The ages and tectonic setting of the Zaxoi-Mamba ductile shear zone in the Gangdise orogenic belt, Xizang

The Zaxoi-Mamba ductile shear zone lies in the middle part of the Gangdise orogenic belt, and occurs as an overthrusted and right-lateral strike-slip oblique ductile shear zone. The tectonites in this zone include tectonic gneiss and mylonite. The biotite from the granitic mylonite gives a ⁴⁰Ar/³⁹Ar age of 105.2 ±1.7 Ma, implying that the ductile shear zone may be traced back to the Early Cretaceous. The petrological associations and microstructures have disclosed that the ductile shear zone was formed in the medium to high greenschist facies conditions, and may be associated with the closure and collision of the Bangong Lake-Nujiang back-arc oceanic basin.