Docking of the Central Metasedimentary Belt to Laurentia in geon 12: evidence from the 1.17-1.16 Ga Chevreuil intrusive suite and host gneisses, Quebec

2000 ◽  
Vol 37 (2-3) ◽  
pp. 253-269 ◽  
Author(s):  
Louise Corriveau ◽  
Otto van Breemen
Keyword(s):  
High Pressure ◽  
North America ◽  
Metamorphic Event ◽  
Grenville Province ◽  
Layered Gabbro ◽  
Peak Metamorphism ◽  
Magma Emplacement ◽  
Reactivation Event ◽  
Intrusive Suite ◽  
Tectonic Boundaries

The Chevreuil intrusive suite (1.17-1.16 Ga) represents a chronological field marker of regional extent that intruded the Central Metasedimentary Belt in the western Grenville Province of Quebec after peak metamorphism. Style and site of magma emplacement, and extent of deformation of Chevreuil plutons and dykes permit unravelling of the early Grenvillian evolution of the belt with respect to cratonal North America. The suite comprises a series of vertically layered gabbro stocks and monzonite-diorite-gabbro sheet intrusions, and a swarm of microdiorite dykes that cut across gneisses. The dykes display systematic variations in extent of deformation across the belt. We targeted U-Pb geochronology on gneisses within the identified strain windows; they preserve the record of a ca. 1.20 Ga high pressure-temperature (P-T) metamorphic event. The sheet intrusions define magmatic corridors all along, and concordant with, the western, northern, and eastern tectonic boundaries of the belt. The concordant and elongate shape of these bodies results from emplacement, not deformation. Chevreuil magmas thus sealed the belt boundaries largely in their current positions, with the implication that docking of Elzevirian and pre-Elzevirian terranes with cratonal North America predates 1.17 Ga. We interpret the 1.20 Ga metamorphism as evidence for the initiation of Grenvillian continent-continent collision during the culmination of the Elzevirian orogeny at ca. 1.22 Ga. Emplacement-related fabrics indicate that the Chevreuil suite and the coeval Morin anorthosite suite intruded during renewed orogenesis. This orogenic pulse (Shawinigan) is not accretionary, but represents a strongly partitioned, compressive, intraplate reactivation event.

Eclogitized gabbros from the eastern Grenville Province: textures, metamorphic context, and implications

1993 ◽  
Vol 30 (1) ◽  
pp. 159-173 ◽  
Author(s):  
Aphrodite Indares
Keyword(s):  
High Pressure ◽  
High Pressures ◽  
Grenville Province ◽  
Mafic Rocks ◽  
Deep Burial ◽  
Mineral Assemblages ◽  
First Occurrence ◽  
Intrusive Suite ◽  
Very High

Undeformed lenses of olivine–orthopyroxene–gabbro belonging to the 1429 Ma Shabogamo Intrusive Suite (Parautochthonous Belt of the eastern Grenville Province) host the first occurrence of eclogite mineral assemblages reported from the Grenville Province. These rocks preserve igneous textures overprinted by eclogite mineralogy and by textures related to subsequent unloading. High-pressure signatures include omphacite pseudomorphs after augite, plagioclase replacement by garnet + kyanite + corundum, and orthopyroxene–omphacite–garnet coronas between olivine and plagioclase. Transformations related to decompression include replacement of garnet + kyanite + corundum by spinel + plagioclase, growth of plagioclase collars between clinopyroxene and garnet, and de-jadeitization of omphacite. Clinopyroxenes with numerous plagioclase inclusions and garnets surrounded by clinopyroxene–plagioclase symplectites in granoblastic mafic rocks from the same area are also evidence of decompression from high pressures. These rocks record pressure–temperature (P–T) conditions of 1600 MPa at 700–800 °C and steep subsequent P–T paths. It is suggested that the entire parautochthon in this part of the Grenville Province experienced deep burial during the Grenvillian metamorphism. In contrast, the Grenvillian metamorphic signature in the overlying allochthonous sheet is known to be minor, thus precluding any relationship between its emplacement and very high Grenvillian pressures in the parautochthon.

Partial melting of metapelites in the Gagnon terrane below the high-pressure belt in the Manicouagan area (Grenville Province): pressure–temperature (P–T) and U–Pb age constraints and implications

2006 ◽  
Vol 43 (9) ◽  
pp. 1309-1329 ◽  
Author(s):  
Sherri L Jordan ◽  
Aphrodite Indares ◽  
Greg Dunning
Keyword(s):  
High Pressure ◽  
Partial Melting ◽  
Metamorphic Event ◽  
Dehydration Melting ◽  
Melting Reaction ◽  
Grenville Province ◽  
Thermal Event ◽  
Zircon Crystallization ◽  
Age Constraints ◽  
Comparable Intensity

Metapelites of the parautochthonous Gagnon terrane at the footwall of the high-pressure (high-P) belt in the Manicouagan area (central Grenville Province) preserve an impressive textural record of partial melting reactions, mainly in polymineralic inclusions within garnet. The dominant textures were developed within the pressure–temperature (P–T) field of the continuous dehydration melting reaction biotite + kyanite (or sillimanite) + plagioclase + quartz = garnet + K-feldspar + melt, with sillimanite instead of kyanite in the southern part of the footwall. Inferred P–T paths have a hair-pin form in the range of 750–850 °C and 1000–1500 MPa for the kyanite-bearing rocks. Monazite crystallization ages are consistently late Grenvillian, either 995 or 985 Ma, and one sample contains monazite of both ages. Two of these samples also contain inherited monazite with ages of 1738 ± 5 and 1719 ± 30 Ma, indicative of an earlier metamorphic event. Tonalite and diorite from the same area yield Archean zircon crystallization ages and titanite ages of 961 ± 3 and 956 ± 4 Ma, the youngest in the Manicouagan region. The late Grenvillian metamorphism was of comparable intensity but ~50 Ma younger than in the overlying high-P belt in this area and therefore seems to be unrelated to the emplacement of the latter over the Parautochthonous Belt, as previously suggested. Rather, this younger metamorphism suggests a reactivation of the footwall by underthrusting of the Gagnon terrane during the waning stages of convergence, and a link with a major coeval post-tectonic thermal event farther south in the hinterland.

Petrogenesis of the peralkaline Flowers River Igneous Suite and its significance to the development of the southern Nain Batholith

2021 ◽  
pp. 1-26
Author(s):  
Taylor A. Ducharme ◽  
Christopher R.M. McFarlane ◽  
Deanne van Rooyen ◽  
David Corrigan
Keyword(s):  
Trace Element ◽  
Volcanic Rocks ◽  
Second Phase ◽  
Discrete Events ◽  
Volcanic Event ◽  
Volcanic Succession ◽  
Intrusive Suite ◽  
Tectonic Boundaries ◽  
Host Rocks ◽  
Nain Plutonic Suite

Abstract The Flowers River Igneous Suite of north-central Labrador comprises several discrete peralkaline granite ring intrusions and their coeval volcanic succession. The Flowers River Granite was emplaced into Mesoproterozoic-age anorthosite–mangerite–charnockite–granite (AMCG) -affinity rocks at the southernmost extent of the Nain Plutonic Suite coastal lineament batholith. New U–Pb zircon geochronology is presented to clarify the timing and relationships among the igneous associations exposed in the region. Fayalite-bearing AMCG granitoids in the region record ages of 1290 ± 3 Ma, whereas the Flowers River Granite yields an age of 1281 ± 3 Ma. Volcanism occurred in three discrete events, two of which coincided with emplacement of the AMCG and Flowers River suites, respectively. Shared geochemical affinities suggest that each generation of volcanic rocks was derived from its coeval intrusive suite. The third volcanic event occurred at 1271 ± 3 Ma, and its products bear a broad geochemical resemblance to the second phase of volcanism. The surrounding AMCG-affinity ferrodiorites and fayalite-bearing granitoids display moderately enriched major- and trace-element signatures relative to equivalent lithologies found elsewhere in the Nain Plutonic Suite. Trace-element compositions also support a relationship between the Flowers River Granite and its AMCG-affinity host rocks, most likely via delayed partial melting of residual parental material in the lower crust. Enrichment manifested only in the southernmost part of the Nain Plutonic Suite as a result of its relative proximity to multiple Palaeoproterozoic tectonic boundaries. Repeated exposure to subduction-derived metasomatic fluids created a persistent region of enrichment in the underlying lithospheric mantle that was tapped during later melt generation, producing multiple successive moderately to strongly enriched magmatic episodes.

Possible seismic reflector in the lower crust: Evidence from fabrics and experiments of seismic velocity on layered gabbro at high temperature and high pressure

2003 ◽  
Vol 48 (9) ◽  
pp. 914-920
Author(s):  
Xingong Ou ◽  
Zhenmin Jin ◽  
Shuyan Jin ◽  
H. Kern
Keyword(s):  
High Pressure ◽  
High Temperature ◽  
Lower Crust ◽  
Seismic Velocity ◽  
Layered Gabbro ◽  
Seismic Reflector

Revised stratigraphic nomenclature for Aphebian and other rock units, southern Labrador Trough, Grenville Province

1980 ◽  
Vol 17 (5) ◽  
pp. 668-670 ◽  
Author(s):  
T. Rivers
Keyword(s):  
Metamorphic Complex ◽  
Grenville Province ◽  
Intrusive Suite ◽  
Stratigraphic Nomenclature

Stratigraphically equivalent Aphebian strata occurring in both the Churchill and Grenville Provinces have different group and formational names. The stratigraphy was first defined within the Churchill Province, and it is proposed that use of these names be extended to cover equivalent units within the Grenville Province. The nomenclature of the Knob Lake Group will thus replace that of the Gagnon Group. Two other changes in terminology are proposed in accordance with a recent amendment to the Code of Stratigraphic Nomenclature. Shabogamo Gabbro is renamed Shabogamo Intrusive Suite, and the name Ashuanipi Metamorphic Complex is proposed instead of Ashuanipi Complex.

Geochronological evidence of Indosinian (high-pressure) metamorphic event and its tectonic significance in Taxkorgan area of the Western Kunlun Mountains, NW China

2010 ◽  
Vol 53 (10) ◽  
pp. 1445-1459 ◽  
Author(s):  
WenQiang Yang ◽  
Liang Liu ◽  
YuTing Cao ◽  
Chao Wang ◽  
ShiPing He ◽  
...  
Keyword(s):  
High Pressure ◽  
Metamorphic Event ◽  
Nw China ◽  
Kunlun Mountains ◽  
Western Kunlun ◽  
Tectonic Significance ◽  
Geochronological Evidence

Eclogitic amphibolites from the Grampian Moines

1986 ◽  
Vol 50 (356) ◽  
pp. 217-221 ◽  
Author(s):  
A. J. Baker
Keyword(s):  
High Pressure ◽  
Amphibolite Facies ◽  
Metamorphic Event ◽  
Partial Reaction

AbstractAmphibolites from the Grampian Moines of Scotland contain clinopyroxene-plagioclase symplectites and plagioclase-hornblende coronas around garnet. The clinopyroxene-plagioclase symplectites are interpreted as former omphacites. It is inferred that an eclogitic garne-tomphacite-quartz assemblage once existed, but has since undergone partial reaction to an amphibolite facies hornblende-plagioclase assemblage. An early high-pressure metamorphic event occurred in parts of the Moine.

Geology and geochronology of Helikian magmatism, western Labrador

1981 ◽  
Vol 18 (7) ◽  
pp. 1211-1227 ◽  
Author(s):  
Christopher Brooks ◽  
Richard J. Wardle ◽  
Toby Rivers
Keyword(s):  
Volcanic Rocks ◽  
High Grade ◽  
Regional Mapping ◽  
Grenville Province ◽  
Felsic Volcanism ◽  
High Grade Metamorphism ◽  
Narrow Belt ◽  
Intrusive Suite ◽  
Magmatic History ◽  
Magma Series

The Shabogamo intrusive suite, a predominantly gabbroic magma series intrusive into a variety of Archean, Aphebian, and Helikian units in the Churchill and Grenville Provinces of western Labrador, is reliably dated at circa 1375 Ma using both the Rb/Sr and Sm/Nd methods on whole rocks and mineral separates. The suite is thus synchronous with Elsonian magmatism in Labrador, which is characterized by the intrusion of large volumes of gabbroic, anorthositic, and associated magma, and so invites petrogenetic correlations on a regional scale.Gabbros of the Shabogamo intrusive suite are emplaced into volcanics and volcaniclastics of the Blueberry Lake group, which are provisionally dated at 1540 ± 40 Ma. The volcanic rocks are therefore of similar age to, and probably correlative with, the upper Petscapiskau Group and Bruce River Group felsic volcanics, which occur further east in a narrow belt within the Grenville Foreland zone. The linear disposition of centres of felsic volcanism in the Grenville Foreland zone about 1500 Ma ago is suggestive of the development of a major ensialic rift at least 300 km in length at that time. A twofold magmatic history during the Helikian of this part of Labrador is now emerging from the field mapping and geochronological studies. Early extrusive felsic volcanism about 1500 Ma ago confined to a linear belt immediately north of the Grenville Province was followed by voluminous mafic magmatism (with emplacement of gabbroic, anorthositic, and associated rocks) occurring over a wide area both within and outside of the present location of the Grenville Province.Rb/Sr dating of Aphebian quartzofeldspathic schists from within the Grenville Province near Wabush – Labrador City shows that the high-grade metamorphism and development of a penetrative schistosity were Grenvillian features formed about 1000 Ma ago. This result effectively precludes the possibility of a Hudsonian metamorphic imprint, a feasible interpretation that was raised during regional mapping of the area.

Tectonic Boundaries of the Eastern Gulf Coast of North America

AAPG Bulletin ◽  
1993 ◽  
Vol 77 ◽  
Author(s):  
LEONARD, CLIFFORD, JR., and ROBERT
Keyword(s):  
North America ◽  
Gulf Coast ◽  
Tectonic Boundaries

Lithoprobe line 55: integration of out-of-plane seismic results with surface structure, metamorphism, and geochronology, and the tectonic evolution of the eastern Grenville Province

2000 ◽  
Vol 37 (2-3) ◽  
pp. 341-358 ◽  
Author(s):  
Andrew Hynes ◽  
Aphrodite Indares ◽  
Toby Rivers ◽  
André Gobeil
Keyword(s):  
High Pressure ◽  
Three Dimensional ◽  
Good Control ◽  
Crustal Thickening ◽  
Metamorphic Rocks ◽  
Seismic Line ◽  
Grenville Province ◽  
Tectonic Model ◽  
Tectonic History ◽  
Out Of Plane

Lithoprobe line 55, in the Grenville Province of eastern Quebec, provides unusually good control on the three-dimensional (3-D) geometry and structural relationships among the major lithological units there. Archean basement underlies the exposed Proterozoic rocks, along the entire seismic line, and there is a lateral ramp in this basement immediately behind a lobate stack of thrust slices of high-pressure metamorphic rocks comprising the Manicouagan Imbricate Zone (MIZ). Integration of the 3-D geometry with P-T and geochronological data allows derivation of a tectonic model for the region. The MIZ was buried to depths >60 km at 1050 Ma. Preservation of its high-pressure assemblages, and the absence of metamorphism at 990 Ma, which is characteristic of lower pressure metamorphic rocks that tectonically overlie them, indicates the MIZ rocks were rapidly unroofed, early in the tectonic history. There were two discrete pulses of crustal thickening during the Grenvillian Orogeny in this region. The first, involving imbrication of Labradorian and Pinwarian rocks that comprised part of southeast Laurentia, culminated in the Ottawan pulse at ca. 1050 Ma, and produced the high-pressure metamorphism of the MIZ. Its effects were rapidly reversed, with extrusion of the MIZ rocks to shallow crustal levels at ca. 1020 Ma. The crust was again thickened, with the Moho subsiding to depths >60 km, in the Rigolet pulse at ca. 990 Ma. The site of extrusion of the MIZ was probably controlled by the subsurface lateral ramp. High geothermal gradients indicate that extrusion may have been aided by lithospheric delamination in the crustal-thickening zone.

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