Detrital zircon ages were determined for conglomerate and sandstone samples from six fault-bounded belts in New Brunswick and coastal Maine. Formations sampled included the Martinon (Brookville belt), Flagg Cove (Grand Manan Island belt), Matthews Lake (New River belt), Ellsworth (Ellsworth belt), Calais (St. Croix belt), and Baskahegan Lake (Miramichi belt). Their maximum age of deposition is based on the youngest detrital zircon population and minimum age of deposition based on stratigraphic, paleontological, and cross-cutting intrusive relationships. The determined range of depositional ages are: Martinon between 602 ± 8 (youngest zircons) and 546 ± 2 Ma (age of cross-cutting intrusion); Flagg Cove between 574 ± 7 (youngest zircons) and 535 ± 3 Ma (age of cross-cutting intrusion); Matthews Lake between 539 ± 5 (youngest zircons) and 514 ± 2 Ma (age of overlying volcanic rocks); Ellsworth between 507 ± 6 (youngest zircons) and 504 ± 3 Ma (age of overlying volcanic rocks); Calais between 510 ± 8 (youngest zircons) and 479 ± 2 Ma (graptolite zone); and Baskahegan Lake between 525 ± 6 (youngest zircons) and 488 ± 2 Ma (graptolite zone).All samples are dominated by Neoproterozoic (Gondwanan) zircon populations. The Early Paleozoic Matthews Lake, Ellsworth, and Calais formations contain main population peaks at 539 ± 5 Ma, 545 ± 4 Ma, and 556 ± 7 Ma, respectively, consistent with derivation mainly from magmatic rocks of the Brookville, Grand Manan Island, and/or New River belts, previously dated at ~553 to ~528 Ma. In contrast, the main peak in the Early Paleozoic Baskahegan Lake Formation is older at 585 ± 5 Ma. The main peak in the Neoproterozoic to Early Cambrian Flagg Cove Formation is at 611 ± 7 Ma with a secondary peak at 574 ± 7 Ma; the former was likely derived from locally exposed igneous units dated at ~618 to ~611 Ma. The Neoproterozoic Martinon Formation exhibits dominant peaks at 674 ± 8 Ma and 635 ± 4 Ma. Ganderian basement gneiss dated at ~675 Ma and intruded by plutonic rocks dated at ~584 Ma in the Hermitage Flexure of Newfoundland are possible sources for these older zircon components in the Martinon and Baskahegan Lake formations. Plutonic rocks in the New River belt dated at ~629 to ~622 Ma may be the source of the younger component in the Martinon Formation.The samples also contain a small number of Mesoproterozoic, Paleoproterozoic, and Archean zircon grains, the latter as old as 3.23 Ga. The presence of zircons in the range 1.07 to 1.61 Ga is consistent with an origin along the periGondwanan margin of Amazonia rather than West Africa. The general similarity of zircon provenance for samples from New Brunswick and coastal Maine suggests that all the Ganderian belts were part of a single microcontinent rifted from the Amazonian craton.The Grand Manan Island and New River belts both record two distinct periods of Neoproterozoic arc magmatism (~629 to ~611 Ma and at ~553 to ~535 Ma) whereas the Brookville belt experienced only a single period of arc magmatism lasting from ~553 to ~528 Ma. ...

Detrital zircon ages from the lower part of the Late Proterozoic(?) to Middle Cambrian Goldenville Group in the Meguma terrane of Nova Scotia suggest derivation from local sources in the Avalonian and Pan-African orogens on the margins of Early Cambrian Gondwana. Samples from near the top of the group show a broader distribution, including ages back to Archean. The εNd data show a corresponding trend, from slightly positive in the lower Goldenville Group to highly negative in the upper Goldenville Group and overlying Upper Cambrian to Lower Ordovician Halifax Group. The trends are consistent with deposition of the lower part of the Meguma succession in a rift, in which uplifted rift-flanks were the main source of the early basin fill, whereas subsequent thermal subsidence of rift margins allowed for more widespread sediment sourcing in younger units. The rift was possibly located between Gondwana and Avalonia, and may have been the locus for separation of Avalonia from Gondwana to form part of the Rheic Ocean.

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Late Precambrian volcanic, sedimentary, and plutonic belts in southeastern Cape Breton Island display differences in rock types, petrochemistry, and age. The oldest rocks are 680 Ma mafic and felsic flows and tuffs, and abundant, mainly tuffaceous, sedimentary rocks in the Stirling Group. They are interpreted to have formed in a trough within or peripheral to a volcanic arc complex. Northwest of the Stirling Group, the East Bay Hills, Coxheath, and Pringle Mountain groups consist of ca. 620 Ma mafic to felsic subaerial pyroclastic rocks and flows and contemporaneous dioritic to granitic plutons. Both volcanic and plutonic rocks are calc-alkalic to high-K calc-alkalic suites, formed in a continental margin volcanic arc. A correlative 620 Ma plutonic suite intruded the western margin of the Stirling Group, and subduction at that time may have been toward the present southeast. The ca. 575 Ma Fourchu Group and laterally equivalent and/or overlying Main-à-Dieu Group are significantly younger than the other groups. Together with co-genetic granitic plutons, they appear to represent a less evolved calc-alkalic to low-K continental margin volcanic arc and associated intra-arc basin formed above a northwest-dipping subduction zone. These Precambrian rocks are overlain in some areas by latest Precambrian through Cambrian clastic sedimentary rocks. The various volcanic-sedimentary belts were juxtaposed by lateral movements along major faults in the Late Precambrian to form this part of the Avalon composite terrane.

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The Caledonian Highlands of southern New Brunswick consist dominantly of Late Neoproterozoic rocks generally considered typical of the Avalon terrane of the northern Appalachian Orogen. Mainly tuffaceous metavolcanic and metasedimentary rocks of the Broad River Group and cogenetic dioritic to granitic plutons with ages ca. 620 Ma form most of the eastern Caledonian Highlands. The igneous rocks have petrological features indicative of origin in a continental-margin subduction zone. Tuffaceous metasedimentary rocks in the group host the Teahan and Lumsden Cu-Pb-Zn-Ag-Au deposits. Significantly younger (ca. 560-550 Ma) volcanic and clastic sedimentary rocks of the Coldbrook Group form most of the western highlands, and occur locally throughout the highlands. The mainly tuffaceous lower part of the group has been intruded by gabbroic and syenogranitic plutons that are interpreted to be cogenetic with basaltic and rhyolitic flows in the upper part of the group. This voluminous continental magmatism may have occurred during extension within the earlier subduction zone complex represented by the Broad River Group and associated plutons. The Broad River Group was deformed, regionally metamorphosed to greenschist facies, and locally mylonitized prior to deposition of the unconformably overlying Coldbrook Group. Both units were folded and slightly metamorphosed, probably during the Silurian and Devonian. This event may have been related to juxtaposition with terranes to the northwest. Subsequent mid- to late Paleozoic mylonitization, thrusting, and brittle faulting may have been related to initiation of the Maritimes Basin, and to movement along the Avalon Meguma terrane boundary to the south and east.