The rocks of this
brittle-fault strand consist of amphibolite to granulite grade gneissic rocks. Structural analysis indicates
that the rocks in this area experienced three distinct episodes of deformation (D1–D3). The first (D1)
formed large-scale NW–SE-trending isoclinal folds (F1) that were reworked by small-scale tight to open
folds (F2) during the second deformation (D2). D1 and D2 resulted from NE–SW shortening during the Triassic
Indosinian orogeny before being cross-cut by leucogranites. D1 and D2 fabrics were then reworked
by D3 sinistral shearing, including shear planes (S3) and mineral stretching lineations (L3). LA–MC–ICP–
MS U–Pb zircon dating suggested that the leucogranite intrusion and the magmatic crystallization took
place at 78.6 ฑ 0.7 Ma followed by a second crystallization at 67 ฑ 1 to 72.1 ฑ 0.6 Ma. Both crystallizations
occurred in the Late Cretaceous and, it is suggested, were tectonically influenced by SE Asian region
effects of the West Burma and Shan-Thai/Sibumasu collision or development of an Andean-type margin.
The sinistral ductile movement of D3 was coeval with the peak metamorphism that occurred in the