Abstract:

Study shows that zinc element mainly goes into the melt phase, partly being into silicates of iron-magnesium and iron oxides,
in silicate melt system. When fluid and melt phase are in separation, zinc preferentially partitions into the hypersaline liquid; However,When brine and vapor are in separation, zinc preferentially enters into the hot brine. During the process of ore-forming, zinc mainly enters into the liquid phase and is transported. And zinc-chloride complex （ZnCln2-n, 0≤n≤4） is the most important form at whichzinc is transported in hydrothermal systems. Oxidation, partial acid, chlorine-rich and sulfide-poor, free Zn2 + , ZnSO0
4 complex, and Zn-OH-complex are important too under certain conditions. There are other potential inorganic ligands to form zinc complexes such as HS-, CO2 -3 , NH3, F-, Br-, S2 -X , SO2 -3 , and so on. However, these complexes are insignificant under general geological conditions.Research shows that carboxylate, amino acids, and humic acids are the most important organisms to form zinc-organic complexes,especially the former. They can transport sufficient zinc to form economic deposits below 200℃. The mineralization of magmatichydrothermal deposit of Zn can be roughly divided into three stages. Early stage of magma degassing in deep magma chamber yields the critical magmatic fluids; during the hydrothermal solutions stage magmatic fluids were derived from magma chamber; afterwards, the magmatic fluids were derived from late stage of degassing in deep magma chamber. The fluid of strata-bound Zn deposit mainly derives from basin brine. The thermal convection of the seafloor in an extensional setting and forces associated with tectonic extrusion control Zn mineralization. Zinc precipitation in hydrothermal solutions is influenced by fluid composition, temperature, pressure, pH and Eh and so on. During ore-forming process, some geological processes such as host rock alteration, boiling and fluid mixing, prompt changes of the physical and chemical conditions (T, P, pH, Eh and so on), which indirectly controls zinc precipitation .

Key words: Zinc, hydrothermal solution, partition coefficient, transport, complex, precipitation.