Publications
129 results found
Maguire R, Ritsema J, Bonnin M, et al., 2017, Evaluating the resolution of deep mantle plumes in teleseismic traveltime tomography, Journal of Geophysical Research, Vol: 123, Pages: 384-400, ISSN: 0148-0227
The strongest evidence to support the classical plume hypothesis comes from seismic imaging of the mantle beneath hot spots. However, imaging results are often ambiguous and it is questionable whether narrow plume tails can be detected by present-day seismological techniques. Here we carry out synthetic tomography experiments based on spectral element method simulations of seismic waves with period T > 10 s propagating through geodynamically derived plume structures. We vary the source-receiver geometry in order to explore the conditions under which lower mantle plume tails may be detected seismically. We determine that wide-aperture (4,000–6,000 km) networks with dense station coverage (<100–200 km station spacing) are necessary to image narrow (<500 km wide) thermal plume tails. We find that if uncertainties on traveltime measurements exceed delay times imparted by plume tails (typically <1 s), the plume tails are concealed in seismic images. Vertically propagating SKS waves enhance plume tail recovery but lack vertical resolution in regions that are not independently constrained by direct S paths. We demonstrate how vertical smearing of an upper mantle low-velocity anomaly can appear as a plume originating in the deep mantle. Our results are useful for interpreting previous plume imaging experiments and guide the design of future experiments.
Maguire R, Ritsema J, Goes S, 2017, Signals of 660-km topography and harzburgite enrichment in seismic images of whole-mantle upwellings, Geophysical Research Letters, Vol: 44, Pages: 3600-3607, ISSN: 1944-8007
Various changes in seismic structures across the mantle transition zone (MTZ) indicate that it may hamper thermal and chemical circulation. Here we show how thermal elevation of the postspinel phase transition at 660 km depth plus harzburgite segregation below this depth can project as narrow high-velocity anomalies in tomographic images of continuous thermochemical mantle upwellings. Model S40RTS features a narrow high-velocity anomaly of +0.8% near 660 km depth within the broad low-velocity structure beneath the Samoa hot spot. Our analyses indicate that elevation of the 660 phase boundary in a hot pyrolitic plume alone is insufficient to explain this anomaly. An additional effect of harzburgite enrichment is required and consistent with geodynamic simulations that predict compositional segregation in the MTZ, especially within thermochemical upwellings. The Samoa anomaly can be modeled with a 125–175°C excess temperature and a harzburgite enrichment below 660 of least 60% compared to a pyrolitic mantle.
Goes S, Agrusta R, Van Hunen J, et al., 2017, Subduction-transition zone interaction: a review, Geosphere, Vol: 13, Pages: 1-21, ISSN: 1553-040X
As subducting plates reach the base of the upper mantle, some appear to flatten and stagnate, while others seemingly go through unimpeded. This variable resistance to slab sinking has been proposed to affect long-term thermal and chemical mantle circulation. A review of observational constraints and dynamic models highlights that neither the increase in viscosity between upper and lower mantle (likely by a factor 20–50) nor the coincident endothermic phase transition in the main mantle silicates (with a likely Clapeyron slope of –1 to –2 MPa/K) suffice to stagnate slabs. However, together the two provide enough resistance to temporarily stagnate subducting plates, if they subduct accompanied by significant trench retreat. Older, stronger plates are more capable of inducing trench retreat, explaining why backarc spreading and flat slabs tend to be associated with old-plate subduction. Slab viscosities that are ∼2 orders of magnitude higher than background mantle (effective yield stresses of 100–300 MPa) lead to similar styles of deformation as those revealed by seismic tomography and slab earthquakes. None of the current transition-zone slabs seem to have stagnated there more than 60 m.y. Since modeled slab destabilization takes more than 100 m.y., lower-mantle entry is apparently usually triggered (e.g., by changes in plate buoyancy). Many of the complex morphologies of lower-mantle slabs can be the result of sinking and subsequent deformation of originally stagnated slabs, which can retain flat morphologies in the top of the lower mantle, fold as they sink deeper, and eventually form bulky shapes in the deep mantle.
Agrusta R, Goes S, Van Hunen J, 2017, Subducting-slab transition-zone interaction: stagnation, penetration and mode switches, Earth and Planetary Science Letters, Vol: 464, Pages: 10-23, ISSN: 1385-013X
Seismic tomography showsthat subducting slabs can either sink straight into the lowermantle, or lie down in the mantle transition zone. Moreover, some slabs seem to have changedmode from stagnation to penetration or vice-versa. We investigate the dynamic controls on these modes and particularly the transition between themusing 2D self-consistent thermo-mechanical subduction models.Our models confirm that the ability of the trench to move is key for slab flattening in the transition zone. Over a wide range of plausible Clapeyron slopes and viscosity jumps at the base of the 15transition zone, hot young slabs (25 Myrin our models) are most likely to penetrate,while cold old slabs (150 Myr) drive more trench motion and tend to stagnate. Several mechanisms are able to inducepenetrating slabs to stagnate:ageing of the subducting plate, decreasing upper plate forcing, andincreasing Clapeyron slope(e.g.due to the arrival of a more hydrated slab).Gettingstagnating slabs to penetrate is more difficult. It can be accomplishedby an instantaneous change inthe forcing of the upper plate from free to motionless,ora sudden decrease inthe Clapeyron slope. A rapid changein plate age at the trench from old to young cannot easily induce penetration. On Earth, ageing of thesubducting plateage(with accompanying upper plate rifting)may be the most common mechanism for causing slab stagnation, while strong changes inupper plate forcingappear required for triggering slab penetration.
Perrin A, Goes S, Prytulak J, et al., 2016, Reconciling mantle wedge thermal structure with arc lava thermobarometric determinations in oceanic subduction zones, Geochemistry, Geophysics, Geosystems, Vol: 17, Pages: 4105-4127, ISSN: 1525-2027
Subduction zone mantle wedge temperatures impact plate interaction, melt generation, and chemical recycling. However, it has been challenging to reconcile geophysical and geochemical constraints on wedge thermal structure. Here we chemically determine the equilibration pressures and temperatures of primitive arc lavas from worldwide intraoceanic subduction zones and compare them to kinematically driven thermal wedge models. We find that equilibration pressures are typically located in the lithosphere, starting just below the Moho, and spanning a wide depth range of ∼25 km. Equilibration temperatures are high for these depths, averaging ∼1300°C. We test for correlations with subduction parameters and find that equilibration pressures correlate with upper plate age, indicating overriding lithosphere thickness plays a role in magma equilibration. We suggest that most, if not all, thermobarometric pressure and temperature conditions reflect magmatic reequilibration at a mechanical boundary, rather than reflecting the conditions of major melt generation. The magma reequilibration conditions are difficult to reconcile, to a first order, with any of the conditions predicted by our dynamic models, with the exception of subduction zones with very young, thin upper plates. For most zones, a mechanism for substantially thinning the overriding plate is required. Most likely thinning is localized below the arc, as kinematic thinning above the wedge corner would lead to a hot fore arc, incompatible with fore-arc surface heat flow and seismic properties. Localized subarc thermal erosion is consistent with seismic imaging and exhumed arc structures. Furthermore, such thermal erosion can serve as a weakness zone and affect subsequent plate evolution.
Civiero C, Goes S, Hammond JOS, et al., 2016, Small-scale thermal upwellings under the northern East African Rift from S travel time tomography, Journal of Geophysical Research. Solid Earth, Vol: 121, Pages: 7395-7408, ISSN: 2169-9313
There is a long-standing debate over how many and what types of plumes underlie the East African rift and whether they do or do not drive its extension and consequent magmatism and seismicity. Here we present a new tomographic study of relative teleseismic S and SKS residuals that expands the resolution from previous regional studies below the northern East African Rift to image structure from the surface to the base of the transition zone. The images reveal two low-velocity clusters, below Afar and west of the Main Ethiopian Rift, that extend throughout the upper mantle and comprise several smaller-scale (about 100-km diameter) low-velocity features. These structures support those of our recent P tomographic study below the region. The relative magnitude of S to P residuals is around 3.5, which is consistent with a predominantly thermal nature of the anomalies. The S- and P-velocity anomalies in the low-velocity clusters can be explained by similar excess temperatures in the range of 100-200°C, consistent with temperatures inferred from other seismic, geochemical and petrological studies. Somewhat stronger VS anomalies below Afar than west of the MER may include an expression of volatiles and/or melt in this region. These results, together with a comparison with previous larger scale tomographic models, indicate that these structures are likely small-scale upwellings with mild excess temperatures, rising from a regional thermal boundary layer at the base of the upper mantle.
Maguire R, Ritsema J, van Keken PE, et al., 2016, P- and S-wave delays caused by thermal plumes, Geophysical Journal International, Vol: 206, Pages: 1169-1178, ISSN: 0956-540X
Many studies have sought to seismically image plumes rising from the deep mantle in order to settle the debate about their presence and role in mantle dynamics, yet the predicted seismic signature of realistic plumes remains poorly understood. By combining numerical simulations of flow, mineral-physics constraints on the relationships between thermal anomalies and wave speeds, and spectral-element method based computations of seismograms, we estimate the delay times of teleseismic S and P waves caused by thermal plumes. Wave front healing is incomplete for seismic periods ranging from 10 s (relevant in traveltime tomography) to 40 s (relevant in waveform tomography). We estimate P-wave delays to be immeasurably small (<0.3 s). S-wave delays are larger than 0.4 s even for S waves crossing the conduits of the thinnest thermal plumes in our geodynamic models. At longer periods (>20 s), measurements of instantaneous phase misfit may be more useful in resolving narrow plume conduits. To detect S-wave delays of 0.4–0.8 s and the diagnostic frequency dependence imparted by plumes, it is key to minimize the influence of the heterogeneous crust and upper mantle. We argue that seismic imaging of plumes will advance significantly if data from wide-aperture ocean-bottom networks were available since, compared to continents, the oceanic crust and upper mantle are relatively simple.
Davies DR, LeVoci G, Goes S, et al., 2016, The Mantle Wedge's Transient 3-D Flow Regime and Thermal Structure, Geochemistry Geophysics Geosystems, Vol: 17, Pages: 78-100, ISSN: 1525-2027
Arc volcanism, volatile cycling, mineralization, and continental crust formation are likely regulated by the mantle wedge's flow regime and thermal structure. Wedge flow is often assumed to follow a regular corner-flow pattern. However, studies that incorporate a hydrated rheology and thermal buoyancy predict internal small-scale-convection (SSC). Here, we systematically explore mantle-wedge dynamics in 3-D simulations. We find that longitudinal “Richter-rolls” of SSC (with trench-perpendicular axes) commonly occur if wedge hydration reduces viscosities to inline image Pa s, although transient transverse rolls (with trench-parallel axes) can dominate at viscosities of inline image Pa s. Rolls below the arc and back arc differ. Subarc rolls have similar trench-parallel and trench-perpendicular dimensions of 100–150 km and evolve on a 1–5 Myr time-scale. Subback-arc instabilities, on the other hand, coalesce into elongated sheets, usually with a preferential trench-perpendicular alignment, display a wavelength of 150–400 km and vary on a 5–10 Myr time scale. The modulating influence of subback-arc ridges on the subarc system increases with stronger wedge hydration, higher subduction velocity, and thicker upper plates. We find that trench-parallel averages of wedge velocities and temperature are consistent with those predicted in 2-D models. However, lithospheric thinning through SSC is somewhat enhanced in 3-D, thus expanding hydrous melting regions and shifting dehydration boundaries. Subarc Richter-rolls generate time-dependent trench-parallel temperature variations of up to inline image K, which exceed the transient 50–100 K variations predicted in 2-D and may contribute to arc-volcano spacing and the variable seismic velocity structures imaged beneath some arcs.
Civiero C, Hammond J, Goes S, et al., 2015, Multiple mantle upwellings in the transition zone beneath the Northern East-African Rift System from relative P-wave travel-time tomography, Geochemistry Geophysics Geosystems, Vol: 16, Pages: 2949-2968, ISSN: 1525-2027
Mantle plumes and consequent plate extension have been invoked as the likely cause of East African Rift volcanism. However, the nature of mantle upwelling is debated, with proposed configurations ranging from a single broad plume connected to the large low-shear-velocity province beneath Southern Africa, the so-called African Superplume, to multiple lower-mantle sources along the rift. We present a new P-wave travel-time tomography model below the northern East-African, Red Sea and Gulf of Aden rifts and surrounding areas. Data are from stations that span an area from Madagascar to Saudi Arabia. The aperture of the integrated dataset allows us to image structures of ∼100 km length scale down to depths of 700-800 km beneath the study region. Our images provide evidence of two clusters of low-velocity structures consisting of features with diameter of 100-200 km that extend through the transition zone, the first beneath Afar and a second just west of the Main Ethiopian Rift, a region with off-rift volcanism. Considering seismic sensitivity to temperature, we interpret these features as upwellings with excess temperatures of 100±50 K. The scale of the upwellings is smaller than expected for lower mantle plume sources. This, together with the change in pattern of the low-velocity anomalies across the base of the transition zone, suggests that ponding or flow of deep-plume material below the transition zone may be spawning these upper-mantle upwellings.
Armitage JJ, Ferguson DJ, Goes S, et al., 2015, Upper mantle temperature and the onset of extension and break-up in Afar, Africa, EARTH AND PLANETARY SCIENCE LETTERS, Vol: 418, Pages: 78-90, ISSN: 0012-821X
Davies DR, Goes S, Lau HCP, 2015, Thermally dominated deep mantle LLSVPs: A review, The Earth’s Heterogeneous Mantle: a geophysical, geodynamical, geochemical perspective, Editors: Khan, Deschamps, Publisher: Springer, Pages: 441-477
The two large low shear-wave velocity provinces (LLSVPs) that dominate lower-mantle structure may hold key information on Earth’s thermal and chemical evolution. It is generally accepted that these provinces are hotter than background mantle and are likely the main source of mantle plumes. Increasingly, it is also proposed that they hold a dense (primitive and/or recycled) compositional com- ponent. The principle evidence that LLSVPs may represent thermo-chemical ‘piles’ comes from seismic constraints, including: (i) their long-wavelength nature; (ii) sharp gradients in shear-wave velocity at their margins; (iii) non-Gaussian distributions of deep mantle shear-wave velocity anomalies; (iv) anti-correlated shear-wave and bulk-sound velocity anomalies (and elevated ratios between shear- and compressional-wave velocity anomalies); (v) anti-correlated shear-wave and density anomalies; and (vi) 1-D/radial profiles of seismic velocity that deviate from those expected for an isochemical, well-mixed mantle. In addition, it has been proposed that hotspots and the reconstructed eruption sites of large ig- neous provinces correlate in location with LLSVP margins. In this paper, we review recent results which indicate that the majority of these constraints do not require thermo-chemical piles: they are equally well (or poorly) explained by thermal heterogeneity alone. Our analyses and conclusions are largely based on comparisons between imaged seismic structure and synthetic seismic structures from a set of thermal and thermo-chemical mantle convection models, which are constrained by ∼ 300 Myr of plate motion histories. Modelled physical structure (temperature, pressure and composition) is converted into seismic velocities via a thermodynamic approach that accounts for elastic, anelastic and phase con- tributions and, subsequently, a tomographic resolution filter is applied to account for the damping and geographic bias inherent to seismic imaging. Our re
Davies DR, Goes S, Sambridge M, 2015, On the relationship between volcanic hotspot locations, the reconstructed eruption sites of large igneous provinces and deep mantle seismic structure, Earth and Planetary Science Letters, Vol: 411, Pages: 121-130, ISSN: 0012-821X
It has been proposed that volcanic hotspots and the reconstructed eruption sites of large igneous provinces (LIPs) are preferentially located above the margins of two deep mantle large low shear-wave velocity provinces (LLSVPs), beneath the African continent and the Pacific Ocean. This spatial correlation has been interpreted to imply that LLSVPs represent long-lived, dense, stable thermo-chemical piles, which preferentially trigger mantle plumes at their edges and exert a strong influence on lower-mantle dynamics. Here, we re-analyse this spatial correlation, demonstrating that it is not global: it is strong for the African LLSVP, but weak for the Pacific. Moreover, Monte Carlo based statistical analyses indicate that the observed distribution of African and Pacific hotspots/reconstructed LIPs is consistent with the hypothesis that they are drawn from a sample that is uniformly distributed across the entire areal extent of each LLSVP: the stronger spatial correlation with the margin of the African LLSVP is expected as a simple consequence of its elongated geometry, where more than 75% of the LLSVP interior lies within 10° of its margin. Our results imply that the geographical distribution of hotspots and reconstructed LIPs does not indicate the extent to which chemical heterogeneity influences lower-mantle dynamics.
Davies DR, Goes S, Lau HCP, 2015, Thermally Dominated Deep Mantle LLSVPs: A Review, EARTH'S HETEROGENEOUS MANTLE: A GEOPHYSICAL, GEODYNAMICAL, AND GEOCHEMICAL PERSPECTIVE, Editors: Khan, Deschamps, Publisher: SPRINGER-VERLAG BERLIN, Pages: 441-477, ISBN: 978-3-319-15626-2
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- Citations: 63
Agrusta R, van Hunen J, Goes S, 2014, The effect of metastable pyroxene on the slab dynamics, Geophysical Research Letters, Vol: 41, Pages: 8800-8808, ISSN: 1944-8007
Seismic studies show that some subducting slabs penetrate straight into the lower mantle, whereas others seem to flatten near the base of the mantle transition zone. Slab stagnation is often attributed to an increase in viscosity and phase transformations in the olivine system. However, recent mineral physics studies showed that due to extremely low transformational diffusion rates, low-density metastable pyroxene may persist into the transition zone in cool slabs. Here we use a dynamically fully self-consistent subduction model to investigate the influence of metastable pyroxene on the dynamics of subducting oceanic lithosphere. Our results show that metastable pyroxene affects slab buoyancy at least as much as olivine metastability. However, unlike metastable olivine, which can inhibit slab penetration in the lower mantle only for cold, old, and fast slabs, metastable pyroxene is likely to also affect sinking of relatively young and slow slabs.
Fourel L, Goes S, Morra G, 2014, The role of elasticity in slab bending, Geochemistry, Geophysics, Geosystems, Vol: 15, Pages: 4507-4525, ISSN: 1525-2027
Previous studies showed that plate rheology exerts a dominant control on the shape and velocity of subducting plates. Here, we perform a systematic investigation of the role of elasticity in slab bending, using fully dynamic 2-D models where an elastic, viscoelastic, or viscoelastoplastic plate subducts freely into a purely viscous mantle. We derive a scaling relationship between the bending radius of viscoelastic slabs and the Deborah number, De, which is the ratio of Maxwell time over deformation time. We show that De controls the ratio of elastically stored energy over viscously dissipated energy and find that at inline image, substantially less energy is required to bend a viscoelastic slab to the same shape as a purely viscous slab with the same intrinsic viscosity. Elastically stored energy at higher De favors retreating modes of subduction via unbending, while trench advance only occurs for some cases with inline image. We estimate the apparent Deborah numbers of natural subduction zones and find values ranging from inline image to > 1, where most zones have low inline image, but a few young plates have De > 0.1. Slabs with inline image either have very low viscosities or they may be yielding, in which case our De estimates may be underestimated by up to an order of magnitude, potentially pointing towards a significant role of elasticity in inline image of the subduction zones. In support of such a role of elasticity in subduction, we find that increasing De correlates with increasing proportion of larger seismic events in both instrumental and historic catalogues.
Greve S, Paulssen H, Goes S, et al., 2014, Shear-velocity structure of the Tyrrhenian Sea: Tectonics, volcanism and mantle (de)hydration of a back-arc basin, EARTH AND PLANETARY SCIENCE LETTERS, Vol: 400, Pages: 45-53, ISSN: 0012-821X
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- Citations: 17
Garel F, Goes S, Davies DR, et al., 2014, Interaction of subducted slabs with the mantle transition-zone: A regime diagram from 2-D thermo-mechanical models with a mobile trench and an overriding plate, GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS, Vol: 15, Pages: 1739-1765
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- Citations: 132
Le Voci G, Davies DR, Goes S, et al., 2014, A systematic 2-D investigation into the mantle wedge's transient flow regime and thermal structure: Complexities arising from a hydrated rheology and thermal buoyancy, GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS, Vol: 15, Pages: 28-51, ISSN: 1525-2027
Goes S, 2013, EARTH SCIENCE Western North America's jigsaw, NATURE, Vol: 496, Pages: 35-37, ISSN: 0028-0836
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- Citations: 3
Goes S, Eakin CM, Ritsema J, 2013, Lithospheric cooling trends and deviations in oceanic <i>PP</i>-<i>P</i> and <i>SS</i>-<i>S</i> differential traveltimes, JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH, Vol: 118, Pages: 996-1007, ISSN: 2169-9313
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- Citations: 13
Goes S, Armitage J, Harmon N, et al., 2012, Low seismic velocities below mid-ocean ridges: Attenuation versus melt retention, JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH, Vol: 117, ISSN: 2169-9313
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- Citations: 54
Davies DR, Goes S, Davies JH, et al., 2012, Reconciling dynamic and seismic models of Earth's lower mantle: The dominant role of thermal heterogeneity, EARTH AND PLANETARY SCIENCE LETTERS, Vol: 353, Pages: 253-269, ISSN: 0012-821X
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- Citations: 177
Styles E, Goes S, van Keken PE, et al., 2011, Synthetic images of dynamically predicted plumes and comparison with a global tomographic model, EARTH AND PLANETARY SCIENCE LETTERS, Vol: 311, Pages: 351-363, ISSN: 0012-821X
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- Citations: 25
Hwang YK, Ritsema J, van Keken PE, et al., 2011, Wavefront healing renders deep plumes seismically invisible, GEOPHYSICAL JOURNAL INTERNATIONAL, Vol: 187, Pages: 273-277, ISSN: 0956-540X
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- Citations: 33
Hwang YK, Ritsema J, Goes S, 2011, Global variation of body-wave attenuation in the upper mantle from teleseismic P wave and S wave spectra, GEOPHYSICAL RESEARCH LETTERS, Vol: 38, ISSN: 0094-8276
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- Citations: 16
Styles E, Davies DR, Goes S, 2011, Mapping spherical seismic into physical structure: biases from 3-D phase-transition and thermal boundary-layer heterogeneity, GEOPHYSICAL JOURNAL INTERNATIONAL, Vol: 184, Pages: 1371-1378, ISSN: 0956-540X
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- Citations: 26
Goes S, 2011, Computational methods for geodynamics, Geophysical Journal International, Vol: 184, Pages: 974-974, ISSN: 0956-540X
Goes S, Capitanio FA, Morra G, et al., 2011, Signatures of downgoing plate-buoyancy driven subduction in Cenozoic plate motions, PHYSICS OF THE EARTH AND PLANETARY INTERIORS, Vol: 184, Pages: 1-13, ISSN: 0031-9201
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- Citations: 37
van Wijk JW, Baldridge WS, van Hunen J, et al., 2010, Small-scale convection at the edge of the Colorado Plateau: Implications for topography, magmatism, and evolution of Proterozoic lithosphere, GEOLOGY, Vol: 38, Pages: 611-614, ISSN: 0091-7613
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- Citations: 132
Hieronymus CF, Goes S, 2010, Complex cratonic seismic structure from thermal models of the lithosphere: effects of variations in deep radiogenic heating, GEOPHYSICAL JOURNAL INTERNATIONAL, Vol: 180, Pages: 999-1012, ISSN: 0956-540X
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- Citations: 35
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