Although carbonates are the primary form of carbon subducted into the mantle, their fate during recycling is debated. Here we report the first coupled high-precision Zn and Mo isotope data for Cenozoic intraplate basalts from western China. The exceptionally high δ⁶⁶Zn values (+0.39 to +0.50‰) of these lavas require involvement of recycled carbonates in the mantle source. Variable ...