Kinematics of the crust around the Ama Drime Massif (southern Tibet) – Constraints from paleomagnetic results

Secondary magnetic remanences are used to study late-orogenic rotation and tilting on a E–W transect in southern Tibet at ∼28.5°N. Sampling was performed on both sides of the Ama Drime Massif (ADM). Remanent magnetization resides in pyrrhotite formed during metamorphism and is related to the last cooling event through 325 °C (Curie temperature of pyrrhotite). The existence of antipodal pTRMs demonstrates that the ChRM is of thermoremanent origin and was acquired during cooling of the Tethyan metasediments. Penetrative deformation was still going on in Ronghbuk area until ca 250 °C, whereas it was already completed in Dinggye area. Significant departures from the expected field direction during the age of remanence acquisition cannot be interpreted by consistent vertical axis rotation of blocks. Antagonist deviations on both sides of the ADM are explained as tiltings around an horizontal axis striking ∼N20°. These tiltings are estimated to be younger than 13–12 Ma and they are related to the ADM exhumation initiated since 33 Ma.

► Pyrrhotite secondary remanence evidence block rotation in southern Tibet.
► Record of successive polarities during cooling of metasediments.
► Magnetization is of thermoremanent origin and was locally acquired during deformation.
► Uplift of the Ama Drime Massif is estimated of 15.5 ± 9.4 km since remanence acquisition.