Meso-Cenozoic Strain Evolution Along the Red River Shear Zone, Northern Vietnam

• Main Authors: She Pao-Chu, 佘寶珠
• Other Authors: Lee Tung-Yi
• Format: Others
• Language: en_US
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/53792663651906278396

碩士 === 國立臺灣師範大學 === 地球科學研究所 === 92 === ABSTRACT In order to study the strain evolution of the highly deformed Red River Shear Zone (RRSZ) in northern Vietnam, matrix Foliation Intersection/Inflection Axes (FIAs) were measured from the orientated thin sections sampled between Lao Cai and Nam Dinh along the RRSZ, northern Vietnam. Microstructural observation recorded three ductile deformation events in this region. D1, possibly occurred during the Indosinian orogeny, showed the sub-vertical S1, the dextral shearing S0/1, and sub-horizontal N-S trending FIA set 1, indicating E-W compressional σ1 . The orientations of FIA set 2 and 3 remained similar to FIA set 1 (N-S trending, sub-horizontal). D2 , possibly resulted from the left-lateral strike-slip movement of the RRSZ during Eocene-Miocene, formed the sub-horizontal S2 and sinistral shearing S1, and indicated σ1 in the vertical direction and E-W compressional σ2 . σ1 changed to E-W compression during D3 , and formed the sub-vertical S3 and the dextral shearing S2 as the right-lateral strike-slip movement of RRSZ, which possibly commenced during the Late Miocene. These results correlate well with the regional tectonic framework of the Indochina. The stress patterns didn’t change along the RRSZ as predicted by the left-lateral strike-slip movement of the RRSZ of the Zipper Tectonic Model Reference. The observed stress evolutionary history since the Cenozoic is different from previous studies, e.g. Huchon et al. (1994) and Burchfiel (2004).