Late Carboniferous volcanism of the Harlik orogenic belt, Xinjiang: Zircon U-Pb geochronological, geochemical and Sr-Nd isotopic evidence

Voluminous Carboniferous volcanic rocks outcrop in the Harlik of Xinjiang. The rock types include basalt, andesite and rhyolite. However, accurate chronological data of these rocks are lacking, and the petrogenesis and tectonic implications are debated. LA-ICP-MS zircon U-Pb dating results indicate volcanic rocks formed at 302Ma (Late Carboniferous). Basalts are tholeiite series. The low Ti/Y (343 similar to 406) and Ce/Y (1.5 similar to 1.7), high epsilon(Nd)(t) (+3.9) and low Sr-87/Sr-86(i) (0.7043) values, indicate basalts originated from a depleted lithospheric mantle. Intermediate-acid volcanic rocks, which are depleted in HFSE (e.g., Nb, Ta and Ti), and enriched in LILE (e.g., LREE, Sr and Ba), show an island arc affinity. High epsilon(Nd)(t) (+3.3 similar to+6.0), low Sr-87/Sr-86(i) (0.7032 similar to 0.7046) values and young model ages (t(DM)=543 similar to 797Ma) suggest that intermediate-acid volcanic rocks originated from a young source which is composed of island arc materials formed in the processes of subduction and coalition of Paleo-Asian Oceanic. The formation of Late Carboniferous volcanic rocks in the Harlik indicates the transformation from oceanic environment to continental environment. In the post-orogenic setting, asthenosphere upwelling and lithosphere readjustment induced the re-melting of upper mantle and young crust, which resulted in the formation of Late Carboniferous volcanic rocks in the Harlik area.