Age and Provenance of Metasedimentary Rocks From the Liwu Group, Western China: Tectonic Implications for the Songpan‐Ganze and Western Yangtze Blocks

ABSTRACT The Liwu Group is located in the core of the Taka, Jianglang and Changqiang domes, and is an important tectono‐stratigraphic unit in the southern Songpan‐Ganze flysch basin. The Songpan‐Ganze Orogenic Belt (SGOB) is bounded by the South China, North China and Qiangtang blocks, and forms the eastern margin of the Tibetan Plateau. The Liwu Group is mainly composed of meta‐clastic/−igneous rocks. We conducted an integrated study of field geology, petrology, geochemistry, and geochronology on representative metasedimentary rocks from the Liwu Group to understand the tectonic evolution of the Songpan‐Ganze Orogenic Belt (SGOB) and the western Yangtze Block. Detrital zircon U–Pb dating on the meta‐clastic rocks yielded age populations of ca. 2472 Ma, 964 Ma, 791 Ma, 535 Ma and 466 Ma, constraining the maximum deposition age at ~466 Ma. Low‐medium chemical index of alteration (CIA = 36–80), relatively high index of compositional variability (ICV = 0.52–1.35), and the positive Zr/Sc vs. Th/Sc correlation indicate low maturity and insignificant weathering. Whole‐rock geochemical data indicate that the sediment provenance was dominated by the late Archean–Paleoproterozoic Liwu Group felsic‐intermediate rocks. The sediments were likely deposited in an active continental margin setting during the early Palaeozoic. Regionally, the metasedimentary rocks in the SGOB were probably deposited in ca. 466–490 Ma, and the SGOB may have had similar early Palaeozoic geotectonic evolution in the western Yangtze Block. According to the detrital zircon U–Pb geochronology of the Liwu Group, we suggest a strong genetic link between the protolith formation and the Yangtze Block, and the features of the stratigraphic sedimentary environment and provenance in the Tethys‐Himalayan Ordovician system.