Gold occurrence of Jiaojia gold mine in Shandong province

The microscopy and scanning electronic microscopy （SEM） were used to study the gold occurrence of Jiaojia gold mine, Shandong province. The results show that the gold-bearing minerals are composed of pyrite, chalcopyrite, gangue, sphalerite and galena. 77.12% of gold minerals are the sulphides and 22.88% are the gangues. The gold occurrence is composed of 60.28% fissure gold, 21.63% inclusion gold and 18.09% crystal fractured gold. The morphology of gold mineral is composed of sphere, triangle, rectangle, strip and erose. The Jiaojia gold mineral owns large grain size range from 3-5 μm to 100 μm. 1.5% of gold grains is more than 0.104 mm, 5.26% is 0.074-0.104 mm, 23.31% is 0.043-0.074 mm, 3.76% is 0.043-0.037 mm and 64.29% is less than 0.037 mm. The occurrence of gold mineral is composed of native gold, electrum, native silver, iron-bearing native silver, goldcuprid and acanthite. Electrum is the most important mineral, accounting for 71.56%. The average quality is 641.26‰ for gold and silver mineral.

The occurrence of gold in hydrothermal sulfide at Southwest Indian Ridge 49.6°E

Massive sulfide precipitates found in the Southwest Indian Ridge （SWIR） 49.6°E hydrothermal field are enriched in gold. Here, the mineralogy and mineral chemistry of these massive sulfides to constrain the process of gold precipitation were studied. Sulfide samples in this field include lower- temperature Zn-rich sulfides and relative higher-temperature Fe-rich sulfides. Zn-rich sulfides are dominated by sphalerite-pyrite-chalcopyrite assemblages, with concentrations of gold ranging from 9.08 to 17.0 μg/g. Fe-rich sulfides consist mainly of pyrite-marcasite-isocubanite assemblages, with gold concentrations from 2.17 to 3.79 μg/g. The significant enrichment in gold within the lower- temperature Zn-rich sulfides and the effective separation of Zn and Fe in hydrothermal precipitates at the surface of this field are here interpreted to reflect the strong temperature dependence of gold transportation and deposition within the sulfides. In Zn-rich samples, large amounts of isolated native gold grains were identified. They were found mainly as inclusions up to 8 μm in diameter, occupying porous cavities in sphalerite or in the elevated iron content rim of sphalerite. The fineness of the gold ranged from 810 to 830. Unlike previously published results on other hydrothermal fields, these data show a low gold fineness values in SWIR 49.6°E. The FeS content of sphalerite associated with gold grains ranged from 3.2 mole % to 18.9 mole %. This was higher than in other fields, indicating that the sulfur activity is relatively low during the gold precipitation process and that sulfur activity may be one of the main factors affecting gold fineness in the SWIR 49.6°E hydrothermal field. Evidence regarding gold fineness and sulfur activity suggests that gold was quite likely transported as AuHS° rather than as a Au（HS）2- complex.

Mineralogy and Mode of Occurrence of Gold, Silver and Bismuth of the Caijiaying Lead-Zine-Silver Deposit, Hebei Province

The deposit under study is a hydrothermal filling-metasomatic vein type lead-zinc-silver deposit, in whichgold and silver can be recovered as by-products. These metals mainly occur as microgranular native gold,electrum, stephanite, acanthite, pyraragyrite, freibergite, and native silver. Gold minerals tend to be associatedwith galenobismutite, native bismuth and unnamed Bi_2Te. They are either enclosed in pyrite, marmatite,iron-bearing sphalerite and galens or fill the microfissures of these minerals. Silver minerals usually occur incleavages or fissures of galena, marmatite and pyrite, but are not associated with gold and bismuth minerals.Gold and silver mineralizations occurred later than lead and zinc, while the silver mineralization was precededby that of gold.

The Occurrence Mechanism of Gold in Pyrite from the Qiucun Gold Deposit in Fujian Province, China

1 Introduction Precipitation and enrichment of gold is an important subject in the study of gold deposits.As the most common sulphide in gold deposits,pyrite is not only a good indicator of the evolution of mineralizing fluids,but also the important gold-bearing mineral.In this paper,

On the Mechanism of Transformation fromPrimary Ores into Oxidized Ores in FinelyDisseminated Gold Deposits

: This paper, taking the finely disseminated gold deposits in southwestern Guizhou and northwestern Guangxi as examples, discusses the difference between the occurrence of primary ores and that of oxidized ores, analyzes the occurrence mechanism in terms of crystallochemistry and geochemistry, and especially studies the chemical model for supergene leaching transformation of clay minerals in the two types of ores. This study proposes a new idea for dressing and smelting technology for primary gold ores.