IsoplotR (version 0.14)

concordia: Concordia diagram

Description

Plots U-Pb data on Wetherill and Tera-Wasserburg concordia diagrams, calculate concordia ages and compositions, evaluates the equivalence of multiple (\(^{206}\)Pb/\(^{238}\)U-\(^{207}\)Pb/\(^{235}\)U or \(^{207}\)Pb/\(^{206}\)Pb-\(^{206}\)Pb/\(^{238}\)U) compositions, computes the weighted mean isotopic composition and the corresponding concordia age using the method of maximum likelihood, computes the MSWD of equivalence and concordance and their respective Chi-squared p-values. Performs linear regression and computes the upper and lower intercept ages (for Wetherill) or the lower intercept age and the \(^{207}\)Pb/\(^{206}\)Pb intercept (for Tera-Wasserburg), taking into account error correlations and decay constant uncertainties.

Usage

concordia(x, limits = NULL, alpha = 0.05, wetherill = TRUE,
  show.numbers = FALSE, ellipse.col = rgb(0, 1, 0, 0.5),
  concordia.col = "darksalmon", exterr = TRUE, show.age = 1, sigdig = 2)

Arguments

x

an object of class UPb

limits

age limits of the concordia line

alpha

confidence cutoff for the error ellipses

wetherill

logical flag (FALSE for Tera-Wasserburg)

show.numbers

logical flag (TRUE to show grain numbers)

ellipse.col

background colour of the error ellipses

concordia.col

colour of the concordia line

exterr

show decay constant uncertainty?

show.age

one of either

1: don't show the age

2: calculate the concordia age

3: fit a discordia line

sigdig

number of significant digits for the concordia/discordia age

References

Ludwig, K.R., 1998. On the treatment of concordant uranium-lead ages. Geochimica et Cosmochimica Acta, 62(4), pp.665-676.

Examples

# NOT RUN {
data(examples) 
concordia(examples$UPb)
# }