A large Oligocene-Miocene extensional gneiss dome in Vietnam has implications for the kinematics of the Ailao Shan-Red River shear zone and rifting of the South China Sea. A major northeast-dipping extensional shear zone separates the Bu Khang dome from less-metamorphosed units above. Shearing deformation occurred during the exhumation of high-pressure rocks. ⁴⁰Ar-³⁹Ar ages on micas reveal Oligocene-Miocene ages, from 36 to 21 Ma. After a high-pressure episode of probable Oligocene age, the area was subjected to northeast-southwest extension during the opening of the South China Sea. A kinematic model involving left-lateral shear and block rotation within a north-south dextral shear zone integrates our observations in the Bu Khang dome with South China Sea rifting.

Jolivet L., Maluski H., Beyssac O., Goffe B., Lepvrier C., Thi P.T., Van Vuong N.

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Từ khóa : geodynamics; gneiss; kinematics; rifting; shear zone; Tertiary; South China Sea