P‐wave tomography of eastern North America: Evidence for mantle evolution from Archean to Phanerozoic, and modification during subsequent hot spot tectonism

Abstract

The unique physical and chemical properties of cratonic lithosphere are thought to be key to its long‐term survival and its resistance to pervasive modification by tectonic processes. Study of mantle structure in southeast Canada and the northeast US offers an excellent opportunity to address this issue because the region spans 3 billion years of Earth history, including Archean formation of the Superior craton and younger accretion of terranes to eastern Laurentia during the Proterozoic Grenville and Phanerozoic Appalachian orogenies. Trending NW–SE through each of these terranes is the track of the Great Meteor hot spot, which affected the region during the Mesozoic. Here we study mantle seismic velocity structure beneath this region of eastern North America using tomographic inversion of teleseismic P‐wave relative arrival‐times recorded by a large‐aperture seismograph network. There are no large‐scale systematic differences between Superior and Grenville mantle wave speed structure, which may suggest that tectonic stabilization of cratons occurred in a similar fashion during the Archean and Proterozoic. Cratonic lithosphere is largely thought to be resistant to modification by hot spot processes, in contrast to younger terranes where lithospheric erosion and significant magmatism are expected. Low velocities beneath the regions affected by the Great Meteor hot spot are broadest beneath the Paleozoic Appalachian terranes, indicating pervasive modification of the lithosphere during magmatism. The zone of modification narrows considerably into the Proterozoic Grenville province before disappearing completely in the Archean Superior craton, where the surface signature of Mesozoic magmatism is limited to kimberlite eruptions.

Seismic anisotropy of Precambrian lithosphere: Insights from Rayleigh wave tomography of the eastern Superior Craton

“…The most recent tectonic event that affected parts of the southern Superior Craton is the passage of the North American plate over the Great Meteor hot spot track at ∼190–110 Ma ago (Figure ). The hot spot may have refertilized the mantle [e.g., Frederiksen et al , ; Boyce et al , ] in the southern section of the study region, consistent with the negative velocity anomalies we observe at all periods in our model (Figure ) also detected in some regional [e.g., Frederiksen et al , ; Villemaire et al , ; Boyce et al , ] and continental scale models [e.g., French et al , ]. The thermal impact associated with a mantle plume head can be as high as ∼500°C, which will rapidly diffuse and decay to ∼80°C at 200 km over 120 Ma [ Eaton and Frederiksen , ].…”

P and S wave tomography of the mantle beneath the United States

“…At the same depth the northern Appalachian anomaly is about 400 km wide and it underlies Massachusetts, Vermont, and New Hampshire (Figure ). The northern feature was previously reported by tomography studies with the sparse data coverage that existed prior the arrival of USArray in the northeastern U.S. [ Eaton and Frederiksen , ; Villemaire et al , ]. Both the central and northern Appalachian anomalies widen at depths of 125–200 km, and it is unknown whether these features extend offshore beneath the Atlantic Ocean.…”

“…Alternatively, smallscale upper mantle convection and volcanism may be organized by proximity to the edge of the cold tectospheric root landward of the Precambrian rift margin [e.g., King, 2007]. Localized mantle upwelling during hot spot volcanism in the Cretaceous may also have modified the passive margin lithosphere in the Cretaceous and influence present-day mantle heterogeneity [Heaman and Kjarsgaard, 2000;Eaton and Frederiksen, 2007;Villemaire et al, 2012;Chu et al, 2013].…”

Precambrian Plate Tectonics in Northern Hudson Bay: Evidence From P and S Wave Seismic Tomography and Analysis of Source Side Effects in Relative Arrival‐Time Data Sets

“…We can thus safely interpret structure in the upper 500 km of the full model. Parameterizing tomographic models deeper than the resolving power of the teleseismic data set is common (e.g., Vandecar et al, ; Villemaire et al, ). Our work demonstrates that this approach is particularly important for large aperture (>1,000 km) networks.…”