Search

Devonian granitoid plulons comprise a major part of the bedrock of northwestern Maine representing the magmatic expression of the Acadian orogeny in this part of the northern Appalachian orogen. They are petrographically diverse with minerals characteristic of both I- and S-type granites, in some cases within the same intrusion, and some are compositionally zoned. New LA-ICP-MS ages presented here elucidate the timing and duration of this magmatism. The earliest phase of granitoid magmatism began around 410-405 Ma with the emplacement of the Flagstaff Lake Igneous Complex, and the presence of contemporaneous mafic rocks suggests that mantle-derived magmas were also produced at this time. Late Devonian ages, ca. 365 Ma, for many intrusions, such as the Chain of Ponds and Songo plutons, reveal that magmatism continued for 45 million years during which compositionally diverse I- and S-type magmas were produced. In addition, there is evidence that intrusive activity was prolonged within some plutons, for example the Rome-Norridgewock pluton and the Mooselookmeguntic Igneous Complex, with 10-15 myr between intrusive units. The new ages suggest a break in magmatism between 400 Ma and 390 Ma apparently separating Acadian magmatism into early and late pulses. The production of lower crustal I-type magmas appears to have been concentrated later, ca. 380-365 Ma, although several S-type granitoids were also emplaced during this period. These Late Devonian plulons display abundant zircon inheritance with ages around 385 Ma, which suggests that the crust was experiencing enhanced thermal perturbations during this extended timeframe. The new data for granitoid plutons in northwestern Maine are consistent with tectonic models for other parts of Ganderia which propose initial flat slab subduction followed by slab breakoff and delamination. Les plutons granitoides du Devonien constituent une tranche importante du substrat rocheux du nord-ouest du Maine representant l'expression magmatique de l'orogenese acadienne dans cette partie de l'orogene appalachien septentrional. Ils constituent une succession petrographiquement diversifiee, composee de mineraux caracteristiques tant des granites de type I que de type S, dans certains cas a l'interieur de la meme intrusion, alors que la composition des aulres plutons regionaux est zonee. Les nouvelles datations par ablation laser et speclrometrie de masse a plasma induclif presentees ici elucidenl le moment ou est survenu ce magmatisme et sa duree. L'episode le plus ancien du magmatisme granitoide a debute vers 410-405 Ma avec la mise en place du complexe de roches eruptives du lac Flagstaff, meme si la presence de roches mafiques contemporaines laisse supposer que des magmas d'origine mantellique ont egalement ete produits a ce moment. Les datations du Devonien tardif faisant remonter a environ 365 Ma de nombreuses intrusions, comme les plutons Chain of Ponds et Songo, revelent que ce magmatisme s'est dans l'ensemble poursuivi durant 45 millions d'annees au cours desquelles des magmas de type I et S de compositions diverses ont ete produits. II existe de plus des preuves que l'activite intrusive s'est prolongee a l'interieur de certains plutons, par exemple le pluton Rome-Norridgewock et le complexe de roches eruptives de Mooselookmeguntic, qui accusent un ecart de 10 a 15 Ma entre les unites intrusives. Les nouvelles datations permettent de supposer une interruption du magmatisme entre 400 et 390 Ma., qui semble separer le magmatisme acadien en impulsions precoce et tardive. La production de magmas de type I crustaux inferieurs semble s'etre concentree a un moment ulterieur, vers 380 a 365 Ma, bien que plusieurs roches granitoides de type S se soient egalement mises en place durant celte periode. Ces plutons du Devonien tardil presentent un heritage abondanl de zircons remontant a peu pres a 385 Ma, ce qui laisse entendre que la croute terrestre a subi des perturbations thermiques de plus en plus prononcees au cours de cet intervalle prolonge. Les nouvelles donnees sur les plutons granitoides du nord-ouest du Maine correspondent aux modeles tectoniques d'autres parties du terrane de Gander, qui supposent une subduction initiale de plaques plates suivie par une rupture des plaques et une delamination. [Traduit par la redaction], INTRODUCTION Granitic magmas produced during collisional tectonic events are important repositories of information regarding (i) the duration of orogenesis, (ii) the role of mantle inputs, both physical and thermal, and [...]

New U-Pb zircon ages from volcanic, plutonic, and sedimentary units in the Avalonian Caledonia terrane of southern New Brunswick provide better timing constraints in this geologically complex area. Previous ca. 620 Ma ages from the Broad River Group are now corroborated by additional dates from felsic tuff in the Gordon Falls Formation and rhyolite in the former Fairfield (now East Branch Black River) Formation of 620 [+ or -] 5 Ma and 622 [+ or -] 1.9 Ma, respectively. Combined with ages ranging from ca. 625 Ma to 615 Ma from cross-cutting plutons, the data suggest that the minimum age of the Broad River Group is about 615 Ma. A quartz-feldspar porphyry dyke in mafic volcanic rocks of the previously undated Long Beach Formation yielded an igneous crystallization age of 685 [+ or -] 10 Ma, the oldest unit yet dated in the Caledonia terrane but similar in age to porphyry in the Stirling belt in the Avalonian Mira terrane of Nova Scotia. The age of the Coldbrook Group was constrained previously by U-Pb (zircon) ages of volcanic rocks between 560 and 550 Ma as well as by similar ages from comagmatic plutons. Five additional samples from both volcanic and plutonic units lie in the same range of 560-550 Ma, including errors, demonstrating that the Coldbrook Group and related plutons formed in less than 10 million years. Such a large volume of mainly felsic magma erupted and emplaced in a short time span suggests a 'supereruption/supervolcano' environment such as the late Cenozoic southwestern USA but not yet recognized at ca. 560-550 Ma elsewhere in Avalonia. Two units yielded Paleozoic ages: felsite of the Bloomsbury Mountain Formation with a zircon population at 427 [+ or -] 9 Ma, indicating a Silurian maximum emplacement age, and dacite of the Grassy Lake Formation with several zircon grains at 382.8 [+ or -] 8.3 Ma, indicating a maximum age of middle Devonian, the first rocks of this age to be identified in the Caledonia terrane. De nouveaux ages U - Pb sur zircon provenant d'unites volcaniques, plutoniques et sedimentaires dans le terrane avalonien Caledonie du sud du Nouveau-Brunswick fournissent de meilleures contraintes temporelles dans cette region geologiquement complexe. Les ages d'environ 620 Ma precedemment obtenus du Groupe de Broad River sont maintenant appuyes par des dates supplementaires provenant du tuf felsique dans la Formation de Gordon Falls et de la rhyolite dans l'ancienne Formation de Fairfield (maintenant East Branch Black River) de 620 [+ or -] 5 Ma et 622 [+ or -] 1,9 Ma, respectivement. Combine avec des ages allant de 625 Ma a 615 Ma a partir de plutons encaisses, les donnees suggerent que l'age minimum du Broad River Group est d'environ 615 Ma. Un dyke de porphyre de quartz-feldspath dans des roches volcaniques mafiques de la Formation de Long Beach non datee a donne un age de cristallisation ignee de 685 [+ or -] 10 Ma, la plus ancienne unite encore datee dans le terrane de Caledonie mais similaire en age au porphyre dans la ceinture de Stirling dans le terrane avalonien Mira de la Nouvelle-Ecosse. L'age du Groupe de Coldbrook etait auparavant limite par les ages U - Pb (zircon) des roches volcaniques entre 560 et 550 Ma, ainsi que par les ages similaires des plutons co-magmatiques. Cinq echantillons supplementaires provenant des unites volcaniques et plutoniques se situent dans la meme periode de 560 a 550 Ma, y compris les erreurs, demontrant que le Groupe de Coldbrook et les plutons associes se sont formes en moins de 10 millions d'annees. Un volume aussi important de magma principalement felsique ayant entre en eruption et mis en place dans un court laps de temps suggere un environnement de 'super-eruption / supervolcan' tel que le sud-ouest du Cenozoique superieur aux etats-Unis, mais pas encore reconnu entre 560-550 Ma ailleurs dans la zone d'Avalonia. Deux unites ont donne des ages paleozoiques: la felsite de la Formation de Bloomsbury Mountain avec une population de zircon a 427 [+ or -] 9 Ma, indiquant un age de mise en place maximal du Silurien, et la dacite de la Formation de Grassy Lake avec plusieurs grains de zircon a 382,8 [+ or -] 8,3 Ma, indiquant un age maximal du Devonien moyen, premieres roches de cet age identifiees dans le terrane de Caledonie. [Traduit par la redaction], INTRODUCTION The Caledonia terrane is a large area of mainly Neoproterozoic rocks that forms the Avalonian part of southern New Brunswick, extending from the Saint John area to the northeast [...]

The Trafalgar Plutonic Suite intruded metasedimentary rocks of the Goldenville and Halifax groups in the northeastern part of the Meguma terrane of southern Nova Scotia at about 374 Ma, based on previously published U-Pb and (40) Ar/(39) Ar mineral ages. Using field and petrographic observations, the suite is divided into 20 different plutons on the combined basis of variations in grain size (fine, medium, or coarse), texture (equigranular or porphyritic) and modal mineralogy (quartz diorite/tonalite, granodiorite, monzogranite, and syenogranite). The granodiorite, monzogranite, and syenogranite plutons are relatively uniform in composition with little variation in mineralogy or chemistry within each pluton or between plutons of the same lithology. In contrast the quartz diorite/tonalite plutons show mineralogical and chemical variation, both within and between plutons. The granodiorite, monzogranite, and syenogranite plutons closely resemble other peraluminous granitoid plutons characteristic of the Meguma terrane. The quartz diorite/tonalite plutons are varied but chemically resemble minor Devonian mafic intrusions elsewhere in the Meguma terrane. Like other plutons of the Meguma terrane, the Trafalgar Plutonic Suite has chemical characteristics of volcanic-arc to syn-collisional granitoid rocks and likely has experienced extensive contamination by metasedimentary material as documented by previous studies of plutons in the Meguma terrane. The minor quartz diorite/tonalite plutons are additional examples of the mafic rocks that have been proposed in tectonic models of the Meguma terrane to have facilitated melting of the lower crust to generate granodioritic parent magmas, followed by crystal fractionation and extensive contamination by metasedimentary material. La suite plutonique de Trafalgar s'est mise en place dans les roches metasedimentaires des groupes de Goldenville et Halifax dans la partie nord-est de la zone de Meguma au sud de la Nouvelle-Ecosse a environ 374 Ma, d'apres des ages U-Pb et (40)Ar/(39)Ar deja publies. a partir d'observations sur le terrain et petrographiques, la suite se divise en 20 plutons, base sur un ensemble de caracteristiques telles que la variation granulometrique (fin, moyen ou grossier), la texture des roches (equidimensionnel ou porphyritique) et la proportion mineralogique (diorite quartzifere/tonalite, granodiorite, monzogranite et syenogranite). La composition des plutons constitues de granodiorite, de monzogranite et de syenogranite est relativement uniforme avec peu de variation mineralogique ou chimique au sein de chacun des plutons ou d'un pluton a un autre de lithologic semblable. En revanche, les plutons formes de diorite quartzifere/tonalite presentent des variations mineralogiques et chimiques a l'interieur du meme pluton et a travers la suite plutonique. Les plutons constitues de granodiorite, de monzogranite et de syenogranite ressemblent etroitement aux autres granitoides peralumineux de la zone de Meguma. Les plutons de diorite quartzifere/tonalite sont variables mais chimiquement comparables aux intrusions mafiques devoniens retrouves ailleurs dans la zone de Meguma. Comme plusieurs autres plutons de la zone de Meguma, la suite plutonique de Trafalgar possede des caracteristiques chimiques semblables aux granitoides de type arc volcanique a syncollisionnel et ayant sans doute subi une contamination significative des roches metasedimentaires, tels que documente dans des etudes precedentes sur les plutons de la zone de Meguma. Les moins vastes plutons formes de diorite quartzifere/tonalite constituent des exemples supplementaires de roches mafiques qui furent presentees dans des modeles tectoniques de la zone de Meguma comme ayant contribuees a la fusion de la croute inferieure et ainsi generer un magma parent granodioritique, suivi d'une cristallisation fractionnee combinee a une contamination importante provenant des roches metasedimentaires. [Traduit par la redaction], INTRODUCTION The Trafalgar Plutonic Suite (White et al. 2009a, b; White and Scallion 2011) is an assemblage of granitoid plutons in the Trafalgar area near the northern margin of the [...]

Southern New Brunswick consists of a collage of fault-bounded belts of Late Neoproterozoic igneous and metamorphic rocks, early Paleozoic sedimentary, metamorphic and igneous units, and overlying Carboniferous and locally Triassic sedimentary rocks. The area also contains the boundary between Avalonia and Ganderia as interpreted in the northern Appalachian orogen. New detrital zircon ages reported here provide improved understanding of depositional ages and provenance of diverse Neoproterozoic to Carboniferous rocks in this complex area. Detrital zircon data from samples with Neoproterozoic maximum depositional ages indicate a dominantly Gondwanan provenance with strong influence from the Amazonian craton. However, quartzite from The Thoroughfare Formation on Grand Manan Island contains dominanly 2 Ga zircon grains, consistent with derivation from the West African craton. The age spectrum is similar to that of the Hutchins Island Quartzite in the Isleboro block in Penobscot Bay, Maine, strengthening the possibility of correlation between the two areas. Cambrian samples also show prominent peri-Gondwanan provenance with strong influence from F.diacaran to early Cambrian arc magmatism. The maximum depositional ages of these samples are consistent with previous interpretations of Cambrian ages based on fossil correlations and field data. A Carboniferous sample from Avalonia shows a significant contribution from Devonian magmatism as the youngest detrital component, although its depositional age based on field relationships is Carboniferous. The results exemplify the need to integrate multiple datasets in making interpretations from detrital zircon data. Le sud du Nouveau-Brunswick est constitue d'un collage de ceintures delimitees par des failles de roches ignees et metamorphiques du Neoproterozoique tardif, d'unites sedimentaires, metamorphiques et ignees du Paleozoique precoce, ainsi que de roches sedimentaires sus-jacentes du Carbonifere et, par endroits, du Trias. Le secteur comprend egalement la frontiere etablie entre Avalonia et Ganderia selon son interpretation a l'interieur de la partie septentrionale de l'orogene des Appalaches. De nouvelles datations de zircon detritique rapportees ici permettent une meilleure comprehension des ages sedimentaires et de la provenance des diverses roches neoproterozoiques a carboniferes dans ce secteur complexe. Les donnees relatives au zircon detritique obtenues des echantillons faisant etat d'ages sedimentaires remontant au maximum au Neoproterozoique signalent une provenance en predominance gondwanienne avec une forte influence du craton amazonien. Le quartzite de la Formation The Thoroughfare sur l'ile Grand Manan renferme toutefois predominament des grains de zircon de 2 Ga, ce qui correspond a une derivation du craton de l'Afrique occidentale. Le spectre de l'age est similaire a celui du quartzite de l'ile Hutchins a l'interieur du bloc Isleboro dans la baie Penobscot, au Maine, ce qui renforce la possibilite d'une correlation entre les deux secteurs. Les echantillons du Cambrien font eux aussi etat d'une provenance perigondwanienne prononcee, marquee d'une forte influence d'un magmatisme d'arc de l'Ediacarien au Cambrien precoce. Les ages sedimentaires maximaux de ces echantillons correspondent aux interpretations anterieures des datations du Cambrien basees sur des correlations de fossiles et des donnees d'echantillonnage sur le terrain. Un echantillon du Carbonifere provenant d'Avalonia revele une contribution prononcee du magmatisme devonien a titre d'element detritique le plus recent, mais son age sedimentaire le situe au Carbonifere d'apres les relations etablies sur le terrain. Les resultats illustrent la necessite d'une integration de plusieurs ensembles de donnees pour effectuer des interpretations a partir de donnees provenant de zircon detritique. [Traduit par la redaction], INTRODUCTION AND GEOLOGICAL SETTING Southern New Brunswick consists of a complex assemblage of three fault-bounded belts of mainly Neoproterozoic rocks with minor Paleozoic rocks termed (from southeast to northwest) Caledonia, [...]

Zircon grains from a granitic pegmatite clast from conglomerate at the base of the Ross Island Formation on Grand Manan Island indicate an igneous crystallization age of 664.1 [+ or -] 4.6 Ma. The clast also contains abundant older inherited grains back to the Archean. Muscovite in the same clast and an additional similar clast yielded cooling ages of 607.0 [+ or -] 3.7 Ma and 619.6 [+ or -] 4.1 Ma, respectively, providing a maximum depositional age for the host conglomerate of the Ross Island Formation. The Seven Hundred Acre Island Formation in the Islesboro block in Penobscot Bay, Maine, contains a granitic pegmatite dyke of similar age, suggesting that it was close to the site of deposition of the Ross Island Formation of Grand Manan Island in the late Ediacaran. This suggestion is supported further by similarity in rock types and detrital zircon spectra between the Seven Hundred Acre Island Formation and The Thoroughfare and Kent Island formations on Grand Manan Island. Des grains de zircon provenant d'un ciaste de pegmatite granitique du conglomerat a la base de la Formation de Ross Island sur l'ile Grand Manan signalent une cristallisation ignee survenue il y a 664,1 [+ or -] 4,6 Ma. Le ciaste renferme egalement une abondance de grains herites plus ages remontant a l'Archeen. La muscovite dans le meme ciaste et un ciaste similaire supplementaire a accuse des ages de refroidissement de 607,0 [+ or -] 3,7 Ma et de 619,6 [+ or -]4,1 Ma, respectivement, ce qui definit l'age maximal de la sedimentation du conglomerat hote de la Formation de Ross Island. La Formation de Seven Hundred Acre Island dans le bloc d'Islesboro a l'interieur de la baie de Penobscot, dans le Maine, abrite un dyke de pegmatite granitique d'age similaire, ce qui laisse supposer qu'il se trouvait pres de l'emplacement de la sedimentation de la Formation de Ross Island sur l'ile Grand Manan au cours de l'Ediacarien tardif. La similarite des types rocheux et des spectres de zircons detritiques entre la Formation de Seven Hundred Acre Island et les formations de Thoroughfare et de Kent Island sur l'ile Grand Manan appuient une telle supposition. [Traduit par la redaction], INTRODUCTION Pre-Mesozoic rocks are exposed on the southeastern third of Grand Manan Island and adjacent offshore islands in the Bay of Fundy (Figs. 1, 2). Published U-Pb (zircon) ages have [...]

Granitoid plutons are a major component of pre-Carboniferous rocks in Cape Breton Island and knowledge of the time and tectonic setting of their emplacement is crucial for understanding the geological history of the island, guiding exploration for granite-related economic mineralization, and making along-orogen correlations. The distribution of these plutons and their petrological characteristics have been used in the past for recognizing both Laurentian and peri-Gondwanan components in Cape Breton Island, and for subdividing the peri-Gondwanan components into Ganderian and Avalonian terranes. However, ages of many plutons were assumed on the basis of field relations and petrological features compared to those of the relatively few reliably dated plutons. Seventeen new U--Pb (zircon) ages from igneous units reported here provide enhanced understanding of the distribution of pluton ages. Arc-related plutons in the Aspy terrane with ages of ca. 490 to 475 Ma likely record the Penobscottian tectonomagmatic event recognized in the Exploits subzone of central Newfoundland and New Brunswick but not previously recognized in Cape Breton Island. Arc-related Devonian plutonic activity in the same terrane is more widespread, continuous, and protracted (445 Ma to 395 Ma) than previously known. Late Devonian magmatism in the Ganderian Aspy terrane is similar in age to that in the Avalonian Mira terrane (380 to 360 Ma) but the tectonic settings are different. In contrast, magmatic activity in the Bras d'Or terrane is almost exclusively arc-related in the Late Ediacaran (580 to 540 Ma) and rift-related in the Late Cambrian (520 to 490 Ma). The new data support the terrane distinctions previously documented. Les plutons granitoïdes sont des composants importants des roches précarbonifères de l'île du Cap Breton, et il est crucial de connaître le moment et le cadre tectonique de leur mise en place pour comprendre l'évolution géologique de l'île, orienter l'exploration de la minéralisation économique liée au granite et établir des corrélations le long de l'orogène. La distribution des plutons et leurs caractéristiques pétrologiques ont été utilisées dans le passé pour reconnaître les composants laurentiens et périgondwaniens dans l'île du Cap Breton et pour subdiviser les composants périgondwaniens entre les terranes gandériens et les terranes avaloniens. Cependant, l'âge de bon nombre de plutons a été présumé en fonction des observations sur le terrain et de leurs caractéristiques pétrologiques comparativement à celles des plutons datés de manière fiable, relativement peu nombreux. Dix sept nouveaux âges U-Pb sur zircon fondés sur des unités ignées et déclarés dans le présent document permettent de mieux comprendre la répartition selon l'âge des plutons. Dans le terrane d'Aspy, des plutons liés à l'arc dont les âges se situent environ entre 490 et 475 Ma illustrent vraisemblablement l'événement tectonomagmatique penobscottien reconnu dans la sous-zone de la rivière Exploits dans le centre de Terre Neuve, mais qui n'a pas été reconnu auparavant à l'île du Cap-Breton. L'activité plutonique Dévonien liée à l'arc dans le même terrane est plus répandue, continue et prolongée (445 Ma à 395 Ma) qu'on ne le croyait antérieurement. Le magmatisme du Dévonien tardif dans le terrane gandérien d'Aspy est d'un âge semblable à celui du terrane de Mira de l'Avalonien (380 Ma à 360 Ma); toutefois, les milieux tectoniques sont différents. En revanche, l'activité magmatique dans le terrane de Bras d'Or est quasi exclusivement liée à l'arc dans l'Édiacarien tardif (580 Ma à 540 Ma) et liée au rift dans le Cambrien tardif (520 Ma à 490 Ma). Les nouvelles données appuient les distinctions documentées antérieurement au sujet des terranes. [Traduit par la redaction], INTRODUCTION Cape Breton Island, Nova Scotia, is a granite-lover's paradise. Granitoid plutons constitute more than half of pre-Carboniferous rocks on the island and more than 120 different plutons, many of [...]

The Creignish Hills and North Mountain areas of southwestern Cape Breton Island consist mostly of Neoproterozoic rocks typical of the Ganderian Bras d'Or terrane. U-Pb ages presented here for detrital zircon in the Blues Brook Formation of the Creignish Hills confirm a depositional age no greater than about 600 Ma. Although it is possible that some components of the formation are much older, similarities in rock types and field relations suggest that this is not the case. It is likely that the equivalent Malagawatch Formation of the North Mountain area, as well as high-grade metasedimentary rocks of the Melford Formation and Chuggin Road complex in the Creignish Hills and Lime Hill gneiss complex in the North Mountain area, represent the same or stratigraphically equivalent units as the Blues Brook Formation. The minimum ages of all of these units are constrained by cross-cutting syn- and post-tectonic plutons with ages mostly between 565 and 550 Ma, indicating that sediments were deposited, regionally metamorphosed, deformed, and intruded by plutons in less than 40-50 million years. The assemblage of pelitic, psammitic, and carbonate rocks indicates that a passive margin in a tropical climate was quickly changed to an active Andean-type continental margin in which voluminous calcalkaline dioritic to granitic plutons were emplaced. This sedimentary and tectonic history is characteristic of the Bras d'Or terrane and is shared by its likely correlative, the Brookville terrane in southern New Brunswick. Les secteurs des collines Creignish et du mont North dans le sud-ouest de l'ile du Cap-Breton sont principalement constitues de roches neoproterozo'iques typiques du terrane de Ganderian Bras d'Or. Les ages U-Pb sur zircon detritique de la formation de Blues Brook des collines Creignish presentes ici confirment une sedimentation survenue il y a au plus 600 Ma environ. Meme s'il est possible que certains elements de la formation soient beaucoup plus ages, les similarites des lithotypes et les observations sur le terrain laissent supposer que ce n'est pas le cas. Il est probable que la formation equivalente de Malagawatch dans le secteur du mont North de meme que les roches metasedimentaires a forte teneur de la formation de Melford et du complexe du chemin Chuggin dans les collines Creignish et le complexe de gneiss de la colline Lime dans le secteur du mont North representent les memes unites que la formation de Blues Brook ou des unites stratigraphiquement equivalentes. Les ages minimaux de toutes ces unites sont limites par les plutons syntectoniques et post-tectoniques transversaux, ages pour la plupart de 550 a 565 Ma, ce qui revele que les sediments se sont deposes, se sont metamorphises et deformes a lechelle regionale, et ont ete penetres par les plutons au cours dune periode de moins de 40 a 50 millions d'annees. L'assemblage de roches pelitiques, psammitiques et carbonatees signale qu'une marge passive dans un climat tropical s'est rapidement transformee en une marge continentale de type andeen active dans laquelle de volumineux plutons calco-alcalins dioritiques a granitiques se sont mis en place. Un tel passe sedimentaire et tectonique est caracteristique du terrane de Bras d'Or et constitue un trait que le terrane a en commun avec l'unite vraisemblablement correlative du terrane de Brookville dans le sud du Nouveau-Brunswick. [Traduit par la redaction], INTRODUCTION The Creignish Hills and North Mountain areas of western Cape Breton Island (Fig. 1) consist mostly of Neoproterozoic metasedimentary and plutonic rocks typical of the Bras d'Or terrane of [...]

Geological mapping, petrological studies, and U-Pb (zircon) dating were done to better characterize metasedimentary and metaigneous rock units in the northeastern Aspy terrane, Cape Breton Highlands, Nova Scotia. Foliated biotite [...]

ABSTRACT The relationship between low-grade metasedimentary and high-grade paragneissic Precambrian rock units in the Bras d'Or terrane of central Cape Breton Island is a long-standing geological problem. Whole-rock geochemical and [...]

Appalachian-Caledonide orogen development has been traditionally illustrated using cross-sections showing terrane accretion and collision over time. This approach is valuable but leads to implicit assumptions: subduction was initiated at passive [...]

ABSTRACT The Late Silurian Landry Brook and Dickie Brook plutons and Charlo plutonic suite underlie a combined area of approximately 80 [km.sup.2] in the northeastern part of the Ganderian Tobique-Chaleur [...]

The ca. 620 Ma Huntington Mountain pluton and East Bay Hills Group, which comprise part of the Avalonian Mira terrane, Cape Breton Island, Nova Scotia, Canada, are characterized by pervasive [...]

A quartz sandstone bed in a dominantly conglomeratic section in the central part of the Lower Carboniferous Horton Group on Petit-de-Grat Island, offshore southern Cape Breton Island, Nova Scotia, contains [...]

ABSTRACT Machias Seal Island in the northern Gulf of Maine consists of fine- to medium-grained weakly foliated quartz monzodiorite. Although previously inferred to be as young as Devonian, the quartz [...]

ABSTRACT Late Neoproterozoic (680 Ma to 560 Ma) Avalonian rocks in the Mira terrane of southeastern Cape Breton Island have been metamorphosed inhomogeneously, at very low grade to low grade, [...]

ABSTRACT 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 [...]

ABSTRACT A major ductile high-strain zone up to 5 km in width can be traced for at least 70 km diagonally across the Avalonian Caledonia terrane of southern New Brunswick. [...]

ABSTRACT The Mechanic Settlement Pluton, southern New Brunswick, is a high-level mafic-ultramafic pluton of Late Neoproterozoic age (ca. 557 Ma). Based on surface-outcrop and drill-core samples, the pluton includes six [...]

ABSTRACT The Lower Coverdale intrusion near Moncton, New Brunswick, has been intersected in drill holes at depths of 100-200 m below unconformably overlying Carboniferous sandstone, conglomerate and, locally, limestone of [...]

ABSTRACT The northeastern part of Kaipokok Bay is located in the Makkovik Province of Labrador, in the boundary zone between the Kaipokok and Aillik domains. The Kaipokok domain is characterized [...]

ABSTRACT The islands known as The Wolves are located in the Bay of Fundy, approximately 10 km offshore from mainland southwestern New Brunswick. They are underlain by monzodiorite, gradational to [...]

ABSTRACT Anomalously thick and coarse clastic sedimentary successions, including over 5000 m of conglomerate, are exposed on Isle Madame off the southern coast of Cape Breton Island. Two steeply to [...]

ABSTRACT The Lochaber-Mulgrave area of northern mainland Nova Scotia is underlain by rocks of the Late Devonian- Early Carboniferous Horton Group, in faulted contact with older Devonian and Silurian rocks [...]

ABSTRACT A new U-Pb (zircon) age of 357 ± 1 Ma for the Wedgeport pluton in the Meguma terrane of southwestern Nova Scotia confirms that it is younger than other [...]

ABSTRACT Late Proterozoic to Early Cambrian igneous rocks are major components of the fault-bounded Caledonia, Brookville, and New River terranes of southern New Brunswick. As previously demonstrated, ca. 620 Ma [...]

ABSTRACT Latest Neoproterozoic and Cambrian plutons in the Brookville terrane of southern New Brunswick are termed the Golden Grove Plutonic Suite. Four groups are recognized on the basis of composition: [...]

Gabbro from the Caledonia Mountain Pluton in the northeastern Caledonian Highlands of southern New Brunswick yielded a U-Pb (zircon) crystallization age of 615 ± 1 Ma. The age shows that [...]

Zircon grains from a granitic pegmatite clast from conglomerate at the base of the Ross Island Formation on Grand Manan Island indicate an igneous crystallization age of 664.1 ± 4.6 Ma. The clast also contains abundant older inherited grains back to the Archean. Muscovite in the same clast and an additional similar clast yielded cooling ages of 607.0 ± 3.7 Ma and 619.6 ± 4.1 Ma, respectively, providing a maximum depositional age for the host conglomerate of the Ross Island Formation. The Seven Hundred Acre Island Formation in the Islesboro block in Penobscot Bay, Maine, contains a granitic pegmatite dyke of similar age, suggesting that it was close to the site of deposition of the Ross Island Formation of Grand Manan Island in the late Ediacaran. This suggestion is supported further by similarity in rock types and detrital zircon spectra between the Seven Hundred Acre Island Formation and the Thoroughfare and Kent Island formations on Grand Manan Island. [ABSTRACT FROM AUTHOR]