Lithospheric records of orogeny within the continental U.S.

Porter, R. C.; Liu, Yuanyuan; Holt, W. E.

doi:10.1002/2015gl066950

Cited by 70 publications

(101 citation statements)

References 62 publications

(92 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Some models (Schmandt et al, 2015;Shen & Ritzwoller, 2016) are relatively fast through the lithospheric column and do not necessarily require invoking grain size effects. The model of Porter et al (2016) generally matches our MT-based temperatures inferences with grain sizes of~10 cm; although slightly larger than typically assumed for the mantle, we nevertheless take this as evidence that anelasticity can indeed reconcile the seemingly disparate MT and seismic results. The model of Wagner et al (2018) is consistent at all depths when taking into account grain sizes of 1 mm to 10 cm.…”

Section: Geochemistry Geophysics Geosystemssupporting

confidence: 83%

“…Resistive upper mantle beneath the SEUS also appears in the global geomagnetic depth sounding (GDS) results of Sun et al (2015). (Pollitz & Mooney, 2016;Porter et al, 2016;Schmandt et al, 2015;Shen & Ritzwoller, 2016;Wagner et al, 2018) and geometric mean resistivity (Murphy & Egbert, 2017) over the same depth range. (Pollitz & Mooney, 2016;Porter et al, 2016;Schmandt et al, 2015;Shen & Ritzwoller, 2016;Wagner et al, 2018) and geometric mean resistivity (Murphy & Egbert, 2017) over the same depth range.…”

Section: Previous Mt Resultsmentioning

confidence: 92%

“…Anharmonicity describes how seismic velocities change (via the constituent elastic parameters) as a function of temperature, pressure, and composition, but it ignores the fact that rocks are composed of discrete crystal grains. At very low frequencies (very long periods, hundreds of seconds for the specified conditions), steady state creep further significantly increases attenuation and decreases the Figure 4, from the five surface wave models (Pollitz & Mooney, 2016;Porter et al, 2016;Schmandt et al, 2015;Shen & Ritzwoller, 2016;Wagner et al, 2018) and the electrical resistivity inverse solutions. At low enough frequencies, grain boundaries do not behave elastically; instead, they behave viscously.…”

Section: Anelasticity Grain Size and Seismic Velocitymentioning

confidence: 99%

“…The model of Pollitz and Mooney (2016) is somewhat of an outlier, but velocities at 120 km and 150 km in their model are still consistent with colder temperatures when taking into account reasonable grain sizes. In Figure 7, this adjustment would have the effect of shifting the observation points to the right in each plot, such that observation pairs from the models of Schmandt et al (2015), Shen and Ritzwoller (2016), and Porter et al (2016) would fall along the predicted curves for realistic grain sizes of~1 mm to 1 cm. The model of Porter et al (2016) generally matches our MT-based temperatures inferences with grain sizes of~10 cm; although slightly larger than typically assumed for the mantle, we nevertheless take this as evidence that anelasticity can indeed reconcile the seemingly disparate MT and seismic results.…”

Section: Geochemistry Geophysics Geosystemsmentioning

confidence: 99%

See 3 more Smart Citations

Synthesizing Seemingly Contradictory Seismic and Magnetotelluric Observations in the Southeastern United States to Image Physical Properties of the Lithosphere

Murphy

Egbert

2019

Geochem Geophys Geosyst

View full text Add to dashboard Cite

Although seismic velocity and electrical conductivity are both sensitive to temperature, thermal lithosphere properties are derived almost exclusively from seismic data because conductivity is often too strongly affected by minor highly conductive phases to be a reliable indicator of temperature. However, in certain circumstances, electrical observations can provide strong constraints on mantle temperatures. In the southeastern United States (SEUS), magnetotelluric (MT) data require high resistivity values (>300 Ωm) to at least 200‐km depth. As dry mantle mineral conduction laws provide an upper bound on temperature for an observed resistivity value, the only interpretation is that lithospheric temperatures (<1330 °C) persist to 200 km. However, seismic tomography shows that velocities in this region are generally slightly slow with respect to references models; this observation has led to a view of relatively thin (<150 km), eroded thermal lithosphere beneath the SEUS. We show that MT and seismic (tomography, attenuation, receiver function) results are consistent with thick (~200 km), coherent thermal lithosphere in this region. Reduced seismic velocities (relative to reference models) can be explained by considering the effect of finite grain size (anelasticity). Calculated velocity as a function of temperature is overall slower when including anelastic effects, even at reasonable grain sizes of 1 mm to 1 cm; this permits mantle temperatures that are colder than would typically be inferred. We argue for a geodynamic scenario in which the present thermal lithosphere in the SEUS formed in association with the Central Atlantic Magmatic Province and has subsequently survived intact for ~200 Ma.

show abstract

Section: Geochemistry Geophysics Geosystemssupporting

confidence: 83%

Section: Previous Mt Resultsmentioning

confidence: 92%

Section: Anelasticity Grain Size and Seismic Velocitymentioning

confidence: 99%

Section: Geochemistry Geophysics Geosystemsmentioning

confidence: 99%

See 2 more Smart Citations

Synthesizing Seemingly Contradictory Seismic and Magnetotelluric Observations in the Southeastern United States to Image Physical Properties of the Lithosphere

Murphy

Egbert

2019

Geochem Geophys Geosyst

View full text Add to dashboard Cite

show abstract

“…The eastern North American coast is the site of significant seismic velocity heterogeneities [Levin et al, 1995;Levin et al, 2000;Li et al, 2003;Godey et al, 2004;Nettles and Dziewonski, 2008;Chu et al, 2013;Schmandt and Lin, 2014;Skryzalin et al, 2015;Pollitz and Mooney, 2016;Porter et al, 2016]. They are a record-albeit an ambiguous one-of lithospheric and asthenospheric processes operating at the continental margin.…”

Section: Introductionmentioning

confidence: 99%

The Northern Appalachian Anomaly: A modern asthenospheric upwelling

Menke

Skryzalin

Levin

et al. 2016

Geophysical Research Letters

View full text Add to dashboard Cite

The Northern Appalachian Anomaly (NAA) is an intense, laterally localized (400 km diameter) low‐velocity anomaly centered in the asthenosphere beneath southern New England. Its maximum shear velocity contrast, at 200 km depth, is about 10%, and its compressional‐to‐shear velocity perturbation ratio is about unity, values compatible with it being a modern thermal anomaly. Although centered close to the track of the Great Meteor hot spot, it is not elongated parallel to it and does not crosscut the cratonic margin. In contrast to previous explanations, we argue that the NAA's spatial association with the hot spot track is coincidental and that it is caused by small‐scale upwelling associated with an eddy in the asthenospheric flow field at the continental margin. That the NAA is just one of several low‐velocity features along the eastern margin of North America suggests that this process may be globally ubiquitous.

show abstract

Post‐rift magmatic evolution of the eastern North American “passive‐aggressive” margin

Mazza

Gazel

Johnson

et al. 2017

Geochem Geophys Geosyst

View full text Add to dashboard Cite

Understanding the evolution of passive margins requires knowledge of temporal and chemical constraints on magmatism following the transition from supercontinent to rifting, to post-rifting evolution. The Eastern North American Margin (ENAM) is an ideal study location as several magmatic pulses occurred in the 200 My following rifting. In particular, the Virginia-West Virginia region of the ENAM has experienced two postrift magmatic pulses at $152 Ma and 47 Ma, and thus provides a unique opportunity to study the long-term magmatic evolution of passive margins. Here we present a comprehensive set of geochemical data that includes new 40 Ar/ 39 Ar ages, major and trace-element compositions, and analysis of radiogenic isotopes to further constrain their magmatic history. The Late Jurassic volcanics are bimodal, from basanites to phonolites, while the Eocene volcanics range from picrobasalt to rhyolite. Modeling suggests that the felsic volcanics from both the Late Jurassic and Eocene events are consistent with fractional crystallization. Sr-Nd-Pb systematics for the Late Jurassic event suggests HIMU and EMII components in the magma source that we interpret as upper mantle components rather than crustal interaction. Lithospheric delamination is the best hypothesis for magmatism in Virginia/West Virginia, due to tectonic instabilities that are remnant from the long-term evolution of this margin, resulting in a ''passive-aggressive'' margin that records multiple magmatic events long after rifting ended.Citation:

show abstract

Lithospheric records of orogeny within the continental U.S.

Cited by 70 publications

References 62 publications

Synthesizing Seemingly Contradictory Seismic and Magnetotelluric Observations in the Southeastern United States to Image Physical Properties of the Lithosphere

Synthesizing Seemingly Contradictory Seismic and Magnetotelluric Observations in the Southeastern United States to Image Physical Properties of the Lithosphere

The Northern Appalachian Anomaly: A modern asthenospheric upwelling

Post‐rift magmatic evolution of the eastern North American “passive‐aggressive” margin

Contact Info

Product

Resources

About