The study of continental deep-subduction has been one of the forefront and core subjects to advance the plate tectonics theory in the twenty-first century. The Dabie-Sulu orogenic belt in China crops out the largest lithotectonic unit containing ultrahigh-pressure metamorphic rocks in the world. Much of our understanding of the world’s most enigmatic processes in continental deep-subduction zones has been deduced from various records in the Dabie-Sulu rocks. By taking these rocks as the natural laboratory, earth scientists have made seminal contributions to understanding of ultrahigh-pressure metamorphism and continental collision. This paper outlines twelve aspects of outstanding progress, including spatial distribution of the UHP metamorphic rocks, timing of the UHP metamorphism, timescale of the UHP metamorphism, the protolith nature of deeply subducted continental crust, subduction erosion and crustal detachment during continental collision, the possible depths of continental subduction, fluid activity in the continental deep-subduction zone, partial melting during continental collision, element mobility in continental deep-subduction zone, recycling of subducted continental crust, geodynamic mechanism of postcollisional magmatism, and lithospheric architecture of collision orogen. Some intriguing questions and directions are also proposed for future studies.

A perspective view on ultrahigh-pressure metamorphism and continental collision in the Dabie-Sulu orogenic belt

We present a new model to explain one of the biggest tectonic problems of Earth Sciences today, namely, how and why did the Archean sub-continental lithospheric mantle under the Eastern Block of the North China Craton (NCC) delaminate or thin so drastically in the Cretaceous? The eastern NCC is surrounded by several sutures: to the north the south-dipping Solonker (Permo-Triassic formation age) and Mongol-Okhotsk suture (Jurassic formation age), to the south the north-dipping Dabie Shan and Song Ma sutures (Permo-Triassic formation age), and to the east the Pacific oceanic plate (200-100 Ma). Water was carried down under the eastern NCC by the hydrated Pacific plate for at least 100 Ma, and by oceanic plates subducted along the Solonker, Dabie Shan and Song Ma sutures for at least 250 Ma from the early Paleozoic to the Permo-Triassic, and by the Mongol-Okhotsk suture for at least 200 Ma until the Jurassic. Tomographic images show that the Pacific plate has ponded along the top of the mantle transition zone under the eastern NCC for over ca. 2000 km from the Japan trench. An addition of 0.2 weight percent H 2 O lowered the solidus temperature of hydrous mantle peridotite by 150 °C, which led to extensive melting in the hydrous mantle transition zone, and to the rise of hydrous plumes into the overlying crust-mantle. By the time of formation of the Permo- Triassic sutures, the hydration caused by subduction of four oceanic plates had caused major garnetization of the Archean crustal root of the eastern NCC, and post-collisional thrusting in the Jurassic led to major crust/mantle thickening and this triggered collapse of the hydro-weakened garnet-enriched crustal root. During the extensional Cretaceous period, abundant mafic, adakitic and granitic intrusions and extensive gold mineralization were emplaced and metamorphic core complexes and sedimentary and foreland basins formed in and around the eastern NCC. Part of the root was chemically transformed and replaced by upwelling fertile asthenospheric material, which fed the extrusion of extensive alkaliflood basalts in the Cenozoic.

Delamination/thinning of sub-continental lithospheric mantle under eastern china: the role of water and multiple subduction

With acquisition and accumulation of new data of structural geological investigations and high-resolution isotopic dating data, we have greatly improved our understanding of the tectonic events occurring in eastern China during the period from the Late Jurassic to Early Cretaceous and may give a new interpretation of the nature, timing and geodynamic settings of the “Yanshan Movement”. During the Mid-Late Jurassic (165±5 Ma), great readjustment of plate amalgamation kinematics took place in East Asia and the tectonic regime underwent great transformation, thus initiating a new tectonic regime in which the North China Block was the center and different plates converged toward it from the north, east and southwest and forming the “East Asia convergent” tectonic system characterized by intracontinental subduction and orogeny. As a consequence, the crustal lithosphere of the East Asian continent thickened considerably during the Late Jurassic, followed immediately by Early Cretaceous substantial lithospheric thinning and craton destruction featured by drastic lithospheric extension and widespread volcano-magmatic activities, resulting in a major biotic turnover from the Yanliao biota to Jehol Biota. Such a tremendous tectonic event that took place in the continent of China and East Asia is the basic connotation of the “Yanshan Movement”. In the paper, according to the deformation patterns, geodynamic settings and deep processes, the “Yanshan Movement” is redefined as the Late Jurassic East Asian multi-directional plate convergent tectonic regime and its associated extensive intracontinental orogeny and great tectonic change that started at ˜165±5 Ma. The substantial lithospheric attenuation in East China is considered the post-effect of the Yanshanian intracontinental orogeny and deformation.

Jurassic Tectonic Revolution in China and New Interpretation of the “Yanshan Movement”

Triassic southeastward subduction of North China Block to South China Block: Insights from new geological, geophysical and geochemical data

Intracontinental deformation in a frontier of super-convergence: A perspective on the tectonic milieu of the South China Block

A new 140-km-long seismic reflection profile provides a high-resolution crustal-scale image of the southern Dabieshan high-pressure (HP) metamorphic belt and the Yangtze foreland fold-and-thrust belt. The seismic image of the stacked section shows that the southern Dabieshan metamorphic terrane and Yangtze foreland belt are separated by a large north-dipping fault. In the foreland the upper crust is dominated by a series of folds and thrusts formed during the collisional stage in the mid-Triassic; it was reworked by crustal extension resulting in the formation of a late Jurassic and Cretaceous red-bed basin. The southern Dabieshan profile shows stacked crustal slabs developed along the margin of the collisional orogenic belt. The Moho reflectors at 10–11 s (∼30–33 km) are seismically prominent and segmented by a number of south-verging thrusts that were probably developed by foreland-directed thrusting of the deeply subducted continental crust during exhumation. The seismic reflection profile suggests that structures related to the Triassic–Jurassic subduction and exhumation of the Yangtze plate are preserved despite the severe crustal extension superimposed during the late Mesozoic and Cenozoic.

Zhongyan Zhao

Papers

Crustal structure of the southern Dabie ultrahigh‐pressure orogen and Yangtze foreland from deep seismic reflection profiling