MORB in the lowermost mantle beneath the western Pacific: Evidence from waveform inversion

被引：34

作者：

Konishi, Kensuke ^{[1
]}

Kawai, Kenji ^{[2
]}

Geller, Robert J. ^{[1
]}

Fuji, Nobuaki ^{[1
]}

机构：

[1] Univ Tokyo, Grad Sch Sci, Dept Earth & Planetary Sci, Tokyo 113, Japan

[2] Tokyo Inst Technol, Dept Earth & Planetary Sci, Tokyo 152, Japan

来源：

EARTH AND PLANETARY SCIENCE LETTERS | 2009年 / 278卷 / 3-4期

关键词：

waveform inversion; lowermost mantle; mid-ocean ridge basalt; pyrolite; phase transition; SUBDUCTED OCEANIC-CRUST; PLATE-TECTONICS; POST-PEROVSKITE; SHEAR VELOCITY; CONVECTION; BOUNDARY; MODEL; FATE;

D O I：

10.1016/j.epsl.2008.12.002

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 study the fine structure of the lowermost several hundred km of the large low shear velocity province (LLSVP) beneath the western Pacific by inverting the transverse components of long period (20-200 s) broadband seismic waveforms. We find a low S-velocity zone in the depth range from about 2550-2750 km, with the greatest decrease (relative to PREM) of about 0.2 km/s at depths of about 2650-2700 km. This suggests the presence of significant amounts of mid-ocean ridge basalt (MORB), for which the phase transitions from pv to ppv and from CaCl2-type to alpha-PbO2-type SiO2 result in a decrease in S-velocities. We also find an increase in the S-velocity, relative to this minimum, of about 0.15 km/s, peaking in the depth range from about 2750-2800 km, which is consistent with the phase transition from pv to ppv expected for average composition models such as pyrolite. (c) 2008 Elsevier B.V. All rights reserved.

引用

页码：219 / 225

页数：7

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