Shear wave splitting and shear wave splitting tomography of the southern Puna plateau

Calixto, Frank J.; Robinson, Danielle D.; Sandvol, Eric; Kay, Suzanne Mahlburg; Abt, D. L.; Fischer, K. M.; Heit, B.; Yuan, Xiaohui; Comte, D.; Alvarado, Patricia

doi:10.1093/gji/ggu296

Cited by 11 publications

(22 citation statements)

References 53 publications

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“…A similar conclusion is made by Calixto et al [2014] in the southern Puna region directly to the north of the flat slab. They instead suggest that trench-parallel to subparallel flow dominates beneath the subducting Nazca slab.…”

Section: Introductionsupporting

confidence: 81%

“…While Calixto et al [2014] are able to deduce trench-parallel subslab anisotropy in the southernmost portion of their study region, the complex splitting they observe suggests multiple layers of anisotropy beneath their stations. The most probable sources of the anisotropic layers are the subslab mantle and the mantle wedge [e.g., Abt et al, 2009;Long and Wirth, 2013;Calixto et al, 2014]. With the presence of a continuous slab, dynamics in the mantle wedge and subslab mantle can operate separately, thereby developing distinct patterns of flow and anisotropy leading to complex splitting orientations [e.g., Abt et al, 2010].…”

Section: 1002/2017gl074312mentioning

confidence: 89%

“…The Nazca plate-motion-parallel splitting is thus likely the result of plate driven mantle flow. The highly variable splitting seen by Calixto et al [2014] is exemplified by the lack of a trend in the rose diagram. This is strong supporting evidence for the assertion Anderson et al [2004] andMacDougall et al [2012].…”

Section: Discussionmentioning

confidence: 99%

“…We propose that the consistently oriented splits we observe result from mantle flow through the slab tear, which is responsible for connecting dynamics between the subslab mantle with the mantle wedge ( Figure 5). In the Calixto et al [2014] study region, no such cross-slab geodynamic mechanism exists leading to their observations of complex splitting. In the Calixto et al [2014] study region, no such cross-slab geodynamic mechanism exists leading to their observations of complex splitting.…”

Section: 1002/2017gl074312mentioning

confidence: 98%

“…Station map of our study area including those where previous splitting measurements were made (PUNA[Heit et al, 2007;Sandvol and Brown, 2007] byCalixto et al [2014] and CHARGE[Beck et al, 2000] byAnderson et al [2004] and MacDougall et al[2012]). The motion of the Nazca plate in the MORVEL No-Net-Rotation(NNR [DeMets et al, 2010]) and HS3 Nuvel-1A hot spot (HS3[Gripp and Gordon, 2002]) reference frames are shown by the black and red arrows, respectively.…”

mentioning

confidence: 99%

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Mantle flow through a tear in the Nazca slab inferred from shear wave splitting

Lynner

Anderson

Portner

et al. 2017

Geophysical Research Letters

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A tear in the subducting Nazca slab is located between the end of the Pampean flat slab and normally subducting oceanic lithosphere. Tomographic studies suggest mantle material flows through this opening. The best way to probe this hypothesis is through observations of seismic anisotropy, such as shear wave splitting. We examine patterns of shear wave splitting using data from two seismic deployments in Argentina that lay updip of the slab tear. We observe a simple pattern of plate‐motion‐parallel fast splitting directions, indicative of plate‐motion‐parallel mantle flow, beneath the majority of the stations. Our observed splitting contrasts previous observations to the north and south of the flat slab region. Since plate‐motion‐parallel splitting occurs only coincidentally with the slab tear, we propose mantle material flows through the opening resulting in Nazca plate‐motion‐parallel flow in both the subslab mantle and mantle wedge.

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Section: Introductionsupporting

confidence: 81%

Section: 1002/2017gl074312mentioning

confidence: 89%

Section: Discussionmentioning

confidence: 99%

Section: 1002/2017gl074312mentioning

confidence: 98%

mentioning

confidence: 99%

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Mantle flow through a tear in the Nazca slab inferred from shear wave splitting

Lynner

Anderson

Portner

et al. 2017

Geophysical Research Letters

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Velocity structure beneath the southern Puna plateau: Evidence for delamination

Calixto

Sandvol

Kay

et al. 2013

Geochem Geophys Geosyst

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[1] The high elevation of the southern Puna plateau, the widespread melting of its crust, the gap in intermediate depth seismicity and the recent eruptions of ignimbrite complexes can be explained by delamination of the lithospheric mantle beneath it. To test this hypothesis, an array consisting of 73 broad band and short period seismic stations was deployed in the region for a period of 2 years starting in 2007. We inverted the data using the two plane wave approach and obtained 1-D and 3-D Rayleigh wave phase velocities. Our dispersion curve shows that at short periods (<70 s) the phase velocities are slightly higher than those of the Tibetan plateau and lower than those of the Anatolian plateau. At periods of 100-140 s we observe a low velocity zone that might be remnant hot asthenosphere below a flat slab (7-10 Ma). We estimate the average continental lithosphere thickness for the region to be between 100 and 130 km. Our three-dimensional Rayleigh wave phase velocities show a high velocity anomaly at low frequencies (0.007, 0.008, and 0.009 Hz) slightly to the north of Cerro Galan. This would be consistent with the hypothesis of delamination in which a piece of lithosphere has detached and caused upwelling of hot asthenosphere, which in turn caused widespread alkaline-collision related volcanism. This interpretation is also corroborated by our shear wave velocity model, where a high velocity anomaly beneath the northern edge of Cerro Galan at 130 km depth is interpreted as the delaminated block on top of the subducting Nazca slab.

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Subduction dynamics and structural controls on shear wave splitting along the South American convergent margin

Lynner

Beck

2020

Journal of South American Earth Sciences

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Shear wave splitting and shear wave splitting tomography of the southern Puna plateau

Cited by 11 publications

References 53 publications

Mantle flow through a tear in the Nazca slab inferred from shear wave splitting

Mantle flow through a tear in the Nazca slab inferred from shear wave splitting

Velocity structure beneath the southern Puna plateau: Evidence for delamination

Subduction dynamics and structural controls on shear wave splitting along the South American convergent margin

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