Exhumation of a collisional orogen: A perspective from the North American Grenville Province

Abstract

Combined structural and geochronologic research in the southernmost portion of the contiguous Grenville Province of North America (Ontario and New York State)show protracted periods of extension after the last episode of contraction. The Grenville Province in this area is characterized by synorogenic extension at ca. 1040 Ma, supported by U-Pb data on titanites and 40 Ar-39 Ar data on hornblendes, followed by regional extension occurring along crustal-scale shear zones between 945 and 780 Ma, as recorded by 40 Ar-39 Ar analysis of hornblende, biotite, and K-feldspar. By ca. 780 Ma the southern portion of the Grenville Province, from Ontario to the Adirondack Highlands, underwent uplift as a uniform block. Tectonic hypotheses have invoked various driving mechanisms to explain the transition from compression to extension; however, such explanations are thus far geodynamically unconstrained. Numerical models indicate that mechanisms such as gravitational collapse and mantle delamination act over timescales that cannot explain a protracted 300 m.y. extensional history that is contemporaneous with ongoing uplift of the Grenville Province. Rather, the presence of a plume upwelling underneath the Laurentian margin, combined with changes in regional stress directions, permitted the observed uplift and extension in the Grenville Province during this time. The uplift history, while on a slightly different timescale from those of most plume models, is similar to that seen in models of uplift and extension caused by the interaction of a plume with the base of the lithosphere. Some of the protracted extension likely reflects the contribution of farfield effects, possibly caused by tectonic activity in other cratons within the Rodinian supercontinent, effectively changing the stress distributions in the Grenville Province of northeastern North America.

The Grenville orogenic cycle of southern Laurentia: Unraveling sutures, rifts, and shear zones as potential piercing points for Amazonia

“…The rapid cooling from 1050-1020 Ma (Alcock et al, 2004) and 7-km-uplift of the Adirondack Highlands-core (Johnson et al, 2004), relative to the slow cooling from 1080-900 Ma (Dahl et al, 2004) and extension from 945-780 Ma (Streepey et al, 2004) of the Frontenac terrane between the CCSZ and RLSZ is comparable to uplift and exhumation rates of metamorphic core-complexes in the Basin and Range Province (e.g., Crittenden et al, 1980;Anderson, 1988Anderson, , 1990Anderson et al, 1992;Wernicke et al, 1987;Wernicke, 1992), suggesting a similar process (e.g., inclined isotherm model of Dahl et al (2004)) may have occurred in the Grenville orogen during the Rigolet phase. Normal displacement across the Ramapo fault during the late Grenville orogeny was also noted by Costa and Gates (1993) and Gates and Costa (1998) in the New Jersey Highlands.…”

“…Streepey et al (2001Streepey et al ( , 2002 placed termination of extension on the CCSZ at 945 Ma and that on the RLSZ after 900 Ma. Streepey et al (2004) suggested that the uplift could be related to a plume, based on modeling, whereas Dahl et al (2004) favored Iapetan rifting. However, other evidence suggests that the extension and uplift may be very widespread (Fig.…”

“…Thus, the extension is (Krogh, 1984). Blue arrows show extension along the Carthage-Colton shear zone (CCSZ) (Johnson et al, 2004) and Robertson Lake shear zone (RLSZ) (e.g., Streepey et al, 2002Streepey et al, , 2004, along the Ramapo fault in New Jersey (e.g., Costa and Gates, 1993;Gates and Costa, 2006), and inferred from seismic lines across both Ohio (Pratt et al, 1989), and eastern Tennessee (Hopkins, 1995). BG -biotite gneiss (Tollo et al, 2006); AMS -Archer Mountain Suite (e.g., Hughes et al, 2004;unpublished preliminary age: B.V. Miller and M.J. Bartholomew); LA -Labrieville Anorthosite (e.g., Owens and Dymek, 1992;Owens et al, 1994); LAMLac Michel Complex Erdmer, 1990, 1986;Heaman et al, 2002); AMCG -anorthosite-mangerite-charnockite-granite suite; LM -Lovingston massif (Bartholomew and Lewis, 1984); MA -Montpelier Anorthosite (Owens and Samson, 2004;Aleinikoff et al, 1996); MEG -Mount Eve granite (Gorring et al, 2004); PM -Pedlar massif (Bartholomew and Lewis, 1984); RA and RMP -Roseland Anorthosite and Roses Mill pluton (e.g., Herz and Force, 1987; unpublished preliminary ages: B.V. Miller and M.J. Bartholomew); Oaxaquia metamorphism (m) (e.g., Cameron et al, 2004;Keppie et al, 2003Keppie et al, , 2004 widespread and associated with the rapid rise of hot, metamorphic cores (e.g., the Adirondacks) -again analogous to the Basin and Range province and associated metamorphic core-complexes.…”

“…Many volumes are devoted to the Grenville province of Canada and its extension into the Adirondacks Mountains of New York (e.g., Buddington, 1939;Thomson, 1956;Isachsen, 1969;Moore et al, 1986;Hynes and Ludden, 2000;Wardle and Hall, 2002), as well as to the Grenvillian massifs within the Appalachians ( Bartholomew, 1984) and mid-continent region, as well as recently to the entire Grenville orogen of North America (Tollo et al, 2004c). These volumes punctuate periods of new-data acquisition and are generally followed by (or may contain) review papers (e.g., Moore, 1986;Easton, 1986;Rankin et al, 1993;Davidson, 1998), palinspastic reconstructions Lewis, 1988, 1992;Culshaw et al, 1997), tectonic syntheses (e.g., Wynne-Edwards, 1972;Baer, 1974;Davidson, 1986Davidson, , 1995Rivers et al, 1989;Gower, 1996;Rivers, 1997) or tectonic models (e.g., Windley, 1986;Streepey et al, 2004). To decipher potential piercing points along the Iapetan rifted-margin for potential correlation with Amazonia, we need to know: (1) the different types of rocks that form this orogen; (2) the different times of plutonism and tectonism versus sedimentation; (3) the identification of accreted 0895-9811/$ -see front matter Ó 2009 Elsevier Ltd. All rights reserved.…”

Tectonic Setting and Evolution of the Grenville Orogen: An Assessment of Progress Over the Last 40 Years

“…Recognition of the orogenic lid and its tectonic juxtaposition with exhumed mid crust along normal sense shear zones provided evidence for the crustal scale of orogenic collapse and permitted integration of the robust, but previously stranded 'old' 40 Ar/ 39 Ar data (e.g. Reynolds 1989;Cosca et al 1991Cosca et al , 1992Cosca et al , 1995Corrigan and van Breemen 1997;Streepey et al 2004;Selleck et al 2005) into a coherent tectonic model. The lid was subsequently named the Ottawan Orogenic Lid (OOL) by Rivers (2012).…”