Olivine-wadsleyite transition in the system (Mg,Fe)2SiO4
Olivine-wadsleyite transition in the system (Mg,Fe)2SiO4
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DOI：
10.1029/2003jb002438
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发表时间：
2004-02-25
影响因子：
3.9
通讯作者：
Funakoshi, K
中科院分区：
文献类型：
--
作者：
Katsura, T;Yamada, H;Funakoshi, K
[1]在Kawai型高压装置上用淬冷法测定了(Mg，Fe)(2)SiO4系统在1600和1900K下橄榄石-瓦兹利石相变的相关系。以氧化镁为压力标准，用原位X射线衍射法测定压力，测量精度优于0.2 Gpa。在1600K和1900K时，端元Mg2SiO4的转变压力分别为14.2和15.4 GPa.1600K和1900K时，Fe和Mg在橄榄石和水晶石之间的分配系数分别为0.51和0.61。通过比较不连续面的深度和转变压力，估算出热解岩上地幔在410 km深度处的温度为1760+/-45K。上地幔底部的温度估计为1880+/-50K，热解地幔中橄榄石-水滑石转变的厚度为7-13公里，这取决于垂直热传递的效率。可以忽略热扩散的快速垂直流动区域(例如对流支路)的过渡间隔应该比热扩散有效的停滞区大。这与短周期地震波观测结果明显矛盾，后者表明最大厚度为
[1] Phase relations of the olivine-wadsleyite transition in the system (Mg, Fe)(2)SiO4 have been determined at 1600 and 1900 K using the quench method in a Kawai-type high-pressure apparatus. Pressure was determined at a precision better than 0.2 GPa using in situ X-ray diffraction with MgO as a pressure standard. The transition pressures of the end-member Mg2SiO4 are estimated to be 14.2 and 15.4 GPa at 1600 and 1900 K, respectively. Partition coefficients for Fe and Mg between olivine and wadsleyite are 0.51 at 1600 K and 0.61 at 1900 K. By comparing the depth of the discontinuity with the transition pressure, the temperature at 410 km depth is estimated to be 1760 +/- 45 K for a pyrolitic upper mantle. The mantle potential temperature is estimated to be in the range 1550-1650 K. The temperature at the bottom of the upper mantle is estimated to be 1880 +/- 50 K. The thickness of the olivine-wadsleyite transition in a pyrolitic mantle is determined to be between 7 and 13 km for a pyrolitic mantle, depending on the efficiency of vertical heat transfer. Regions of rapid vertical flow ( e. g., convection limbs), in which thermal diffusion is negligible, should have a larger transition interval than stagnant regions, where thermal diffusion is effective. This is in apparent contradiction to short-period seismic wave observations that indicate a maximum thickness of