ERRATUM PUBLICATION: 2020, v. 132, no. 5/6, p. 1046, https://doi.org/10.1130/B35214E.1. First published 26 March 2020.
The wrong equation “f = XRC/XRM ≈ (True Age)TC-13/(Measured Age)TC-13” has appeared twice and should be corrected to “f = XRC/XRM ≈ (Measured Age)TC-13/(True Age)TC-13” in the following two locations:
1. p. 1037, Figure 5 caption is correct as:
Figure 5. (A) Pb-Pb isochron plot of the Taochong garnet (TC-13). (B) Procedure for normalization of sample 238U/206Pb using the measured array of TC-13 garnet as the primary reference material. Notes: The x intercepts of these arrays were calculated using Isoplot v. 3.75 (Ludwig, 2012) as XRM and XUM, referring to the measured x intercepts of the TC-13 reference material and unknown, respectively. A line anchored to the initial common Pb projected through the correct age for the TC-13 garnet gives an x intercept of XRC. XUC refers to the corrected x intercept of the unknown. Linear correction factor: f = XRC/XRM ≈ (Measured Age)TC-13/(True Age)TC-13, where XUC = XUM × f. MSWD—mean square of weighted deviates.
2. p. 1041, left column is correct as:
On the Tera-Wasserburg plots, U-Pb isotopic compositions of TC-13 form a mixing array between initial and radiogenic Pb (Fig. 7). The common Pb proportion of TC-13 is only ∼3% on average, up to 6% of total Pb. Following the approach suggested by Chew et al. (2014) and Roberts et al. (2017), U-Pb normalization can be achieved using the Taochong garnet (TC-13) as the reference material. A linear correction factor was calculated with the measured Tera-Wasserburg intercept age and the true age of TC-13 (line correction factor: f = XRC/XRM ≈ [Measured Age]TC-13/[True Age]TC-13; the specific method is shown in detail in Figure 5B and its notes). The same correction factor was then applied to correcting 238U/206Pb ratios of other garnets in the same analytical session to obtain their ages. We tested the robustness of using TC-13 as a reference material by analyzing Qichun and Dongping garnets with independently known ages in four separate sessions…