Table 3.

Results of Lu–Hf garnet dating

SampleFractionWeight (mg)Lu (ppm)Hf (ppm)176Lu/177Hf176Hf/177HfAge (Ma)
VU 600GRT173.7815.021.771.20320.290134 ± 6342 ± 7
VU 600GRT279.1714.181.821.10270.289424 ± 4
VU 600GRT370.0113.341.910.98930.288714 ± 8
VU 600WR99.950.522.910.02520.282550 ± 5
VU 601EGRT174.496.500.118.31950.339753 ± 18363.9 ± 1.9
VU 601EGRT268.806.540.127.50030.333918 ± 17
VU 601EWR99.780.760.320.33500.285185 ± 8
VU 602GRT172.097.031.330.74760.287181 ± 6344.5 ± 1.3
VU 602GRT268.147.631.340.80680.287535 ± 5
VU 602WR99.980.372.680.01970.282470 ± 5

Uncertainties on Hf isotope ratios are 2SE (standard errors) and refer to the last significant digits. 176Lu/177Hf errors are 0.5%. Reproducibility of 176Hf/177Hf for JMC475 Hf standard yielded 0.282159 ± 6 2SD (standard deviation) over the period of analyses (n = 7). Mass bias correction to 179Hf/177Hf = 0.7325. Decay constant λ176Lu = 1.865 × 10–11 a−1 (Scherer et al. 2001). Age calculations conducted using Isoplot v. 4.15 (Ludwig 2008). Age uncertainties are 2σ.