Figure 2
Age of ophiolite basalts (symbols in key) versus ΔεHfi (explanation of notation in top inset). (Lu-Hf decay constant = 1.867 × 10−11 55, CHUR values of 176Lu/177Hf = 0.0336 and 176Hf/177Hf = 0.28278556. Indian–Pacific MORB discriminant line and calculation parameters from Pearce et al.29; ΔεHfi = 1.6 εNdi – εHfi. [Note: Pearce et al. 29, referred to parameter as ΔεHfP/I]. Negative ΔεHfi values indicate sample affinity with Indian Ocean MORB chemistry. Such compositions are evident in the signatures of Tethyan basalts, even in 550 Ma MORB basalts from early Paleo-Tethys (bottom inset; China: Yushigou and Russia: Kurai). See Supplementary Information Part 2 for sample details. Average values for present-day Indian and Pacific MORB calculated from PetDB database and references therein.
