期刊
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH
卷 126, 期 2, 页码 -出版社
AMER GEOPHYSICAL UNION
DOI: 10.1029/2020JB020350
关键词
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资金
- Swiss Federal Institute of Technology (ETH) [ETH05 17-1]
- European Union [793824]
- Swiss National Science Foundation via an Ambizione Fellowship [180025]
- Swiss National Science Foundation [159907, 191892]
- Swiss National Supercomputing Centre (CSCS) [s922]
- Marie Curie Actions (MSCA) [793824] Funding Source: Marie Curie Actions (MSCA)
By inverting seismic recordings, we constructed a thermochemical structure model of the crust and mantle, identifying three major tectonic regions – TAW, CTR, and COE – with distinct mantle chemical and seismic properties.
We image the thermochemical structure of crust and mantle underneath the North American continent by inverting recordings of P-to-s (Ps) and S-to-p (Sp) converted seismic body waves (receiver functions [RFs]). Through careful data selection and processing, we construct a multifrequency Ps (5-, 8-, and 10 -s) and Sp (10- and 15- s) RF data set from USArray recordings. The inversion is interfaced with petrological phase equilibria computations to build self-consistent radial seismic velocity and density models for RF waveform simulations. Inverted models are combined through back-projection along converted raypaths and interpolation to tomographic images of crust and mantle structure. Through clustering analysis we identify three major tectonic regions based on mantle thermochemical and seismic structure: the tectonically active West (TAW), the central transition region (CTR), and the cratonic-orogenic East (COE). TAWis chemically more fertile with a Mg# similar to 0.90 (molar Mg# = Mg/(Mg+Fe)) and characterized by an elevated mantle potential temperature of 1490 +/- 27 degrees C relative to COE, which is chemically more depleted (Mg# similar to 0.91) and colder (1419 +/- 27 degrees C). CTR is intermediate to TAW and COE. We find significant thermochemically induced topography associated with the base of the lithosphere (+/- 90 km), while the mantle transition zone is mostly influenced by thermally induced topography on the 410-km discontinuity (+/- 15 km). In contrast, the 660-km discontinuity, where variations are only +/- 5 km, reflects a more complex thermochemical interplay. To place the results in a tectonic context, thermobarometric estimates from basaltic rocks across the western United States are integrated with the seismic inversions to produce a thermal model of the underlying mantle.
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