Middle-Miocene transformation of tectonic regime in the Himalayan orogen

Abstract

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.

Phylogenetic and morphological analysis of Gloydius himalayanus (Serpentes, Viperidae, Crotalinae), with the description of a new species

“…At this time, the Qinghai-Xizang plateau had begun to uplift, and the rate of uplift increased in the late Miocene (Copeland et al 1987). The Himalayan orogen also changed from a North-South extension to a North-South contraction during the mid-Miocene (Wang et al 2013).…”

The Mabja Dome Structure in Southern Tibet Revealed by Deep Seismic Reflection Data and Its Tectonic Implications

“…Eclogitic‐facies rocks (Austrheim & Griffin, 1985; Fountain et al., 1994; Kern et al., 1999) would be consistent with the observations. Wang and Zhang (2015) documented granulite and eclogite‐facies rocks in selected Himalayan gneiss domes, which were originated from Indian plate thrusting beneath the Asian continent followed by exhumation during doming to the surface (Cottle et al., 2009; Jessup et al., 2008; Wang et al., 2013; J. Zhang et al., 2012). However, mafic rocks in the form of dikes, sills, or relatively thick mafic intrusions cannot be ruled out as a cause of both the high bulk velocities and high amplitude reflections (Cook et al., 1999; Simancas et al., 2003).…”

“…Eclogitic-facies rocks (Austrheim & Griffin, 1985;Fountain et al, 1994;Kern et al, 1999) would be consistent with the observations. Wang and Zhang (2015) documented granulite and eclogite-facies rocks in selected Himalayan gneiss domes, which were originated from Indian plate thrusting beneath the Asian continent followed by exhumation during doming to the surface (Cottle et al, 2009;Jessup et al, 2008;Wang et al, 2013;J. Zhang et al, 2012).…”

In-situ boron isotope and chemical composition of tourmaline in the Gyirong pegmatite, southern Tibet: Implications for petrogenesis and magma source

“…Leucogranites occurring as sills, dikes, dykes, dendritic and lenticular shapes intruded into the metamorphic rocks within the GHC. These leucogranitic veins were emplaced at 22-16 Ma (Wang et al, 2013;Gao et al, 2016), which record a long duration of anatexis and a tectonic transformation.…”