Investigating the Boundaries of the Southeastern New England Avalon Terrane: New La-Icp-MS U-Pb Zircon Dates From Igneous and Metasedimentary Rocks

Ellison, Sonia; Kuiper, Yvette D.; Crowley, Jim; Murray, Daniel P.

doi:10.1130/abs/2020se-345455

Cited by 4 publications

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“…1C; Zartman and Hermes, 1987) yielded highly discordant zircon with Archean upper intercept ages. All other analyzed Ediacaran to Devonian igneous rocks in the Avalon terrane of southeastern New England do not show inheritance that is significantly older than the age of crystallization (Zartman and Naylor, 1984;Zartman, 1985, 1992;Zartman et al, 1988;Thompson and Hermes, 2003;Thompson et al, 1996Thompson et al, , 2010aThompson et al, , 2010bEllison et al, 2020).…”

Section: The Southeastern New England Avalon Terranementioning

confidence: 94%

Supplemental Material: U-Pb detrital zircon analysis of sedimentary rocks of the southeastern New England Avalon terrane in the U.S. Appalachians: Evidence for a separate crustal block

Kuiper¹,

al.²

2022

Preprint

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Section: The Southeastern New England Avalon Terranementioning

confidence: 94%

Supplemental Material: U-Pb detrital zircon analysis of sedimentary rocks of the southeastern New England Avalon terrane in the U.S. Appalachians: Evidence for a separate crustal block

Kuiper¹,

al.²

2022

Preprint

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U-Pb detrital zircon analysis of sedimentary rocks of the southeastern New England Avalon terrane in the U.S. Appalachians: Evidence for a separate crustal block

Kuiper

Murray

Ellison

et al. 2022

New Developments in the Appalachian-Caledonian-Variscan Orogen

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The Avalon terrane of southeastern New England is a composite terrane in which various crustal blocks may have different origins and/or tectonic histories. The northern part (west and north of Boston, Massachusetts) correlates well with Avalonian terranes in Newfoundland, Nova Scotia, and New Brunswick, Canada, based on rock types and ages, U-Pb detrital zircon signatures of metasedimentary rocks, and Sm-Nd isotope geochemistry data. In the south, fewer data exist, in part because of poorer rock exposure, and the origins and histories of the rocks are less well constrained. We conducted U-Pb laser ablation–inductively coupled plasma–mass spectrometry analysis on zircon from seven metasedimentary rock samples from multiple previously interpreted subterranes in order to constrain their origins. Two samples of Neoproterozoic Plainfield Formation quartzite from the previously interpreted Hope Valley subterrane in the southwestern part of the southeastern New England Avalon terrane and two from the Neoproterozoic Blackstone Group quartzite from the adjacent Esmond-Dedham subterrane to the east have Tonian youngest detrital zircon age populations. One sample of Cambrian North Attleboro Formation quartzite of the Esmond-Dedham subterrane yielded an Ediacaran youngest detrital zircon age population. Detrital zircon populations of all five samples include abundant Mesoproterozoic zircon and smaller Paleoproterozoic and Archean populations, and are similar to those of the northern part of the southeastern New England Avalon terrane and the Avalonian terranes in Canada. These are interpreted as having a Baltican/Amazonian affinity based primarily on published U-Pb and Lu-Hf detrital zircon data. Based on U-Pb detrital zircon data, there is no significant difference between the Hope Valley and Esmond-Dedham subterranes. Detrital zircon of two samples of the Price Neck and Newport Neck formations of the Neoproterozoic Newport Group in southern Rhode Island is characterized by large ca. 647–643 and ca. 745–733 Ma age populations and minor zircon up to ca. 3.1 Ga. This signature is most consistent with a northwest African affinity. The Newport Group may thus represent a subterrane, terrane, or other crustal block with a different origin and history than the southeastern New England Avalon terrane to the northwest. The boundary of this Newport Block may be restricted to the boundaries of the Newport Group, or it may extend as far north as Weymouth, Massachusetts, as far northwest as (but not including) the North Attleboro Formation quartzite and associated rocks in North Attleboro, Massachusetts, and as far west as Warwick, Rhode Island, where eastern exposures of the Blackstone Group quartzite exist. The Newport Block may have amalgamated with the Amazonian/Baltican part of the Avalon terrane prior to mid-Paleozoic amalgamation with Laurentia, or it may have arrived as a separate terrane after accretion of the Avalon terrane. Alternatively, it may have arrived during the formation of Pangea and been stranded after the breakup of Pangea, as has been proposed previously for rocks of the Georges Bank in offshore Massachusetts. If the latter is correct, then the boundary between the Newport Block and the southeastern New England Avalon terrane is the Pangean suture zone.

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U-Pb zircon ages and Sm-Nd isotopic data from the Cobequid Highlands, Nova Scotia, Canada: New contributions to understanding the Neoproterozoic geologic history of Avalonia

White

Barr

Crowley

et al. 2022

New Developments in the Appalachian-Caledonian-Variscan Orogen

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Forty-three new U-Pb zircon ages from metasedimentary and igneous rock units throughout the Cobequid Highlands of northern mainland Nova Scotia, Canada, provide new insights into the Neoproterozoic evolution of this long-enigmatic part of Avalonia in the northern Appalachian orogen. Contrasts in ages and rock types resulted in the identification of fault-bounded Neoproterozoic assemblages of units forming the Bass River, Jeffers, and Mount Ephraim blocks. In the Bass River block, quartzite, metawacke, and minor calc-silicate rocks and marble (Gamble Brook Formation) with a maximum depositional age of 945 ± 12 Ma are associated with subaqueous mafic volcanic rocks, siltstone, and ironstone (Folly River Formation) and intruded by 615–600 Ma calc-alkalic subduction-related dioritic to granitic rocks of the Bass River plutonic suite. The contrasting Jeffers block forms most of the Cobequid Highlands and consists mainly of intermediate to felsic volcanic, epiclastic, and minor plutonic rocks. The western and eastern areas of that block yielded ages mainly ca. 607–592 Ma for both volcanic and plutonic rocks, whereas the central area has ages of ca. 630–625 Ma from both volcanic and plutonic rocks and inheritance in overlying Devonian conglomerate. The Mount Ephraim block forms the eastern part of the highlands and includes possible ca. 800 Ma quartzofeldspathic, semipelitic and pelitic gneiss and schist of the Mount Thom Formation, ca. 752 Ma volcanic arc rocks of the Dalhousie Mountain Formation and related 752–730 Ma gabbroic/dioritic to granitic plutons of the Mount Ephraim plutonic suite and Six Mile Brook pluton, as well as ca. 631 Ma granitoid rocks of the Gunshot Brook pluton. The pre–750 Ma high-grade regional metamorphism and deformation and 752–730 Ma subduction-related magmatism recorded in the Mount Ephraim block were previously unrecognized in Avalonia. Evidence from zircon inheritance and Sm-Nd isotopic data in igneous units suggests linkages among these now-separate areas, and comparison with other parts of Avalonia in the northern Appalachian orogen suggests similarity to southeastern New England.

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Investigating the Boundaries of the Southeastern New England Avalon Terrane: New La-Icp-MS U-Pb Zircon Dates From Igneous and Metasedimentary Rocks

Cited by 4 publications

References 0 publications

Supplemental Material: U-Pb detrital zircon analysis of sedimentary rocks of the southeastern New England Avalon terrane in the U.S. Appalachians: Evidence for a separate crustal block

Supplemental Material: U-Pb detrital zircon analysis of sedimentary rocks of the southeastern New England Avalon terrane in the U.S. Appalachians: Evidence for a separate crustal block

U-Pb detrital zircon analysis of sedimentary rocks of the southeastern New England Avalon terrane in the U.S. Appalachians: Evidence for a separate crustal block

U-Pb zircon ages and Sm-Nd isotopic data from the Cobequid Highlands, Nova Scotia, Canada: New contributions to understanding the Neoproterozoic geologic history of Avalonia

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