age: Calculate isotopic ages

Description Usage Arguments Value See Also Examples

View source: R/age.R

Description

Calculates U-Pb, Pb-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

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age(x, ...)

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

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

## S3 method for class 'PbPb'
age(x, isochron = TRUE, common.Pb = 1, 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, Th02 = c(0, 0),
  Th02U48 = c(0, 0, 1e+06, 0, 0, 0, 0, 0, 0), ...)

## 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 (if method='fissiontracks'),

  • 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 six element vector containing Rb, s[Rb], Sr, s[Sr], Sr87Sr86, and s[Sr87Sr86]

  • a six element vector containing Re, s[Re], Os, s[Os], Os187Os188, and s[Os187Os188]

  • a six element vector containing Sm, s[Sm], Nd, s[Nd], Nd143Nd144, and s[Nd144Nd143]

  • a six element vector containing Lu, s[Lu], Hf, s[Hf], Hf176Hf177, and s[Hf176Hf177]

  • a five element vector containing 0/8, s[0/8], 4/8, s[4/8] and cov[0/8,4/8]

OR

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

...

additional arguments

method

one of either 'U238-Pb206', 'U235-Pb207', 'Pb207-Pb206', '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.

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.

wetherill

logical flag to indicate whether the data should be evaluated in Wetherill (TRUE) or Tera-Wasserburg (FALSE) space. This option is only used when type=2

i

(optional) 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

apply a common lead correction using one of three methods:

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

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

3: use the Pb-composition stored in settings('iratio','Pb206Pb204') and settings('iratio','Pb207Pb204')

show.p

Show the p-value for concordance for each aliquot to the output table. Note: it would be unwise to use the p-value value as a concordance filter. Doing so would 'punish' high precision measurements, which are more likely to fail the Chi-square test than low precision measurements. The latter would therefore be 'rewarded' by such a criterion.

isochron

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

i2i

‘isochron to intercept’: calculates the initial (aka ‘inherited’, ‘excess’, or ‘common’) ^{40}Ar/^{36}Ar, ^{40}Ca/^{44}Ca, ^{207}Pb/^{204}Pb, ^{87}Sr/^{86}Sr, ^{143}Nd/^{144}Nd, ^{187}Os/^{188}Os or ^{176}Hf/^{177}Hf 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.

Th02

2-element vector with the assumed initial ^{230}Th/^{232}Th-ratio of the detritus and its standard error. Only used if isochron==FALSE and detritus==2

Th02U48

9-element vector with the measured composition of the detritus, containing X=0/8, sX, Y=2/8, sY, Z=4/8, sZ, rXY, rXZ, rYZ. Only used if isochron==FALSE and detritus==3

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.conc, err[t.conc], 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 single grain concordia age and standard error, and the 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, ArAr, KCa, RbSr, SmNd, ReOs, LuHf, ThU or UThHe and isochron=FALSE, returns a table of Pb-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, 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

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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)

Example output



IsoplotR documentation built on Dec. 9, 2018, 1:04 a.m.