Anisotropic zonation in the lithosphere of Central North America: Influence of a strong cratonic lithosphere on the Mid-Continent Rift

Ola, O.; Frederiksen, A. W.; Bollmann, T. A.; Lee, Suzan van der; Darbyshire, F. A.; Wolin, Emily; Revenaugh, J.; Stein, Carol A.; Stein, Seth; Wysession, M. E.

doi:10.1016/j.tecto.2016.06.031

Cited by 10 publications

(25 citation statements)

References 67 publications

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“…This does not seem to be the case in the lithosphere as the previously mentioned low-velocity zone in central/western Minnesota departs from the Becker Embayment to the northwest instead of following the GLTZ to the southwest. This low-velocity zone also seems to be a line of demarcation where the shear wave splitting of Frederiksen, Deniset, et al (2013) and Ola et al (2016) decreases in split time moving to the southwest and crossing the previously mentioned low-velocity zone. Either the GLTZ is too small to image with the resolution of the model or it does not have a lithospheric signature.…”

Section: Ws High-velocity Anomalysupporting

confidence: 57%

P Wave Teleseismic Traveltime Tomography of the North American Midcontinent

et al. 2019

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The remains of the 1.1‐Ga Midcontinent Rift (MCR) lie in the middle of the tectonically stable portion of North America. Previous and ongoing studies have imaged strong heterogeneity associated with the MCR in the crust but have not imaged such within the mantle. It is unclear whether this is due to the absence of rift‐related mantle structures or these studies had insufficient resolution to image them. To address this issue, we measured 46,374 teleseismic P wave delay times from seismograms recorded by the USArray Transportable Array, Superior Province Rifting EarthScope Experiment, and surrounding permanent stations. We included these and 54,866 delay times from prior studies in our tomographic inversion. We find that high‐velocity anomalies are widespread in our study area, but there are also prominent low‐velocity anomalies. Two of these are coincident with high‐Bouguer gravity anomalies associated with the MCR in Iowa and the Minnesota/Wisconsin border at 50‐ to 150‐km depth. Extensive resolution testing shows that these anomalies could be the result of downward vertical smearing of relatively low velocities from rift‐related material that “underplated" the crust, although we cannot exclude that the subcrustal mantle lithosphere beneath the MCR is anomalously enriched, hydrated, or warm. Other anomalies occur at syntaxes of the Penokean Orogen. One with the Superior Province and Marshfield Terrane in southern Minnesota and another with the Yavapai and Mazatzal Terranes, both at 100‐ to 250‐km depth. In the midmantle, we image two linear high‐velocity anomalies, interpreted as subducted fragments of the Farallon and Kula plates.

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Section: Ws High-velocity Anomalysupporting

confidence: 57%

P Wave Teleseismic Traveltime Tomography of the North American Midcontinent

et al. 2019

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“…Whitmeyer and Karlstrom, 2007), or a combination of the two (Stein et al, 2015). Northward propagation of the MCR was inhibited by the strong Superior lithosphere, and the shape and position of the rift was influenced by the stable craton margin (Ola et al, 2016). There is evidence for basaltic underplating of the Archean lower crust during the 1.1 Ga failed rifting of the mid-continent (e.g.…”

Section: Underplating At the Mid-continent Riftmentioning

confidence: 99%

Instability of the southern Canadian Shield during the late Proterozoic

McDannell

Zeitler

Schneider

2018

Earth and Planetary Science Letters

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Cratons are generally considered to comprise lithosphere that has remained tectonically quiescent for billions of years. Direct evidence for stability is mainly founded in the Phanerozoic sedimentary record and low-temperature thermochronology, but for extensive parts of Canada, earlier stability has been inferred due to the lack of an extensive rock record in both time and space. We used 40 Ar/ 39 Ar multi-diffusion domain (MDD) analysis of K-feldspar to constrain cratonic thermal histories across an intermediate (~150-350°C) temperature range in an attempt to link published high-temperature geochronology that resolves the timing of orogenesis and metamorphism with lower-temperature data suited for upper-crustal burial and unroofing histories. This work is focused on understanding the transition from Archean-Paleoproterozoic crustal growth to later intervals of stability, and how uninterrupted that record is throughout Earth's Proterozoic "Middle Age." Intermediate-temperature thermal histories of cratonic rocks at well-constrained localities within the southern Canadian Shield of North America challenge the stability worldview because our data indicate that these rocks were at elevated temperatures in the Proterozoic. Feldspars from granitic rocks collected at the surface cooled at rates of <0.5°C/Ma subsequent to orogenesis, seemingly characteristic of cratonic lithosphere, but modeled thermal histories suggest that at ca. 1.1-1.0 Ga these rocks were still near ~200°Csignaling either reheating, or prolonged residence at mid-crustal depths assuming a normal cratonic geothermal gradient. After 1.0 Ga, the regions we sampled then underwent further cooling such that they were at or near the surface (<< 60°C) in the early Paleozoic. Explaining mid-crustal residence at 1.0 Ga is challenging. A widespread, prolonged reheating history via burial is not supported by stratigraphic information, however assuming a purely monotonic cooling history requires at the very least 5 km of exhumation beginning at ca. 1.0 Ga. A possible McDannell et al.-Late Proterozoic Instability of the Canadian Shield 2 explanation may be found in evidence of magmatic underplating that thickened the crust, driving uplift and erosion. The timing of this underplating coincides with Mid-Continent extension, Grenville orogenesis, and assembly of the supercontinent Rodinia. 40 Ar/ 39 Ar MDD data demonstrate that this technique can be successfully applied to older rocks and fill in a large observational gap. These data also raise questions about the evolution of cratons during the Proterozoic and the nature of cratonic stability across deep time.

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“…Best-fitting splitting parameters are retrieved from the final combined stack, and a 95% confidence interval is calculated by treating the combined stack as a single-event measurement (thus overestimating the errors, but giving a value comparable from station to station). More detail on this procedure is given in Ola et al (2016).…”

Section: Shear-wave Splitting Analysismentioning

confidence: 99%

Altered Mantle Fabric Beneath the Mid‐Continent Rift

Frederiksen

Pokar

Barrow

et al. 2021

Geochem Geophys Geosyst

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We present new, densely sampled shear-wave splitting results from southern Minnesota and adjacent areas of neighboring states, sampling the southwestern limit of the Archean Superior Province and straddling the Proterozoic Mid-Continent Rift (MCR). The new measurements include data from the Earthscope Transportable Array (TA) as well as the Superior Province Rifting Earthscope Experiment (SPREE), yielding 99 new station-averaged measurements. The split times show a consistent decrease from 1.1 s in the NE to 0.2 s in the SW, with the lowest values being associated with the Minnesota River Valley Terrane (MRVT). From modeling and other geophysical constraints, we interpret the split time variations to represent variations in fabric strength within a thick lithosphere, rather than lithospheric thinning or a multi-layered effect, and propose that the weak fabric of the MRVT is associated with a different mechanism of formation than elsewhere in the Superior Province. The fast directions we measure range from NNE-SSW to E-W and vary on a shorter length scale than the split times, with a pattern of NE-SW splits that closely follows the axis of the MCR. We interpret this as a perturbation of the net fast direction due to anisotropy in an underplate along the rift.Plain Language Summary This study presents new measurements of oriented fabric in the Earth's lithosphere, detected from variations in the polarization of seismic waves from distant earthquakes. These results are from southern Minnesota and the surrounding area, combining results from the national grid of Earthscope Transportable Array instruments with a denser deployment of portable instruments. The dense deployment was located so as to examine the Mid-Continent Rift (MCR), a billion-year-old region where stretching of the tectonic plate caused large amounts of volcanic rock to erupt. We found that the strength of fabric was largely unaffected by the MCR, even within the rift's boundaries, and instead varies according to the much older (around two and a half billion years old) regions predating it. The direction of the fabric, however, is influenced by the rift, with a consistent change in orientation that follows the rift axis. We interpret this effect as resulting from a layer of igneous rock that formed at the base of the crust during the rifting process. FREDERIKSEN ET AL.

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Anisotropic zonation in the lithosphere of Central North America: Influence of a strong cratonic lithosphere on the Mid-Continent Rift

Cited by 10 publications

References 67 publications

P Wave Teleseismic Traveltime Tomography of the North American Midcontinent

P Wave Teleseismic Traveltime Tomography of the North American Midcontinent

Instability of the southern Canadian Shield during the late Proterozoic

Altered Mantle Fabric Beneath the Mid‐Continent Rift

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