Laurentia: Turning Points in the Evolution of a Continent
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The North American continent has a rich record of the tectonic environments and processes that occur throughout much of Earth history. This Memoir focuses on seven “turning points” that had specific and lasting impacts on the evolution of Laurentia: (1) The Neoarchean, characterized by cratonization; (2) the Paleoproterozoic and the initial assembly of Laurentia; (3) the Mesoproterozoic southern margin of Laurentia; (4) the Midcontinent rift and the Grenville orogeny; (5) the Neoproterozoic breakup of Rodinia; (6) the mid-Paleozoic phases of the Appalachian-Caledonian orogen; and (7) the Jurassic–Paleogene assembly of the North American Cordillera. The chapters in this Memoir provide syntheses of current understanding of the geologic evolution of Laurentia and North America, as well as new hypotheses for testing.
Paleoproterozoic Earth and the transition toward modern tectonic processes: A synopsis Available to Purchase
*Corresponding author: [email protected]; retired; Geological Survey of Canada.
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Published:January 23, 2023
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CitationD. Corrigan*, D. Van Rooyen, 2023. "Paleoproterozoic Earth and the transition toward modern tectonic processes: A synopsis", Laurentia: Turning Points in the Evolution of a Continent, Steven J. Whitmeyer, Michael L. Williams, Dawn A. Kellett, Basil Tikoff
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ABSTRACT
Many of the hallmarks of modern plate-tectonic processes first occurred in the Paleoproterozoic Era, indicating that the mechanical, thermal, and compositional parameters of Earth’s lithosphere had evolved to approximately modern ranges of values by that time. The core of Laurentia preserves widespread examples of both convergent and divergent tectonic processes in the time span from 2.2 to 1.7 Ga, particularly within the Trans-Hudson composite orogen. Large continental masses or supercontinents previously accreted during the Neoarchean Era began to break up between 2.4 and 2.0 Ga, leading to the deposition of widespread passive-margin sedimentary prisms and locally voluminous emplacement of mafic magma in radiating dike swarms. Further rifting and drifting led to the formation of incipient (e.g., Bravo Formation) to fully developed oceanic crust (e.g., Manikewan Ocean). Plate convergence beginning ca. 1.92 Ga heralded the demise of the Manikewan Ocean ~150 m.y. after its postulated opening. Protracted subduction of oceanic lithosphere over a period of ~90 m.y. produced a series of island arcs, some of which (Lynn Lake, Flin Flon, Snow Lake) host world-class volcanogenic massive sulfide (VMS) ± Au deposits. Plate convergence also led to progressive southeastward (present-day coordinates) accretion of microplates on a pre-amalgamated core consisting of the Slave craton and the Rae and Hearne “Provinces,” forming the Churchill plate. Following the formation of the Churchill plate collage ca. 1.86 Ga, subduction of oceanic lithosphere organized along an ~4000-km-long, north-dipping subduction zone along the southeastern edge of the Churchill plate, producing voluminous continental arc magmas in an Andean-type setting. The final phase of tectonic evolution involved collision of the Superior and North Atlantic cratons with the Churchill plate and intervening juvenile oceanic arc terranes. That phase was strongly influenced by the irregular shape of the indenting Superior craton, favoring the development of oroclines and leading to escape tectonics and lateral extrusion of continental microplates. For the most part, the Trans-Hudson was a hot but not necessarily thick orogen, perhaps reflecting a higher geothermal gradient during the Paleoproterozoic Era.
- Archean
- Canada
- crust
- Flin Flon Manitoba
- geothermal gradient
- heat flow
- island arcs
- Laurentia
- lithosphere
- Lynn Lake Manitoba
- mafic magmas
- magmas
- Manitoba
- mechanics
- Neoarchean
- oceanic crust
- oceanic lithosphere
- Paleoproterozoic
- passive margins
- plate tectonics
- Precambrian
- Proterozoic
- sediments
- Snow Lake Manitoba
- subduction
- supercontinents
- tectonics
- terranes
- upper Precambrian
- Western Canada
- Trans-Hudson Orogeny
- Manikewan Ocean
- Bravo Formation