Volcanoplutonic complexes in NE Vietnam have recently been interpreted as intraplate products of the Emeishan plume. Alternatively, mafic-ultramafic rocks have been considered as dismembered Paleotethyan ophiolites juxtaposed along a tectonic mélange zone. New U-Pb zircon geochronological and geochemical datasets presented here suggest a complex geological history that records collision between the Indochina-South China blocks. Mafic-ultramafic rocks exposed within a tectonic mélange (Song Hien Tectonic Zone) include sub-alkaline pillow basalts that define two geochemically distinct ophiolitic suites (SH-1: N-MORB-like, SH-2: transitional E-MORB-like). Both suites have geochemical signatures suggestive of crustal contamination, compatible with a volcanic passive margin/rift setting. We suggest SH-1 basalts may correlate with the Devonian-Carboniferous Jinshajiang-Ailaoshan-Song Ma branch of the Paleotethys and form part of the associated Dian-Qiong belt, whereas SH-2 basalts are co-magmatic with Middle-Late Permian mafic-ultramafic intrusive rocks (dolerites, gabbros, peridotites) that developed in a rift basin, most likely on the margin of the down-going South China plate during west-vergent subduction beneath Indochina. During continental orogenesis and thrust stacking, these ophiolitic rocks were juxtaposed with other lithotectonic blocks within the Song Hien Tectonic Zone. Post-collisional relaxation led to the development of a rift basin (Song Hien rift) comprising Late Permian-Triassic volcano-sedimentary strata including < 270-265 Ma terrigenous sandstones, < 252 Ma mudstones, and c. 254-248 Ma felsic effusives. Granites and granodiorites were emplaced across NE Vietnam between c. 252-245 Ma in a syn- to post-collisional setting. The Late Permian-Early Triassic felsic magmatic rocks best correlate with coeval rocks in SW Guangxi and the Central and Western Ailaoshan fold belts (China) and the Truong Son fold belt (Vietnam); together they signal the final to post-collisional stages of Indochina-South China collision. We demonstrate that the analysed magmatic rocks in the Lo-Gam-Song Hien domains of NE Vietnam are not genetically linked to the Emeishan Large Igneous Province in the Yangtze block of South China, as has been previously widely proposed.