U-Th-Pb dating at FiLTER is performed by Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS). Coupling our Excimer 193 nm laser to the Agilent 8900 ICP-MS allows solid sample introduction at spatial resolutions of 12 to 100 µm. Depending on the sample, it is possible to collect both trace element and U-Th-Pb isotopic ratios from each spot location within an individual grain.
The minerals for which we are able to perform geochronologic analyses are listed in the table below. Precision of around 2% is typical for obtained ages. Approximately 60 individual analyses (plus analysis of standard reference materials) can be performed in a 4 hour run. Please feel free to contact us to discuss your particular analytical requirements. Hourly analytical rates can be found here.
The minerals for which we are able to perform geochronologic analyses are listed in the table below. Precision of around 2% is typical for obtained ages. Approximately 60 individual analyses (plus analysis of standard reference materials) can be performed in a 4 hour run. Please feel free to contact us to discuss your particular analytical requirements. Hourly analytical rates can be found here.
Mineral |
Available standards - Age |
References |
Notes |
Monazite |
Stern - (512 Ma) 44069 - (424 Ma) 554 - (46 Ma) |
Gonclalves et al. 2016 Aleinnikoff et al. 2006 Harrison et al. 1999 |
Spot size typically 12 - 50 µm. Ages typically determined using 208Pb/232Th |
Zircon |
91500 - (1065 Ma) Plešovice - (337 Ma) Fish Canyon - (28.2 Ma) |
Wiedenbeck et al. 1995 Slama et al. 2008 Kuiper et al. 2008 |
Spot size typically 20 - 50 µm. Ages typically determined using 206Pb/238U |
Titanite |
DD81-29 - (2700 Ma) MKED1 - (1519 Ma) Mount Mclure - (523 Ma) Fish Canyon (28.2 Ma) |
Davis and Edwards 1986 Spandler et al. 2016 Schoene and Bowring 2006 Kuiper et al. 2008 |
Spot size typically 20 - 50 µm. Ages typically determined using 206Pb/238U |
Terra-Wasserberg plots showing typical analyses of Titanite standard MKED1 and Zircon standard 91500. Both isotope ratios and trace element data were collected in these examples using a laser spot size of 25 µm. Concordia ages displayed. Data was reduced and downhole fractionation corrected isotope ratios produced using Iolite V4.
Weighted mean 206Pb/238U ages for the same MKED1 and 91500 analyses. Legend:
mean = μ ± x | y (| z)
where:
μ: the weighted mean age.
x: the standard error (σ) of μ.
y: the width of the 100(1-α)% confidence interval for μ. This is also shown as a grey band on the plot. The uncertainties associated with the random uncertainties are shown in dark grey, whereas the systematic uncertainties (i.e. J-factor and decay constant) are shown in light grey.
z: the approximate 100(1-α)% confidence interval for t with overdispersion, calculated as z = y√MSWD (not reported for random effects models).
MSWD = x, p(χ2) = y
where:
x: the Mean Square of the Weighted Deviates (MSWD) for age homogeneity. MSWD values >> 1 indicate that the ages are overdispersed with respect to the stated analytical uncertainties.
y: the Chi-squared p-value for the age homogeneity test. p-values <
This figure was generated using the online version of isoplot R available at: https://www.ucl.ac.uk/~ucfbpve/isoplotr/
See also : Vermeesch, P., 2018, IsoplotR: a free and open toolbox for geochronology. Geoscience Frontiers, v.9, p.1479-1493, doi:10.1016/j.gsf.2018.04.001.
An example dataset for 208Pb/232Th ages in monazite. Isotope ratios and trace element data were collected simultaneously using a 15 µm laser spot. The raw data was initially reduced and downhole fractionation corrcted using Iolite V4. Further processing including propagation of errors, plotting concordia and extracting ages from different sample populations was achieved using a custom R script developed by Dr Kyle Larson.
