Middle Proterozoic age for the Montpelier Anorthosite, Goochland terrane, eastern Piedmont, Virginia

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

“…Significant new geochronologic and isotopic studies in the Grenvillian massifs of the Appalachians (e.g., Aleinikoff et al, 1996Aleinikoff et al, , 2000Aleinikoff et al, , 2004Bream et al, 2004;Hatcher et al, 2004;Heatherington et al, 1996;Owens and Samson, 2004;Ownby et al, 2004;Pettingill et al, 1984;Sinha et al, 1996;Tollo et al, 2004aTollo et al, ,b, 2006, and in the Adirondacks and New England massifs (e.g., Alcock et al, 2004;Hamiton et al, 2004;McLelland et al, 2004;Sinha and McLelland, 1999;Walsh et al, 2004) during the last two decades, have focused on the similarities between the Adirondacks and Appalachian massifs. These studies show that they shared Grenvillian magmatic, deformational, and metamorphic events during the Shawinigan, Ottawan, and Rigolet phases of Grenvillian orogenesis.…”

“…terranes), and the terranes of the Llano uplift (e.g., Mosher, 1998;Mosher et al, 2004) formed and/or were accreted to Laurentia during the Shawinigan phase of Grenvillian orogensis. Extensive magmatism, including anorthosite-mangerite-charnockite-granite (AMCG), occurred within the interior magmatic belt along the length of the Canadian Grenville province and Adirondacks (e.g., Rivers, 1997) as well as in the Blue Ridge terrane (e.g., Aleinikoff et al, 1996Aleinikoff et al, , 2000Tollo et al, 2004a,b) Many parts of these Appalachian Grenvillian massifs were subsequently fragmented during the breakup of Rodinia and later reaccreted as micro-continents or parts of larger terranes during the Paleozoic development of the Appalachians. These include the Goochland terrane and the Tugaloo terrane, both of which contain basement fragments (Carrigan et al, 2003;Hatcher et al, 2004).…”

“…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 BG -biotite gneiss (Tollo et al, 2006); AMS -Archer Mountain Suite (e.g., Hughes et al, 2004;unpublished preliminary age: B.V. Miller and M.J. Bartholomew); LA -Labrieville Anorthosite (e.g., Owens and Dymek, 1992;Owens et al, 1994); LAMLac Michel Complex Erdmer,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. AMCG magmatism and metamorphism in Oaxaquia during the Rigolet phase (e.g., Mora et al, 1986;Cameron et al, 2004;Keppie et al, 2003Keppie et al, , 2004 suggest similar extension there, although Oaxaquia's location relative to Laurentia at that time is unknown and is only diagrammatically depicted in Fig.…”

Strain and vorticity analysis of transpressional high-strain zones from the Virginia Piedmont, USA

“…An areally extensive biotite-rich gneiss crops out SE of the SHSZ. At many locations the gneiss is pelitic (with kyanite + sillimanite) and may correlate with the Maidens gneiss of the Proterozoic Goochland terrane (Farrar 1984;Aleinikoff et al 1996). The biotite-rich gneiss is interlayered with amphibolite-rich gneiss and intruded by a suite of granodioritic pegmatites.…”

“…An unresolved controversy in southern Appalachian tectonics concerns the origin of the Goochland terrane. Mesoproterozoic rocks and A-type Neoproterozoic granitoids of the Goochland terrane are similar to native Laurentian rocks in the Virginia Blue Ridge and have led many workers to conclude that the Goochland terrane is of Laurentian origin (Farrar 1984;Glover et al 1989;Aleinikoff et al 1996;Owens & Tucker 2000). Others suggest the Goochland terrane may be of peri-Gondwanan affinity and was accreted to Laurentia during the Appalachian orogen (Rankin et al 1989;Hibbard & Samson 1995).…”