Sutton Mountains Research Articles

Dating polyphase deformation across low-grade metamorphic belts: An example based on 40Ar/39Ar muscovite age constraints from the southern Quebec Appalachians, Canada

Research Article| July 01, 2007 Dating polyphase deformation across low-grade metamorphic belts: An example based on 40Ar/39Ar muscovite age constraints from the southern Quebec Appalachians, Canada Sébastien Castonguay; Sébastien Castonguay 1Geological Survey of Canada, GSC-Québec, 490 rue de la Couronne, Québec G1K 9A9, Canada Search for other works by this author on: GSW Google Scholar Gilles Ruffet; Gilles Ruffet 2Geosciences Rennes, CNRS-Université de Rennes 1, Campus de Beaulieu, Avenue Général Leclerc, Rennes Cedex 35042, France Search for other works by this author on: GSW Google Scholar Alain Tremblay Alain Tremblay 3Département des Sciences de la Terre et de l'Atmosphère, Université du Québec à Montréal, C.P. 8888, Succursale Centre-Ville, Montréal, Québec H3C 3P8, Canada Search for other works by this author on: GSW Google Scholar GSA Bulletin (2007) 119 (7-8): 978–992. https://doi.org/10.1130/B26046.1 Article history received: 25 May 2006 rev-recd: 01 Feb 2007 accepted: 02 Feb 2007 first online: 08 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share MailTo Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Sébastien Castonguay, Gilles Ruffet, Alain Tremblay; Dating polyphase deformation across low-grade metamorphic belts: An example based on 40Ar/39Ar muscovite age constraints from the southern Quebec Appalachians, Canada. GSA Bulletin 2007;; 119 (7-8): 978–992. doi: https://doi.org/10.1130/B26046.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Geochronologic 40Ar/39Ar data of fabric-forming metamorphic minerals, in conjunction with structural and metamorphic studies, are being increasingly used to constrain the deformation and tectonometamorphic evolution of polyphase low-grade orogens. Careful data interpretation is needed to extract meaningful age constraints from neo- and recrystallized minerals affected by isotopic disturbances. In the southern Quebec Appalachians, the Sutton Mountains anticlinorium exposes the metamorphic core of the early Paleozoic continental margin of Laurentia. Orogenesis in this part of the Appalachians was the result of tectonic events that have been classically attributed to the combined effects of the Middle to Late Ordovician Taconian and the Middle Devonian Acadian orogenies; however, evidence of separate and distinct Silurian–Early Devonian tectonism has also been recently documented. Laser step-heating 40Ar/39Ar data on single-grains of muscovite from polydeformed greenschist facies samples of the Sutton Mountains anticlinorium indicate that these tectonometamorphic events are heterogeneously preserved as a prograde Taconian event at ca. 456 Ma and an Acadian overprint at ca. 390 Ma. The integration of 40Ar/39Ar age spectra analyses with structural relationships provides precise age constraints on the duration, propagation, and evolution of Silurian–Early Devonian hinterland-directed deformation as it migrated across the anticlinorium, including back thrusting from ca. 433 Ma to ca. 420 Ma and extensional faulting from ca. 417 Ma to ca. 405 Ma. Along the Laurentian margin of the northern Appalachians, such Silurian–Early Devonian tectonism is currently attributed either to the collapse of the Taconian orogen triggered by the delamination of the subducted slab or to the outboard accretion of peri-Gondwanan terranes during the Salinic orogeny. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Ediacaran U–Pb zircon dates for the Lac Matapédia and Mt. St.-Anselme basalts of the Quebec Appalachians: support for a long-lived mantle plume during the rifting phase of Iapetus opening

It has been suggested that the rifting phase of Iapetus Ocean opening in Quebec involved a long-lived mantle plume centered near the Sutton Mountains whose dominant magmatism was first of continental flood basalt composition and later of ocean-island basalt (OIB) composition. We dated the Lac Matapédia and Mt. St.-Anselme basalts, which are thought to have originated from this plume and have dominant OIB-like composition. The U–Pb dating was done on individual zircon crystals using a laser ablation microprobe linked to an inductively coupled plasma – mass spectrometer. Zircons from two basalt flows at Lac Matapédia yielded ages of 565 ± 6 and 556 ± 5 Ma. Zircons from a basalt flow at Mt. St.-Anselme yielded an age of 550 ± 7 Ma. Although the basalts are allochthonous, these should be their ages of extrusion onto Laurentia, as shown by Grenvillian ages yielded by inherited zircons in both Lac Matapédia flows and by zircons in a granitic pebble from the Mt. St.-Anselme Formation. Our dating supports the hypothesis of a long-lived (~615 to ~550 Ma) Sutton Mountains mantle plume involved in Iapetus rifting. It does so by closing a possible gap of ~10 Ma between the end of flood basalt and the beginning of OIB magmatism, and by supporting ~540 (rather than ~570) Ma for the rift-to-drift transition in Quebec. Because plumes move slowly, this hypothesis implies that Laurentia moved slowly from ~615 to ~550 Ma. This is consistent with paleomagnetic evidence, although very rapid true polar wander at ~590 Ma may need to be invoked.

Geochemistry and petrogenesis of the Tibbit Hill metavolcanic suite of the Appalachian fold belt, Quebec-Vermont; a plume-related and fractionated assemblage

The Late NeoProterozoic metavolcanic Tibbit Hill Formation (THF) covers a large crustal segment exposed along a belt about 250 km long in the Appalachian fold belt (Quebec-Vermont). It is predominantly basaltic in composition but contains a minor component of felsic and intermediate alkaline volcanic lithologies. Geochemically, the Tibbit Hill Formation forms a continuum in composition and exhibits a wide range of SiO2 (44-76 wt. percent), covering the entire spectrum from alkali basalt to trachyte and comendite. This mildly alkaline suite is relatively enriched in incompatible elements and exhibits a wide range of Zr (138-1493 ppm), Nb (15-139 ppm), and Y (18-185 ppm) concentrations, among other elements. The concentrations of the HFSE and the REE gradually increase toward the more evolved lithologies. The chondrite normalized REE patterns are fractionated (LREE-enriched over HREE), parallel to subparallel, and generally uniform but with negative Eu-anomalies developed in the more felsic varieties. These geochemical features underline the comagmatic nature of the entire suite and are consistent with a fractionated basalt to comendite suites. The incompat- ible element profiles suggest that most of these elements including Nb, Zr, Ti, Y, and the REE have not been affected by metamorphism, as they remained largely intact within the THF rocks. Chemical features of the mafic rocks are typical of within-plate basalts and suggest that their melts were derived from a fertile or plume-related mantle source. Chemical features of the felsic and intermediate rocks are typical of anorogenic A1 type suites, related to hotspots, mantle plumes, or continental rift zones. This is consistent with the regional geological context with the volcanism, associated with an Iapetan RRR triple junction, occurring shortly before the onset of seafloor spreading. Geochemical modelling shows that the THF basaltic magma was produced by a very small degree of batch partial melting (F 2.5 percent) of a garnet- bearing primitive mantle source (garnet lherzolite). A final basaltic melt segrega- tion depth is estimated at 80 to 100 km. Melting probably occurred within the thermal anomaly of a rising mantle plume beneath the Sutton Mountains triple junction (near the Quebec-Maine border). Fractionation of THF basaltic magma produced minor trachytic and comenditic magmas. The volcanic assemblage of the Afar rift (for example, Boina centre) appears to represent a modern analogue to the THF volcanic suite.

Stratigraphic position and conodonts of the early Middle Ordovician Melbourne Formation, Quebec

A new fossil locality yielding rare conodonts of probable late Arenig to early Llanvirn age in the previously unfossiliferous Melbourne Formation of the Appalachian Humber Zone has been discovered in the Eastern Townships of Quebec. The presence of a continental-margin fauna at the northeast end of the Sutton Mountains Anticlinorium suggests a continuity of sedimentation, and this contradicts previous suggestions of a major disconformity between the Lower and Middle Ordovician rocks in this part of the Quebec Reentrant. Moreover, recent geological mapping shows that the contact between the conodont-bearing Melbourne Formation and the underlying Sweetsburg Formation of the Oak Hill Group is conformable and gradational. Consequently, it is proposed that the graphitic limestone of the Melbourne Formation represents the youngest unit of the Cambro-Ordovician Oak Hill Group.

Chalcopyrite–bornite and chalcopyrite–bornite–barite in the Acton Vale Limestone, southeastern Quebec: mineralized shelf-margin slivers in a Taconian nappe

The Acton Vale limestone units of probable Early Ordovician age in the external nappe zone of the Appalachian foldbelt in southeastern Quebec host numerous occurrences of vein- and breccia-type copper deposits. Associated with these are two significant occurrences of barite: one at Upton consisting of a stratiform mass of probable economic potential; and the other at Lord Aylmer consisting of thin, tabular, karstic infillings of barite. Studies of the mineral occurrences at Acton Vale, Upton, and Lord Aylmer show that the mineralization is epigenetic and formed largely by open-space filling at shallow depths in parts of the limestones that had undergone ground preparation by brecciation and (or) karsting. Fluid-inclusion, sulphur-isotope, and strontium-isotope analyses show that mineral deposition occurred at temperatures ranging from 110° to 135 °C, that sea water formed the bulk of the mineralizing fluids, and that altered basaltic volcanic rocks associated with the Acton Vale limestones are. the most important source of metals and Ba.The mineral deposits seem to have formed during the evolution of the passive margin of Laurentia. The preferred model for their genesis is one involving deep circulation of water, which, on coming into contact with the volcanic rocks, leached metals and Ba and subsequently deposited them in favourable parts of Acton Vale limestones. Recurrent movements of faults of the Ottawa Graben, which is the failed arm of the Sutton Mountains triple junction, may have been a factor that facilitated deep circulation of fluids. In their present setting, the Acton Vale limestones and the associated volcanic rocks and shales probably represent slivers of the passive margin incorporated into the Cambrian shale – feldspathic sandstone assemblages of the Granby Nappe.

Geochemistry and U–Pb zircon age of comenditic metafelsites of the Tibbit Hill Formation, Quebec Appalachians

Metafelsites in Waterloo area, Quebec, represent the only known silicic volcanic rocks in the predominantly basaltic Tibbit Hill Formation. Low-grade metamorphism accompanied by hydration and albitization has converted the felsic volcanic rocks mainly to muscovite–quartz–albite schists. The volcanic parent of these metafelsites was formed partly as lava flows and partly as tuffs. The principal compositional type was a comendite. A component of intermediate rocks is also present but its extent is undetermined and probably minor. U–Pb zircon studies of the metafelsites have yielded a reliable age of [Formula: see text]. This Early Cambrian age is probably representative of the age of the Tibbit Hill Formation as a whole.The Tibbit Hill Formation accumulated at one of the clearest examples of a RRR (rift–rift–rift) triple junction–the Sutton Mountains triple junction–of the continental rift system formed as a prelude to the opening of the Iapetus Ocean. Its volcanic rocks are products of the youngest major episode of rift-related volcanism known from the continental margin of Laurentia. The volcanic event may have occurred as a harbinger of the onset of sea-floor spreading at the Sutton Mountains triple junction.

West-southwest glacial dispersal of pillow-lava boulders, Philipsburg–Sutton region, Eastern Townships, Quebec

Pillow-lava boulders, probably from Place Mountain in the Bolton valley east of the Sutton Mountains, occur in a narrow belt or fan 43 km long trending west-southwest (azimuth about 248°) from 10 km southwest of Place Mountains to Rosenberg, near Philipsburg, Quebec. Glacial striations with this direction are uncommon; the general glacial movement indicated by abundant striations and indicator erratics is southeastward. A southwestward flow in the axial part of the St. Lawrence Lowlands near Montréal is apparently the youngest direction there, of late Wisconsinan age. In the Eastern Townships of Quebec east and northeast of the study area and in adjoining northern Vermont there is evidence of a southwestward flow of mid-Wisconsinan age. Local southwestward flow in the study area at the beginning and end of a glacial cycle may have resulted from a mobile bed in the flooded St. Lawrence – Champlain lowland, but a hypothesis of flow from a major mid-Wisconsinan axis of accumulation in the northern Appalachians farther to the east is supported by much published field evidence.

Gravity and magnetic anomalies of the Sutton Mountains region, Quebec and Vermont: expressions of rift volcanics related to the opening of Iapetus

Prominent, nearly coincident, positive gravity and magnetic anomalies occur in the Sutton Mountains region, centered about 100 km east of Montreal, Quebec. Several lines of evidence indicate that the gravity anomaly stems from two principal sources: a deep (mid and lower crustal) source of speculative origin and a shallow source identifiable with a narrow belt of late Precambrian – early Cambrian metavolcanic rocks, the Tibbit Hill volcanics. The magnetic anomaly seems to be produced mainly by the metavolcanic rocks. Three-dimensional modelling of a residual gravity anomaly, supplemented by two-dimensional modelling of the magnetic anomaly, shows that the seemingly minor belt of metavolcanic rocks constitutes the surface expression of a thick (maximum thickness ~8 km) pile of dominantly mafic volcanics, which are only slightly exposed at the present level of erosion.The Tibbit Hill volcanics are regarded as products of rift-related volcanism that occurred at an rrr triple junction developed during the early stages of the opening of the Iapetus Ocean. The Ottawa graben is probably the failed arm of this triple junction. The emplacement of the Grenville dike swarm whose trend is nearly coincident with that of the Ottawa graben was probably coeval with the volcanism in the Sutton Mountains region. The present work shows that the volcanism in the region was on a much larger scale than hitherto recognized.

Appalachian salients and recesses: Late Precambrian continental breakup and the opening of the Iapetus Ocean

Appalachian salients (convex toward the craton) and recesses (concave toward the craton) are inherited from the initial breakup of a continental mass by the intersection of rift valleys radiating from triple junctions, beginning about 820 m.y. ago. The trace of axes of anticlinoria exposing crystalline rocks older than 1 b.y., here called the Blue-Green-Long axis after major Precambrian massifs, roughly coincides with the western margin of a series of late Precambrian water-filled graben. The rift system east of the axis probably did not open far enough to produce significant oceanic crust but, like the Triassic basins of a later opening cycle, was an initial stage in the opening of an ocean basin ultimately located still farther east. Although metamorphosed basalt is widely distributed along the Blue-Green-Long axis, known upper Precambrian or Eocambrian metamorphosed rhyolite is restricted to three salients: Mt. Rogers, Virginia; South Mountain, Pennsylvania; and the Sutton Mountains, Quebec, Canada. These rhyolites are per-alkaline in affinity, are constituents of basalt-rhyolite suites, and are associated near Mt. Rogers and South Mountain with consanguineous aegirine granite. Suggestions of failed-arm troughs or aulacogens are found at all three salients. The basal Cambrian clastic sequence is thickest near the Mt. Rogers and South Mountain salients. Basal conglomerates are coarsest near Mt. Rogers. Geophysical anomalies suggest an area of buried mafic igneous rocks projecting northwest from the South Mountain salient. The Ottawa-Bonnechere graben, the most convincing of the failed-arm troughs, strikes into the Sutton Mountains salient. The Cambrian carbonate bank in northwestern Vermont faces north into this graben, which also contains alkaline ring complexes of probable Cambrian age at its western end at Lake Nipissing, Ontario. Recesses near Roanoke, Virginia, and New York City are triple junctions whose failed arms have been carried away. An anomalously thin basal Cambrian clastic sequence between western Massachusetts and eastern Pennsylvania may reflect a structurally high area that coincides with the concave side of the New York recess. The Wilson cycle implies that fracture zones may be reactivated as zones of weakness in subsequent events. The incipient opening of the present Atlantic (as evidenced by the trends of the Triassic basins between North Carolina and Massachusetts) was essentially parallel to and nearly coincident with the incipient opening of the Iapetus along the Blue-Green-Long axis. The trend of the Monteregian intrusions extends from the Ottawa-Bonnechere graben to the Sutton Mountains salient, suggesting reactivation of another zone of weakness.

On the glaciation of Orford and Sutton mountains, Que

On the glaciation of Orford and Sutton mountains, Que