Emplacement and cooling of the Dien Bien Phu granitic complex: Implications for the tectonic evolution of the Dien Bien Phu Fault (Truong Son Belt, NW Vietnam)



Title: Emplacement and cooling of the Dien Bien Phu granitic complex: Implications for the tectonic evolution of the Dien Bien Phu Fault (Truong Son Belt, NW Vietnam)
Authors: Roger, Françoise;
Jolivet, Marc;
Maluski, Henri;
Respaut, Jean-Patrick;
Münch, Philippe
Paquette, Jean-Louis
Vu, Van Tich
Nguyen, Van
Keywords: Dien Bien Phu Fault
Indosinian orogeny
Late Cretaceous event
Paleo-Pacific subduction
Paleotethys
Issue Date: 2014
Publisher: Gondwana Research
Citation: Scopus
Abstract: The Dien Bien Phu (DBP) Fault strikes nearly perpendicular to the general tectonic framework, separating northwest Vietnam into two compartments. The DBP and Muong Lay granites are exposed respectively east and west of the fault. The U/Pb age of 277±2Ma obtained for the Muong Lay granite is similar to the age of the Chieng Khuong complex exposed within the Song Ma structure east of the DBP Fault. These two magmatic intrusions are considered as belonging to a same tectonic structure related to the subduction of the Song Ma Ocean under the Indochina Block during the Indosinian orogeny. The DBP Fault with a total post Permian dextral offset of 30-40km shifts the Song Ma Suture. It could then be connected to the Ailao Shan-Shuanggou suture to the north. The undeformed DBP granite gave a U/Pb age of 230±1Ma sealing the Indosinian deformation on the fault. The Ladinian-Carnian activity of the fault is confirmed by the 40Ar/39Ar (biotite) age of 228±4Ma obtained from the paragneiss forming the fault zone. A geodynamic model is proposed to describe the various tectonic phases recorded by on the DBP Fault. It associates field data, stratigraphic observations, and geochronology analyses (U/Pb, Ar/Ar, fission tracks). Following the Late Triassic exhumation of the granite and the end of the Indosinian orogeny marked by the Norian unconformity, the granite was buried under Jurassic and Lower Cretaceous sediments. A strong cooling event during the early Late Cretaceous (100Ma) is associated with the reactivation of the DBP Fault and the accommodation of a southward thrusting of the Song Da terrane onto the Truong Son Belt. This newly recognised tectonic phase could be associated to the subduction of the Paleo-Pacific plate under the Indochina Block. No data are available yet to constrain the Tertiary evolution of the DBP system. However, the Tertiary deformation is likely similar to the Cretaceous one
Description: Gondwana Research, Volume 26, Issue 2, September 2014, Pages 785-801
Gondwana Research
URI: http://www.sciencedirect.com/science/article/pii/S1342937X13002670
http://repository.vnu.edu.vn/handle/VNU_123/34086
ISSN: 1342937X
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