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A study of teleseismic P-wave tomography was carried out along the Central Orogenic Belt of China (COBC) consisting of the Qinling, Tongbai, Hong'an, Dabie and Sulu orogens that were created by northward subduction of the South China Block beneath the North China Block to subarc depths in the Paleozoic to Mesozoic. The results show the presence of high velocity anomaly underneath the COBC and its adjacent cratonic regions but the absence of high velocity anomaly in the lower lithosphere beneath the COBC. The high velocity anomaly is deep underneath the COBC, possibly representing the relic of the subducted Paleo-Tethyan oceanic slab predating the continental deep subduction of the South China Block. The high velocity anomaly is also deep underneath the southeastern part of the North China Block, possibly being a relic of the subducted Paleo-Pacific slab. However, no relic of the deeply subducted continental slab is seismically detected in the lower lithosphere beneath the Dabie and Sulu orogens, though the occurrence of ultrahigh-pressure metamorphic rocks in the two orogens has clearly demonstrated continental deep subduction to subarc depths in the Triassic. Instead there is only the relatively flat and uniform Moho boundary beneath the COBC region, indicating that the subduction-thickened continental lithosphere along the COBC has lost its root. It is inferred that the orogenic root beneath the COBC region has been foundered into the asthenospheric mantle at the postcollisional stage. The foundering would have taken place in the Early Cretaceous as indicated by the extensive occurrence of magmatic and migmatitic rocks along the COBC. As a consequence, the seismic tomography cannot detect the deeply subducted continental slab remnant from the Triassic period. It is possible that the tomographic visibility of continental subduction in the lower lithosphere is limited to the past 100 Myr. [ABSTRACT FROM AUTHOR]

Late Mesozoic magmatism in eastern China was extensive and closely related to the subduction of the Paleo-Pacific plate, but genetic relationship between magmatism and subduction remains unclear. Cretaceous magmatic rocks distributed along the eastern coast of China can provide an opportunity to evaluate the influence of subduction on the evolution of the magmatism. Here, a combined study of whole-rock major-trace elements and Sr-Nd-Pb-Hf isotopes as well as zircon U-Pb ages was carried out for the Cretaceous granitoids in Liyang volcanic basin, eastern China. Zircon U-Pb dating results indicate that the Liyang granitoids were emplaced in the Early Cretaceous (ca. 130–125 Ma). These samples (SiO 2 = 70.8–75.3 wt%) are mainly composed of high-K calc-alkaline granite and granite porphyry. Their geochemical characteristics are similar to I-type granites, with enrichment in LREEs, Rb, Th and U, and negative Eu (δEu = 0.04–0.51), Ba, Sr, P and Ti anomalies. All samples show negative whole-rock ε Nd (t) (−9.8 to −5.7) and zircon ε Hf (t) (−15.7 to −3.60) values (corresponding crustal Hf model ages of 1.40–2.17 Ga), and high radiogenic Pb isotopic compositions. The integrated interpretation of geochemical data reveal that rollback of the Paleo-Pacific subducted slab resulted in lithospheric extension and thinning, and the upwelling of hot asthenosphere in eastern China, which induced more intensive underplating of the mantle-derived mafic magma. The ascent of heat and mafic magma, intruded in Meso-Neoproterozoic crust, and triggered partial melting of the Meso-Neoproterozoic crust. The Liyang I-type granitoids were the result of the Meso-Neoproterozoic crustal components mixing with a small number of mantle-derived magmas in the extensional tectonic setting, which was response to slab rollback of the Paleo-Pacific plate. • The Liyang I-type granitoids consisting of granite porphyry and granite were formed in Early Cretaceous; • The Liyang granitoids were derived from Meso-Neoproterozoic crustal components mixing with mantle-derived magmas; • The Early Cretaceous (130–125 Ma) magmatism might be response to the Paleo-Pacific slab rollback. [ABSTRACT FROM AUTHOR]

• We develop a combined geodynamic, mineralogical and seismic modeling approach. • Thermal structure of the stagnant slab in the MTZ beneath SE China is constrained. • The morphology of the slab indicates that it underwent little deformation. The structure of Earth's mantle transition zone (MTZ) contains important information about how oceanic plates are recycled into the mantle. However, morphologies of stagnant slab in the MTZ inferred from seismic studies remain controversial. Here, we conduct combined geodynamic, mineral physical and seismologic modeling to infer fine features of the stagnant slab in the MTZ beneath southeastern China. This method applies mineral physics modeling in combination with geodynamically consistent thermal anomalies to predict seismic velocity structures in the MTZ that are used in triplication waveform modeling. The synthetic waveforms are systematically compared with observed data using a grid search optimization. Our best-fit model reveals a stagnant slab lying at the bottom of the MTZ with a peak temperature reduction of 350 ± 80 K and a thickness of 85 ± 20 km, indicating that it underwent little deformation. By joint modeling of the mineral physics and thermal history of the slab, our approach improves estimates of both the thickness and temperature of the stagnant slab and provides a better understanding of the paleo subduction system beneath southeastern China. [ABSTRACT FROM AUTHOR]