Crustal resistivity structure of the Lunpola basin in central Tibet and
its tectonic implications
Abstract
In the central Tibetan Plateau, an east-west trending band of basins is
developed. How such topography formed and the underlying geodynamic
processes are still in debate. Magnetotelluric data were collected
across the Lunpola basin to study the crustal structure beneath central
Tibet. Phase tensors and 3-D inversion are employed to obtain the
electrical resistivity model. Our model clearly portrays conductive
sedimentary layers beneath the basins with average resistivity of 2.0
Ω·m. The low-resistivity mid-to-lower crust is revealed beneath the
Lunpola basin with bulk resistivity of 20 Ω·m and fluid fraction of
1.3-3.0%, which would be attributed to partial melting. Compared to the
significant conductive crust in southern Tibet, the crustal rheology is
less well developed beneath central Tibet. We propose that the
asthenospheric flow beneath central Tibet is responsible for the crustal
partial melting and drives the eastward escape of the continental
lithosphere in a rigid block fashion.