The Youjiang Basin is usually regarded as an important foreland basin in the southern part of the South China Block that is related to the convergence of the South China and Indochina blocks during the Permian-Triassic. However, the nature of the basin remains controversial due to questions about the subduction polarity and suture boundary between these two blocks. Permian-Triassic felsic volcanics across the Dian-Qiong and Song Ma suture zones could offer new insights into the convergent processes of the South China and Indochina blocks. This study presents detailed petrological, zircon U-Pb dating, and Hf-O isotope and whole-rock geochemical analyses for the Triassic felsic volcanics of the Youjiang Basin (northeast of the Dian-Qiong). The dacites and rhyolites from the Beisi and Baifeng Formations were dated at ca. 240–245 Ma. All of the felsic volcanics are characterized by high SiO2 (69.40–73.15 wt%), FeOt/MgO, 10000*Ga/Al, and TZr, δ18O (9.7–11.8‰) and negative εNd(t) (from −9.6 to −12.3) and zircon εHf(t) (from −6.2 to −14.5) with A-type granitoid geochemical affinities, suggesting the reworking of crustal rocks in an extensional setting. Permian-Triassic felsic igneous rocks display similar geochemical signatures across the Dian-Qiong suture zone, whereas they show distinctive Sr-Nd and zircon Hf-O isotopes across the Song Ma suture zone. The felsic igneous rocks to the northeast of the Song Ma suture zone have much lower εNd(t) and higher δ18O with negative zircon εHf(t) than those to the southwest, which have positive zircon εHf(t). Combined with other geological and geophysical features, it is inferred that the Song Ma suture zone was probably the suture boundary between the South China and Indochina blocks, and the Youjiang Basin was likely a peripheral foreland basin in response to the southwestward convergence of the South China Block toward the Indochina Block.

中文翻译：

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华南与印度支那地块的组合：来自右江盆地三叠纪长英质火山岩的约束

右江盆地通常被认为是华南地块南部重要的前陆盆地，与二叠纪—三叠纪华南地块与中南地块的辐合有关。然而，由于关于这两个块体之间的俯冲极性和缝合边界的问题，盆地的性质仍然存在争议。横跨滇琼和宋马缝合带的二叠纪-三叠纪长英质火山岩可以为华南和印度支那地块的汇聚过程提供新的见解。本研究提供了右江盆地（滇琼东北部）三叠纪长英质火山岩的详细岩石学、锆石 U-Pb 定年、Hf-O 同位素和全岩地球化学分析。北寺组和白峰组的英安岩和流纹岩的年代约为 240–245 马。所有长英质火山岩的特征是高 SiO2 (69.40–73.15 wt%)、FeOt/MgO、10000*Ga/Al 和 TZr、δ18O (9.7–11.8‰) 和负 εNd(t)（从 -9.6 到 - 12.3) 和锆石 εHf(t)（从 -6.2 到 -14.5）具有 A 型花岗岩地球化学亲和性，表明在伸展环境中地壳岩石的再加工。二叠纪-三叠纪长英质火成岩在滇琼缝合带上显示出相似的地球化学特征，而在宋马缝合带上则显示出独特的 Sr-Nd 和锆石 Hf-O 同位素。松马缝合带东北部长英质火成岩的εNd(t)低得多，δ18O高得多，锆石εHf(t)为负值，而西南地区的锆石εHf(t)为正值。结合其他地质和地球物理特征，