Decoupling of surface and subsurface sutures in the Dabie orogen and a continent-collisional lithospheric-wedging model: Sr-Nd-Pb isotopic evidences of Mesozoic igneous rocks in eastern China

摘要: There are significant differences of Nd and Pb isotopic compositions between Mesozoic mafic igneous rocks from the North China Block (NCB) South (SCB). mantle-derived have very lowɛNd values (−15 to −21), and206Pb/204Pb ratios ( −10 > 18.3. The (−16 −20) (< 17.3) early Cretaceous mafic-ultramafic intrusions developed in north part Dabie orogen (NDZ) suggest that deep lithosphere underneath NDZ belongs NCB but not SCB. Therefore, although surface suture SCB is located on side NDZ, subsurface should be south NDZ. This consistent with previous suggestion Sulu terrane east Tanlu fault was displacement, contradictory northward continental subduction A. continent-collisional lithospheric-wedging model can interpret decoupling sutures Dabie-Sulu orogen. After slab break-off, continuing convergence two blocks must increase compression force acting zone, which might induce splitting Thus, lower crust lithospheric mantle margin wedge into along collision zone. process caused overthrust mid-upper exhumed ultrahigh pressure meta-morphic (UHPM) underthrust litho-sphere It could an important mechanism responsible for second rapid cooling uplifting UHPM delamination as well corresponding magmatism Jurassic southward movement may also provide a tectonic setting depth large-scale magmatic-metallogenesis middle-lower reaches Yangtse River eastern China.