Middle Jurassic syn-kinematic magmatism, anatexis and metamorphism in the Zheduo-Gonggar massif, implication for the deformation of the Xianshuihe fault zone, East Tibet

• Mid-Jurassic magmatism and high-temperature metamorphism along the XSH fault.
• Mid-Jurassic sinistral strike-slip shearing along the XSH fault.
• Episodic magma emplacement of the granitic massif from 216 Ma to 10 Ma.

The Xianshuihe fault (XSHF) zone is an important lithospheric structure in east Tibetan Plateau. The Zheduo-Gonggar massif, about 120 km long and 13–18 km wide, developed along its eastern segment. Based on geological mapping, meso- and micro-structure studying and geochronology testing, the massif is divided into 5 units: (1) Intrusions of 216–204 Ma, (2) Intrusions of ∼170 Ma, (3) mid-Jurassic sillmanite-grade metasediments, (4) Oligo-Miocene migmatite zone, (5) Intrusions less than 20 Ma ago. Intrusions of 216–204 Ma related to the Songpan–Garze folding and distributes on the southern segment of the massif. The middle Jurassic intrusions which were found for the first time in the region, includes the syn-kinematic Zheduoshan granite and a suit of leucogranite. The former constrained by the youngest U–Pb age of 171 Ma which provides a minimum shear age of the XSH fault. The latter, U–Pb age of 170 Ma, is a common feature of convergent orogens or intracontinental subduction. The Oligo-Miocene migmatite zone, about 80 km long and 1–3 km wide, developed on the eastern edge of the massif. Intrusions less than 20 Ma ago is located on the northern segment of the massif. It had been widely researched that the latter two units are associated to the Cenozoic deformation of the XSH fault. While the mid-Jurassic syn-kinematic magmatism, anatexis and metamorphism along the XSH fault suggests a more strong Mesozoic tectono-thermal event in the fault zone. The discoveries provide us with a new perspective on understanding the Mesozoic and Cenozoic deformation of the XSH fault zone, southeastern Tibet.