Become an expert in R — Interactive courses, Cheat Sheets, certificates and more!
Get Started for Free

age

Calculate isotopic ages

Description

Calculates U-Pb, Pb-Pb, Th-Pb, Ar-Ar, K-Ca, Re-Os, Sm-Nd, Rb-Sr, Lu-Hf, U-Th-He, Th-U and fission track ages and propagates their analytical uncertainties. Includes options for single grain, isochron and concordia ages.

Usage

age(x, ...)

## Default S3 method:
age(
  x,
  method = "U238-Pb206",
  exterr = TRUE,
  J = c(NA, NA),
  zeta = c(NA, NA),
  rhoD = c(NA, NA),
  d = diseq(),
  ...
)

## S3 method for class 'UPb'
age(
  x,
  type = 1,
  exterr = TRUE,
  i = NA,
  sigdig = NA,
  common.Pb = 0,
  discordance = discfilter(),
  ...
)

## S3 method for class 'PbPb'
age(x, isochron = TRUE, common.Pb = 2, exterr = TRUE, i = NA, sigdig = NA, ...)

## S3 method for class 'ArAr'
age(x, isochron = FALSE, i2i = TRUE, exterr = TRUE, i = NA, sigdig = NA, ...)

## S3 method for class 'KCa'
age(x, isochron = FALSE, i2i = TRUE, exterr = TRUE, i = NA, sigdig = NA, ...)

## S3 method for class 'UThHe'
age(x, isochron = FALSE, central = FALSE, i = NA, sigdig = NA, ...)

## S3 method for class 'fissiontracks'
age(x, central = FALSE, i = NA, sigdig = NA, exterr = TRUE, ...)

## S3 method for class 'ThU'
age(
  x,
  isochron = FALSE,
  i2i = TRUE,
  exterr = TRUE,
  i = NA,
  sigdig = NA,
  detritus = 0,
  ...
)

## S3 method for class 'ThPb'
age(x, isochron = TRUE, i2i = TRUE, exterr = TRUE, i = NA, sigdig = NA, ...)

## S3 method for class 'ReOs'
age(x, isochron = TRUE, i2i = TRUE, exterr = TRUE, i = NA, sigdig = NA, ...)

## S3 method for class 'SmNd'
age(x, isochron = TRUE, i2i = TRUE, exterr = TRUE, i = NA, sigdig = NA, ...)

## S3 method for class 'RbSr'
age(x, isochron = TRUE, i2i = TRUE, exterr = TRUE, i = NA, sigdig = NA, ...)

## S3 method for class 'LuHf'
age(x, isochron = TRUE, i2i = TRUE, exterr = TRUE, i = NA, sigdig = NA, ...)

Arguments

x

can be:

  • a scalar containing an isotopic ratio,

  • a two element vector containing an isotopic ratio and its standard error, or the spontaneous and induced track densities Ns and Ni,

  • a four element vector containing Ar40Ar39, s[Ar40Ar39], J, s[J],

  • a two element vector containing K40Ca40 and s[K40Ca40],

  • a six element vector containing U, s[U], Th, s[Th], He and s[He],

  • an eight element vector containing U, s[U], Th, s[Th], He, s[He], Sm and s[Sm]

  • a two element vector containing Sr87Rb87 and s[Sr87Rb87]

  • a two element vector containing Os187Re187 and s[Os187Re187]

  • a two element vector containing Nd143Sm147 and s[Nd144Sm147]

  • a two element vector containing Hf176Lu176 and s[Hf176Lu176]

  • a five element vector containing Th230U238, s[Th230/U238], U234U238, s[U234U238] and cov[Th230U238,U234U238]

OR

  • an object of class UPb, PbPb, ThPb, ArAr, KCa, ThU, RbSr, SmNd, ReOs, LuHf, UThHe or fissiontracks.

...

additional arguments
method

one of either 'U238-Pb206', 'U235-Pb207', 'Pb207-Pb206', 'Th232-Pb208', 'Ar-Ar', 'K-Ca', 'Th-U', 'Re-Os', 'Sm-Nd', 'Rb-Sr', 'Lu-Hf', 'U-Th-He' or 'fissiontracks'
exterr

propagate the external (decay constant and calibration factor) uncertainties?
J

two-element vector with the J-factor and its standard error.
zeta

two-element vector with the zeta-factor and its standard error.
rhoD

two-element vector with the track density of the dosimeter glass and its standard error.
d

an object of class diseq.
type

scalar flag indicating whether

1: each U-Pb analysis should be considered separately,

2: all the measurements should be combined to calculate a concordia age,

3: a discordia line should be fitted through all the U-Pb analyses using the maximum likelihood algorithm of Ludwig (1998), which assumes that the scatter of the data is solely due to the analytical uncertainties.

4: a discordia line should be fitted ignoring the analytical uncertainties.

5: a discordia line should be fitted using a modified maximum likelihood algorithm that accounts for overdispersion by adding a geological (co)variance term.
i

index of a particular aliquot
sigdig

number of significant digits for the uncertainty estimate (only used if type=1, isochron=FALSE and central=FALSE).
common.Pb

common lead correction:

0: none

1: use the Pb-composition stored in

settings('iratio','Pb207Pb206') (if x has class UPb and x$format<4);

settings('iratio','Pb206Pb204') and settings('iratio','Pb207Pb204') (if x has class PbPb or x has class UPb and 3<x$format<7); or

settings('iratio','Pb208Pb206') and settings('iratio','Pb208Pb207') (if x has class UPb and x$format=7 or 8).

2: use the isochron intercept as the initial Pb-composition

3: use the Stacey-Kramer two-stage model to infer the initial Pb-composition
discordance

discordance calculator. This is an object of class discfilter, or a two element list containing:

option: one of

1 or 't' (absolute age filter);

2 or 'r' (relative age filter);

3 or 'sk' (Stacey-Kramers common Pb filter);

4 or 'a' (perpendicular Aitchison distance);

5 or 'c' (concordia distance);

6 or 'p' (p-value of concordance); or

NA (omit the discordance from the output)

before: logical flag indicating whether the discordance should be calculated before (TRUE) or after (FALSE) the common-Pb correction.
isochron

logical flag indicating whether each analysis should be considered separately (isochron=FALSE) or an isochron age should be calculated from all analyses together (isochron=TRUE).
i2i

‘isochron to intercept’: calculates the initial (aka ‘inherited’, ‘excess’, or ‘common’) ^{40}Ar/^{36}Ar, ^{40}Ca/^{44}Ca, ^{87}Sr/^{86}Sr, ^{143}Nd/^{144}Nd, ^{187}Os/^{188}Os, ^{176}Hf/^{177}Hf or ^{204}Pb/^{208}Pb ratio from an isochron fit. Setting i2i to FALSE uses the default values stored in settings('iratio',...). When applied to data of class ThU, setting i2i to TRUE applies a detrital Th-correction.
central

logical flag indicating whether each analysis should be considered separately (central=FALSE) or a central age should be calculated from all analyses together (central=TRUE).
detritus

detrital ^{230}Th correction (only applicable when x$format = 1 or 2).

0: no correction

1: project the data along an isochron fit

2: correct the data using an assumed initial ^{230}Th/^{232}Th-ratio for the detritus.

3: correct the data using the measured present day ^{230}Th/^{238}U, ^{232}Th/^{238}U and ^{234}U/^{238}U-ratios in the detritus.

Value

  1. if x is a scalar or a vector, returns the age using the geochronometer given by method and its standard error.

  2. if x has class UPb and type=1, returns a table with the following columns: t.75, err[t.75], t.68, err[t.68], t.76, err[t.76], (t.82, err[t.82],) t.conc, err[t.conc], (disc) or err[p.conc],) containing the ^{207}Pb/^{235}U-age and standard error, the ^{206}Pb/^{238}U-age and standard error, the ^{207}Pb/^{206}Pb-age and standard error, (the ^{208}Pb/^{232}Th-age and standard error,) the single grain concordia age and standard error, (and the % discordance or p-value for concordance,) respectively.

  3. if x has class UPb and type=2, 3, 4 or 5, returns the output of the concordia function.

  4. if x has class PbPb, ThPb, ArAr, KCa, RbSr, SmNd, ReOs, LuHf, ThU or UThHe and isochron=FALSE, returns a table of Pb-Pb, Th-Pb, Ar-Ar, K-Ca, Rb-Sr, Sm-Nd, Re-Os, Lu-Hf, Th-U or U-Th-He ages and their standard errors.

  5. if x has class ThU and isochron=FALSE, returns a 5-column table with the Th-U ages, their standard errors, the initial ^{234}U/^{238}U-ratios, their standard errors, and the correlation coefficient between the ages and the initial ratios.

  6. if x has class PbPb, ThPb, ArAr, KCa, RbSr, SmNd, ReOs, LuHf, UThHe or ThU and isochron=TRUE, returns the output of the isochron function.

  7. if x has class fissiontracks and central=FALSE, returns a table of fission track ages and standard errors.

  8. if x has class fissiontracks or UThHe and central=TRUE, returns the output of the central function.

See Also

Examples

data(examples)
tUPb <- age(examples$UPb,type=1)
tconc <- age(examples$UPb,type=2)
tdisc <- age(examples$UPb,type=3)
tArAr <- age(examples$ArAr)
tiso <- age(examples$ArAr,isochron=TRUE,i2i=TRUE)
tcentral <- age(examples$FT1,central=TRUE)
IsoplotR

Statistical Toolbox for Radiometric Geochronology

v3.8
GPL-3
Authors
Pieter Vermeesch [aut, cre]
Initial release
2021-04-05

We don't support your browser anymore

Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.