Provenance of Tibetan Geoid Ridge and its Implication to the Collision
Evolution between India and Tibet
Abstract
The geoid minima in the Indian Ocean and North Eurasia are separated by
the Tibetan Geoid Ridge (TGR), yet the origin of TGR remains poorly
constrained. Spherical harmonic analysis and geoid kernels indicate that
the TGR has wavelengths of degrees 7-10 and is generated by density
anomalies of degrees 7-10 in the mantle. By employing numerical geoid
modelling with four different tomography-derived density structures, we
determined that abundant high-density anomalies in the mantle transition
zone beneath Tibet are responsible for TGR. Additionally, two previously
proposed alternative evolving scenarios of the India-Tibet collision —
Indian lithosphere subduction and Tibetan lithosphere dripping — are
evaluated through geoid calculation. The former suggests abundant
high-density structures in the Tibetan transition zone, which can
generate a well-constrained TGR, while the latter does not. Therefore,
we regard the Indian lithosphere subduction as a more plausible evolving
scenario.