Spidergram

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Import geochemical datasets from databases or from mass spectrometer output files, reorder and normalize to produce geochemical spider diagrams.

A spider diagram (spidergram) in geochemistry is a category plot of element concentrations. Typically whole-rock compositions are normalized by dividing by corresponding element concentrations in some parental composition; basaltic oceanic crust might be normalized to CI chondrite meteorites, for instance. This normalization removes the Oddo-Harkins 'odd-even' effect on element abundances arising from nucleosynthetic processes. The elements are usually ordered according to their 'compatibility', i.e. in order of their enrichment in the rock type relative to its source. Anomalous patterns can then be used to fingerprint specific processes of interest.

To create the plot thus requires reordering and looking up of reference data for normalization. This package aims to facilitate that part of the process. The aim is to output normalized data in the correct order for plotting, with the option of making a template spidergram plot that can be tweaked into the desired style of plot.

How to use

  • Select "spidergram" from Macros menu.
  • Easily import data by copying from a spreadsheet and pasting into the spidergram panel.
  • Select data waves, element order and normalizing scheme in the data selection and data treatment areas of the panel to preview output.
  • Click 'Do it' to save the reordered and normalized data in a subfolder.

If you'd like to test the package but don't have any geochemical data to hand, visit the PetDB database at http://www.earthchem.org/petdb. I used the MORB and mantle xenolith compilations for testing. Note that if you select many hundreds of analyses from one of these large data compilations it make take some time to import the data and to display large numbers of traces.

Limitations

Units for all data must be the same - i.e. can't mix ppm and wt.%.
Entries on the line (or column) containing categories (elements) cannot be interpreted if they contain ambiguous text or incorrectly capitalized symbols (though the package is tolerant of mixed numerals and text, e.g. "57Fe", such as you might find in text files exported from a mass spectrometer).

Compatibility

Not tested with Igor 6. You might get it to work, but you're on your own for importing data (try pasting into a table window).

Releases

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