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| Geochemical Styudy of Gold and Arsenic Mineralization of the Carlin-Type Gold Deposits,Qinling Region,China | |
| 摘 要： | Element geochemistry of gold arsenic and mineralogical features of their sulfides in the Carlin-type gold depostis of the Qinling region are discussed in this paper.The initial contents of ore-forming elements such as glod and arsenic are high the ore-bearing rock series in the Qinling region.Furthermore,both the metals are concentrated mainly in the diagenetic pyrite.Study on the mineralogy of arsenic-bearing sulfide minerals in the ores demonstrated that there is a poistive correlation between gold and arsenic in the sulfide minerals.Available evidence suggests that gold in the As-bearing sulfide minerals in likely to be presented as a charge species(Au ),and it is most possible for it to replace the exxcess arsenic at the site of iron and war probably deposited together with arsenic as solid in the sulfide minerals. Pyrite is composed of(Aux^3 ,Fe1-2^2 )(AsS]x^3-S2]1-x^2-),and arenopyrite of (Aux^3 ,Fe1-x^3 )(AsS]x^3-AsS2]1-x^3-).The occurrence of glod in the As-sulfied minerals from the Carlin-type gold depostis in the Qinling region has been confirmed by electron probe and transmission electron microscopic studies.The results show that gold was probably depostied together with arsenicas coupled solid solutions in sulfide minerals in the early stage of mineralization.Metallogenic chemical reactions concerning gold deposition in the Carlin-type As-rich gold deposits would involve oxidation of glod and concurrent reduction of arsenic.Later,the deposited gold as solid was remobilized and redistributed as exsolutions,as a result of increasing hydrothermal alteration and crystallization,and decreasing resistance to refractoriness of the host minerals.Gold occurs as sub-microscopic grains(ranging from 0.04tp 0.16μm in diameter)of native gold along micro factures in and crystalline grains of the sulfiedes. |
| 关 键 词： | 金矿床 元素地球化学 砷 秦岭地区 |
Geochemical study of gold and arsenic mineralization of the carlin-type gold deposits, Qinling Region, China |
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| Authors: | Fuxin Zhang Jianqin Ma Yanjing Chen |
| Institution: | 1. The Key Lab. of Continental Dynamics, Northwest University, Ministry of Education, 710069, Xi’an, China 2. Department of Geology, Northwest University, 710069, Xi’an, China 3. Institute of Geochemistry, Chinese Academy of Sciences, 550002, Guiyang, China 4. Department of Geology, Peking University, 100871, Beijing, China |
| Abstract: | Element geochemistry of gold and arsenic and mineralogical features of their sulfides in the Carlin-type gold deposits of the Qinling region are discussed in this paper. The initial contents of ore-forming elements such as gold and arsenic are high in the ore-bearing rock series in the Qinling region. Furthermore, both the metals are concentrated mainly in the diagenetic pyrite. Study on the mineralogy of arsenic-bearing sulfide minerals in the ores demonstrated that there is a positive correlation between gold and arsenic in the sulfide minerals. Available evidence suggests that gold in the As-bearing sulfide minerals is likely to be presented as a charge species (Au+), and it is most possible for it to replace the excess arsenic at the site of iron and was probably deposited together with arsenic as solid solution in the sulfide minerals. Pyrite is composed of (Aux3+, Fe1?x2+) (AsS]x3? S2]1?x2?, and arsenopyrite of (Aux3+, Fe1?x3+) (AsS]x3? AsS2]1?x3?). The occurrence of gold in the As-sulfide minerals from the Carlin-type gold deposits in the Qinling region has been confirmed by electron probe and transmission electron microscopic studies. The results show that gold was probably deposited together with arsenic as coupled solid solutions in sulfide minerals in the early stage of mineralization. Metallogenic chemical reactions concerning gold deposition in the Carlin-type As-rich gold deposits would involve oxidation of gold and concurrent reduction of arsenic. Later, the deposited gold as solid solution was remobilized and redistributed as exsolutions, as a result of increasing hydrothermal alteration and crystallization, and decreasing resistance to refractoriness of the host minerals. Gold occurs as sub-microscopic grains (ranging from 0.04 to 0.16 μm in diameter) of native gold along micro factures in and crystalline grains of the sulfides. |
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