Penetration of mid-crustal low velocity zone across the Kunlun Fault in the NE Tibetan Plateau revealed by ambient noise tomography

Jiang, Chengxin; Yang, Yingjie; Zheng, Yong

doi:10.1016/j.epsl.2014.08.040

Cited by 80 publications

(66 citation statements)

References 55 publications

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“…7) throughout the mid-crust in most of Tibet has also been observed in a number of previous studies (e.g. Cotte et al 1999;Rapine et al 2003;Caldwell et al 2009;Guo et al 2009;Li et al 2009;Yang et al 2012;Agius & Lebedev 2014;Jiang et al 2014;Li et al 2014;Sun et al 2014;Bao et al 2015;Deng et al 2015;Gilligan et al 2015). Our results have high resolution across the entire Tibetan Plateau and the Pamirs, whereas many previous studies have mainly focused on more restricted geographical regions.…”

Section: P O S S I B L E C Au S E O F T H E L O W V E L O C I T Y L Amentioning

confidence: 42%

“…Various explanations have been put forward as to the cause of the mid-crustal low velocity zone including the presence of partial melt (Caldwell et al 2009;Hacker et al 2014;Jiang et al 2014), aqueous fluids (Caldwell et al 2009), anisotropy from the alignment of micas in the crust (Yang et al 2012;Hacker et al 2014) or some combination of these mechanisms (Agius & Lebedev 2014). These explanations imply that the mid-crust is mechanically weak (Klemperer 2006), providing support for the idea that deformation in Tibet occurs due to crustal flow (e.g.…”

Section: P O S S I B L E C Au S E O F T H E L O W V E L O C I T Y L Amentioning

confidence: 92%

“…Caldwell et al 2009;Hacker et al 2014;Jiang et al 2014) . Velocities less than 3.4 km s −1 , such as those observed throughout the Tibetan Plateau would be in agreement with the presence of melt from rocks of composition and temperatures that are plausible for Tibet (Hacker et al 2014).…”

Section: P O S S I B L E C Au S E O F T H E L O W V E L O C I T Y L Amentioning

confidence: 99%

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Lateral variations in the crustal structure of the Indo–Eurasian collision zone

Gilligan

2018

Geophysical Journal International

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S U M M A R YThe processes involved in continental collisions remain contested, yet knowledge of these processes is crucial to improving our understanding of how some of the most dramatic features on the Earth have formed. As the largest and highest orogenic plateau on the Earth today, Tibet is an excellent natural laboratory for investigating collisional processes. To understand the development of the Tibetan Plateau, we need to understand the crustal structure beneath both Tibet and the Indian Plate. Building on previous work, we measure new group velocity dispersion curves using data from regional earthquakes (4424 paths) and ambient noise data (5696 paths), and use these to obtain new fundamental mode Rayleigh wave group velocity maps for periods from 5 to 70 s for a region including Tibet, Pakistan and India. The dense path coverage at the shortest periods, due to the inclusion of ambient noise measurements, allows features of up to 100 km scale to be resolved in some areas of the collision zone, providing one of the highest resolution models of the crust and uppermost mantle across this region. We invert the Rayleigh wave group velocity maps for shear wave velocity structure to 120 km depth and construct a 3-D velocity model for the crust and uppermost mantle of the Indo-Eurasian collision zone. We use this 3-D model to map the lateral variations in the crust and in the nature of the crust-mantle transition (Moho) across the Indo-Eurasian collision zone. The Moho occurs at lower shear velocities below northeastern Tibet than it does beneath western and southern Tibet and below India. The east-west difference across Tibet is particularly apparent in the elevated velocities observed west of 84• E at depths exceeding 90 km. This suggests that Indian lithosphere underlies the whole of the Plateau in the west, but possibly not in the east. At depths of 20-40 km our crustal model shows the existence of a pervasive mid-crustal low velocity layer (∼10% decrease in velocity, V s < 3.4 km s −1 ) throughout all of Tibet, as well as beneath the Pamirs, but not below India. The thickness of this layer, the lowest velocity in the layer and the degree of velocity reduction vary across the region. Combining our Rayleigh wave observations with previously published Love wave dispersion measurements, we find that the low velocity layer has a radial anisotropic signature with V sh > V sv . The characteristics of the low velocity layer are supportive of deformation occurring through ductile flow in the mid-crust.

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Section: P O S S I B L E C Au S E O F T H E L O W V E L O C I T Y L Amentioning

confidence: 42%

Section: P O S S I B L E C Au S E O F T H E L O W V E L O C I T Y L Amentioning

confidence: 92%

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Lateral variations in the crustal structure of the Indo–Eurasian collision zone

Gilligan

2018

Geophysical Journal International

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“…Magnetotelluric observations found that a finger-like crustal melt penetrates north from the Songpan-Ganzi terrane and weakens the crust beneath the Kunlun Shan (Pape et al 2012). Ambient noise tomography by Li et al (2014) showed that the mid-to-lower crustal LVZ thinned out around the eastern Kunlun fault, while Jiang et al (2014) observed a weak crust in the Qinling Orogen facilitating the northeastern extrusion of the LVZs. Receiver functions near the Qaidam basin showed a south-dipping velocity discontinuity in the upper mantle, which is interpreted as the top of the subducting Eurasia mantle lithosphere (Kind et al 2002), however, Yue et al (2012) observed a slightly northward dipping Moho underneath the Qaidam basin.…”

Section: Introductionmentioning

confidence: 99%

“…Previous results of surface wave tomography and receiver functions suggest that the crust and mantle structure in the NET is very heterogeneous (e.g. Bao et al 2013;Jiang et al 2014;Li et al 2014). Magnetotelluric observations found that a finger-like crustal melt penetrates north from the Songpan-Ganzi terrane and weakens the crust beneath the Kunlun Shan (Pape et al 2012).…”

Section: Introductionmentioning

confidence: 99%

Crustal and upper mantle structure beneath the northeastern Tibetan Plateau from joint analysis of receiver functions and Rayleigh wave dispersions

Zheng

Shen

et al. 2015

Geophys. J. Int.

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Constraints on the evolution of crustal flow beneath Northern Tibet

Pape

Jones

Unsworth

et al. 2015

Geochem Geophys Geosyst

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Crustal flow is an important tectonic process active in continent‐continent collisions and which may be significant in the development of convergent plate boundaries. In this study, the results from multidimensional electrical conductivity modeling have been combined with laboratory studies of the rheology of partially molten rocks to characterize the rheological behavior of the middle‐to‐lower crust of both the Songpan‐Ganzi and Kunlun terranes in the northern Tibetan Plateau. Two different methods are adopted to develop constraints on melt fraction, temperature, and crustal flow velocity in the study area. The estimates of these parameters are then used to evaluate whether crustal flow can occur on the northern margin of the Tibetan plateau. In the Songpan‐Ganzi crust, all conditions are satisfied for topography‐driven channel flow to be dominant, with partial melt not being required for flow at temperature above 1000°C. Further north, the Kunlun fault defines the southern boundary of a transition zone between the Tibetan plateau and the Qaidam basin. Constrained by the estimated melt fractions, it is shown that channel injection across the fault requires temperatures close to 900°C. The composition of igneous rocks found at the surface confirm those conditions are met for the southern Kunlun ranges. To the north, the Qaidam basin is characterized by colder crust that may reflect an earlier stage in the channel injection process. In the study area, at least 10% of the eastward directed Tibetan crustal flow could be deflected northward across the Kunlun Fault and injected into the transition zone defining the northern margin of the Tibetan plateau.

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Penetration of mid-crustal low velocity zone across the Kunlun Fault in the NE Tibetan Plateau revealed by ambient noise tomography

Cited by 80 publications

References 55 publications

Lateral variations in the crustal structure of the Indo–Eurasian collision zone

Lateral variations in the crustal structure of the Indo–Eurasian collision zone

Crustal and upper mantle structure beneath the northeastern Tibetan Plateau from joint analysis of receiver functions and Rayleigh wave dispersions

Constraints on the evolution of crustal flow beneath Northern Tibet

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