Abstract

The early Paleozoic orogeny in South China created an important orogenic belt in East Asia, which possibly extends southwest to the Indochina block and northeast to the Korean Peninsula. Although this orogeny is interpreted as one of the examples of intraplate orogenesis in the world, the driver for the orogeny and its deformation details are poorly understood. In this study, we provide detailed structural analysis of the basement of the northeastern Cathaysia block (i.e., Chencai complex) with geochronological constraints. We combine previous studies with ours and obtain the following results. (1) The Chencai complex has experienced multiple metamorphic and deformation events since the early Paleozoic. The earliest deformation was northward thrusting at ca. 460–420 Ma (Dn+1a), which resulted in the thickening of the crust and coeval regional metamorphism (high-grade amphibolite to granulite facies). During the late stages of the orogeny (ca. 420–390 Ma, Dn+1b), the crust was extended and thinned; metamorphism and deformation during this stage erased the information from earlier stage(s). This early deformation (Dn+1) may have resulted from an intraplate orogeny and may have been a response to the Kuungan orogeny or Bhimphedian orogeny to the south, which caused the final assembly of Gondwana. The Jiangshan-Shaoxing fault belt was a sinistral ductile shear zone that formed to accommodate deformation between the Yangtze block and the eastern Cathaysia block. The Cathaysia block moved northward during the early Paleozoic and compressed the eastern Yangtze block. (2) During the Triassic, the Chencai complex experienced folding, forming northeast-southwest–trending close isoclinal folds as part of the regional thrust system along the southeastern margin of the Yangtze block at this time (Dn+2). (3) A group of northeast-southwest–trending thrusts cut the Chencai complex and placed it directly onto the Jiangshan-Shaoxing fault belt during the Late Jurassic (Dn+3). The main structures in the studied outcrops of the Chencai complex formed during the Triassic and Jurassic, not the early Paleozoic. (4) The fourth deformation event of the Chencai complex was a series of northwest-southeast–trending open folds that may have developed during the Cenozoic.

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