The Seismic 8degrees Discontinuity and Partial Melting in Continental Mantle
Strong, scattered reflections beyond 8 degrees (8degrees) offset are characteristic features of all high-resolution seismic sections from the continents. The reflections identify a low-velocity zone below approximately 100 kilometers depth beneath generally stratified mantle. This zone may be caused by partial melting, globally initiated at equal depth in the continental mantle. Solid state is again attained at the Lehmann discontinuity in cold, stable areas, whereas the zone extends to near the 400-kilometer discontinuity in hot, tectonically active areas. Thus, the depth to the Lehmann discontinuity may be an indicator of the thermal state of the continental mantle.
Thybo
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H. Thybo, Geological Institute, University of Copenhagen, Oster Voldgade 10, DK-1350 Copenhagen K, Denmark. E. Perchuc, Institute of Geophysics, Polish Academy of Sciences, ul.Ksiecia Janusza 64, PL-01452 Warsaw, Poland.
Perchuc
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