Fig. 6: Grain geochemical signatures from SW-1.
From: Cryptic geological histories accessed through entombed and matrix geochronometers in dykes
a Hf isotope composition of small metamict discrete zircon grains analysed by split stream laser ablations. Black squares denote ɛHf = apparent 207Pb-corrected age. Uncertainties are shown at the two sigma level. The red Pb loss line depicts the trajectory for radiogenic-Pb loss from a a 1390 Ma neoblastic dyke component and b an Archean xenocrystic component inherited into the dyke. The Hf isotopic compositions indicate the zircon cannot be Archean xenocrysts that have lost Pb, yet retained primary Hf. MORB-DM depicts the average composition of modern MORB extrapolated to ɛHf = 0 at 4500 Ma. The CHUR parameters are provided in the Supplementary Information. Whole rock Nd converted to ɛHf assuming a terrestrial array relationship plots at the blue star symbol. Hf isotopic data were not collected for zircon inclusions in titanite as these inclusions are below the spatial resolution of the method. b Laser ablation signal (ppm) concentrations of Ti, Zr, Th, and U during ablation highlighting the ablation of a zircon inclusion in titanite. Time-resolved integrations are set on consistent periods to subsample the desired mineral component. c Plot of Zr versus F207% in titanite from SW-1. Data points are colour-coded for apparent 207Pb-corrected age. Zircon inclusions show higher Zr content, less discordance, and older apparent ages.
