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-ICROMINERALOGY OF GOLD-BEARING ORES OF METASOMATIC TYPE DEPOSIT IN KAZAKHSTAN

Gulnara Omarova

Abstract

Samples of ore for micromineralogical research were selected from the core of boreholes. The mineral composition of the ores, their textural and structural features were examined under an optical microscope in reflected and transmitted light, scanning electronic microscope (SEM) and energy dispersive X-ray spectrometer (EDS) with microanalyzer. Mineralization by its composition is sulfide. The nature of mineralization is imbedded. Phenocrysts are presented by separate idiomorphic grains of pyrite, aggregate intergrowths of several of its grains. Phenocrysts are formed by separate pentagondodehaedrs of pyrite, intergrowths of its grains and rare chains of grains up to 30.0 mm in length. Besides, in the ore sample there is linneit, millerit, idait and sulfosalts in unessential quantities. Minerals of silver are found as dyscrasite up to 0.08 mm and as polibazit up to 0.03 mm in size. Native gold in the sample was observed in the secretions of foliose-scaly form. The size of scales is approximately 0.01 mm. Telluride gold is presented by highly reflective double telluride differences of massive structure - krennerite, calaverite and petzite. Gold form independent isolations, aggregates with each other and intergrowths of gold tellurides with tetradymite. There are sulfides among which pyrite sharply predominates, in a smaller amount inclusions of galena and sphalerite. Along the edges of sphalerite selections pyrite-chalcopyrite aggregates are observed. Gold is met in the form of fine secretions intergrown with chalcopyrite and in quartz. Chalcosite and covelline form rare, irregular shaped allocations in thin quartz veins. The size of sulfide allocations is from 0.01 to 0.03 mm.

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