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Ongoing controversies on the timing and kinematics of the Indo–Asia collision can be solved by palaeomagnetically determined palaeolatitudes of terranes bounding the Indo–Asia suture zone. We show here, based on new palaeomagnetic data from the Linzizong volcanic rocks (54–47 Ma) near the city of Lhasa, that the latitude of the southern margin of Asia was 22.8 ± 4.2°N when these rocks were deposited. This result, combined with revised palaeomagnetic results from the northernmost sedimentary units of Greater India and with apparent polar wander paths of India and Eurasia, palaeomagnetically constrain the collision to have occurred at 46 ± 8 Ma (95 per cent confidence interval). These palaeomagnetic results are consistent with tomographic anomalies at 15–25°N that are interpreted to locate the Tethyan oceanic slab that detached following collision, and with independent 56–46 Ma collision age estimates inferred from the timing of slowing down of India, high pressure metamorphism, the end of marine sedimentation and the first occurrence of suture zone and arc detritus on the Greater Indian margin. When compared with apparent polar wander paths of India and Eurasia, the ∼46 Ma onset of collision at 22.8 ± 4.2°N implies 2900 ± 600 km subsequent latitudinal convergence between India and Asia divided into 1100 ± 500 km within Asia and 1800 ± 700 km within India. [ABSTRACT FROM AUTHOR]

Shear wave splitting parameters (fast polarization directions and splitting times) obtained at the permanent broad-band station Wushi (WUS), which is situated in central Tien Shan, China, demonstrate systematic azimuthal variations. The fast polarization directions range from 26° to 85° and the delay times range from 0.4 to 1.6 s, suggesting a complex anisotropic structure that cannot be adequately explained by a single anisotropic layer with horizontal axis of symmetry. The azimuthal variations have an apparent 90° periodicity and thus can be best explained by a two-layer anisotropic model with horizontal symmetry axes. The optimal fast direction for the upper layer is in the 60°–80° range that is subparallel to the strike of the Tien Shan orogenic belt, and can consequently be attributed to the ongoing N–S directed shortening. The fast direction for the lower layer ranges from 85° to 105° and can be explained by lattice-preferred orientation of olivine crystals in the asthenosphere associated with present-day absolute plate motion of the Eurasian plate. [ABSTRACT FROM AUTHOR]