Fig. 5

Titanite U–Pb data for three samples individually (top three rows), and for pooled data from all three samples, distinguished by colour following the same scheme (bottom row). a Wetherill concordia plotting measured ratios. b Tera-Wasserburg concordia plotting ratios calculated from the ²⁰⁷Pb/²³⁵U and ²⁰⁶Pb/²³⁸U, with the data conversion performed by Isoplot 3.7. ^These plots are shown for comparison only as the data conversion performed by Isoplot assumes that Pb is highly radiogenic (Ludwig 2012), which is incorrect for these samples. The data conversion is therefore not strictly correct. c Tera-Wasserburg concordia plotting the measured²⁰⁷Pb/²⁰⁶Pb and ²³⁸U/²⁰⁶Pb ratios. Data on all types of concordia are plotted uncorrected for common Pb. Blue dashed lines are two-dimensional (semi-total Pb/U) isochrons calculated by Isoplot Ex 3.7. Lower intercept ages are given as text. Data are plotted at 2σ, and uncertainties on lower intercept ages are 95% confidence. The ²⁰⁷Pb/²⁰⁶Pb_common calculated from each isochron is given, calculated from the slope of the isochron following Eq. (4) for Wetherill concordia, and from the y-intercept of the isochron for Tera-Wasserburg concordia. Isochron slopes and y-intercepts, and their uncertainties, were determined by Isoplot 3.7. Note that for sample 19–85, with few analyses and a relatively small range in Pb_C/Pb*, an anchored Tera-Wasserburg isochron may be more appropriate, and is given in online Fig. S4