Exhumation of the crustal-scale Gaoligong strike-slip shear belt in SE Asia

The lateral extrusion of blocks is a well-known geological process during continent-continent collision and is always expressed by either brittle strike-slip faults or ductile shear zones. However, the vertical motion along such fault systems remains poorly constrained. The Gaoligong shear zone formed the western boundary of the Indochina block during India-Eurasia collision, resulting in the exhumation of deep crustal rocks, including a large volume of syn-tectonic granites. Combined zircon U-Pb dating and 40Ar/39Ar thermochronology show that both the unfoliated and foliated granitic intrusions were emplaced during the Early Cretaceous (125-112 Ma), post-magmatic melting occurred from the Early Oligocene (c. 35 Ma) and subsequent cooling took place during the Mid-Miocene (c. 13 Ma). The average emplacement depth of Early Cretaceous samples showed that at least 15 km of the hanging wall of the Gaoligong shear zone must have been removed by vertical motion during shearing. Syn-shearing exhumation underlines the role of the initiation of lateral motion of the shear zone by magma-assisted rheological weakening and exhumation at high ambient temperatures within the shear zone. A new model links magmatic channel flow underneath the Tibetan Plateau with magma intrusions and the high geothermal gradients along the shear belts such as the Gaoligong shear zone. Supplementary material: Methods, electron probe microanalysis test results and zircon laser ablation inductively coupled plasma mass spectrometry U-Pb results are available at