水对Wadsleyite和Ringwoodite电导率的影响及地球动力学意义

在 Kawai-1000型多顶砧压机上,利用橄榄石相变人工合成地幔转换带矿物 wadsleyite 和 ringwoodite,其含水量从0.03wt%到2.0wt%变化不等。在压力14～16GPa,温度873K～1273K,通过 Mo:MoO_2固体反应控制氧逸度的条件下,利用阻抗谱分析方法,测量获得了这些样品的电导率。实验结果显示:wadsleyite 的电导率与 C_H^(0.66)呈正比,ringwoodite 的电导率与C_H^(0.69)呈正比,水极大地增强了样品的电导率;在我们的实验条件下,含水 wadsleyite 和 ringwoodite 样品的主要电荷载体是自由质子。另外,结合大地电磁反演获得的电导率结果和我们的实验数据,我们推断中国东北地区地幔转换带中的水含量约为0.1～0.3wt%,远远高于上地幔中的水含量,这或许表明在410km 处可能发生了部分熔融。

Preliminary Deformation Experiment of Ringwoodite at 20 GPa and 1 700 K Using a D-DIA Apparatus

A deformation experiment of ringwoodite with a strain of 9% was achieved at 20 GPa and 1 700 K and at a strain rate of 3×10^-5 s^-1 using a deformation-DIA （D-DIA） apparatus and a multi-anvil 6-6 （MA 6-6） assembly. The crystallographic orientations of the deformed sample were successfully analyzed by the electron backscatter diffraction （EBSD） method, although any notable latticepreferred orientation （LPO） was not observed presumably due to the insufficient strain in the present experiment. In this study, the deformation experiment on ringwoodite succeeded at P-T conditions consistent with the lower part of the mantle transition zone and at a controlled strain rate for the first time. The present study extended the pressure range of deformation experiments in the D-DIA apparatus from 16 GPa in our earlier study to 20 GPa at 1 700 K. The successful extension of the pressure range demonstrates potential importance of the D-DIA apparatus in studying rheological properties of minerals under the P-T conditions of the whole mantle transition zone.

First Terrestrial Occurrence of Ringwoodite

Several of the known over 3000 minerals possess great typomorphic implication and experienced twists and turns of their discovery. Ringwoodite is the most outstanding of them. In 1931, Goldshmidt suggested that the crystal structure of Mg2GeO4 could show two polymorphs for olivine and spinel. Based on this, in 1936, J. D. Bernal put forward his bold assumption that the increase of seismic velocity in mantle is caused by

The Time Events and the Poetics of Care for the Oceans

The images of the oceans often inspire us to take a poetic lift of the spirit for an escape from the daily boredom or troubles related to the social restriction based on the ideological hierarchy.On the other hand,however,the collective human desires have no good ethics to discipline the insatiable enjoyment that has obviously damaged the environment and polluted the oceans.In this short paper,I focus on the concepts of the time event,Aion and Chronos,with the three poems related to the images of the oceans written by a Taiwan Residents poet,Hui Tong;I also try to understand how the origin of the water on our Earth comes from.In fact,our Earth has the“liquid”oceans on the surface and also the hidden“solid”oceans,the blue crystal rocks called ringwoodite,within Earth’s mantle.The oceans absorb heat and the tiny ocean plants called phytoplankton drifting with the oceanic currents produce oxygen through photosynthesis for the human health as well.But the contemporary environmental problem is that the chronic damages of the biodiversity by the human collective desires have affected the oceans to become seriously polluted.Therefore,we have the feelings of ambivalence toward the images of the oceans:tranquility,transience,creativity,oblivion or corruption and hostility for the human bad habits.

Hydration effects on crystal structures and equations of state for silicate minerals in the subducting slabs and mantle transition zone

There are potentially huge amounts of water stored in Earth's mantle, and the water solubilities in the silicate minerals range from tens to thousands of part per minion(ppm, part per million). Exploring water in the mantle has attracted much attention from the societies of mineralogy and geophysics in recent years. In the subducting slab, serpentine breaks down at high temperature, generating a series of dense hydrous magnesium silicate(DHMS) phases, such as phase A, chondrodite, clinohumite, etc. These phases may serve as carriers of water as hydroxyl into the upper mantle and the mantle transition zone(MTZ). On the other hand, wadsleyite and ringwoodite, polymorphs of olivine, are most the abundant minerals in the MTZ, and able to absorb significant amount of water(up to about 3 wt.% H_2O). Hence, the MTZ becomes a very important layer for water storage in the mantle, and hydration plays important roles in physics and chemistry of the MTZ. In this paper, we will discuss two aspects of hydrous silicate minerals:(1) crystal structures and(2) equations of state(Eo Ss).