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首页> 外文期刊>Contributions to Mineralogy and Petrology >Melting of metasomatized peridotite at 4-6 GPa and up to 1200 degrees C: an experimental approach
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Melting of metasomatized peridotite at 4-6 GPa and up to 1200 degrees C: an experimental approach

机译：交代化橄榄岩在4-6 GPa和高达1200摄氏度的温度下熔融：一种实验方法

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The phase assemblages and compositions in a K-bearing lherzolite + H2O system are determined between 4 and 6 GPa and 850-1200 degrees C, and the melting reactions occurring at subarc depth in subduction zones are constrained. Experiments were performed on a rocking multi-anvil apparatus. The experiments had around 16 wt% water content, and hydrous melt or aqueous fluid was segregated and trapped in a diamond aggregate layer. The compositions of the aqueous fluid and hydrous melt phases were measured using the cryogenic LA-ICP-MS technique. The residual lherzolite consists of olivine, orthopyroxene, clinopyroxene, and garnet, while diamond (C) is assumed to be inert. Hydrous and alkali-rich minerals were absent from the run products due to preferred dissolution of K2O (and Na2O) to the aqueous fluid/hydrous melt phases. The role of phlogopite in melting relations is, thus, controlled by the water content in the system: at the water content of around 16 wt% used here, phlogopite is unstable and thus does not participate in melting reactions. The water-saturated solidus, i.e., the first appearance of hydrous melt in the K-lherzolite composition, is located between 900 and 1000 degrees C at 4 GPa and between 1000 and 1100 degrees C at 5 and 6 GPa. Compositional jumps between hydrous melt and aqueous fluid at the solidus include a significant increase in the total dissolved solids load. All melts/fluids are peralkaline and calcium-rich. The melting reactions at the solidus are peritectic, as olivine, clinopyroxene, garnet, and H2O are consumed to generate hydrous melt plus orthopyroxene. Our fluid/melt compositional data demonstrate that the water-saturated hybrid peridotite solidus lies above 1000 degrees C at depths greater than 150 km and that the second critical endpoint is not reached at 6 GPa for a K2O-Na2O-CaO-FeO-MgO-Al2O3-SiO2-H2O-Cr2O3(-TiO2) peridotite composition.
机译：在4至6 GPa和850-1200摄氏度之间确定了含K的锂铁矿+ H2O系统中的相组成和组成，并且限制了在俯冲带亚弧深度发生的熔融反应。实验是在摇摆的多砧装置上进行的。该实验具有约16wt％的水含量，并且含水熔体或水性流体被分离并被捕集在金刚石聚集体层中。使用低温LA-ICP-MS技术测量含水流体和含水熔融相的组成。残留的锂铁矿由橄榄石，邻苯二茂铁，斜铁基吡啶和石榴石组成，而钻石（C）被认为是惰性的。由于优选的K 2 O（和Na 2 O）溶解在含水流体/含水熔融相中，因此运行产物中没有含水和富含碱的矿物。因此，金云母在熔融关系中的作用由系统中的水含量控制：在此处使用的水含量约为16 wt％时，金云母是不稳定的，因此不参与熔融反应。水饱和固相线，即K-锂沸石组成中含水熔体的首次出现，在4GPa下位于900至1000℃之间，在5GPa和6GPa下位于1000至1100℃之间。固相线上含水熔体和含水流体之间的成分跃迁包括总溶解固体负荷的显着增加。所有的熔体/流体都是高碱性和高钙的。固相线的熔融反应是包晶的，因为消耗了橄榄石，斜茂铁，石榴石和H2O生成含水熔融物和邻苯二茂铁。我们的流体/熔体成分数据表明，水饱和的杂化橄榄岩固相线在大于150 km的深度处处于1000摄氏度以上，并且对于K2O-Na2O-CaO-FeO-MgO-，在6 GPa时未达到第二个关键终点Al2O3-SiO2-H2O-Cr2O3（-TiO2）橄榄岩组成。

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