Mantle transition zone discontinuities beneath the Indochina Peninsula: Implications for slab subduction and mantle upwelling

Yu, Youqiang; Gao, Stephen S.; Liu, Kelly H.; Yang, Ting; Xue, Mei; Le, Khanh Phon

doi:10.1002/2017gl073528

Cited by 38 publications

(41 citation statements)

References 48 publications

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“…Results from this study are consistent with the hypothesis that the upflow is capable of causing significant temperature anomalies in areas as deep as at least the upper MTZ. Thermal upwelling through a slab window has been proposed beneath some other areas such as the Indochina Peninsula (Yu et al, ) and SW China (Zhang et al, ) and is considered to be the upwelling component of a return flow system induced by sinking slab segments, as revealed by geodynamic modeling (Faccenna et al, ).…”

Section: Discussionmentioning

confidence: 99%

“…Numerous previous studies have demonstrated that the depth variations of the d 410 and d 660 can provide independent constraints on the depth extent of subducted cold slabs and high temperature anomalies (e.g., Anderson, ; Collier et al, ; Contenti et al, ; Li & Yuan, ; Liu et al, , ; Shearer & Masters, ; Wicks & Richards, ; Yu et al, ). The d 410 and d 660 are ubiquitous and well established in most global models and correspond to a globally averaged MTZ thickness of 250 km (Kennett & Engdahl, ; Kennett et al, ).…”

Section: Introductionmentioning

confidence: 99%

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Topography of the Mantle Transition Zone Discontinuities Beneath Alaska and Its Geodynamic Implications: Constraints From Receiver Function Stacking

et al. 2017

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The 410 and 660 km discontinuities (d410 and d660, respectively) beneath Alaska and adjacent areas are imaged by stacking 75,296 radial receiver functions recorded by 438 broadband seismic stations with up to 30 years of recording period. When the 1‐D IASP91 Earth model is used for moveout correction and time depth conversion, significant and spatially systematic variations in the apparent depths of the d410 and d660 are observed. The mean apparent depth of the d410 and d660 for the entire study area is 417 ± 12 km and 665 ± 12 km, respectively, and the mean mantle transition zone (MTZ) thickness is 248 ± 8 km which is statistically identical to the global average. For most of the areas, the undulations of the apparent depths of the d410 and d660 are highly correlated, indicating that lateral velocity variations in the upper mantle above the d410 contribute to the bulk of the observed apparent depth variations by affecting the traveltimes of the P‐to‐S converted phases from both discontinuities. Beneath central Alaska, a broad zone with greater than normal MTZ thicknesses and shallower than normal d410 is imaged, implying that the subducting Pacific slab has reached the MTZ and is fragmented or significantly thickened. Within the proposed Northern Cordilleran slab window, an overall thinner than normal MTZ is observed and is most likely the result of a depressed d410. This observation, when combined with results from seismic tomography investigations, may indicate advective thermal upwelling from the upper MTZ through the slab window.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Topography of the Mantle Transition Zone Discontinuities Beneath Alaska and Its Geodynamic Implications: Constraints From Receiver Function Stacking

et al. 2017

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“…In d o c h in a P e n in s u la Sl ab R ol lb ac k Figure 10. A schematic cartoon showing the formation mechanisms of the observed seismic anisotropy beneath the Indochina Peninsula generated based on our observations and previous studies (Li et al, 2008;Pesicek et al, 2008;Yu et al, 2017b).…”

Section: Mantle Upwellingmentioning

confidence: 94%

“…While seismic tomography (e.g., Bijwaard et al, 1998;Li et al, 2008;Pesicek et al, 2008) and receiver function studies (Yu et al, 2017b) have demonstrated that the Indian slab has reached the mantle transition zone (MTZ), the key issue of whether the subduction is still active remains debated. A recent focal Geochemistry, Geophysics, Geosystems 10.1029/2018GC007474 mechanism study reveals that the P axis of earthquakes in the Benioff zone beneath the Burma Block has a predominantly NNE direction, which is similar to the direction of relative plate motion between the Indian and Eurasian plates, and argues against active subduction (Rao & Kumar, 1999).…”

Section: 1029/2018gc007474mentioning

confidence: 99%

Characteristics of the Mantle Flow System Beneath the Indochina Peninsula Revealed by Teleseismic Shear Wave Splitting Analysis

Gao

Liu

et al. 2018

Geochem Geophys Geosyst

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Numerous geoscientific investigations have been conducted on the southeastern Tibetan Plateau and adjacent areas for understanding crustal and mantle deformation associated with the indentation of the Indian Plate into Eurasia. A number of key issues, such as the causes of a sudden change of fast polarization orientations from N‐S to almost E‐W at approximately 26°N revealed by shear wave splitting (SWS) studies, and the geodynamic implications of the transition still remain enigmatic, partially due to the lack of sufficient SWS measurements on the Indochina Peninsula. Here we employ the SWS technique to systematically illuminate upper mantle anisotropy beneath the Indochina Peninsula with an unprecedented data coverage. The resulting 409 SWS measurements from 29 stations show that upper mantle anisotropy beneath the vast majority of the study area is characterized by dominantly E‐W fast orientations which are nearly orthogonal to the strike of most of the major tectonic features in the study area, ruling out significant lithospheric contributions to the observed anisotropy. This observation, when combined with results from seismic tomography, numerical modeling, surface movement, and focal mechanism investigations, suggests that the observed azimuthal anisotropy is mostly the consequence of absolute plate motion or the westward rollback of the oceanic Indian slab. The flow system induced by the rollback or absolute plate motion may experience regional alteration from mantle upwelling along the eastern edge of the slab and through a previously detected slab window, leading to local variations in the observed splitting parameters.

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“…Wang et al (2015) showed that late Cenozoic continental flood basalts, which originated directly above the edge of the Pacific stagnant slab beneath China, could be accounted for by subducted fluids triggering wet melting. Yu et al (2017) also provided evidence from seismic tomography for similar events beneath Southeast Asia.…”

Section: Big Wedges and Inward-facing Subductionmentioning

confidence: 88%

Komatiites From Mantle Transition Zone Plumes

Wyman

2020

Front. Earth Sci.

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During the Archean, episodic volcanism commonly included both plume-and arctype magmatism, raising the issue of a possible link between "bottom up" and "top down" geodynamic processes. Rather than plume-initiated subduction, the bestpreserved cratons demonstrate that komatiitic magmatism postdated at least some of the subduction linked volcanism. Several factors suggest that komatiite-generating plumes were sourced in the mantle transition zone. Komatiites contain 0.6 wt.% or more H 2 O, which is contrary to earlier predictions for plume ascent through the transition zone. Geodynamic reconstructions indicate that multiple subducted slabs penetrated the transition zone in the region of future plume ascent and the related trench configurations limit the size of any associated plume heads. The implied plume head sizes are inconsistent with those required for a plume to ascend from the core-mantle boundary but match those predicted for plumes sourced from the lower transition zone. Transition zone plumes have mainly been advocated for in post-Archean "big wedge" scenarios involving subducted slabs that stall at the base of the transition zone but they are also an outcome of the "basalt barrier" featured in some geodynamic models for the Archean and early Proterozoic. The latter models suggest the basaltic components of Archean subducted slabs were too buoyant to descend into the lower mantle and formed a boundary layer that isolated the upper mantle and lower mantle on the early Earth, except in times of mantle overturns. The basalt barrier was a significant thermal boundary layer that, in principle, could act as the nucleation site of upwelling plumes anywhere on the globe. The evidence discussed here, however, suggests that the mainly peridotitic mantle upwellings were enhanced by the nearby injection of closely associated slabs into the transition zone. The simplicity of the Mantle Transition Zone (MTZ) plume-forming mechanism ensured that komatiites could be generated throughout the Archean even as Earth moved toward a regime involving modernstyle subduction, globe-encompassing oceanic ridge systems and tectonic plates. The distinctive geodynamic setting of Gorgona Island produced relatively low-temperature komatiites at the only place along the margin of North and South America where it was possible to reproduce the bowl-like subduction configurations commonly associated with their Archean and Paleoproterozoic counter parts.

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Mantle transition zone discontinuities beneath the Indochina Peninsula: Implications for slab subduction and mantle upwelling

Cited by 38 publications

References 48 publications

Topography of the Mantle Transition Zone Discontinuities Beneath Alaska and Its Geodynamic Implications: Constraints From Receiver Function Stacking

Topography of the Mantle Transition Zone Discontinuities Beneath Alaska and Its Geodynamic Implications: Constraints From Receiver Function Stacking

Characteristics of the Mantle Flow System Beneath the Indochina Peninsula Revealed by Teleseismic Shear Wave Splitting Analysis

Komatiites From Mantle Transition Zone Plumes

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