Hydrogen and Oxygen Isotopic Characteristics of the Fluid Inclusions from the Liangkeshu Iron Deposit in Altay Region, Xinjiang

The Liangkeshu iron deposit in Xinjiang is located in the Kelang basin at the southern margin of Altay. The iron deposit occurs in pegmatite dikes at the contact zone of monzonitic granite and schist of the Middle-Upper Devonian Aletai Formation. Fluid inclusions in quartz from the ore body, which are mainly liquid inclusions were studied by micro temperature measurement and are described in this paper. The results indicate that the homogenization temperatures of the fluid inclusions varied from 156℃ to 367℃, mostly distributed from 210℃ to 250℃. The salinity (NaCl_eq) of fluids ranged from 0.18% to 18.72% and the densities ranged from 0.80 g/cm³ to 0.95 g/cm³. Ore fluids in the Liangkeshu iron deposit were characterized by medium temperature, low salinity and low density, and belonged to the H₂O-NaCl system. δD_SMOW values of quartz were from -110‰ to -76‰, δ¹⁸O_SMOW values changed from 5.3‰ to 7.9‰ and δ¹⁸O_H2O values varied from 1.03‰ to 1.07‰, implying that the ore-forming fluid was magmatic water mixed with meteoric water. Fe mineralization in the Liangkeshu deposit occurred in the Middle Devonian period (about 377 Ma), and is closely related to the monzonitic granite. The decrease of temperature and pressure, the fluids mixing and water-rock reaction played important roles in ore-forming processes of the Fe ore bodies.