Plots of Nb/Ta ratios against Ta contents in rutile from UHP eclogite and enclosed quartz veins (Dabie-Sulu, China). (a) Large rutile grains in eclogite (#27a-1) and its enclosed quartz vein (#27b-1) from the Sulu orogen (data from Xiao et al. 2006). (b) Small rutile grains in eclogites and enclosed kyanite-quartz veins from the Sulu orogen (pair 1, data from Zhang et al. 2008) and the Dabie orogen (pair 2, data from Zheng et al. 2011b). Also shown are Nb/Ta ratios for the primitive mantle (McDonough and Sun 1995) and the continental crust (Rudnick and Gao 2003).