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

Posted on 01.09.2021 - 12:20
Lateral extrusion of blocks is a well-known geological process during continent-continent collision, which always expresses by either brittle strike-slip faults or ductile shear zones. However, vertical motion along such fault systems remains poorly constrained. The Gaoligong shear zone (GLG–SZ) formed the western boundary of the Indochina block during the India–Eurasia collision, resulting in the exhumation of deep crustal rocks, including a large volume of syntectonic granites. Combined zircon U–Pb dating and 40Ar/39Ar thermochronology revealed that both the unfoliated and foliated granitic intrusions were emplaced during the Early Cretaceous (112–125 Ma), post-magmatic melting occurred from the Early Oligocene (c. 35 Ma), and subsequent cooling during the Middle Miocene (c. 13 Ma). The average emplacement depth of Early Cretaceous samples revealed that at least 15 km of hangingwall of the GLG–SZ must have been removed by vertical motion during shearing. Syn-shearing exhumation underlines the role of the lateral motion of the shear zone initiation 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 GLG–SZ.

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Dong, Yanlong; Cao, Shuyun; Neubauer, Franz; Wang, Haobo; Li, Wenyuan; Genser, Johann (2021): Exhumation of the crustal-scale Gaoligong strike-slip shear belt in Southeast Asia. Geological Society of London. Collection. https://doi.org/10.6084/m9.figshare.c.5598365.v1
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