Recycling of deeply subducted continental crust in the Dabie Mountains, central China

摘要: Post-collisional mafic–ultramafic intrusive rocks from the North Dabie zone show evidence for derivation a mantle source that was overprinted by partial melts derived subducted crust of South China Block. All samples are characterized enrichment large ion lithophile elements (LILE, e.g., Ba, Th) and depletion high field strength (HFSE, Nb, Ti). The Zhujiapu intrusion developed in has moderately enriched 87 Sr/ 86 Sri (0.70605–0.70827), negative eNd(T) values (−2.3 to −18.8), unradiogenic Pb isotopes. Such typical “continental” geochemical features do not result crustal contamination or magma mixing, but reflect properties source. Because trace element Sr–Nd isotopic compositions post-collisional similar those Mesozoic mantle-derived lower granulites xenoliths Block, it is unclear whether due contribution lithospheric Block deeply materials However, given 206 Pb/ 204 Pbi Δ7/4, 208 Δ8/4 (159–180) close granitoids, eclogites, gray gneisses Dabie–Sulu orogen, significantly higher than (Δ8/4b160). This indicates slabs experienced time-integrated Th/U U/Pb as deep lithosphere We therefore propose orogen depleted upper metasomatised recycled crust. Due continent–continent collision between late Triassic, over-thickened resulting eclogitic metamorphism mafic crust, producing gravitational instability. foundered into beneath mountain root removal, less composition unusually evolved continental heterogeneity. © 2006 Elsevier B.V. rights reserved.