Lithospheric density and thermal structure of the Tibetan Plateau

We developed a density model of the lithosphere beneath the Tibet Plateau using the joint inversion of gravity and seismic surface wave data. Based on density and seismic velocity, we revealed the lithospheric thermal structure. Simulation tests show that the lateral resolution of the density model from the joint inversion is 1°, which is higher than that from surface wave inversion. The lithospheric temperature field from the joint inversion of density and seismic velocity shows an uncertainty of ~50°C beneath the Tibetan Plateau, which is much lower than that constrained by seismic velocity alone. Our density and thermal models show that: (1) The lower crust of the Tibetan Plateau has a low density and a high temperature, indicating crustal partial melting and crustal flow. (2) The lithosphere mantle beneath the plateau shows high density and high temperature, indicating partial melting and underplating of the upper mantle. (3) Low-density anomalies appear in the lithospheric mantle of the Bangonghu-Nujiang and Longmucuo-Shuanghu sutures, consistent with low Vs anomalies, possibly caused by the hydration of peridotite in the lithospheric mantle. (4) Low-density and low-temperature anomalies are found in the lithospheric mantle beneath the Yungui Plateau, the Sichuan Basin and the Ordos Block. These anomalies are consistent with the characteristics of cratonic lithospheric mantle.