Distributions and properties of grain boundary thin film water in the earth's interior

为了研究地球内部水的分布和性质，人们用红外显微光谱方法测量了各种地壳和地幔物质中的水。1)近场红外光谱结合近场显微光谱发展了一种新的水表征方法。这种方法和红外近场红外(NFIR)显微光谱分析技术可以在亚微米尺度上测量水的化学状态和含量，测量范围可以达到300 nm左右。这种近红外光谱方法在微晶石英集合体(玛瑙)上的作图结果揭示了水沿晶界的约束结构，氢键距离较短。2)水在地壳和地幔物质中的分布。各种壳幔岩石的红外显微光谱显示，地球内部水的分布如下：a)深俯冲变质岩中约200公里深的水分布在单斜辉石Ar…的缺陷中更多的ID石榴石，平均含量为2000ppm，证明水向地幔输送。b)地幔中的水可以储存在地幔矿物的缺陷中，如钙钛矿，高达2000ppm。这相当于现在地幔中可储存海水的5倍。c)岩浆和喷发物质中的水可以用我们研究确定的摩尔吸收系数通过红外显微光谱分析来测量。这项技术还可以研究岩浆的就地脱水行为。d)变质岩中剪切带中的流体由于它们的化学成分(氯化钠和二氧化碳)而具有不同的润湿性质，在变质条件下这种润湿性质的差异预计会更大。e)低级别变质岩中的水主要分布在晶界。3)合成晶界水和合成水溶液为了实验研究晶界水的结构和性质，用红外光谱测量了几种合成薄膜水。薄膜水的OH伸缩吸收峰从3400 cm-1移至3200 cm-1左右，表明靠近冰的氢键距离较短。矿物中的水似乎被限制在大约200 nm的范围内。用衰减全反射(ATR)红外光谱对合成的水溶液进行了表征，发现氯化钠溶液表现出更疏松的性质，氢键更长，而碳酸盐溶液表现出更紧密的性质，氢键更短。2003年9月13日，我们在东京工业大学组织了一次国际研讨会，与来自物理、化学和地球科学的国际专家讨论了这些结果。专题讨论会的成果现已编辑成会议论文集，将于2004年7月至8月出版(Nakashima，S.水的物理化学、材料和地球的动力学--薄膜水的结构和行为--环球学院出版社。东京，约200便士。)较少

In order to study the distributions and properties of water in the earth's interior, infrared microspectroscopic methods have been used to measure water in various crustal and mantle materials1)Near-Field infrared MicrospectroscopyA new water characterization method has been developed by combining a near field microscopy spectroscopy. This and infrared Near-field infrared (NFIR) microspectroscopy can measure chemical states and contents of water down to about I wt% in submicron scale down to about 300nm. Mapping results by this NFIR method on microcrystalline quartz aggregates (agate) revealed constrained structures of water along grain boundaries with shorter hydrogen-bond distances.2)Distribution of water in the crust and mantle materialsinfrared microspectroscopy on various crustal and mantle rocks revealed the following distributions of water in the earth's interior.a)Water in deep subducted metamorphic rock to the depth of about 200 km is distributed in defects in clinopyroxnes ar … More id garnets with average contents of 2000 ppm, evidencing the water transport to the mantle.b)Water in mantle can be stored in defects of mantle minerals such as perovskites upto about 2000 ppm. This is corresponding to 5 times as much water as the present sea water can be stored in the mantle.c)Water in magma and erupted materials can be measured by infared microspectroscpy by using molar absorption coefficients determined by our studies. In-situ dehydration behaviors of magma can be studied also by this technique.d)Fluids in shear zones in metamorphic rocks have contrasted wetting properties due to their chemistries (NaCl vs. C02) and this difference in wetting properties is expected to be much larger at metamorphic conditions.e)Water in low grade metamorphic rocks is found to be distributed mainly ingrain boundaries.3)Synthetic grain boundary water and synthetic aqueous solutionsIn order to study experimentally the structures and properties of water in grain boundaries, several synthetic thin film water have been measured by infrared microspectroscopy. Thin film water showed a OH stretching absorption peak shift from 3400 to around 3200cm-1 indicating shorter hydrogen-bonding distance close to ice. Water sandwitched in minerals appeared to be constrained from about 200nm. This structural modification is dependent on mineral species and crystallographic orientations.Synthetic aqueous solutions were studied by Attenuated Total Reflection (ATR) infrared spectroscopy, and NaCl solutions showed more loose nature with longer H-bond, while carbonate solutions indicated more tight nature with shorter H-bond. These aqueous solutions become "looser"at higher temperatues.We organized an international symposium on September 13, 2003 in Tokyo Institute of Technology to discuss these results with international experts from physics, chemistry and earth sciences. The results of the symposium is now edited as a proceeding book which will be published in July-August 2004 (Nakashima, S.Mercury. L.Fenter, P. and Spiers, C.J.(2004)"Physicochemistry of Water and Dynamics_of Materials and the Earth-Structures and behaviors of the thin film water-"Universal Academy Press. Tokyo,〜200p.) Less