Tectonic erosion related to continental subduction: An example from the eastern North Qaidam Mountains, NW China

Abstract

AbstractTectonic erosion has been commonly recognized in oceanic subduction zones, but evidence of tectonic erosion related to continental subduction is rarely reported. In this contribution, we suggest a tectonic erosion process along the North Qaidam Mountains of NW China during the Early Palaeozoic continental subduction. To the north of the North Qaidam ultra‐high pressure (UHP) metamorphic belt, the microcontinental Oulongbuluke Block (OB) is characterized by Precambrian metamorphic basement. New and existing zircon U–Pb data show that the OB underwent Early Palaeoproterozoic (2.4–2.3 Ga) magmatism and Late Palaeoproterozoic (c. 1.9 Ga) high‐grade metamorphic and anatectic events. The North Qaidam UHP metamorphic belt has been considered to result from the northward subduction of the Qaidam continental block consisting mainly of Meso‐Neoproterozoic orthogneiss and paragneiss. However, our new data show some gneisses enclosing eclogites in the eastern North Qaidam UHP metamorphic belt (Dulan UHP metamorphic unit) experienced 2.4–2.3 Ga magmatism and 1.9–1.8 Ga metamorphism, similar to those of the OB, prior to Early Palaeozoic UHP metamorphism. These data suggest that tectonic erosion occurred during north‐dipping subduction: the Precambrian basement from the upper plate (OB) was transported in the subduction zone to more than 80 km depth, resulting in UHP metamorphism related to Early Palaeozoic continental subduction prior to their exhumation.