Intra-continental transpression and gneiss doming in an obliquely convergent regime in SE Asia

• Published in: Journal of structural geology 2017-04, Vol.97, p.48-70
• Main Authors: Zhang, Bo, Chai, Zhi, Yin, Cong Yuan, Huang, Wen Tao, Wang, Yang, Zhang, Jin Jiang, Wang, Xiao Xian, Cao, Kai
• Format: Article
• Language: English
• Subjects: Cenozoic; Dome; Oblique collision; Strike-slip shear zone; Tengchong; Transpression
• ISSN: 0191-8141; 1873-1201
• DOI: 10.1016/j.jsg.2017.02.010

The Tengchong terrane comprises a sequence of linear dome-like zones, cored by granite and migmatitic layers. These cores are mantled by predominantly gneiss and subordinate schist sequences, decreasing in deformation intensity outward from extensive mylonitization to weak mylonitization. The pre-doming deformation was characterized by the formation of large-scale top-to-the-east shearing (D1) in the gneiss terrane, locally preserved flat-lying foliation (S1), weak folding (F1) and emplacement of the Mangbang granite during the Cretaceous (114-104 Ma). The second stage of deformation (D2) consisted of map-scale east-verging folds (F2, dome amplification) and minor lateral strike-slip shear zones between the anticlines in the gneiss and migmatitic sequences. Extensive partial melting and emplacement of 67-30 Ma synkinematic granitoid bodies/veins occurred, leading to the emplacement of wedges of granite into the easterly directed F2 fold cores. These wedges formed kilometer-scale granitoid domes. The post-doming D3 deformation with transpression recorded strain partitioning with simple shear-dominated high-strain zones along the Gaoligong and Nabang dextral lateral strike-slip shear zones (active during 30-11 Ma). Late transtensional deformation (D4) during cooling of the entire terrane involved the localized low-temperature Gaoligong west and east detachment faults that controlled the late exhumation of the Gaoligong metamorphic zone (since 10 Ma). Our structural observations, combined with previous studies, suggest that this style of doming is a representative type of intra-continental deformation in the Cenozoic during the oblique India-Asia collision. The actual dome shapes reflect formation of antiforms during compression-dominated transpression, prior to localized strike-slip shearing, in the accommodation belt around the Eastern Himalayan Syntaxis. Vertical exhumation of crustal material by contractional doming played an important role in absorbing the vast majority of the internal deformation of crustal fragments during oblique collision. [Display omitted] •A compressive dome zone in the Tengchong terrane played a role for Intra-continental evolution.•Cenozoic doming formed in a transpression during dual collision of the Baoshan and Indian Plates.•Doming-related deformation of migmatites and syn-kinematic granite occurred with solid–state rheology.•The domes formed as antiforms prior to strike-slip shearing around the Eastern Himalayan Syntaxis.•The