Structural evolution of the Red River Shear zone, Yunnan (SW China) and North Vietnam.

M.P. Searle in collaboration with Sun-Lin Chung and Meng-Wang Yeh (National University of Taiwan, Taipei), J. Cottle (NIGL).

The NW-SE aligned Red River Fault is a major strike-slip fault that stretches for ~1000 km from the southeast corner of the Tibetan Plateau to the Gulf of Tonkin and South China Sea. It is commonly interpreted as a lithospheric-scale strike-slip that has accommodated 500-1000 km of southeastward extrusion of Indochina as a result of the indentation of India into Asia. Four metamorphic complexes have been exhumed along the Red River Fault, the Xuelong Shan, Diancang Shan, Ailao Shan in Yunnan and the DayNuiConVoi in North Vietnam. They each contain high-grade metamorphic rocks, and at least three types of granitic rocks: calc-alkaline granodiorites and orthogneisses, mantle-derived amphibole-quartz monzonites – syenites (eg: FanSiPan syenites in Vietnam), and crustal-melt leucogranites containing biotite with rare garnet and tourmaline. There is presently great debate whether the metamorphic rocks along the Red River shear zone were formed as a result of shear heating or were earlier, unrelated to strike-slip fault motion. This project is undertaking regional and local scale mapping both in Yunnan and in North Vietnam, combined with metamorphic petrology, thermobarometry and metamorphic modeling as well as U-Pb dating of metamorphic and magmatic rocks with the aim of unraveling the evolution of all the rocks exhumed along the Red River Fault.

Selected references: