Melting of Peridotites through to Granites: A Simple Thermodynamic Model in the System KNCFMASHTOCr
Melting of Peridotites through to Granites: A Simple Thermodynamic Model in the System KNCFMASHTOCr
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DOI：
10.1093/petrology/egy048
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发表时间：
2018-05-01
影响因子：
3.9
通讯作者：
Powell, Roger
中科院分区：
文献类型：
--
作者：
Holland, Tim J. B.;Green, Eleanor C. R.;Powell, Roger
本文提出了一套新的热力学模型，用于计算从橄榄岩到花岗岩，从0.001到70 kbar，从650 ℃到橄榄岩液相线温度范围内，K_2 O-Na_2 O-CaO-FeO-MgO-Al_2 O_3-SiO_2-H_2 O-TiO_2-Fe_2 O_3-Cr_2 O_3（KNCFMASHTOCr）体系的体相关系。该模型可用于计算大范围地幔和地壳成分部分熔融的相平衡。它们提供了一个很好的适合实验的相关系拓扑结构和熔体组成的模型的组成范围内。与Jennings的初步模型相比，E. S. & Holland，T. J. B.（2015）（NCFMASOCr系统中橄榄岩熔融的简单热力学模型。岩石学杂志56，869-892）橄榄岩-玄武岩熔融关系，包含K2 O和TiO 2允许更好地模拟橄榄岩熔融中的小熔体分数，并在高压下再现含金红石榴辉岩熔融。一个改进的有序无序模型尖晶石现在纳入。高于10千巴的压力，湿部分熔融的关系可能会受到显着影响的硅酸盐在含水流体中的溶解，所以一组模型包括一个含水的低密度silicatebearing流体除了一个高密度H2O-轴承硅酸盐熔体。氧逸度可以很容易地计算为整个范围内的散装组成的调查，和水含量对熔体fO（2）的影响进行了评估。
A new set of thermodynamic models is presented for calculating phase relations in bulk compositions extending from peridotite to granite, from 0.001 to 70 kbar and from 650 degrees C to peridotite liquidus temperatures, in the system K2O-Na2O-CaO-FeO-MgO-Al2O3-SiO2-H2O-TiO2-Fe2O3-Cr2O3 (KNCFMASHTOCr). The models may be used to calculate phase equilibria in partial melting of a large range of mantle and crustal compositions. They provide a good fit to experimental phase relation topologies and melt compositions across the compositional range of the model. Compared with the preliminary model of Jennings, E. S. & Holland, T. J. B. (2015) (A simple thermodynamic model for melting of peridotite in the system NCFMASOCr. Journal of Petrology 56, 869-892) for peridotite-basalt melting relations, the inclusion of K2O and TiO2 allows for better modelling of small melt fractions in peridotite melting, and in reproducing rutile-bearing eclogite melting at high pressures. An improved order-disorder model for spinel is now incorporated. Above 10 kbar pressure, wet partial melting relations may be significantly affected by the dissolution of silicates in aqueous fluid, so the set of models includes an aqueous low-density silicatebearing fluid in addition to a high-density H2O-bearing silicate melt. Oxygen fugacity may be readily calculated for the whole range of bulk compositions investigated, and the effect of water content on melt fO(2) is assessed.