New insights into the collision process of India and Eurasia: Evidence from the syntectonic-sedimentation-induced inclinational divergence of Cretaceous paleomagnetic data of the Lhasa Terrane

Unidentified Cretaceous syntectonic growth strata in the Lhasa Terrane (LT) has resulted in inclinations calculated from the paleomagnetic data from the southern limb of folds being substantially higher than those from the northern limb. This causes conspicuous inclinational divergences in the Cretaceous paleomagnetic data obtained from the LT, and results in cluttered restoring of the Cretaceous paleolatitude of the southern margin of Eurasia, contradictory constraining of the collision process of India and Eurasia, and imprecise estimation of the post-collision crustal convergence within southern Eurasia. After applying a new syntectonic-sedimentation-correction, the inclinational divergences of the Cretaceous paleomagnetic data within the LT are effectively eliminated. The Cretaceous inclinations of the western part of the LT are found to converge within the range of 30.1°–30.7°, indicating that the western part of the LT was situated at the paleolatitude of 16.9 ± 1.3°N during the Cretaceous. Nevertheless, the syntectonic-sedimentation-correction for the Cretaceous paleomagnetic data from the central-eastern parts of the LT show alternative Cretaceous paleolatitudes of 17.4 ± 1.3°N or 12.9 ± 1.6°N, because of lacking paleomagnetic sampling sections across the two limbs of folds. When considering the western, central and eastern parts of the LT were consistently situated at the paleolatitude of ~17°N, the LT had an approximate E-W extended banded shape in the entire Cretaceous. This interpretation supports the diachronous collision process of India and Eurasia, in which the collision first occurred at the western end of the LT, and subsequently the counterclockwise rotation of India closed the Neo-Tethys Ocean from the west to the east. On the other hand, the central part of the LT was situated at the paleolatitude of 12.9 ± 1.6°N, resulting in a shape of inverted triangle of the LT during the interval of the Cretaceous. This suggested that the India probably had collided with the LT quasi-synchronously at the western and central part of the Himalaya Terrane, and that the Neo-Tethys Ocean was closed simultaneously along the western and central segment of the Yarlung Zangbo suture zone. Subsequently, the Indian Plate began to experience counterclockwise rotation, approximately centered on the Western Himalaya syntaxis, which compressed the LT and resulted in non-uniform crustal convergence within the LT. The central part of the LT should experience larger amount of crustal convergence than that of the western part of the LT.