Abstract

The Southeastern portion of the Tam Kỳ - Phước Sơn Shear Zone, which locates along the coastal area of southern Quảng Nam - northern Quang Ngai provinces is a large-scale, highly strained, multiply derformed structure with 5 oeverprinting phases of deformation. The first deformational event (D₁) is created a kilomete-thick ultra-high deformational zone that is reprented by strong mylonitization of pre-Sliurian rocks that bounded the tectonic mélanges derived from ultramatic to felsic, intrusive and extrusive magmas or multi- original sedimentary rocks. Kinematic indicators indicate that this zone is a typical thrust structure formed by the plate-plate collision. The first generation structures were redeformed by second phase of deformation (D2), creating regionally norhtwest-southeast trending fold-thrust system. Above structures was deformed by the third deformational phase (D3), which led to the formation of northeast-southwest trending open folds and faults. All of these structures are partly fractured by brittle structures, which formed during the fourth (D4) and fifth (D5) deformaitons. The first deformation evenr was taken place during a plate collisional event in Ordovician-Silurrian time to form Proto-Indochina Block. The second defomation event directly related to the Indosinian Orogeny caused by the destruction of Paaleotethys and assembly of Subumasu Plate to Indochina. The third, fourth and fiftth deformational events were sucessively procuded by the accretion of Shan-Thai, West Burma, Luconia-Dangerous Ground plates to Sibumasu-Indochina and India to Euasia during Late Mesozoic-Cenozoic and is continued to recent.