Ague {GCDkit}R Documentation

Concentration ratio diagram (Ague 1994)

Description

Implementation of Concentration ratio diagrams after Ague (1994) used for judging the mobility of elements or oxides in course of various geochemically open-system processes such as alteration or partial melting.

Usage

    Ague(x = NULL,
    whichelems = "SiO2,TiO2,Al2O3,FeOt,MnO,MgO,CaO,Na2O,K2O,P2O5",
    immobile = NULL, bars = NULL, plot = TRUE)

Arguments

x

two sample names for analyses of the protolith and altered rock compositions, respectively.

whichelems

list of elements to be plotted.

immobile

list of (one or more) elements considered as immobile.

bars

optional name of the variable containing 1sigma errors

for plotting error bars.

plot

logical, should be the diagram plotted or just the results calculated?

Details

The Concentration ratio diagram shows concentration ratio of each geochemical species of interest (element or oxide) in the 'altered rock' to that in its presumed 'protolith'. These ratios are plotted on the y-axis, and the elements are arranged in any convenient order along x.

Following an open-system geological process, any of the perfectly immobile constituents i should ideally have exactly the same concentration ratio rinv defined as (Ague 2003):

rinv = c(A,i)/c(0,i)

where c(i) is the concentration of the species i, 0 refers to the 'protolith' and A to the 'altered rock'.

This ratio, however, would only exceptionally equate unity, when the mass of the whole system is conserved. Using the presumably immobile species i as the geochemical reference frame, the change in the rock mass can be defined as Ague (1994):

Delta_Mass = c(0,i)/c(A)-1

Thus rinv > 1 indicates overall rock mass loss due to removal of mobile constituents; this has the effect of increasing the concentrations of the immobile species ("residual enrichment"). Conversely, rinv < 1 shows an overall rock mass gain ("residual dilution").

The mass change of any mobile constituent j can be expressed as (Ague 1994):

Delta = 1/rinv*c(0,i)/c(A)-1

Mobile species j that have c(A,j)/c(0,j) ratios greater than rinv have been added to the system, and those with ratios lower than rinv have been lost.

In the GCDkit's implementation of the Concentration ratio diagrams, firstly the parental and altered rock samples can be chosen interactively from a binary plot MgO-SiO2, if not specified at the function call. Then the user is prompted for the elements/oxides to be plotted.

If not provided as a comma delimited list among the arguments, the presumably immobile elements are to be specified. To facilitate this choice, printed and plotted as barplots are ordered ratios of the elemental concentrations in the 'altered rock' to that in the 'protolith' (c(A,j)/c(0,j))).

Finally the concentration ratio diagram is plotted. If the parameter bars is given, error bars are also shown corresponding to +/- 1 sigma.

ague.png

Value

Returns a matrix 'results' with the following columns:

Altered/Protolith

concentration ratios of the given geochemical species in the 'altered rock' to that in the 'protolith' - primary y axis of the plot

Gain/loss in %

relative gains (positive) or losses (negative) corrected for the rock mass change - secondary y axis of the plot

Plugin

Isocon.r

Author(s)

Vojtech Janousek, vojtech.janousek@geology.cz

References

Ague J J (1994) Mass transfer during Barrovian metamorphism of pelites, south-central Connecticut; I, Evidence for changes in composition and volume. Amer J Sci 294: 989-1057 doi: 10.2475/ajs.294.8.989

Ague J J (2003) Fluid infiltration and transport of major, minor, and trace elements during regional metamorphism of carbonate rocks, Wepawaug Schist, Connecticut, USA. Amer J Sci 303: 753-816 doi: 10.2475/ajs.303.9.753

Grant J A (1986) The isocon diagram - a simple solution to Gresens equation for metasomatic alteration. Econ Geol 81: 1976-1982 doi: 10.2113/gsecongeo.81.8.1976

Grant J A (2005) Isocon analysis: a brief review of the method and applications. Phys Chem Earth (A) 30: 997-1004 doi: 10.1016/j.pce.2004.11.003

Gresens R L (1967) Composition-volume relationships of metasomatism. Chem Geol 2: 47-55 doi: 10.1016/0009-2541(67)90004-6

See Also

Wedge, isocon

Examples

    data<-loadData("sazava.data",sep="\t")
    
    Ague(c("Po-4","Po-1"),
    "SiO2,TiO2,Al2O3,FeOt,MgO,CaO,Rb,Sr,Ba,Zr,La,Nd,Eu,Gd,Yb,Y",
    "TiO2,SiO2,FeOt")      

[Package GCDkit version 4.0 Index]