Fluid evolution of iron oxide-Cu-Au (IOCG) deposits in the basin inversion setting, North Xinjiang: constraints from halogen and noble gas composition of fluid inclusions

Abstract

The northern margin of the Eastern Junggar and the Yamansu Belt of the Eastern Tianshan are two important late Paleozoic iron oxide-copper-gold mineralization potential areas in northern Xinjiang, China, represented by the Laoshankou, Qiaoxiahala and Heijianshan deposits. . The research shows that the iron oxide-copper-gold deposits in the two areas are produced under the closed arc basin transformation system of the basin, and have obvious two-stage mineralization of iron, copper and gold. Halogen elements and noble gas isotopes are used as reliable fluid tracers to explore the fluid evolution and genesis of iron oxide-copper-gold deposits in this specific tectonic setting. The results show that the ore-forming fluids of the Laoshankou, Qiaoxiahara and Heijianshan deposits have obvious mixed fluid end-member characteristics: (1) The magmatic fluid end-member, mainly involved in the magnetite stage of the Heijianshan deposit, I/Cl, Br/ The ratios of Cl and 40 Ar/ 36 Ar are (16.3～18.0)×10 -6 , (1.03～1.06)×10 -3 and 352～437, respectively; (2) The evapotranspiration origin of seawater surface source salt brine is mainly involved in the aging process. In the copper-gold mineralization stage of the Shankou deposit, the ratios of I/Cl, Br/Cl and 40 Ar/ 36 Ar are (77.1～87.7)×10 -6 , (1.53～1.80)×10 -3 and 672～883.. . more Show more