DOI: 10.1016/j.epsl.2018.07.022
Scopus记录号: 2-s2.0-85050629111
论文题名: Dynamics of rheological heterogeneities in mantle plumes
作者: Farnetani C.G. ; Hofmann A.W. ; Duvernay T. ; Limare A.
刊名: Earth and Planetary Science Letters
ISSN: 0012821X
出版年: 2018
卷: 499 起始页码: 74
结束页码: 82
语种: 英语
英文关键词: dynamics
; heterogeneity
; mantle plume
; mixing
; rheology
Scopus关键词: Buoyancy
; Dynamics
; Isotopes
; Mixing
; Rheology
; Viscosity
; Volcanoes
; Flow charac-teristics
; heterogeneity
; Horizontal velocity
; Mantle plume
; Melt productivity
; Plume buoyancy fluxes
; Stability domains
; Viscosity ratios
; Thermal plumes
; basalt
; heterogeneity
; mantle plume
; mixing
; rheology
; timescale
; Hawaiian Islands
英文摘要: The geochemical record of Hawaiian basalts has been interpreted to reflect vertically stretched, partly filament-like heterogeneities in the Hawaiian plume, but one alternative interpretation has been that this record reflects intra-conduit mixing, caused by rheological contrasts across the conduit. Here we present numerical simulations of a mantle plume carrying rheological heterogeneities λ times more viscous than the surrounding fluid. Our first objective is to quantify how the heterogeneity deforms during upwelling. We find a full spectrum of shapes, from stretched filaments to nearly undeformed blobs, and we map the respective stability domain as a function of the viscosity ratio λ and of the flow characteristics, including the plume buoyancy flux. Our second objective is to test the hypothesis that a rheological heterogeneity can cause intra-conduit mixing. Although horizontal velocities do appear across the plume conduit, we have not found any toroidal “doughnut-shaped swirl” mode. Instead we show that perturbations of the flow trajectories are a local phenomenon, unable to cause permanent mixing. Our third objective is to determine over which time-scales a rheological heterogeneity crosses the magma capture zone (MCZ) beneath a hotspot volcano. For a blob-like heterogeneity of radius 30–40 km and viscosity ratio 15–20, the crossing time-scale is less than 1 Myr. Contrary to a stretched filament, a blob can entirely fill the MCZ, thereby representing the unique source rock of partial melts feeding a volcano. If the heterogeneity has a distinct isotopic fingerprint (or a distinct fertility), surface lavas will then record an isotopic fluctuation (or a fluctuation in melt productivity) lasting 0.5–0.8 Myr. Our simulations predict that such fluctuations should occur preferentially in low buoyancy flux hotspots, where blob-like rheological heterogeneities are more easily preserved than in the vigorous Hawaiian plume. © 2018 Elsevier B.V. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/109724
Appears in Collections: 影响、适应和脆弱性 气候变化事实与影响
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作者单位: Institut de Physique du Globe de Paris, Sorbonne Paris Cité, Université Paris Diderot, UMR 7154, Paris, 75005, France; Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY 10964, United States; Max-Planck-Institut für Chemie, Hahn-Meitner-Weg 1, Mainz, 55128, Germany; Research School of Earth Sciences, The Australian National University, Canberra, ACT 2601, Australia
Recommended Citation:
Farnetani C.G.,Hofmann A.W.,Duvernay T.,et al. Dynamics of rheological heterogeneities in mantle plumes[J]. Earth and Planetary Science Letters,2018-01-01,499