Au-Sb association and fractionation in micro-disseminated gold deposits, southwestern Guizhou - geochemistry and thermodynamics

The dual geochemical character of paragenesis and fractionation between gol d, arsenic and antimony in micro-disseminated gold deposits in southwestern Guizhou is discussed in terms of spatial distribution of independent depos its. lateral and vertical enrichment, mineralization stage and factor and c orrelation analyses. Thermodynamic calculations of solubility and speciatio n of gold and antimony minerals indicate that gold is transported in hydrot hermal solution as Au(HS)(2) and antimony is mainly as Sb(OH)(3)(0) althoug h HSb2S4- may be of increasing importance in acid environment at low temper atures during the late stage of mineralization. Changes in physicochemical conditions hold the key to the association and fractionation between gold a nd antimony. Gold and antimony response differently to physicochemical vari ations because they are distinct from each other in soluble speciation and mineral solubility, leading to precipitation at different times and localit ies during hydrothermal evolution.