PETROLOGY, ELASTICITY, AND COMPOSITION OF THE MANTLE TRANSITION ZONE

被引:364
作者
ITA, J
STIXRUDE, L
机构
关键词
D O I
10.1029/92JB00068
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
We compare the predictions of compositional models of the mantle transition zone to observed seismic properties by constructing phase diagrams in the MgO-FeO-CaO-Al2O3-SiO2 system and estimating the elasticity of the relevant minerals. Mie-Gruneisen and Birch-Murnaghan finite strain theory are combined with ideal solution theory to extrapolate experimental measurements of thermal and elastic properties to high pressures and temperatures. The resulting thermodynamic potentials are combined with the estimated phase diagrams to predict the density, seismic parameter, and mantle adiabats for a given compositional model. We find that the properties of pyrolite agree well with the observed density and bulk sound velocity of the upper mantle and transition zone. Piclogite significantly underestimates the magnitude of the 400-m velocity discontinuity and overestimates the velocity gradient in the transition zone. Substantially enriching piclogite in Al provides an acceptable fit to the observations. Invoking a chemical boundary layer between the uppermost mantle and transition zone leads to poor agreement with observed seismic properties for the compositions considered. Within the transition zone, the dissolution of garnet to Ca-perovskite near 18 GPa may explain the proposed 520-km seismic discontinuity. Below 700 km depth, all compositions disagree with observed bulk sound velocities, implying that the lower mantle is chemically distinct from the upper mantle.
引用
收藏
页码:6849 / 6866
页数:18
相关论文
共 178 条
[31]   UPPER MANTLE STRUCTURE IN WESTERN-CANADA [J].
DEYSARKAR, SK ;
WIGGINS, RA .
JOURNAL OF GEOPHYSICAL RESEARCH, 1976, 81 (20) :3619-3632
[32]   UPPER MANTLE STRUCTURE UNDER WESTERN-EUROPE FROM FUNDAMENTAL AND HIGHER MODE SURFACE-WAVES USING THE NARS ARRAY [J].
DOST, B .
GEOPHYSICAL JOURNAL INTERNATIONAL, 1990, 100 (01) :131-151
[33]   SEISMIC VELOCITIES IN MANTLE MINERALS AND THE MINERALOGY OF THE UPPER MANTLE [J].
DUFFY, TS ;
ANDERSON, DL .
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH AND PLANETS, 1989, 94 (B2) :1895-1912
[34]   PRELIMINARY REFERENCE EARTH MODEL [J].
DZIEWONSKI, AM ;
ANDERSON, DL .
PHYSICS OF THE EARTH AND PLANETARY INTERIORS, 1981, 25 (04) :297-356
[35]  
FAIRBORN JW, 1969, B SEISMOL SOC AM, V59, P1983
[36]   EXPERIMENTAL-DETERMINATION OF ELEMENT PARTITIONING AND CALCULATION OF PHASE-RELATIONS IN THE MGO-FEO-SIO2 SYSTEM AT HIGH-PRESSURE AND HIGH-TEMPERATURE [J].
FEI, Y ;
MAO, HK ;
MYSEN, BO .
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH AND PLANETS, 1991, 96 (B2) :2157-2169
[37]   SIMULTANEOUS HIGH-P, HIGH-T X-RAY-DIFFRACTION STUDY OF BETA-(MG,FE)2SIO4 TO 26-GPA AND 900-K [J].
FEI, YW ;
MAO, HK ;
SHU, JF ;
PARTHASARATHY, G ;
BASSETT, WA ;
KO, JD .
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH, 1992, 97 (B4) :4489-4495
[38]  
FINGER LW, 1976, AM MINERAL, V61, P303
[39]   UPPER MANTLE P-STRUCTURE ON OCEAN SIDE OF JAPAN-KURILE ARC [J].
FUKAO, Y .
GEOPHYSICAL JOURNAL OF THE ROYAL ASTRONOMICAL SOCIETY, 1977, 50 (03) :621-642
[40]  
FUKAO Y, 1982, HIGH PRESSURE RES GE, P285