Early Mesozoic volcanic rocks in northwestern Laos are rarely reported and important for investigating the Paleotethyan tectonic evolution and regional correlation in SE Asia. In this study, New zircon ages and whole-rock geochemical data are presented for the newly identified volcanic rocks in northwestern Laos. Twelve volcanic rocks yield zircon U–Pb ages of 228–234 Ma. The volcanic rocks in northwestern Laos contain basalt, basaltic andesite, andesite, and rhyolite and can be geochemically subdivided into three groups. Both Group 1 and 2 samples belong to the calc-alkaline mafic-intermediate volcanic rocks. Group 1 has ε_Nd (t) values of −0.52 to +1.20, ε_Hf (t) values of +0.9 to +3.6 and δ¹⁸O values of 6.3–7.0‰. In contrast, Group 2 has lower ε_Nd (t) values of −2.82 to −5.89 and ε_Hf (t) values of −4.0 to +1.4 and higher δ¹⁸O values of 6.6–8.1‰ than Group 1. Group 3 samples are high-K calc-alkaline rhyolites with high ε_Nd (t) (−0.08 to +0.74) and positive ε_Hf (t) (+4.6 to +13.2) values. Geochemical characteristics suggest that the Group 1 and 2 samples were derived from a metasomatized lithospheric mantle modified by sediment-derived components, and Group 3 rhyolites were derived from partial melting of juvenile mafic rocks with a crustal component. Our results, along with the geological observations and reported ages suggest that the Late Triassic volcanic rocks in northwestern Laos were formed in a post-collisional setting, and provide the key studies for the connection between the Lancangjiang and Chiang Khong-Lampang-Tak zones.

老挝西北部早中生代火山岩鲜有报道，对研究东南亚古特提斯构造演化和区域对比具有重要意义。本研究提供了老挝西北部新发现的火山岩的新锆石年龄和全岩地球化学数据。十二个火山岩产生的锆石 U-Pb 年龄为 228-234 Ma。老挝西北部火山岩含有玄武岩、玄武安山岩、安山岩和流纹岩，地球化学上可细分为三组。第 1 组和第 2 组样品均属于钙碱性基性中质火山岩。第 1 组的 ε _Nd (t) 值为 -0.52 至 +1.20，ε _Hf (t) 值为+0.9 至 +3.6，δ ¹⁸ O 值为 6.3–7.0‰。相比之下，第 2 组具有较低的 ε_Nd (t) 值为 -2.82 至 -5.89，ε _Hf (t) 值为 -4.0 至 +1.4，δ ¹⁸ O 值比第 1 组高6.6–8.1 ‰。第 3 组样品是高钾钙碱性流纹岩具有高 ε _Nd (t)（-0.08 至 +0.74）和正 ε _Hf(t) (+4.6 到 +13.2) 值。地球化学特征表明，第 1 组和第 2 组样品来自由沉积物衍生成分改性的交代岩石圈地幔，第 3 组流纹岩来自具有地壳成分的新生基性岩的部分熔融。我们的结果以及地质观测和报告的年龄表明，老挝西北部的晚三叠世火山岩是在碰撞后环境中形成的，为澜沧江与清孔-南邦-德带之间的联系提供了关键研究。