Geological confirmation for water-effected incipient melt origin of seismic low velocity zone (LVZ) beneath ocean basins.

It is reasonable to state that if there were no seismic low veloc-ity zone(LVZ)beneath ocean basins,there would be no seafloor spreading and plate tectonics.Over the past 50 years,plate tecton-ics has been developed into a powerful theory with unquestionable and irrefutable lines of evidence and predictive efficacies.Yet,markedly different views remain prevalent on the origin of the LVZ.These include the effect of incipient melt[1,2],weak astheno-sphere dictated by hydrous olivine[3],solid-state rheology change in response to optimal pressure and temperature conditions in the upper mantle[4],and mantle temperature variation[5].Such debate is common and healthy in the Earth science research towards unifying solutions,but can often cause confusions in the community that some scientific questions such as the origin of the LVZ may be forever debatable with no prospect for any consen-sus in the foreseeable future.The latter perception is understand-able because the LVZ debate has been continuing for over half a century[1-5].While a comprehensive review with a lengthy list of"pros"and"cons"is welcome,such a review may,on the other hand,make the above no-solution perception more persistent because reviews are commonly considered as summaries of state-of-the-art research progress without solid conclusions.