Zircon U-Pb ages and Hf isotopic compostions of Sugensala pluton in the western Junggar: Constraints on the tectonic evolution

This paper is the result of geological survey engineering.

Objective In order to further understand the tectonic evolution of the West Junggar region.

Methods In this paper, the zircon UPb geochronology and Hf isotopes of Sugensala granites were carried out.

Results The dating results show two stages of age. The first phase focused on 440-440 Ma and the second phase is concentrated in the 410-420 Ma. According to the characteristics of the zircon CL images, we consider a capture zircon age of (444.2±2.2) Ma and a crystallization zircon age of (415.6±1.1) Ma. It is implied there was a wide range of magmatic activity at least on late- Silurian in Boshchekul—Chingiz magmatic arc. The ε_Hf(t) values of the zircon range of 8.6-13.2, with a weighted average of 10.8±1.4, indicating that its original rock is derived from mantle materials. The one-stage Hf model ages (T_DM1) are 521-742 Ma and two-stage Hf model ages (T_DM2) are 565-858 Ma. The granite was derived from the younger crustal materials from partial melting of the depleted mantle which raised to crust and stayed for a period of time. It shows that the source rocks of granites were generated from partial melting of new crustal material. The new components of continental crust may mainly come from depleted mantle-derived basaltic magma.

Conclusions We speculate that Junggar basin is composed of young crust which evolved from depleted mantle in the period of late Neoproterozoic to Early Paleozoic. It is helpful to the further understanding the nature and tectonic evolution for Boshchekul-Chingiz magmatic arc.