Le métamorphisme Tardi-Crétacé à Éocène des zones internes de la chaı̂ne Indo-Birmane (Myanmar occidental) : implications géodynamiques

Abstract

Abstract – Late Cretaceous to Eocene metamorphism of the internal zone of the Indo-Burma range (westernMyanmar): geodynamic implications. Metamorphic study on Triassic schists in the internal zone of the Indo-Burma range,essentially based on chlorite–mica equilibrium in metapelites, allows a P – T path to be quantified. During the progrademetamorphism, the geothermic gradient evolves from that of a ‘normal’ crust (30 ◦ Ckm −1 ) to that of a thickened crust(18 ◦ Ckm −1 ). The peak conditions are around 8 kbar and 450 ◦ C. This thickening (25–30 km) is probably made in a wedgeset up between the Late Cretaceous and the Eocene, in front of the obduction. The obtained cold retrograde path requires amechanism allowing thermal re-equilibration, implying slow exhumation. It occurred along a shear zone that put into contactthe micaschists of the core with the Triassic schists of the roof. To cite this article: A. Socquet et al., C. R. Geoscience 0(2002) 1–8.  2002 Academie des sciences / Editions scientifiques et medicales Elsevier SAS