age: Calculate isotopic ages

In IsoplotR: Statistical Toolbox for Radiometric Geochronology

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",
  oerr = 1,
  sigdig = NA,
  exterr = FALSE,
  J = c(NA, NA),
  zeta = c(NA, NA),
  rhoD = c(NA, NA),
  d = diseq(),
  ...
)

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

## S3 method for class 'PbPb'
age(
  x,
  isochron = TRUE,
  common.Pb = 2,
  exterr = FALSE,
  i = NULL,
  oerr = 1,
  sigdig = NA,
  projerr = FALSE,
  ...
)

## S3 method for class 'ArAr'
age(
  x,
  isochron = FALSE,
  i2i = TRUE,
  exterr = FALSE,
  i = NULL,
  oerr = 1,
  sigdig = NA,
  projerr = FALSE,
  ...
)

## S3 method for class 'KCa'
age(
  x,
  isochron = FALSE,
  i2i = TRUE,
  exterr = FALSE,
  i = NULL,
  oerr = 1,
  sigdig = NA,
  projerr = FALSE,
  ...
)

## S3 method for class 'UThHe'
age(x, isochron = FALSE, central = FALSE, i = NULL, oerr = 1, sigdig = NA, ...)

## S3 method for class 'fissiontracks'
age(
  x,
  central = FALSE,
  pooled = FALSE,
  i = NULL,
  oerr = 1,
  sigdig = NA,
  exterr = FALSE,
  ...
)

## S3 method for class 'ThU'
age(
  x,
  isochron = FALSE,
  Th0i = 0,
  exterr = FALSE,
  i = NULL,
  oerr = 1,
  sigdig = NA,
  ...
)

## S3 method for class 'ThPb'
age(
  x,
  isochron = TRUE,
  i2i = TRUE,
  exterr = FALSE,
  i = NULL,
  oerr = 1,
  sigdig = NA,
  projerr = FALSE,
  ...
)

## S3 method for class 'ReOs'
age(
  x,
  isochron = TRUE,
  i2i = TRUE,
  exterr = FALSE,
  i = NULL,
  oerr = 1,
  sigdig = NA,
  projerr = FALSE,
  ...
)

## S3 method for class 'SmNd'
age(
  x,
  isochron = TRUE,
  i2i = TRUE,
  exterr = FALSE,
  i = NULL,
  oerr = 1,
  sigdig = NA,
  projerr = FALSE,
  ...
)

## S3 method for class 'RbSr'
age(
  x,
  isochron = TRUE,
  i2i = TRUE,
  exterr = FALSE,
  i = NULL,
  oerr = 1,
  sigdig = NA,
  projerr = FALSE,
  ...
)

## S3 method for class 'LuHf'
age(
  x,
  isochron = TRUE,
  i2i = TRUE,
  exterr = FALSE,
  i = NULL,
  oerr = 1,
  sigdig = NA,
  projerr = FALSE,
  ...
)

## S3 method for class 'PD'
age(
  x,
  nuclide,
  isochron = TRUE,
  i2i = TRUE,
  exterr = FALSE,
  i = NULL,
  oerr = 1,
  sigdig = NA,
  projerr = FALSE,
  ...
)

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 two element vector containing Ar40Ar39, s[Ar40Ar39], 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'
oerr	indicates whether the analytical uncertainties of the output are reported as: 1: 1\sigma absolute uncertainties. 2: 2\sigma absolute uncertainties. 3: absolute (1-\alpha)% confidence intervals, where \alpha equales the value that is stored in settings('alpha'). 4: 1\sigma relative uncertainties (\%). 5: 2\sigma relative uncertainties (\%). 6: relative (1-\alpha)% confidence intervals, where \alpha equales the value that is stored in settings('alpha'). (only used when isochron and central are FALSE)
sigdig	number of significant digits for the uncertainty estimate (only used if type=1, isochron=FALSE and central=FALSE).
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
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','Pb206Pb208') and settings('iratio','Pb207Pb208') (if x has class UPb and x$format=7 or 8). 2: use the isochron intercept as the initial Pb-composition 3: use the Stacey-Kramer two-stage model to infer the initial Pb-composition
discordance	discordance calculator. This is an object of class discfilter, or a two element list containing: option: one of 1 or 't' (absolute age filter); 2 or 'r' (relative age filter); 3 or 'sk' (Stacey-Kramers common Pb filter); 4 or 'a' (perpendicular Aitchison distance); 5 or 'c' (concordia distance); 6 or 'p' (p-value of concordance); or NA (omit the discordance from the output) before: logical flag indicating whether the discordance should be calculated before (TRUE) or after (FALSE) the common-Pb correction.
isochron	logical flag indicating whether each analysis should be considered separately (isochron=FALSE) or an isochron age should be calculated from all analyses together (isochron=TRUE).
projerr	logical. If TRUE, propagates the uncertainty of the non-radiogenic isotope correction (the 'projection error') into the age uncertainty. Note that the resulting single grain age uncertainties may be strongly correlated with each other, but these error correlations are not reported in the output.
i2i	‘isochron to intercept’: calculates the initial (aka ‘inherited’, ‘excess’, or ‘common’) ^{40}Ar/^{36}Ar, ^{40}Ca/^{44}Ca, ^{87}Sr/^{86}Sr, ^{143}Nd/^{144}Nd, ^{187}Os/^{188}Os, ^{176}Hf/^{177}Hf or ^{204}Pb/^{208}Pb ratio from an isochron fit. Setting i2i to FALSE uses the default values stored in settings('iratio',...).
central	logical flag indicating whether each analysis should be considered separately (central=FALSE) or a central age should be calculated from all analyses together (central=TRUE).
pooled	if TRUE, returns the pooled fission track age. Overrides the value of central.
Th0i	initial ^{230}Th correction. 0: no correction 1: project the data along an isochron fit 2: if x$format is 1 or 2, correct the data using the measured present day ^{230}Th/^{238}U, ^{232}Th/^{238}U and ^{234}U/^{238}U activity ratios in the detritus. If x$format is 3 or 4, correct the data using the measured ^{238}U/^{232}Th activity ratio of the whole rock, as stored in x by the read.data() function. 3: correct the data using an assumed initial ^{230}Th/^{232}Th-ratio for the detritus (only relevant if x$format is 1 or 2).
nuclide	a text string corresponding to a valid entry for settings('lambda',...)

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

concordia, isochron, central

Examples

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

IsoplotR documentation built on Aug. 8, 2025, 7:14 p.m.