Formation of the Wulong gold deposit, Liaodong gold Province, NE China: Constraints from zircon U-Pb age, sericite Ar-Ar age, and H-O-S-He isotopes

摘要

The Wulong deposit is the largest quartz vein-type gold deposit in the eastern Liaoning Province of China. The gold ore bodies are hosted by Mesozoic biotite-granites. The mineralization occurs as veins with lenticular shapes. Laser-ablation-ICP-MS zircon U-Pb dating was used to date the biotite-granite, granite porphyry, and fine-grained diorites at the Wulong deposit, yielding ages of 155.4 +/- 0.9 Ma, 154.2 +/- 1.2 Ma, and 1211 +/- 0.9 Ma, respectively. A sericite sample from the gold ore yields a Ar-40-Ar-38 plateau age of 122.8 +/- 0.8 Ma (MSWD = 0.09). The calculated delta O-18(w) values for the quartz range from 4.8% to 8.6% and the 8Dw values of fluid inclusion waters in quartz vary from -98% to -77%. The H-O isotope data indicates that ore-forming fluids could be of a magmatic origin. The delta S-84 values of metallic sulfides range from +1.1% to +2.4%, with an average of +1.8%, suggesting that the sulfur is derived from a magmatic source. The He-3/He-4 ratios of fluid inclusions in pyrite range from 0.36 to 0.65 Ra with an average of 0.50 Ra. The mantle helium involved in the ore-forming fluid ranges from 3.9% to 7.2%, indicating a crustal fluid source. The Wulong gold deposit was formed at ca. 120 Ma and it has a genetic association with contemporaneous fine-grained diorite. The Wulong deposit was formed during lithospheric thinning of the eastern North China Craton during the early Cretaceous.