Wasser im ozeanischem Mantel am schnell spreizenden ostpazifischen Rücken; Infrarot-Spektroskopie an nominell wasserfreiem Orthopyroxen

存在于地球地幔中的名义上无水矿物（NAM）中的水对地幔动力学有重要影响。斜方辉石是水的重要载体。它可能含有数百重量份。-在最上层地幔中的H2O含量为ppm，在更深的部分甚至更高，因为它的储存能力是压力增强的。以往对地幔斜方辉石中水的研究仅限于陆下地幔橄榄岩包体。最近，在DFG资助的一个项目中，对来自大洋下地幔的第一批样本进行了研究。这些第一批数据显示，从缓慢扩展的大西洋中脊橄榄岩中的水含量对比，从相当于ODP-航段153斜方辉石中的水饱和度的水平到ODP-航段209中始终低一个数量级的含量。这种对比意味着不同的地幔停留时间后熔体耗尽和/或不同的隆升/折返速率。这一初步调查不仅为我们提供了一个更好地了解水在地幔中的内容，但也提出了有关动力学过程的限制扩张中心以下。为了建立一个更一般的模型和检验初步的假设，研究快速扩张的洋脊中的橄榄岩是绝对必要的。建议的项目旨在通过调查赫斯深海ODP第147航次的橄榄岩斜方辉石（水、主要、次要和微量元素含量、平衡条件），填补知识的根本空白。

Water that is present in the Earth's mantle in nominally anhydrous minerals (NAM's) has a significant influence on mantle dynamics. Orthopyroxene is a very important container for water. It may incorporate several hundred wt.-ppm H2O in the uppermost mantle and even higher amounts in deeper parts, because its storage capacity is pressure-enhanced. Any previous studies on water in mantle orthopyroxene were restricted to peridotite xenoliths from the sub-continental mantle. The first samples from the sub-oceanic mantle were recently studied in the course of an own, DFG-financed project. These first data reveal contrasting water contents in peridotite from the slow spreading Mid-Atlantic Ridge, from levels equal to water saturation in orthopyroxene at ODP-Leg 153 to contents that consistently are one order of magnitude lower at ODP-Leg 209. This contrast implies different mantle residence times after melt depletion and/or different uplift/exhumation rates. This preliminary investigation not only provides us with a better knowledge of the water contents in the mantle but also puts constraints concerning dynamic processes below spreading centers. To develop a more general model and to test the preliminary hypotheses, it is absolutely necessary to study peridotite from a fastspreading ridge. The project suggested is aimed at closing a fundamental gap of knowledge by investigating peridotitic orthopyroxene (water, major, minor and trace element contents, equilibrium conditions) from the Hess Deep, ODP-Leg 147.