Characteristics of gold-bearing minerals and gold occurrence state of a Carlin-type gold ore deposit in Guizhou Province,China
In order to formulate reasonable gold extraction technology for recovering gold efficiently,the characteristics of gold-bearing minerals and gold occurrence state of a Carlin-type gold ore deposited in Guizhou Province,China,were investigated by using methods of optical microscopic identification,chemical analysis,X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),and electron probe X-ray microanalysis(EPMA).The results show that the ore has gold grade of 4.30 g/t,w(S)and w(As)contents of 2.97％and 0.35％,respectively.S and As occurred mainly in-1 valence state,indicating that the ore is a primary gold ore.Granular,framboid,biological shaped,metasomatic,and banded structures are main structures of the gold ore.Main sulfides of the ore include arsenic-bearing pyrite and arsenopyrite,while main gangue minerals of the ore include quartz,carbonate minerals,and sericite.The arsenic-bearing pyrites are mostly associated with quartz and carbonate minerals,and a few of them were included in cryptocrystalline quartz and carbonaceous argillaceous minerals.Some of them are characterized with ring-shaped or curved biological remains.94.88％of gold in the ore occurred in the form of inclusion gold.Arsenic-bearing pyrite is the main gold-bearing mineral,which contains 75.81％of gold in the ore.Au contents in different formed arsenic-bearing pyrites are decreased gradually from fine-granular one,bioclastic one,framboid one to coarse-grained one.In addition,there is no positive correlation between Au and S,Au and As.The gold occurred in forms of substituting ion in pyrite lattice and nano-particle inclusions in arsenic-containing pyrite grains,and it is generally disseminated unevenly and sparsely in the arsenic-containing pyrite.The research results can provide theoretical guidance for the formulation of pretreatment-gold leaching process for treating ores of the Carlin-type gold deposits in Guizhou or other regions.Furthermore,the effective oxidation or destruction of gold-bearing pyrite and quartz inclusions,and the prevention of gold secondary inclusion in the pretreatment process are conducive to improve the gold recovery.
Carlin-type gold depositore structuregold-bearing mineralembedded characteristicsoccurrence state
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