- 责任者：Huang Ruifang (State Key Laboratory of Isotope Geochemistry ; Guangzhou Institute of Geochemistry ; Chinese Academy of Sciences ; Guangzhou 510640 ; China) ; Sun Weidong
- 刊名：Acta Petrologica Sinica
- 出版年：2013
- 卷期：29(12)
- 关键词：蛇纹石化 ; serpentinization ; 成矿作用 ; metallogenesis
- 页码：p.4336-4348
- 图表：3 illus., 3 tables, 84 refs.
- 分类号：1001
- issnNo：ISSN1000-0569
- isbnNo：CN11-1922/P
Serpentinization is the hydrothermal alteration of ultramafic rocks （e.g., peridotite, komatⅡte） and mafic rocks （e.g., basalt）. Serpentinization occurs at different types of geological settings, e.g., oceanic basins, spreading ocean ridges, and convergent margins. One specialty of serpentinization that gained wide interests is： hydrogen gas is generated, which may help to explain the origin of life during the early history of the Earth; magnetite usually forms; serpentine is rich in H2O, up to 13%. Some water-soluble elements, e.g. lithium, strontium and arsenic, are concentrated in serpentine. Serpentine dehydrates at temperatures above 700℃, releasing water and these water-soluble elements, which is significant for subduction processes. Such fluid metasomatises the mantle wedge, resulting in composition changes of the mantle. Moreover, serpentinization may have some effect for the formation of different deposits, e.g., iron deposit, gold deposit and silver deposit. In this study, four aspects were discussed in order to understand the mechanism of serpentinization： （1） the alteration products. This part includes five sections, hydrothermal fluid composition, hydrogen generated during serpentinization, formation of lizardite, chrysotile and antigorite, brucite formation and magnetite formation. The fluid composition is dependent on temperature and rock type. At high temperature （〉300℃）, e.g., Logachev hydrothermal field at 353℃, the fluid is acidic （pH around 2.8） and is rich in Fe （2500μmol/kg）; At low temperature, e.g., Lost City hydrothermal field at 40~75℃, fluid is alkaline （pH around 8.0） and contains almost no Fe （below detection limit）. Serpentinization of ultramafic rocks generates larger amounts of hydrogen gas than that of basalt. Logachev hydrothermal field is hosted by peridotite, which contains 12.0mmol/kg H2. By contrast, the host rock of TAG hydrothermal field is basalt and the concentration of H2 is only 0.18~0.23mmol/kg. In the following section, we discuss the formation of lizardite, chrysotile and antigorite. Lots of factors affect which type of serpentine forms, e.g., temperature, pressure, the amount of water, and MgO/SiO2 ratio. The following section is about brucite formation. Brucite usually contains some Fe and its Fe content decreases with increasing temperature. The next section is about magnetite formation. The formation of magnetite depends on reaction progress, temperature and activity of SiO2. （2） Kinetic studies of serpentinization. The speed of serpentinization is dependent on temperature, grain size and fluid type, etc. （3） Element migration during serpentinization. Mg, Ca, Fe and Si could be leached into fluid. Al and Cr are also mobile. （4） The potential of mineralization. Some Fe, Au, Ag deposits are associated with serpentinites, which may be the source for these ore elements.