Influence of FeO and H on the electrical conductivity of olivine

被引:30
作者
Dai, Lidong [1 ,2 ]
Karato, Shun-ichiro [2 ]
机构
[1] Chinese Acad Sci, Inst Geochem, Key Lab High Temp & High Pressure Study Earths In, Guiyang 550002, Guizhou, Peoples R China
[2] Yale Univ, Dept Geol & Geophys, New Haven, CT 06511 USA
关键词
Electrical conductivity; Olivine aggregate; Iron; Hydrogen; Terrestrial planets; WATER-CONTENT; LUNAR MANTLE; HYDROGEN; PRESSURE; TEMPERATURE; CONSTRAINTS; DEPENDENCE; DIFFUSION; BOUNDARY; MINERALS;
D O I
10.1016/j.pepi.2014.10.006
中图分类号
P3 [地球物理学]; P59 [地球化学];
学科分类号
0708 ; 070902 ;
摘要
The influence of Fe (iron) and H (hydrogen) on the electrical conductivity of olivine was investigated. Synthetic olivine aggregates with the X-Fe = Fe/(Fe + Mg) (molar ratio) = 21-64% with the water content of 84-620 ppm wt (Paterson calibration) were prepared and their electrical conductivity was measured at P = 4 GPa and T = 873-1473 K. The impedance spectroscopy was used to calculate the DC electrical conductivity. We found that electrical conductivity of samples increases with increasing FeO content in both anhydrous and hydrous olivine. However, the way in which FeO enhances electrical conductivity is different between anhydrous and hydrous olivine. In anhydrous sample, the activation energy is reduced with FeO content and hence the effect of FeO content is large at low temperatures, but its effect is small at mantle temperatures. In contrast, FeO content does not affect the activation energy in hydrous olivine, and consequently, the magnitude of FeO effect is nearly independent of temperature. For both anhydrous and hydrous olivine, the influence of FeO is only modest at high temperatures (increase in conductivity by a factor of 2 for the increase in FeO by 20% (e.g., from 10 to 30%)). In contrast, the FeO content has relatively large effects at low temperatures for anhydrous olivine. However, the role of hydrogen is large at low temperatures and hydrogen mechanism dominates under most cases. Therefore the influence of FeO on electrical conductivity is small at all temperatures for a plausible range of water content. We conclude that the water (hydrogen) content in a terrestrial planet can be inferred from observed conductivity without substantial influence of FeO if the temperature is constrained. The present results provide a basis for the interpretation of electrical conductivity model of other planets with different FeO contents. (C) 2014 Elsevier B.V. All rights reserved.
引用
收藏
页码:73 / 79
页数:7
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