Ridge subduction and episodes of crustal growth in accretionary belts: Evidence from late Paleozoic felsic igneous rocks in the southeastern Central Asian Orogenic Belt, Inner Mongolia, China

Abstract The Central Asian Orogenic Belt (CAOB) is one of the largest accretionary orogens on Earth and preserves evidence that more than 50% this orogen represents juvenile crustal growth over an extended period some 750 million years from ca. 1000 Ma to 250 Ma. However, mechanism controversial, as implied by a variety proposed models ranging contributions mantle-derived basaltic underplating in post-collisional extensional setting subduction-related processes island arc setting. To distinguish among these models, we report petrological, geochemical, whole-rock Sr-Nd isotope zircon U-Pb Hf analyses late Paleozoic felsic igneous rocks northern Inner Mongolia region, southeastern CAOB. New three plutonic extrusive magmatic suites yield Late Carboniferous Early Permian ages 319–279 Xi Ujimqin granodiorites have low-K tholeiitic calc-alkaline, metaluminous weakly peraluminous compositions, are magnesian I-type granitoids. These granitoids also characterized relatively high MgO Sr contents, Mg# values, mid-ocean ridge basalt (MORB)-like Nd-Hf compositions young model 600–298 features indicate parental magmas originated depleted lithospheric mantle had been metasomatized fluids released subducting slab. By contrast, Xilinhot alkali-feldspar granites Dashizhai rhyolites display geochemical signatures ferroan granites. These, together with their moderately 809–277 Ma, suggest they were produced re-melting lower crust via magmas. coexistence association boninite-adakite-high-Mg andesite-Nb-enriched basalt, MORB ocean basalt-type mafic region implies dramatic change composition fluid-related calc-alkaline magmatism melt-related initiated upwelling asthenosphere. We infer subduction may occurred during Permian. Combined previous studies, there two events early within CAOB, which coincide large-volume flare-ups (300 ± 20 450 Ma). Furthermore, our calculations most CAOB was generated short interval (~20–40 m.y.) each long-lived tectonic cycle (>140 m.y. spanning oceanic rifting, subduction, collision) activity. Ridge played significant role rhythmic Phanerozoic. Repeated cycles punctuated, rapid associated systems represent pattern be generalized other Phanerozoic belts Earth.