Mapping the Thermal Lithosphere and Melting Across the Continental US

Porter, R. C.; Reid, M. R.

doi:10.1029/2020gl092197

Cited by 7 publications

(2 citation statements)

References 70 publications

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“…Another improvement from the new approach is the uppermost mantle Vs. Uppermost mantle Vs can be used to infer the temperature and possible distribution of partial melting (Hansen et al., 2015; Porter & Reid, 2021). However, the depth‐velocity trade‐off of surface waves often leads to the correlation between uppermost mantle Vs and Moho depth, as demonstrated by the synthetic test (Figure 9a).…”

Section: Discussionmentioning

confidence: 99%

Incorporating H‐κ Stacking With Monte Carlo Joint Inversion of Multiple Seismic Observables: A Case Study for the Northwestern US

Wu,

Sui,

Shen

2024

JGR Solid Earth

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Accurately determining the seismic structure of the continental deep crust is crucial for understanding its geological evolution and continental dynamics in general. However, traditional tools such as surface waves often face challenges in solving the trade‐offs between elastic parameters and discontinuities. In this work, we present a new approach that combines two established inversion techniques, receiver function H‐κ stacking and joint inversion of surface wave dispersion and receiver function waveforms, within a Bayesian Monte Carlo (MC) framework to address these challenges. Demonstrated by synthetic tests, the new method greatly reduces trade‐offs between critical parameters, such as the deep crustal Vs, Moho depth, and crustal Vp/Vs ratio. This eliminates the need for assumptions regarding crustal Vp/Vs ratios in joint inversion, leading to a more accurate outcome. Furthermore, it improves the precision of the upper mantle velocity structure by reducing its trade‐off with Moho depth. Additional notes on the sources of bias in the results are also included. Application of the new approach to USArray stations in the Northwestern US reveals consistency with previous studies and identifies new features. Notably, we find elevated Vp/Vs ratios in the crystalline crust of regions such as coastal Oregon, suggesting potential mafic composition or fluid presence. Shallower Moho depth in the Basin and Range indicates reduced crustal support to the elevation. The uppermost mantle Vs, averaging 5 km below Moho, aligns well with the Pn‐derived Moho temperature variations, offering the potential of using Vs as an additional constraint to Moho temperature and crustal thermal properties.

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Section: Discussionmentioning

confidence: 99%

Incorporating H‐κ Stacking With Monte Carlo Joint Inversion of Multiple Seismic Observables: A Case Study for the Northwestern US

Wu,

Sui,

Shen

2024

JGR Solid Earth

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“…It is notable that much of the western USA is in tectonic extension, whereas western Canada and Alaska are in compression, indicating that the extension is not required for recent backarc volcanics. In the western USA Cordillera, both the major element geochemistry (e.g., Plank & Forsyth, 2016; and references therein) and trace element geochemistry (Klöcking et al., 2018) indicate a surprisingly uniform temperature and depth at the LAB of 65 ± 5 km, and a LAB temperature of ∼1,350°C ± 25°C (extrapolated surface potential temperature of ∼1,325°C) (with the exception of the Yellowstone hot spot area and recently thinned lithosphere Colorado Plateau) (also R. Porter & Reid, 2021). One hypothesis is that this depth is constrained by the spinel peridotite to garnet peridotite pressure‐controlled phase boundary (e.g., Hyndman & Canil, 2021b).…”

Section: Lab Temperature and Pressure (Depth) From The Geochemistry O...mentioning

confidence: 99%

The Thermal Regime of NW Canada and Alaska, and Tectonic and Seismicity Consequences

Hyndman

2023

Geochem Geophys Geosyst

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NW Canada and Alaska are the continuation of the North American Cordillera through Mexico, western USA and western Canada. I show that they have similar thermal regimes and thermal control of tectonics and seismicity. I first summarize the multiple constraints to crust and upper mantle temperatures and then discuss some consequences. There are bimodal crust and upper mantle temperatures characteristic of most subduction zones: cool forearc, uniformly hot backarc (Yukon Composite Terrane to Southern Brooks Range, and Mackenzie Mountains), and stable cratonic backstops (Arctic Alaska Terrane and Canadian Shield). The main constraints are as follows: (a) Heat flow measurements, (b) Temperature‐dependent upper mantle velocities and seismic attenuation, (c) Temperature‐dependent topographic elevations; thermal isostasy, (d) Depth and temperature of the seismic lithosphere‐asthenosphere boundary (LAB), (e) Origin temperature and depth of craton kimberlite xenoliths, (f) Geochemically inferred source temperature and depth of recent volcanic rocks. (g) Depth to the magnetic Curie temperature, (h) Depth extent of seismicity. The backarc lithosphere is thin, LAB at 50–85 km and ∼1,350°C ± 25°C. Moho temperatures at 35 km are 850°C ± 100°C compared to cool cratonic areas of 400°C–500°C. The consequences include the following: (a) Thin and weak backarc lithosphere that accommodates pervasive tectonic deformation indicated by wide‐spread seismicity and GPS‐defined motions, in contrast to the stable cratonic regions; (b) Weak backarc lower crust that flattens the Moho and allows detachment and thrusting of the upper crust over the cold strong Arctic Alaska Terrane and Canadian Shield. This article provides a model for how to estimate deep temperatures from multiple constraints.

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A New View of Shear Wavespeed and the Lithosphere‐Asthenosphere Boundary in the Southwestern United States

Golos,

Brunsvik,

Eilon

et al. 2024

JGR Solid Earth

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The Southwestern United States experiences active deformation, seismicity, and magmatism, remarkable in an intraplate setting. The Basin and Range and Colorado Plateau (CP) are inferred to differ in lithospheric thickness, but modeling geophysical properties of the lithosphere, in particular the depth of the Lithosphere‐Asthenosphere Boundary (LAB), across the entirety of the region, has proved challenging. Here, we introduce a new model of 1‐D depth profiles in shear wavespeed, determined through a probabilistic joint inversion of information from Sp receiver functions and Rayleigh wave phase velocity. From these profiles we quantify the locations and Vs contrast of wavespeed gradients that represent boundaries such as the Moho, the LAB, and intralithospheric discontinuities. We infer a lithosphere that is thinner and lower in Vs in the Basin and Range. In the CP and farther north, the LAB is more gradual, deeper, and intermittently observed. We also observe Mid‐Lithospheric Discontinuities (MLDs) near the boundaries between the CP, Wyoming Craton, and Northern Basin and Range, as well as within the Craton. When both an MLD and LAB are observed, the Vs gradient associated with the LAB is narrower than expected. Finally, we image Positive Velocity Gradients beneath areas of thinner lithosphere, which are consistent with recent global observations that have been attributed to the base of a partially molten zone below the lithosphere. Overall, the picture of the lithosphere‐asthenosphere system that emerges is one of considerable structural complexity with a strong dependency on tectonic regime and geological history.

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Mapping the Thermal Lithosphere and Melting Across the Continental US

Cited by 7 publications

References 70 publications

Incorporating H‐κ Stacking With Monte Carlo Joint Inversion of Multiple Seismic Observables: A Case Study for the Northwestern US

Incorporating H‐κ Stacking With Monte Carlo Joint Inversion of Multiple Seismic Observables: A Case Study for the Northwestern US

The Thermal Regime of NW Canada and Alaska, and Tectonic and Seismicity Consequences

A New View of Shear Wavespeed and the Lithosphere‐Asthenosphere Boundary in the Southwestern United States

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