Geologic transect across the Grenville orogen of Ontario and New York

Youngest crustal age domains (>1.3 Ga; Composite Arc Belt and Adirondacks-Frontenac) are restricted to pericratonic arcs assembled and accreted to Laurentia between ca.1.25 and 1.16 Ga during the Elzevirian and Shawinigan orogenies.

“Youngest crustal age domains (>1.3 Ga; Composite Arc Belt and Adirondacks-Frontenac; Fig. 1b) are restricted to pericratonic arcs assembled and accreted to Laurentia between ca.1.25 and 1.16 Ga during the Elzevirian and Shawinigan orogenies (Carr et al. 2000;Rivers et al. 2012; see also Corriveau and van Breemen 2000 for an alternative interpretation).”

The rest of the high-T magmatism, together with the Geon 11 AMCGs, is associated in space to formerly pericratonic arc/backarc systems: the Adirondack-Frontenac and Composite Arc belts that were assembled and accreted to Laurentia at ca. 1.22-1.16Ga, and Quebecia that represents rifting of the Laurentian margin and re-amalgamation of pericratonic slivers at ca. 1.50-1.38Ga.

“The rest, together with the Geon 11 AMCGs, is associated in space to formerly pericratonic arc/backarc systems: the Adirondack-Frontenac and Composite Arc belts that were assembled and accreted to Laurentia at ca. 1.22-1.16Ga (e.g., Carr et al. 2000), and”

With respect to the tectonic subdivision of Carr et al. (2000), the Parautochthonous, HP, and LP belts are all components of their 'Laurentia and Laurentian Margin.'

“With respect to the tectonic subdivision of Carr et al. (2000), the Parautochthonous, HP, and LP belts are all components of their 'Laurentia and Laurentian Margin.'”

The Frontenac-Adirondack belt and contiguous parts of the Composite Arc belt carry evidence for penetrative deformation and greenschist- to granulite-facies metamorphism at 1190-1140 Ma (Shawinigan orogeny), suggesting that they were amalgamated at that time.

“The Frontenac-Adirondack belt and contiguous parts of the Composite Arc belt carry evidence for penetrative deformation and greenschist- to granulite-facies metamorphism at 1190-1140 Ma (Shawinigan orogeny), suggesting that they were amalgamated at that time (Carr et al. 2000; Hanmer et al. 2000).”

Carr et al. (2000) subdivided the Allochthonous Monocyclic belt of Rivers et al. (1989) into the 'Composite Arc belt' and the 'Frontenac-Adirondack belt.'

“Carr et al. (2000) subdivided the Allochthonous Monocyclic belt of Rivers et al. (1989) into the 'Composite Arc belt' and the 'Frontenac-Adirondack belt.'”

The current geometry of the Composite Arc belt reflects principally thrusting and extension at c. 1080-1050 Ma.

“However, the current geometry of the belt reflects principally thrusting and extension at c45 1080-1050 Ma (Timmermann et al. 1997; Carr et al. 2000).”

The boundary between the Composite Arc belt and the structurally underlying units is a map-scale tectonic mélange referred to as the Composite Arc boundary thrust zone.

“The boundary between the Composite Arc belt and the structurally underlying units is a map-scale tectonic mélange referred to here as the Composite Arc boundary thrust zone (Fig. 2; formerly Central Metasedimentary Belt boundary thrust zone, Hanmer and Ciesielski 1984; renamed to be consistent with renaming of Central Metasedimentary belt to Composite Arc belt by Carr et al. 2000).”

Metamorphism in most of the Composite Arc belt took place during the Elzevirian orogeny, and metamorphism in the Frontenac part of the Frontenac-Adirondack belt took place in the Shawinigan orogeny.

“Structurally up-section to the south, metamorphism in most of the Composite Arc belt took place during the Elzevirian orogeny (except for the basal Composite Arc boundary thrust zone, noted earlier, and Mazinaw domain, which record late Ottawan ages of metamorphism, Corfu and Easton 1995), and metamorphism in the Frontenac part of the Frontenac-Adirondack belt took place in the Shawinigan orogeny”

The pre-1300 Ma history of the Laurentian margin is absent in the Composite Arc and Frontenac-Adirondack belts.

“This pre-1300 Ma history of the Laurentian margin is absent in the Composite Arc and Frontenac-Adirondack belts (see also, e.g., Wodicka et al. 1996; Culshaw et al. 1997; Carr et al. 2000).”

The Parautochthonous, HP, and LP belts were (semi-)contiguous components of the southeastern margin of Laurentia during the Mesoproterozoic prior to the Grenvillian collision.

“We therefore infer, with Carr et al. (2000), that the Parautochthonous, HP, and LP belts were (semi-)contiguous components of the southeastern margin of Laurentia during the Mesoproterozoic prior to the Grenvillian collision.”

Earlier pre-Grenvillian and Grenvillian orogenic activity includes offshore(?) imbrication of the components of the Composite Arc belt during the c45 1250-1220 Ma Elzevirian orogeny, and imbrication of the Composite Arc belt with the Frontenac-Adirondack belt during the c45 1190-1140 Ma Shawinigan orogeny.

“Other earlier pre-Grenvillian and Grenvillian orogenic activity not shown in the figure includes the offshore(?) imbrication of the components of the Composite Arc belt during the c45 1250-1220 Ma Elzevirian orogeny, and imbrication of the Composite Arc belt with the FrontenacAdirondack belt during the c45 1190-1140 Ma Shawinigan orogeny (Carr et al. 2000).”

The province-wide Ottawa orogeny was a result of continent-continent collision.

“If the province-wide Ottawa orogeny was a result of continent-continent collision, as is commonly inferred (e.g., McLelland et al. 1996, 2001; Rivers 1997; Carr et al. 2000)”