Composition and temperature of the Earth's core constrained by combining ab initio calculations and seismic data

被引:235
作者
Alfè, D
Gillan, MJ
Price, GD
机构
[1] UCL, Dept Phys & Astron, London WC1E 6BT, England
[2] Univ London Birkbeck Coll, Res Sch Geol & Geophys Sci, London WC1E 6BT, England
[3] UCL, London WC1E 6BT, England
关键词
chemical composition; core; seismology; simulation;
D O I
10.1016/S0012-821X(01)00568-4
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
It is shown how ab initio techniques based on density functional theory can be used to calculate the chemical potentials of the leading candidate impurity elements (S, 0 and Si) in the Earth's solid inner core and liquid outer core. The condition that these chemical potentials be equal in the solid and liquid phases provides values for the ratios of the impurity mol fractions in the inner and outer core. By combining the estimated ratios with ab initio values for the impurity molar volumes in the two phases, and demanding that the resulting density discontinuity across the inner-core boundary agree with free-oscillation data, we obtain estimates for the concentrations of S, O and Si in the core. The results show that O partitions much more strongly than S and Si from solid to liquid, and indicate that the presence of O in the core is essential to account for seismic measurements. We suggest that if compositional convection drives the Earth's magnetic field, then the presence of O may be essential for this compositional convection. (C) 2002 Elsevier Science B.V. All rights reserved.
引用
收藏
页码:91 / 98
页数:8
相关论文
共 38 条
[1]   Structure and dynamics of liquid iron under Earth's core conditions [J].
Alfè, D ;
Kresse, G ;
Gillan, MJ .
PHYSICAL REVIEW B, 2000, 61 (01) :132-142
[2]   First-principles simulations of liquid Fe-S under Earth's core conditions [J].
Alfe, D ;
Gillan, MJ .
PHYSICAL REVIEW B, 1998, 58 (13) :8248-8256
[3]   The melting curve of iron at the pressures of the Earth's core from ab initio calculations [J].
Alfè, D ;
Gillan, MJ ;
Price, GD .
NATURE, 1999, 401 (6752) :462-464
[4]   Thermodynamic stability of Fe/O solid solution at inner-core conditions [J].
Alfè, D ;
Price, GD ;
Gillan, MJ .
GEOPHYSICAL RESEARCH LETTERS, 2000, 27 (16) :2417-2420
[5]   Oxygen in the Earth's core:: a first-principles study [J].
Alfè, D ;
Price, GD ;
Gillan, MJ .
PHYSICS OF THE EARTH AND PLANETARY INTERIORS, 1999, 110 (3-4) :191-210
[6]   Constraints on the composition of the Earth's core from ab initio calculations [J].
Alfè, D ;
Gillan, MJ ;
Price, GD .
NATURE, 2000, 405 (6783) :172-175
[7]  
ALFE D, UNPUB PHYS REV B
[8]   THE CHEMICAL-COMPOSITION OF THE EARTH [J].
ALLEGRE, CJ ;
POIRIER, JP ;
HUMLER, E ;
HOFMANN, AW .
EARTH AND PLANETARY SCIENCE LETTERS, 1995, 134 (3-4) :515-526
[9]   Experimental melting curve of iron revisited [J].
Anderson, OL ;
Duba, A .
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH, 1997, 102 (B10) :22659-22669
[10]   AN EQUATION OF STATE FOR LIQUID-IRON AND IMPLICATIONS FOR THE EARTHS CORE [J].
ANDERSON, WW ;
AHRENS, TJ .
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH, 1994, 99 (B3) :4273-4284