Multiple Nuclide Analysis

ACE contains a small routine for the analysis of multiple nuclide samples. For a sample from which 2 different cosmogenic nuclide inventories are measured, additional information regarding erosion and inheritance can be recovered.  To demonstrate this utility we calculate ages for the 26Al and 10Be samples (TI2 and TI3) and experiments (10Be Demonstration Expt, 26Al Demonstration Expt) provided with ACE.  Results should look like this:

Click on image to expand

Click on image to expand

The theory of multiple nuclide techniques originates from Lal (1991) who assumed time invariant production rates.  Therefore when a sample is dated using time varying production rates, a time invariant production rate is also calculated for use in this routine.  The sample attribute ‘Production Rate Invariant’ for a sample with cosmogenic inventory N and age t is calculated as:

Where is the decay constant of the nuclide.  For stable nuclide the invariant production rate is the inventory divided by the sample age. With the default value of mu = 1/500 (mm) from Lal 1991 the cosmogenic inventory and time invariant production rates are used to estimate erosion rates and prior exposure. To run the analysis, highlight (click, hold and drag) the samples which have different nuclide results:

When selected, the utility ‘Multiple Nuclide Analysis’ can be selected.  A result window will open:

Click on image to expand

Click on image to expand

For sample TI3 the ratio of cosmogenic inventories suggests prior exposure of the sample.  In ACE, the maximum recent exposure is then calculated.  For sample TI2 a different result is obtained:

Click on image to expand

Click on image to expand

As for the other figures in ACE these can be panned and zoomed to see greater detail:

Click on image to expand

Click on image to expand

For samples which fall within the erosion region (the ‘Banana’ in these figures defined as the area between the red line (of zero erosion) and blue line (of steady state erosion).  In this case an erosion rate and age are calculated, which can be verified by reentering the sample details adding that erosion rate and recalculating.

To watch a movie of this procedure click here (requires Quicktime).

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