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Large cold anomalies in the deep mantle and mantle instability in the Cretaceous
Author(s) -
Yuen D.A.,
Čadek O.P.,
Boehler R.,
Moser J.,
Matyska C.
Publication year - 1994
Publication title -
terra nova
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.353
H-Index - 89
eISSN - 1365-3121
pISSN - 0954-4879
DOI - 10.1111/j.1365-3121.1994.tb00490.x
Subject(s) - geology , mantle (geology) , mantle wedge , mantle convection , transition zone , core–mantle boundary , subduction , geophysics , hotspot (geology) , slab , instability , crustal recycling , seismology , tectonics , mechanics , physics , continental crust
Two large cold masses in the deep mantle have been delineated by using long‐wavelength seismic tomographic models in conjunction with mineralogical experimental data at high pressure. These cold anomalies are found under the western Pacific and the Americas with temperatures more than 1000 degrees below the ambient mantle temperature. These strong cold anomalies existing in the lower mantle today would suggest that there might have existed not too long ago a substantial temperature jump across a thermal boundary layer between the upper and lower mantle. Numerical simulations in an axisymmetric spherical‐shell model incorporating the two major phase transitions have shown that very large pools of cold material with temperatures of around 1500 K can be flushed down to the core–mantle boundary during this tumultuous gravitational instability. A correlation is found between the current locations of these very cold masses and regions of past subduction since the Cretaceous. Correlation analysis shows that the slab mass‐flux into the lower mantle does not behave in a steady‐state fashion. These findings may support the idea of a strong gravitational instability with origins in the transition zone, as suggested by numerical models of mantle convection.