Ongoing Subduction of the Paleo‐Asian Ocean in the Carboniferous: Constraint From Magmatism in the Eastern Central Tianshan, <scp>NW</scp> China

ABSTRACT The Palaeozoic magmatism in the Tianshan Orogen can provide a pivotal time‐stamp on the multiple accretions and final amalgamation process of the southern Central Asian Orogenic Belt. To constrain the controversial Carboniferous subduction–accretion history of the South Tianshan Ocean, we investigated a suite of magmatic rocks in the Kawabulak area at the southern edge of the eastern Central Tianshan. LA‐ICP‐MS zircon dating yields emplacement ages of 318 ± 2 Ma for diorite, 332 ± 2 Ma for bojite, 312 ± 2 Ma for granodiorite and 335 ± 1 Ma for gabbro‐diorite enclave, respectively. The early Carboniferous bojite and gabbro‐diorite enclave show high Mg # , Cr and Ni contents, variable zircon Hf isotopic compositions, probably derived from a metasomatised lithospheric mantle wedge in the spinel stability field. The late Carboniferous granodiorite and diorite have low Mg # , Cr, Ni and positive ε Hf ( t ) character, suggesting production dominant via partial melting of the juvenile basaltic lower crust, with addition of mantle‐derived components to a certain extent in the diorite. All the rocks belong to high‐K calc‐alkaline to shoshonitic series, together with the enrichment of LILE (e.g., Rb, Ba, Sr), depletion in HFSE and the amphiboles record high water content H 2 Omelt and oxygen fugacity ΔNNO character, resembling magmatism in a continental arc setting. Taking into account the prevalence of magmatic records along the southern edge of the Central Tianshan Block in Tianshan Orogen, it suggests a progressive northward subduction of the South Tianshan Ocean beneath the Central Tianshan Block during Ordovician to Carboniferous and the Paleo‐Asian Ocean continued to subduct at the Eastern Tianshan in late Carboniferous.