Late Paleozoic to Early Mesozoic provenance record of Paleo-Pacific subduction beneath South China

摘要

Northeast trending Yong'an Basin, southeast South China Craton, preserves a Permian-Jurassic, marine to continental, siliciclastic-dominated, retroarc foreland basin succession. Modal and detrital zircon data, along with published paleocurrent data, sedimentary facies, and euhedral to subhedral detrital zircon shapes, indicate derivation from multicomponent, nearby sources with input from both the interior of the craton to the northwest and from an inferred arc accretionary complex to the southeast. The detrital zircon U-Pb age spectra range in age from Archean to early Mesozoic, with major age groups at 2000-1700Ma, 1200-900Ma, 400-340Ma, and 300-240Ma. In addition, Early Jurassic strata include zircon detritus with ages of 200-170Ma. Regional geological relations suggest that Precambrian and Early Paleozoic detritus was derived from the inland Wuyi Mountain region and Yunkai Massif of the South China Craton. Sources for Middle Paleozoic to early Mesozoic detrital zircons include input from beyond the currently exposed China mainland. Paleogeographic reconstruction in East Asia suggests derivation from an active convergent plate margin along the southeastern rim of the craton that incorporated part of Southwest Japan and is related to the subduction of the Paleo-Pacific Ocean. Integration of the geologic and provenance records of the Yong'an Basin with the time equivalent Yongjiang and Shiwandashan basins that lie to the southwest and south, respectively, provides an integrated record of the subduction of the Paleo-Pacific Ocean along the southeast margin of the South China Craton and termination of subduction of the Paleo-Tethys beneath its southwest margin in Permo-Triassic.