Geochemical Characteristics and Significance of the Whole Rock Sr-Nd and Zircon Hf Isotopic in the Paleozoic Granite-plutons in Kuruktag, Xinjiang

The Baihaizi pluton is typical Paleozoic granitic intrusive rock in Kuruktag area.A deep understanding of the petrogenesis and the source material of the rock is of great significance to the study of the tectonic setting and Paleozoic crustal evolution in this area. This paper studied the whole rock Sr-Nd, zircon Hf isotope and zircon trace elements of the Baihaizi pluton.The isotopic results indicate that the rocks have the intitial medium value of I_Sr (0.710 01~0.712 87), with the negative ε_Nd(t) (-21.01~-18.07) and negative ε_Hf(t) (-26.55~-17.28) values. The corresponding Nd two stage mode age (T_DM2) and Hf mode age (T_DMC) range from 2.60 Ga to 2.84 Ga and from 2.43 Ga to 3.00 Ga, respectively, indicating that it is the product of the recycling of crustal materials from the early Paleoproterozoic to the Neoarchean.The zircon trace element analysis shows that the zircons are magmatic crust zircons, with an average T_Zr=745℃ and T_Ti=692℃.The "cold" magma formed in the active continental margin and it was the product of the southward subduction of the south Tianshan ocean to the lower part of the Tarim Craton in the late stage. Many Paleozoic granitic intrusive rocks have been found in the Kuruktag area, the ε_Nd(t) value and zircon ε_Hf(t) value increase first and then decrease with a reduction of age.Combined with the previous data, it is held that crustal evolution in the Kuruktag area experienced a thin-to-thick process in the subduction of the south Tianshan ocean to the Tarim block during the Ordovician-Early Carboniferous.