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The Luobei Complex in Northeast (NE) China lies in the northern Heilongjiang Complex and comprises a sequence of low-temperature–high-pressure metamorphic rocks distributed along the N–S-oriented suture zone between the Jiamusi and Songliao blocks. However, the timing of formation and tectonic setting of the Luobei Complex remain poorly constrained. Here, we present petrological, geochronological, and geochemical data for metasedimentary rocks from the Luobei Complex to elucidate its origin and tectonic setting. The Luobei Complex is characterised by the occurrence of serpentinite, blueschist, greenschist, amphibolite, and marble, which form lenses or interlayers in a matrix of two-mica schist, albite schist, quartz schist, and granitic gneiss. Zircon U–Pb dating of four metasedimentary rocks yields consistent Late Triassic maximum depositional ages (ca. 214 Ma). Detrital zircons from the Luobei Complex yield ages ranging from 1889 to 202 Ma, with age peaks at 504, 350, 265, and 214 Ma. The ages prior to 350 Ma exist in both the Jiamusi Block and the Central Asia Orogenic Belt (CAOB), indicating that the syn-deposition of Luobei Complex, meanwhile, the lack of ages younger than 350 Ma suggests that the Jiamusi Block rifted eastward from the CAOB. Geochemical data indicate that the studied metasedimentary rocks were formed in a continental island arc setting. These results, together with the Early Jurassic metamorphism reported by previous studies, constrain the timing of final collision to Late Triassic–Early Jurassic after subduction of the Jiamusi Block beneath the Songliao Block. Combining our new results with previous findings, we propose a new tectonic model: (1) during the latest Carboniferous to Late Triassic, the Jiamusi Block rifted from the CAOB as a result of Mongol–Okhotsk oceanic plate subduction; and (2) during the Late Triassic and Early Jurassic, the Jiamusi Block was reunited with the Songliao Block, and the Heilongjiang Complex formed, as a result of Paleo-Pacific plate subduction. [ABSTRACT FROM AUTHOR]