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Abstract

This paper presents a plate-scale model for the Precambrian growth and evolution of the North American continent. The core of the North American continent (Canadian shield) came together in the Paleoproterozoic (2.0-1.8 Ga) by plate collisions of Archean continents (Slave with Rae-Hearne, then Rae-Hearne with Superior) as well as smaller Archean continental fragments (Wyoming, Medicine Hat, Sask, Marshfi eld, Nain cratons). The resulting Trans-Hudson orogen was a collisional belt similar in scale to the modern Himalayas. It contains mainly reworked Archean crust, but remnants of juvenile volcanic belts are preserved between Archean masses. The thick, buoyant, and compositionally depleted mantle lithosphere that now underlies North America, although dominantly of Archean age, took its present shape by processes of collisional orogenesis and likely has a scale of mantle heterogeneity similar to that exhibited in the overlying crust.In marked contrast, lithosphere of southern North America (much of the conti nental United States) was built by progressive addition of a series of dominantly juvenile vol canic arcs and oceanic terranes accreted along a long-lived southern (present coordinates) plate margin. Early juvenile additions ( Pembine-Wausau, Elves Chasm arcs) formed at the same time (1.84-1.82 Ga) the core was assembling. Following fi nal assembly of the Archean and Paleoproterozoic core of North America by 1.8 Ga, major accretionary provinces (defi ned mainly by isotopic model ages) were added by arc-continent accretion, analogous to present-day convergence between Australia and Indonesia. Also similar to Indonesia, some accreted terranes contain older continental crustal material [Archean(?) Mojavia], but the extent and geometry of older crust are not well known. Accretion-ary provinces are composed of numerous 10 to 100 km scale terranes or blocks, separated by shear zones, some of which had compound histories as terrane sutures and later crustalassembly structures. Major northeast-trending provinces are the Yavapai province (1.80-1.70 Ga), welded to North America during the 1.71-1.68 Ga Yavapai orogeny; the Mazatzal province (1.70-1.65 Ga), added during the 1.65-1.60 Ga Mazatzal orogeny; the Granite-Rhyolite province (1.50-1.30 Ga), added during the 1.45-1.30 Ga tectonic event associated with A-type intracratonic magmatism; and the Llano-Grenville province (1.30-1.00 Ga), added during the 1.30-0.95 Ga broader Grenville orogeny. During each episode of addition of juvenile lithosphere, the transformation of juvenile crust into stable continental lithosphere was facilitated by voluminous granitoid plutonism that stitched new and existing orogenic boundaries. Slab roll back created transient extensional basins (1.70 and 1.65 Ga) in which Paleoproterozoic quartziterhyolite successions were deposited, then thrust imbricated as basins were inverted.The lithospheric collage that formed from dominantly juvenile terrane accretion and stabilization (1.8-1.0 Ga) makes up about half of the present-day North American con...

Rocky Mountain evolution: Tying Continental Dynamics of the Rocky Mountains and Deep Probe seismic experiments with receiver functions

“…The Jemez lineament is an alignment of Miocene and younger volcanic centers and geologic features that extends from east central Arizona to northeastern New Mexico (Figure 1) [e.g., Aldrich, 1986], and it aligns with the structural grain of the Precambrian basement in the region [e.g., Gilbert et al, 2007]. It also lies in an area thought to be a transition zone between the Yavapai and Mazatzal terranes [e.g., Whitmeyer and Karlstrom, 2007].…”

Age and isotopic geochemical characteristics of Archean carbonatites and alkaline rocks of the Baltic shield

“…Each episode of addition of juvenile crust and its transformation into stable continental crust was facilitated by voluminous granitoid plutonism that stitched new and previously existing orogenic boundaries. Slab rollback created transient extensional basins (1.70 and 1.65 Ga), where Palaeoproterozoic quartzite-rhyolite successions were deposited [Whitmeyer, Karlstrom, 2007]. Between 1.73 and 1.48 Ga, the accretionary crustal growth along the southwestern edge of the East European Craton (EEC) was directed toward the west.…”

A rootless rockies—Support and lithospheric structure of the Colorado Rocky Mountains inferred from CREST and TA seismic data

“…[38] Similarly, we interpret the E-NE trending lineament of thickened crust traversing southern Colorado and northern New Mexico as a crustal welt left from the suturing of the Proterozoic Yavapai and Mazatzal provinces [e.g., Whitmeyer and Karlstrom, 2007]. The location of the exact suture is uncertain [see Shaw and Karlstrom, 1999], and other workers have suggested the main suturing occurred further south along the Jemez lineament in New Mexico [Magnani et al, 2004].…”

“…Since the late Cretaceous, this region has risen from sea level to an average elevation of about 3 km; the zenith of a long-wavelength ($1000 km) epeirogenic swell and the largest regional-scale topographic anomaly in North America [Eaton, 2008]. This N-S trending feature cuts across the grain of ancient structural features, including northeast trends associated with the Proterozoic accretion of the Colorado Province [Reed et al, 1987;Whitmeyer and Karlstrom, 2007] and northwest trends associated with the formation of the Ancestral Rocky Mountains [Kluth and Coney, 1981]. In addition to their topographic prominence, the CRM displays a long-wavelength Bouguer gravity low reaching À330 mGal, elevated surface heat flow up to 100 mW/m 2 [Decker, 1995;Reiter, 2008], and reduced seismic velocities in the crust and upper mantle [e.g., Schmandt and Humphreys, 2010;Shen et al, 2013].…”