U–Pb geochronology of the Mazinaw terrane, an imbricate segment of the Central Metasedimentary Belt, Grenville Province, Ontario

Corfú, Fernando; Easton, R. M.

doi:10.1139/e95-081

Cited by 53 publications

(35 citation statements)

References 33 publications

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“…The entire MB and the GT were affected by metamorphism and deformation at ca. 1160 Ma (McLelland et al 1988;van Breemen and Davidson 1990;Mezger et al 1991bMezger et al , 1993Chiarenzelli and McLelland 1993;Corfu andEaston 1995, 1997).…”

Section: Introductionmentioning

confidence: 99%

Early History of the Carthage‐Colton Shear Zone, Grenville Province, Northwest Adirondacks, New York (U.S.A.)

Streepey

Johnson

Mezger

et al. 2001

The Journal of Geology

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A B S T R A C TThe Adirondack Mountains expose two distinct tectonic elements of the Proterozoic Grenville Province of northeastern North America: the Adirondack Lowlands and Highlands. The Lowlands are located along the eastern edge of the Metasedimentary Belt, and the Highlands form the western portion of the Granulite Terrane. The two are separated by the Carthage-Colton Shear Zone (CCSZ). U/Pb titanite and 40 Ar hornblende ages in the Lowlands are ca. 100 m.yr. older than in the Highlands, across the CCSZ. While both the Lowlands and the Highlands record a history of metamorphism during the Elzevirian Orogeny (ca. 1150 Ma), only the Highlands record evidence of a major phase of Grenvillian thermotectonic activity (Ottawan Orogeny) at ca. 1090-1030 Ma. Proposed tectonic models require that the Lowlands were either laterally separated from the Highlands or were at structurally higher levels during this metamorphism. New U/Pb and Ar hornblende ages at 1000 Ma within the shear zone. Thermobarometric constraints indicate that deformation occurred under granulite-facies conditions. Therefore, titanite and hornblende ages are interpreted as cooling ages from a ca. 1050-1030-Ma event. An early transpressive shearing event at ca. 1040 Ma, combined with structural data in the Dana Hill metagabbro that indicate strike-slip displacement along the CCSZ, suggests significant lateral displacement between the Lowlands and the Highlands during the ca. 1090-1030-Ma Ottawan Orogeny, prior to later extension along the CCSZ.

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Section: Introductionmentioning

confidence: 99%

Early History of the Carthage‐Colton Shear Zone, Grenville Province, Northwest Adirondacks, New York (U.S.A.)

Streepey

Johnson

Mezger

et al. 2001

The Journal of Geology

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“…2) that seems to have been created during the Ottawan orogenic pulse (Corfu and Easton, 1995). Uplift and partial erosion of the block have exposed a variety of heterogeneously strained rock units, whose 1020 Ma metamorphism reaches amphibolite facies and is generally at a higher grade than that of similar units observed in the adjacent Grimsthorpe and Sharbot Lake domains ( Fig.…”

Section: Geology Of the Composite Arc Belt And The Mazinaw Domainmentioning

confidence: 99%

“…1; Easton, 1992). Moreover, rocks presently exposed in these adjacent domains were un- affected by the 1020 Ma metamorphism in the Ottawan orogenic pulse (Corfu and Easton, 1995).…”

Section: Geology Of the Composite Arc Belt And The Mazinaw Domainmentioning

confidence: 99%

L-S shape fabrics in the Mazinaw domain and the issue of northwest-directed thrusting in the Composite Arc Belt, southeastern Ontario

Schwerdtner¹,

Downey²,

Alexander³

2004

Memoir 197: Proterozoic Tectonic Evolution of the Grenville Orogen in North America

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Many vertical sections across deeper parts of collisional orogens contain gently dipping thrusts that have the geometric style of shallow-crustal, dip-slip faults. In the southwestern Grenville Province (central and southeastern Ontario), however, structural geologists have found it difficult to document northwest-directed thrusting within large, polydeformed complexes of medium-to high-grade metamorphic rocks. This applies, in particular, to the Mazinaw domain of the eastern Composite Arc Belt, where narrow north-to east-northeast-striking ("longitudinal") zones of high strain have been linked tentatively to ductile thrusting at the sole of Elzevirian (1230-1190 Ma) or Early Ottawan (1085-1015 Ma) fold nappes. During subsequent northwestsoutheast shortening, the apparent thrusts behaved as structural detachment horizons or were subhorizontally folded, together with their wallrocks.Gravity modeling and reflection-seismic profiling have shown that in the present shallow crust most tabular rock bodies and coplanar structural surfaces (including high-strain zones and ductile faults) are horizontal or dip < <45°SE. This seems incompatible with the idea that Elzevirian and Early Ottawan thrusts acquired strong curvature in the northwest-southeast vertical plane during upright buckling of fold nappes and other southeast-dipping lithotectonic units.The longitudinal high-strain zones and their ductilely deformed wallrocks are characterized by steeply inclined to vertical planar fabrics (S) such as geometric systems of strained mineral constituents, pebbles, and volcanic fragments. Linear fabrics (L) coexist with the planar fabrics at many localities, but are commonly weak or seemingly absent. The prevalence of planar fabrics is difficult to explain by shallow-crustalstyle ductile thrusting, but these fabrics may have been produced by large-scale strains associated with the formation of midcrustal stretching thrusts.For a variety of thrust-dip options, we use L < < S fabrics to derive the local sense of tangential shear strain within and adjacent to six high-strain zones. The sense of accumulated shear strain proves to be reverse for most realistic options, even if one presumes that the zones rotated during superimposed buckle folding. Mesoscopic Zfolds are common in one high-strain zone, and attest to dextral-reverse shearing and shortening of thrust walls during Mid-to Late Ottawan deformation (1015-980 Ma). *

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“…2. 2 (Pehrson et al 1996: Corfu et Easton 1995: Hildebrand et Easton 1995. Notons que tous les âges cités ci-dessus ne représentent ni des âges minimum ni maximum de la faille, mais, ils représentent des âges précis de l'activité de la faille.…”

Section: Le Parautochtoneunclassified

Géochronologie, géochimie et pétrographie des roches métamorphiques et ignées autour du gisement de wollastonite du Canton Saint-Onge, Québec, Canada /

Ider¹

1997

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UIUQAC Mise en garde/AdviceAfin de rendre accessible au plus grand nombre le résultat des travaux de recherche menés par ses étudiants gradués et dans l'esprit des règles qui régissent le dépôt et la diffusion des mémoires et thèses produits dans cette Institution, l'Université du Québec à Chicoutimi (UQAC) est fière de rendre accessible une version complète et gratuite de cette oeuvre.Motivated by a desire to make the results of its graduate students' research accessible to all, and in accordance with the rules governing the acceptation and diffusion of dissertations and theses in this Institution, the Université du Québec à Chicoutimi (UQAC) is proud to make a complete version of this work available at no cost to the reader.L'auteur conserve néanmoins la propriété du droit d'auteur qui protège ce mémoire ou cette thèse. Ni le mémoire ou la thèse ni des extraits substantiels de ceux-ci ne peuvent être imprimés ou autrement reproduits sans son autorisation.The author retains ownership of the copyright of this dissertation or thesis. Neither the dissertation or thesis, nor substantial extracts from it, may be printed or otherwise reproduced without the author's permission. RésuméLe gisement de wollastonite du Canton Saint-Onge est un important dépôt de wollastonite récemment découvert dans le complexe anorthositique du lac Saint-Jean (CALSJ). Ce gisement est interprété comme un skarn, mais les plutons possibles pour sa formation restent encore inconnus. Le gisement s'est développé dans les paragneiss situés dans le couloir de la zone de cisaillement du Lac Saint-Jean-Pipmuacan (ZCLSJP) qui coupe le CALSJ. Cette zone contient plusieurs plutons déformés ou non qui peuvent être associés au CALSJ (et sa fameuse suite AMCG). Les zircons trouvés dans les poches pegmatitiques dans les anorthosites indiquent un âge de cristallisation de 1137 ± 3 Ma, mais toutes les fractions de zircons sont discordantes. Si on suppose qu'une perte de plomb s'est produite à cause de la mise en place des plutons tardifs, alors l'âge des roches serait de 1159 ± 3 Ma, cet âge est semblable à celui des anorthosites de la partie sud ( 1157 Ma, 1142 Ma).Le Granite de Du Bras possède une forme lenticulaire, il est parallèle à la ZCLSJP, il est toujours en contact avec les anorthosites et il est considéré comme un granophyre qui est généré par la fusion des roches paragneissiques hôtes suite à la mise en place des anorthosites. L'âge U/Pb des zircons du Granite de Du Bras de 1148 ± 5 Ma est cohérent avec cette idée. La phase grossière de ce granite montre une forte foliation parallèle à la ZCLSJP tandis que sa phase fine est légèrement déformée. Ceci suggère que l'âge de ce pluton serait aussi l'âge d'une phase du mouvement de la ZCLSJP. Les paragneiss qui contiennent la wollastonite ne possèdent pas de zircon, mais la titanite donne un âge de i 160 ± 20 Ma, cet âge est identique à celui du Granite de Du Bras, ceci indique que ce pluton pourrait être la source des fluides siliceux qui sont responsables de la genèse du gisement de wollastonite. L'...

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U–Pb geochronology of the Mazinaw terrane, an imbricate segment of the Central Metasedimentary Belt, Grenville Province, Ontario

Cited by 53 publications

References 33 publications

Early History of the Carthage‐Colton Shear Zone, Grenville Province, Northwest Adirondacks, New York (U.S.A.)

Early History of the Carthage‐Colton Shear Zone, Grenville Province, Northwest Adirondacks, New York (U.S.A.)

L-S shape fabrics in the Mazinaw domain and the issue of northwest-directed thrusting in the Composite Arc Belt, southeastern Ontario

Géochronologie, géochimie et pétrographie des roches métamorphiques et ignées autour du gisement de wollastonite du Canton Saint-Onge, Québec, Canada /

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