Silicon and oxygen self-diffusion in stishovite: Implications for stability of SiO2-rich seismic reflectors in the mid-mantle
Silicon and oxygen self-diffusion in stishovite: Implications for stability of SiO2-rich seismic reflectors in the mid-mantle
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石英石中硅和氧的自扩散：对中地幔中富含 SiO2 的地震反射体稳定性的影响
DOI：
10.1016/j.epsl.2016.11.044
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发表时间：
2017
期刊：
影响因子：
--
通讯作者：
H.
中科院分区：
文献类型：
--
作者：
Xu;F.;Yamazaki;D.;Sakamoto;N.;Sun;W.;Fei;H. and Yurimoto;H.
在14.0- 21.5GPa和1673-2073 K的压力下，研究了硅和氧在硅镁石单晶中的扩散。Si（D Si）和O（D O）的自扩散系数被确定为D Si [m2/s]= 2.4× 10− 12 exp {−（237 [kJ/mol]+ 6.0 [cm3/mol]× P）/RT}和DO [m2/s]= 7.2× 10 - 11exp ε {-（263 [kJ/mol]+4.8 [cm 3/mol]× P）/RT}，其中P是压力（GPa），T是绝对温度（K），R是理想气体常数。结果表明，Si的扩散比O的扩散慢一个数量级，Si是硅镁石塑性变形的速率控制元素。硅扩散在斯氏石英被评估为至少三个数量级慢于在中地幔条件下的bridgmanite。因此，俯冲到下地幔中的高粘度富SiO2组分作为地震反射体长期存在，而不会与周围以桥镁石为主的地幔混合。
Diffusion of Si and O in single crystal stishovite was examined at pressures of 14.0–21.5 GPa and temperatures of 1673–2073 K. Self-diffusion coefficients of Si (D Si) and O (D O) were determined as D Si [m 2/s]= 2.4× 10− 12 exp{−(237 [kJ/mol]+ 6.0 [cm 3/mol]× P)/R T} and D O [m 2/s]= 7.2× 10− 11 exp{−(263 [kJ/mol]+ 4.8 [cm 3/mol]× P)/R T}, respectively, where P is pressure (in GPa), T is absolute temperature (in K) and R is the ideal gas constant. It was revealed that diffusion of Si is approximately one order of magnitude slower than that of O and, thus, Si is the rate-controlling element for plastic deformation of stishovite. Si diffusion in stishovite is assessed to be at least three orders of magnitude slower than that in bridgmanite under mid-mantle conditions. Therefore, it is anticipated that highly viscous SiO 2-rich components subducted into the lower mantle persist as the seismic reflectors for long term without mixing up with the bridgmanite-dominated surrounding mantle.