Provenance of Central Canyon in Qiongdongnan Basin as evidenced by detrital zircon U-Pb study of Upper Miocene sandstones

Deep-water canyon systems can provide important sandstone reservoirs for deep-water oil and gas exploration in the South China Sea; however, the sedimentary provenance of the Central Canyon in the Qiongdongnan Basin remains controversial. In this work, detrital zircon grains from three drilling sandstones in the Upper Miocene Huangliu Formation in the western part of the Central Canyon were analysed by LA-ICP-MS for U-Pb ages, in order to constrain their provenance. One hundred and ninety-one zircon grains yield concordant U-Pb ages ranging from 28.6 to 3285 Ma. Most of them show oscillatory or linear zoning in CL-images and high Th/U ratios (> 0.1), suggesting that they are magmatic zircons. Three major age clusters at about 30 Ma (N=6), 220-270 Ma (N=29), and 420-440 Ma (N=13), and five minor age clusters at 70-110 Ma (N=7), 150-170 Ma (N=4), 800-850 Ma (N=11), 1800-2000 Ma (N=16), and 2400-2600 Ma (N=7), can be identified in the age spectrum, which are very similar to those of the Upper Miocene sandstones and modern river sands in the Red River area, but different from those of other nearby regions (e.g., Hainan Island, the Pearl River area, and the Mekong River area) in Southeast Asia. The major age peak at about 30 Ma in our samples is consistent with the timing of tectonothermal events in the Red River Fault Zone. Therefore, we suggest that the provenance of the western part of the Central Canyon, in the Qiongdongnan Basin, was fed dominantly by the Paleo-Red River system during the Late Miocene