Age and geochemical characteristics of the Early Carboniferous volcanic rocks in Dishuiquan area of East Junggar Basin, Xinjiang

The Early Carboniferous volcanic rocks in Dishuiquan area are distributed in southern Kalamaili ophiolite belt on the eastern margin of the Junggar Basin. The volcanic rocks are mainly composed of basalts, basaltic andesites, andesite and andesitic breccia lava, belonging to alkaline series and tholeiite series. The LA-ICP-MS zircon U-Pb ages of the volcanic rocks are (336.6±3.7)Ma~(338.3±5.2)Ma, indicating that they were formed in early Carboniferous. These volcanic rocks are enriched in LILE and REE ((La/Yb)N = 3.3~8.5), depleted in Nb and Ta slightly, with relatively low Isr (0.70354~0.70411) and positive εNd(t) (+4.9~+6.6). They were probably derived from a continental mantle wedge source metasomatized by dehydration fluids produced by a subducted slab. Geochemical features indicate that volcanic rocks were formed in an intraplate environment and produced in the post-collisional extensional period. These volcanic rocks suggest that post-collision magmatic activity had already begun at least in the Early Carboniferous in the eastern margin of the Junggar Basin. The captured ancient zircons in volcanic rocks indicate the presence of the old basement in eastern Junggar Basin.