Exempel på the asthenosphere

• In continental rift settings, the emplacement of such large volumes of felsic melts requires a huge amount of mafic magma derived from uprising asthenosphere.

• Either of these mechanisms can cause the hot asthenosphere to rise close to the metasomatized lithosphere, initiating melting.

• In particular, is the source of within-plate basaltic magmas in an extensional setting the lithosphere, convecting asthenosphere or both?

• The extension of lithosphere accompanied with the upwelling of asthenosphere may be the key factor for the coeval magmas with different sources.

• We therefore favour the model whereby the eclogitic lower crust, together with the underlying lithospheric mantle, was delaminated, accompanied by asthenosphere upwelling.

• However, the contribution of asthenosphere to the generation of mafic magmatism would become ever greater along with the increase in extension of the lithosphere.

• The second chapter discusses the lithosphere and asthenosphere and the important role water plays in defining the brittle and ductile behaviour of the rocks in these regions.

• Temperatures high enough to produce basaltic partial melt in this decaying thermal anomaly would be located near the base of the lithosphere and in the immediately underlying asthenosphere.

• Several explanations have been proposed; a lower limit to the pliable asthenosphere, a phase transition, and most plausibly, depth-variation in the shear wave anisotropy.

• It was found that the asthenosphere had invaded the overlying lithosphere.

• Beneath the lithosphere is the asthenosphere, a relatively low-viscosity layer on which the lithosphere rides.

• The upwelling of asthenosphere is not involved in the actual rifting process.

• The upward flow of the asthenosphere results in decompression melting, magmatic underplating and some volcanism that may occur in the rift area.

• This decreasing in seismic waves velocity from lithosphere to asthenosphere could be caused by the presence of small percentage of melt in the asthenosphere.

• The steep dip angle of the subducting plate can correspond to a thicker wedge of asthenosphere and therefore a greater source of fertile mantle material.