MORB in the lowermost mantle beneath the western Pacific: Evidence from waveform inversion
MORB in the lowermost mantle beneath the western Pacific: Evidence from waveform inversion
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西太平洋下地幔中的 MORB：来自波形反演的证据
DOI：
10.1016/j.epsl.2008.12.002
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发表时间：
2009
影响因子：
5.3
通讯作者：
N. Fuji
中科院分区：
文献类型：
--
作者：
Kensuke Konishi;K. Kawai;R. Geller;N. Fuji
通过反演长周期（20-200 s）宽频带地震波形的横向分量，研究了西太平洋大的低剪切速度区（LLSVP）最低几百km的精细结构。我们发现一个低的S-速度区的深度范围从约2550-2750公里，与最大的减少（相对于PREM）约0.2公里/秒的深度约2650-2700公里。这表明存在大量的洋中脊玄武岩（MORB），其从pv到ppv和从CaCl 2型到α-PbO 2型SiO2的相变导致S速度降低。我们还发现，在S-速度的增加，相对于这个最小值，约0.15公里/秒，峰值在深度范围从约2750-2800公里，这是一致的平均组成模型，如地幔岩预期从pv到ppv的相变。
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 α-PbO2-type SiO2result 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.