Late Triassic uplift, magmatism and extension of the northern North China block: Mantle signatures in the surface

The Late Triassic saw a period of broad uplift, vigorous magmatism and supracrustal stretching in the northern North China block, but the driving mechanism has been uncertain. Previous investigations have mostly dealt with individual tectonic processes, such as petrogenesis of igneous complexes, extensional deformations, or basin development, and the proposed models were aimed to account for some specific processes. This study makes a holistic treatment of Late Triassic denudation, magmatism, and rift basins in an attempt to unravel the driver for these coeval tectonic processes. Late Triassic uplift is registered by a regional disconformity separating Jurassic from Lower-Middle Triassic or older units, and Upper Triassic oligomict conglomerates are suggestive of early-stage peneplanation. The extensive uplift of the northern North China block was also accompanied by the development of the Great Ordos basin in the southern North China block, which exhibits striking southward variation from alluvial/fluvial through deltaic to lacustrine depositional settings. Vigorous magmatism is typified by mantle-sourced alkaline and mafic complexes distributed in an east-west narrow belt. The development of metamorphic core complex and some isolated rift basins is clearly indicative of crustal extension. Spatial variation from coeval island-arc calc-alkaline to backarc bimodal magmatism in the Amurian superterrane hints at southward subduction of the Mongol-Okhotsk plate. All the geologic records point to the plausibility that these synchronous tectonic processes must have been genetically linked and were likely induced by southward subduction of the Mongol-Okhotsk plate. Here, we argue that the Mongol-Okhotsk plate subduction not only triggered arc and backarc magmatism in the Amurian superterrane, but also led to decompression melting and focused upwelling of the upper mantle ahead of the subducting slab beneath the northern North China block. The Late Triassic intraplate extensive uplift, magmatism, and extension in the northern North China block are accordingly interpreted as the signatures of the focused mantle upwelling. (C) 2020 Elsevier B.V. All rights reserved.