DOI: 10.1016/j.epsl.2020.116242
论文题名: Unravelling partial melt distribution in the oceanic low velocity zone
作者: Gardés E. ; Laumonier M. ; Massuyeau M. ; Gaillard F.
刊名: Earth and Planetary Science Letters
ISSN: 0012821X
出版年: 2020
卷: 540 语种: 英语
中文关键词: distribution and dynamics of volatiles and melt in the upper mantle
; low velocity zone
; mantle incipient melting
; volatile-rich melt interconnection in mantle rocks
英文关键词: Carbon dioxide
; Drops
; Geochemical surveys
; Indium compounds
; Melting
; Rocks
; Seismic waves
; Seismology
; Shear waves
; Velocity
; Wave propagation
; Geophysical surveys
; Heterogeneous distributions
; Incipient melting
; Lithospheric temperatures
; Low velocity zones
; Mantle rocks
; Shear wave velocity
; Upper mantle
; Shear flow
; low velocity zone
; melt
; P-T conditions
; partial melting
; seismic velocity
; spatial distribution
; upper mantle
; volatile element
英文摘要: The widespread low seismic velocity zone (LVZ) in the shallow oceanic mantle has long been debated in terms of mantle melting. At LVZ depths, volatiles (CO2 and H2O) are present in minute amounts, which implies mantle incipient melting down to below 1000 °C with the production of minute amounts of volatile-rich melt, well below 1 vol.%. However, melt compositions and distributions in the incipient melting regime have only been inferred from experiments departing from actual mantle conditions. Here, we experimentally reproduce incipient melting by re-equilibrating a naturally CO2- and H2O-bearing mantle rock at mantle temperatures and pressure. By using cutting-edge microscopy characterizations, we evidence that minute amounts of volatile-rich melts fully interconnect in mantle rocks down to lithospheric temperatures, enabling thus the modification of geophysical signals from the mantle. These findings and the correspondence of the domain of local, sharp drops in shear wave velocity (Vs) with the domain of (CO2+H2O)-melting in the LVZ strongly supports that these geophysical anomalies relate to mantle melting. Geophysical surveys image in situ the very low and highly heterogeneous distribution of melt in the mantle generated by the very low and highly heterogeneous distribution of volatiles probed by surficial geochemical surveys. The global-scale geophysical signature of the LVZ appears mainly unaffected because the average background melt fraction is very low, estimated at ∼0.03-0.05 vol.% melt. However, enhanced geophysical signals arise from sporadic, localized areas where melt fraction is increased, such as the ∼0.2 vol.% melt estimated for detecting sharp Vs drops using SS precursors. In-depth deciphering of the dynamics of melt and volatiles in the LVZ calls for investigations on the seismic velocity, permeability and rheology of partially molten mantle rocks covering the diversity of mantle melt compositions, fractions and temperatures. © 2020 Elsevier B.V. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/164975
Appears in Collections: 气候变化与战略
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作者单位: Centre de recherche sur les Ions, les Matériaux et la Photonique (CIMAP), Normandie Université, ENSICAEN, UNICAEN, CEA, CNRS, Caen, France; Laboratoire Magmas et Volcans (LMV), Université Clermont Auvergne, CNRS, IRD, OPGC, Clermont-Ferrand, France; Deep and Early Earth Processes Research Group (DEEP), Department of Geology, University of Johannesburg, Auckland Park, South Africa; Institut des Sciences de la Terre d'Orléans (ISTO), Université d'Orléans, CNRS, BRGM, Orléans, France
Recommended Citation:
Gardés E.,Laumonier M.,Massuyeau M.,et al. Unravelling partial melt distribution in the oceanic low velocity zone[J]. Earth and Planetary Science Letters,2020-01-01,540