North-South Differences of Xuefeng Mountain Metallogenic Belt and Fluid Inclusion and Isotope Evidences of Ore-Forming Hydrothermal Solution Source

Abstract

Single gold deposits are mainly found in the southern section of the Xuefeng Mountain metallogenic belt, and gold-antimony-tungsten polymetallic deposits are gradually found northward. Based on the causes of ore-forming differences between the southern and northern sections, this research studied fluid inclusion characteristics and hydrogen and oxygen isotopes of the main gold-bearing mineral quartz in both sections. The test results show that the cationic composition of quartz fluid inclusions in typical gold deposits in the southern section is Na + -Ca 2+ type, and the anionic composition is mainly SO4 2and Cl -, with K + /Na + <1 and F -/Cl -<1. The CO2 and N2 content in the gas phase composition is extremely low, especially with the maximum N2 content of only 0.025μg•g -1 . Hydrogen and oxygen isotope projection falls near the formation and metamorphic water, indicating that the ore-forming fluids do not come from magmatic water. The cationic content of quartz fluid inclusions in typical gold deposits in the northern section is relatively dispersed, including Ca + enriched type and Na + -K + -Ca 2+ type, and the anionic composition is mainly SO4 2-. The CO2 and N2 content indicating deep source in the gas phase composition is much higher than that of gold deposits in the southern section, and pure N2 inclusions are developed. Hydrogen and oxygen isotope projection mainly falls into the formation and metamorphic water and their overlap area. The geological and geochemical characteristics show that the ore-forming hydrothermal solution in the southern section mainly comes from groundwater, and that in the northern section comes from a mixture of magmatic rocks, metamorphic water, and groundwater.