LA-ICP-MS zircon U-Pb age and geochemistry of the dark dykes in Central Tianshan Block

The NNW-trending dark dykes widely occur in Central Tianshan Mountains. The LA-ICP-MS zircon U-Pb dating of dark dyke yielded a weighted mean 206Pb/238U age of 304.8±1.5Ma, suggesting that they were generated in Late Carboniferous. The dark dykes are characterized by low Mg, Cr and Ni values. These samples are enriched in LILEs (e.g., Rb，Ba，Th) and depleted in HFSEs (e.g., Nb, Ta, Ti). The dark dykes were likely generated by interaction of mantle wedge with fluids derived from dehydration of the subducting slab. The closure of the Junggar Ocean probably terminated after Late Carboniferous.