Hydrous Spinelloids and the Hydration State of the Mantle

Smyth EAR-0087279这是一项研究水尖晶石和尖晶石相的稳定性、晶体化学和状态方程的建议，这些相可能出现在地幔过渡带(410-670公里深)。在巴伐利亚地质研究所(Bayerisches GeoInstitute)的同事们的合作下，研究人员将进行合成实验，以确定地幔成分中是否存在尖晶石V，并更好地精炼尖晶石IV(Wadsleyite II)的压力-温度-组成场。在含水体系中的初步实验已经产生了足够大小的晶体，可用于单晶衍射法，因此将用这种方法分析运行产物。他们将使用钻石顶压室(DAC)中的单晶X射线衍射测量来测量在这些实验中观察到的含水尖晶石的可压缩性(等温体弹性系数)和热膨胀。由于体积模数与地震速度直接相关，如果这些相的可压缩性与无水修改有很大不同，则可能对过渡带矿物中实际存在的OH的量施加一些限制。还将通过各种光谱和超声波方法提供样品供合作研究。

Smyth EAR-0087279 This is a proposal to investigate the stability, crystal chemistry and equation of state of hydrous spinel and spinelloid phases that could occur in the Transition Zone of the mantle (410-670km depth). In collaboration with colleagues at the Bavarian Geological Institute (Bayerisches Geoinstitut), the investigators will perform synthesis experiments to see if spinelloid V may exist in mantle compositions and to better refine the pressure-temperature-composition field of spinelloid IV (wadsleyite II). Preliminary experiments in hydrous systems have produced crystals of sufficient size for single-crystal diffraction methods, so run products will be analyzed by this method. They will use single-crystal X-ray diffraction measurements in the diamond anvil cell (DAC) to measure compressibilities (isothermal bulk moduli) and thermal expansion of the hydrous spinelloid observed in these experiments. 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. Samples will also be made available for collaborative studies by various spectroscopic and ultrasonic methods.