Abstract It is intriguing whether and how crust‐mantle interaction would proceed in continental subduction zones. Here, we report zircon U‐Pb ages and Hf isotopes, major and trace elements, and Sr‐Nd‐Mo isotopes for Late Paleozoic mafic igneous rocks from the East Kunlun orogen (EKO). Zircon U–Pb dating of these rocks yields concordant ages of 384–387 Ma, corresponding to post‐collisional magmatism in the EKO. The mafic rocks are characterized by arc‐type trace element distribution patterns and slightly enriched Sr‐Nd isotopes, indicating their derivation from a fertile mantle source with the involvement of crustal material. Their high Th/La ratios (0.28–0.77) are inconsistent with the recycling of typical oceanic crust but can be related to continental crust‐derived melts with residual allanite during crustal anatexis. This is further strengthened by the similarity in Sr‐Nd isotopes and zircon Hf isotopes between these mafic rocks and gneiss that represent ancient continental crustal components in the EKO. Notably, the post‐collisional mafic rocks have variably low δ 98 Mo values of −0.64‰ to −0.07‰. Combined with the enriched Sr‐Nd isotopes and high Th/La features, it is inferred that the light Mo isotopic signatures are inherited from the deeply subducted continental crust. Given that continental crust is generally characterized by high δ 98 Mo values of 0.10–0.40‰, the light Mo isotope compositions of the mafic rocks should be inherited from the previously dehydrated continental crust‐derived melts. Our study highlights that the light Mo isotope features can be used to decipher the recycling of continental crust in collisional orogens.
Yang et al. (Fri,) studied this question.
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