An Investigation of Fluid-Rock Interaction During Subduction Zone Metamorphism

CO2-H2O在30km深处的不混相应该是在物质向俯冲带主动输送过程中等温线下降的直接结果。这种环境下的流体相分离应该对俯冲带的热、力学和变质发育产生许多重要影响，但这种影响记录了高压下流体不混相控制岩石学过程的程度。将特别注意确定蓝片岩与绿片岩、蓝片岩与榴辉岩组合的小尺度互层是否源于流体非均质性的产生和保存，以及这种非均质性是否可能是由流体相分离引起的。所采取的方法将是：(1)使用矿物相平衡来计算相类型内和相边界内相邻层之间的a （H20）和a （co2）比率，(2)直接从多代流体包裹体中确定流体成分，以及(3)模拟岩石在非混相和超临界流体状态下的反应途径。待研究的样品来自格鲁瓦岛、陶恩窗口和锡弗诺斯岛的相干高压地层。研究结果将对高压下流体的组成提供更好的约束，并为俯冲板块的脱挥发提供更好的模型。

CO2-H2O immiscibility to depths of 30 km should be a direct result of the depression of isotherms that occurs during active transport of material down a subduction zone. Fluid phase separation in this environment should have a number of important consequences for the thermal, mechanical, and metamorphic development of subduction zones, yet the effect documenting the extent to which fluid immiscibility controls petrologic processes at high pressure. Particular attention will be paid to determining whether small-scale interlaying of blueschist and greenschist and blueschist and eclogite assemblages results from generation and preservation of fluid heterogeneities and whether such heterogeneities could be caused by fluid phase separation. The approach taken will be (1) to use mineral phase equilibria to calculate a (H20) and a (C02) ratios between adjacent layers both within facies types and across facies boundaries, (2) to determine fluid compositions directly from multiple generations of fluid inclusions, and (3) to model reaction pathways for rocks in both the immiscible and supercritical fluid regimes. Samples to be studied are from coherent high-pressure terranes on the Ile de Groix, in the Tauern Window, and on the island of Sifnos. The results should provide better constraints on the compositions of fluids present at high pressure and result in better models for devolatilization of subducting slabs.