Water partitioning between coexisting olivine (ol) and wadsleyite (wads) and the effect of the OH-defect concentrations on the P-T-x coordinates of the ol-wads phase transformation

S地幔内410公里深度的地震不连续被认为是由于橄榄石(Ol)向水滑石(Wads)的转变(如Dziewonski和Anderson，1981)。最近的地震观测表明，不连续面不像实验中观察到的那样尖锐(例如，Zhang和Herzberg，1994)，但显示出从大约4公里的广泛厚度范围(例如，Benz和Vidale，1993)。至35公里(van der Meijde等人(2003)。基于理论研究(Wood，1995；Helffrich和Wood，1996)，van der Meijde等人。(2003)解释了观察到的410公里不连续面的加宽是由于共存的地幔矿物OL和WAD中的水合并造成的。如果这是真的，不连续面的厚度变化表明上地幔中水的分布是不同的和不均匀的。然而，到目前为止，水掺入地幔矿物ol和wad中如何影响矿物之间的相界的实验还没有被毫无疑问地证实(Smyth和Frost，2002；Chen等，2002)。要全面了解地球的水周期及其对地球S结构的影响，还需要更多的实验数据。本项目的目标是在实验上确定(I)地幔条件下共存的橄榄石和水滑石的含水饱和度，以及(Ii)水对淬火多砧实验和激光加热金刚石砧实验中ol-wads相变的P-T-x坐标的影响。在这些研究的基础上，第二个应用期的未来项目将处理(Iii)水对ol-wads相变的机理和动力学的影响。

The seismic discontinuity at 410 km depth within the Earth¿s mantle is believed to be caused by the transformation of olivine (ol) to wadsleyite (wads) (e.g. Dziewonski and Anderson, 1981). Recent seismic observations indicate that the discontinuity is not as sharp as observed in experiments (e.g. Zhang and Herzberg, 1994) but shows a wide range of thicknesses from about 4 km (e.g. Benz and Vidale, 1993).) to 35 km (van der Meijde et al. (2003). Based on theoretical studies (Wood, 1995; Helffrich and Wood, 1996) van der Meijde et al. (2003) interpret the observed broadening of the 410 km discontinuity as being caused by water incorporation in the coexisting mantle minerals ol and wads. If this is true, varying thicknesses of the discontinuity indicate variable and inhomogenous distribution of water in the upper mantle. However, up to now it has not been confirmed unquestioningly by experiments how water incorporation into the mantle minerals ol and wads influence the phase boundaries between the minerals (Smyth and Frost, 2002; Chen et al., 2002). To fully understand the water cylcle of the Earth and its effect on the Earth¿s structure more experimental data are needed. The goals of this project are to experimentally determine (i) the water saturation of coexisting olivine and wadsleyite under mantle conditions, and (ii) the effect of water on the P-T-x coordinates of the ol-wads phase transition in quenched multi-anvil experiments as well as in-situ in laser heated diamond anvil experiments. On the base of these studies a future project in the second application period will deal with (iii) the influence of water on the mechanisms and kinetics of the ol-wads phase transition.