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Durham University

Department of Earth Sciences

Profile

Publication details for Professor Yaoling Niu

Niu, Yaoling & O'Hara, M.J. (2003). Origin of ocean island basalts: A new perspective from petrology, geochemistry and mineral physics considerations. Journal of Geophysical Research: Solid Earth 108(B4): 2209.

Author(s) from Durham

Abstract

Consideration of petrology, geochemistry, and mineral physics
suggests that ancient
subducted oceanic crusts cannot be the source materials supplying ocean
island basalts
(OIB). Melting of oceanic crusts cannot produce high-magnesian OIB lavas.
Ancient
oceanic crusts (>1 Ga) are isotopically too depleted to meet the required
values of most
OIB. Subducted oceanic crusts that have passed through subduction zone
dehydration are
likely to be depleted in water-soluble incompatible elements (e.g., Ba,
Rb, Cs, U, K, Sr, Pb)
relative to water-insoluble incompatible elements (e.g., Nb, Ta, Zr, Hf,
Ti). Melting of
residual crusts with such trace element composition cannot produce OIB.
Oceanic crusts, if
subducted into the lower mantle, will be >2% denser than the ambient
mantle at shallow
lower mantle depths. This negative buoyancy will impede return of the
subducted oceanic
crusts into the upper mantle. If subducted oceanic crusts melt at the base
of the mantle,
the resultant melts are even denser than the ambient peridotitic mantle,
perhaps by as
much as 15%. Neither in the solid state nor in melt form can bulk oceanic
crusts
subducted into the lower mantle return to upper mantle source regions of
oceanic basalts.
Deep portions of recycled oceanic lithosphere are important geochemical
reservoirs hosting
volatiles and incompatible elements as a result of metasomatism taking
place at the
interface between the low-velocity zone and the cooling and thickening
oceanic
lithosphere. These metasomatized and recycled deep portions of oceanic
lithosphere are the
most likely candidates for OIB sources in terms of petrology, geochemistry
and mineral
physics. INDEX TERMS: 1025 Geochemistry: Composition of the mantle; 3040
Marine Geology and
Geophysics: Plate tectonics (8150, 8155, 8157, 8158); 8121 Tectonophysics:
Dynamics, convection currents
and mantle plumes; 8124 Tectonophysics: Earth�s interior�composition
and state (1212); 8125
Tectonophysics: Evolution of the Earth; KEYWORDS: OIB sources, mantle
plumes, recycled ocean crust,
oceanic lithosphere, low-velocity zone metasomatism, mantle convection