Abstract:

The Weibao Pb-Zn deposit is located in the western Qimantage, east Kunlun, Xinjiang Province. The stratiform ore bodies are controlled by the strata, and occur in the banded epidote diopsite skarn in middile-lower Langyashan Formation of Jixianian Period. Major Pb-Zn (Cu) ore belongs to epidote diopsite skarn type. The ore minerals consist of galena, sphalerite and chalcopyrite, and the gangue minerals are composed of diopsite, epidote, calsite, chlorite and garnet. The sphalerite is characterized by higher content of Fe (2.206%-2.679%), lower content of Ga, Ge, Cd and Zn/Cd (143-150), and the content of Ag in galena is lower (0.163%-0.210%), which indicates that the metallic minerals may be formed closely with magmatic fluid. There are two types of fluid inclusions, liquid-rich two-phase and gas-rich two-phase. The average homogenization temperatures of two types of inclusions are 268.2 and 273.1 ℃, respectively. The gas components of CO₂, CH₄, N₂ and H₂ in inclusions indicate the ore-forming fluid may be derived from magmatic fluid. In all, the initial oreforming fluid belongs to immiscibility, characterized by middle-high temperature, high salinity and low density. The values of δ³⁴S vary from 0.49‰ to 2.41‰, which indicates that sulfur in sulfides was mainly from the magma. The sulfides have ²⁰⁶Pb/²⁰⁴Pb values from 18.254 to 18.336,²⁰⁷Pb/²⁰⁴Pb values from 15.556 to 15.664,²⁰⁸Pb/²⁰⁴Pb values from 38.060 to 38.367, which suggests that ore-forming metals come from deep magmatic activity, with little crust mixing. In summary, the Weibao Pb-Zn deposit may be a layered skarn type deposit related to Indosinian magmatic activity.

Key words: fluid inclusion, S isotope, Pb isotope, geochemistry, Weibao Zn-Pb deposit, Qimantage, Xinjiang