|Abstract:The Nanpanjiang basin is the biggest terrigenous clasitic basin developed on the southwest margin of the South China block. The tectonic setting of the Nanpanjiang Basin during its forming, the onset time and the mechanism of the basin''s opening have been long debated. These debates obstruct our understanding on the evolution of the Indochina orogen. Inside the Nanpanjiang basin, excepted the Triassic deposition, some Paleozoic carbonatites also outcropped, which developed into faulted blocks of the basement during the basin stretching. Around the Paleozoic carbonate faulted blocks, somestratoid or veined diabase outcropped. As the initial record of the basin evolution, the diabase is a perfect research target for studying the age and geodynamics of the basin''s opening. In this study, the diabase samples were acquired near to the Badu town, Tianlin county, Guangxi Province, which is in the southeastern part of the Nanpanjiang Basin. The U-Pb dating was conducted with Cameca IMS 1280 on the baddeleyite and zircon concentrated from the diabase samples. The results give the weighted mean 206Pb/238U ages of 269.3±4.2 Ma (n=15，MSWD=0.27) and 265.0±2.9 Ma (n=8，MSWD=0.02), respectively. This result demonstrates that the Badu diabase emplaced during the Wordian, Middle Permian (265.1~268.8 Ma) and indicates that the Nanpanjiang Basin was stretching during this period. Besides this magmatic event dated by this study, a later mafic magmatic event continued widely in the Nanpanjiang basin during the Late Permian to the Early Triassic (258~248 Ma). Sedimentology study suggests that from the Late Permian to the Early Triassic the sedimentary environment of the Nanpanjiang basin changed from calci-clastic platform to turbidite fan. All these facts suggest that the Nanpanjiang Basin experienced extension during the Middle Permian to Early Triassic.