Abstract:

Halongxiuma molybdenum polymetallic deposit is the only medium-sized porphyry deposit in the eastern part of the East Kunlun metallogenic belt. Based on the detailed study of fluid inclusions and H-O-S isotopes, this paper finds out the nature of ore-forming fluids and the source of ore-forming materials, and constructs the metallogenic model of this deposit. Petrography and microthermometry of fluid inclusions show that two types of inclusions, namely gas-liquid two-phase and CO₂ containing three-phase, are developed in Halongxiuma deposit. The ore-forming fluids are characterized by medium to high temperature (concentrated in 280-340 ℃), high salinity (concentrated in 6.00%-18.00%) and medium density (concentrated in 0.64-0.92 g/cm³), and the metallogenic depth is 2.4-4.1 km, suggesting that the deposit was formed in a meso-epithermal environment. The results of H-O isotope show that the ore-forming fluids are derived from the mixing of magmatic and atmospheric water, and the main component is magmatic water; The results of S isotope show that the ore-forming materials mainly come from the deep magma. Combined with the regional tectonic evolution, it is considered that the metallogenic model of Halongxiuma deposit is as follows: Firstly, intense crust-mantle mixing occurred in East Kunlun area during the Late Indosinian, producing a mixed magma rich in ore-forming elements; Then the ore-bearing fluids boiled during the ascent of the mixed magma and cooled down due to the addition of [JP2]atmospheric water, resulting in the changes in the physical and chemical conditions of mineralization, and promoting the precipitation of metallogenic materials.

Key words: ore-forming fluid；H-O-S isotope；metallogenic model；Halongxiuma , molybdenum polymetallic deposit