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SUMMARY:The temperature of the top of the mantle - Prof. Dan McKenzie 
DTSTART:20121112T170000Z
DTEND:20121112T180000Z
UID:TALK39404@talks.cam.ac.uk
CONTACT:Lois Salem
DESCRIPTION:The thickness of the lithosphere and melt generation are contr
 olled by the temperature of the mantle\, which in turn is dominated by con
 vective heat transfer. Traditional geological and geophysical arguments pr
 ovide limited\, but strong\, local constraints on mantle temperature\, fro
 m thermal models of spreading ridges and sinking slabs\, and from the mine
 ralogy of garnet peridotite nodules brought up by alkaline magmas. The wid
 espread installation of broad band seismometers now allows the S wave stru
 cture of the mantle to be mapped in considerable detail using surface wave
 s to a depth of ~300 km. Vs is principally controlled by temperature\, not
  by composition\, so we now have a method of mapping the 3D temperature of
  the upper part of the mantle. I will discuss our most recent maps\, produ
 ced from Keith Priestley's model of Vs generated from about three million 
 seismograms. The maps show a number of unexpected features. They show that
  the planform of the convective circulation beneath Africa and the Middle 
 East is a 3D spoke pattern\, with the hubs corresponding to the proposed l
 ocations of plumes. Beneath Asia thick lithosphere (~250 km) is now being 
 generated by continental shortening beneath the Zagros\, Hidu Kush\, Pamir
 s\, Tien Shan and Tibet.
LOCATION:Harker Room 1\, Department of Earth Sciences
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