Response of the mantle to flat slab evolution: Insights from local <i>S</i> splitting beneath Peru

Eakin, C. M.; Long, Maureen D.; Beck, S. L.; Wagner, L. S.; Tavera, Hernando; Condori, Cristobal

doi:10.1002/2014gl059943

Cited by 34 publications

(44 citation statements)

References 52 publications

(65 reference statements)

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…These are colocated with low Rayleigh wave phase velocities. The alignment of fast directions is consistent with the results of local shear wave splitting [ Eakin et al , ]. At 50 s we observe little to no anisotropy in this area (Figure b, dashed green area).…”

Section: Resultssupporting

confidence: 91%

“…The model for upper mantle anisotropy obtained in this study provides constraints complementary to those provided by shear wave splitting, which has previously been studied in this region by Eakin et al [, , ] and Long et al []. Here we briefly discuss the comparison between the two types of studies, illustrated in Figure .…”

Section: Discussionsupporting

confidence: 66%

“…Recent shear wave splitting studies, however, have found more complex patterns across southern Peru. Results of local shear wave splitting reveal predominantly trench‐parallel alignments of fast directions north of the subducting ridge and heterogeneous anisotropic patterns south of the ridge [ Eakin et al , ]. Shear wave splitting analyses of SKS, sSKS, and PKS phases between 10° and 18°S illuminate distinct spatial variations along strike, where the projected subducting Nazca Ridge again marks a sharp boundary in the anisotropic patterns [ Eakin et al , ].…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Effects of change in slab geometry on the mantle flow and slab fabric in Southern Peru

et al. 2016

Self Cite

View full text Add to dashboard Cite

The effects of complex slab geometries on the surrounding mantle flow field are still poorly understood. Here we combine shear wave velocity structure with Rayleigh wave phase anisotropy to examine these effects in southern Peru, where the slab changes its geometry from steep to flat. To the south, where the slab subducts steeply, we find trench‐parallel anisotropy beneath the active volcanic arc that we attribute to the mantle wedge and/or upper portions of the subducting plate. Farther north, beneath the easternmost corner of the flat slab, we observe a pronounced low‐velocity anomaly. This anomaly is caused either by the presence of volatiles and/or flux melting that could result from southward directed, volatile‐rich subslab mantle flow or by increased temperature and/or decompression melting due to small‐scale vertical flow. We also find evidence for mantle flow through the tear north of the subducting Nazca Ridge. Finally, we observe anisotropy patterns associated with the fast velocity anomalies that reveal along strike variations in the slab's internal deformation. The change in slab geometry from steep to flat contorts the subducting plate south of the Nazca Ridge causing an alteration of the slab petrofabric. In contrast, the torn slab to the north still preserves the primary (fossilized) petrofabric first established shortly after plate formation.

show abstract

Section: Resultssupporting

confidence: 91%

Section: Discussionsupporting

confidence: 66%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Effects of change in slab geometry on the mantle flow and slab fabric in Southern Peru

et al. 2016

Self Cite

View full text Add to dashboard Cite

show abstract

“…This results in a broadening of the flat slab as new continental areas to the south become underlain by the ridge and associated flat slab, while areas to the north that were previously underlain by the ridge maintain their flat-slab geometry. This is consistent with earlier studies that attribute the along-strike (trench parallel) extent of the Peruvian flat slab to the southward sweep of the Nazca Ridge over time 8,9 .…”

supporting

confidence: 92%

“…Here, the subducting Nazca Ridge trends at an oblique angle to relative plate motion, resulting in a northward migration of the overriding continent relative to the down-going ridge 8 . We have collected and analysed data from two deployments of broadband seismometers in central and southern Peru: PULSE (Peru Lithosphere and Slab Experiment) 9 , and CAUGHT (Central Andean Uplift and Geodynamics of High Topography) 10 . We also incorporate data from eight stations from the PERUSE deployment (Peru Slab Experiment) 11 and the permanent station called NNA in Lima, Peru (Fig.…”

mentioning

confidence: 99%

The role of ridges in the formation and longevity of flat slabs

Antonijevic

Wagner

Kumar

et al. 2015

Nature

Self Cite

107

View full text Add to dashboard Cite

Flat-slab subduction occurs when the descending plate becomes horizontal at some depth before resuming its descent into the mantle. It is often proposed as a mechanism for the uplifting of deep crustal rocks ('thick-skinned' deformation) far from plate boundaries, and for causing unusual patterns of volcanism, as far back as the Proterozoic eon. For example, the formation of the expansive Rocky Mountains and the subsequent voluminous volcanism across much of the western USA has been attributed to a broad region of flat-slab subduction beneath North America that occurred during the Laramide orogeny (80-55 million years ago). Here we study the largest modern flat slab, located in Peru, to better understand the processes controlling the formation and extent of flat slabs. We present new data that indicate that the subducting Nazca Ridge is necessary for the development and continued support of the horizontal plate at a depth of about 90 kilometres. By combining constraints from Rayleigh wave phase velocities with improved earthquake locations, we find that the flat slab is shallowest along the ridge, while to the northwest of the ridge, the slab is sagging, tearing, and re-initiating normal subduction. On the basis of our observations, we propose a conceptual model for the temporal evolution of the Peruvian flat slab in which the flat slab forms because of the combined effects of trench retreat along the Peruvian plate boundary, suction, and ridge subduction. We find that while the ridge is necessary but not sufficient for the formation of the flat slab, its removal is sufficient for the flat slab to fail. This provides new constraints on our understanding of the processes controlling the beginning and end of the Laramide orogeny and other putative episodes of flat-slab subduction.

show abstract

Flat slab deformation caused by interplate suction force

Clayton

2015

Geophysical Research Letters

View full text Add to dashboard Cite

We image the structure at the southern end of the Peruvian flat subduction zone, using receiver function and surface wave methods. The Nazca slab subducts to ~100 km depth and then remains flat for ~300 km distance before it resumes the dipping subduction. The flat slab closely follows the topography of the continental Moho above, indicating a strong suction force between the slab and the overriding plate. A high‐velocity mantle wedge exists above the initial half of the flat slab, and the velocity resumes to normal values before the slab steepens again, indicating the resumption of dehydration and ecologitization. Two prominent midcrust structures are revealed in the 70 km thick crust under the Central Andes: molten rocks beneath the Western Cordillera and the underthrusting Brazilian Shield beneath the Eastern Cordillera.

show abstract

Response of the mantle to flat slab evolution: Insights from local S splitting beneath Peru

Cited by 34 publications

References 52 publications

Effects of change in slab geometry on the mantle flow and slab fabric in Southern Peru

Effects of change in slab geometry on the mantle flow and slab fabric in Southern Peru

The role of ridges in the formation and longevity of flat slabs

Flat slab deformation caused by interplate suction force

Contact Info

Product

Resources

About