Mantle Oxidation State and Its Relationship to Tectonic Environment and Fluid Speciation
Mantle Oxidation State and Its Relationship to Tectonic Environment and Fluid Speciation
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DOI：
10.1126/science.248.4953.337
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发表时间：
1990-04
期刊：
影响因子：
56.9
通讯作者：
B. Wood;L. T. Bryndzia;Kathleen E. Johnson
中科院分区：
文献类型：
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作者：
B. Wood;L. T. Bryndzia;Kathleen E. Johnson
地球的地幔沿着沿着洋中脊被脱气，而在俯冲带则发生再水化和可能的再碳酸化。这些过程和地幔中C-H-O流体的形态与地幔橄榄岩的氧化状态有关。来自大陆地区的橄榄岩捕虏体相对于FMQ（铁橄榄石-磁铁矿-石英）缓冲区的氧逸度（fo 2）范围为-1.5到+1.5个对数单位。最低值来自大陆延伸区。高度氧化的捕虏体（fo 2大于FMQ）来自最近或活跃的俯冲区域（例如，日本的Ichinomegata），通常含角闪石，并显示出流体-岩石相互作用的微量元素和同位素证据。洋脊的橄榄岩减少，相对于FMQ，平均fo 2约为-0.9对数单位，几乎与从洋中脊玄武岩（MORB）玻璃获得的值一致。这些数据进一步证明了MORB液体和残余橄榄岩之间的遗传联系，并表明软流圈，虽然减少，有CO2和H2O作为其主要流体种类。俯冲带的氧化物质进入大陆岩石圈产生的捕虏体具有软流圈和俯冲特征。岩石圈中的流体也以CO2和H2O为主，自然C通常不稳定。虽然天然C（金刚石）的发生在深层次的石榴子石捕虏体和金伯利岩不需要还原条件，计算表明，高Fe 3+含量稳定在石榴石结构和fo 2 deareases随着深度的增加。
The earth's mantle is degassed along mid-ocean ridges, while rehydration and possibly recarbonaton occurs at subduction zones. These processes and the speciation of C-H-O fluids in the mantle are related to the oxidation state of mantle peridotite. Peridotite xenoliths from continental localities exhibit an oxygen fugacity (fo2) range from -1.5 to +1.5 log units relative to the FMQ (fayalite-magnetite-quartz) buffer. The lowest values are from zones of continental extension. Highly oxidized xenoliths (fo2 greater than FMQ) come from regions of recent or acive subduction (for example, Ichinomegata, Japan), are commonly amphibole-bearing, and show trace element and isotopic evidence of fluid-rock interaction. Peridotites from ocean ridges are reduced and have an averae fo2 of about -0.9 log units relative to FMQ, virtually coincident with values obtained from mid-ocean ridge basalt (MORB) glasses. These data are further evidence of the genetic link between MORB liquids and residual peridotite and indicate that the asthenosphere, although reducing, has CO2 and H2O as its major fluid species. Incorporation of oxidized material from subduction zones into the continental lithosphere produces xenoliths that have both asthenospheric and subduction signatures. Fluids in the lithosphere are also dominated by CO2 and H2O, and native C is generally unstable. Although the occurrence of native C (diamond) in deep-seated garnetiferous xenoliths and kimberlites does not require reducing conditions, calculations indicate that high Fe3+ contents are stabilized in the garnet structure and that fo2 deareases with increasing depth.