Thermal-rheological bottom boundary of continental lithosphere: case studies on cratons of Kaapvaal, Fennoscandia, and Slave

doi:10.7523/j.issn.2095-6134.2015.01.013

Abstract

Abstract:

A fundamental premise of the plate tectonics is that a relatively rigid lithosphere moves over a weaker asthenosphere. Howerer, the nature of the lithosphere-asthenosphere boundary (LAB) remains poorly understood, especially that beneath the continental lithosphere. At the present there are several definitions for the LAB based on different measurements. By defining the LAB as the depth where the effective viscosity has a weak minimum, a semi-analytical method to determine this bottom boundary is presented. This boundary is called thermal-rheological bottom boundary because it combines the thermal and rheological properties of the lithospheric mantle. Studies on the three famous cratons (Kaapvaal, Fennoscandia, Slave) show that the thermal-rheological LAB is at the depth of ~250 km, which is consistent with the results based on other geophysical methods (for example, magnetotelluric method). The thermal-rheological LAB is closer to the LAB in the plate tectonics, because it provides the possibility for the mechanical plates moving over the asthenosphere. At the thermal-rheological LAB and in its adjacent area, the deformation mechanism is predominant by diffuse creep, and the differential stress level is low while the strain rate is high.

Key words: plate tectonics, lithosphere-asthenosphere boundary, continental lithosphere, craton, thermal-rheological bottom boundary

CLC Number:

R541

WEI Rongqiang, LI Wuyang. Thermal-rheological bottom boundary of continental lithosphere: case studies on cratons of Kaapvaal, Fennoscandia, and Slave[J]. , 2015, 32(1): 74-81.

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