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首页> 外文期刊>Contributions to Mineralogy and Petrology >The water-undersaturated and dry Qz-Ab-Or system revisited. Experimental results at very low water activities and geological implications
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The water-undersaturated and dry Qz-Ab-Or system revisited. Experimental results at very low water activities and geological implications

机译：重新研究了水不饱和和干燥的Qz-Ab-Or系统。在极低的水分活度和地质意义下的实验结果

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Liquidus phase relations have been determined in the system Qz-Ab-Or-H2O at H2O-undersaturated conditions (melt water content of 1 wt% H2O) in the pressure range 200–800 MPa. Starting materials were homogeneous synthetic glasses containing 1 wt% H2O. The minimum liquidus temperatures of the ternary system Qz-Ab-Or are 925±15 °C at 200 MPa, 990±10 °C at 500 MPa, and 1,050±10 °C at 800 MPa. The normative Qz content of the minimum is 34±2% at 200 MPa (the exact Ab/Or ratio could not be determined). The composition of the minimum is Qz32Ab35Or33 at 500 MPa, and Qz29Ab37Or34 at 800 MPa (Qz/Ab/Or expressed as normative proportions). At a given pressure, the Qz content of the minimum composition in the system Qz-Ab-Or-H2O remains constant with changing aH2O. The Qz content of the minimum composition increases with decreasing pressure and the normative Ab/Or ratio remains approximately constant (for a water content of the melt of 1 wt%). The determined liquidus temperatures in eutectic or minimum melts with 1 wt% H2O, and the effect of pressure on the liquidus temperature are higher than estimated previously (ca. +0.2 °C/MPa between 200 and 800 MPa instead of less than +0.1 °C/MPa in previous estimations). Thus, at a given pressure, temperature and water content, the melt productivity in quartzofeldspathic rocks (such as metagreywackes) is lower than predicted from previous models. The experimental results show (1) that adiabatic decompression in the quartz-alkali feldspar system containing 0–3 wt% H2O produces more melt than expected, which is of importance for the evolution of ascending dacitic and rhyolitic magmas, and (2) that previously published dry liquidus temperatures are strongly underestimated at high pressure (approximately 75 °C at 500 MPa).
机译：已在压力范围内的H2 O不饱和条件下（熔融水含量为1 wt％H2 O）在Qz-Ab-Or-H2 O系统中确定了液相线相关系200–800 MPa。起始原料是含有1 wt％H2O的均质合成玻璃。三元体系Qz-Ab-Or的最低液相线温度在200 MPa时为925±15°C，在500 MPa时为990±10°C，在800 MPa时为1,050±10°C。在200 MPa下，最小值的标准Qz含量为34±2％（无法确定确切的Ab / Or比）。最小成分为500 MPa时的Qz32 Ab35 Or33 和800 MPa时的Qz29 Ab37 Or34 （Qz / Ab / Or以规范比例表示）。在给定压力下，随着aH2O的变化，系统Qz-Ab-Or-H2 O中最小组成的Qz含量保持恒定。最小组成的Qz含量随着压力的降低而增加，并且标准的Ab / Or比保持近似恒定（对于熔体的水含量为1 wt％）。在H2O为1 wt％的共熔体或最低熔体中确定的液相线温度，压力对液相线温度的影响高于先前估计的值（200至800 MPa之间为+0.2°C / MPa，而不是以前的估算值小于+0.1°C / MPa）。因此，在给定的压力，温度和水含量下，石英长石质岩石（如变质灰泥岩）的熔体生产率低于先前模型的预测。实验结果表明：（1）含0–3 wt％H2 O的石英-碱长石体系中的绝热减压比预期的产生更多的熔体，这对于上升的胶状和流纹岩性岩浆的演化非常重要，并且（2）在高压下（500 MPa时约75°C），强烈低估了以前公布的干液相线温度。

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    《Contributions to Mineralogy and Petrology》 |2001年第3期|347-357|共11页
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    Institut für Mineralogie Universität Hannover Welfengarten 1 30167 Hannover Germany;

    Institut für Mineralogie Universität Hannover Welfengarten 1 30167 Hannover Germany;

    Institut für Mineralogie Universität Hannover Welfengarten 1 30167 Hannover Germany;

    Institut für Mineralogie Universität Hannover Welfengarten 1 30167 Hannover Germany;

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