Hydrous Spinelloids and the Hydration State of the Mantle

氢可能是地球上最不受约束的成分变量，但它对许多地质过程（如果不是大多数的话）有控制作用。这是一个建议，以提高内部的水合状态的稳定性，晶体化学和状态方程的水合橄榄石，尖晶石，尖晶石相，将发生在和附近的水合过渡带的调查的理解。 我们将与巴伐利亚地质研究所（Bayerisches Geoinstitut）的同事合作，在对应于300至700公里深度的温度和压力下对含水橄榄岩成分进行合成实验。在科罗拉多大学，我们将通过单晶X射线衍射、电子探针和红外光谱来表征这些材料。 我们将在科罗拉多大学的金刚石压砧室（DAC）中使用单晶X射线衍射测量来测量这些实验中观察到的含水橄榄石、尖晶石和尖晶石相的压缩模量（等温体积模量）和热膨胀。在一年的资金支持下，我们预计能够完成一系列含水环木岩、wadsleyites和橄榄石的表征，并对其中几个样品进行高压压缩实验。由于体积模量与地震速度直接相关，如果这些相的压缩系数与无水变形有很大不同，则可能对过渡带矿物中实际存在的OH量施加一些限制。 此外，我们将继续合作研究通过布里渊光谱和GHz超声波干涉测量弹性性能，并向其他团体提供样品。

SmythEAR-0229315Hydrogen is perhaps the most poorly constrained compositional variable in the Earth, yet it has a controlling effect on many if not most geologic processes. This is a proposal to improve the understanding of the hydration state of the interior by investigation of the stability, crystal chemistry and equation of state of hydrous olivine, spinel, and spinelloid phases that would occur in and near a hydrous Transition Zone. In collaboration with colleagues at the Bavarian Geological Institute (Bayerisches Geoinstitut), we will perform synthesis experiments on hydrous peridotite compositions at temperatures and pressures corresponding to depths of 300 to 700 km. At the University of Colorado, we will characterize these materials by single crystal X-ray diffraction, electron microprobe and IR spectroscopy. We will use single-crystal X-ray diffraction measurements in the diamond anvil cell (DAC) at the University of Colorado to measure compressibilities (isothermal bulk moduli) and thermal expansion of the hydrous olivine, spinel and spinelloid phases observed in these experiments. With a single year of funding, we expect to be able to complete characterization of a series of hydrous ringwoodites, wadsleyites and olivines and to perform high-pressure compression experiments on several of these samples. Because the bulk modulus is directly related to seismic velocity, if the compressibilities of these phases differ greatly from the anhydrous modifications, it may be possible to place some constraint on the amount of OH actually present in the minerals of the Transition Zone. In addition, we will continue our collaborative studies on measurement of elastic properties by Brillouin spectroscopy and GHz ultrasonic interferometry, and make samples available to other groups.