The influence of H2O-H2 fluids and redox conditions on melting temperatures in the haplogranite system
The influence of H2O-H2 fluids and redox conditions on melting temperatures in the haplogranite system
复制标题
H2O-H2 流体和氧化还原条件对单质花岗岩体系熔化温度的影响
DOI：
10.1007/s004100050258
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发表时间：
1997
影响因子：
3.5
通讯作者：
M. Pichavant
中科院分区：
文献类型：
--
作者：
B. Schmidt;F. Holtz;B. Scaillet;M. Pichavant
摘要在1、2、5和8 kbar蒸汽压下测定了H2O-H2流体存在下单花岗岩系统（Qz-Ab-Or）和子系统中石英-碱性长石组合的固相线温度，以限制氧化还原条件对石英长石组合中相关系的影响。在1和2 kbar总压下，使用用于适度还原条件（fH 2 < 60 bar）的Shaw膜技术控制流体相中的氢逸度（fH 2）。固体氧缓冲组合在双胶囊实验中已被用来获得更多的还原条件在1和2千巴和所有的调查在5和8千巴。系统Qz-Or-H2O-H2和Qz-Ab-H2O-H2仅在中等还原条件（1和5 kbar）下进行了研究，系统Qz-Ab-Or-H2O-H2在低至IW（1至8 kbar）的氧化还原条件下进行了研究。对饱和土的计算结果与前人的研究结果吻合得很好。在给定的压力下，固相线温度在0-75巴的fH 2范围内是恒定的（在± 5°C的实验精度内）。在较高的fH 2下，由氧缓冲剂FeO-Fe 3 O 4（WM）和Fe-FeO（IW）产生，固相线温度随着气相中H2含量的增加而增加。在2kbar和5 kbar压力下测得的固相线曲线与相同石英-碱性长石组合在含H_2 O-CO_2或H_2 O-N_2体系下测得的曲线形状相似。这表明H2具有流体相的惰性稀释剂的行为，并且H2在铝硅酸盐熔体中的溶解度非常低。将结果应用于地质相关条件[HM（赤铁矿-磁铁矿）> fO 2> WM]表明，在1至5 kbar总压之间存在H2O-H2流体的情况下，fH 2的增加会导致石英-碱性长石组合的固相线温度略微升高（高达30 °C）。
Abstract Solidus temperatures of quartz–alkali feldspar assemblages in the haplogranite system (Qz-Ab-Or) and subsystems in the presence of H2O-H2 fluids have been determined at 1, 2, 5 and 8 kbar vapour pressure to constrain the effects of redox conditions on phase relations in quartzofeldspathic assemblages. The hydrogen fugacity (fH2) in the fluid phase has been controlled using the Shaw membrane technique for moderately reducing conditions (fH2 < 60 bars) at 1 and 2 kbar total pressure. Solid oxygen buffer assemblages in double capsule experiments have been used to obtain more reducing conditions at 1 and 2 kbar and for all investigations at 5 and 8 kbar. The systems Qz-Or-H2O-H2 and Qz-Ab-H2O-H2 have only been investigated at moderately reducing conditions (1 and 5 kbar) and the system Qz-Ab-Or-H2O-H2 has been investigated at redox conditions down to IW (1 to 8 kbar). The results obtained for the water saturated solidi are in good agreement with those of previous studies. At a given pressure, the solidus temperature is found to be constant (within the experimental precision of ± 5°C) in the fH2 range of 0–75 bars. At higher fH2, generated by the oxygen buffers FeO-Fe3O4 (WM) and Fe-FeO (IW), the solidus temperatures increase with increasing H2 content in the vapour phase. The solidus curves obtained at 2 and 5 kbar have similar shapes to those determined for the same quartz - alkali feldspar assemblages with H2O-CO2- or H2O-N2-bearing systems. This suggests that H2 has the behaviour of an inert diluent of the fluid phase and that H2 solubility in aluminosilicate melts is very low. The application of the results to geological relevant conditions [HM (hematite-magnetite) > fO2 > WM] shows that increasing fH2 produces a slight increase of the solidus temperatures (up to 30 °C) of quartz–alkali feldspar assemblages in the presence of H2O-H2 fluids between 1 and 5 kbar total pressure.