FeMiddlemost {GCDkit}R Documentation

Adjustment of Fe oxidation ratio (Middlemost 1989))

Description

Auxiliary function performing adjustment of the iron-oxidation ratio as proposed by Middlemost (1989).

Usage

FeMiddlemost(anhydrous = TRUE)

Arguments

anhydrous

logical; should be returned major-element analyses recast to anhydrous basis?

Details

This function performs an adjustment of the iron-oxidation ratio for individual volcanic rock types as proposed by Middlemost (1989).

The classification is based on TAS classification (Le Bas et al. 1986, Le Maitre et al. 1989).

The Fe2O3/FeO ratios for individual rock types, based on Verma et al. (2002) (Fig. 1), are as follows:

foidite, Na2O+K2O <= 3 0.15
foidite, 3 < Na2O+K2O <= 7 0.2
foidite, 7 < Na2O+K2O <= 10 0.3
foidite, Na2O+K2O > 10 0.4
picrobasalt 0.15
basalt 0.2
basaltic andesite 0.3
andesite 0.35
dacite 0.4
rhyolite 0.5
trachybasalt 0.3
basaltic trachyandesite 0.35
trachyandesite 0.4
trachyte/trachydacite 0.5
tephrite/basanite, Na2O+K2O <= 6 0.2
tephrite/basanite, Na2O+K2O > 6 0.3
phonotephrite 0.35
tephriphonolite 0.4
phonolite 0.5

If the parameter 'anhydrous' is set, returned are the major-element data recast to 100 % anhydrous basis.

Value

A matrix with adjusted whole-rock chemical data.
No permanent changes to either 'WR' or 'WRanh' are made.

Author(s)

Vojtěch Janoušek, vojtech.janousek@geology.cz

References

Le Bas MJ, Le Maitre RW, Streckeisen A & Zanettin B (1986) A chemical classification of volcanic rocks based on the total alkali-silica diagram. J Petrology 27: 745-750 doi: 10.1093/petrology/27.3.745

Le Maitre RW et al (1989) Igneous Rocks: A Classification and Glossary of Terms, 1st edition. Cambridge University Press

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

See Also

TAS Verma

Examples

    data(blatna)
    accessVar("blatna")
    
    FeMiddlemost(TRUE)

[Package GCDkit version 6.1 Index]