Fluid Inclusions and Hydrogen, Oxygen, and Lead Isotopes of the Antuoling Molybdenum Deposit, Northern Taihang Mountains, China

Abstract

The Antuoling Mo deposit is a major porphyry-type deposit in the polymetallic metallogenic belt of the northern Taihang Mountains, China. The processes of mineralization in this deposit can be divided into three stages: an early quartz-pyrite stage, a middle quartz-polymetallic sulfide stage, and a late quartz-carbonate stage. Four types of primary fluid inclusions are found in the deposit: two-phase aqueous inclusions, daughter-mineral-bearing multiphase inclusions, CO 2 -H 2 O inclusions, and pure CO 2 inclusions. From the early to the late ore-forming stages, the homogenization temperatures of the fluid inclusions are 300 to >500°C, 270-425°C, and 195-330°C, respectively, with salinities of up to 50.2 wt%, 5.3-47.3 wt%, and 2.2-10.4 wt% NaCl equivalent, revealing that the ore-forming fluids changed from high temperature and high salinity to lower temperature and lower salinity. Moreover, based on the laser Raman spectra, the compositions of the fluid inclusions evolved from the NaCl-CO 2 -H 2 O to the NaCl-H 2 O system. The δ 18 O H2O and δD values of quartz in the deposit range from +3.9‰ to +7.0‰ and À117.5‰ to À134.2‰, respectively, reflecting the δD of local meteoric water after oxygen isotopic exchange with host rocks. The Pb isotope values of the sulfides ( 208 Pb/ 204 Pb, 207 Pb/ 204 Pb, 206 Pb/ 204 Pb,) indicate that the ore-forming materials originated from a mixed upper mantle-lower crust source.