Frost {GCDkit}R Documentation

Frost et al. (2001)

Description

Classification of granitic rocks proposed by Frost et al (2001).

Usage

    Frost(plot.txt = getOption("gcd.plot.text"), 
    clssf = FALSE, GUI = FALSE)

Arguments

plot.txt

logical, annotate fields by their names?

clssf

logical, should the samples be classified?

GUI

logical, is the function called from a GUI?

Details

Classification scheme proposed by Frost et al. (2001). It consists of three diagrams:

The classification is designed to work both with analyses distinguishing between ferrous and ferric iron (preferred) and those with total iron only. The dialogue box lets the user decide, whether to use the ferrous iron value or the total iron.

Similarly, if some P2O5 concentrations are missing in the dataset, the user is prompted whether the missing values should be replaced with zero. If not, the problematic analyses are not plotted/classified.

The following associations are distinguished:

ferroan, magnesian

alkalic, alkali-calcic, calc-alkalic, calcic

peralkaline, metaluminous, peraluminous

Frost.png

The geologically reasonable combinations, together with examples, are listed in the ../Diagrams/Geotectonic/FrostTable.html, modified from the original article.

In fact, the ASI vs. A/NK diagram (based on Shand (1943)) was not plotted in the paper, but it replaces the conditions mentioned in the text and is, in our view, more instructive.

Value

results

The function returns table of calculated coefficients (Fe-Number, MALI, ASI).

There are two values for the ASI: that labeled 'ASI' is calculated from molecular proportions of oxides, and is used for plotting and classification. The other one is labeled 'ASI_orig', and is calculated exactly as stated in the original paper (i.e. Al/(Ca-1.67P+Na+K).

Note

This function uses the plates concept. The individual plots can be selected and their properties/appearance changed as if they were stand alone Figaro-compatible plots.

See Plate, Plate editing and figaro for details.

Due to the specific design of this scheme (combination of multiple diagrams), the classification option is not available via the pull-down menus. Currently, the only way to apply Frost's classification in GCDkit on individual samples is to call the function manually from the Console: Frost_2008(clssf = TRUE).

Warning

Note that the Fe-number is calculated as weight proportion of FeO/(FeO+MgO) (or FeOtot/(FeOtot+MgO)). The approach used here should not be confused with the more common usage of the term "Fe-number" (as well as "Mg-number") for molecular proportions.

As approved by one of the authors (C. Barnes, pers. comm., 2008), the equation for ASI in the original work (Frost et al. 2001) was stated erroneously as molecular proportions of elements, instead of oxides.

Note

This function uses the plates concept. The individual plots can be selected and their properties/appearance changed as if they were stand alone Figaro-compatible plots. See Plate,

Plate editing and figaro for details.

Author(s)

Vojtěch Erban, erban@sopky.cz

& Vojtěch Janoušek vojtech.janousek@geology.cz

References

Frost BR, Barnes CG, Collins WJ, Arculus RJ, Ellis DJ, Frost CD (2001) A geochemical classification for granitic rocks. J Petrol 42: 2033-2048. doi: 10.1093/petrology/42.11.2033

Shand SJ (1943) Eruptive rocks, 2nd ed. John Wiley, New York, pp 1-444

See Also

Frost_2008 Shand classify Plate Plate editing plotPlate figaro

Examples

    data(sazava)
    accessVar("sazava")
    
    # Plot the diagrams
    plotPlate("Frost")

    # Classify the samples, suppress the graphical output
    Frost(clssf=TRUE, GUI=TRUE)

[Package GCDkit version 6.1 Index]