Fig. 3. Condensation (orange) and evaporation (green) isotopic trends expected in δ⁵¹V-δ⁸⁸Sr space, starting from a nebular gas of chondritic composition and assuming that V and Sr species have identical sticking coefficients (γ_i) and 50% condensation temperatures (T₅₀).

The different trends represent the various potential combinations of V and Sr atomic and molecular species (i.e., V, VO, VO₂ and Sr, SrO, respectively) that may be expected in the PPD (53). The solid black line and its gray envelope represent the CAI correlation line presented in Fig. 1. It is noteworthy that the slope of the δ⁵¹V-δ⁸⁸Sr correlation line may be readily reproduced by considering Sr in atomic form and V as 64% VO and 36% V. The vertical red line emphasizes a shift of ~0.3‰ between the chondritic composition and the CAI correlation line. The purple arrow shows the effect of irradiation processes, which would only tend to lower δ⁵¹V values due to cosmogenic ⁵⁰V production.