Detrital zircons from modern sands in New England and the timing of Neoproterozoic to Mesozoic Magmatism

Bradley, Dwight C.; O’Sullivan, Paul B.; Bradley, Lauren M.

doi:10.2475/05.2015.03

Cited by 15 publications

(12 citation statements)

References 89 publications

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“…The area of regional metamorphism and penetrative deformation is far greater for the Acadian than for any of the other events (Robinson et al, 1998). Judging from the age distribution of granites, the two greatest peaks in Appalachian magmatic activity were during the Acadian (407 and 379 Ma) (Bradley et al, 2015). The Acadian foreland basin received an extremely large volume of sediment.…”

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confidence: 98%

Detrital zircon geochronology of pre‐ and syncollisional strata, Acadian orogen, Maine Appalachians

Bradley

O’Sullivan²

2016

Basin Research

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The Central Maine Basin is the largest expanse of deep‐marine, Upper Ordovician to Devonian metasedimentary rocks in the New England Appalachians, and is a key to the tectonics of the Acadian Orogeny. Detrital zircon ages are reported from two groups of strata: (1) the Quimby, Rangeley, Perry Mountain and Smalls Falls Formations, which were derived from inboard, northwesterly sources and are supposedly older; and (2) the Madrid, Carrabassett and Littleton Formations, which were derived from outboard, easterly sources and are supposedly younger. Deep‐water deposition prevailed throughout, with the provenance shift inferred to mark the onset of foredeep deposition and orogeny. The detrital zircon age distribution of a composite of the inboard‐derived units shows maxima at 988 and 429 Ma; a composite from the outboard‐derived units shows maxima at 1324, 1141, 957, 628, and 437 Ma. The inboard‐derived units have a greater proportion of zircons between 450 and 400 Ma. Three samples from the inboard‐derived group have youngest age maxima that are significantly younger than the nominal depositional ages. The outboard‐derived group does not share this problem. These results are consistent with the hypothesised provenance shift, but they signal potential problems with the established stratigraphy, structure, and (or) regional mapping. Shallow‐marine deposits of the Silurian to Devonian Ripogenus Formation, from northwest of the Central Maine Basin, yielded detrital zircons featuring a single age maximum at 441 Ma. These zircons were likely derived from a nearby magmatic arc now concealed by younger strata. Detrital zircons from the Tarratine Formation, part of the Acadian foreland‐basin succession in this strike belt, shows age maxima at 1615, 980 and 429 Ma. These results are consistent with three episodes of zircon recycling beginning with the deposition of inboard‐derived strata of the Central Maine Basin, which were shed from post‐Taconic highlands located to the northwest. Next, southeasterly parts of this succession were deformed in the Acadian orogeny, shedding detritus towards the northwest into what remained of the basin. Finally, by Pragian time, all strata in the Central Maine Basin had been deformed and detritus from this new source accumulated as the Tarratine Formation in a new incarnation of the foreland basin. Silurian‐Devonian strata from the Central Maine Basin have similar detrital zircon age distributions to coeval rocks from the Arctic Alaska and Farewell terranes of Alaska and the Northwestern terrane of Svalbard. We suggest that these strata were derived from different segments of the 6500‐km‐long Appalachian‐Caledonide orogen.

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confidence: 98%

Detrital zircon geochronology of pre‐ and syncollisional strata, Acadian orogen, Maine Appalachians

Bradley

O’Sullivan²

2016

Basin Research

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“…to Silurian turbidites in south-central Maine at 321 ± 2 Ma. This represents a time when New England was otherwise magmatically quiescent (Bradley et al 2015a), with the only other known intrusion of similar age being the Palermo pegmatite in central New Hampshire (ca. 326 Ma, U-Pb zircon; Bradley et al 2015b).…”

Section: Age Correlationsmentioning

confidence: 98%

The Litchfield Pluton in South-Central Maine: Carboniferous Alkalic Magmatism in northern New England, USA

West

Bradley

Coish

2016

atgeol

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The Litchfield pluton is a poorly exposed 7 km 2 composite alkalic intrusive complex that cuts previously deformed and metamorphosed Silurian turbidites in south-central Maine. The pluton includes a variety of alkaline syenites, including the type locality of "litchfieldite, " a coarse-grained cancrinite-, sodalite-, and lepidomelane-bearing nepheline syenite first recognized over 150 years ago and common in many petrologic collections. A new U-Pb zircon age of 321 ± 2 Ma from the nepheline syenite is interpreted to represent the crystallization age of the plutonic complex. A new biotite 40 Ar/ 39 Ar age of 239 ± 1 Ma from the syenite is similar to previously published mica ages from the surrounding country rocks and dates the time of regional cooling in the area below ~ 300°C. Whole-rock chemical analyses of rocks of the Litchfield pluton reveal silica-undersaturated alkaline compositions that are consistent with formation in a within-plate tectonic setting. The age and geochemical characteristics of the alkalic igneous rocks near Litchfield are consistent with a model that invokes the generation of a small volume of alkalic magma beneath south-central Maine during a period of Carboniferous transcurrent tectonism in the northern Appalachian orogen. RÉSUMÉLe pluton de Litchfield est un complexe intrusif alcalin composite de sept kilomètres carrés peu affleurant qui recoupe des turbidites siluriennes précédemment déformées et métamorphisées dans le centre-sud du Maine. Le pluton inclut diverses syénites alcalines, notamment la localité type de la « litchfieldite », une syénite néphélinique renfermant de la cancrinite, de la sodalite et de la lépidomélane à grain grossier identifiée pour la première fois il y a plus de 150 ans et répandue dans maintes collections pétrologiques. Une nouvelle datation U-Pb sur zircon de 321 ± 2 Ma de la syénite néphélinique est interprétée comme une représentation de l'âge de la cristallisation du complexe de roches plutoniques. Une nouvelle datation de la syénite par biotite et The Litchfield pluton in south-central Maine: Carboniferous alkalic magmatism in northern New England, USA nepheline syenite (Fig. 2) that was assigned the name "litchfieldite" by Bayley (1892), is part of a composite alkalic plutonic complex (Barker 1965) that occupies an area of approximately 7 km 2 (Fig. 3). While these unusual rocks have attracted the interest of mineral collectors for over a century and a half, extremely poor exposure has discouraged detailed study; thus the age and tectonic INTRODUCTIONSince the mid-1800s (Jackson 1845; Clarke 1886), the small village of Litchfield in south-central Maine (Fig. 1) has been known as a collecting locality for specimens of cancrinite, sodalite, nepheline, and lepidomelane (Fe-rich biotite). The host rock to these minerals, a coarse-grained of the Litchfield pluton, Barker (1965) suggested that they are associated with the Mesozoic White Mountain magma series. However, limited major element geochemical data are available from these rocks, and ...

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“…Plutons were emplaced during multiple pulses spanning the late Neoproterozoic to the Cretaceous (Bradley et al, 2015). The Oxford pegmatite district includes plutons related to four igneous episodes.…”

Section: Regional Geologymentioning

confidence: 99%

“…Deformation and metamorphism took place during the Acadian, Neoacadian, and Alleghanian orogenies. Eusden et al (2017, this volume) present a summary of the geologic history.Plutons were emplaced during multiple pulses spanning the late Neoproterozoic to the Cretaceous (Bradley et al, 2015). The Oxford pegmatite district includes plutons related to four igneous episodes.…”

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confidence: 99%

Lithium-Boron-Beryllium Gem Pegmatites, Oxford Co., Maine: Havey and Mount Mica Pegmatites

Simmons¹,

Falster²,

Webber³

et al. 2017

New England Intercollegiate Geological Conference 2017

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INTRODUCTIONThis fieldtrip will visit two world renowned gem-producing pegmatites, in the Oxford County pegmatite field of western Maine: Havey and Mount Mica pegmatites. This is intended to be primarily an instructional fieldtrip lead by pegmatite experts from the Maine Mineral and Gem Museum (MMGM) MP 2 (Mineralogy, Pegmatology, Petrology) research group. This is an opportunity to learn about the latest research and advances in the field of pegmatology in Maine. Mt. Mica and the Havey pegmatites are enriched in Be, B, and Li and over the last ten years have produced significant finds of gem tourmaline. The Havey produces a very consistent mint green elbaite with lesser amounts of pink and some rare blue gem elbaite. Mt. Mica has produced a huge quantity of gem elbaite in a wide range of colors. Some of the elbaite crystals recently mined from Mt. Mica are exceptionally large and many are fine museum-quality mineral specimens.This field trip guide is divided into the following four sections:1. Field trip summary with the leaders identified (A1- Maine (357595.99 m E, 4918691.40 m N). The field trip will begin with a brief discussion in the parking lot. We encourage carpooling to limit the number of vehicles entering the mines. A convoy of vehicles will travel approximately one hour to the Havey Quarry located off of Levine Road in Poland (395997.39 m E, 4880613.82 m N). Plan to spend approximately 2hrs at this location, starting with a discussion and later an opportunity to collect. Departing the Havey Quarry, the convoy will travel north approximately 40 minutes to the Mt. Mica Quarry located off of Mt. Mica road in Paris (382422.66 m E, 4902813.15 m N). Plan to spend approximately 2 hrs. at this site, which will begin with a discussion and end with an opportunity to collect on the dumps afterwards. There will not be an opportunity to go underground. At 4:00 pm, participants will leave the mine and travel north approximately 40 minutes back to Bethel. We encourage all participants to attend the Friday night reception at the Maine Mineral and Gem Museum. For this field trip, be prepared with a lunch as we will not be stopping along the way. There will be bathroom facilities available at each of the mine sites. Enrollment will be limited to 25 participants. Expect cold and unpredictable weather and dress accordingly. Please note: both quarries we are visiting are not open to the public except via previous arrangement. 1 A1-2 SIMMONS, FALSTER, WEBBER, FELCH, BRADLEY GENERAL GEOLOGY OF THE OXFORD COUNTY PEGMATITE FIELD IN MAINE REGIONAL GEOLOGYThe New England Appalachians formed during a prolonged Wilson Cycle between the breakup of the supercontinent Rodinia in the Neoproterozoic and the staged assembly of the supercontinent Pangea in the Phanerozoic. The pre-Silurian rocks mainly fall into two groups: those of Laurentian or peri-Laurentian affinity, toward the west, and those of peri-Gondwanan affinity, toward the east . These rocks were juxtaposed via mainly convergent plate motions, deformed, metamorphosed, a...

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Detrital zircons from modern sands in New England and the timing of Neoproterozoic to Mesozoic Magmatism

Cited by 15 publications

References 89 publications

Detrital zircon geochronology of pre‐ and syncollisional strata, Acadian orogen, Maine Appalachians

Detrital zircon geochronology of pre‐ and syncollisional strata, Acadian orogen, Maine Appalachians

The Litchfield Pluton in South-Central Maine: Carboniferous Alkalic Magmatism in northern New England, USA

Lithium-Boron-Beryllium Gem Pegmatites, Oxford Co., Maine: Havey and Mount Mica Pegmatites

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