Middle-Miocene transformation of tectonic regime in the Himalayan orogen

• Published in: Chinese science bulletin Vol. 58; no. 1; pp. 108 - 117
• Main Authors: Wang, XiaoXian, Zhang, JinJiang, Liu, Jiang, Yan, ShuYu, Wang, JiaMin
• Format: Journal Article
• Language: English
• Published: Heidelberg Springer-Verlag 2013; SP Science China Press
• Subjects: Chemistry/Food Science; deformation; Earth Sciences; Engineering; geology; Humanities and Social Sciences; LA-ICP-MS; Life Sciences; multidisciplinary; Physics; Science; Science (multidisciplinary); 中中新世; 喜马拉雅造山带; 收敛变形; 构造体制; 构造转换; 逆冲推覆; 造山运动; China; tectonic regime transformation; south Tibet detachment system (STDS); Gyirong area; north-south trending rift (NSTR); Himalayan orogen; leucogranitic vein
• ISSN: 1001-6538; 1861-9541
• DOI: 10.1007/s11434-012-5414-6

Understanding the multiple tectonic transformations during the Himalayan orogeny is significant in evaluating the evolution of Himalayan orogen. In the Gyirong area in south Tibet, deformed leucogranitic veins in the biotite-plagioclase gneisses of Greater Himalayan crystalline complex (GHC) constitute south-vergent asymmetric folds. The reconstruction of the veins shows that they experienced two generations of deformation under different tectonic regimes: an earlier top-to-north extension and a later top-to-south thrusting, implying a tectonic transformation from N-S extension to N-S shortening. Zircons LA-ICP-MS U-Pb dating of the leucogranite shows that it was emplaced during 21.03-18.7 Ma. The data suggest that the tectonic transformation occurred after 18.7 Ma. The chronological data of South Tibet detachment system (STDS) and North-South trending rift (NSTR) from Gyirong and other areas indicate that the Himalayan orogeny was in a period of tectonic transformation from N-S extension to N-S shortening during 19-13 Ma. The transformation of tectonic regime was probably controlled by the India-Asia convergence rate. An increase in the convergence rate resulted in N-S shortening of the orogen, thrusting and folding, with coeval formation of the NSTR in Tibet. A decrease in the convergence rate led to N-S extension and reactivation of the STDS.