Toroidal Mantle Flow Induced by Slab Subduction and Rollback Beneath the Eastern Himalayan Syntaxis and Adjacent Areas

Liu, Lin; Gao, Stephen S.; Liu, Kelly H.; Li, Sanzhong; Tong, Siyou; Kong, Fande

doi:10.1029/2019gl084961

Cited by 30 publications

(23 citation statements)

References 79 publications

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“…The geometries of slabs subducting into the mantle beneath Asia, including intracontinental subduction in northern Tibet (Zhao et al, 2011), and the continued northward migration of India into Asia are responsible for the flow of sub‐Tibetan asthenosphere toward the Burmese microplate (e.g., Jolivet et al, 2018). This mantle flow model is supported by the results of azimuthal anisotropy inferred from SKS splitting results (Figure 1; Kind & Yuan, 2010; Liu et al, 2019; Wang et al, 2008).…”

Section: Discussionsupporting

confidence: 66%

“…Crust and mantle kinematics are thought to be decoupled at ~26°N (Figure 1), where orientations of mantle flow suddenly change from N‐S to W‐E (Figure 1; Kind & Yuan, 2010; Liu et al, 2019; Wang et al, 2008). This flow in the mantle would push the SE Tibetan asthenosphere across the inactive branches of the Sagaing Fault and approach northern Myanmar (Figures 1 and 2).…”

Section: Discussionmentioning

confidence: 99%

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Quaternary Volcanism in Myanmar: A Record of Indian Slab Tearing in a Transition Zone From Oceanic to Continental Subduction

Zhang

Ding

et al. 2020

Geochem Geophys Geosyst

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Magmatic processes that occur during the transition from oceanic to continental subduction and collision in orogens are critical and still poorly resolved. Oceanic slab detachment in particular is hypothesized to mark a fundamental change in magmatism and deformation within an orogen. Here, we report on two Quaternary volcanic centers of Myanmar that may help us better understand the process of slab detachment. The Monywa volcanic rocks are composed of low‐K tholeiitic, medium‐K calk‐alkaline, and high‐K to shoshonitic basalts with arc signatures, while the Singu volcanic rocks show geochemical characteristics similar to asthenosphere‐derived magmas. These volcanic rocks have low Os concentrations but extremely high 187Os/186Osi ratios (0.1498 to 0.3824) due to minor (<4%) crustal contamination. The Monywa arc‐like rocks were generated by small degrees of partial melting of subduction‐modified asthenospheric mantle at variable depths from the spinel to garnet stability fields. Distinct from the Monywa arc‐like rocks (87Sr/86Sri = 0.7043 to 0.7047; εNdi = +2.3 to +4.7), the Singu OIB‐like rocks exhibit higher 87Sr/86Sri (0.7056 to 0.7064) and lower εNdi (+0.8 to +1.6) values. These isotopic characteristics indicate a large contribution of an isotopically enriched asthenosphere layer beneath the Burmese microplate, which possibly flowed from SE Tibet. We interpret that this short‐lived, small‐scale, and low‐degree melting Quaternary volcanism in Myanmar was triggered by its position above a slab window resulting from the tearing of the oceanic lithosphere from buoyant continental lithosphere of the Indian plate.

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Section: Discussionsupporting

confidence: 66%

Section: Discussionmentioning

confidence: 99%

Quaternary Volcanism in Myanmar: A Record of Indian Slab Tearing in a Transition Zone From Oceanic to Continental Subduction

Zhang

Ding

et al. 2020

Geochem Geophys Geosyst

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“…Thus, the lower‐layer anisotropy revealed beneath the central Malay Peninsula can possibly be attributed to the toroidal flow induced by the tear of the subducted Indo‐Australian slab. A similar model associated with the Indian slab tear (L. Liu, Gao, et al., 2019) and the big mantle wedge (Lei & Zhao, 2016; Lei et al., 2009, 2019) is also proposed to explain the circular fast orientations observed in the eastern Himalayan syntaxis and the trench‐perpendicular fast orientations in the eastern Tibet toward the Burma arc. The revealed two‐layered anisotropy is also consistent with that from 3D body‐wave anisotropy tomography (Huang et al., 2015).…”

Section: Discussionmentioning

confidence: 83%

Seismic Anisotropy and Mantle Deformation Beneath the Central Sunda Plate

Song

Gao

et al. 2021

JGR Solid Earth

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The central Sunda plate, which forms the core of Southeast Asia, has been extensively studied based on analyses of data mainly from surface geological observations. In contrast, largely due to the limited coverage by seismic stations in the area, a number of key issues associated with mantle structure and dynamics remain enigmatic. These can possibly be constrained by investigating seismic azimuthal anisotropy in the upper mantle. Here we employ the shear wave splitting technique on three P‐to‐S converted phases from the core‐mantle boundary (PKS, SKKS, and SKS) recorded by 11 stations to systematically explore the spatial variation of azimuthal anisotropy beneath the central Sunda plate. Most of the Malay Peninsula is revealed to possess mostly trench‐perpendicular fast orientations that can be attributed to mantle flow induced by the Indo‐Australian subduction. In addition, the central part of the Malay Peninsula is characterized by a 2‐layered model of anisotropy, which is possibly associated with the joint effects of lithospheric fabrics and a slab tear‐induced toroidal flow. Absolute plate motion (APM)‐parallel anisotropy is observed in northern Borneo and the Nansha Block, where APM‐driven simple shear in the transitional layer between the partially coupled lithosphere and asthenosphere is mostly responsible for the observed anisotropy. The APM‐induced flow may be locally modified by a fossil slab segment beneath Sabah.

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“…Results of previous XKS splitting measurements (mainly downloaded from SWS-DBs Shear-wave splitting databases [IRIS DMC, https://doi. org/10.17611/DP/SWS.1;Wüstefeld et al, 2009], and additionally supplemented from L Liu et al, 2019). are plotted as dark-green bars, which are aligned with polarization φ of the fast wave and scaled by delay time δt.…”

mentioning

confidence: 99%

Lateral Seismic Anisotropy Variations Record Interaction Between Tibetan Mantle Flow and Plume‐Strengthened Yangtze Craton

Chen

Liang

et al. 2021

JGR Solid Earth

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The southeastern Tibetan Plateau experienced intense Cenozoic shortening and extrusion along the western Yangtze Craton, SW China, where the Permian Emeishan flood basalts were emplaced. Seismic anisotropy along a dense E–W‐trending linear seismic array across the west Yunnan is determined by shear‐wave splitting analysis to characterize the deformation associated with these processes. Interestingly, a strong N–S‐oriented anisotropic zone collocated with the Eocene–Oligocene potassic magmatism is observed between two weak anisotropic zones in the Three‐River Orogenic Zone and the western Yangtze Craton, respectively. The lateral anisotropy variation and distinct upper mantle structures collectively suggest that the western most Yangtze Craton, strengthened by the Permian mantle plume, acted as a rigid barrier to divert the Cenozoic Tibetan mantle flow into the Three‐River Orogenic Zone. Consequently, the western edge of the Yangtze Craton has been partially eroded and its anisotropic orientation was realigned to the direction of the mantle flow. This observation indicates that both the remodeled anisotropy in the lithosphere and the dynamic flow in the asthenosphere contribute to the mantle anisotropy at the lateral lithosphere‐asthenosphere transition, which is usually hard to seismologically resolve from the vertical lithosphere‐asthenosphere boundary.

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Toroidal Mantle Flow Induced by Slab Subduction and Rollback Beneath the Eastern Himalayan Syntaxis and Adjacent Areas

Cited by 30 publications

References 79 publications

Quaternary Volcanism in Myanmar: A Record of Indian Slab Tearing in a Transition Zone From Oceanic to Continental Subduction

Quaternary Volcanism in Myanmar: A Record of Indian Slab Tearing in a Transition Zone From Oceanic to Continental Subduction

Seismic Anisotropy and Mantle Deformation Beneath the Central Sunda Plate

Lateral Seismic Anisotropy Variations Record Interaction Between Tibetan Mantle Flow and Plume‐Strengthened Yangtze Craton

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