HR: 0800h
AN: V51B-0535    [Abstracts]
TI: Cratonal lithosphere a potential recorder of ancient mantle plumes
AU: * Sleep, N H
EM: norm@pangea.stanford.edu
AF: Department of Geophysics, Stanford University, Stanford, CA 94305 United States
AB: In the conventional mantle plume hypothesis, hot plume material ponds at the base of the lithosphere. The deep cratonal lithosphere provides a record and a potential test of this aspect of plumes. First uplift and subsidence in the geological record give lthe more likely times of plume impingement. Second studies of pressure-temperature-time histories from zoned diamonds may make this process observable. I make analytical and numerical calculations relevant the the thermal history of the deep lithosphere. Physically stagnant-lid convection subsequent to the ponding of plume material heats the overlying lithosphere and cools the plume material. It thins the rheological boundary layer of ordinary mantle between overlying chemically buoyant cratonal lithosphere and the underlying plume material. Convection moves the chemically buoyant material producing a potentially observable pressure change. Loitering plume tails have a stronger effect than plume head episodes. They can occur only at times that the plate moves slowly, which provides another potential test. The xenolith geotherm provides a further constraints. If a thick layer of plume material is present, the scaling relationship for the thickness of the rheological boundary layer beneath a convecting lid is inverse to the viscosity of the underlying hot material to the fourth power at a given heat flow.
DE: 8110 Continental tectonics--general (0905)
DE: 8121 Dynamics, convection currents and mantle plumes
DE: 3660 Metamorphic petrology
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2004 AGU Fall Meeting