Earth Science Frontiers ›› 2011, Vol. 18 ›› Issue (5): 90-102.

• Article • Previous Articles     Next Articles

The classification of oreforming fluid and the efficiency of ore formation of magmatic hydrothermal solution.

  

  1. 1. State Key Laboratory of Geological Processes and Mineral Resources；School of Earth Sciences and Resources, China University of Geosciences (Beijing), Beijing 100083, China
    2.  The 3rd Geological Party, Zhejiang Bureau of Geology and Mineral Exploration and Development/ The 269th Geological Party of Nuclear Industry of Zhejiang, Jinhua 321017, China
    Zhang Dehui, Jin Xudong, Mao Shide, et al. The classification of oreforming fluid and the efficiency of ore formation of magmatic hydrothermal solution. Earth Science Frontiers， 2011， 18(5): 090102
  • Received:2011-07-26 Revised:2011-08-18 Online:2011-09-18 Published:2011-09-18

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Abstract:

 Oreforming fluids are divided into meteoric, seawater, basinal settings, metamorphic and magmatic fluids, according to the contents of H2O, CO2 and NaCl phase components, as well as the critical pressure and halite meltcurvetemperature in the H2ONaCl system. This kinds of classification has a great value in understanding the variety of flowing fluids along geothermal and geopressure gradient, and fluid mixing and unmixing in the earths crust. Compared with other hydrothermal fluids, the magmatic hydrothermal fluid has a highest metalenrichment efficiency by the following reasons: 1) the magmatic hydrothermal fluid has the energy required to carry out the mineralization from the magma; 2) it has a high concentration of volatile components, which not only greatly affects the hydrothermal pH and oxygen fugacity, but also enhances the extraction efficiency of metals, and the huge released energy causes the expansion of wall rock permeability and produces fluid convection; and 3) the characteristics of high temperature and high salinity also lead to much higher metal extraction and enrichment efficiency of magmatichydrothermal fluids than other fluids. Compared with the magmatic melts, the hydrothermal system has higher mineralization efficiency, which can be attributed to the high partition coefficient of liquidmelts for most oreforming elements. The latest estimates of electronegativity and chemical hardness of the fluid phase and the melt phase indicate that, compared with the melt phase, the fluid phase has a greater electronegativity and chemical hardness. According to the hard and soft acidbase theory and the principle of maximum hardness, as the metals show the higher electronegativity and chemical hardness, the fluids are very attractive and of higher extraction ability for the metals compared to the silicate melt phase, which is consistent with the experimental results showing that the vast majority of the metals favor the hydrothermal fluid than the melt phase.

Key words:  hydrothermal fluid, fluid geochemistry, metallogeny, efficiency of ore formation

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