Verma {GCDkit}R Documentation

Major-element based discrimination plots for (ultra-)basic rocks (Verma et al. 2006)

Description

Plots data stored in 'WR' (or its subset) into discrimination plots proposed by Verma et al. (2006) for (ultra-) basic rocks (SiO2 < 52 wt. %).

Usage

Verma(FeMiddlemost = FALSE, GUI = FALSE)

Arguments

FeMiddlemost

logical, should be iron adjusted according to Middlemost (1989)?

GUI

logical, is the function called from a GUI?

Details

Suite of five diagrams for discrimination of geotectonic environment of ultrabasic and basic rocks (SiO2 < 52 wt. %), proposed by Verma et al. (2006). It is based on log-transformed concentration ratios of major-element oxides. Note that prior to the transformation, the analyses are recast to 100% anhydrous basis. Each diagram is a plot of two discriminant functions, DF1 and DF2, respectively in x- and y-axes. Only samples with SiO2 < 52 wt. % are plotted. To work properly, the major-element analysis should be complete (SiO2, TiO2, Al2O3, Fe2O3, FeO, MnO, MgO, CaO, Na2O, K2O, P2O5). Following the recommendation by Verma et al. (2006), prior to the plotting can be performed an adjustment of the iron-oxidation ratio as proposed by Middlemost (1989) (see 'FeMiddlemost').

For the Fe2O3/FeO ratios implemented for individual rock types (based on TAS classification), see Verma et al. (2002) (Fig. 1).

Verma.png

Following geotectonic settings may be deduced:

Abbreviation used Environment
IAB island arc basic rocks
CRB continental rift basic rocks
OIB ocean-island basic rocks
MORB mid-ocean ridge basic rocks

Value

None.

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 Janoušek, vojtech.janousek@geology.cz

References

Middlemost EAK (1989) Iron oxidation ratios, norms and the classification of volcanic rocks. Chem Geol 77: 19-26. doi: 10.1016/0009-2541(89)90011-9

Verma SP, Torres-Alvarado IS, Sotelo-Rodriguez ZT (2002) SINCLAS: standard igneous norm and volcanic rock classification system. Comput and Geosci 28: 711-715. doi: 10.1016/S0098-3004(01)00087-5

Verma SP, Guevara M, Agrawal S (2006) Discriminating four tectonic settings: Five new geochemical diagrams for basic and ultrabasic volcanic rocks based on log-ratio transformation of major-element data. Journal of Earth System Science 115: 485-528. doi: 10.1007/BF02702907

See Also

FeMiddlemost Agrawal Plate Plate editing plotPlate figaro

Examples

    data(sazava)
    accessVar("sazava")
    
    # plot the diagrams
    plotPlate("Verma")

[Package GCDkit version 6.1 Index]