numbers in the Scaling panel and click on the Change button. If you want to retain these customs settings between different toolbox sessions, be certain to check the Freeze Scale checkbox.

Note   If you click on the Default Patterns button, the settings get changed to return a similar plot as shown above. When you close the dialogbox, your latest settings will be remembered and used the next time you view the Degassing Patterns.