Analyze radiometric geochronological data.

Purpose

This App can be used to analyze radiometric geochronological data (Pb-Pb, Ar-Ar, Rb-Sr, Sm-Nd, Lu-Hf, Re-Os, U-Th-He, U-Pb). It includes several tools, including isochron, weighted mean, kernel density estimate, cumulative age distribution, york fit and concordia diagram.

Installation

The app requires R software (recommended version 4.4.1) and package (IsoplotR). 

1. Open the download page for R version 4.4.1
2. Download the file named R-4.4.1-win.exe and install it
3. Once you have successfully installed R, you can then install the App
4. The App will download and install required R packages when you run it the first time.

Note that if you installed the App prior to instalilng R, the App icon will show in the Apps bar.
Simply click on that icon to continue after you have installed R.

Note: If downloading packages fails, a pop-up dialog will ask you to copy 2 lines of commands from Results Log and run them in R to complete downloading packages. 

Related FAQ: FAQ-1214 What can I do when Origin has trouble launching R?

Operation

• Input Data

  1. Choose Isotopic Data type (Pb-Pb, Ar-Ar, Rb-Sr, Sm-Nd, Lu-Hf, Re-Os, U-Th-He).
  2. Choose Input Format from Normal, Inverse(X, s[X], Y, s[Y], &rho[X,Y]) and Three ratios(X, s[X], Y, s[Y], Z, s[Z]). 
  3. Specify input data range.
  4. Select Input Errors type from 1 se (abs), 2 se (abs), 1 se (%) and 2 se(%).

  Notes: X, Y and Z are the isotopic (ratio) measurements. s[X], s[Y], s[Z] are analytical uncertainties (standard errors). &rho[X,Y] is the error correlation. 

• Dialog Options

  Isochron

  • Model
    • Error-weighted least squares regression:This algorithm takes into account the analytical uncertainties and error correlations, under the assumption that the scatter between the data points is solely caused by the analytical uncertainty.
    • Ordinary least squares regression: This algorithm  ignores the analytical uncertainties.
    • Error-weighted least squares with overdispersion term: Instead of attributing any overdispersion to underestimated analytical uncertainties, one can also attribute it to the presence of geological uncertainty, which manifests itself as an added (co)variance term.
  • Inverse isochron: toggles between normal and inverse isochrons.

  Weighted Mean

  • Alpha: The confidence limits of the error bars.
  • Common Pb Correction: 
    • None: No correction.
    • Nominal: Use the stored Pb-composition.
    • Isochron: Remove the common Pb by projecting the data along an inverse isochron. Note: choosing this option introduces a degree of circularity in the weighted age calculation. In this case the weighted mean plot just serves as a way to visualise the residuals of the data around the isochron, and one should be careful not to over-interpret the numerical output.
  • Isochron to Intercept: Calculate the initial ⁴⁰Ar/³⁶Ar, ⁴⁰Ca/⁴⁴Ca, ²⁰⁷Pb/²⁰⁴Pb, ⁸⁷Sr/⁸⁶Sr, ¹⁴³Nd/¹⁴⁴Nd, ¹⁸⁷Os/¹⁸⁸Os, ²³⁰Th/²³²Th, ¹⁷⁶Hf/¹⁷⁷Hf or ²⁰⁴Pb/²⁰⁸Pb ratio from an isochron fit. If this option is uncheck,  use the default values.
  • Reject Outliers: Indicate whether outliers should be detected and rejected using Chauvenet&rsquos Criterion.
  • Random Effects: Compute the weighted mean using a random effects model with two parameters: the mean and the dispersion.

  Kernel Density Estimate

  • Adaptive KDE: If checked, the adaptive KDE modifier of Abramson is used.
  • Common Pb Correction/Isochron to Intercept: Follow the same instructions as Weighted Mean. 

  Cumulative Age Distribution

  • Common Pb Correction/Isochron to Intercept: Follow the same instructions as Weighted Mean. 

  York Fit

  • Alpha: Cutoff value for confidence intervals.

  Concordia

  • Age:
    • Calculate no age: Plot the data without calculating an age.
    • Calculate concordia age: Fit a concordia composition and age.
    • Calcuate discordia (model-1) age: Fit a discordia line through the data using the maximum likelihood algorithm of Ludwig, which assumes that the scatter of the data is solely due to the analytical uncertainties.
    • Calcuate discordia (model-2) age: Fit a discordia line ignoring the analytical uncertainties.
    • Calcuate discordia (model-3) age: Fit a discordia line using a modified maximum likelihood algorithm that includes accounts for any overdispersion by adding a geological (co)variance term.
  • Concordia Type:
    • Wetherill: ²⁰⁶Pb/²³⁸U vs. ²⁰⁷Pb/²³⁵U
    • Tera-Wasserburg: ²⁰⁷Pb/²⁰⁶Pb vs. ²³⁸U/²⁰⁶Pb
    • U-Th-Pb concordia: ²⁰⁸Pb/²³²Th vs. ²⁰⁶Pb/²³⁸U (only available if input format is 7th or 8th type)
  • Alpha:Probability cutoff for the error ellipses and confidence intervals.

Sample OPJU File

This app provides a sample OPJU file.  Right click the App icon in the Apps Gallery window, and choose Show Samples Folder from the short-cut menu. A folder will open. Drag-and-drop the project file Radiometric Geochronology Analysis Sample.opju from the folder onto Origin. The Notes window in the project shows detailed steps.
Note: If you wish to save the OPJU after changing, it is recommended that you save to a different folder location (e.g. User Files Folder).

Reference

https://cran.r-project.org/web/packages/IsoplotR/index.html

v1.2:4/1/2025 Update warning text.
v1.19:8/20/2024 Modify based on package updates
v1.14:6/26/2024 Change package location
v1.13:6/8/2022 Add concordia diagram