Fluid Inclusions and H-O-S-Pb Isotope Systematics of the Galonggema CuDeposit in Yushu, Qinghai Province, China
Wang Jian
Sun Fengyue
Yu Lu
Jiang Hefang
Wang Fei
Ning Chuanqi
Abstract：In order to determine the metallogenic physicochemical condition, ore-forming materials, ore-forming fluid and metallogenic mechanism of Galonggema VMS (volcanogenic massive sulfide) deposit in the northern Sanjiang metallogenic belt, China, orebody features, fluid inclusion microthermometry, laser Raman spectroscopy, and S, Pb, H, O isotopes are studied in this paper.It is found that deposit is hosted in the Late Triassic Batang Group dacite-volcanic tuff and consists of two parts, namely, lower ore belt of vein-stockwork mineralization system belonging to hydrothermal fluid supply channel, and upper ore belt of exhalative-chemical deposit system of submarine basin brine pond.Fluid inclusions (FIs) in vein-stockwork mineralization are both aqueous and gas-rich, homogenization temperature from 175.6 to 263.3℃, and salinities of 1.05%-6.29% NaCl equivalent (eqv.) and densities of 0.820-0.935g/cm3.Laser Raman spectroscopic analyses of the gas phase components of FIs show they are dominated by H2O, CO2 and minor amounts of N2.Fluid inclusions in barite in exhalative-chemical deposit system are only aqueous FIs, homogenization temperature from 105.2 to 157.1℃, and salinities of 0.18%-5.55% NaCl eqv.and densities of 0.735-1.173g/cm3 suggesting from lower ore belt to upper ore belt metallogenic temperature drops, salinities does not change, and the density of fluid increases.Hydrogen and oxygen isotopic study (δ18OH2O: 0.25‰-1.75‰,δD:-103.2‰ to-65.3‰) shows that metallogenic fluid is a mixture of seawater and magmatic water.The predecessors research results of sulfur isotope previous research indicates that the sulfur were provided by magma and bacteria reduction seawater sulfate or basement rock.Lead isotopic compositions of galena show 206Pb/204Pb ratios ranging from 18.449 to 18.519, 207Pb/204Pb ratios from 15.677 to 15.777, and 208Pb/204Pb ratios from 38.875 to 39.145, respectively.Lead isotopes has high radioactive lead isotope compositions with μ values of 9.65~9.80.It suggests that the lead mainly was sourced from crustal components and little from magma.The mixing of ore-forming fluid and seawater is the main metallogenic mechanism of Galonggema deposit.
Keywords：Sanjiang metallogenic beltGalonggemaore-forming fluiddepositS isotopePb isotopeHO isotopespetrology
Publication Date：2017-01-01
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：16( 941-956 )